global climate change case study

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Climate Change Collection

HKS climate change cases span the globe and cover a variety of disciplines from economics to leadership, and from energy policy to international trade. For your convenience, this resource has been categorized in two ways: by topic and by region .

Climate Change Cases by Topic

Climate Change Cases by Region

Negotiating toward the Paris Accords: WWF and the Role of Forests in the 2015 Climate Agreement  by Pamela Varley and Robert Wilkinson

Shaping the Future of Solar Power: Climate Change, Industrial Policy and Free Trade by Anjani Datla and Robert Lawrence

Shaping the Future of Solar Power: Climate Change, Industrial Policy and Free Trade (B)  by Anjani Datla and Robert Lawrence

Solar Panels and Safeguards: Rising Tensions in the Global Trading System by Anjani Datla and Robert Lawrence

Buchanan Renewables: Bringing Power to Liberia  by Tamara Heimur, Henry Lee, and Akash Deep Evaluating the Impact of Solar Lamps in Uganda  by Anjani Datla, Dan Levy, and Patricia Garcia-Rios

Fighting Pollution with Data: Environmental Audits and the Gujarat Pollution Control Board and sequel   by Anjani Datla and Rohini Pande

Central America

Costa Rica's Forests and the Market for Carbon Emissions Reduction Credits by Rene Castro Salazar and Jose Gomez-Ibanez

Rural Electrification in Nicaragua (Abridged)  by Tahir Sheikh and Jose Gomez-Ibanez

South America

Integrating Renewable Energy in Argentina  by Anjani Datla and Henry Lee

Untapped Potential: Renewable Energy in Argentina  and  sequel  by Anjani Datla and Henry Lee

U.S., Canada, and Europe

A Cascade of Emergencies: Responding to Superstorm Sandy in New York City (A)  by David W. Giles and Arnold M. Howitt 

A Cascade of Emergencies: Responding to Superstorm Sandy in New York City (B)  by David W. Giles and Arnold M. Howitt  Ambitious but Achievable: Using Land Use and Transportation Plans to Reduce GHG Emissions in California  and  sequel  by David Luberoff, Carl Allen, and Jose Gomez-Ibanez Caño Martín Peña: Land Ownership and Politics Collide in Puerto Rico  by Patricia Garcia-Rios and Quinton Mayne Choosing the Road Less Traveled: How Cycling Took Hold in Copenhagen by Pamela Varley and Quinton Mayne

Climate Resilience in New York City: The Battle over East River Park  by Patricia Garcia-Rios and Justin de Benedictis-Kessner Corporate Average Fuel Economy Standards 2017-2025  by Anjani Datla and Albert Nichols Electric Vehicles in Cities  by Yennga Khuong and Jose Gomez-Ibanez Gainesville Regional Utilities' Feed-in Tariff  and  epilogue  by Leah Stokes and Henry Lee

Greenland and the Paris Agreement  by Katie Segal, Elsenguaq Silassen, and Halla Hrund Logadóttir Iceland's Energy Policy: Finding the Right Path Forward  by Halla Hrund Logadóttir and Henry Lee Implementing the Inflation Reduction Act: Can the Tax Code Transform American Energy?  by Laura Winig and John D. Donahue Innovation at GSA: Zero Environmental Footprint and the Extreme Challenge (A)  by James Quinn, Patricia Garcia-Rios, and Steven Kelman Miami-Dade County and Sea Rise  and  sequel  by Henry Lee, Natalie Unterstell, Shauna Theel, and Pinar De Neve Mothers Out Front by Laura Winig and Marshall Ganz Pricing Carbon: The Birth of British Columbia's Carbon Tax  and  sequel  by Anjani Datla and Henry Lee Oregon's Wind Energy Health Impact Assessment  by David Tannenwald and Arnold M. Howitt Power Partnership: The Creation of a Hybrid Electric Delivery Truck Eaton, Fedex, and Environmental Defense  by Barbara J. Mack and Alan Trager The California Global Warming Solutions Act (AB32)  by Jose Gomez-Ibanez The Challenge of Adapting to Climate Change: King County Brings Local Action to a Global Threat  and  sequel  by Pamela Varley and John D. Donahue This Far and No Further: The Rise and Fall of the Committee on Earth and Environmental Sciences  by David Kennedy and Bill Clark

Economics of Climate Change

Corporate Average Fuel Economy Standards 2017-2025  by Anjani Datla and Albert Nichols Pricing Carbon: The Birth of British Columbia's Carbon Tax  and  sequel  by Anjani Datla and Henry Lee Shaping the Future of Solar Power: Climate Change, Industrial Policy and Free Trade  by Anjani Datla and Robert Lawrence

Shaping the Future of Solar Power: Climate Change, Industrial Policy and Free Trade (B)  by Anjani Datla and Robert Lawrence Solar Panels and Safeguards: Rising Tensions in the Global Trading System  by Anjani Datla and Robert Lawrence Untapped Potential: Renewable Energy in Argentina  and  sequel  by Anjani Datla and Henry Lee 

Return to Topics

Government and Regulation Buchanan Renewables: Bringing Power to Liberia  by Tamara Heimur, Henry Lee, and Akash Deep Choosing the Road Less Traveled: How Cycling Took Hold in Copenhagen  by Pamela Varley and Quinton Mayne Corporate Average Fuel Economy Standards 2017-2025  by Anjani Datla and Albert Nichols Gainesville Regional Utilities' Feed-in Tariff  and  epilogue  by Leah Stokes and Henry Lee Miami-Dade County and Sea Rise  and  sequel  by Henry Lee, Natalie Unterstell, Shauna Theel, and Pinar De Neve Pricing Carbon: The Birth of British Columbia's Carbon Tax  and  sequel  by Anjani Datla and Henry Lee The California Global Warming Solutions Act (AB32)  by Jose Gomez-Ibanez The Challenge of Adapting to Climate Change: King County Brings Local Action to a Global Threat  and  sequel  by Pamela Varley and John D. Donahue

Evidence and Decision-Making Evaluating the Impact of Solar Lamps in Uganda  by Anjani Datla, Dan Levy, and Patricia Garcia-Rios Fighting Pollution with Data: Environmental Audits and the Gujarat Pollution Control Board  and  sequel  by Anjani Datla and Rohini Pande Mothers Out Front  by Laura Winig and Marshall Ganz

Leadership and Negotiation Innovation at GSA: Zero Environmental Footprint and the Extreme Challenge (A)  by James Quinn, Patricia Garcia-Rios, and Steven Kelman Mothers Out Front  by Laura Winig and Marshall Ganz Negotiating toward the Paris Accords: WWF & the Role of Forests in the 2015 Climate Agreement  by Pamela Varley and Robert Wilkinson Pricing Carbon: The Birth of British Columbia's Carbon Tax  and  sequel  by Anjani Datla and Henry Lee The Challenge of Adapting to Climate Change: King County Brings Local Action to a Global Threat  and  sequel  by Pamela Varley and John D. Donahue This Far and No Further: The Rise and Fall of the Committee on Earth and Environmental Sciences  by David Kennedy and Bill Clark

Energy Policy and Renewables

Ambitious but Achievable: Using Land Use and Transportation Plans to Reduce GHG Emissions in California  and  sequel  by David Luberoff, Carl Allen, and Jose Gomez-Ibanez Buchanan Renewables: Bringing Power to Liberia  by Tamara Heimur, Henry Lee, and Akash Deep Caño Martín Peña: Land Ownership and Politics Collide in Puerto Rico  by Patricia Garcia-Rios and Quinton Mayne Costa Rica's Forests and the Market for Carbon Emissions Reduction Credits  by Rene Castro Salazar and Jose Gomez-Ibanez Electric Vehicles in Cities  by Yennga Khuong and Jose Gomez-Ibanez Greenland and the Paris Agreement  by Katie Segal, Elsenguaq Silassen, and Halla Hrund Logadóttir

Iceland's Energy Policy: Finding the Right Path Forward  by Halla Hrund Logadóttir and Henry Lee Implementing the Inflation Reduction Act: Can the Tax Code Transform American Energy?  by Laura Winig and John D. Donahue Integrating Renewable Energy in Argentina  by Anjani Datla and Henry Lee Oregon's Wind Energy Health Impact Assessment  by David Tannenwald and Arnold M. Howitt Power Partnership: The Creation of a Hybrid Electric Delivery Truck Eaton, Fedex, and Environmental Defense  by Barbara J. Mack and Alan Trager

Rural Electrification in Nicaragua (Abridged)  by Tahir Sheikh and Jose Gomez-Ibanez

Disaster Preparedness

A Cascade of Emergencies: Responding to Superstorm Sandy in New York City (B)  by David W. Giles and Arnold M. Howitt Climate Resilience in New York City: The Battle over East River Park  by Patricia Garcia-Rios and Justin de Benedictis-Kessner  Miami-Dade County and Sea Rise  and  sequel  by Henry Lee, Natalie Unterstell, Shauna Theel, and Pinar De Neve

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10 Big Findings from the 2023 IPCC Report on Climate Change

• climate change
• Climate Resilience
• climate science
• climatewatch-pinned

March 20 marked the release of the final installment of the Intergovernmental Panel on Climate Change’s (IPCC) Sixth Assessment Report (AR6) , an eight-year long undertaking from the world’s most authoritative scientific body on climate change. Drawing on the findings of 234 scientists on the  physical science of climate change , 270 scientists on  impacts, adaptation and vulnerability to climate change , and 278 scientists on  climate change mitigation , this  IPCC synthesis report  provides the most comprehensive, best available scientific assessment of climate change.

It also makes for grim reading. Across nearly 8,000 pages, the AR6 details the devastating consequences of rising greenhouse gas (GHG) emissions around the world — the destruction of homes, the loss of livelihoods and the fragmentation of communities, for example — as well as the increasingly dangerous and irreversible risks should we fail to change course.

But the IPCC also offers hope, highlighting pathways to avoid these intensifying risks. It identifies readily available, and in some cases, highly cost-effective actions that can be undertaken now to reduce GHG emissions, scale up carbon removal and build resilience. While the window to address the climate crisis is rapidly closing, the IPCC affirms that we can still secure a safe, livable future.

Here are 10 key findings you need to know:

1. Human-induced global warming of 1.1 degrees C has spurred changes to the Earth’s climate that are unprecedented in recent human history.

Already, with 1.1 degrees C (2 degrees F) of global temperature rise, changes to the climate system that are unparalleled over centuries to millennia are now occurring in every region of the world, from rising sea levels to more extreme weather events to rapidly disappearing sea ice.

Additional warming will increase the magnitude of these changes. Every 0.5 degree C (0.9 degrees F) of global temperature rise, for example, will cause clearly discernible increases in the frequency and severity of heat extremes, heavy rainfall events and regional droughts. Similarly, heatwaves that, on average, arose once every 10 years in a climate with little human influence will likely occur 4.1 times more frequently with 1.5 degrees C (2.7 degrees F) of warming, 5.6 times with 2 degrees C (3.6 degrees F) and 9.4 times with 4 degrees C (7.2 degrees F) — and the intensity of these heatwaves will also increase by 1.9 degrees C (3.4 degrees F), 2.6 degrees C (4.7 degrees F) and 5.1 degrees C (9.2 degrees F) respectively.

Rising global temperatures also heighten the probability of reaching dangerous tipping points in the climate system that, once crossed, can trigger self-amplifying feedbacks that further increase global warming, such as thawing permafrost or massive forest dieback. Setting such reinforcing feedbacks in motion can also lead to other substantial, abrupt and irreversible changes to the climate system. Should warming reach between 2 degrees C (3.6 degrees F) and 3 degrees C (5.4 degrees F), for example, the West Antarctic and Greenland ice sheets could melt almost completely and irreversibly over many thousands of years, causing sea levels to rise by several meters.

2. Climate impacts on people and ecosystems are more widespread and severe than expected, and future risks will escalate rapidly with every fraction of a degree of warming.

Described as an “an atlas of human suffering and a damning indictment of failed climate leadership” by United Nations Secretary-General António Guterres, one of AR6’s most alarming conclusions is that adverse climate impacts are already more far-reaching and extreme than anticipated. About half of the global population currently contends with severe water scarcity for at least one month per year, while higher temperatures are enabling the spread of vector-borne diseases, such as malaria, West Nile virus and Lyme disease. Climate change has also slowed improvements in agricultural productivity in middle and low latitudes, with crop productivity growth shrinking by a third in Africa since 1961. And since 2008, extreme floods and storms have forced over 20 million people from their homes every year.

Every fraction of a degree of warming will intensify these threats, and even limiting global temperature rise to 1.5 degree C is not safe for all. At this level of warming, for example, 950 million people across the world’s drylands will experience water stress, heat stress and desertification, while the share of the global population exposed to flooding will rise by 24%.

Similarly, overshooting 1.5 degrees C (2.7 degrees F), even temporarily, will lead to much more severe, oftentimes irreversible impacts, from local species extinctions to the complete drowning of salt marshes to loss of human lives from increased heat stress. Limiting the magnitude and duration of overshooting 1.5 degrees C (2.7 degrees F), then, will prove critical in ensuring a safe, livable future, as will holding warming to as close to 1.5 degrees C (2.7 degrees F) or below as possible. Even if this temperature limit is exceeded by the end of the century, the imperative to rapidly curb GHG emissions to avoid higher levels of warming and associated impacts remains unchanged.

3. Adaptation measures can effectively build resilience, but more finance is needed to scale solutions.

Climate policies in at least 170 countries now consider adaptation, but in many nations, these efforts have yet to progress from planning to implementation. Measures to build resilience are still largely small-scale, reactive and incremental, with most focusing on immediate impacts or near-term risks. This disparity between today’s levels of adaptation and those required persists in large part due to limited finance. According to the IPCC, developing countries alone will need $127 billion per year by 2030 and $295 billion per year by 2050 to adapt to climate change. But funds for adaptation reached just $23 billion to $46 billion from 2017 to 2018, accounting for only 4% to 8% of tracked climate finance.

The good news is that the IPCC finds that, with sufficient support, proven and readily available adaptation solutions can build resilience to climate risks and, in many cases, simultaneously deliver broader sustainable development benefits.

Ecosystem-based adaptation, for example, can help communities adapt to impacts that are already devastating their lives and livelihoods, while also safeguarding biodiversity, improving health outcomes, bolstering food security, delivering economic benefits and enhancing carbon sequestration. Many ecosystem-based adaptation measures — including the protection, restoration and sustainable management of ecosystems, as well as more sustainable agricultural practices like integrating trees into farmlands and increasing crop diversity — can be implemented at relatively low costs today. Meaningful collaboration with Indigenous Peoples and local communities is critical to the success of this approach, as is ensuring that ecosystem-based adaptation strategies are designed to account for how future global temperature rise will impact ecosystems.

4. Some climate impacts are already so severe they cannot be adapted to, leading to losses and damages.

Around the world, highly vulnerable people and ecosystems are already struggling to adapt to climate change impacts. For some, these limits are “soft” — effective adaptation measures exist, but economic, political and social obstacles constrain implementation, such as lack of technical support or inadequate funding that does not reach the communities where it’s needed most. But in other regions, people and ecosystems already face or are fast approaching “hard” limits to adaptation, where climate impacts from 1.1 degrees C (2 degrees F) of global warming are becoming so frequent and severe that no existing adaptation strategies can fully avoid losses and damages. Coastal communities in the tropics, for example, have seen entire coral reef systems that once supported their livelihoods and food security experience widespread mortality, while rising sea levels have forced other low-lying neighborhoods to move to higher ground and abandon cultural sites. 

Whether grappling with soft or hard limits to adaptation, the result for vulnerable communities is oftentimes irreversible and devastating. Such losses and damages will only escalate as the world warms. Beyond 1.5 degrees C (2.7 degrees F) of global temperature rise, for example, regions reliant on snow and glacial melt will likely experience water shortages to which they cannot adapt. At 2 degrees C (3.6 degrees F), the risk of concurrent maize production failures across important growing regions will rise dramatically. And above 3 degrees C (5.4 degrees F), dangerously high summertime heat will threaten the health of communities in parts of southern Europe.

Urgent action is needed to avert, minimize and address these losses and damages. At COP27, countries took a critical step forward by agreeing to establish funding arrangements for loss and damage, including a dedicated fund. While this represents  a historic breakthrough  in the climate negotiations, countries must now figure out the details of what these funding arrangements, as well as the new fund , will look like in practice — and it’s these details that will ultimately determine the adequacy, accessibility, additionality and predictability of these financial flows to those experiencing loss and damage.

5. Global GHG emissions peak before 2025 in 1.5 degrees C-aligned pathways.

The IPCC finds that there is a more than 50% chance that global temperature rise will reach or surpass 1.5 degrees C (2.7 degrees F) between 2021 and 2040 across studied scenarios, and under a high-emissions pathway, specifically, the world may hit this threshold even sooner — between 2018 and 2037. Global temperature rise in such a carbon-intensive scenario could also increase to 3.3 degrees C to 5.7 degrees C (5.9 degrees F to 10.3 degrees F) by 2100. To put this projected amount of warming into perspective, the last time global temperatures exceeded 2.5 degrees C (4.5 degrees F) above pre-industrial levels was more than 3 million years ago.

Changing course to limit global warming to 1.5 degrees C (2.7 degrees F) — with no or limited overshoot — will instead require deep GHG emissions reductions in the near-term. In modelled pathways that limit global warming to this goal, GHG emissions peak immediately and before 2025 at the latest. They then drop rapidly, declining 43% by 2030 and 60% by 2035, relative to 2019 levels.

While there are some bright spots — the annual growth rate of GHG emissions slowed from an average of 2.1% per year between 2000 and 2009 to 1.3% per year between 2010 and 2019, for example — global progress in mitigating climate change remains woefully off track. GHG emissions have climbed steadily over the past decade, reaching 59 gigatonnes of carbon dioxide equivalent (GtCO2e) in 2019 — approximately 12% higher than in 2010 and 54% greater than in 1990.

Even if countries achieved their climate pledges (also known as nationally determined contributions or NDCs),  WRI research  finds that they would reduce GHG emissions by just 7% from 2019 levels by 2030, in contrast to the 43% associated with limiting temperature rise to 1.5 degrees C (2.7 degrees F). And while handful of countries have submitted  new or enhanced NDCs  since the IPCC’s cut-off date,  more recent analysis  that takes these submissions into account finds that these commitments collectively still fall short of closing this emissions gap.

6. The world must rapidly shift away from burning fossil fuels — the number one cause of the climate crisis.

In pathways limiting warming to 1.5 degrees C (2.7 degrees F) with no or limited overshoot just a net 510 GtCO2 can be emitted before carbon dioxide emissions reach net zero in the early 2050s. Yet future carbon dioxide emissions from existing and planned fossil fuel infrastructure alone could surpass that limit by 340 GtCO2, reaching 850 GtCO2.

A mix of strategies can help avoid  locking in  these emissions, including retiring existing fossil fuel infrastructure, canceling new projects, retrofitting fossil-fueled power plants with carbon capture and storage (CCS) technologies and scaling up renewable energy sources like solar and wind (which are now cheaper than fossil fuels in many regions).

In pathways that limit warming to 1.5 degrees C (2.7 degrees F) — with no or limited overshoot — for example, global use of coal falls by 95% by 2050, oil declines by about 60% and gas by about 45%. These figures assume significant use of abatement technologies like CCS, and without them, these same pathways show much steeper declines by mid-century. Global use of coal without CCS, for example, is virtually phased out by 2050.

Although coal-fired power plants are starting to be retired across Europe and the United States, some multilateral development banks continue to invest in new coal capacity. Failure to change course risks stranding assets worth trillions of dollars.

7. We also need urgent, systemwide transformations to secure a net-zero, climate-resilient future.

While fossil fuels are the number one source of GHG emissions, deep emission cuts are necessary across all of society to combat the climate crisis. Power generation, buildings, industry, and transport are responsible for close to 80% of global emissions while agriculture, forestry and other land uses account for the remainder.

Take the  transport system , for instance. Drastically cutting emissions will require urban planning that minimizes the need for travel, as well as the build-out of shared, public and nonmotorized transport, such as rapid transit and bicycling in cities. Such a transformation will also entail increasing the supply of electric passenger vehicles, commercial vehicles and buses, coupled with wide-scale installation of rapid-charging infrastructure, investments in zero-carbon fuels for shipping and aviation and more.

Policy measures that make these changes less disruptive can help accelerate needed transitions, such as subsidizing zero-carbon technologies and taxing high-emissions technologies like fossil-fueled cars. Infrastructure design — like reallocating street space for sidewalks or bike lanes — can help people transition to lower-emissions lifestyles. It is important to note there are many co-benefits that accompany these transformations, too. Minimizing the number of passenger vehicles on the road, in this example, reduces harmful local air pollution and cuts traffic-related crashes and deaths.

Systems Change Lab  monitors, learns from and mobilizes action to achieve the far-reaching transformational shifts needed to limit global warming to 1.5 degrees C, halt biodiversity loss and build a just and equitable economy.

Transformative adaptation measures, too, are critical for securing a more prosperous future. The IPCC emphasizes the importance of ensuring that adaptation measures drive systemic change, cut across sectors and are distributed equitably across at-risk regions. The good news is that there are oftentimes strong synergies between transformational mitigation and adaptation. For example, in the global food system, climate-smart agriculture practices like shifting to  agroforestry  can improve resilience to climate impacts, while simultaneously advancing mitigation.  

8. Carbon removal is now essential to limit global temperature rise to 1.5 degrees C.

Deep decarbonization across all systems while building resilience won’t be enough to achieve global climate goals, though. The IPCC finds that all pathways that limit warming to 1.5 degrees C (2.7 degrees F) — with no or limited overshoot — depend on some quantity of  carbon removal . These approaches encompass both natural solutions, such as sequestering and storing carbon in trees and soil, as well as more nascent technologies that pull carbon dioxide directly from the air.

Hover over each carbon removal approach to learn more:

Note: This figure includes carbon removal approaches mentioned in countries' long-term climate strategies as well as other leading proposed approaches. The natural/biotic vs. technological/abiotic categorization shown here is illustrative rather than definitive and will vary depending on how approaches are applied, particularly for carbon removal approaches in the ocean.

The amount of carbon removal required depends on how quickly we reduce GHG emissions across other systems and the extent to which climate targets are overshot, with estimates ranging from between 5 GtCO2 to 16 GtCO2 per year needed by mid-century.

All carbon removal approaches have merits and drawbacks. Reforestation, for instance, represents a readily available, relatively low-cost strategy that, when implemented appropriately, can deliver a wide range of benefits to communities. Yet the carbon stored within these ecosystems is also vulnerable to disturbances like wildfires, which may increase in frequency and severity with additional warming. And, while technologies like bioenergy with carbon capture and storage (BECCS) may offer a more permanent solution, such approaches also risk displacing croplands, and in doing so, threatening food security. Responsibly researching, developing and deploying emerging carbon removal technologies, alongside existing natural approaches, will therefore require careful understanding of each solution’s unique benefits, costs and risks.

9. Climate finance for both mitigation and adaptation must increase dramatically this decade.

The IPCC finds that public and private finance flows for fossil fuels today far surpass those directed toward climate mitigation and adaptation. Thus, while annual public and private climate finance has risen by upwards of 60% since the IPCC’s Fifth Assessment Report, much more is still required to achieve global climate change goals. For instance, climate finance will need to increase between 3 and 6 times by 2030 to achieve mitigation goals, alone.

This gap is widest in developing countries, particularly those already struggling with debt, poor credit ratings and economic burdens from the COVID-19 pandemic. Recent mitigation investments, for example, need to increase by at least sixfold in Southeast Asia and developing countries in the Pacific, fivefold in Africa and fourteenfold in the Middle East by 2030 to hold warming below 2 degrees C (3.6 degrees F). And across sectors, this shortfall is most pronounced for agriculture, forestry and other land use, where recent financial flows are 10 to 31 times below what is required to achieve the Paris Agreement’s goals.

Finance for adaptation, as well as loss and damage, will also need to rise dramatically. Developing countries, for example, will need $127 billion per year by 2030 and $295 billion per year by 2050. While AR6 does not assess countries’ needs for finance to avert, minimize and address losses and damages,  recent estimates  suggest that they will be substantial in the coming decades. Current funds for both fall well below estimated needs, with the highest estimates of adaptation finance totaling under $50 billion per year.

10. Climate change — as well as our collective efforts to adapt to and mitigate it — will exacerbate inequity should we fail to ensure a just transition.  

Households with incomes in the top 10%, including a relatively large share in developed countries, emit upwards of 45% of the world's GHGs, while those families earning in the bottom 50% account for 15% at most. Yet the effects of climate change already — and will continue to — hit poorer, historically marginalized communities the hardest.

Today, between 3.3 billion and 3.6 billion people live in countries that are highly vulnerable to climate impacts, with global hotspots concentrated in the Arctic, Central and South America, Small Island Developing states, South Asia and much of sub-Saharan Africa. Across many countries in these regions, conflict, existing inequalities and development challenges (e.g., poverty and limited access to basic services like clean water) not only heighten sensitivity to climate hazards, but also limit communities’ capacity to adapt.  Mortality from storms, floods and droughts, for instance, was 15 times higher in countries with high vulnerability to climate change than in those with very low vulnerability from 2010 to 2020.

At the same time, efforts to mitigate climate change also risk disruptive changes and exacerbating inequity. Retiring coal-fired power plants, for instance, may displace workers, harm local economies and reconfigure the social fabric of communities, while inappropriately implemented efforts to halt deforestation could heighten poverty and intensify food insecurity. And certain climate policies, such as  carbon taxes  that raise the cost of emissions-intensive goods like gasoline, can also prove to be regressive, absent of efforts to recycle the revenues raised from these taxes back into programs that benefit low-income communities.

Fortunately, the IPCC identifies a range of measures that can support a just transition and help ensure that no one is left behind as the world moves toward a net-zero-emissions, climate-resilient future. Reconfiguring social protection programs (e.g., cash transfers, public works programs and social safety nets) to include adaptation, for example, can reduce communities’ vulnerability to a wide range of future climate impacts, while strengthening justice and equity. Such programs are particularly effective when paired with efforts to expand access to infrastructure and basic services.

Similarly, policymakers can design mitigation strategies to better distribute the costs and benefits of reducing GHG emissions. Governments can pair efforts to phase out coal-fired electricity generation, for instance, with subsidized job retraining programs that support workers in developing the skills needed to secure new, high-quality jobs. Or, in another example, officials can couple policy interventions dedicated to expanding access to public transit with interventions to improve access to nearby, affordable housing.

Across both mitigation and adaptation measures, inclusive, transparent and participatory decision-making processes will play a central role in ensuring a just transition. More specifically, these forums can help cultivate public trust, deepen public support for transformative climate action and avoid unintended consequences.

Looking Ahead

The IPCC’s AR6 makes clear that risks of inaction on climate are immense and the way ahead requires change at a scale not seen before. However, this report also serves as a reminder that we have never had more information about the gravity of the climate emergency and its cascading impacts — or about what needs to be done to reduce intensifying risks.

Limiting global temperature rise to 1.5 degrees C (2.7 degrees F) is still possible, but only if we act immediately. As the IPCC makes clear, the world needs to peak GHG emissions before 2025 at the very latest, nearly halve GHG emissions by 2030 and reach net-zero CO2 emissions around mid-century, while also ensuring a just and equitable transition. We’ll also need an all-hands-on-deck approach to guarantee that communities experiencing increasingly harmful impacts of the climate crisis have the resources they need to adapt to this new world. Governments, the private sector, civil society and individuals must all step up to keep the future we desire in sight. A narrow window of opportunity is still open, but there’s not one second to waste.

Note: In addition to showcasing findings from the IPCC’s AR6 Synthesis Report, this article also draws on previous articles detailing the IPCC’s findings on  the physical science of climate change ,  impacts, adaption and vulnerability ,  and  climate change mitigation .

Relevant Work

6 takeaways from the 2022 ipcc climate change mitigation report, 6 big findings from the ipcc 2022 report on climate impacts, adaptation and vulnerability, 5 big findings from the ipcc’s 2021 climate report, 8 things you need to know about the ipcc 1.5˚c report.

Join us on March 23 for a high-level webinar featuring IPCC authors, government representatives and leading carbon removal experts to discuss how carbon removal is a critical tool in our toolbox to address the climate crisis.

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Envision a world where everyone can enjoy clean air, walkable cities, vibrant landscapes, nutritious food and affordable energy.

11 min read

Seven case studies in carbon and climate

Every part of the mosaic of Earth's surface — ocean and land, Arctic and tropics, forest and grassland — absorbs and releases carbon in a different way. Wild-card events such as massive wildfires and drought complicate the global picture even more. To better predict future climate, we need to understand how Earth's ecosystems will change as the climate warms and how extreme events will shape and interact with the future environment. Here are seven pressing concerns.

The Far North is warming twice as fast as the rest of Earth, on average. With a 5-year Arctic airborne observing campaign just wrapping up and a 10-year campaign just starting that will integrate airborne, satellite and surface measurements, NASA is using unprecedented resources to discover how the drastic changes in Arctic carbon are likely to influence our climatic future.

Wildfires have become common in the North. Because firefighting is so difficult in remote areas, many of these fires burn unchecked for months, throwing huge plumes of carbon into the atmosphere. A recent report found a nearly 10-fold increase in the number of large fires in the Arctic region over the last 50 years, and the total area burned by fires is increasing annually.

Organic carbon from plant and animal remains is preserved for millennia in frozen Arctic soil, too cold to decompose. Arctic soils known as permafrost contain more carbon than there is in Earth's atmosphere today. As the frozen landscape continues to thaw, the likelihood increases that not only fires but decomposition will create Arctic atmospheric emissions rivaling those of fossil fuels. The chemical form these emissions take — carbon dioxide or methane — will make a big difference in how much greenhouse warming they create.

Initial results from NASA's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) airborne campaign have allayed concerns that large bursts of methane, a more potent greenhouse gas, are already being released from thawing Arctic soils. CARVE principal investigator Charles Miller of NASA's Jet Propulsion Laboratory (JPL), Pasadena, California, is looking forward to NASA's ABoVE field campaign (Arctic Boreal Vulnerability Experiment) to gain more insight. "CARVE just scratched the surface, compared to what ABoVE will do," Miller said.

Methane is the Billy the Kid of carbon-containing greenhouse gases: it does a lot of damage in a short life. There's much less of it in Earth's atmosphere than there is carbon dioxide, but molecule for molecule, it causes far more greenhouse warming than CO 2 does over its average 10-year life span in the atmosphere.

Methane is produced by bacteria that decompose organic material in damp places with little or no oxygen, such as freshwater marshes and the stomachs of cows. Currently, over half of atmospheric methane comes from human-related sources, such as livestock, rice farming, landfills and leaks of natural gas. Natural sources include termites and wetlands. Because of increasing human sources, the atmospheric concentration of methane has doubled in the last 200 years to a level not seen on our planet for 650,000 years.

Locating and measuring human emissions of methane are significant challenges. NASA's Carbon Monitoring System is funding several projects testing new technologies and techniques to improve our ability to monitor the colorless gas and help decision makers pinpoint sources of emissions. One project, led by Daniel Jacob of Harvard University, used satellite observations of methane to infer emissions over North America. The research found that human methane emissions in eastern Texas were 50 to 100 percent higher than previous estimates. "This study shows the potential of satellite observations to assess how methane emissions are changing," said Kevin Bowman, a JPL research scientist who was a coauthor of the study.

Tropical forests

Tropical forests are carbon storage heavyweights. The Amazon in South America alone absorbs a quarter of all carbon dioxide that ends up on land. Forests in Asia and Africa also do their part in "breathing in" as much carbon dioxide as possible and using it to grow.

However, there is evidence that tropical forests may be reaching some kind of limit to growth. While growth rates in temperate and boreal forests continue to increase, trees in the Amazon have been growing more slowly in recent years. They've also been dying sooner. That's partly because the forest was stressed by two severe droughts in 2005 and 2010 — so severe that the Amazon emitted more carbon overall than it absorbed during those years, due to increased fires and reduced growth. Those unprecedented droughts may have been only a foretaste of what is ahead, because models predict that droughts will increase in frequency and severity in the future.

In the past 40-50 years, the greatest threat to tropical rainforests has been not climate but humans, and here the news from the Amazon is better. Brazil has reduced Amazon deforestation in its territory by 60 to 70 percent since 2004, despite troubling increases in the last three years. According to Doug Morton, a scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, further reductions may not make a marked difference in the global carbon budget. "No one wants to abandon efforts to preserve and protect the tropical forests," he said. "But doing that with the expectation that [it] is a meaningful way to address global greenhouse gas emissions has become less defensible."

In the last few years, Brazil's progress has left Indonesia the distinction of being the nation with the highest deforestation rate and also with the largest overall area of forest cleared in the world. Although Indonesia's forests are only a quarter to a fifth the extent of the Amazon, fires there emit massive amounts of carbon, because about half of the Indonesian forests grow on carbon-rich peat. A recent study estimated that this fall, daily greenhouse gas emissions from recent Indonesian fires regularly surpassed daily emissions from the entire United States.

Wildfires are natural and necessary for some forest ecosystems, keeping them healthy by fertilizing soil, clearing ground for young plants, and allowing species to germinate and reproduce. Like the carbon cycle itself, fires are being pushed out of their normal roles by climate change. Shorter winters and higher temperatures during the other seasons lead to drier vegetation and soils. Globally, fire seasons are almost 20 percent longer today, on average, than they were 35 years ago.

Currently, wildfires are estimated to spew 2 to 4 billion tons of carbon into the atmosphere each year on average — about half as much as is emitted by fossil fuel burning. Large as that number is, it's just the beginning of the impact of fires on the carbon cycle. As a burned forest regrows, decades will pass before it reaches its former levels of carbon absorption. If the area is cleared for agriculture, the croplands will never absorb as much carbon as the forest did.

As atmospheric carbon dioxide continues to increase and global temperatures warm, climate models show the threat of wildfires increasing throughout this century. In Earth's more arid regions like the U.S. West, rising temperatures will continue to dry out vegetation so fires start and burn more easily. In Arctic and boreal ecosystems, intense wildfires are burning not just the trees, but also the carbon-rich soil itself, accelerating the thaw of permafrost, and dumping even more carbon dioxide and methane into the atmosphere.

North American forests

With decades of Landsat satellite imagery at their fingertips, researchers can track changes to North American forests since the mid-1980s. A warming climate is making its presence known.

Through the North American Forest Dynamics project, and a dataset based on Landsat imagery released this earlier this month, researchers can track where tree cover is disappearing through logging, wildfires, windstorms, insect outbreaks, drought, mountaintop mining, and people clearing land for development and agriculture. Equally, they can see where forests are growing back over past logging projects, abandoned croplands and other previously disturbed areas.

"One takeaway from the project is how active U.S. forests are, and how young American forests are," said Jeff Masek of Goddard, one of the project’s principal investigators along with researchers from the University of Maryland and the U.S. Forest Service. In the Southeast, fast-growing tree farms illustrate a human influence on the forest life cycle. In the West, however, much of the forest disturbance is directly or indirectly tied to climate. Wildfires stretched across more acres in Alaska this year than they have in any other year in the satellite record. Insects and drought have turned green forests brown in the Rocky Mountains. In the Southwest, pinyon-juniper forests have died back due to drought.

Scientists are studying North American forests and the carbon they store with other remote sensing instruments. With radars and lidars, which measure height of vegetation from satellite or airborne platforms, they can calculate how much biomass — the total amount of plant material, like trunks, stems and leaves — these forests contain. Then, models looking at how fast forests are growing or shrinking can calculate carbon uptake and release into the atmosphere. An instrument planned to fly on the International Space Station (ISS), called the Global Ecosystem Dynamics Investigation (GEDI) lidar, will measure tree height from orbit, and a second ISS mission called the Ecosystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) will monitor how forests are using water, an indicator of their carbon uptake during growth. Two other upcoming radar satellite missions (the NASA-ISRO SAR radar, or NISAR, and the European Space Agency’s BIOMASS radar) will provide even more complementary, comprehensive information on vegetation.

Ocean carbon absorption

When carbon-dioxide-rich air meets seawater containing less carbon dioxide, the greenhouse gas diffuses from the atmosphere into the ocean as irresistibly as a ball rolls downhill. Today, about a quarter of human-produced carbon dioxide emissions get absorbed into the ocean. Once the carbon is in the water, it can stay there for hundreds of years.

Warm, CO 2 -rich surface water flows in ocean currents to colder parts of the globe, releasing its heat along the way. In the polar regions, the now-cool water sinks several miles deep, carrying its carbon burden to the depths. Eventually, that same water wells up far away and returns carbon to the surface; but the entire trip is thought to take about a thousand years. In other words, water upwelling today dates from the Middle Ages – long before fossil fuel emissions.

That's good for the atmosphere, but the ocean pays a heavy price for absorbing so much carbon: acidification. Carbon dioxide reacts chemically with seawater to make the water more acidic. This fundamental change threatens many marine creatures. The chain of chemical reactions ends up reducing the amount of a particular form of carbon — the carbonate ion — that these organisms need to make shells and skeletons. Dubbed the “other carbon dioxide problem,” ocean acidification has potential impacts on millions of people who depend on the ocean for food and resources.

Phytoplankton

Microscopic, aquatic plants called phytoplankton are another way that ocean ecosystems absorb carbon dioxide emissions. Phytoplankton float with currents, consuming carbon dioxide as they grow. They are at the base of the ocean's food chain, eaten by tiny animals called zooplankton that are then consumed by larger species. When phytoplankton and zooplankton die, they may sink to the ocean floor, taking the carbon stored in their bodies with them.

Satellite instruments like the Moderate resolution Imaging Spectroradiometer (MODIS) on NASA's Terra and Aqua let us observe ocean color, which researchers can use to estimate abundance — more green equals more phytoplankton. But not all phytoplankton are equal. Some bigger species, like diatoms, need more nutrients in the surface waters. The bigger species also are generally heavier so more readily sink to the ocean floor.

As ocean currents change, however, the layers of surface water that have the right mix of sunlight, temperature and nutrients for phytoplankton to thrive are changing as well. “In the Northern Hemisphere, there’s a declining trend in phytoplankton,” said Cecile Rousseaux, an oceanographer with the Global Modeling and Assimilation Office at Goddard. She used models to determine that the decline at the highest latitudes was due to a decrease in abundance of diatoms. One future mission, the Pre-Aerosol, Clouds, and ocean Ecosystem (PACE) satellite, will use instruments designed to see shades of color in the ocean — and through that, allow scientists to better quantify different phytoplankton species.

In the Arctic, however, phytoplankton may be increasing due to climate change. The NASA-sponsored Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment (ICESCAPE) expedition on a U.S. Coast Guard icebreaker in 2010 and 2011 found unprecedented phytoplankton blooms under about three feet (a meter) of sea ice off Alaska. Scientists think this unusually thin ice allows sunlight to filter down to the water, catalyzing plant blooms where they had never been observed before.

Related Terms

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Scientific Consensus

It’s important to remember that scientists always focus on the evidence, not on opinions. Scientific evidence continues to show that human activities ( primarily the human burning of fossil fuels ) have warmed Earth’s surface and its ocean basins, which in turn have continued to impact Earth’s climate . This is based on over a century of scientific evidence forming the structural backbone of today's civilization.

NASA Global Climate Change presents the state of scientific knowledge about climate change while highlighting the role NASA plays in better understanding our home planet. This effort includes citing multiple peer-reviewed studies from research groups across the world, 1 illustrating the accuracy and consensus of research results (in this case, the scientific consensus on climate change) consistent with NASA’s scientific research portfolio.

With that said, multiple studies published in peer-reviewed scientific journals 1 show that climate-warming trends over the past century are extremely likely due to human activities. In addition, most of the leading scientific organizations worldwide have issued public statements endorsing this position. The following is a partial list of these organizations, along with links to their published statements and a selection of related resources.

American Scientific Societies

Statement on climate change from 18 scientific associations.

"Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver." (2009) 2

American Association for the Advancement of Science

"Based on well-established evidence, about 97% of climate scientists have concluded that human-caused climate change is happening." (2014) 3

American Chemical Society

"The Earth’s climate is changing in response to increasing concentrations of greenhouse gases (GHGs) and particulate matter in the atmosphere, largely as the result of human activities." (2016-2019) 4

American Geophysical Union

"Based on extensive scientific evidence, it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century. There is no alterative explanation supported by convincing evidence." (2019) 5

American Medical Association

"Our AMA ... supports the findings of the Intergovernmental Panel on Climate Change’s fourth assessment report and concurs with the scientific consensus that the Earth is undergoing adverse global climate change and that anthropogenic contributions are significant." (2019) 6

American Meteorological Society

"Research has found a human influence on the climate of the past several decades ... The IPCC (2013), USGCRP (2017), and USGCRP (2018) indicate that it is extremely likely that human influence has been the dominant cause of the observed warming since the mid-twentieth century." (2019) 7

American Physical Society

"Earth's changing climate is a critical issue and poses the risk of significant environmental, social and economic disruptions around the globe. While natural sources of climate variability are significant, multiple lines of evidence indicate that human influences have had an increasingly dominant effect on global climate warming observed since the mid-twentieth century." (2015) 8

The Geological Society of America

"The Geological Society of America (GSA) concurs with assessments by the National Academies of Science (2005), the National Research Council (2011), the Intergovernmental Panel on Climate Change (IPCC, 2013) and the U.S. Global Change Research Program (Melillo et al., 2014) that global climate has warmed in response to increasing concentrations of carbon dioxide (CO2) and other greenhouse gases ... Human activities (mainly greenhouse-gas emissions) are the dominant cause of the rapid warming since the middle 1900s (IPCC, 2013)." (2015) 9

Science Academies

International academies: joint statement.

"Climate change is real. There will always be uncertainty in understanding a system as complex as the world’s climate. However there is now strong evidence that significant global warming is occurring. The evidence comes from direct measurements of rising surface air temperatures and subsurface ocean temperatures and from phenomena such as increases in average global sea levels, retreating glaciers, and changes to many physical and biological systems. It is likely that most of the warming in recent decades can be attributed to human activities (IPCC 2001)." (2005, 11 international science academies) 1 0

U.S. National Academy of Sciences

"Scientists have known for some time, from multiple lines of evidence, that humans are changing Earth’s climate, primarily through greenhouse gas emissions." 1 1

U.S. Government Agencies

U.s. global change research program.

"Earth’s climate is now changing faster than at any point in the history of modern civilization, primarily as a result of human activities." (2018, 13 U.S. government departments and agencies) 12

Intergovernmental Bodies

Intergovernmental panel on climate change.

“It is unequivocal that the increase of CO 2 , methane, and nitrous oxide in the atmosphere over the industrial era is the result of human activities and that human influence is the principal driver of many changes observed across the atmosphere, ocean, cryosphere, and biosphere. “Since systematic scientific assessments began in the 1970s, the influence of human activity on the warming of the climate system has evolved from theory to established fact.” 1 3-17

Other Resources

List of worldwide scientific organizations.

The following page lists the nearly 200 worldwide scientific organizations that hold the position that climate change has been caused by human action. http://www.opr.ca.gov/facts/list-of-scientific-organizations.html

U.S. Agencies

The following page contains information on what federal agencies are doing to adapt to climate change. https://www.c2es.org/site/assets/uploads/2012/02/climate-change-adaptation-what-federal-agencies-are-doing.pdf

Technically, a “consensus” is a general agreement of opinion, but the scientific method steers us away from this to an objective framework. In science, facts or observations are explained by a hypothesis (a statement of a possible explanation for some natural phenomenon), which can then be tested and retested until it is refuted (or disproved).

As scientists gather more observations, they will build off one explanation and add details to complete the picture. Eventually, a group of hypotheses might be integrated and generalized into a scientific theory, a scientifically acceptable general principle or body of principles offered to explain phenomena.

1. K. Myers, et al, "Consensus revisited: quantifying scientific agreement on climate change and climate expertise among Earth scientists 10 years later", Environmental Research Letters Vol.16 No. 10, 104030 (20 October 2021); DOI:10.1088/1748-9326/ac2774 M. Lynas, et al, "Greater than 99% consensus on human caused climate change in the peer-reviewed scientific literature", Environmental Research Letters Vol.16 No. 11, 114005 (19 October 2021); DOI:10.1088/1748-9326/ac2966 J. Cook et al., "Consensus on consensus: a synthesis of consensus estimates on human-caused global warming", Environmental Research Letters Vol. 11 No. 4, (13 April 2016); DOI:10.1088/1748-9326/11/4/048002 J. Cook et al., "Quantifying the consensus on anthropogenic global warming in the scientific literature", Environmental Research Letters Vol. 8 No. 2, (15 May 2013); DOI:10.1088/1748-9326/8/2/024024 W. R. L. Anderegg, “Expert Credibility in Climate Change”, Proceedings of the National Academy of Sciences Vol. 107 No. 27, 12107-12109 (21 June 2010); DOI: 10.1073/pnas.1003187107 P. T. Doran & M. K. Zimmerman, "Examining the Scientific Consensus on Climate Change", Eos Transactions American Geophysical Union Vol. 90 Issue 3 (2009), 22; DOI: 10.1029/2009EO030002 N. Oreskes, “Beyond the Ivory Tower: The Scientific Consensus on Climate Change”, Science Vol. 306 no. 5702, p. 1686 (3 December 2004); DOI: 10.1126/science.1103618

2. Statement on climate change from 18 scientific associations (2009)

3. AAAS Board Statement on Climate Change (2014)

4. ACS Public Policy Statement: Climate Change (2016-2019)

5. Society Must Address the Growing Climate Crisis Now (2019)

6. Global Climate Change and Human Health (2019)

7. Climate Change: An Information Statement of the American Meteorological Society (2019)

8. American Physical Society (2021)

9. GSA Position Statement on Climate Change (2015)

10. Joint science academies' statement: Global response to climate change (2005)

11. Climate at the National Academies

12. Fourth National Climate Assessment: Volume II (2018)

13. IPCC Fifth Assessment Report, Summary for Policymakers, SPM 1.1 (2014)

14. IPCC Fifth Assessment Report, Summary for Policymakers, SPM 1 (2014)

15. IPCC Sixth Assessment Report, Working Group 1 (2021)

16. IPCC Sixth Assessment Report, Working Group 2 (2022)

17. IPCC Sixth Assessment Report, Working Group 3 (2022)

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Call for case studies on climate change and health

The year 2021 is due to be a crucial year for international climate action, with far-reaching consequences for the long-term health and resilience of communities and societies. In recovering from the global shock caused by COVID-19 - and the resulting damage to livelihoods, health, and sustainable development – governments are increasingly urged to prioritise a healthy and sustainable recovery of their economies that takes into account the broader social and environmental determinants of health.

In May 2020, millions of health professionals called for a healthy recovery , and WHO released its  Manifesto for a green, healthy recovery from COVID-19 , laying out 6 prescriptions and over 70 actionables for more sustainable and healthy societies post-COVID.

In 2021, WHO and the global health community will continue to drive the conversation on recovery and resilience by envisioning how a healthy, equitable recovery from COVID-19 can advance the rapid decarbonization of the world economy. To further this goal, WHO will be collecting case studies on health and climate change, to be highlighted in upcoming events and initiatives throughout the year, including at the COP26 climate conference.

What kind of case studies are we looking for?

We are looking for short, real-life stories about an initiative, project or advocacy campaign that showcase some of the great work that is already being implemented to reduce the impact of climate change on human health, and to help communities and societies recover from COVID-19 and transition to a healthy, climate-resilient and climate-just future. Sharing experiences of less successful case studies and lessons learned is also welcome. 

What should a climate & health case study look like?

• Be solutions-driven : make sure your case study is a concrete and real-life example of progress being made on reducing the impacts of climate change on human health;
• Be visual : share images, video or graphic elements if possible;
• Be diverse : highlight different stakeholders and sectors driving positive change, such as representatives from cities, regions, businesses and civil society from sectors such as health, biodiversity, transport, economy and energy, as well as health professionals, scientists, policymakers, celebrities, local authorities and mayors, government representatives, representatives from vulnerable communities and youth leaders;
• Be personal : show the people behind the initiative, and share at least 1 quote or personal perspective, ideally from a person directly involved in the project or from an expert in the field;
• Be short and concise : limit your story to 1-1.5 page (1200 words max), if possible.

How to submit a case study?

The case studies can be submitted via this online form or in text format (1200 words max) , following the guiding questions , by email to [email protected] . The guiding questions are meant to help you structure your case study and help ensure all relevant information is present, but are not mandatory. Complementing the case studies with visual materials, such as photos from the field, would be most welcome.

Interested organizations and individuals are also encouraged to showcase their projects by submitting a short 1-2 minute video with footage and testimonials from the field, by email to [email protected] . These recordings could be used to create an advocacy video “The healthy, equitable and climate resilient future we want” that will be projected at the 2021 Global Conference on Health and Climate Change at the margin of COP26.

The deadline for submitting the case studies is August 31 st .

How will the case studies be used?

A selection of case studies will be presented at the upcoming Regional consultations on Climate Change and Health prepared by the World Health Organization (WHO) and the Global Climate and Health Alliance (GCHA) in April-May 2021.

Case studies will also be featured in the COP26 Special Report "The Health Argument for Climate Action", to be published in November 2021, and will be featured on the WHO website and on a forthcoming WHO/WMO Online Portal on Climate Change and Health*.

*Selected submissions will be further co-developed into case studies in collaboration with the WHO climate change team. Case studies aim to highlight the scope and diversity of ongoing global efforts on climate change and health, but do not necessarily imply endorsement from WHO.

Regional Consultations on Climate Change and Health

2021 Global Conference on Health and Climate Change

COP26 Case Studies on Climate Change and Health

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Case study Template - Guiding questions

WHO Call for Case Studies on Climate Change and Health

July 23, 2020

Worst- and Best-Case Scenarios for Warming Less Likely, Groundbreaking Study Finds

The research narrows the range for how much Earth’s average temperature may rise if CO 2 levels are doubled

By Chelsea Harvey & E&E News

Caspar Benson Getty Images

How much warming will greenhouse gas emissions cause in the coming years? It’s one of the most fundamental questions about climate change—and also one of the trickiest to answer.

Now, a  major study  claims to have narrowed down the range of possible estimates.

It presents both good and bad news. The worst-case climate scenarios may be somewhat less likely than previous studies suggested. But the best-case climate scenarios—those assuming the least amount of warming—are almost certainly not going to happen.

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It’s “the most important climate science paper that’s come out in several years,” according to climate scientist Andrew Dessler of Texas A&M University, who was not involved with the study.

The effort also illuminates some of the challenges of a decadeslong scientific quest to predict the strength of future climate change.

At the heart of the new study is a concept known as “climate sensitivity”—how sensitive the Earth is to greenhouse gas emissions and how much it’s likely to warm in response. In studies, scientists often focus on the amount of warming that might be expected if carbon dioxide concentrations doubled their preindustrial levels.

It’s a hypothetical scenario, but one that’s not impossible.

Prior to the industrial era—around 150 years ago—global CO 2 concentrations hovered around 280 parts per million in the atmosphere. Doubling that amount would put the total at 560 ppm.

Today, CO 2 levels have climbed above 400 ppm.

The metric has existed for decades now. In 1979, a groundbreaking  report  led by Massachusetts Institute of Technology scientist Jule Charney—dubbed the “Charney Report”—suggested the planet’s climate sensitivity probably fell within a range of 1.5 to 4.5 degrees Celsius for a doubling of CO 2 .

In the years since, that range hasn’t changed much. Most studies have found that the amount of warming to be expected after a doubling of CO 2 probably falls within those boundaries.

The most recent assessment report from the United Nations’ Intergovernmental Panel on Climate Change, published in 2014, suggested there was about a 66% chance—a “likely” probability, in other words—that the climate sensitivity range falls between 1.5 and 4.5 C. That’s anywhere from 2.7 to 8.1 degrees Fahrenheit.

Many of the difficulties narrowing the range have stemmed from the sheer complexity of the question.

In a simple sense, greenhouse gases in the atmosphere warm the Earth by trapping heat from the sun that would otherwise be radiated back out into space. But there are other factors that can affect the total amount of warming the planet experiences over time.

These include physical changes in the air that makes up the atmosphere, the amount of water vapor in the atmosphere, and the melting of snow and ice on the Earth’s surface, which can speed up the rate of climate change as they disappear.

Then there’s the question of cloud feedbacks, often cited by scientists as one of the biggest uncertainties about future climate change. Warming in the atmosphere can change the size, density and lifespan of clouds. And clouds, in turn, are capable of either worsening or lessening global warming, depending on their characteristics.

Over the years, though, scientists have dramatically improved their understanding of the Earth’s climate response.

“Behind the scenes, underneath the hood, our understanding of a lot of the processes was much better,” Dessler told E&E News. “And so I think that even though the range hadn’t changed, that masked a real tremendous improvement in our understanding.”

Narrowing the range

The new study narrows the range at both ends, particularly the lower end. It finds there’s a 66% chance that the sensitivity range falls between 2.6 and 3.9 C of warming (4.9 to 7 F).

Several factors made the revised estimates possible.

Perhaps most importantly, the new study investigates multiple lines of evidence when it comes to climate sensitivity. It uses global climate models, which simulate large-scale processes across the whole world. It also uses detailed, process-based models, which can simulate fine-scale events related to the formation of clouds.

It also examines the Earth’s response to recent greenhouse gas emissions, since the onset of the industrial era. And it even uses ancient ice and sediment samples to look back at the Earth’s long-term climate history and evaluate how the planet changed in the past.

It’s a departure from many other recent sensitivity studies, according to Mark Zelinka, an atmospheric scientist at Lawrence Livermore National Laboratory and one of the study’s co-authors.

Most papers have focused on individual categories of evidence—for instance, only looking at the Earth’s ancient climate, or only investigating cloud feedbacks.

In an email to E&E News, Zelinka noted that “the various lines of evidence related to climate sensitivity have never really been systematically brought together and analyzed in concert.”

That’s critical for a question with so many different factors playing a role, and so many possible ways of investigating them.

This approach has allowed the authors to reduce their uncertainties about the new estimates, Dessler noted.

“What they’ve done here, effectively, is a meta-analysis of all the previous studies,” he said. “And then they use a statistical framework to try to take everything that people have published on this and everything we know and try to ask the question: What range of climate sensitivity is consistent with all of the evidence that’s out there?”

And since the new report relies on so many previous studies of climate sensitivity, it’s benefited from years of advancements in scientists’ understanding of the Earth’s climate system.

Clouds, in particular, are helping to close the gaps.

“The primary reason for difficulty in narrowing the range over the years is that we do not know well enough how clouds will respond to warming,” said Zelinka. “We have made a lot of progress on this recently, and this has contributed to narrowing the range.”

The new report devotes a large chunk of its analysis exclusively to clouds. It examines the growing body of science on how different types of clouds respond to climate change, and how changes in these clouds may affect future climate change.

The mounting evidence suggests that clouds are unlikely to mitigate climate change on a global scale, the report concludes. On the contrary, they’re more likely to make it worse.

With a new, more confident sensitivity estimate in hand, the report begs the question: What does this mean for future climate policy?

On the one hand, the study strikes a blow to a favorite argument used by climate deniers: The uncertainty about climate sensitivity suggests future warming might not actually be that severe.

The new report strongly suggests that the best-case sensitivity scenarios—those at the lower end of the old ranges—are probably not in the cards.

Still, the revised range doesn’t change much when it comes to the international climate goals outlined by the Paris Agreement. Nations worldwide are striving to keep global temperatures within 2 C of their preindustrial levels.

To reach that target, world leaders would have to ensure global CO 2 concentrations never double at all.

“It’s not clear to me how much we would gain from further decreases in the uncertainty” of this metric, Dessler said. “What this has done, in my opinion, is it’s really moved the game away from these questions about the physics of the climate system into questions about how are humans going to react to climate change.”

Reprinted from Climatewire with permission from E&E News. E&E provides daily coverage of essential energy and environmental news at  www.eenews.net .

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What We Do: Case Studies in Climate Change

Field trip lets students study climate change in the living lab of Eastern California.

Danielle Underferth

When it comes to climate change, California provides an ideal case study. And Scot Miller wants his students to be where the science is.

Miller, an assistant professor in the Whiting School of Engineering, took students on a field trip to Death Valley this spring to round out their classwork for the seminar Case Studies in Climate Change. The trip was designed to give the group a thorough understanding of how the Earth’s climate has fluctuated over time, how those fluctuations can be traced in the physical environment, and how one state – California – is managing repercussions from the rapid, human-made changes underway now.

Studying the past to understand the present

Climate change is not a new phenomenon. Over the past several million years, the Earth's climate has changed dramatically, with periods dominated by roaming glaciers and even a “snowball Earth” phase, when the entire globe was covered in ice.

Death Valley National Park and Eastern California are excellent locations to observe evidence of these changes, says Miller. “The region is a hub of global research on past climate change.”

It’s also an ideal place to study and understand the impacts of current climate change, he says.

“There is arguably no state that is more heavily impacted by current climate change than California, and the state government has taken global leadership by enacting innovative climate mitigation and management policies.”

Learning across disciplines

In order to understand climate trends and impacts, Miller’s students studied and did field work in the areas of geology, ecology, chemistry, meteorology, hydrology, and even public policy.

Activities included mapping and interpreting geological formations that show how the Earth swung from cold to hot climate extremes, measuring trees in different ecosystems to estimate how much carbon is locked up in certain ecosystems, and then modeling how carbon storage may change as those ecosystems adjust to a changing climate, collecting tree cores to observe variations in climate that stressed or benefited trees, and evaluating how California’s policies improve, or in some cases worsen climate stresses.

"The class was an amazing opportunity to learn about our climate not only through books and pictures but also through the experience of seeing the evidence of a changing climate in person,” said student Madi Miro. “It was definitely one of the best experiences I was able to have at Hopkins."

For Miller, it’s important for students to learn not just about how climate is changing, but also about how scientists track the magnitude and impacts of climate change.

“I strongly believe that field-based and experiential learning can bring academic material to life. While in the field, we can connect academic climate science and academic discussions of policy with real-world climate impacts that are already starting to occur,” he says. “Climate change is more than an abstract academic subject. It’s a phenomenon that’s happening in the here and now, and we can see these impacts around us if we know where to look.”

Environmental Health and Engineering is a cross-divisional department spanning the Bloomberg School of Public Health and the Whiting School of Engineering. This hybrid department is uniquely designed to lead pioneering research and prepare the next generation of scholars to solve critical and complex issues at the interface of public health and engineering.

U.S. Climate Resilience Toolkit

• Steps to Resilience
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Communities, businesses, and individuals are taking action to document their vulnerabilities and build resilience to climate-related impacts. Click dots on the map to preview case studies, or browse stories below the map. Use the drop-down menus above to find stories of interest. To expand your results, click the Clear Filters link.

A Climate for Resilience

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Alert System Helps Strawberry Growers Reduce Costs

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Boise's Climate Action Roadmap

Newsroom Post

Climate change: a threat to human wellbeing and health of the planet. taking action now can secure our future.

BERLIN, Feb 28 – Human-induced climate change is causing dangerous and widespread disruption in nature and affecting the lives of billions of people around the world, despite efforts to reduce the risks. People and ecosystems least able to cope are being hardest hit, said scientists in the latest Intergovernmental Panel on Climate Change (IPCC) report, released today.

“This report is a dire warning about the consequences of inaction,” said Hoesung Lee, Chair of the IPCC. “It shows that climate change is a grave and mounting threat to our wellbeing and a healthy planet. Our actions today will shape how people adapt and nature responds to increasing climate risks.”

The world faces unavoidable multiple climate hazards over the next two decades with global warming of 1.5°C (2.7°F). Even temporarily exceeding this warming level will result in additional severe impacts, some of which will be irreversible. Risks for society will increase, including to infrastructure and low-lying coastal settlements.

The Summary for Policymakers of the IPCC Working Group II report,  Climate Change 2022: Impacts, Adaptation and Vulnerability was approved on Sunday, February 27 2022, by 195 member governments of the IPCC, through a virtual approval session that was held over two weeks starting on February 14.

Urgent action required to deal with increasing risks

Increased heatwaves, droughts and floods are already exceeding plants’ and animals’ tolerance thresholds, driving mass mortalities in species such as trees and corals. These weather extremes are occurring simultaneously, causing cascading impacts that are increasingly difficult to manage. They have exposed millions of people to acute food and water insecurity, especially in Africa, Asia, Central and South America, on Small Islands and in the Arctic.

To avoid mounting loss of life, biodiversity and infrastructure, ambitious, accelerated action is required to adapt to climate change, at the same time as making rapid, deep cuts in greenhouse gas emissions. So far, progress on adaptation is uneven and there are increasing gaps between action taken and what is needed to deal with the increasing risks, the new report finds. These gaps are largest among lower-income populations. 

The Working Group II report is the second instalment of the IPCC’s Sixth Assessment Report (AR6), which will be completed this year.

“This report recognizes the interdependence of climate, biodiversity and people and integrates natural, social and economic sciences more strongly than earlier IPCC assessments,” said Hoesung Lee. “It emphasizes the urgency of immediate and more ambitious action to address climate risks. Half measures are no longer an option.”

Safeguarding and strengthening nature is key to securing a liveable future

There are options to adapt to a changing climate. This report provides new insights into nature’s potential not only to reduce climate risks but also to improve people’s lives.

“Healthy ecosystems are more resilient to climate change and provide life-critical services such as food and clean water”, said IPCC Working Group II Co-Chair Hans-Otto Pörtner. “By restoring degraded ecosystems and effectively and equitably conserving 30 to 50 per cent of Earth’s land, freshwater and ocean habitats, society can benefit from nature’s capacity to absorb and store carbon, and we can accelerate progress towards sustainable development, but adequate finance and political support are essential.”

Scientists point out that climate change interacts with global trends such as unsustainable use of natural resources, growing urbanization, social inequalities, losses and damages from extreme events and a pandemic, jeopardizing future development.

“Our assessment clearly shows that tackling all these different challenges involves everyone – governments, the private sector, civil society – working together to prioritize risk reduction, as well as equity and justice, in decision-making and investment,” said IPCC Working Group II Co-Chair Debra Roberts.

“In this way, different interests, values and world views can be reconciled. By bringing together scientific and technological know-how as well as Indigenous and local knowledge, solutions will be more effective. Failure to achieve climate resilient and sustainable development will result in a sub-optimal future for people and nature.”

Cities: Hotspots of impacts and risks, but also a crucial part of the solution

This report provides a detailed assessment of climate change impacts, risks and adaptation in cities, where more than half the world’s population lives. People’s health, lives and livelihoods, as well as property and critical infrastructure, including energy and transportation systems, are being increasingly adversely affected by hazards from heatwaves, storms, drought and flooding as well as slow-onset changes, including sea level rise.

“Together, growing urbanization and climate change create complex risks, especially for those cities that already experience poorly planned urban growth, high levels of poverty and unemployment, and a lack of basic services,” Debra Roberts said.

“But cities also provide opportunities for climate action – green buildings, reliable supplies of clean water and renewable energy, and sustainable transport systems that connect urban and rural areas can all lead to a more inclusive, fairer society.”

There is increasing evidence of adaptation that has caused unintended consequences, for example destroying nature, putting peoples’ lives at risk or increasing greenhouse gas emissions. This can be avoided by involving everyone in planning, attention to equity and justice, and drawing on Indigenous and local knowledge.

A narrowing window for action

Climate change is a global challenge that requires local solutions and that’s why the Working Group II contribution to the IPCC’s Sixth Assessment Report (AR6) provides extensive regional information to enable Climate Resilient Development.

The report clearly states Climate Resilient Development is already challenging at current warming levels. It will become more limited if global warming exceeds 1.5°C (2.7°F). In some regions it will be impossible if global warming exceeds 2°C (3.6°F). This key finding underlines the urgency for climate action, focusing on equity and justice. Adequate funding, technology transfer, political commitment and partnership lead to more effective climate change adaptation and emissions reductions.

“The scientific evidence is unequivocal: climate change is a threat to human wellbeing and the health of the planet. Any further delay in concerted global action will miss a brief and rapidly closing window to secure a liveable future,” said Hans-Otto Pörtner.

For more information, please contact:

IPCC Press Office, Email: [email protected]   IPCC Working Group II:  Sina Löschke,  Komila Nabiyeva: [email protected]

Notes for Editors

Climate Change 2022: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change

The Working Group II report examines the impacts of climate change on nature and people around the globe. It explores future impacts at different levels of warming and the resulting risks and offers options to strengthen nature’s and society’s resilience to ongoing climate change, to fight hunger, poverty, and inequality and keep Earth a place worth living on – for current as well as for future generations. 

Working Group II introduces several new components in its latest report: One is a special section on climate change impacts, risks and options to act for cities and settlements by the sea, tropical forests, mountains, biodiversity hotspots, dryland and deserts, the Mediterranean as well as the polar regions. Another is an atlas that will present data and findings on observed and projected climate change impacts and risks from global to regional scales, thus offering even more insights for decision makers.

The Summary for Policymakers of the Working Group II contribution to the Sixth Assessment Report (AR6) as well as additional materials and information are available at https://www.ipcc.ch/report/ar6/wg2/

Note : Originally scheduled for release in September 2021, the report was delayed for several months by the COVID-19 pandemic, as work in the scientific community including the IPCC shifted online. This is the second time that the IPCC has conducted a virtual approval session for one of its reports.

AR6 Working Group II in numbers

270 authors from 67 countries

• 47 – coordinating authors
• 184 – lead authors
• 39 – review editors
• 675 – contributing authors

Over 34,000 cited references

A total of 62,418 expert and government review comments

(First Order Draft 16,348; Second Order Draft 40,293; Final Government Distribution: 5,777)

More information about the Sixth Assessment Report can be found  here .

Additional media resources

Assets available after the embargo is lifted on Media Essentials website .

Press conference recording, collection of sound bites from WGII authors, link to presentation slides, B-roll of approval session, link to launch Trello board including press release and video trailer in UN languages, a social media pack.

The website includes  outreach materials  such as videos about the IPCC and video recordings from  outreach events  conducted as webinars or live-streamed events.

Most videos published by the IPCC can be found on our  YouTube  channel. Credit for artwork

About the IPCC

The Intergovernmental Panel on Climate Change (IPCC) is the UN body for assessing the science related to climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide political leaders with periodic scientific assessments concerning climate change, its implications and risks, as well as to put forward adaptation and mitigation strategies. In the same year the UN General Assembly endorsed the action by the WMO and UNEP in jointly establishing the IPCC. It has 195 member states.

Thousands of people from all over the world contribute to the work of the IPCC. For the assessment reports, IPCC scientists volunteer their time to assess the thousands of scientific papers published each year to provide a comprehensive summary of what is known about the drivers of climate change, its impacts and future risks, and how adaptation and mitigation can reduce those risks.

The IPCC has three working groups:  Working Group I , dealing with the physical science basis of climate change;  Working Group II , dealing with impacts, adaptation and vulnerability; and  Working Group III , dealing with the mitigation of climate change. It also has a  Task Force on National Greenhouse Gas Inventories  that develops methodologies for measuring emissions and removals. As part of the IPCC, a Task Group on Data Support for Climate Change Assessments (TG-Data) provides guidance to the Data Distribution Centre (DDC) on curation, traceability, stability, availability and transparency of data and scenarios related to the reports of the IPCC.

IPCC assessments provide governments, at all levels, with scientific information that they can use to develop climate policies. IPCC assessments are a key input into the international negotiations to tackle climate change. IPCC reports are drafted and reviewed in several stages, thus guaranteeing objectivity and transparency. An IPCC assessment report consists of the contributions of the three working groups and a Synthesis Report. The Synthesis Report integrates the findings of the three working group reports and of any special reports prepared in that assessment cycle.

About the Sixth Assessment Cycle

At its 41st Session in February 2015, the IPCC decided to produce a Sixth Assessment Report (AR6). At its 42nd Session in October 2015 it elected a new Bureau that would oversee the work on this report and the Special Reports to be produced in the assessment cycle.

Global Warming of 1.5°C , an IPCC special report on the impacts of global warming of 1.5 degrees Celsius above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty  was launched in October 2018.

Climate Change and Land , an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems  was launched in August 2019, and the  Special Report on the Ocean and Cryosphere in a Changing Climate  was released in September 2019.

In May 2019 the IPCC released the  2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories , an update to the methodology used by governments to estimate their greenhouse gas emissions and removals.

In August 2021 the IPCC released the Working Group I contribution to the AR6, Climate Change 2021, the Physical Science Basis

The Working Group III contribution to the AR6 is scheduled for early April 2022.

The Synthesis Report of the Sixth Assessment Report will be completed in the second half of 2022.

For more information go to  www.ipcc.ch

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Fifty-fifth session of the ipcc (ipcc-55) and twelfth session of working group ii (wgii-12), february 14, 2022, working group report, ar6 climate change 2022: impacts, adaptation and vulnerability.

Climate Change: Global Temperature

Yearly surface temperature from 1880–2023 compared to the 20th-century average (1901-2000). Blue bars indicate cooler-than-average years; red bars show warmer-than-average years. NOAA Climate.gov graph, based on data from the National Centers for Environmental Information.

Given the tremendous size and heat capacity of the global oceans, it takes a massive amount of added heat energy to raise Earth’s average yearly surface temperature even a small amount. The roughly 2-degree Fahrenheit (1 degrees Celsius) increase in global average surface temperature that has occurred since the pre-industrial era (1850-1900 in NOAA's record) might seem small, but it means a significant increase in accumulated heat.

That extra heat is driving regional and seasonal temperature extremes , reducing snow cover and sea ice , intensifying heavy rainfall, and changing habitat ranges for plants and animals —expanding some and shrinking others.  As the map below shows, most land areas have warmed faster than most ocean areas, and the Arctic is warming faster than most other regions. In addition, it's clear that the rate of warming over the past few decades is much faster than the average rate since the start of the 20th century.

Trends in annual surface temperature in the past few decades (1994-2023, bottom) compared to the trend since the start of the 20th century (1901-2023, top). Recent warming is much faster than the longer-term average, with some locations warming by 1 degree Fahrenheit or more per decade. Differences are most dramatic in the Arctic, where the loss of reflective ice and snow amplifies the rate of warming. NOAA Climate.gov, based on data provided by NOAA National Centers for Environmental Information.

About surface temperature

The concept of an average temperature for the entire globe may seem odd. After all, at this very moment, the highest and lowest temperatures on Earth are likely more than 100°F (55°C) apart. Temperatures vary from night to day and between seasonal extremes in the Northern and Southern Hemispheres. This means that some parts of Earth are quite cold while other parts are downright hot. To speak of the "average" temperature, then, may seem like nonsense. However, the concept of a global average temperature is convenient for detecting and tracking changes in Earth's energy budget—how much sunlight Earth absorbs minus how much it radiates to space as heat—over time.

To calculate a global average temperature, scientists begin with temperature measurements taken at locations around the globe. Because their goal is to track changes in temperature, measurements are converted from absolute temperature readings to temperature anomalies—the difference between the observed temperature and the long-term average temperature for each location and date. Multiple independent research groups across the world perform their own analysis of the surface temperature data, and they all show a similar upward trend.

Across inaccessible areas that have few measurements, scientists use surrounding temperatures and other information to estimate the missing values. Each value is then used to calculate a global temperature average. This process provides a consistent, reliable method for monitoring changes in Earth's surface temperature over time. Read more about how the global surface temperature record is built in our Climate Data Primer.

Global temperature in 2023

According to the 2023 Global Climate Report from NOAA National Centers for Environmental Information, every month of 2023 ranked among the 7 warmest for that month, and the months in the second half of the year (June-December) were each their hottest on record. In July, August, and September, global temperatures were more than 1.0°C (1.8°F) above the long-term average—the first time in NOAA's record any month has breached that threshold. 

Map of global average surface temperature in 2023 compared to the 1991-2020 average. Warmer-than-average areas are shades of red, and cooler-than-average areas are shades of blue. The darker the color, the bigger the difference from average. The animated bar graph shows global temperatures each year from 1976 (left) to 2023 (right) compared to the 1901-2000 average. 1976 (blue bar at far left) was the last time a year was cooler than the 20th-century average. 2023 (far right) set a new record for warmest year. NOAA Climate.gov image, based on data provided by NOAA National Centers for Environmental Information. 

Other 2023 rankings included...

• warmest year on record for land and ocean areas individually;
• warmest year for land and ocean individually in the North,
• 2nd-warmest year for land and warmest year for ocean in the South;
• 40th-warmest year for the Antarctic,
• 4th-warmest year for the Arctic.

For more regional details and 2023 climate statistics, see the 2023 Global Climate Report from NOAA's National Centers for Environmental Information. 

Past and future change in global temperature

Though warming has not been uniform across the planet, the upward trend in the globally averaged temperature shows that more areas are warming than cooling. According to NOAA's  2023 Annual Climate Report the combined land and ocean temperature has increased at an average rate of 0.11° Fahrenheit (0.06° Celsius) per decade since 1850, or about 2° F in total. The rate of warming since 1982 is more than three times as fast: 0.36° F (0.20° C) per decade.

According to the latest Synthesis Report ( pdf ) from the Intergovernmental Panel on Climate Change, there is no debate about the cause of this warming trend:

Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming, with global surface temperature reaching 1.1°C above 1850-1900 in 2011-2020.

In the IPCC's Sixth Assessment Report on the Physical Basis of Climate Change, experts summarized the relative influence of all things known to affect Earth's average surface temperature:

The likely range of total human-caused global surface temperature increase from 1850–1900 to 2010–2019 is 0.8°C to 1.3°C, with a best estimate of 1.07°C [2.01 ˚F]. Over this period, it is likely that well-mixed greenhouse gases (GHGs) contributed a warming of 1.0°C to 2.0°C, and other human drivers (principally aerosols) contributed a cooling of 0.0°C to 0.8°C, natural (solar and volcanic) drivers changed global surface temperature by –0.1°C to +0.1°C, and internal variability changed it by –0.2°C to +0.2°C.

The amount of future warming Earth will experience depends on how much carbon dioxide and other greenhouse gases we emit in coming decades. Today, our activities—burning fossil fuels and to a lesser extent clearing forests—add about 11 billion metric tons of carbon ( equivalent to a little over 40 billion metric tons of carbon dioxide ) to the atmosphere each year. Because that is more carbon than natural processes can remove, atmospheric carbon dioxide amounts increase each year.

( left ) Hypothetical pathways of carbon emissions ("representative concentration pathways," or RCPs) throughout the twenty-first century based on different possible energy policies and economic growth patterns. ( right )  Projected temperature increase relative to the 1901-1960 average depending on which RCP we eventually follow. Image by Katharine Hayhoe, from the 2017 Climate Science Special Report by the U.S. Global Change Research Program.

According to the 2017 U.S. Climate Science Special Report , if yearly emissions continue to increase rapidly, as they have since 2000, models project that by the end of this century, global temperature will be at least 5 degrees Fahrenheit warmer than the 1901-1960 average, and possibly as much as 10.2 degrees warmer. If annual emissions increase more slowly and begin to decline significantly by 2050,  models project temperatures would still be at least 2.4 degrees warmer than the first half of the 20 th century, and possibly up to 5.9 degrees warmer.

Key resources

• Climate at a Glance for NOAA global and national surface temperature maps, graphs, and underlying data.
• Maps of U.S. temperature and precipitation trends.
• The Climate Explorer for U.S. county-level maps and time series of past and future temperatures and climate impacts.

Global Carbon Project. (2023, December 4). Fossil CO2 emissions at record high in 2023. Accessed January 18, 2023, from  https://globalcarbonbudget.org/fossil-co2-emissions-at-record-high-in-2… .

NOAA National Centers for Environmental Information (2024). Annual 2023 Global Climate Report. Accessed January 17, 2024, from https://www.ncei.noaa.gov/access/monitoring/monthly-report/global/202313 .

IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 3−32, doi:10.1017/9781009157896.001.

IPCC, 2023: Summary for Policymakers. In: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland, pp. 1-34, doi: 10.59327/IPCC/AR6-9789291691647.001

USGCRP, 2017: Climate Science Special Report: Fourth National Climate Assessment, Volume I [Wuebbles, D.J., D.W. Fahey, K.A. Hibbard, D.J. Dokken, B.C. Stewart, and T.K. Maycock (eds.)]. U.S. Global Change Research Program, Washington, DC, USA, 470 pp., doi: 10.7930/J0J964J6.

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Deadly Landslides in India Made Worse by Climate Change, Study Finds

Extreme rainfall made 10 percent heavier by human-caused climate change triggered landslides that killed hundreds, according to a new study.

By Austyn Gaffney

A sudden burst of rainfall on July 30 caused a cascade of landslides that buried hundreds of people in the mountainous Kerala region of southern India.

That downpour was 10 percent heavier because of human-caused climate change, according to a study by World Weather Attribution, a group of scientists who quantify how climate change can influence extreme weather. Nearly six inches, or 150 millimeters, of rain fell on soils already highly saturated from two months of monsoon and marked the third highest single-day rain event on record for India.

“The devastation in northern Kerala is concerning not only because of the difficult humanitarian situation faced by thousands today, but also because this disaster occurred in a continually warming world,” said Maja Vahlberg, a climate risk consultant at the Red Cross Red Crescent Climate Centre. “The increase in climate-change-driven rainfall found in this study is likely to increase the number of landslides that could be triggered in the future.”

In a state that is highly prone to landslides, the Wayanad district is considered the riskiest part. As of Tuesday, at least 231 people had died and 100 remained missing.

The Kerala landslides were the second extreme landslide event in July, following one in Ethiopia that killed 257 people. July was the second-worst month on record, after July 2019, with 95 landslide events that caused 1,167 fatalities , according to data maintained by Dave Petley, the vice-chancellor of the University of Hull. Together, they caused roughly one-third of the more than 3,600 deaths resulting from some 429 fatal landslides recorded this year, Dr. Petley said in an email.

Already, 2024 is an outlier, Dr. Petley posted to The Landslide Blog on Tuesday . He wrote that he could “only speculate on the likely underlying reasons for this very high incidence of fatal landslides,” but “the most likely cause continues to be the exceptionally high global surface temperatures, and the resultant increase in high intensity rainfall events.”

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How USAID’s Upper Lempa Watershed Project Supports Transboundary Water Security and Resilience in Central America

The  USAID Upper Lempa Watershed Project , implemented by Winrock International, focuses on the headwaters of the Lempa River, one of the longest in Central America – and the largest river in El Salvador. The project engages government, communities, environmental groups and other stakeholders across El Salvador, Guatemala and Honduras to improve the health and resilience of the Upper Lempa Watershed, directly impacting the wellbeing and water security of approximately 180,000 people in the three countries. As World Water Day 2024 approaches, we asked Chief of Party Deisy Lopez and her El Salvador-based team how the Upper Lempa Watershed Project collaborates with partners to help communities and government of the three nations achieve their aims for this critical natural resource.

What are the main goals of the USAID Upper Lempa Watershed Project?

The main goal is to support improved water resource management in the watershed through enhanced water quality, quantity and reliability. To do that, we’re working with a wide range of partners to address water security risks linked to man-made, climate, and environmental factors in an area that covers approximately 260,000 hectares – equivalent to just over 641,000 acres ─ of the watershed. This is a biologically significant region that contains many important and protected ecosystems. To give a sense of the area this big watershed covers, it’s similar in size to Los Angeles, California.

The main activities will help to mitigate future water security risks by ensuring that national water authorities in each of the three countries – Guatemala, where the river’s headwaters are located; Honduras; and El Salvador, where the river empties into the Pacific ─ and transboundary institutions have the information and support they need to effectively, inclusively plan and make decisions to enhance water security in the river’s basin. Also ─ to reduce risks for the tens of thousands of downstream water users who depend on the Lempa River for economic prosperity, ecosystem services and their own wellbeing. The project also promotes productive economic activities that help reduce violence and gender discrimination. In addition to Winrock, project partners include  Plan Trifinio ,  Tetra Tech ARD , the  Stockholm Environment Institute , and the  Center for Water Security and Cooperation .

Why is the Upper Lempa River Watershed so important?

It’s the watershed of one of the longest rivers in Central America, and the river is also El Salvador’s largest and only navigable one. The northern valley has hydroelectric plants that supply power to most Salvadorans, and the southern basin is an important agricultural area, as it provides drinking water to 1.5 million Salvadorans at the metropolitan area. It’s also very beautiful: check out this USAID video to see some of it:

Despite its beauty, the Lempa River is at risk, for many reasons, including climate change, but also due to challenges with coordination amongst the jurisdictions and people who rely on it for drinking water, for irrigation for farms and livelihoods including aquaculture.

What are some of the project’s main strategies for improving water resources management?

We are working closely with our partners using a locally-led approach to strengthen regional, national, and local institutions, municipalities, and civil society organizations, including environmental and conservation-focused groups, in all three countries. These stakeholders already share common principles. They agree on the need to improve capacity and funding to empower their own institutions, citizens, CSOs and governments to efficiently, equitably protect water security and manage biodiversity. Ultimately, these measures aim to mitigate risks to water security, better protect human health, security and the economy, build prosperity and climate resilience, and preserve ecosystems and biodiversity. 

We have three key objectives: Fortifying capacity to monitor water and utilize data for informed decision-making; showcasing the practical application of  USAID’s Water Security Improvement process  to local partners with a focus on municipal applications; and conducting a comprehensive assessment of the financial landscape within water resource management to facilitate stakeholder access to vital resources. 

How’s it going, so far?

We are a five-year project and just finished our second year. We are making substantial strides in augmenting the health and resilience of the watershed, which encompasses the headwaters of the Lempa River. This work is pivotal in addressing the underlying causes of irregular migration, violence, and gender discrimination by sustaining economically productive activities and fostering adaptation to climate stressors. We use a combination of approaches, including exploring ways that new technology, data collection, analysis and sharing can help people across all three countries better protect the river, while simultaneously fostering intensive, community-led collaboration in planning and action.

Can you tell us three specific ways the project helps improve water security in the region?   

First, we are working with partners to strengthen local capacity to reduce the algae presence at the intake of the Torogoz Drinking Water Treatment Plant and to support the plant’s early water quality alert system. 

This is an important facility that treats drinking water for around 1.5 million Salvadorans. It is named after El Salvador’s national bird, the Torogoz, a symbol of freedom and the beauty of our natural environment. As in other freshwater bodies around the world, the algae proliferation problem in the Lempa River is exacerbated by climate change, in part because warmer temperatures encourage growth and distribution of algae in rivers and extends the growing season for algae, leading to longer blooms. Excessive nutrient runoff into the river is also a factor. To help government tackle this near the treatment plant,  USAID provided three ultrasonic buoys  to El Salvador’s National Administration of Aqueducts and Sewers (ANDA), which is responsible for providing water services in El Salvador. The buoy network reduces algae contamination in the river using ultrasound.

The buoys are floating platforms that use solar energy and ultrasound pulses to control microalgae in an area of up to 500 meters in diameter each, eliminating up to 90% of toxic microalgae and preventing their growth. They’re helping to combat excessive growth of microalgae, which affects the water’s quality – including its color, taste, odor and suitability for consumption. 

Introduction of this new technology is a major step toward improved water quality.

We also are supporting the development of new Municipal Water Security Plans in El Salvador, Guatemala and Honduras.  

The project recognizes the interplay between local governance and the wellbeing of the watershed. This approach embodies our commitment to establishing a direct and efficient avenue for improving water security. By focusing on municipal collaboration, the project aims to address the immediate needs of communities and foster a more resilient and sustainable water management system. 

In addition to controlling algae proliferation, they continuously monitor the water in the Lempa River. The data is reflected directly in real-time in our automated control center. This modern system will contribute to ensuring the water quality entering our drinking water treatment plant and improving the surveillance and early warning system for the Upper Lempa Watershed. ANDA President Rubén Alemán

Municipal Water Security Plans are part of this approach because they help to identify and address the current issues and state of water resources in municipalities along with their organizational management and governance while also addressing future challenges and building climate-resilient programming. The plans include activities and interventions to help municipalities achieve improved water security, which benefits citizens through more reliable water supply. We have prioritized communities that are the most vulnerable to water security risks, and work on these plans in close collaboration with municipal governments, water users and local organizations in all three countries.

The process we use ensures local ownership and leadership from the beginning, from generating interest and commitment to the planning process all the way to validation of the final plan. It involves carefully collecting information about each municipality’s current water management and use.

And third, we’re helping to boost local capacity to monitor water quality through hydrometric data collection.

In coordination with the Ministry of Environment and Natural Resources (MARN) of El Salvador,   the project is constructing and equipping six riverine hydrometric stations in the main tributaries of the Lempa River. These stations are the first of their kind to be used in the region. They collect and generate real-time rainfall, flow and water quality data on conductivity, temperature, pH, and dissolved oxygen, all of which are critical for informed water management decision making. Additionally, the project is providing measurement and monitoring equipment for determining ecological flows and laboratory equipment for water quality analysis.  

This data will help technicians at the Torogoz facility anticipate phenomena that affect water quality, enabling them to take preventive measures faster to protect the water supply and better preserve aquatic life. With more timely and consistent information, agencies and communities can develop new measures to improve water suitability for aquaculture and agriculture, benefiting communities that depend on aquatic resources.

This information will also be strengthened with environmental flow data developed by MARN, helping to protect the aquatic life of the territory. Data collection will be carried out with the new instruments provided by the project.

We now have all the necessary equipment to conduct the biodiversity studies needed to determine ecological flows. Guillermo Cornejo, a water resources specialist at MARN

This blog was originally published by Winrock International .

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For 13 consecutive months, global average air and ocean temperatures were probably the hottest they have been in human history.

This streak of extraordinary heat ended last month, the EU’s Copernicus Climate Change Service reported , as July 2024 was only the second hottest ever recorded – 0.04°C cooler than a record set the previous July.

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“Global warming has consistently toppled records for warm global average temperatures in recent decades, but breaking them by as much as a quarter of a degree for several months is not common,” says Christopher Merchant, a professor of ocean and Earth observation at the University of Reading.

Air temperatures peaked in December 2023, when the Earth was 1.78°C hotter than the pre-industrial average for that time of year. Buoy-based sensors confirmed that the ocean was also record-warm at the time.

So what caused this stretch of unusually high temperatures on land and at sea?

“Several factors came together,” Merchant says. “But the biggest and most important is climate change, largely caused by burning fossil fuels.”

Big Oil and the little boy

When scientists refer to Earth’s pre-industrial temperature, they typically mean a global average taken between 1850 and 1900. Factories and power plants still existed in the second half of the 19th century, especially in Europe and North America, but the vast majority of greenhouse gas emissions generated by human activity had yet to be emitted. What’s more, meteorologists have a fairly good temperature record for this period with which to compare modern warming.

What this comparison tells us is that July 2024 was 1.48°C warmer than a typical July before the mass burning of coal, oil and gas, Merchant says. Roughly 1.3°C of that is directly attributable to global heating caused by these fossil emissions and land-use changes (deforestation, livestock farming) over the intervening decades.

The remainder, which caused the sudden temperature spike beginning in June 2023 , was largely the result of a natural cycle in the climate known as El Niño.

Read more: Earth has just ended a 13-month streak of record heat – here's what to expect next

“An El Niño event is a reorganisation of the water across the vast reaches of the Pacific Ocean. El Niño is so important to the workings of worldwide weather as it increases the temperature of the air on average across all of Earth’s surface, not only over the Pacific,” Merchant explains.

El Niño has ended, and with it, the run of record global average temperatures. Merchant expects temperatures to ease back slightly, but says there is no going back to the pre-2023 norm.

“A plausible scenario is that global temperatures will fluctuate near the 1.4°C level for several years, until the next big El Niño event pushes the world above 1.5°C of warming, perhaps in the early 2030s,” he says.

Over? Shoot!

Since the 2015 Paris agreement, the political consensus on climate change has been to strive to limit warming to 1.5°C. A slew of catastrophic and potentially irreversible changes to the systems that keep Earth habitable are more likely to occur once this long-term average has been crossed.

Read more: What El Niño means for the world's perilous climate tipping points

It’s possible that this process has already started for one system in particular: tropical coral reefs . Earth’s largest, the Great Barrier Reef off Australia, has suffered five mass bleaching events in the past nine summers and recently endured its worst heat in at least 400 years.

Read more: 'Wake-up call to humanity': research shows the Great Barrier Reef is the hottest it's been in 400 years

The new plan, if one exists among the world’s governments ( approving new oil and gas production is still a normal feature of governing), would seem to accept the 1.5°C target being breached at least temporarily.

Read more: The world no longer needs new fossil fuels – and the UK could lead the way in making them taboo

“The question is, how do we manage this period of ‘overshoot’ and bring temperatures back down?” asks Jonathan Symons, a lecturer in international relations at Macquarie University.

In autumn last year, a commission mainly composed of former government ministers from several countries published a report on the implications of overshooting 1.5°C . The report argued that high-emitters like Australia should now aim for “net-negative emissions” and begin urgently removing carbon from the air – by restoring habitats and deploying carbon capture and storage technology.

Symons summed up their reservations with both:

“The commission worries many carbon removal approaches are phoney, impermanent or have adverse social and environmental impacts.”

One drastic option the Climate Overshoot Commission ruled out was “solar radiation management”: reflecting some of the Sun’s heat and light back to space by injecting reflective particles into the atmosphere, among other techniques. Academics continue to debate whether this is now an unpleasant necessity or more reckless vandalism of the atmosphere.

Read more: The disagreement between two climate scientists that will decide our future

In lieu of a radical change of course, present global climate policy could breach the 1.5°C target by a degree Celsius or more according to an analysis published in Nature Climate Change on Monday.

The world seems to be delaying the end of fossil fuels, gambling that nature will hold its breath. Research has so far condemned this wishful thinking: computer models predict “ waves of extinctions ” and ecological damage spanning centuries from even a brief sojourn at 2°C.

Read more: Climate crisis: even temporarily overshooting 2°C would cause permanent damage to Earth's species

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• Published: 05 August 2024

Climate change engagement of scientists

• Fabian Dablander   ORCID: orcid.org/0000-0003-2650-6491 1 , 2   na1 ,
• Maien S. M. Sachisthal   ORCID: orcid.org/0000-0002-9833-0723 3   na1 ,
• Viktoria Cologna   ORCID: orcid.org/0000-0003-3706-8669 4 , 5 ,
• Noel Strahm   ORCID: orcid.org/0000-0001-9837-8869 6 ,
• Anna Bosshard   ORCID: orcid.org/0000-0002-2095-1116 3 ,
• Nana-Maria Grüning   ORCID: orcid.org/0000-0002-1528-6625 7 ,
• Alison J. K. Green   ORCID: orcid.org/0000-0002-5216-0175 8 ,
• Cameron Brick   ORCID: orcid.org/0000-0002-7174-8193 3 , 9 ,
• Adam R. Aron 10 &
• Jonas M. B. Haslbeck   ORCID: orcid.org/0000-0001-9096-7837 11 , 12   na1  

Nature Climate Change ( 2024 ) Cite this article

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• Climate-change mitigation

Climate change is one of the biggest threats to humanity. Scientists are well positioned to help address it beyond conducting academic research, yet little is known about their wider engagement with the topic. We investigate scientists’ engagement with climate change using quantitative and qualitative analyses of a large-scale survey ( N  = 9,220) across 115 countries, all fields and all career stages. Many scientists already engage in individual lifestyle changes, but fewer engage in advocacy or activism. On the basis of our quantitative and qualitative results, we propose a two-step model of engagement to better understand why. Scientists must first overcome intellectual and practical barriers to be willing to engage, and then overcome additional barriers to actually engage. On the basis of this model, we provide concrete recommendations for increasing scientists’ engagement with climate change.

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Scientists’ identities shape engagement with environmental activism

Exposure to and learning from the IPCC special report on 1.5 °C global warming, and public support for climate protests and mitigation policies

Globally representative evidence on the actual and perceived support for climate action

Data availability.

We used the Scopus database 72 to identify scientists and academics who were subsequently invited to participate in the survey. The anonymized data used for analysis are available on Zenodo at https://doi.org/10.5281/zenodo.12187345 (ref. 74 ).

Code availability

The code and all materials are available on Zenodo at https://doi.org/10.5281/zenodo.12187345 (ref. 74 ). Together with the data (see above), these allow the reader to reproduce all analyses, results and figures reported in the paper.

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Acknowledgements

This work was supported by NWO gravitation grant number 024.004.016 (to J.H.), Swiss National Science Foundation Postdoc Mobility Fellowship P500PS_202935 (to V.C.), the Harvard University Faculty Development Funds (to V.C.) and the Studienstiftung des deutschen Volkes (PhD scholarship) (to A.B.). We thank G. Gallo from New Environments and D. Mackey for help with Fig. 3 , and T. Fossen, K. Nielsen, A. Urai and C. van Eck for their helpful comments on an earlier version of this paper.

Author information

These authors contributed equally: Fabian Dablander, Maien S. M. Sachisthal, Jonas M. B. Haslbeck.

Authors and Affiliations

Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Amsterdam, the Netherlands

Fabian Dablander

Institute for Advanced Study, University of Amsterdam, Amsterdam, the Netherlands

Department of Psychology, University of Amsterdam, Amsterdam, the Netherlands

Maien S. M. Sachisthal, Anna Bosshard & Cameron Brick

Department of Communication and Media Research, University of Zürich, Zürich, Switzerland

Viktoria Cologna

Weather and Climate Risk Group, ETH Zürich, Zürich, Switzerland

Institute of Sociology, University of Bern, Bern, Switzerland

Noel Strahm

Institute of Biochemistry, Charite Universitätsmedizin Berlin, Berlin, Germany

Nana-Maria Grüning

Scientists’ Warning Foundation, Richmond, CA, USA

Alison J. K. Green

Department of Psychology, Inland Norway University of Applied Sciences, Elverum, Norway

Cameron Brick

Department of Psychology, University of California San Diego, La Jolla, CA, USA

Adam R. Aron

Department of Clinical Psychological Science, Maastricht University, Maastricht, the Netherlands

Jonas M. B. Haslbeck

Department of Psychological Methods, University of Amsterdam, Amsterdam, the Netherlands

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Contributions

F.D. conceived the initial idea of the study and F.D., M.S.M.S., J.M.B.H., V.C., N.-M.G., C.B., A.J.K.G. and A.R.A. contributed to its conceptualization. F.D., M.S.M.S., J.M.B.H., N.S., N.M.G., A.B. and A.R.A. contributed to the formal analysis of the quantitative and/or qualitative data. F.D., M.S.M.S., J.M.B.H. and N.S. contributed to the methodology of the study, the data collection strategy, software used for the study administration and/or analysis. F.D., N.S., M.S.M.S., A.R.A. and A.B. contributed to the validation of the study results. F.D. and J.M.B.H. performed data visualization. F.D., M.S.M.S. and J.M.B.H. curated the data, administered the project and wrote the original draft. F.D., M.S.M.S., J.M.B.H., V.C., C.B., A.J.K.G. and A.R.A. reviewed and edited the original draft.

Corresponding author

Correspondence to Fabian Dablander .

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The authors declare the existence of a non-financial competing interest. All authors have engaged in climate change advocacy or activism.

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Extended data

Extended data fig. 1 number of observations per country in our data set..

Please note that Hong Kong (n = 32) is not included as a separate country on this map, but is modelled as a separate country in all other analyses that include country as a variable.

Extended Data Fig. 2 Distribution of Scopus and our sample on key variables.

The dashed lines indicate the median of the respective distributions.

Supplementary information

Supplementary information.

Supplementary Text, Figs. 1–8 and Tables 1–9.

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Dablander, F., Sachisthal, M.S.M., Cologna, V. et al. Climate change engagement of scientists. Nat. Clim. Chang. (2024). https://doi.org/10.1038/s41558-024-02091-2

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In the face of global warming, students are dreaming up a better climate future

Lee V. Gaines

Bloomington High School South science teacher Kirstin Milks leads a lesson on human-caused climate change and technologies that could help reduce greenhouse gas emissions. Chris Elberfeld/WFYI hide caption

High school freshman DeWayne Murphy has a big idea for a new green technology.

“There's going to be a tank and it should be like a big giant metal tank,” he explains to climate scientist Ben Kravitz on a school day in May. “You fill it up with water, and the tank is going to heat up.”

The water will turn to steam, which will power a car. But it has some potential drawbacks.

Startups want to cool Earth by reflecting sunlight. There are few rules and big risks

“It's not really designed to take any damage, like at all, so you have to be like really gentle with it,” Murphy says.

“What I really like about that is steam’s kind of an old tech,” Kravitz tells him. “Steam works. We know that. So, yeah, that's a really cool idea.”

This conversation is part of a larger lesson about developing technologies that reduce planet-heating pollution. The lesson was created by Kravitz, an assistant professor of earth and atmospheric sciences at Indiana University; his colleague Paul Goddard; and Kirstin Milks, DeWayne Murphy’s science teacher at Bloomington High School South in Bloomington, Ind.

With heat waves and extreme weather becoming more and more common, Milks wants to empower her students with information and the creative freedom to dream up big ideas for a better climate future.

“The fact is that climate change is the story of these young people's lives,” Milks says. “Our students need to know not just the stuff about it that is challenging and difficult, the stuff we hear about in the news, but also they need to see how change can happen. They need to feel like they understand and can actually make a difference in our shared future.”

Milks teaches her students the basic facts about human-caused climate change: that burning fossil fuels — like coal, oil and gas — is the biggest single driver of increased carbon dioxide in the atmosphere. Carbon dioxide heats the planet, which has led to more frequent droughts, hurricanes, floods and intense heat waves.

This oil company invests in pulling CO2 out of the sky — so it can keep selling crude

Kravitz says, “The only permanent solution to stopping that is reducing our greenhouse gas emissions.”

Scientists already know some technologies that could help. Solar and wind energy combined with big batteries are helping the world transition away from oil, coal and gas.

But Kravitz says the world isn’t moving fast enough. So he and other scientists are studying strategies to temporarily alter the Earth’s climate to reduce the effects of climate change. It’s known as climate engineering, or geoengineering .

Climate engineering covers a range of strategies, including reflecting sunlight back into space and removing carbon dioxide from the atmosphere . But these strategies can also pose significant risks — like disruptions to rain patterns and impacts on global crops. Meanwhile, there’s still little regulation over how these technologies might get used.

“The people who are going to be voting on whether to [pursue climate engineering], or even leading the charge, are sitting in high school classrooms right now,” Kravitz says. “So if they don’t know what this topic is, that’s a real problem. So that’s why we developed the lesson.”

Milks says she isn’t trying to persuade students to embrace climate engineering — rather, she wants to give them the knowledge they need to make informed decisions about it, if and when the time comes.

Students think up wild ideas, like covering the desert in glitter

Creativity is at the core of this lesson, Milks explains. After students learn the basics of climate engineering, they’re asked to “come up with interesting wild ideas” to slow global warming.

High school freshman DeWayne Murphy consults with Milks, his science teacher, on a classroom experiment. Chris Elberfeld/WFYI hide caption

At first, no idea is too out there, says Goddard, an assistant research scientist at Indiana University who helped develop the lesson.

'It could just sweep us away': This school is on the front lines of climate change

“As we progress along throughout the lessons, then we add more details, more constraints to their designs,” Goddard says.

In the first round of brainstorming, students imagined a solar-powered helicopter; artificial trees that store rainwater to help fight wildfires; and lots of ways to reflect light back into the atmosphere, like covering the desert in shiny glitter.

Next, students are asked to consider the potential limitations and risks to their ideas. Take glitter in the desert, for example:

“How are we going to make sure that the glitter doesn't get eaten by the rock pocket mouse … or like snakes and stuff?” Milks asks.

The student suggests making the glitter large and smooth enough so it won’t be eaten by animals or otherwise harm them.

For their final assignment, students present their concepts — including their anticipated benefits and risks — to Kravitz, Goddard and other scientists.

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High school junior Campbell Brown has an idea for a flying air filter that sucks carbon dioxide out of the atmosphere and turns it into a harmless byproduct.

“It'll decrease the amount of greenhouse gases that are in the air,” she explains during her presentation. “The risks could be that it just doesn't work the way I want it to.”

Kravitz is impressed.

“So you want to know something? It does work,” he tells Brown. “The waste product that you get out of it is baking soda, essentially. So yeah, it works, it just can't be widely deployed right now because it's too expensive.”

Fostering climate optimism

Brown is thrilled that her idea is something scientists are currently studying, especially because she didn’t know much about climate change before this lesson.

Ben Kravitz, an assistant professor of earth and atmospheric sciences at Indiana University, chats with high school students DeWayne Murphy and Emerald Yee during a class at Bloomington High School South. Chris Elberfeld/WFYI hide caption

She was saddened to learn how humans have contributed to climate change and its effects on the planet, but she says she’s leaving this lesson with a newfound sense of hope.

“Because rather than the old generation leaving something broken for us to fix, we're also getting help from that generation. And so that way, we're all helping each other out and fixing what we have caused,” she says.

New Jersey requires climate change education. A year in, here's how it's going

Emerald Yee, a senior in Milks’ class, has been concerned about climate change for a while. She has a family member with a chronic health condition that’s exacerbated by heat.

“So for me, I’m mainly just worried about [their] safety when it comes to climate change and global warming,” Yee says. She says this lesson gave her the tools to “really think about climate change and how we can change it and make it better for not just our generation, but the younger generations, our younger siblings, or even our kids and grandkids.”

For Kravitz, fostering climate optimism is a big part of this lesson. And he says hearing students’ ideas for solutions always makes him feel better.

“The neat thing about seeing all of these ideas come out of the classroom is it's not I can't do it . It's we can do it . Humans, when they get together, can do amazing things. And that's what gives me hope.”

• climate change and kids