The 2021 Report

People in every region of the world are increasingly seeing their health affected by climate change. Key trends seen in previous Lancet Countdown Reports are getting worse and exacerbating already existing health and social inequities–the 2021 report gives a code red for health.

Our 2021 Report tracks the relationship between health and climate change across five key domains and over 40 indicators.

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Key message

Every region of the world is affected by climate change and its health impacts are getting worse. We are seeing more frequent and more intense extremes of heat harming people’s health in rich and poor countries; 72% of countries saw an increase in human exposure to wildfires; the environmental suitability for the transmission of diseases like dengue, malaria and cholera is increasing around the world; and in 2020, up to 19% of the global land surface was affected by extreme drought in any given month – putting people in danger of food and water insecurity. Compounded with insufficient adaptation measures, the most vulnerable people are the worst affected, and climate change is already exacerbating inequities.

Key message

With current commitments putting the world on track to 2.4°C of warming, the cost of inaction on climate and health will vastly outweigh the costs of acting now. Rapid decarbonisation could prevent most of the 3.3 million deaths from air pollution that occur each year, the 842,000 deaths associated with excessive red meat consumption, and result in better physical and mental health from higher exposure to nature and more physical activity.

Key message

The COVID-19 pandemic has demonstrated the need for increased international co-operation in the face of global crises. COVID-19 recovery presents an unprecedented opportunity to invest in a future of economic and environmental sustainability, improved health and reduced inequities. However, this will only be possible if the world acts together to ensure that no person is left behind. Decision-makers must act today and show strong leadership. A better future is still possible.

Explore key findings of this year’s report

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Health Hazards, Exposures, and Impacts

Climate Change Impacts, Exposure and Vulnerability

A changing climate has profound implications for human health, with more frequent heatwaves and extreme weather events, changing patterns of infectious disease, and the exacerbation of existing health challenges around the world. Indicators in this section track how these impact on human health.

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Adaptation, Planning, and Resilience for Health

Adaptation, Planning, and Resilience for Health

Indicators in this section track how communities, health systems, and governments are understanding the health risks of climate change, the strategies and resources they are deploying, and how adaptation and resilience measures are being implemented globally.

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Mitigation Actions and Health Co-Benefits


Tackling climate change could be the greatest global health opportunity of the 21st century. Many of the interventions required to mitigate and adapt bring enormous benefits for human health and wellbeing in the form of cleaner air, healthier diets, and more liveable cities. Indicators in this section track the world’s efforts to mitigate climate change, and the health benefits of this response.

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Economics and Finance

Economics and Finance

The data here works to track the financial and economic dimensions of the effects of climate change, and of mitigation efforts required to respond to these changes. Indicators here monitor the economic costs of climate change and its drivers, as well as the investments and economic tools being deployed to transition to a low-carbon economy.

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Public and Political Engagement in Health and Climate Change

Public and Political Engagement in Health and Climate Change

Public and political engagement underpins the foundations of the world’s collective response to climate change, with reductions in global emissions at the speed required by the Paris Agreement depending on engagement from all sectors of society. The indicators in this section track the links between health and climate change in the media, national governments, the corporate sector, and the broader public.

  • Icon_1_Green Created with Sketch. Health Hazards, Exposures, and Impacts
    • 1.1.5 Heat-Related Mortality

      In 2018-2022, people experienced on average 86 days of health-threatening high temperatures annually. 60% of such temperatures were made more than twice as likely to occur by human-caused climate change.

    • 1.3.1 Dengue

      The transmission potential for dengue by Aedes aegypti and albopictus increased by 42.7% and 39.5%, respectively.

    • 1.4 Food Security and Undernutrition

      The higher frequency of heatwave days and drought months in 2021 compared to 1981–2010, is associated with 127 million more people experiencing moderate or severe food insecurity.

  • Icons Final_Green-03 Created with Sketch. Adaptation, Planning, and Resilience for Health
    • 2.1.3 City-Level Climate Change Risk Assessments

      In 2022, 94% of cities (848/898) reported they had completed or were undertaking a city-level climate change risk assessment, up from 713 in 2021.

    • 2.2.2 Air Conditioning: Benefits and Harms

      In 2021, air-conditioning provided cooling in a third of households but consumed about 1900 terawatt hours (TWh) of electricity (approximately the total electricity consumption of India and Brazil combined).

    • 2.3.1 Vulnerability to Mosquito-borne Disease

      Low HDI countries experienced a 37% decrease in vulnerability to Aedes-borne disease between 1990 and 2021, partly due to improvements in access to healthcare.

  • Icons Final_Green_v2-03 Created with Sketch. Mitigation Actions and Health Co-Benefits
    • 3.2.1 Mortality from Ambient Air Pollution

      Global deaths attributable to fossil fuel-derived PM2.5 decreased from 1.4 million in 2005 to 1.2 million in 2020. Reduced coal pollution contributed to about 80% of the decrease.

    • 3.2.2 Household Air Pollution

      The use of polluting fuels resulted in 140 deaths per 100,000 associated with household air pollution in 2020 in 62 countries reviewed, 56% of which was due to the use of solid fuels.

    • 3.3.2 Diet and Health Co-Benefits

      In 2020, 7.8 million deaths were associated with insufficient consumption of nutritious plant-based foods, and 1.9 million to excessive consumption of dairy, red and processed meat.

  • Icons Final_Green_v2-05 Created with Sketch. Economics and Finance
    • 4.1.1 Economic Losses due to Weather-related Extreme Events

      Global economic losses due to weather-related extreme events were US$264 billion in 2022. While 57.1% of losses in very high HDI countries were insured, 92.8% of losses in other countries were uninsured.

    • 4.2.6 Compatibility of Fossil Fuel Company Strategies With the Paris Agreement

      The strategies of the 20 largest oil and gas companies as of February 2023 would lead to production exceeding levels consistent with 1.5°C of heating by 173% in 2040, an increase from 112% expected as from February 2022.

    • 4.2.7 Fossil Fuel and Green Bank Lending

      Green sector lending has risen sharply since 2016, to US$498 billion in 2021, and is approaching fossil fuel lending. However, 22 of the top 40 private banks have increased their fossil fuel lending.

  • Icons Final_Green_v2-06 Created with Sketch. Public and Political Engagement in Health and Climate Change
    • 5.3.2 Scientific Engagement on the Health Impacts of Climate Change

      There are global inequalities in the location of studies referring to the health impacts of human-influenced climate drivers: 6.89 studies per million people in very high HDI countries, and 1.61 and 1.51, respectively, for medium and low HDI countries. Of 37 extreme events analysed for detection and attribution between 2022 and 2023, 31 (84%) were more likely and/or more severe because of climate change.

    • 5.4.2 Engagement by International Organisations

      Tweets mentioning the health co-benefits of climate change action reached a record of 22% of all monthly tweets from International Organisations in November 2022, in a continuously upward trend.

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