10 of 15 indicators monitoring health hazards, exposures and impacts have reached record levels, according to the latest Lancet Countdown on Health and Climate Change report. These impacts disproportionately fall on the 745 million people who lack access to electricity and have contributed the least to climate change. Record fossil fuel subsidies, production, and increasing global energy demand are pushing emissions to levels that will further endanger human health.
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“The 2024 report reveals the most concerning findings yet in 8 years of monitoring” – 2024 Lancet Countdown on Health and Climate Change
The Lancet Countdown on Health and Climate Change is produced each year since 2015 by a collaboration of 300 researchers and health professionals from UN agencies and global academic institutions. The central aim of the report is to evaluate the connections between climate change and health at global, regional, and national levels. The most recent report, published in October 2024, analyzes linkages between climate change and health across 56 indicators.
Key Climate Change and Health Indicators
Heat
Extreme heat is becoming more prevalent and dangerous to human health. Between 2019 and 2023, people were exposed to 46 additional days on average of health-threatening heat than would have been expected without climate change. The report defines “health-threatening” as temperatures above the 84th percentile of the 1986-2005 daily average.
Heat exposure is far more prevalent in developing countries, with many experiencing at least 100 or more days of health-threatening heat than without climate change.
Increased heat due to climate change is especially dangerous for older adults, who are more likely to have an underlying health condition and less able to protect themselves during a heat event. Heat-related deaths in adults older than 65 was 167% higher in 2023 than in 1990-1999 and there was a 106% increase in the average annual heat-related deaths in this age group between 1990-1999 and 2014-2023, according to the report.
Wildfires
The catastrophic, ongoing wildfires in the Los Angeles area have caused 24 deaths and destroyed more than 12,000 structures as of this writing. This is the latest example of an overall global increase in wildfire frequency and severity. The risk of wildfires and human exposure to very high fire danger increased in 124 countries between 2003-2007 and 2019-2023 due to higher temperatures and more frequent droughts.
Wildfire smoke contains several pollutants including particulate matter 2.5 (PM2.5) that are a significant threat to human health, including exacerbating respiratory illnesses and reducing lung and cardiovascular function. Research has also found that even short-term exposure to wildfire-related PM2.5 is associated with an increased risk of mortality.
Air pollution
Toxic air pollution is a global human health hazard. The burning of fossil fuels releases pollutants such as PM2.5 and contributes to related climate changes including drought and wildfire. Drier conditions increase the likelihood of sand and dust storms that contain the air pollutant PM10.
Between 2018 and 2022, 3.8 billion people were exposed to unsafe concentrations of PM10, which was a 31% increase from 2003-07, the report found.
Exposure to fossil fuel derived PM2.5 contributed to 2.09 million of 6.4 million total deaths attributable to PM2.5 in 2021. Although fossil fuels accounted for over 30% of PM2.5 mortality, this actually reflects a reduction of 156,000 fossil fuel related pollution deaths since 2016. This is due to decreased coal-related pollution in high and very high human development index (HDI) countries, underlining the tangible health benefits from decarbonization.
Extreme weather accelerating global food insecurity
Extreme heat and drought are causing millions more people to experience food insecurity. Nearly 50% of the global land area was affected by one or more months of extreme drought in 2023. The reduction in crop yields, water, and disrupted supply chains contributed to 151 million more people experiencing food insecurity in 2022 due to climate change.
Infectious disease
Warming temperatures, extreme precipitation and flooding are creating more favorable conditions for disease-carrying insects worldwide.
Mosquito-borne diseases are responsible for more than one million deaths and 700 million infections per year. Warmer temperatures accelerate mosquito development and lengthen disease transmission seasons by a month or more. The climatic suitability for transmission of dengue fever by two species of mosquito, Aedes albopictus and Aedes aegypti – also known as Asian tiger mosquito and yellow fever mosquito – increased by 46.3% and 10.7%, respectively, between 1951-60 and 2014-23. An additional 17.1% of global land area became suitable for transmission of malaria between 1951-60 and 2014-23.
More on the topic: What Are Zoonotic Diseases?
The Growing Carbon Footprint of Healthcare
A paradox of modern healthcare is that treatment of diseases, many of which are exacerbated by climate change, generates significant greenhouse gas emissions and contributes to climate change.
The global healthcare sector accounts for 4.6% of total emissions, according to the report. Emissions increased 36% between 2016 and 2021. Air pollution from healthcare emissions contributed to 4.6 million disability-adjusted life years lost in 2021.
Healthcare emissions are categorized across three scopes based on their source:
- Scope 1: direct emissions from healthcare facilities operations
- Scope 2: indirect emissions from purchased electricity, steam, cooling and heating
- Scope 3: emissions from the healthcare supply chain – production, transport, use and disposal of goods and services
The Lancet report found that there is an association between healthcare emissions and higher life expectancy up to 400 kilograms of carbon dioxide equivalent (CO2e) per capita. Additional emissions beyond this level are not linked to better health outcomes. Several very high HDI countries are over 1,000 kg CO2e, with the US leading industrialized countries at over 1,600 kg CO2e. This finding highlights that healthcare in high-emitting countries could decarbonize and still achieve high-quality care and outcomes.
UK National Health Service: A Global Model For Healthcare Decarbonization
The UK’s National Health Service (NHS) has initiated the most comprehensive national approach to healthcare decarbonization in the world. In 2022, it became the first national health system to embed a net zero commitment in legislation, with a roadmap for reaching this goal across its total carbon footprint by 2045.
Key rationales for the net zero target were the potential for diverse health benefits, improved air pollution in vulnerable and marginalized communities, and reduced environmental health inequities that disproportionately impact minority ethnic groups.
Emission reduction strategies are being deployed across all three emission scopes. Examples include improving NHS facility energy efficiency, installation of renewable energy infrastructure, facilitating reduced staff and patient travel, reducing single-use plastics, devices and disposable products, incentivizing supplier decarbonization and shifting to low carbon intensity anaesthetic gases and inhalers.
Decarbonizing transportation is another key focus. The NHS is in the process of transitioning its fleet of 20,000 vehicles to zero emission models. This applies to all new vehicles starting in 2027, ambulances in 2030 with full fleet transition by 2040.
The NHS estimates these strategies will yield substantial health benefits: 5,770 lives saved per year from reductions in air pollution and 38,400 lives saved per year from increased levels of physical activity by 2040.
Outlook
The world has a 99.7% probability of exceeding the 1.5C Paris Agreement limit, and global warming could reach 3.1C by 2100. This is due to insufficient decarbonization commitments from nearly all high emitting countries, growing energy demand and record fossil fuel subsidies. The anticipated withdrawal of the US from the Paris Climate Agreement under the incoming Trump Administration may further slow global momentum on climate change.
Global engagement around climate change and health may also be falling overall. The Lancet report highlighted that the number of governments mentioning climate and health in their annual UN General Debate fell from 50% in 2022 to 35% in 2023. Additionally, only 47% of the 58 Nationally Determined Contributions (NDCs) submitted in 2023 referred to health. NDCs are national climate actions plans each signatory to the Paris Agreement is required to submit regularly.
Health impacts and death from climate change are likely to continue escalating if the world maintains a high emission and warming trajectory. A November 2024 study projected that climate change and air pollution could contribute to 30 million deaths annually by 2100.
The health impacts of climate change are projected to disproportionately impact poor countries with the smallest carbon footprints. As Our World in Data’s Hannah Ritchie puts it, “this is the harsh inequality of climate change.”
You might also like: Why We Should Care About Environmental Health
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