Climate change health risks are accelerating worldwide, with extreme heat contributing to an estimated 710,000 deaths in 2023, according to a major international health assessment. Researchers warn that rising temperatures, worsening droughts, and climate-related economic losses are threatening human health faster than governments are responding.
The findings come from the 2026 Lancet Countdown on Health and Climate Change, released October 28. The report calls for climate change to be recognized as a global health emergency, arguing that its consequences now extend far beyond environmental damage. The assessment also identifies measurable health benefits from clean energy investments and stronger public health systems.
Climate Change Health Risks Are Growing Faster Than Global Action
The 2026 Lancet Countdown report brings together research from 146 experts across 71 collaborating institutions. It examines 54 indicators covering environmental hazards, health outcomes, economic consequences, and government responses.
The assessment marks a decade of monitoring the relationship between climate change and public health. Its central finding is that several health threats are worsening at an accelerating rate, despite progress in some areas of climate policy.
Researchers compared conditions following the Paris Agreement with those recorded during the preceding decade. They found that annual average heat-related mortality increased by nearly 36% after the agreement entered into force.
Marina Romanello, executive director of the Lancet Countdown at University College London, warned that growing health threats are outpacing international efforts to address them. The report’s authors are urging governments to treat climate policy as a public health priority rather than solely an environmental issue.
Extreme Heat Linked to 710,000 Deaths in 2023
The report’s most troubling finding concerns the global death toll associated with high temperatures. Researchers estimate that heat contributed to 710,000 deaths worldwide in 2023, the latest year covered by the mortality analysis.
Approximately 71.5% of those deaths were attributable to human-caused climate change. That represents an estimated 508,000 deaths associated with the additional warming caused by human activity.
The distinction is important. The report does not claim that every heat-related death resulted from climate change. Instead, researchers used attribution methods to estimate how much the changing climate increased mortality beyond what would otherwise have occurred.
The assessment also found that heat was associated with more than 540,000 deaths annually, on average, between 2016 and 2023. Researchers attributed approximately 68% of that burden to climate change.
Across the eight years, the report estimates that nearly 3 million heat-related deaths were attributable to human-caused warming.
Heat exposure can worsen cardiovascular disease, contribute to kidney injuries, and increase the risk of heat stroke. Older adults, people with existing medical conditions, and outdoor workers face particular risks.
The Lancet Countdown’s mortality data provides more detail on regional differences and the methods used to estimate these deaths.
Droughts and Extreme Weather Are Threatening Health
The report identifies worsening drought conditions as another major public health concern. In 2025, approximately 51.8% of the world’s land area experienced extreme drought conditions for at least one month.
Researchers found that the area affected by extreme drought has been expanding much faster than in the previous decade. The findings raise concerns about water availability, food production, and community health.
Drought can undermine agricultural production and increase pressure on food supplies. Its effects are particularly serious in regions where communities depend heavily on local farming and have limited access to alternative water sources.
Climate-related flooding and heavy rainfall also create health risks. Contaminated water, damaged infrastructure, interrupted medical services, and displacement can worsen the consequences of extreme weather.
The report also examines how changes in temperature and rainfall affect conditions for infectious disease transmission. Environmental suitability for dengue transmission has increased over recent decades, although actual disease outbreaks also depend on mosquito populations, public health measures, and human behavior.
These findings show why climate-related health risks cannot be measured through temperature alone. Changes in weather patterns can influence multiple systems that communities rely on for survival.
Extreme Heat Caused More Than $1 Trillion in Income Losses
The economic effects of rising temperatures are becoming increasingly visible. According to the Lancet Countdown, heat exposure caused an estimated loss of 573 billion potential working hours worldwide in 2025.
Researchers calculated that the resulting reduction in labor capacity represented approximately $1.07 trillion in lost potential income.
These estimates reflect economic activity that could not be completed because of heat exposure. They should not be interpreted as direct government spending or documented financial losses for every affected business.
Outdoor workers are particularly vulnerable because prolonged exposure can make physical labor unsafe. Agriculture, construction, and other labor-intensive industries face significant risks as temperatures rise.
The economic burden also falls unevenly across countries. Lower-income populations often have fewer resources to adapt working conditions, install cooling equipment, or recover from interrupted income.
Researchers warn that reduced earning capacity can contribute to additional health problems. Lower household income may limit access to nutritious food, adequate housing, and essential medical services.
Why Researchers Are Calling It a Global Health Emergency
The Lancet Countdown’s authors are calling for climate change to be recognized and addressed as a global health emergency. Their recommendation reflects the growing evidence of mortality, illness, economic disruption, and environmental hazards.
However, the recommendation is not equivalent to a formal emergency declaration by the World Health Organization.
In its October 28 statement, WHO described climate change as a growing health emergency and highlighted the report’s findings. The organization emphasized the need to strengthen health systems and reduce exposure to climate-related hazards.
The distinction matters because formal international public health emergency declarations involve specific institutional procedures. The Lancet Countdown is making a policy recommendation supported by its scientific assessment.
The researchers argue that governments should respond to climate change with the urgency normally associated with major threats to human health. They also call for greater investment in preventive measures and health-focused adaptation.
Clean Energy and Health Systems Are Delivering Benefits
Despite the worsening indicators, the report identifies evidence that climate action can improve public health. Global investment in clean energy reached approximately $2.1 trillion in 2025, according to the assessment.
Reducing fossil fuel combustion can also lower air pollution. The report estimates that countries that reduce fossil fuel-related pollution prevent thousands of premature deaths each year.
These benefits arise because cleaner air reduces exposure to pollutants associated with respiratory and cardiovascular disease. The health gains can begin before the longer-term effects of reduced greenhouse gas emissions become apparent.
Health systems are also adopting measures to address climate-related emergencies. The report points to progress in national health adaptation plans and early warning systems that incorporate climate information.
Heat alerts, public cooling facilities, and emergency response planning can help communities prepare for dangerous temperatures. Similar approaches can support responses to floods, droughts, and other weather-related threats.
However, access to these protections remains uneven. Lower-income communities may lack the infrastructure and funding needed to implement effective adaptation measures.
What the 2026 Lancet Report Means for Global Health
The report presents climate change as an immediate health concern rather than a distant environmental threat. Its findings show that extreme heat, drought, and other climate-related hazards already affect mortality, livelihoods, and healthcare needs.
The 710,000 estimated heat-related deaths in 2023 illustrate the scale of the problem. The attribution analysis also indicates that human-caused warming was responsible for a substantial share of that burden.
Yet the assessment does not conclude that the health outlook is beyond improvement. Cleaner energy, better early warning systems, and stronger healthcare infrastructure are already delivering measurable benefits.
Researchers are calling for faster action ahead of the next round of international climate negotiations. They want governments to incorporate health outcomes more directly into climate policies and investment decisions.
The challenge is that progress in some areas has not kept pace with the accelerating risks. The 2026 Lancet Countdown concludes that protecting public health will require both deeper reductions in greenhouse gas emissions and stronger measures to help communities adapt.
