New research from the Lancet Countdown and World Health Organization reveals how rising temperatures, extreme weather and environmental changes are threatening human health worldwide.
Key Takeaways
- Heat was associated with an estimated 710,000 deaths worldwide in 2023, with more than 70 percent attributable to human-caused climate change.
- Average annual heat-related deaths have increased nearly 36 percent compared with the decade before the Paris Agreement.
- Drought, infectious diseases and extreme weather are creating additional health risks.
- Clean energy investments and stronger healthcare systems are delivering measurable benefits, although progress remains too slow.
- Researchers are calling for climate change to be formally recognized as a global health emergency.
How Dangerous Is Climate Change for Human Health?
When we think about climate change, images of melting glaciers, devastating wildfires and rising seas often come to mind. Increasingly, however, scientists are drawing attention to the growing connection between climate change and human health.
According to the 2026 Lancet Countdown on Health and Climate Change, developed in collaboration with the World Health Organization (WHO), heat was associated with approximately 710,000 deaths worldwide in 2023. Researchers estimate that more than 70 percent were attributable to human-caused climate change.
The report, involving 146 researchers and tracking 54 indicators, found that average annual heat-related deaths have increased nearly 36 percent compared with the decade preceding the Paris Agreement.
These findings have prompted researchers to call for climate change to be formally recognized as a global health emergency.
The Growing Health Risks of a Warming Planet
Extreme heat is only one of the ways climate change threatens human health. The report found that approximately 52 percent of the world’s land experienced extreme drought for at least one month in 2025, threatening water supplies, agriculture and food security.
Changing temperatures and rainfall patterns are also creating more favorable conditions for infectious diseases such as dengue, while extreme weather events can disrupt healthcare services and leave vulnerable populations without access to essential treatment.
The economic consequences are substantial. Heat exposure resulted in an estimated 573 billion potential working hours lost worldwide in 2025, representing approximately $1.07 trillion in lost income.
These pressures are particularly challenging for communities with limited healthcare resources and workers who spend long hours outdoors.
When Climate Disasters Become Health Disasters
The relationship between climate change and human health becomes particularly concerning when extreme weather disrupts essential services. Extreme heat can overwhelm hospitals and electricity grids, while flooding and storms can interrupt medical care, contaminate drinking water and displace entire communities.
Earlier this month, Voices.Earth explored whether humanity is prepared for climate change’s “Big One,” an extraordinary weather event capable of overwhelming infrastructure and emergency response systems.
The latest Lancet Countdown findings add urgency to that discussion by showing how climate-related health emergencies are already unfolding. Extreme heat can overwhelm hospitals and electricity grids, while flooding and storms can interrupt medical care, contaminate drinking water and displace entire communities.
Our recent article on Earth’s sixth mass extinction examined another dimension of this challenge, including how biodiversity loss threatens food supplies, water quality and the ecosystems supporting human health.
Together, these findings illustrate how environmental changes can create interconnected risks for communities worldwide.
Can Climate Action Improve Human Health?
The Lancet Countdown also offers encouraging evidence that climate action is producing measurable health benefits. Global clean energy investment reached a record $2.1 trillion in 2025. In 70 countries where fossil fuel-related air pollution has declined, cleaner air is estimated to be preventing approximately 323,000 premature deaths annually.
Healthcare systems are also beginning to adapt. According to the report, 56 WHO member states now have national plans to address climate-related health risks, compared with just 14 in 2015.
These improvements demonstrate the value of reducing emissions, strengthening healthcare infrastructure and expanding early warning systems, even as researchers warn that the response remains insufficient.
One Planet. One Domain.
Climate change is increasingly affecting the conditions that allow people and communities to remain healthy. The latest research reinforces the importance of treating environmental protection as an investment in human well-being.
Now is the time to fight back in the name of Earth. By joining the .earth domain tribe, individuals, organizations and businesses can become part of a global community working to protect our planet and create a healthier, more sustainable future.
To learn more and get started, visit Voices.Earth, and check out the latest Voices.Earth podcast series for inspiring stories from our community.
