1371. Lancet Countdown 2025 

Climate change is increasingly destabilizing the Earth's systems and environmental conditions that support human survival. The Lancet Countdown on Health and Climate Change's 2025 report warned that health threats from climate change are reaching unprecedented levels. 

From 2020 to 2024, an average of 16 of the 19 life-threatening heatwave days per year (84%) were estimated to not occur without climate change. Rising temperatures and growing vulnerable populations have led to a 63% increase in heatstroke deaths since the 1990s, with an estimated average of 546,000 per year between 2012 and 2021. Heat exposure's impact on individuals' outdoor work and exercise capacity, as well as on sleep quality, is also reaching concerning levels, impacting physical and mental health. 

The incidence of extreme precipitation days, which can impact health and cause flash floods and landslides, increased across 64% of the world's land area between 1961–1990 and 2015–2024. Meanwhile, 61% of the world's land area is expected to be affected by record drought in 2024, which is 299% higher than the 1950s average. These extreme heat, precipitation, and drought events can further threaten food security by affecting crop productivity, disrupting supply chains, reducing agricultural workers' capacity, and impacting incomes. Indeed, the number of heatwave days and drought months in 2023 was higher compared to 1981–2010, associated with an increase of 123.7 million people experiencing moderate or severe food insecurity across the 124 countries analyzed. Furthermore, rising temperatures and drier conditions are increasing the risk of wildfires, with air pollution from fine particulate matter (PM2.5) caused by wildfire smoke resulting in a record 154,000 deaths in 2024. 

Climate change is also affecting the risk of transmission of deadly infectious diseases. The likelihood of climate-driven transmission of dengue fever by Aedes albopictus and Aedes aegypti mosquitoes increased by 48.5% and 11.6% between 1951–1960 and 2015–2024, respectively, contributing at least partially to the 7.6 million dengue cases reported globally in early 2024. 

The diverse health impacts of climate change are straining economies, reducing labor productivity, increasing worker absenteeism, and straining healthcare systems, ultimately affecting the socioeconomic conditions that support health and well-being. Lost work hours due to heat exposure in 2024 could potentially cost US$1.09 trillion, and global economic losses from extreme weather in 2024 are projected at US$304 billion, a 58.9% increase from the 2010–2014 annual average. These losses are increasingly straining healthcare systems that are increasingly unable to absorb climate-related damages. Insurance coverage for rising extreme weather-related losses fell from 67% in 2010–2014 to 54% in 2020–2024. As a result, losses increasingly fall on public systems and individuals, affecting health and socioeconomic well-being, reducing the capacity to respond to climate change-related impacts, and further exacerbating vulnerability to climate change. 

The report's indicators reveal that climate change is increasing threats to health in all its dimensions. Current adaptation measures are insufficient to protect people from the current levels of warming, and there is an urgent need to accelerate efforts to build resilience, minimize impacts, and protect human lives. Each unit of greenhouse gas emissions increases risk, exacerbating the economic costs and challenges of adaptation. Therefore, simultaneous and effective mitigation is essential to keep adaptation feasible and to protect populations worldwide from the now-inevitable impacts of climate change. 

(Reference) 

The 2025 report of the Lancet Countdown on health and climate change, The Lancet (2025). https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(25)0191…;

Contributor: IIYAMA Miyuki, Information Program