Lives & Money: How Climate Change Impacts Health

The acceleration of climate-related health impacts is worsening, with heat-related deaths rising by 63% since the 1990s, according to The Lancet.

The medical journal's 2025 Report of the Lancet Countdown on Health and Climate Change, developed in partnership with the World Health Organisation, reveals the extent of the mounting toll on global health systems and economies.

Labour capacity reduction due to heat exposure led to more than US$1tn in global potential income losses. 

The report “paints a stark picture”, says Adam Elman, Director of Sustainability EMEA at Google, on LinkedIn. 

“Despite the clear and escalating crisis, we see worrying backsliding.

“However, the report highlights that progress is possible and yields immediate benefits!”

Heat exposure and mortality

The analysis shows that between 2020 and 2024, individuals experience an average of 19 life-threatening heatwave days annually, with 16 of these directly attributable to climate change.

The data reveals that nearly 1% of all deaths between 2012 and 2021 are associated with heat exposure, though this burden falls disproportionately across different regions.

Low Human Development Index (HDI) countries record 1.73% of deaths linked to heat, compared to 0.53% in very high HDI nations.

Heat-related mortality rates climbed from 5.9 deaths per 100,000 people between 1990 and 1999 to 7.2 deaths per 100,000 during 2012 to 2021.

The physiological impacts extend beyond mortality, with sleep loss increasing by 9% in 2024 from baseline levels, the largest percentage increase recorded in the past decade.

 “This report once again provides strong evidence that the impact of climate change is being counted not just in degrees and carbon metric tonnes but in lives lost," says Dr Githinji Gitahi, Group CEO of AMREF Health Africa.

“The science reflects what communities across Africa experience daily – bearing the brunt of increasing heat-related deaths, rising infectious disease threats and growing food and water insecurity. 

“Health is the human face of climate change.”

The impact of extreme weather

Extreme weather events during 2024, coupled with adaptation delays, resulted in at least 16,000 deaths and affected a minimum of 166 million people.

These events displaced more than 800,000 individuals, creating humanitarian challenges with substantial economic ramifications.

Research cited in the report identifies anthropogenic climate change as a factor that increases the intensity or probability of at least 26 major extreme weather events in 2024, collectively accounting for more than 3,700 deaths.

A record 61% of global land area experiences extreme drought in 2024, 299% above 1950s averages.

These conditions threaten food and water security whilst causing considerable downstream economic losses.

Wildfire risk intensifies under hotter and drier conditions, with 2024 recording 154,000 deaths from wildfire smoke-derived small particulate matter air pollution.

“The climate crisis is a health crisis. Every fraction of a degree of warming costs lives and livelihoods,” explains Dr Jeremy Farrar, Assistant Director-General for Health Promotion and Disease Prevention and Care at the World Health Organization.

“This report, produced with WHO as a strategic partner, makes clear that climate inaction is killing people now in all countries.  

"However, climate action is also the greatest health opportunity of our time. Cleaner air, healthier diets, and resilient health systems can save millions of lives now and protect current and future generations.”

Addressing climate change for health

The report outlines priority actions for national governments and private sector organisations.

Governments could advance health protection through supportive regulations and financial incentives targeting both public and private sectors, enabling affordable renewable energy adoption and energy efficiency improvements.

The report describes a safe fossil fuel phase-out as "essential" to maintaining climate risks at adaptable levels.

Private sector organisations should consider science-based targets, fossil fuel divestment and renewable energy transitions.

Professor Charlotte Watts, Executive Director, Solutions at Wellcome, says: “Progress is being held back by underfunding and wavering political will. This must change. 

“At COP30, governments have a chance to accelerate health-centred climate action. Addressing the sources of climate change and investing in climate change adaptation will save people’s lives, strengthen economies and cut emissions to secure a better future.” 

Laura Clarke, CEO of ClientEarth, says: “We know what is needed to create a better future of clean air, healthy food and liveable cities. But too many governments and companies are turning away from that task, and even fuelling the climate crisis. 

“As attribution science, climate litigation and grassroots activism grow, accountability for climate impacts is no longer a question of if, but when.”