Lives & Money: The Health Cost of Climate Change

Failure to curb the warming effects of climate change has caused the growth of heat-related deaths to grow by 63% since the 1990s according to The Lancet.

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

The medical journal’s 2025 Report of the Lancet Countdown on Health and Climate Change, produced in collaboration with the World Health Organization, details the impacts of climate change and health. 

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!”

The impacts of heat on health

The report says that on average, 16 of the 19 life-threatening heatwave days people were exposed to annually between 2020 and 2024 would not have occurred without climate change. 

Between 2012 and 2021, nearly 1% of all deaths were associated with heat, the report found. 

In low Human Development Index (HDI) countries this percentage reached 1.73%, compared to 0.53% in very high HDI countries. 

Between 1990 and 1999, heat-related mortality averaged 5.9 deaths per 100,000 people.

This figure increased to 7.2 deaths per 100,000 between 2012 and 2021. 

Increased heat can also impact sleep, with an increase of 9% sleep loss in 2024 from baseline. 

The report says this is the largest percentage increase in lost sleep in the past decade. 

Dr Githinji Gitahi, Group CEO of AMREF Health Africa, says: “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. 

“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.”

Health in extreme weather events

Extreme weather events in 2024, combined with delays in adaptation, caused at least 16,000 deaths and impacted at least 166 million people, the report says. 

It is estimated that these events led to the displacement of more than 800,000 people. 

Research cited in the report found that anthropogenic climate change increased the intensity or probability of occurrence of at least 26 of the most impactful extreme weather events in 2024. 

These impacts jointly account for more than 3,700 deaths. 

A record-breaking 61% of global land area was affected by extreme drought in 2024, 299% above the average in the 1950s. 

This can threaten food and water security, sanitation and cause downstream economic losses. 

Hotter and drier conditions are increasing the risk of wildfires, and the report found that 2024 had a record-high 154,000 deaths from wildfire smoke-derived small particulate matter air pollution. 

Weather conditions are also becoming more suitable for the spread of deadly infectious diseases, the report says. 

The direct health impacts of climate change are compounded by socioeconomic impacts, with a record-high US$1.09tn in potential income losses from heat in 2024 and more than US$304bn in losses from weather-related extreme events. 

“The climate crisis is a health crisis. Every fraction of a degree of warming costs lives and livelihoods,” says 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 Lancet’s report also details priorities for the protection of health amid global turmoil.

National governments, it says, can promote a safer future through creating supportive regulations and financial incentives applied to both the public and private sectors. 

These policies should help to enable affordable renewable energy, energy efficiency and a safe fossil fuel phase out, which the report describes as “essential” to keep climate risks within levels that countries can adapt to. 

For private sector organisations, the report recommends setting science-based targets, divesting from fossil fuels, transitioning towards renewable energy and developing collaborations to advance climate change action.

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.”