Climate change is increasingly threatening human health and survival, with heat-related deaths, lost livelihoods and worsening drought among the mounting impacts, as governments struggle to prepare for a crisis researchers say demands urgent global action.
The 2026 Lancet Countdown on Health and Climate Change report, its 10th annual assessment, draws on the work of 146 researchers and tracks 54 indicators. It finds that health risks linked to climate change have accelerated since the Paris Agreement entered into force in 2016, compared with the previous decade.
The report acknowledges progress. Action since 2016 has reduced projected end-of-century warming from 3°C–3.5°C to 2.6°C–3.4°C, while the growth of zero-emission energy has exceeded expectations.
The World Health Organisation (WHO) has also made addressing climate change a core priority under its Global Programme of Work 14.
But greenhouse gas emissions continue to reach record highs, while weakening multilateralism and growing climate disinformation, denialism and scepticism are undermining collective action.
Heat was associated with an average of 540 800 estimated deaths a year globally between 2016 and 2023, of which 68% — about 369 900 — were attributable to human-caused climate change.
In 2023, heat was associated with a record 710 000 deaths globally, with 71.5% of the toll attributed to climate change.
The findings are reflected in South Africa, where climate change was responsible for 87.4% of the heatwave days experienced by the population between 2021 and 2025.
The country’s youngest and oldest age groups — children under one and adults over 65 — each experienced an average of about four heatwave days a year during that period. This was about two additional days annually compared with 1986–2005, an increase of 119% for infants and 110% for older people.
The effects extend beyond exposure to extreme temperatures. South Africans lost an estimated 32.6 hours of sleep a year because of high night-time temperatures between 2021 and 2025.
Heat also posed at least a moderate risk of heat stress during moderate outdoor physical activity, such as brisk walking, for about 463 hours annually between 2016 and 2025 — 65 hours, or 16%, more than the annual average in the 1990s.
The average annual monetised value of heat-related mortality among South Africans older than 65 was estimated at $1.38 billion between 2021 and 2025. This was 161% higher than in 2000–2004 and equivalent to about 79 500 average annual incomes.
Professor Marina Romanello, the executive director of the Lancet Countdown at University College London, said: “The health harms of climate change are growing faster than the world’s response to them, and in many cases, even accelerating.
“Real progress has been made in clean energy, health system readiness and health-protective regulation, all of which are delivering health benefits to communities. However, progress has been too slow, too small and isn’t reaching those who need it most.”
The consequences of rising temperatures are also being felt in people’s ability to work and earn a living.
Heat exposure caused an estimated 573 billion potential work hours to be lost globally in 2025, resulting in $1.07 trillion in potential income losses. South-East Asia and Africa were hardest hit, with losses equivalent to 3.9% and 3.2% of GDP, respectively, compared with 0.2% in Europe and 1.5% in the Americas.
Globally, agriculture and construction accounted for the largest shares of heat-related potential income losses, at 38% and 29% respectively.
WHO director-general Dr Tedros Adhanom Ghebreyesus said: “By placing health at the heart of climate policies, we can save millions of lives, build more resilient societies and deliver a healthier future for all.”
Extreme drought affected 51.8% of the world’s land area for at least one month in 2025, the second-highest level recorded. The area affected grew 704% faster in 2016–2025 than in the previous decade.
In South Africa, 31% of the country’s land area experienced at least one month of extreme drought annually between 2021 and 2025, compared with 11% in 1981–1990.
A new satellite-based analysis found that, since 2003, 43% of the world’s land area had experienced a long-term decline in water storage, while 37% had experienced a long-term increase.
Fossil fuels supplied 80.7% of global energy, while energy-related greenhouse gas emissions reached a record high in 2024. Yet global investment in clean energy reached $2.1 trillion in 2025, 82% more than the amount invested in fossil fuels.
Health gains are evident, with cleaner air preventing an estimated 323 000 deaths a year in at least 77 countries where air pollution from fossil fuels has fallen since 2016.
But rising energy demand and slow system change mean fossil fuels supply more than 80% of the world’s energy, while climate-heating emissions reached a record high in 2024. Despite progress in some countries, fossil-fuel air pollution causes an estimated 2.8 million deaths a year worldwide
In South Africa, the monetised value of years of life lost because of air pollution amounted to $19.25 billion in 2023, equivalent to about 4.8% of national GDP.
Renewable sources accounted for 8.2% of South Africa’s electricity generation in 2023, while no road transport energy came from electricity. Electrifying households and road transport using renewable energy could reduce harmful air pollution and protect health, the country profile notes.
There has been progress in preparing health systems for climate change, although significant gaps remain. By 2025, 47 WHO member states reported having conducted a vulnerability and adaptation assessment since 2020, while 56 had developed a health national adaptation plan, up from 14 in 2015.
However, 75.8% of member states had not reported completing an assessment since 2020 while 71.1% had not reported developing a health adaptation plan. Early-warning systems for climate-related health hazards are available in 75 countries and are helping to limit the adverse impacts of climate hazards.
The report also points to growing legal and policy action. The number of national climate laws referencing health has increased 50-fold since 2000. Climate change litigation has gained momentum as a tool to advance action, the report says.
In May 2026, 141 countries voted in favour of a resolution welcoming the International Court of Justice’s advisory opinion and calling on all states to take every possible step to address climate change, strengthening the case for further legislation and litigation.
But financing remains a major obstacle. Figures from 48 developing countries put annual health adaptation needs at at least $3.3 billion. International climate finance delivered covered less than a third of these disclosed needs.
“Decades of unmet commitments mean that avoiding the most catastrophic outcomes of climate change now requires a new approach to deliver system-wide change at a scale and pace matching the immediacy and gravity of the hazards otherwise faced,” the report says.
Its recommendations include recognising climate change as a global health emergency through a new WHO instrument; strengthening international coordination and early-warning systems; and accelerating just and equitable emissions cuts.
The researchers also want health outcomes to become central measures of climate policy, a global climate and health data commons to improve access to information, and more accessible grant-based finance for health adaptation in developing countries.
Helen Clark, a former prime minister of New Zealand and the chair of the Lancet Countdown’s board, said: “Governments must double down on their climate action commitments and rebuild momentum for international co-operation.”