540,800 heat deaths a year, and the word 146 researchers have decided to use
What happened
On Tuesday 27 October 2026, The Lancet published the 2026 report of the Lancet Countdown on Health and Climate Change. It is the tenth of these annual reports. The Lancet Countdown is a large collaboration. This edition involved 146 researchers from more than 100 institutions in more than 30 countries. It was led by University College London and produced with the World Health Organization. Each year the report tracks a set of indicators: heat deaths, drought, extreme rainfall, air pollution, food security, energy investment, and how much money is going into protecting health from all of it. This year the authors went further than usual in their language. They called for climate change to be declared a global health emergency. The reason given is not that the harms are new. It is that the harms are growing faster than the response to them. The report finds that many climate-related health harms increased more quickly in the decade from 2016 to 2025, which is the decade after the Paris Agreement, than they did in the decade before it.
Why this matters
Climate reports usually talk in degrees and emissions. This one talks in deaths, working hours and money, which makes it harder to file away as somebody else's subject. The headline figure is heat. Across 2016 to 2023, heat was linked to an average of 540,800 deaths per year. Around 68% of those, about 369,900, were attributed to climate change rather than to heat that would have happened anyway. In the decade before, that share was 55%. In 2023 alone, the estimated figure was 710,000 heat-linked deaths, with 71.5% attributed to climate change. The report also finds that heat cut how much work people could do in 2025, at an estimated cost of 1.07 trillion US dollars, or 0.91% of global economic output. For the UK, the relevant signal is not drought in another continent. It is that heat kills older people, people with heart and lung conditions, and people on certain medicines, and that British housing was designed to hold heat in rather than let it out. The UK Health Security Agency now runs heat-health alerts in summer for exactly this reason. There is a second UK-relevant figure. Fossil fuel air pollution is estimated to kill about 2.73 million people a year worldwide. Air quality is one of the places where cutting emissions improves health immediately, not in fifty years.
What the evidence actually says
The report is an assessment of indicators, not a single experiment, so it is worth being clear about what kind of evidence this is. The figures are modelled estimates. Attributing a death to heat, and then attributing part of that heat to climate change, involves statistical modelling rather than counting certificates. The researchers are open about this, and the method is published and peer reviewed. But a figure like 540,800 is a best estimate with uncertainty around it, not a headcount. With that in mind, here are the other main numbers. In 2025, 51.8% of global land had at least one month of extreme drought. Very extreme rainfall covered about 17.2% of global land per year across 2016 to 2025, up from 14.8% in the decade before. On the response side, there is genuine good news. Clean energy investment reached a record 2.1 trillion US dollars in 2025, against 1.16 trillion for fossil fuels. The report credits clean energy investment, health system leadership, new health-protecting laws and better science with delivering real health gains. But fossil fuels still supply over 80% of global energy. And the money for adapting health systems is small: developing countries estimated a minimum need of 3.3 billion US dollars a year, while about 1.1 billion was committed in 2024. Climate-related health research funding rose to 316 million US dollars in 2024, but 84% of it went to researchers in the wealthiest countries. Professor Marina Romanello of UCL, the Countdown's executive director, summarised it as the health harms of climate change growing faster than the world's response to them. Professor Anthony Costello, co-chair, said the pace and scale of emissions reduction remains entirely out of step with the pace and scale of the harm. Helen Clark, former Prime Minister of New Zealand and chair of the Countdown's board, said what is missing is not evidence, but the political will to act on it. It is also fair to note what the report is: an advocacy-informed scientific assessment. The authors are making an argument as well as reporting indicators. The indicators are the part to check.
Qurexa perspective
There is one part of this that sits squarely in our work, and it comes up every summer. Most medicines are licensed to be stored below 25 degrees Celsius. Some, including many insulins, some eye drops and certain antibiotics, need a fridge. During the hot spells the UK now gets routinely, a parcel left in a porch or a car boot can go well past that. Heat also changes how some medicines affect people. Diuretics, often called water tablets, increase fluid loss. Some blood pressure medicines affect how the body handles heat. Certain antidepressants and antipsychotics interfere with sweating and temperature control. Anticholinergic medicines can do the same. None of that is a reason to stop taking them, and stopping is usually more dangerous than the heat. It is a reason to be more careful about fluids, shade and timing. When we plan deliveries, storage and timing are part of the job, not an afterthought. If you are on a medicine that needs cool storage and you are not confident about how it is being kept, ask your pharmacist. It is a quick conversation and it is worth having before a heatwave, not during one.
Practical advice
Nobody fixes global emissions from their kitchen. But there are things within reach that genuinely reduce harm. Know the heat-health alerts. The UK Health Security Agency and the Met Office issue them in summer. You can sign up to receive them, and they tell you when a hot spell is likely to affect health rather than just be pleasant. Know who around you is at higher risk: people over 75, babies and young children, people with heart, lung or kidney conditions, people with dementia, people who are bed-bound, and people living alone. A phone call during a heatwave is a reasonable thing to make. In hot weather, keep curtains closed on the sunny side during the day, open windows at night when it is cooler outside than in, drink water regularly, and avoid heavy exercise in the middle of the day. Check how your medicines should be stored. The information leaflet in the box says so. If something needs to stay below 25 degrees, find the coolest place in the house, and do not leave it in a car. Do not stop any medicine because of hot weather. Speak to your pharmacist or GP if you are concerned about how a medicine and the heat interact. On air quality, the Daily Air Quality Index is published by Defra and is worth a look on still, cold days as well as hot ones, especially if you have asthma or COPD.
What to know
The 2026 Lancet Countdown report, published in The Lancet on 27 October 2026, involved 146 researchers from more than 100 institutions in more than 30 countries, led by UCL with the World Health Organization. It calls for climate change to be declared a global health emergency, on the grounds that health harms are growing faster than the response. Heat was linked to an estimated 540,800 deaths a year across 2016 to 2023, with about 68% attributed to climate change, up from 55% in the previous decade. Clean energy investment hit a record 2.1 trillion US dollars in 2025, but fossil fuels still supply over 80% of global energy, and health adaptation funding falls far short of estimated need. These are modelled estimates with uncertainty, published and peer reviewed. The direction of travel is the robust part. For households, the useful actions are local: sign up for heat-health alerts, check on vulnerable neighbours in hot weather, store medicines properly, and never stop a medicine because of the heat without advice. Sources: The Lancet, 'The 2026 report of the Lancet Countdown on health and climate change', 27 October 2026, DOI 10.1016/S0140-6736(26)01779-4, https://doi.org/10.1016/S0140-6736(26)01779-4 ; News-Medical, 'Climate change intensifies global health risks, Lancet Countdown report warns', 27 October 2026, https://www.news-medical.net/news/20261027/Climate-change-intensifies-global-health-risks-Lancet-Countdown-report-warns.aspx ; Lancet Countdown, https://lancetcountdown.org/ This article is for general information and does not replace advice from a doctor, pharmacist or other qualified healthcare professional. Never stop or change a prescribed medicine without speaking to a professional first.
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