Lancet Countdown 2026: Heat Deaths Hit a Record 710,000 as Researchers Call for a Global Health Emergency

Remember last summer’s wardrobe debates? Linen or cotton, sandals at the office or not, whether a mini fan clipped to your phone counts as an accessory. They felt trivial at the time. A new report suggests the heat behind them is anything but. According to the 2026 edition of the Lancet Countdown on health and climate change, published this week, heat was linked to an estimated 710,000 deaths in 2023 alone. That is more than malaria or HIV caused that year.

We are a fashion and lifestyle magazine, so you may wonder why we are reading a 54-indicator scientific report on a Wednesday morning. The answer is simple: the way you dress, travel, work and sleep is increasingly shaped by temperature. And the Lancet Countdown is about as authoritative as climate and health research gets.

What the Lancet Countdown 2026 found

The report is the tenth annual edition of the project, led by University College London together with the World Health Organization. It draws on 146 researchers from more than 100 institutions. Its headline message is stark: the health harms of climate change are growing faster than the world’s response to them.

The heat numbers are the most striking. Between 2016 and 2023, heat was associated with an average of about 540,800 deaths per year. The researchers attribute 68 percent of those to climate change, up from 55 percent in the previous decade. In 2023, the hottest year in the period, estimated heat deaths reached a record 710,000, with 71.5 percent attributed to climate change. Over 2016 to 2023, the report estimates almost 3 million heat deaths were caused by climate change.

A word on what these numbers are and are not. They are modelled research estimates, not a tally of death certificates that list “heat” as a cause, so they come with uncertainty. They are also one of the most comprehensive global pictures of a risk that rarely announces itself as dramatically as a storm or a flood.

It is also about money and work

Heat does not only affect health directly. The report estimates that in 2025 lost work capacity due to heat cost about US$1.07 trillion in potential income worldwide, the third year in a row above the trillion mark. Agriculture and construction absorb the largest shares, which makes sense: you cannot move a wheat field or a scaffold into an air-conditioned office. The burden falls hardest on South-East Asia and Africa, where losses reach more than 3 percent of GDP, compared with 0.2 percent in Europe.

There is a fashion angle here. It is not a frivolous one. Much of the world’s clothing is made in countries where workers face extreme heat in factories and fields. When we talk about the true cost of a garment, temperature is becoming part of the bill.

Drought, rain and the weather whiplash

The report also documents extremes in both directions. In 2025, 51.8 percent of the world’s land experienced at least one month of extreme drought, the second-worst year on record after 2023. At the same time, the share of land hit by very extreme rainfall rose from 14.8 percent per year in 2006 to 2015 to 17.2 percent in 2016 to 2025. Drought can threaten food security and water quality, while floods raise the risk of infectious and respiratory illness.

If this sounds like the plot of a disaster film, it is worth remembering that Hollywood’s version usually involves one dramatic weekend. The Lancet data describes something slower and harder to dramatise: a steady upward line, year after year.

Not all the news is bad

The researchers also found progress, which deserves equal billing. Clean energy investment reached a record US$2.1 trillion in 2025, 82 percent more than investment in fossil fuels. Renewables rose from 5.5 percent of global electricity generation in 2016 to 13.5 percent in 2023. In at least 77 countries where fossil fuel air pollution fell, cleaner air is estimated to prevent around 323,000 deaths a year. And more countries now have health adaptation plans and early warning systems for extreme weather, which the report credits with slowing increases in deaths.

The catch is scale. Fossil fuels still supply more than 80 percent of global energy. Air pollution from them is linked to an estimated 2.73 million deaths each year. “The pace and scale of emissions reduction remains entirely out of step with the pace and scale of the harm,” said Lancet Countdown co-chair Anthony Costello.

A call for a global health emergency

The authors’ central recommendation is political. They urge that climate change be formally recognised as a global health emergency, with a new WHO instrument to coordinate the response and health placed at the centre of climate decisions. Marina Romanello, executive director of the Lancet Countdown, said progress has been “too slow, too small” and is not reaching those who need it most. Helen Clark, chair of the Countdown’s board, put it in one line: what is missing is not evidence but political will.

Whether governments follow that call is an open question. What the report makes clear is that this is not a distant scenario. It is the backdrop of the summers you have already lived through.

What this means for you

On an individual level, the WHO lists older adults, infants and young children, pregnant women, outdoor workers and people with heart or lung conditions or diabetes among those most at risk during heat. Its #KeepCool advice is refreshingly practical: limit strenuous activity in the hottest hours, ventilate your home at night, drink water and check on people who spend a lot of time alone. It also recommends light clothing, which we have decided to read as a styling tip. If you are unsure how heat affects your own health or medication, your doctor or pharmacist is the right person to ask.

And on a cultural level, perhaps it is time to retire the idea that a scorching summer is simply good weather for a terrace. The breezy linen shirt is still a great idea. It is just no longer the whole answer.

This article is for general information only and does not replace professional medical advice. If you have health concerns, please consult a doctor.