When the Paris Agreement was adopted in 2015, then-President Barack Obama said, "This agreement represents the best chance we've had to save the one planet that we've got.”

But a decade later, a new report, led by University College London in collaboration with the World Health Organization (WHO), finds that while progress has been made, many detrimental health indicators linked to climate change are moving in the wrong direction. The report's authors are also warning that problems aren't just increasing -- they're accelerating.

"A decade after the Paris Agreement, our findings are unambiguous: the health harms of climate change are growing faster than the world's response to them, and in many cases even accelerating," said Marina Romanello, a professor at University College London and the executive director of the Lancet Countdown in a statement.

The 2026 report of The Lancet Countdown on health and climate change includes findings from 146 researchers at more than 100 institutions in more than 30 countries. Researchers found evidence that heat was linked, on average, to more than 540,000 estimated deaths per year from 2016, when the Paris Agreement went into effect, through 2023, the latest year with available data. The researchers attribute 68% of those fatalities to climate change.

"These numbers point to a clear emergency," Romanello said in a statement. "The rate of increase in many climate-related health threats is accelerating, while heat deaths linked to climate change have reached a record-high, and the economic toll is battering vulnerable sectors and communities the hardest."

The past 11 years have been the 11 hottest on record. In 2023, heat could be linked to 710,000 estimated deaths, with more than 71% attributable to climate change, the report said. That number exceeded the loss of life from malaria or HIV, according to the researchers. For the entire period of 2016 to 2023, the report found that nearly 3 million deaths could be connected to climate change.

According to the report, heat is also taking a toll on the global economy. Because of reduced productivity, the researchers estimated that the world lost more than a trillion dollars in potential income in 2025. They say it's the third consecutive year that losses topped the trillion-dollar mark.

"The threats to people's health and people's survival have reached unprecedented levels, with many of these threats and impacts even accelerating in the last decade with respect to the previous one," Romanello said.

The researchers also found the pace at which land is being hit by extreme drought accelerated by about 700% between 2016 and 2025 compared with the decade before the Paris Agreement. In 2025, more than half of the world's land experienced extreme drought for at least a month. In other cases, climate change brought too much precipitation, which can result in flash flooding. The report found that the share of land hit by very extreme rainfall rose from 14.8% between 2006 to 2015 to 17.2% from 2016 to 2025.

"The risks become even more profound when you consider how different hazards interact and compound. At the same time, drought is spreading, and the world is swinging to water extremes, some drying out, while others are flooding. This isn't a gradual worsening; it's a step change that must be recognized as the global health emergency it is," Romanello said.

But it's not all bad news. The report noted that global investment in clean energy grew by more than 7% in 2025, reaching a record $2.1 trillion. That's 82% more than was invested in fossil fuel energy sources, according to the researchers. The report said new investment helped renewables grow from 5.5% of global electricity generation in 2016 to 13.5% in 2023. As a result, the report found that cleaner air prevented an estimated 323,000 deaths a year in dozens of countries, though increases elsewhere offset those gains globally.

Still, despite the growth of renewable energy, fossil fuels accounted for over 80% of global energy supply, the report found, and the authors say the resulting air pollution is responsible for about 2.7 million deaths worldwide each year.

Based on their findings, the report's authors say climate change should now be treated as a "global health emergency" and they laid out six priorities for a "health-centered response" to the warming planet.

For one, they say the WHO and United Nations should use their existing resources to respond to the challenges, and they recommend that the WHO create a new way to formally recognize climate change as a health emergency and coordinate a global response. They also suggest making health and well-being core objectives and measures of success in all climate action.

The authors say countries and global institutions need to make climate and health a top priority and they call for cutting greenhouse gas emissions quickly and fairly to protect people's health. In addition, the researchers recommend creating a shared pool of climate and health data that everyone can use and having wealthier countries provide more grants and low-interest loans.

"We have not really managed to tackle climate change 10 years after the Paris Agreement, and we're seeing these escalating health harms that have made climate change now a very severe, very grave global health emergency that requires an urgent emergency response to be adequately addressed," Romanello said.

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