The World Health Organization is urging negotiators at next month’s UN climate conference, COP 26, to save millions of lives by reining in global warming.

The WHO’s report this week coincided with a call to action from more than 400 international health organizations and professionals, representing two-thirds of the world’s health care workers.

“The burning of fossil fuels is killing us,” the WHO said in an 82-page special report that laid out 10 recommendations for maximizing the health benefits of climate action. “Climate change is the single biggest health threat facing humanity.”

“The COVID-19 pandemic has shone a light on the intimate and delicate links between humans, animals, and our environment,” said WHO Director General Dr. Tedros Adhanom Ghebreyesus. “The same unsustainable choices that are killing our planet are killing people.”

“We know that climate change is impacting people’s health, this is increasingly visible around the world. We also know that many solutions to address climate change offer tremendous health co-benefits,” said Dr. Jeni Miller of Global Climate and Health Alliance, which coordinated the open letter. “The health community is really seeing that if we don’t step up and call for action on climate change, we’re failing the patients and the communities that we care for.”

The WHO report and the open letter were released just as new research in the journal Nature Climate Change concluded that 85% of the world population has experienced weather events made worse by the climate emergency.

“After using machine learning to analyze and map more than 100,000 studies of events that could be linked to global warming, researchers paired the analysis with a well-established data set of temperature and precipitation shifts caused by fossil fuel use and other sources of carbon emissions,” the Washington Post reports. “These combined findings—which focused on events such as crop failures, floods, and heat waves—allowed scientists to make a solid link between escalating extremes and human activities,” concluding that 80% of the world’s land mass has been affected by climate change.

“We have a huge evidence base now that documents how climate change is affecting our societies and our ecosystems,” said lead author Max Callaghan, a researcher at the Mercator Research Institute on Global Commons and Climate Change in Germany.

The public appeal, whose signatories include the WHO’s Ghebreyesus, “lists seven million premature deaths a year due to pollution and disturbance of global food systems by extreme weather as some of the health detriments caused by the climate crisis,” The Guardian writes. “It also argues that the costs of policies such as improving the cleanliness of air and water and creating more secure food supplies would be offset by savings in health care costs.”

In its report, the WHO notes that air pollution generated primarily by fossil fuels causes 13 deaths per minute around the world—and that the benefits of ambitious climate action far outweigh the cost.

“Bringing down air pollution to WHO guideline levels, for example, would reduce the total number of global deaths from air pollution by 80%,” said WHO environment, climate change and health director Maria Neira. A switch toward plant-based diets “could reduce global emissions significantly, ensure more resilient food systems, and avoid up to 5.1 million diet-related deaths a year by 2050.”

The report is meant to “offer positive encouragement” to world leaders attending the COP, said WHO health and climate head Diarmid Campbell-Lendrum. “We think it will boost the argument of any government or stakeholder around the world who is trying to encourage their population to get behind climate action,” he told The Guardian. “These health gains are so large they… provide a compelling argument.”

The UK-based paper says pediatric health care providers will cycle from London to Glasgow to formally present the WHO report to world leaders, after Campbell-Lendrum bikes from Geneva to put it in their hands.