Among the biggest threats humans face a warming climate is heat stress, which not only kill people directly but can also lead to kidney and cardiovascular disease, the report noted. Higher temperatures can also diminish people's ability to work, especially in agriculture, leading to tens of billions of hours of lost labor capacity every year.
Most worrying, according to the authors, is the compounding effect of extreme weather events that are exacerbated by climate change. Heat waves, floods and storms can batter the very public health systems that are meant to help people, the report says. A failure to rein in emissions, it warns, could lead to disasters that "Disrupt core public health infrastructure and overwhelm health services."
The American report, called the National Climate Assessment, says that extreme rainfall could overwhelm the nation's ailing water and sewer systems, contributing to shortages of drinkable water and increasing exposure to gastrointestinal disease. In some parts of the country, like Florida and Texas, higher temperatures will be a boon to a type of mosquito that transmits the viruses that cause dengue, zika, chikungunya and yellow fever.
Echoing these warnings on Wednesday, the United Nations Secretary General, António Guterres, urged world leaders to swiftly curb greenhouse gas emissions as they had promised under the Paris climate agreement three years ago. Nine out of 10 people have been found to be unsafe air, according to the World Health Organization, Mr. Guterres said. "Meeting the Paris Agreement commitments could save more than a million lives a year," he said.
Cutting emissions from sources like coal-fired power plants and diesel-burning trucks will also result in enormous savings to public health systems, the Lancet authors said. "Doing that now would be good for us, it would be good for our livelihoods and would be good for the planet," Dr. Ebi said.