Burning fossil fuels has driven climate change, and now climate change is costing people their health and increasingly their lives, says a new report from the prestigious medical journal the Lancet. The eighth annual Lancet Countdown, an international analysis that tracks nearly 50 different health-focused issues affected by climate change, calls for an immediate wind-down of fossil fuel use.

"We're currently at 1.14 degree Celsius of global indicator heating, and we're already seeing climate change claiming lives and livelihoods in every part of the world," says Marina Romanello, a scientist at University College, London, and the lead author of the report. "The impacts are happening here and now. However, these impacts that we're seeing today could be just an early symptom of a very dangerous future unless we tackle climate change urgently."

Every country is affected. But those with the least historical responsibility for causing climate change are feeling the worst effects. Pakistan–a country responsible for roughly 0.3% of all climate-change-causing carbon emissions, suffered massive floods in 2022 that displaced more than 30 million people and killed at least 1,700.

But wealthier countries are not immune. In the U.S., wildfire smoke this summer sent people to the emergency room from New York to Georgia. In Europe, a 2022 summer heat wave resulted in over 60,000 deaths.

Heat waves and droughts, actively intensified by climate change, affected food production worldwide in 2021 and pushed 127 million people into food insecurity, according to the report. Supercharged heat waves have driven the number of heat-related deaths amongst people over 65 up by more than 80% compared to the 1980s.

"This year was brutal for many people around the world–and we expect to see that next year, and the year after," Romanello says.

The report puts those heat deaths in stark context: less than half of them would have occurred in a world without climate change.

The ability to link climate events and health outcomes unambiguously is a relatively new scientific development, Romanello says. It's a variation on a relatively new scientific technique called "climate attribution," where sophisticated climate models compare real-world climate disasters with hypothetical ones in which human-driven climate change hadn't occurred.

Researchers can use this technique to figure out how much more likely climate change made a certain heat wave, for example. They can see how many people were affected by that extra-hot stretch of time.

The Lancet Countdown also details staggering economic costs that stem from climate change. About one fifth of all U.S. residents work outdoors; the percentages are even higher in many other countries. When it gets too hot, it gets harder and harder to work. Last year, the report says, outdoor workers lost more than 140 hours each–or several weeks of pay–because of excess heat. Scaled up, that cost countries in Africa an average of 4% of their gross domestic product in 2022.

The human and economic costs are forecast to grow with every tenth of a degree hotter the planet gets. Heat-related deaths, for example, could increase by nearly a factor of five by the middle of the century, absent immediate reductions to carbon emissions.

Fossil fuels make people sick

The economic and health impacts are part and parcel, says Renee Salas, a doctor at Harvard's Chan School of Public Health, because they have a common source: fossil fuel burning. It is, she says, "the root cause of the health problems that I'm seeing in my patients and my colleagues are seeing around the world."

The report directly calls for a wind-down of fossil fuel extraction. By limiting further warming the number of health problems and deaths attributable to climate change would dramatically reduce.

"I had a young [patient] who presented with uncontrollable asthma. And she lived right next to a highway and was breathing in toxic exhaust from cars burning gas," says Salas. "So the treatment she needs is electric vehicles and home weatherization and air purification. These are prescriptions I can't write."

The report, she says, presents the primary prescription: phasing out fossil fuel use. The planet has warmed by 1.1 degrees Celsius (2 degrees Fahrenheit) since major fossil fuel extraction began in the 1800s, and it is now expected to warm past 1.5 degrees C.

Though most countries have agreed to try to limit warming to well below 2 degrees C by phasing out fossil fuel use quickly, many nations are still actively expanding fossil fuel extraction efforts. Investment in fossil fuels rose by 10% in 2022, the report points out.

Solutions to climate change can improve global health

Across the globe, nearly 2 million people die each year because of long-term exposure to fine particles produced by burning coal, gas, and other fuels. "The number of people who die from the air pollution produced from fossil fuels every year, it is mind blowing," says Katharine Hayhoe, a climate researcher and lead scientist at the Nature Conservancy who was not involved in the report.

The impacts drop nearly instantaneously when the particles go away. It's an example, Hayhoe says, of a win-win: health harms from pollution drop in tandem with heat-trapping carbon emissions.

Along with a prescription for cutting climate-change-causing carbon emissions, the Lancet Countdown authors call for practical adaptations for health care systems facing climate-caused problems whether they like it or not. That means tools like better tracking for mosquito-borne disease, or developing effective early-warning systems for heat waves.

There will eventually be limits to adaptation, Romanello says. Health systems already struggle to handle the influxes of patients after major climate-influenced disasters like wildfires and hurricanes, and that influx will continue to rise as the planet warms. "The increase in those health hazards, we will definitely not be able to cope with," Romanello says. "So that's why we say mitigation is essential, to ensure a livable future. And it's a public health intervention. It's primary prevention at its heart."