In 2019 more than 100 health care organizations—including the American College of Physicians and the American Medical Association—signed a statement drafted by the Medical Society Consortium on Climate and Health. It begins: “Climate change is one of the greatest threats to health America has ever faced,” and outlines the need for bold action now.

Fighting climate change might well begin at home. The global health care industry itself is responsible for 4.4% of worldwide emissions of planet-warming greenhouse gases. If the global health care sector were its own country, it would be the fifth largest emitter of greenhouse gases, and the U.S. health care sector alone accounts for 27% of the global health care carbon footprint.

“It’s important for health care systems to lead the way in mitigating and decreasing their carbon footprint,” said Renee Salas, an emergency medicine physician at Massachusetts General Hospital on The New England Journal of Medicine’s Perspectives podcast. “We have the tools to solve this. We have the research and public health infrastructure and the ingenuity.”

That ingenuity, in fact, has taken a dizzying array of forms in recent years, as hospitals and health care systems rethink their use of energy, their physical resources and their relationship to the environment.