At the end of February, the email inbox of Regina LaRocque, an infectious diseases specialist at Massachusetts General Hospital, was flooded to overflowing. She had widely shared the draft of an amicus brief in the landmark Juliana v. United States case, in which 21 young people are suing the U.S. government over climate change. Physician groups and public health experts had only 48 hours to decide whether to sign on.

Advocacy is a touchy topic for some physicians, who fear it may compromise their private roles as healers. Professional groups can be especially wary of controversy—and when they do move, says LaRocque, they do not move quickly. But the amicus on Juliana v. United States broke this precedent. Hour after hour, the responses to LaRocque rolled in: “Yes.” “Please include our foundation.” “Count me in.”

The court case aims to block the U.S. government from its continued support for national reliance on fossil fuels. It cites future harm that will be suffered by the young plaintiffs—all of whom were younger than 20 years old when the case was brought in 2015.

The amicus brief was a collaborative effort between a team at Harvard Medical School and Harvard Law School, led by Wendy Jacobs, the director of the Emmett Environmental Law and Policy Clinic. The document, filed on March 1, 2019, aims to lend scientific weight to the claim that the Juliana generation “is suffering—and will continue to suffer as they age—harms different from those of prior generations.”

Climate-related threats to health have been well-documented in scientific literature: rising risk of extreme weather events, increased heat stress, decreased air quality and altered patterns of infectious disease, among other dangers. The Juliana generation is also likely to experience “insecurity” related to food, water and nutrients in some regions of the United States. Children are especially vulnerable, according to the amicus brief, because of their “developing bodies; higher exposure to air, food, and water per unit of body weight; unique behavior patterns; and dependence on caregivers.” But “prompt reductions” in greenhouse gas emissions, the amicus authors argue, could relieve some of these effects.

More than a dozen professional organizations—including the American Academy of Pediatrics, the American Heart Association and the American Lung Association—as well as 72 department chairs, physicians, nurses and public health experts agreed to endorse the brief. In fact, the team from Harvard Law School and Harvard Medical School that authored the brief secured so many signatories, they couldn’t include them all within the tightly prescribed word count. “We had to turn people away,” LaRocque says.

The medical profession has a tradition of activism on matters of public health. During the progressive era of the 1890s through the 1920s, physicians banded together to advocate for more humane child labor laws and better care for the mentally ill. Beginning in the 1960s, advocacy became both more vocal and more organized. The International Physicians for the Prevention of Nuclear War—an outgrowth of the U.S.-based Physicians for Social Responsibility (PSR)—won the Nobel Peace Prize in 1985 for its wide-ranging work on nuclear disarmament.

But climate change is quickly becoming a flashpoint for the current generation of physician activists, and PSR now ranks climate change as a top priority alongside nuclear disarmament. That focus has coalesced only during the past few years, says Jim Recht, an assistant professor of psychiatry at Harvard and a member of PSR. “We've been slow to wake up to what's really happening,” he says.

For some, a change in attitude was sparked by seeing the effects of climate change in their own practices. For Lynn Ringenberg, a pediatrician in Florida for 40 years and a former president of PSR, it was an uptick in asthma among her young patients. Others have been swayed by the most recent National Climate Assessment, a congressionally mandated report, which concluded: “Climate change is projected to significantly damage human health, the economy, and the environment in the United States.”

While most physicians may agree about the dangers of climate change, many remain uncertain about what actions are effective and appropriate. In a recent editorial in The New England Journal of Medicine, LaRocque and her colleague Caren Solomon outlined a range of possible actions, including institutional divestment from fossil fuel companies or insisting on change from within the health care industry, which accounts for nearly 10% of U.S. greenhouse gas emissions. Physicians might also take a larger role in shaping legislation through meeting legislators and testifying at public hearings, or even participate in direct action such as protests.

Whatever form it takes, action trumps the intolerable path of doing nothing, says Ringenberg. “I'm worried that we're not going to leave a good place for the next generation,” she says. “We’re innovative, we’re caring, we’re bright. So if we all work together, we can move the needle on climate change.”