(CNN) Climate change could "halt and reverse" progress made in human health over the last century.
The grim analysis comes from one of the authors of a new report in the New England Journal of Medicine that suggests rising global temperatures could lead to many more deaths than the 250,000 a year the World Health Organization predicted just five years ago.
In reviewing the research on the topic, study co-author Sir Andrew Haines thinks our health is much more vulnerable to climate change -- and he believes 250,000 deaths is a "conservative estimate."
"We think the impact is more difficult to quantify because there is also population displacement and a range of additional factors like food production and crop yield, and the increase in heat that will limit labor productivity from farmers in tropical regions that wasn't taken into account among other factors," said Haines, a British epidemiologist and former director of the London School of Hygiene & Tropical Medicine.
Due to climate change-related food shortages alone, the world could see a net increase of 529,000 adult deaths by 2050, the report said. Climate change could force 100 million people into extreme poverty by 2030 and poverty makes people more vulnerable to health problems.
Haines adds that climate change, "while the most important environmental threat facing humanity," is not the only environmental problem that threatens our health.
The depletion of freshwater resources, the unprecedented biodiversity loss, ocean acidification, overfishing, pollution, deforestation and the spread of invasive species, that are related to climate change, but are environmental problems on their own, all compound these public health threats he said.
"It is an urgent task to understand how to safeguard health in the face of these dramatic trends, all of which are caused by human activities related to patterns of economic activity." Haines added.
An editorial accompanying the report urges medical professionals to take this report seriously. Its co-author, Dr. Caren Solomon, suggests doctors have a "special responsibility to safeguard health and alleviate suffering," and that mission should include working quickly to curtail greenhouse gas emissions.
"We hope that this work will make more people aware and hopefully get more involved," said Solomon, a primary care physician who serves as deputy editor at the NEJM, and an associate professor of medicine at Harvard Medical School and Brigham and Women's Hospital. Her editorial points out that the health care sector accounts for nearly one-tenth of US greenhouse gas emissions and would rank seventh in the quantity of such emissions internationally, if it were its own country.
Health care workers, she said, should encourage their organizations to reduce their carbon footprint.
Reducing a health care facility's carbon footprint is possible.
She points to groups like Boston Medical Center, which generates its own energy efficient electricity and has climate-friendly programs like its hospital-based rooftop farm. Or the Gundersen Health System in Wisconsin that in 2014 became the first health care system in the country to produce more energy than it consumes, using wind, solar and methane from a local landfill.
Solomon said physicians can also pressure politicians to create better climate change-oriented public policy and put pressure on groups to use financial divestment as a tool. In 2018, the American Medical Association and the Royal College of General Practitioners passed resolutions calling for divestment in fossil fuel companies.
Doctors can also help educate patients and motivate people to act.
"There are substantial benefits and co-benefits of working to reduce these greenhouse gasses," said Solomon. Riding a bike to work or walking, rather than driving, for example cuts down on climate change-related pollution and the exercise is better for your health. Cleaner air also improves people's health.
"We all know that prevention in medicine is enormously more effective and efficient, rather than waiting for full blown disease. We view climate change in the same manner and know that if we take action immediately, we can avoid the catastrophic health effects that are projected," Solomon said.
Haines would agree. "Future generations will, no doubt, look back at the missed opportunities for progress towards a healthy, sustainable economy and question why decisive action wasn't taken sooner," Haines said. "It is imperative to increase the scale of ambition and emphasizing the potential health benefits of doing so now and for future generations could help to motivate progress."