Global health has improved for decades. Climate change could change that.

Muhammad Reza
·5 min read

As temperatures warm, the health risks of climate change are expected to intensify in the U.S. and worldwide.

The effects of climate change have already left millions of people hungry, caused deaths during heat waves and strained some people’s mental health as they are forced to leave their homes because of extreme weather, according to a major report from the United Nations’ Intergovernmental Panel on Climate Change, or IPCC, that was released Monday.

So far, scientists say, world leaders are falling short not only at reducing fossil fuel use and greenhouse gas emissions but also in making their communities more resilient to the health issues aggravated by climate change.

“We’re seeing impacts today that when you look to earlier assessment reports weren’t projected until later in the century. They’re occurring now,” said an author of the report, Kristie Ebi, a professor at the Center for Health and the Global Environment at the University of Washington. “People are dying from climate change. On the other hand, we’re not getting the investments we need.”

In the decades before the Covid-19 pandemic, measures of human health worldwide largely improved. Now, climate change could put those trends in jeopardy.

“For many aspects of human well-being, we are actually in a period of decades of progress,” said Brian O’Neill, a chief scientist at the Pacific Northwest National Laboratory who studies climate change risks and helped author the IPCC report. In particular, O’Neill cited the trend of reductions in worldwide poverty, malnourishment and child mortality. “Climate impacts slow that progress or put it at risk.”

The findings are part of a broad study by the IPCC of the effects of climate change, its impacts and how societies could adapt and prepare for a warmer climate. The assessment, which was written by 270 scientists from 67 countries, represents broad consensus among researchers about how global warming is affecting people and the environment — and the potential consequences of inaction.

Reducing poverty, improving health care and focusing on sustainable development could matter as much for people’s health and well-being as reducing emissions, O’Neill said.

“In places where we have evidence, our ability to adapt has not been keeping pace with climate change effects,” he said.

A clearer picture

Scientists are growing increasingly confident in their projections of risks to health from climate change.

“There’s a very long list of health outcomes that are affected by changing weather patterns and ultimately climate change,” Ebi said. “Since the last report, the evidence has become much stronger. We have a better picture of what’s going on.”

Without more action, the report found, billions more people worldwide could be at risk of contracting diseases like dengue fever, which is spread by mosquitoes that are expanding their range as temperatures warm. Heat-related deaths are expected to rise with temperatures. Illnesses contracted from contaminated food and water are expected to increase as flooding increases and certain pathogens become more prevalent. Warmer temperatures, which are expected to pressure food production, could make some foods less nutritious, which could lead to increases in hunger.

Preparing for the health impacts is key.

“Most of these health outcomes, to some level, could be prevented,” Ebi said.

Implementing heat-wave warning systems could ensure that vulnerable people have access to cooling. Better controlling the mosquitoes that cause dengue fever could reduce outbreaks. Investing further in drought-resistant crops could reduce the impacts of drought on food systems.

Mental health

For the first time, the IPCC authors evaluated and assessed research on climate change’s impacts on mental health, finding that many people are struggling as they reckon with the effects of global warming.

After an extreme weather event, such as a flood, a wildfire or a storm, people are more likely to experience post-traumatic stress disorder, depression, anxiety or substance abuse, said another author of the IPCC report, Susan Clayton, a social psychologist and professor who studies climate change at the College of Wooster in Ohio.

Heat, itself, can threaten mental health.

“There’s increasing evidence that high temperatures, themselves, are associated with decreased mental health, increased rates of suicide, psychiatric hospitalizations,” Clayton said.

Displacement, which could increase because of climate change, also presents a risk.

“If you have to leave your community, it’s a threat to mental health. It’s stressful,” Clayton said. “You’re losing your support system, facing new risks.”

Around the world, anxiety and stress are expected to increase as warming intensifies, the report found.

“Mental health affects physical health,” Clayton said. “It’s very hard to separate the two. People experiencing mental health threats might engage in more risky behavior. They might not take care of their physical health or put themselves more at risk.”

Few health systems are prepared, Clayton said.

“Most, if not all, countries don’t have sufficient support for mental health in their general health systems,” she said.

Creating resiliency

Strengthening health systems and further reducing societal vulnerabilities, investing in climate adaptations and reducing emissions could significantly reduce the number of people whose health and well-being suffer from climate change.

Depending on future climate policies, the number of people facing hunger by mid-century could range from 8 million to 80 million, a summary of the IPCC report said.

Extreme weather displaced about 30 million people globally in 2020, said an IPCC author, Robert McLeman, a professor of geography and environmental studies at Wilfrid Laurier University in Canada.

“These are people who have no choice but to leave their homes, on a temporary basis or on an indefinite basis, from weather-related or climate events,” McLeman said.

In a worst-case scenario, in which emissions rise, countries don’t collaborate well and governments fail to adapt, the number of people who are displaced could balloon to more than 140 million by 2050 just in sub-Saharan Africa, South Asia and Latin America, McLeman said, citing research by the World Bank. In a best-case scenario, in which warming is limited to 1.5 degrees Celsius (2.7 degrees Fahrenheit) and sustainable development goals are achieved, the number could be just 9 million.

“We’re moving in a worrisome direction,” McLeman said. “When you talk about the impacts of climate change and the implications of them, they often boil down to direct impacts on people’s health and well-being.”