• Posted August 4, 2025

Climate Change Will Send Many More Californians to the ER

California’s emergency departments will be more clogged than ever as climate change pushes daily temperatures higher, a study finds.

But there is one silver lining to the new research, however: Thousands of fewer deaths in California from extreme cold. 

Nevertheless, high temperatures will also be flooding hospitals with patients as heat triggers injuries and worsens chronic health issues. 

“Heat can harm health even when it doesn’t kill,” explained study first author Carlos Gould, assistant professor of public health at the University of California San Diego. “Warmer temperatures were consistently associated with more trips to the emergency department, so studies and planning that only consider mortality [death] miss a big slice of the burden.”

Working alongside researchers at Stanford University, Gould’s team looked at data on deaths, emergency department (ED) visits, hospitalizations and daily temperatures in California from 2006 to 2017.

The good news: projecting the health-related effects of climate change to 2050, California should expect to see around 53,500 fewer deaths overall due to less cold weather, the data showed. 

That could save the state an estimated $30 billion annually.

However, California will also experience surges in ED visits on hot days, which are projected to become more frequent.  

Of course, heatstroke is the effect that most people might associated with extreme heat. But many ED visits will be due to other heat-linked events or conditions: injuries, mental health issues and poisonings, especially. 

“We often think about only the most extreme health impacts of heat waves: deaths. This work is showing that many things that we may not think about being sensitive to extreme heat are, like poisonings, endocrine disorders, injuries and digestive issues,” said study co-author Alexandra Heaney.

“We need to focus on the full spectrum of health impacts when we think about heat waves, now and in the future,” said Heaney, who is assistant professor of public health at UCSD.

Certain demographics will be hardest hit. 

“Age plays a critical role in shaping health risks from temperatures,” Gould said. “Older adults are particularly vulnerable to cold temperatures, whereas younger adults and children are more affected by heat.”

Easing the health care burden of rising temperatures on California’s budget will take cooperation of various stakeholders, added study co-author Marshall Burke, associate professor of environmental social sciences at Stanford.

Hospitals, insurers and public health agencies should work together to prepare for hotter temperatures in coming years and tailor messages for those groups at highest risk. 

“Understanding who is affected, how, and at what temperatures is critical for planning appropriate responses to protect health,” Burke said in the UCSD news release. “This is true with or without climate change, but a warming climate makes it more important and alters who is exposed to what.”

The findings were published July 30 in Science Advances. 

More information

Find out more about protecting yourself in high heat at ready.gov.

SOURCE: University of California San Diego, news release, July 30, 2025