August 10, 2015

Global Warming Emissions Linked to Worsening Heat Waves in California’s Central Valley, New Peer-Reviewed Paper Finds

Washington (August 10, 2015)—Global warming emissions have significantly increased the risk of extreme heat in California’s Central Valley, according to new research published today in Climatic Change.

The study found that under natural conditions, the area would have just a one percent chance each year of experiencing a month with 13 days or more of 104 degree (F) temperatures. But when climate models accounted for heat-trapping emission from burning coal and oil and destroying tropical forests, temperatures in the region increased, particularly at night, and such strings of extremely hot days occurred more than twice as often.

Public health researchers sometimes use 104 degrees as a benchmark since it is associated with heat strokes and other illnesses; they also caution that higher night time temperatures make it harder for people to get relief from extreme heat.

 "We’re living and working in a different climate than our grandparents,” said Roberto Mera, a Kendall Science Fellow in climate attribution at the Union of Concerned Scientists and the paper’s lead author. “In the Central Valley, that has consequences for people who work outdoors, including Latino farmworkers, and people who don’t have access to air conditioning.”

Mera noted that a particularly severe Central Valley heat wave in 2006 resulted in emergency room visits, hospitalizations and at least 146 deaths, many of which occurred in Fresno. A previous study found that higher regional temperatures, along with higher humidity, have increased extreme heat risks. According to weather station data, regional nighttime temperatures were nearly 2 degrees (F) warmer in the 2000s compared to historic levels.

The new study, which was conducted by an international team of climate attribution experts, used modeling to compare the climate of the 2000s with and without industrial heat-trapping emissions. Model simulations were conducted by a volunteer, distributed computing network organized through weather@home.

Scientists are increasingly able to link risks and damage from climate change back to the industrial emissions. Researchers and legal scholars say such studies bolster arguments from climate justice advocates regarding carbon producers sharing responsibility for damage from climate change. Currently, such responsibility rests on governments, other businesses, and individuals.

The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet's most pressing problems. Joining with people across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future.