The Sacramento region has been making strides in improving its air quality, but rising temperatures from climate change could undo those gains, scientists say.
A recently released study by the National Center for Atmospheric Research predicts that areas in the U.S. not currently meeting federal ozone standards will see more unhealthy summertime air days, and regions that currently meet the standard may experience more unhealthy air-quality days.
The implications of the study are significant for the Sacramento region, whose annual average temperature has risen by 0.2 degrees Fahrenheit each decade since 1950, according to the National Climate Data Center. At present, Sacramento does not meet federal standards for healthy ozone levels as defined by the Environmental Protection Agency. Even without rising temperatures, it will likely be years before the region achieves compliance.
The new study found that by 2050, rising temperatures will cause an average 70 percent jump in summertime periods in which ozone standards are exceeded across the U.S.
Climate change means “more action is needed in order to reach attainment,” said Gabriele Pfister, lead author of the study, which was published last month in the Journal of Geophysical Research.
Hotter temperatures raise the amount of ground-level ozone, which is a greenhouse gas and a component of smog.
“There will be more ozone at a hundred degrees than at 95 degrees,” said Larry Greene, executive director of the Sacramento Metropolitan Air Quality Management District.
Aggressive steps taken statewide to curb emissions from cars and diesel trucks have eased the problem for now. The Sacramento region currently experiences 100-degree days without triggering high ozone levels that were seen in the past, Green said.
“Our background burden of pollution has been going down over the years. It takes a lot hotter day now for us to get the same level of ozone than it did 10 years ago,” Greene said.
However, if the recent study is any indication, that may change.
“Temperature, over time, will push back against the progress we have made,” Greene said.
Two forms of ozone exist in the atmosphere. The type found in the upper atmosphere is beneficial, shielding humans from ultraviolet radiation.
The unhealthy form is ground-level ozone, which forms when chemicals react in sunlight. Exhaust emitted by planes, trains and cars is the greatest contributor to ozone. Ground-level ozone is linked to asthma, increased risk of heart attacks, and in some cases, strokes and premature death in the elderly.
The Sacramento region has exceeded the EPA’s ozone standards since 2008, when the agency said measurements over 75 parts per billion in an eight-hour period were unhealthy.
Recently, though, the air in the capital has been improving – the result of some of the nation’s most stringent air regulations.
The Sacramento region has gone from posting 86 days exceeding the EPA’s eight-hour ozone standard level, to only 15 days in 2013. Peak ozone levels have also been dropping. The highest eight-hour concentration in the Sacramento metropolitan area was 107 ppb in 2000. In 2013, it was 90 ppb. Geography and wind patterns make some areas more prone to ozone. For example, Folsom typically records the highest ozone levels in the region, in part because the Sierra foothills trap pollution.
Call The Bee’s Edward Ortiz, (916) 321-1071. Follow him on Twitter @edwardortiz.