Members of Congress have come to expect controversy sometimes during their August break.
Four years ago, it was health care. This year many thought it would be immigration. But in California, global warming has become an unexpectedly hot topic.
Thanks to California Sen. Barbara Boxer, the White House and environmental groups, some Republican lawmakers are on the defensive over an issue that hadn't been on their August radar.
As wildfires raged in Southern California last week, Boxer, a Democrat who leads the Senate Environment and Public Works Committee, said climate change was making the problem worse and that Republican skeptics needed to "get out of the fringe lane."
"The wildfire season is starting earlier and ending later, the fires are growing bigger and hotter, and the impacts and costs of fighting these fires have increased dramatically," Boxer said while touring wildfire areas last week. "Climate change is already taking a toll, and the deniers need to stop denying it."
Over the weekend, Rep. Dana Rohrabacher, a Southern California Republican member of the House Science Committee, challenged Boxer to debate the science around the issue.
"A total fraud," he said.
"I challenge her to defend her positions," Rohrabacher told CBS Los Angeles, " . . . not just try to scare the public into accepting her expansion of government power over our lives."
Jack Pitney, a political science professor at Claremont McKenna College in Claremont, Calif., said that neither Boxer nor Rohrabacher, both longtime public figures, was known for shyness. They each "love provoking the other side," he said.
Boxer, through her office, said she wouldn't debate what was already settled, comparing the connection between global warming and climate change to the long-established link between smoking and cancer.
Rohrabacher spokesman Rick Dykema said the congressman still would like to debate her.
There's overwhelming agreement among scientists that greenhouse gas emissions are warming the planet. The California Environmental Protection Agency and the California Department of Forestry and Fire Protection agree.
Department Director Ken Pimlott said in a message on the department's website that warming trends were likely to increase the chances of more wildfires in the future.
"Research scientists predict significant increases in the occurrence of large fires and the amount of acres burned by the end of the century," he said.
Many prominent Republicans agree that climate change is happening, including former Environmental Protection Agency heads from the Nixon, Reagan and both Bush administrations, as well as former Secretary of State George Shultz.
But a deep vein of skepticism runs among current Republican officeholders, which Democrats have exploited.
This week, President Barack Obama's political arm, Organizing for America, fanned the flames, sending golden unicorn trophies to 135 Republican lawmakers, including Rohrabacher, for "exceptional extremism and ignoring the overwhelming judgment of science."
"This award is designed to draw attention to the anti-reality and anti-science position that Rohrabacher and others in Congress have taken," the group said in its release.
Dykema said the unicorn trophy "appears to be part of President Obama's campaign for legislation that would significantly harm the American economy without providing any noticeable environmental benefit."
"The number of recipients shows the 'award' was not specifically about Congressman Rohrabacher," Dykema added, "but about the larger national debate, and policy disagreements between the president and the House of Representatives."
The League of Conservation Voters also launched a $2 million nationwide television ad campaign aimed at several Republican lawmakers for their views on climate change. Though Rohrabacher wasn't among the targets, the group scored his environmental voting record last year at 6 percent. Boxer received a perfect score.
However, Pitney said Democrats had found themselves on the wrong side of science, too.
Several years ago, many prominent Democrats, including environmentalist Robert F. Kennedy Jr. and more recently even Obama, endorsed a now-discredited idea that childhood vaccines caused autism. The American Academy of Pediatrics has said that no such link exists.
"You've got people in both parties challenging mainstream science," Pitney said.
Democrats aren't always in lockstep on the environment, either. Obama supports the development of natural gas and oil extracted through hydraulic fracturing, or fracking, a technique that other Democrats and many environmental groups oppose.
Pitney predicted that the dispute between Boxer and Rohrabacher would generate fundraising activity on both sides, but that its real political impact would be limited.
"This isn't a high-priority issue for the public," he said.
By Curtis Tate and Erika Bolstad
McClatchy Washington Bureau