As a scientist, I shouldn't have a stake in the upcoming midterm elections, but unfortunately, it seems that I -- and indeed all my fellow climate scientists -- do.

Rep. Darrell Issa (R-Calif.) has threatened that, if he becomes chairman of the House Committee on Oversight and Government Reform, he will launch what would be a hostile investigation of climate science. The focus would be on e-mails stolen from scientists at the University of East Anglia in Britain last fall that climate-change deniers have falsely claimed demonstrate wrongdoing by scientists, including me. Rep. James Sensenbrenner (R-Wis.) may do the same if he takes over a committee on climate change and energy security.

My employer, Penn State University, exonerated me after a thorough investigation of my e-mails in the East Anglia archive. Five independent investigations in Britain and the United States, and a thorough recent review by the Environmental Protection Agency, also have cleared the scientists of accusations of impropriety.

Nonetheless, Virginia Attorney General Ken Cuccinelli is investigating my previous employer, the University of Virginia, based on the stolen e-mails. A judge rejected his initial subpoena, finding that Cuccinelli had failed to provide objective evidence of wrongdoing. Undeterred, Cuccinelli appealed the decision to the Virginia Supreme Court and this week issued a new civil subpoena.

What could Issa, Sensenbrenner and Cuccinelli possibly think they might uncover now, a year after the e-mails were published?

The truth is that they don't expect to uncover anything. Instead, they want to continue a 20-year assault on climate research, questioning basic science and promoting doubt where there is none.

Cuccinelli, in fact, rests his case largely on discredited claims that Rep. Joe Barton (R-Tex.) made during hearings in 2005 at which he attacked me and my fellow researchers. Then-Rep. Sherwood Boehlert (R-N.Y.) had the courage and character to challenge Barton's attacks. We need more political leaders like him today.

We have lived through the pseudo-science that questioned the link between smoking cigarettes and lung cancer, and the false claims questioning the science of acid rain and the hole in the ozone layer. The same dynamics and many of the same players are still hard at work, questioning the reality of climate change.

The basic physics and chemistry of how carbon dioxide and other human-produced greenhouse gases trap heat in the lower atmosphere have been understood for nearly two centuries. Overloading the atmosphere with carbon dioxide from burning fossil fuels is heating the planet, shrinking the Arctic ice cap, melting glaciers and raising sea levels. It is leading to more widespread drought, more frequent heat waves and more powerful hurricanes. Even without my work, or that of the entire sub-field of studying past climates, scientists are in broad agreement on the reality of these changes and their near-certain link to human activity.

Burying our heads in the sand would leave future generations at the mercy of potentially dangerous changes in our climate. The only sure way to mitigate these threats is to reduce global greenhouse gas emissions dramatically over the next few decades. But even if we don't reduce emissions, the reality of adapting to climate change will require responses from government at all levels.

Challenges to policy proposals for how to deal with this problem should be welcome -- indeed, a good-faith debate is essential for wise public policymaking.

But the attacks against the science must stop. They are not good-faith questioning of scientific research. They are anti-science.

How can I assure young researchers in climate science that if they make a breakthrough in our understanding about how human activity is altering our climate that they, too, will not be dragged through a show trial at a congressional hearing?

America has led the world in science for decades. It has benefited our culture, our economy and our understanding of the world.

My fellow scientists and I must be ready to stand up to blatant abuse from politicians who seek to mislead and distract the public. They are hurting American science. And their failure to accept the reality of climate change will hurt our children and grandchildren, too.

Michael E. Mann, the author of "Dire Predictions: Understanding Global Warming," is a professor in the meteorology department at Penn State University and director of the Penn State Earth System Science Center.