WASHINGTON — Climate science and politics too often revert to name calling and bullying, which can get in the way of real work.

That was the only thing House Science Committee members, three scientists who often clash with mainstream science, and a prominent climate scientist could agree to at a contentious hearing Wednesday.

They couldn’t agree on who was doing the name calling, though.

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Republicans and three scientists invited by them to testify accused the mainstream climate scientist, Michael Mann of Pennsylvania State University, and major international science panels of trying to silence researchers who disagree about the magnitude of global warming.

Mann, meanwhile, said he was harassed by people trying to stifle science.

Mann and Republican Rep. Dana Rohrabacher of California both compared the other side’s behavior to repression in the former Soviet Union under Josef Stalin. Mann first raised the Stalin analogy, then Rohrabacher used the comparison four times after that to talk about Mann and other mainstream climate scientists.

“For scientists to call names to beat someone into submission, that’s a Stalinist tactic,” Rohrabacher said.

Former Georgia Tech climate scientist Judith Curry, who often clashes with mainstream science, said she was the victim of “gutter tactics” by “scientists who demonize their opponents.”

She pointed to the way she and Mann have clashed, saying the Penn State professor wrongly called her a climate denier, when she acknowledges that the world is warming and humans play a role. She disagrees with mainstream climate science over implications of global change, how much the world is warming, how much is human-caused, and its certainty.

At first Mann said he didn’t call Curry a denier. But in his written not oral testimony he called Curry “a climate science denier.” Mann said there’s a difference between denying climate change and “denying established science” on how much humans cause climate change, which he said Curry did.

Mann said the chance that humans are causing less than half of the global warming now going on is less than 1 in 10,000, citing an international panel of scientists convened by the United Nations. Curry disagreed, insisting it’s not clear. “I just don’t know how much is human versus how much is natural,” she said.

When pressed by Rep. Barry Loudermilk (R-Ga.) on whether humans are mostly to blame, Mann replied: “I go with physics. You can go with opinion.”

The American Meteorological Society and the American Association for the Advancement of Science both said in email statements to The Associated Press that the overwhelming scientific evidence is clear that global warming is primarily caused by humans.

Republican committee Chairman Lamar Smith of Texas, a lawyer, said, “much of climate science today appears to be based more on exaggerations, personal agendas and questionable predictions than on the scientific method.”

Led by Representative Smith, the House Science Committee opposed the Obama administration’s efforts to regulate the gas, oil and coal industries and reduce carbon emissions.

The panel of three scientists who often clash with mainstream science and Mann was not representative of the peer reviewed research in the field, which overwhelmingly finds climate change to be real, human caused and a problem, Democrats said.

Though climate headlines tend to focus on places like Antarctica, where global warming is rapidly transforming the physical environment, climate change is upending the U.S., too.

Earlier this month, doctors representing 11 top medical societies lobbied in Washington for more aggressive action against climate change, which they said poses an immediate health threat to millions of Americans, citing problems such as widespread heart and lung disease associated with air pollution and increased mortality from floods and other extreme weather events.

The U.S. is already setting twice as many daily heat records as cold records, and research suggests breaking heat records will become more and more routine as man-made climate change worsens.

Retired Adm. David Titley, now a Penn State meteorology professor, said in an email to the AP that scientists should boycott House hearings because it is a “charade” and perpetuates the myth that there is a legitimate scientific debate on the issue.

Democratic Rep. Don Beyer of Virginia asked, “Why can’t we all just get along?” and then answered his own question: “It’s because the stakes are so large.”