WASHINGTON — Republican lawmakers critical of global efforts to battle climate change said Tuesday they would head to the Copenhagen summit to undercut President Obama’s promises of U.S. action. They vowed to highlight a scandal over leaked emails from leading climate scientists, which they said backed their suspicions that the global-warming threat was overblown and too costly to counter.

“I will not be one of the sycophants that says climate change is the biggest problem facing the world and we need to do all these draconian things that cost jobs,” said Rep. Joe Barton (R-Texas), the top Republican on the House Committee on Energy and Commerce.

Obama plans to head next week to the 192-nation summit in the Danish capital to promise U.S. leadership and pledge that the world’s largest economy will cut carbon emissions blamed for global warming — a plan he says will create jobs by creating a new green economy. While his pledges are below those of the European Union and Japan, Obama has sharply reversed course from Bush, a diehard opponent of the Kyoto Protocol.

Rep. James Sensenbrenner (R-Wis.), who will head the Republican House delegation to Copenhagen, said that Obama should “lower the rhetoric” on what the United States will do under the next global agreement. “America lost a lot of credibility when then-vice president Al Gore promised the international community in Kyoto something that he knew could never be passed by the Congress,” Sensenbrenner said. “I would hope that President Obama will not repeat Al Gore’s mistake.”

The House of Representatives in June narrowly passed a plan to cut emissions by 17 percent by 2020 from 2005 levels, the same figures Obama is taking to Copenhagen. The Senate has delayed similar legislation until next year, but its coauthor, John Kerry (D-Mass.), has vowed to see it through and has won cooperation from at least one Republican in the chamber, Lindsey Graham (R-S.C.).

In an apparent bid to show it has the ability to match words with deeds, the Obama administration on Monday empowered the Environmental Protection Agency to regulate carbon dioxide as a pollutant, regardless of the debate in Congress.

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