As the party shifted against the Democratic climate agenda in 2009, Republicans turned abroad, arguing that it would be pointless for the U.S. to adopt regulations that could impose higher costs on consumers if leading global polluters like China and India did not follow suit. (Mother Jones has put together a good mashup of Republican statements to this effect.) By striking a pact with China, Obama essentially has called their bluff, and an explicit aim of the accord is to spur other nations to make similar agreements at a global conference next year in Paris.

With an eye toward those past statements, two senior Republicans on the House Energy and Commerce Committee, Representative Fred Upton and Representative Ed Whitfield, focused on the parameters of the deal, in which China is promising merely to stop its annual increase in carbon emissions by "around 2030" while the U.S. is committing to steep reductions for itself. "America's pain is truly China's gain," Upton and Whitfield said, "and if the president has his way, Americans will continue to be at a disadvantage for many years to come. The Chinese are promising to double their emissions while the administration is going around Congress to impose drastic new regulations inhibiting our own growth and competitiveness."

To some extent, the shift in political momentum on climate change had its roots in the economic collapse of 2008, when in the minds of many Americans, the short-term costs of action came to outweigh the long-term benefits to the environment. And it was a lack of support from Democrats in the Senate that prevented the House-passed cap-and-trade bill from becoming law.

But now the upper ranks of the Republican Party are united in opposition to any mandatory carbon caps, and they have made EPA climate regulations a top target in 2015. The Obama administration, of course, saw all of this coming, which is why you won't see the word "treaty" anywhere in the climate agreements either with China or other nations. The deal does not require Senate ratification, but it is more vulnerable to undoing from Obama's successor, as when President George W. Bush pulled out of the Kyoto Protocol upon taking office in 2001.

Tuesday's accord lends a measure of global prestige to a president who has been diminished at home. But Obama knows that when he returns from Asia, he'll quickly have to get back on climate-change defense as he confronts resurgent Republicans on Capitol Hill.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.