The world’s two biggest emitters of carbon dioxide have reached an agreement on emissions reductions. The United States and China announced the deal yesterday, in a move that’s already being praised by environmental groups and panned by Congressional Republicans.

This agreement marks the first-ever move by China to set a ceiling on the country’s carbon dioxide emissions. Greenhouse gases from sources like fossil fuel-fired power plants are contributing to climate change, and scientists have warned that the planet is warming at an alarming rate. The latest report from the United Nations Intergovernmental Panel on Climate Change recently called for drastic steps: a reduction of 40 to 70 percent in greenhouse gas emissions by 2050, and total elimination by 2200.

The new China-U.S. deal doesn’t go that far, but it does lay out clear reduction targets.

Chinese President Xi Jinping said the country would peak its emissions by 2030, if not sooner. He said to meet that goal, China would rely on renewable energy sources like solar and wind, and those sources would make up 20 percent of the country’s energy portfolio by 2030.

Here’s how the White House described the U.S.’s part of the pledge:

After 2020, the United States will reduce its net greenhouse gas emissions to 26-28% below 2005 levels by 2025. This goal is both ambitious and achievable, grounded in an intensive analysis of what actions can be taken under existing law, and will double the pace of carbon pollution reduction in the United States from the pre-2020 period. It also means the United States is doing its part to contain warming to 2 degrees Celsius, though achieving that global outcome will require global ambition and commitments from all economies.

One of the common complaints from Republicans and many coalfields politicians has been that action by the U.S. to slow the pumping of CO2 into the air—like the EPA’s proposed rules limiting greenhouse gas emissions from power plants—is needlessly harmful to the American economy. They say even if climate change is happening (a point on which nearly all climate scientists agree), that U.S. action won’t make a difference unless other major players like China act, too.

“No industrialized country in the world is going to do this,” said Kentucky Sen. Mitch McConnell during his debate with Democrat Alison Lundergan Grimes last month on KET. He was talking about the proposed carbon dioxide regulations, and cited all the coal use by countries like China, India and Australia.

“Even if you felt this was a cause worth pursuing, our doing it by ourselves is going to have zero impact,” he said.

Now China has signaled willingness to play ball, but McConnell wasn’t impressed.

Here’s a statement his office sent out this morning:

“Our economy can’t take the President’s ideological War on Coal that will increase the squeeze on middle-class families and struggling miners.  This unrealistic plan, that the President would dump on his successor, would ensure higher utility rates and far fewer jobs. The President said his policies were on the ballot, and the American people spoke up against them. It’s time for more listening, and less job-destroying red tape. Easing the burden already created by EPA regulations will continue to be a priority for me in the new Congress.”

He elaborated later in a photo op with Republican senators-elect:

I was particularly distressed by the deal apparently [Obama]’s reached with the Chinese on his current trip, which as I read the agreement requires the Chinese to do nothing at all for 16 years while these carbon emission regulations are creating havoc in my state and other states around the country.

The question remains how the U.S. will meet these new goals. President Obama wasn’t clear, saying the goal was achievable and could be met by speeding up progress that’s already underway. But NPR White House Correspondent Scott Horsly said whatever the White House pursues probably won’t involve Congress.

“The White House thinks the U.S. can meet these targets without new legislation,” he said. “That’s important, because after last week’s midterm elections, we’re not likely to see any new climate legislation coming out of Capitol Hill.”

From statements he’s made, it’ll be a challenge to continue the environmental regulations that are in the works under presumptive Majority Leader McConnell, let alone passing new ones.