The U.S. and China announced a joint plan to reduce carbon emissions on Nov. 11, ahead of next year’s U.N. climate change summit in Paris.

China’s decision to move with U.S. President Barack Obama in reining in greenhouse gases jump-starts the global fight against climate change, removing an excuse for inaction in developing nations.

Chinese President Xi Jinping broke ranks with India, Brazil and South Africa in setting a target for the first time to reduce fossil-fuel emissions by 2030. Obama pledged to double the pace of cutting carbon dioxide starting in 2020.

The U.S. and China are the biggest polluters, responsible for almost 40% of greenhouse gas emissions.

“This unrealistic plan, that the president would dump on his successor, would ensure higher utility rates and far fewer jobs,” Mitch McConnell of Kentucky, the Republican leader in the Senate, said in a statement from his office in Washington.

Environmental groups were also skeptical the diplomatic breakthrough will be enough to hold global warming to 2 degrees Celsius since the industrial revolution, the guideline endorsed by world leaders as the maximum that can be safely endured.

The new targets mean that emissions in the U.S. and China will converge by 2030 at 12 tons per capita, more than double the global average today, according to India’s Centre for Science and Environment.

The deal, announced by Obama and Xi in Beijing, is significant for the U.S. because it starts to remove one of the reasons Congress in Washington had not to act on climate.

The Senate opposed then-President Bill Clinton’s effort to ratify the 1997 Kyoto Protocol because it set limits for industrial nations only and left none for developing nations including China and India.

Obama’s attempts to pass cap-and-trade legislation to limit carbon emissions during his first term were blocked by Congress. This time around, Obama plans to bypass Congress using existing legislation and his regulatory powers, the White House said.

To date, developing countries have resisted setting pollution targets, saying richer nations that created the problem should move first. India, Brazil and South Africa have called for the UN to consider the historical emissions of all nations in fixing how much each country should act. Even so, they’ve agreed to come up with contributions to a new deal by the end of March.

The UN-led process underway envisions all nations setting pledges in the first quarter. That will lead to a deal in Paris in December 2015, which will take affect starting in 2020, when the current limits in the Kyoto Protocol lapse. The European Union has promised to cut emissions by 40% by 2030 from 1990 levels, the most ambitious program announced to date.