Think of the irony, if the push that finally makes the United States a world leader in combating climate change comes from ... China.

Of course, President Xi Jinping first would have to follow through on the promises made in his new carbon-cutting accord with President Barack Obama, which commits China to launching a cap-and-trade program for greenhouse gases within his country — similar to what California has now — and putting up $3.1 billion to help developing countries in their efforts against climate change.

Obama and the Environmental Protection Agency have been trying to do the right things, especially with the Clean Power Plan that was unveiled in August.

Under that initiative, states must reduce carbon emissions from power plants, the single biggest source of greenhouse gases, to a level in 2030 that is 32 percent below the plants’ 2005 emissions. Most of that would be achieved by moving from coal to renewable energy or gas.

Republicans have tried to kill the plan, though, largely by arguing that global warming is a global problem and that the U.S. should not commit to new restrictions unless China, the biggest emitter, does the same.

The new accord steals that argument from them — Xi pledged to halt the growth of greenhouse gas emissions by no later than 2030 — and positions China and the U.S. to enter the Paris climate talks later this year as committed leaders.

And it marks a huge reversal in China’s rhetoric.

Two decades ago, China was arguing that it was one of the developing nations that should be given a pass on reducing greenhouse gases; indeed, at that time, the U.S. was the leading climate polluter. China took on the dubious title in 2006.

China has more motivation to make good on its climate promises than it does on Xi’s high-profile cybersecurity deal with Obama. The country has a practical interest in reducing climate pollution because the same pollution from dirty coal has been choking its skies and killing its people.

An August study found that dangerously sooty air enveloped many parts of China, and that in Beijing, it had reached such alarming levels that simply breathing was the equivalent of smoking two packs of cigarettes a day. China has closed several coal plants in the Beijing area, and announced in March that it would close the last one next year.

In other words, Xi has good reasons to be willing to sign a binding global agreement in Paris, which would be the true sign of international cooperation. Such willingness could go a long way toward preventing a repeat of the disappointing 2009 Copenhagen climate talks, which resulted in weak commitments and dropped promises.

The evidence of climate change has become far more visible in the past six years; there is no time for another failed climate summit.