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Today, President Donald Trump will announce his decision on whether to pull the United States out of  the landmark Paris climate agreement that was signed in 2016 with more than 190 countries on board. Members agreed to reduce carbon emissions and to keep global warming to below 2 degrees Celsius, starting no later than 2020.

The leaders in that agreement were the U.S. and China, who together produce close to 45 percent of global emissions.

When China agreed to sign on to the Paris accord, it was not only hailed as a breakthrough in policy coordination, but as a sign that China was getting serious about the enormous size of its carbon footprint and was ready to commit to protecting against the effects of climate change.

China, the number one producer of greenhouse gases, is burning close to half of the world's coal supply each year. They pledged to peak carbon emissions by 2030 or sooner, an ambitious goal for a country of more than 1.3 billion people. But according to a recent report from Climate Action Tracker both China and India — two nations once viewed as roadblocks in the global fight against climate change — are on track to meet that goal before the deadline.

If the U.S. does decide to pull out of the agreement, it appears that China and India will be the world leaders to fill the void. Here to explain is Joanna Lewis, an associate professor of science, technology, and international affairs at Georgetown University, who has written widely about China's role in climate change and is author of "Green Innovation in China." Also weighing in is Andrew Light, a distinguished senior fellow in the global climate program at the World Resources Institute. He's also a former senior adviser and India counselor to the U.S. Special Envoy on Climate Change at the State Department.