Last week, President Barack Obama and China’s President Xi Jinping announced that their two countries would sign the global climate accord on April 22. Senior U.S. officials noted that the commitment to cut carbon emissions by the world’s largest greenhouse gas polluters will compel other countries to formally join the agreement. “Our hope is that as that process proceeds, you will see growing momentum toward having this agreement enter into force early and swiftly,” said Brian Deese, a senior adviser to Mr. Obama.

The climate deal, completed late last year in Paris, was forged by more than 190 nations, and commits nations to reduce greenhouse gas emissions and mitigate climate change beginning in 2020. However, in order for the agreement to enter into force, it requires official ratification beginning in April by legislatures from at least 55 countries representing 55 percent of the world’s emissions. Mr. Deese further commented that the U.S.-China announcement “will help build the critical momentum that we all saw coming out [of] Paris.”

Although the U.S. faces legal challenges to meet its international commitments at home, the joint announcement is another monumental step in a worldwide movement toward curbing climate change.