The only remaining countries that emit more than Brazil, but have not yet ratified, are Russia (7.5 percent of emissions), India (4.1 percent), Japan (3.79 percent), and Germany (2.56). If all four of those countries also ratified this year, the agreement would easily enter into force.

But other countries could also contribute to tipping the world into an officially active Paris regime, including Canada (1.95 percent), South Korea (1.85 percent), Mexico (1.7 percent), the U.K. (1.55 percent), Indonesia (1.49 percent), South Africa (1.46 percent) and Australia (1.46 percent).

Ban Ki-moon, secretary general of the United Nations, has called world leaders to the U.N. headquarters on the 21st of this month for a ratification ceremony for the Paris agreement. Some 175 have already signed, and along with the recent move by the U.S. and China, Brazil’s move just considerably increased the likelihood that there will be something to celebrate.

“It’s an important signal, and continues the momentum going into next week in New York,” said Alden Meyer, director of strategy and policy at the Union of Concerned Scientists.

September 12, 2016