As President Xi Jinping’s special envoy prepares to sign the Paris Agreement on climate change on April 22 in New York City, international environmental groups are praising China for significantly increasing the chances that the agreement can take effect before the 2020 deadline.

China will sign the historic climate agreement with the United States — the two countries account for 38 percent of the world’s greenhouse gas emissions — and about 160 other nations.

The signing of the agreement, which was reached in December, will take place at United Nations headquarters on April 22, which is also International Mother Earth Day. The president’s special envoy, Vice-Premier Zhang Gaoli, is also scheduled to meet with UN Secretary-General Ban Ki-moon and some state leaders about further cooperation.

After the signing ceremony, China will begin the legal process to join the agreement and will ratify it as soon as possible, said Su Wei, director of the Department of Climate Change of the National Development and Reform Commission.

Countries that don’t sign the agreement on April 22 will still have a year to do so. Countries that sign must then have the agreement ratified by their own legislative procedures.

At least 55 countries, representing at least 55 percent of global greenhouse gas emissions, must ratify the agreement before it can take effect.

The agreement aims to hold the increase in the global average temperature to less than 2 degrees Celsius above preindustrial levels and to work toward limiting the increase to 1.5 C.

China and the US have announced that they will join the agreement this year. There are indications that more countries will also join this year.

“These signals significantly increase the chance that the agreement will enter into force this year,” said Jake Schmidt, director of the International Program at the Natural Resources Defense Council, which is based in New York City.

Eliza Northrop, a researcher at the World Resources Institute, also said the signing by China and the US will give a major boost to efforts to reach the threshold for entry into force.

“It is reasonable to think the entry into force would happen in 2017,” she said. “But given the varying timelines for countries to complete their domestic approval processes, the timing of entry into force is uncertain.”

Samantha Smith, leader of the World Wildlife Fund, said more efforts are urgently needed for the climate change meeting next month in Bonn to pick up on issues where the Paris meeting left off.

“We hope that leaders will not only send strong signals to their negotiators, but even instruct them, about the key elements needed to give life to the Paris Agreement.”