UNITED NATIONS — The landmark Paris agreement on climate change will enter into force on Nov. 4, after a coalition of the world's largest polluters and small island nations threatened by rising seas pushed it past a key threshold on Wednesday.

President Barack Obama hailed the news as “a turning point for our planet,” and U.N. Secretary-General Ban Ki-moon called the agreement's strong international support a “testament for the urgency of action.” Katharine Hayhoe, a climate scientist at Texas Tech, called it: “A moment of bright hope in the increasingly discouraging landscape of climate science.”

U.N. deputy spokesman Farhan Haq said late Wednesday that the European Union and 10 countries deposited their instruments of ratification on Wednesday. The percentage of emissions they account for topped the 55 percent threshold needed for the treaty to take effect, he said.

Haq said the 10 countries were Austria, Bolivia, Canada, France, Germany, Hungary, Malta, Nepal, Portugal and Slovakia.

“Global momentum for the Paris Agreement to enter into force in 2016 has been remarkable. What once seemed unthinkable is now unstoppable,” Ban said in a statement issued from Europe.

A U.N. website said that as of Wednesday afternoon 73 of the 197 parties to the treaty, accounting for 56.87 percent of the world's greenhouse gas emissions, have deposited their instruments of ratification.