President-elect Donald Trump has called climate change a hoax perpetrated by the Chinese and during his electoral campaign, also said he would “cancel the Paris Climate Agreement” that went into force last week. In a statement Wednesday, former Vice President and climate activist Al Gore appealed to Trump to honor the agreement that many experts consider is not enough to stop a catastrophic rise in Earth’s temperature.

In his statement, published on the website of his foundation, the Climate Reality Project, Gore said: “Last night President-elect Trump said he wanted to be a president for all Americans. In that spirit, I hope that he will work with the overwhelming majority of us who believe that the climate crisis is the greatest threat we face as a nation. I wish him well in these efforts and intend to do everything I can to work with him and his administration to ensure that our nation remains a leader in the global effort to meet this challenge.”

With the exception of China, the U.S. is the world’s largest emitter of greenhouse gases and a lot of Trump’s electoral rhetoric, if it were to come true, would increase the country’s contribution to gases that warm the planet. He wants to increase offshore drilling for fossil fuels and natural gas production, scrap the Environmental Protection Agency completely and put a stop to what he called “wasteful” spending on climate change mitigation by the federal government.

Taking on the economic angle, Gore added in his statement: “The market forces driving the transition to a sustainable economy simply will not be slowed. … Today, without regard to last night’s outcome, we must turn our focus to making the promises of the Paris Agreement a reality by embracing the forces that are already working to grow our economy and transform our energy future.”

The U.S. contributes about 13 percent of global greenhouse emissions and if it were to pull out of the Paris accord, even if not on paper but in practice, other polluters — both large and small — would likely follow suit. If that were to happen, Earth would hurtle faster toward a disaster.

Gore’s message ended on a hopeful, yet cautious, note.

“A sustainable future is in sight — but we cannot take it for granted. We must fight for the future we all believe in. Now, more than ever, our planet needs us — and I’m inspired by the knowledge that we’ll take the path forward together.”