Renowned physicist Stephen Hawking warned Sunday that President Donald Trump’s decision to pull the United States out of the Paris climate accord last month could result in temperatures on Earth rising as high as those on the surface of Venus, the second-closest planet to the sun.

Ahead of a celebration for his 75th birthday at Cambridge University, Hawking also told BBC News that he fears the best hope for human civilization is to colonize other planets.

“We are close to the tipping point where global warming becomes irreversible. Trump’s action could push the Earth over the brink, to become like Venus, with a temperature of 250 degrees and raining sulfuric acid,” he said.

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Hawking also said, “Climate change is one of the great dangers we face, and it’s one we can prevent if we act now. By denying the evidence for climate change and pulling out of the Paris climate agreement, Donald Trump will cause avoidable environmental damage to our beautiful planet, endangering the natural world, for us and our children.”

Trump announced on June 1 that the U.S. would no longer participate in the deal to cut global carbon emissions but would seek to renegotiate the 195-nation accord.

Almost immediately after Trump’s remarks, leaders from other top economic powers, like Germany, France and Italy, chastised Trump for the decision, called the accord “irreversible” and vowed no new negotiations, according to The New York Times.

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Hawking said that human nature will inevitably serve as a hindrance to any real, profound actions taken to combat the Earth’s rising temperatures and that he believed humanity’s time on the planet was running out.

“I fear evolution has inbuilt greed and aggression to the human genome,” Hawking said. “There is no sign of conflict lessening, and the development of militarized technology and weapons of mass destruction could make that disastrous. The best hope for the survival of the human race might be independent colonies in space.”

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A new study by the American Meteorological Society found that satellite data was consistent with temperatures taken on the Earth’s surface and showed the planet is getting hotter and hotter as time goes by, according to The Washington Post.

The study, aimed at debunking the claims made by climate change deniers, found there wasn’t much discrepancy between temperatures measured high above or on the Earth’s surface.

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