Renowned physicist and best-selling author Stephen Hawking died Wednesday morning in his Cambridge, England home at the age of 76.

Hawking had become an iconic figure because of his scientific brilliance, his popular writings, and the grace and humor with which he waged a multi-decade fight against ALS, amyotrophic lateral sclerosis, a neuromuscular disease also known as Lou Gehrig’s disease.

As physicist Michio Kaku, told the New York Times: “Not since Albert Einstein has a scientist so captured the public imagination and endeared himself to tens of millions of people around the world.”

In recent years, Hawking used his status as a legendary scientist to warn the public about the dangers posed by a number of catastrophic threats to humanity, particularly global climate change.


In 2016, he warned that climate change was the gravest threat facing humanity. That September he also joined 377 members of the National Academy of Sciences in signing an open letter that began, “Human-caused climate change is not a belief, a hoax, or a conspiracy. It is a physical reality.”

The letter warned about a Trump victory, explaining that “it is of great concern that the Republican nominee for President has advocated U.S. withdrawal from the Paris Accord” and that “such a decision would make it far more difficult to develop effective global strategies for mitigating and adapting to climate change.”

In July 2017, Hawking told the BBC that President Trump’s climate policies could permanently destroy the Earth’s livable climate.

“We are close to the tipping point where global warming becomes irreversible,” he explained. “Trump’s action could push the Earth over the brink, to become like Venus, with a temperature of 250º” Celsius (482°F).

While “climate change is one of the great dangers we face,” the good news, Hawking noted, is that “it’s one we can prevent if we act now.” But the tragedy is that “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.”

Was Hawking correct that humans could, in a worst-case scenario, create a truly runaway greenhouse effect?

A 2013 Nature Geoscience study concluded: “A runaway greenhouse could in theory be triggered by increased greenhouse forcing, but anthropogenic emissions are probably insufficient.” So, no, it’s not very likely.


Of course, human civilization would likely collapse well before we had Venus-level warming. A mere 4°C (7°F) warming would lead to “devastating” impacts such as “declining global food stocks,” the World Bank has warned.

If we continue with the kind of business-as-usual emissions of carbon pollution that the Trump administration has embraced, then we risk warming far beyond that magnitude and unimaginable devastation for centuries.

The good news is that the rest of the world is committed to meeting its Paris carbon emission reduction pledges. But we are fast approaching irreversible tipping points, as Hawking warns, so Trump’s pro-pollution policies might well be enough to ensure that we do cross them.

Hawking became famous for his study of the past, and his 1998 book, A Brief History of Time: From the Big Bang to Black Holes,” which has sold more than 10 million copies. But it’s his warnings about the future we most need to heed today.