I can understand when pop-scientists like Bill Nye spout scientific silliness. But complete nonsense coming from Stephen Hawking? Really?
In this video, Stephen Hawking claims that Trump withdrawing the U.S. from the Paris Accord could lead to the Earth being pushed past a tipping point, with Venus-like 250 deg. C temperatures and sulfuric acid rain.
The trouble with this statement is that no reputable climate scientist would claim such a thing. The reason is that Venus has about 220,000 times as much carbon dioxide in its atmosphere as does Earth.
Meanwhile, human civilization will have trouble simply doubling (2x) our atmospheric CO2 concentration (it’s taken about 100 years to increase it by 50%, which is half way to doubling).
Since we don’t know what our future energy mix will be in 50-100 years, it’s not obvious we will even reach “2XCO2”.
So, how could we possibly get from 2x to 220,000x?
Not even if we wanted to.
Venus is a very different planet. Venus has 93x as much atmosphere as Earth, and it is almost 100% CO2. The CO2 concentration in our comparatively thin atmosphere is only 0.04%.
I have no idea where Hawking ever got such a wild idea. Apparently, he had his audience in tears with his dire predictions.