The legendary physicist Stephen Hawking is celebrating his 75th year on this planet with a grand cosmology conference in his honour held this week at the University of Cambridge, UK.

Ahead of this event Hawking spoke to BBC News, sharing his grave disappointment and concern with the direction Earth's climate is taking, especially in light of US President Donald Trump's decision to pull out of the Paris climate agreement.

"We are close to the tipping point where global warming becomes irreversible," Hawking told BBC's Pallab Ghosh.

"Trump's action could push the Earth over the brink, to become like Venus, with a temperature of two hundred and fifty degrees, and raining sulphuric acid."

Now, the famous scientist was certainly being a touch hyperbolic here, as is wont for someone who has spent his career in the public eye, making headlines with every new discovery and popular science book.

While our planet is without a doubt undergoing the effects of anthropogenic climate change, the kind of runaway greenhouse gas effect that is actually happening on Earth's 'evil twin' Venus is not really our most immediate concern.

A 2013 study did predict that a runaway greenhouse effect on Earth "could in theory be triggered by increased greenhouse forcing", but added that, based on the available data, emissions wouldn't be enough to cause this.

But even if we're not about to be melted down to our skeletons in sulphuric acid rain, Hawking still has a point.

"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," he added.

It's already too late to prevent the full effect that climate change is going to have on our planet. Over the course of the 20th century, Earth's average temperature increased by about 1 degree Fahrenheit (0.6 degrees Celsius), which may not sound like much, but actually amounts to huge environmental changes.

As that average temperature climbs even higher, temperature anomalies are going to swing all over the shop, with weather extremes hot on their heels. There will be more hurricanes, more heat waves, more record temperatures, loss of sea ice and changing seasonal patterns everywhere.

For people who accept the reality of scientific consensus on climate change, it's now become a question of how best to mitigate all these effects, and the Paris Climate Agreement was the result of 195 countries coming together to say "let's finally do this".

When a major world power decides to renege on these international efforts, it's natural to feel pessimistic - although Professor Hawking has seemed to be pessimistic about humanity's prospects for a while now.

Just last month he reiterated that if humans are to persist as a species, our only choice is to explore other planets as quickly as possible, so that we can one day travel beyond our own Solar System.

"Spreading out may be the only thing that saves us from ourselves. I am convinced that humans need to leave Earth," Hawking said at a science festival in Norway.

The leap to a backup plan off world is a lot harder than fixing this one Goldilocks planet we've got. But at least for worst case scenario planning, it's good to know NASA, Japan, and China are all working on new lunar missions as a stepping stone to putting spaceboots on Mars.

You can read the full interview with Stephen Hawking over at BBC News.