But Hawking also had much to say about the future, recently turning his attention to climate change. In his last years, he used his platform to warn us that human activity was irreversibly damaging the planet and urged us to take action.

“We are close to the tipping point where global warming becomes irreversible,” Hawking said during an interview last year with the BBC.

He didn’t stop there. He then proceeded to denounce US President Donald Trump’s decision to withdraw from Paris climate agreement. “Trump’s action could push the Earth over the brink, to become like Venus with a temperature of 250 degrees and raining sulphuric acid,” Hawking said.

Sounds ominous, right?

But Hawking’s words might not be mere premonition of a distant future. They are looking more and more likely to become a reality sooner than expected.

The past four years has been the hottest period on record, with NASA reporting that 2017 was the second-hottest year in recorded history, while scientists from the US National Oceanic and Atmospheric Administration (NOAA) saying that it was the third-warmest.

And the risk of such hot weather has already increased fivefold from the past, when it occurred once in a thousand days, according to a 2015 study by climatologist Dr. Erich Fischer at the Institute for Atmospheric and Climate Science in Zurich.

And things could get much worse if we go beyond the tipping point of a temperature rise of 1.5 degrees Celsius.

Fischer’s study shows that the risk of hot weather will double again at a 1.5-degree increase in temperature, and double once more when we reach a 2-degree rise.

Failure to maintain the global temperature rise could usher in a new climate regime.

According to a 2016 study published in Earth System Dynamics, 2-degree rise in temperature would lead to a 10-centimeter-rise in global sea levels by 2100 and longer heat waves, which would threaten virtually all tropical coral reefs in the world.

Such an extreme rise in sea level could permanently inundate many coastal regions and islands.

And that is just the tip of the iceberg. Other estimates predict an ice-free Arctic in the summer, the destruction of the Amazon rainforest, and the melting of the Siberian tundra to release planet-warming methane from its frozen depths.

And there’s not much time left, either. Delaying the efforts to reduce fossil fuel emissions could lead to 153 million premature deaths across the globe from air pollution this century, according to a recently released study led by Duke University in North Carolina.

So the next big question is, can we keep global warming within 1.5 degrees?

The answer, unfortunately, is that this would be extremely unlikely, according to a draft UN report from the International Panel on Climate Change (IPCC), the world’s leading authority on climate change.

“There is a very high risk that under current emissions trajectories and current national pledges, global warming will exceed 1.5 degrees Celcius above preindustrial levels,” the report reads.

It also states that the 66 percent likelihood of holding warming below 1.5 degrees without overshooting is already out of reach.

Not all hope is lost, though. The report points out that limiting global warming to 1.5 degrees is still possible, but it will require a rapid phaseout of net global carbon dioxide emissions and deep reductions in non-CO₂ drivers of climate change, such as methane.

With the deadline for our planet’s fate drawing near, chief executive Andrew Higham of Mission 2020 – a collaborative initiative that aims to drive down global emissions for full decarbonization by 2050 – said that policymakers had to act now, and fast.

“What we need is to move fast. We have the technology, so there’s nothing stopping us in our pathway to 1.5,” said Higham, who was in charge within the United National Framework Convention on Climate Change (UNFCCC) for drafting and delivering the Paris Agreement. “It seems like a small number, but it makes a really huge difference to vulnerable communities."

Hawking may have left the Earth and all of its problems, but the rest of humanity is still here. It's high time we took Hawking's words seriously. (kes)

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Born in Indonesia, Hans Nicholas Jong is a Jakarta-based environmental journalist. Before joining Mongabay.com in 2017, Hans worked for The Jakarta Post for five years. Having covered a wide range of issues from the elections to the economy, Hans found his passion in the environment. Being surrounded by people who dedicated their lives to protecting the environment fueled Hans’ interests and desire to write about the complexities of environmental issues in Indonesia and other countries.

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