When major new climate change scenarios are released, there’s always strong interest.

These scenarios lay out what our future climate will look like, depending on how fast we act to cut emissions.

But what was surprising about the seven new scenarios announced last week was that US President Donald Trump took an interest.

Why? Because a high-emissions scenario – known as RCP8.5 and its successor SSP5-8.5 – had been removed.

Under these worst-case scenarios, nations would make no effort to cut emissions and expand fossil fuel use. By 2100, carbon dioxide levels would almost triple, to 1135 parts per million and the world would be around 4.5 degrees hotter than the pre-industrial period.

The climate scientists responsible for laying out the range of possible futures removed the RCP8.5 scenarios for a very good reason. Although often slow and incomplete, our efforts to tackle climate change have made a tangible difference.

We have averted the worst climate future once thought possible.

The job is far from done. Emissions are at record highs and global warming is speeding up.

But the removal of this high-emissions scenario isn’t, as Trump and other climate sceptics have claimed, a sign of failed modelling or that climate change was a hoax. It’s a sign the expansion of solar, wind, electric vehicles and batteries have slowed emissions growth.

Under the worst-case scenario, the world would warm about 4.5 degrees by 2100. Photo: IPCC

How are these scenarios made?

Many climate impacts are becoming evident after about 1.4 degrees........

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