World’s first year-long breach of key 1.5C warming limit

At the current rate of emissions, the Paris goal of limiting warming to 1.5C as a long-term average – rather than a single year – could be crossed within the next decade.

This would be a hugely symbolic milestone, but researchers say it wouldn’t mark a cliff edge beyond which climate change will spin out of control.

The impacts of climate change would continue to accelerate, however with every little increase in warming – something that the extreme heatwaves, droughts, wildfires and floods over the past 12 months have given us a taste of.

An extra half a degree – the difference between 1.5C and 2C of global warming – also greatly increases the risks of passing so-called tipping points.

These are thresholds within the climate system which, if crossed, could lead to rapid and potentially irreversible changes.

For example, if the Greenland and West Antarctic Ice Sheets passed a tipping point, their potentially runaway collapse could cause catastrophic rises to global sea-levels over the centuries that followed.

But researchers are keen to emphasise that humans can still make a difference to the world’s warming trajectory.

The world has made some progress, with green technologies like renewables and electric vehicles booming in many parts of the world.

This has meant some of the very worst case scenarios of 4C warming or more this century – thought possible a decade ago – are now considered much less likely, based on current policies and pledges.

And perhaps most encouragingly of all, it’s still thought that the world will more or less stop warming once net zero carbon emissions are reached. Effectively halving emissions this decade is seen as particularly crucial.

“That means we can ultimately control how much warming the world experiences, based on our choices as a society, and as a planet,” says Zeke Hausfather, a climate scientist at US group Berkeley Earth.

“Doom is not inevitable.”

Graphics by Erwan Rivault.