The world is on track for between 1.9 and 3.7°C of warming by 2100

Current policies of governments around the world are likely to result in Earth warming by anywhere between 1.9 and 3.7°C by 2100, with potentially more to come in the 22nd century.

“Every year we keep emitting CO2 after 2100 results in higher and higher global temperatures,” says Zeke Hausfather, a climate scientist at Stripe, a California-based software company that invests in carbon-removal technology.

His conclusions are based on a review of more than a dozen studies published in the past five years looking at the implications of current policies. According to these studies, the world is most likely to warm by between 2.3 and 3°C by 2100.

However, these numbers don’t fully take account of the uncertainties about future emissions of greenhouse gases as a result of human actions, and also in how the climate system will respond to those emissions. Including those uncertainties gives a broader range, of 1.9 to 3.7°C.

These numbers reflect the most likely range of scenarios – the 5th to 95th percentiles – meaning there is a small chance of warming of as much as 4.4°C this century with current policies.

The good news is that all the recent studies agree that very high emission scenarios are now unlikely. In these, more than 4°C of warming before 2100 would be the most likely outcome.

This is partly because the worst-case scenarios considered by climate scientists weren’t that plausible in the first place, says Hausfather, but it also reflects real progress in limiting emissions growth, with coal use now plateauing.

If climate policies are strengthened and technological advances continue to exceed expectations, future emissions could be even lower than envisaged in these studies – but this isn’t guaranteed, and the rise of energy-hungry technologies like artificial intelligence could do the opposite.

“It’s definitely possible to envision a world where AI rapidly accelerates and drives near-term emissions increases beyond what we think will happen today,” says Hausfather.

But he doesn’t think AI-related emissions will make a huge difference in the long run. “It’s certainly not in line with rapid emissions reductions, but hard to see it by itself putting us on track for a significantly different end-of-century outcome,” says Hausfather.

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