There Is A Less Than 1 In 40 Chance Global Warming Will Exceed 4 Degrees Celsius

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Most estimates predict climate change will increase average global surface temperatures by 1.5 to 4.5°C (or 2.7 to 8.1°F) by the end of the century, but new research, published this week in the journal Nature, suggests there is a less than one in 40 chance global warming will exceed 4°C. While it looks like we may be saved from the worst-case scenario, these findings should not be used as an excuse to abandon our climate commitments, the researchers warn.

A team of researchers from the University of Exeter and the Centre of Ecology and Hydrology, both UK, have examined fluctuations in annual global temperatures to calculate a more accurate and precise range of warming we can expect to see by 2100.

"Much of climate science is about checking for general trends in data and comparing these to climate model outputs, but year-to-year variations can tell us a lot about longer-term changes we can expect in a physical system such as Earth's climate," co-author Chris Huntingford, a climate modeller from the Centre for Ecology and Hydrology, explained in a statement.

They predict average global surface temperatures will be 2.2°C to 3.4°C higher than they were in pre-Industrial times, slashing the range of potential outcomes by 60 percent. Unfortunately, as you may have noticed, the new range also makes the best-case scenario (a 1.5°C warming) extremely unlikely.

The temperature range comes down to something called equilibrium climate sensitivity (ECS), which is essentially how much the Earth's average surface temperature would increase if the concentration of carbon dioxide (CO2) in the atmosphere doubled and the climate was brought into equilibrium with the new amount. De Visu/Shutterstock

The Paris Agreement set a global target of 2°C warming with a more ambitious aim to prevent average global temperatures from rising above 1.5°C. A leaked report recently revealed that at our current emission levels we will have hit the lower target by the 2040s and now new data seems to suggest we won't succeed with the upper target either. This matters because 2°C above pre-Industrial levels is already considered by a UN-appointed group of scientists, experts, and climate negotiators "inadequate" as a safe limit.

But there is reason to remain positive. 

"Our study all but rules-out very low or very high climate sensitivities, so we now know much better what we need to,” Peter Cox from the University of Exeter, lead author of the study, has pointed out. “Climate sensitivity is high enough to demand action, but not so high that it is too late to avoid dangerous global climate change."

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