Global warming triggered by anthropogenic activities and a natural surge in Earth’s surface temperatures will make the next four years exceptionally hot, says a study.

The unusually hot weather will primarily be because of the natural variability of Earth’s climate rather than global warming alone, said Florian Sevellec, a physical oceanographer with the University of Brest in France and the main author of the study that appeared in the journal Nature Communications .

The likely increase due to the natural variability of Earth’s climate alone — that is, the variability that is not associated with long-term global warming — is +0.02°C for 2018, +0.03°C for 2018-19, and +0.01°C for 2018-22, says Sevellec.

“The natural variability puts us in a warm phase that superimposes a warm anomaly approximately twice as big as the effect of global warming on its own,” he told BusinessLine via email. In comparison, global warming raises the temperature on an average by 0.01°C a year.

The forecast comes from a new probabilistic forecasting (PROCAST) model of the natural variability in Earth’s climate developed by Sevellec and his collaborator from the University of Southampton in the UK, Sybren Drijfhout.

Climate prediction

According to Sevellec, though scientists have made some important breakthroughs in understanding and modelling the climate system, these are yet to be transferred into an ability to predict the climate from year to year. As a result, scientists are still not in a position to efficiently predict the climate a few years in advance.

The new model, however, stands out. It combines various climate models, removing the dependence on a single model, leading to better accuracy. Besides, the model dramatically improves the speed of predictions: a forecast that previously took a high-powered supercomputer a week can now be done on a laptop in a few hundredths of a second.

Significantly, the scientists have been able to prove the PROCAST model’s effectiveness by running a retrospective test on the 1998-2013 global warming hiatus, which it accurately predicted.

However, one major drawback of the system currently is that it cannot forecast the temperature on a regional scale. “Regional forecasts are not possible at this stage. It is something we are working on. But it is an important challenge,” said Sevellec.

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