The past four years have been the four warmest ever recorded — and now, according to a new scientific forecast, the next five will also probably be “anomalously warm,” even beyond what the steady increase in global warming would produce on its own.
That could include another record warmest year, even warmer than the current record year of 2016. It could also include an increased risk of heat extremes and a major heat event somewhere in the Earth’s oceans, of the sort that has triggered recent die-offs of coral reefs across the tropics.
“What we found is that for the next five years or so, there is a high likelihood of an anomalously warm climate compared to anomalously cold,” said Florian Sevellec, a scientist at France’s National Center for Scientific Research, who co-authored the study published in Nature Communications with Sybren Drijfhout of the University of Southampton in the United Kingdom.
Earth is warming, but this does not mean that every year is warmer than the previous one. Rather, there is an overall warming trend — meaning that each successive decade tends to be warmer than the last — but also plenty of bouncing around among individual years in how hot they get.
One key determinant of a year’s temperature is what scientists sometimes call the climate’s “internal variability,” as opposed to the contribution of human-released greenhouse gases. The new forecast for 2018 through 2022 arises from projecting how this internal or natural variability will play out.
During the global warming “hiatus” during the 2000s, for instance, these internal factors, such as oscillations in Earth’s oceans, helped keep the planet somewhat cooler than it might otherwise have been and blunted the pace of warming — launching a long-running scientific debate and 1,000 political talking points.
Now, though, these same internal factors are poised to do the opposite, says the new research (whose authors also note that their technique can successfully capture the earlier “hiatus”). And assuming that the steady rate of global warming continues, that means already rising temperatures will get an added boost. [Continue reading…]