The Next Five Years Will Be ‘Anomalously Warm,’ Scientists Predict

Humans are already making the planet warmer.  Now Earth could help speed the process up.

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.

The study mines data from 10 existing climate change models, or simulations, to determine which do the best job of capturing how natural factors are contributing to the planet’s temperature.  Then it projects forward using the same simulations to see how these factors will play out over the next five years.

It’s important to underscore that the result is a forecast based on probability — not a certain outcome.  The study finds a 58 percent chance that Earth’s overall temperature from 2018 through 2022 will be anomalously warm based on these factors, and a 69 percent chance that Earth’s oceans will be.

This includes, for Earth’s oceans, “a dramatic increase of up to 400% for an extreme warm event likelihood” during 2018 to 2022, the study reports.

Already, 2018 is shaping up to be a pretty warm year — although not record-breaking.  For instance, the period from March through May of this year was .87 degrees Celsius (1.57 degrees Fahrenheit) above the planet’s average from 1951 to 1980, making that the third-warmest such stretch in the temperature record, according to NASA’s Goddard Institute for Space Studies.

It’s too early to determine where the year as a whole will rank.  According to NASA, 2016 was the warmest year on record, followed by 2017, 2015, and 2014.

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