Climate

Long-Awaited ‘Jump’ In Global Warming Now Appears ‘Imminent’

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We may be witnessing the start of the long-awaited jump in global temperatures. There is “a vast and growing body of research,” as Climate Central explained in February. “Humanity is about to experience a historically unprecedented spike in temperatures.”

A March study, “Near-term acceleration in the rate of temperature change,” makes clear that an actual acceleration in the rate of global warming is imminent — with Arctic warming rising a stunning 1°F per decade by the 2020s.

Scientists note that some 90 percent of global heating goes into the oceans — and ocean warming has accelerated in recent years. Leading climatologist Kevin Trenberth of the National Center for Atmospheric Research explained here in 2013 that “a global temperature increase occurs in the latter stages of an El Niño event, as heat comes out of the ocean and warms the atmosphere.”

In March, NOAA announced the arrival of an El Niño, a multi-month weather pattern “characterized by unusually warm ocean temperatures in the Equatorial Pacific.”

How much of a temperature jump should we expect? Last month, Trenberth explained to Living on Earth:

Trenberth says it could mean a rise of two- or three-tenths-of-a-degree Celsius, or up to half a degree Fahrenheit. The change could occur “relatively abruptly,” but then stick around for five or 10 years.

I interviewed Trenberth this week, and he told me that he thinks “a jump is imminent.” When I asked whether he considers that “likely,” he answered, “I am going to say yes. Somewhat cautiously because this is sticking my neck out.”

Trenberth explained that it’s significant the Pacific Decadal Oscillation (PDO) “seems to have gone strongly positive” because that is “perhaps the best single indicator to me that a jump is imminent.” During a PDO, he explains, “the distribution of heat in the oceans changes along with some ocean currents.”

The PDO is a “pattern of Pacific climate variability similar to ENSO [El Niño Southern Oscillation] in character, but which varies over a much longer time scale.” While El Niños and La Niñas tend to last only 6 to 18 months, the PDO can remain primarily in one phase for a decade or even longer, as this figure from NOAA’s March “Global Ocean Monitoring” report shows:

Pacific Decadal Oscillation

“The positive phase of PDO [Pacific Decadal Oscillation] index has persisted 8 months since Jul 2014 with PDO index = + 1.6 in Feb 2015.” Via NOAA.

If you compare the PDO chart with the NASA global temp chart at the top, you’ll see that a negative PDO appears to temporarily offset the long-term global warming trend, whereas a positive PDO corresponds to a “catch up” phase (see discussion here). That is one reason, Trenberth explains, that global temperatures seem to look more like a staircase than a ramp (a steadily-rising straight-line or linear trend).

Making things even more confusing, the staircase-shaped rise in temperatures is further modulated by El Niños, which tend to set the record for the hottest years (since the regional warming adds to the underlying global warming trend) and by La Niña years, which tend to be cooler than normal years.

The fact that NOAA projects that the current El Niño could last most of 2015 means we are still on track for what is likely to be the hottest calendar year on record — very possibly beating 2014 by a wide margin (0.1°C).

And record global temps mean extreme temperatures and weather locally. So far this year, “five nations or territories have tied or set all-time records for their hottest temperature in recorded history,” explains meteorologist Jeff Masters.

Antarctica appears to have set its all-time temperature record — 63.5°F (17.5°C) — on March 24 at the northern tip of the Antarctic Peninsula. That is “more than 30°F (17°C) above average.” This was actually part of a heat wave since the Antarctic record it broke was set the day before (63.3°F). Also in March, the Chilean desert was deluged by “over fourteen years of rain in one day.”

It was the hottest February on record in California, a full 1°F higher than the second-warmest February on record. And that followed California’s driest January ever recorded. These type of records are not good news.

“So it is a bad year for the Earth and an equally bad year for the politicians, talk show radio ‘scientists’, climate-denial funders, and second rate scientists who told us not to worry,” as climate expert Professor John Abraham told me. “They told us global warming had stopped nearly two decades ago. The problem is, science and climate change marched forward. Perhaps next time we will believe the real scientists.”

Indeed it will be a very bad year for the Earth and for climate science deniers if 2015 proves to be the beginning of the long-awaited temperature jump.

The last time global temps jumped sharply (see top chart), it was during an extended period of positive PDO, from 1992 and 1998. The super El Niño in 1998 at the end of that period set a new global temperature record by a wide margin. That was a high bar for subsequent years to match, which cherry-picking climate science deniers used — with some success — to persuade conservative politicians and media outlets that global warming had paused or slowed down. In fact we have merely been in an extended period of the PDO negative phase, with only occasional switches to a mild positive phase. And that, coupled with some recent La Niñas, gave an appearance of a short-term slowdown in warming in some datasets.

But the NASA chart at the top makes clear there has in fact been no slowdown in warming. Indeed the March study, “Near-term acceleration in the rate of temperature change” makes clear the only “pause” there has been was in the long-expected speed-up of global warming. The rate of surface warming should have started to accelerate in the past decade, rather than stay fairly constant.

The authors warned that, by 2020, human-caused warming will move the Earth’s climate system into a regime of rapid multi-decadal rates of warming. It projected that within the next few years, “there is an increased likelihood of accelerated global warming associated with release of heat from the sub-surface ocean and a reversal of the phase of decadal variability in the Pacific Ocean.”

That would be Trenberth’s imminent jump. And it may be starting now.