NASA oceanographer Bill Patzert called the intensifying El Niño, “Godzilla.” A NOAA research scientist called it “Bruce Lee” in July, and, by August, she said that what’s coming is “Supercalifragilisticexpealidocious.”
Whatever you call it, the short-term burst of regional warming in the tropical Pacific (from the monster El Niño) combined with the strong underlying long-term global warming trend means that 2015 will easily be the hottest year on record — blowing past the record just set in 2014. And if the global temperature pattern repeats that of the last super El Niño (1997–1998), then 2016 could well top 2015 record. Here’s why.
First, as a 2010 NASA study explained, the 12-month running mean global temperature tends to lag the temperature in the key Niño 3.4 region of the equatorial Pacific “by 4 months.” El Niño (and La Niña) are typically defined as positive (and negative) sustained sea surface temperature anomalies greater than 0.5°C across the central tropical Pacific Ocean’s Nino 3.4 region. More details here.
Second, in its monthly ENSO (El Niño Southern Oscillation) update released last week, NOAA reported, “All multi-model averages predict a strong event at its peak in late fall/early winter.” NOAA’s National Centers for Environmental Prediction (NCEP) went on to explain, “At this time, the forecaster consensus unanimously favors a strong El Niño, with peak 3-month SST departures in the Niño 3.4 region potentially near or exceeding +2.0°C.”
As of Sunday, the ensemble mean prediction of NCEP’s Climate Forecast System (CFS) looks like this:
Again, the peak in the 12-month running average of global temperatures generally occurs four months after the Niño 3.4 region peak. As you can see, that region is already much warmer than it was four months ago. That in turn means the running 12-month global temperature — though already at the highest level on record — is all but certain to keep rising for the rest of the year, with 2015 blowing out the previous calendar year record set in 2014.
If the Niño 3.4 region peak is in the November–December timeframe as forecast, then the record for the hottest twelve-month period may not be set until early spring 2016. Then the question of whether 2016 beats 2015 will depend on how quickly the El Niño dissipates — and whether (and how quickly) it transitions to a La Niña, as typically happens at the end of strong El Niños.
Climatologist Kevin Trenberth has explained 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.” Over 90 percent of global heating goes into the oceans — and ocean warming has sped up recently.
Trenberth has been expecting a jumpof up to half a degree Fahrenheit, which could occur “relatively abruptly.” He told ClimateProgress back in April 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.”
The PDO is a “pattern of Pacific climate variability similar to ENSO in character, but which varies over a much longer time scale.” The PDO can remain in one phase almost exclusively for a decade or even longer, as this figure from NOAA’s August “Global Ocean Monitoring” report shows:
Now compare the PDO chart with this NASA global temp chart update to include the record temperatures from July:
You can see that a negative PDO temporarily offsets the long-term global warming trend, whereas a positive PDO brings 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).
The last time global temperatures jumped sharply, it was during an extended period of positive PDO, from 1992 and 1998, ending in the monster El Niño of 1997–1998, which set a new global temperature record by a wide margin. That became a high bar for later 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 highlights the fact there has been no actual 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 — with Arctic warming rising a stunning 1°F per decade by the 2020s. They project 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 accelerated warming appears to starting now.