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A day by day comparison sea surface heights from the "super" El Nino in 1997-98 and the current El NIno pattern in the Pacific Ocean.
OUT OF THIS WORLD | Earth, Space And The Stuff In Between - a daily journey through weather, space and science with meteorologist/science writer Scott Sutherland

El Niño Update: Could it be gaining a second wind?

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Scott Sutherland
Meteorologist/Science Writer

Monday, January 25, 2016, 9:52 AM - Eyes are still on El Niño this month, as it gives more indications of having reached its peak. Are new signs pointing towards a fresh surge in strength, and what could be in store for the globe in 2016?

As we reached the end of 2015, the most up-to-date look at the El Niño pattern in the equatorial Pacific Ocean showed that temperatures in the central equatorial Pacific -  the "Niño 3.4 region" which scientists use to gauge the strength of the El Niño Southern Oscillation (ENSO) - had reached their maximum in mid November, and were slowly cooling down.

The latest look from NASA appears to support that conclusion. As they wrote on the NASA Earth Observatory website:

If past events help predict future ones, then we have probably reached the peak of the 2015–2016 El Niño. Warmer-than-average waters in the eastern tropical Pacific Ocean should start to cool off and shift westward. By summer, the tropical Pacific might be back in a neutral state or La Niña cooling could kick in, as it did after major El Niños of the past.

However, although representations of the pattern usually focus on sea surface heights and temperatures, that is only because it is usually the easiest way to visualize what's happening.


Tracking sea surface heights with NASA's Jason-2 satellite. Credit: NASA Earth Observatory/Joshua Stevens


Sea surface temperature anomalies across the Pacific Ocean, from October 28, 2015 to January 13, 2016. Credit: NOAA

The fact is, the ocean is only one half of ENSO, and to get a complete picture of what's going on, the atmosphere over the equatorial Pacific needs to be taken into account as well.

While the general strength of an El Niño is recorded with the Oceanic Niño Index (ONI), the Southern Oscillation Index (SOI) is used to track what is happening with the atmosphere.

Just like ONI, the SOI is a three-month running average, but in this case, rather than tracking temperatures above or below normal in one region of the ocean, SOI tracks the difference in atmospheric pressure between two places - Tahiti, in the middle of the Pacific, and Darwin, in northern Australia.


Credit: NOAA Climate.gov/Fiona Martin.

As we progressed through 2015, ONI values continued to climb, reaching a maximum of +2.3 for the October-December three-month average, and matching the strength of the 1997-98 "super" El Niño in the process

At the same time, weekly sea surface temperature anomalies in the Niño 3.4 region reached a peak in mid-November, at their highest level ever seen - 3.1oC above normal (they only reached a maximum of +2.8oC in 1997). By now, a few weeks into 2016, sea surface temperature (SST) anomalies in the central Pacific continued on a slow downward tend, having reached +2.6oC above normal, but the SOI is very different.

When sea surface temperatures were on the rise in the central Pacific, SOI values were getting more and more negative - indicating a strengthening El Niño - with higher atmospheric pressure over northern Australia than over the central Pacific, and thus weaker trade winds and the spreading of warmer waters towards the east. Then, in December, the SOI backed off, apparently matching the weakening trend seen in the ocean after the November peak.

In the last days of 2015 and in first few weeks of 2016, however, there has been a surge in the SOI, driving it strongly negative.

As of January 22, 2016, the SOI has reached a 30-day average value of -20.48 (anything -8 or lower indicates El Niño conditions, and anything below -20 for any significant amount of time gets in the "super" El Niño range).

What could this mean for us in 2016?

According to NASA's Earth Observatory, this shift in the SOI was not missed by scientists monitoring the pattern:

Bill Patzert, a climatologist at NASA’s Jet Propulsion Laboratory, sees the potential for a second peak for this El Niño. He pointed to a recent relaxation in the trade winds and a west wind burst that could refuel the warming trend in the eastern Pacific. Weaker trade winds in the eastern Pacific allow west wind bursts to push warm waters toward the Americas. Patzert suspects February and March 2016 could still be very active months for El Niño-driven weather along the western coasts of the Americas.

As 2015 has now taken its place as the new hottest year on record, with an over 99 per cent confidence level from NOAA, El Niño definitely played a role. The influence wasn't overwhelming, as NASA climate scientist Gavin Schmidt estimated that it added 0.07oC to the global temperature anomalies for the year.

There is an overall trend, however. Just look at the nine El Niño events going back to the 1980s, and for all but two - 1991-92 and 2006-07 - the second year of the event was the hotter one.

This reached an extreme case for the last super El Nino, too, in 1997-98. 1997 took the top spot on the list of hottest years on record after the year was over, at 0.51oC over the 20th century average, but it only held that spot for one year. 1998 came in at over a tenth of a degree hotter than that when all the numbers were tallied (and +0.63oC above the 20th century average). It was so warm that year that it set a kind of "new normal" for the world, and that year maintained the #1 position on the list of hottest years until 2005 came along. Since at least the 1970s, that's the longest any year has held the top spot on that list.


NOAA's hottest years on record going back to 1975, with notations by S. Sutherland

Will 2016 do the same - becoming the new hottest year on record and setting yet another new standard for global temperatures?

As this particular El Niño was growing and strengthening, we looked back to previous episodes, to get an idea for how it might develop, and just how strong it could get. Of particular note were the "anomalous" double-peaked El Niño of 1986-1987, the strong and early-developing 1982-1983 El Niño, and the "super" El Niño of 1997-1998 (the strongest ever recorded).

As it has turned out, El Niño 2015-2016 has become a unique combination of these three events. It not only developed like the '82-'83 pattern, with an early start in the year, it also showed some signs of a weak double-peak, and it has grown to rival the strength of the '97-'98 event. In fact, it could easily surpass that last "super" El Niño when the final November-December-January ONI value comes in for 2015.

Now, as the pattern has peaked, forecasters are looking at how quickly it will diminish, and also for the possibility that it will transition into a La Niña phase towards the end of the year.

The mid-January forecast from the NWS Climate Prediction Center and the International Research Institute for Climate and Society, gives some indication that the pattern will weaken in 2016 along the same lines as what was seen in 1983 (the thick purple line riding above most of the forecast model values is the CPC consensus forecast). However, it will be doing so from a position of strength more indicative of the 1997-98 El Niño.

So, what could this mean for global temperatures in 2016?

It's difficult to say anything definite this early in the year, however we can look to the past to speculate about the future.

Several scenarios for monthly global temperature anomalies are presented above for 2016, using both the monthly temperature anomalies and ONI values from those three previous El Niño events as a guide, and factoring in the significantly higher global temperatures that have been experienced in more recent years, along with the forecast for how this El Nino pattern will proceed from here.

The end result - an annual global temperature anomaly of around 1.11oC above the 20th century average.

That would put 2016 at the top of the list of hottest years on record, beating out 2015 by a margin of 0.21oC, and making it the third year in a row that we've had a new hottest year on record.

While there have certainly been three years in a row where global temperatures have been successively higher in each of those years, in the history of our temperature records, going back to the year 1880, there have never been three hottest years on record for the globe in a row. Ever.

More to come as the year progresses.

Sources: NASA Earth Observatory | NOAA | NOAA | Queensland Government

Watch Below: Understanding El Nino

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