temperature anomalies

Chart of global temperature since 1950, also showing the phase of the El Niño-La Niña cycle. Via NASA.

Signs are increasingly pointing to the formation of an El Niño in the next few months, possibly a very strong one. When combined with the long-term global warming trend, a strong El Niño would mean 2015 is very likely to become the hottest year on record by far.

El Nino

El Niño visualization (via NOAA)

An El Niño is “characterized by unusually warm ocean temperatures in the Equatorial Pacific,” as NOAA explains. That contrasts with the unusually cold temps in the Equatorial Pacific during a La Niña. Both are associated with extreme weather around the globe. But, as the above chart from NASA shows, El Niños are generally the hottest years on record, since the regional warming adds to the underlying global warming trend. La Niña years tend to be below the global warming trend line.

Because 1998 was an unusually strong “super El Niño,” and because we haven’t had an El Niño since 2010, it can appear as if global warming has slowed — if you cherry-pick a relatively recent start year. But in fact several recent studies have confirmed that planetary warming continues apace everywhere you look.

Remember that 2010, a moderate El Niño, is the hottest year on record so far. And 2010 saw a stunning 20 countries set all-time record highs, including “Asia’s hottest reliably measured temperature of all-time, the remarkable 128.3°F (53.5°C) in Pakistan in May 2010.” Meteorologist Dr. Jeff Masters said 2010 was “the planet’s most extraordinary year for extreme weather since reliable global upper-air data began in the late 1940s.”

Given that the “Earth’s Rate Of Global Warming Is 400,000 Hiroshima Bombs A Day,” the planet is half a billion Hiroshimas warmer than it was in 2010. So even a moderate El Niño will cause record-setting temperature and weather extremes. But a strong one, let alone a super El Niño, should shatter records.

Peru’s official El Niño commission said last week that they are expecting an El Niño to start as soon as April. Peru tracks this closely because “El Nino threatens to batter the fishmeal industry by scaring away abundant schools of cold-water anchovy.”

To be clear, an El Niño is not a sure thing at this point. Some forecasters put the chances at about 60 percent, but one recent study put the chances at 75 percent.

Mashable’s Andrew Freedman (formerly of Climate Central) reports “some scientists think this event may even rival the record El Niño event of 1997-1998.” He cites meteorology professor Paul Roundy:

Roundy said the chances of an unusually strong El Niño event “Are much higher than average, it’s difficult to put a kind of probability of it … I’ve suggested somewhere around 80%”

“The conditions of the Pacific ocean right now are as favorable for a major event as they were in march of 1997. That’s no major guarantee that a major event develops but clearly it would increase the likelihood of a major event occurring,” Roundy says.

The El Niño Southern Oscillation (ENSO) doesn’t change the overall warming trend, but it is a short-term modulation, what NASA labels the largest contributor to the “natural dynamical variability” of the climate system. El Niño and La Niña are typically defined as sustained sea surface temperature anomalies (positive and negative respectively) greater than 0.5°C across the central tropical Pacific Ocean. You can read the basics about ENSO here.

One key El Niño indicator is the rapid rise in upper ocean temperatures in the central and eastern Pacific — just what NOAA reported Monday:

El Nino

Since the end of January, temperature anomalies have strongly increased.

Meteorologist Michael Ventrice had a detailed analysis in late February here on why such warming is significant.

For El Niño junkies, NOAA’s National Centers for Environmental Prediction (NCEP) releases a weekly ENSO report every Monday here. And super-junkies can go to the ENSO page of the Australian government’s Bureau of Meteorology (updated every second Tuesday), which also charts another key El Niño indicator, the Southern Oscillation Index (SOI). For the SOI, “sustained negative values below −8 may indicate an El Niño event.” The latest 30-day SOI value (through March 23) is −12.6.

The ensemble mean prediction of NCEP’s Climate Forecast System (CFS) is for an El Niño in early summer, eventually getting quite strong:

CFS2

When the El Niño forms and then peaks is crucial to whether 2014 or 2015 (or both!) will be the hottest year on record. A 2010 NASA study found “the correlation of 12-month running-mean global temperature and Niño 3.4 index is maximum with global temperature lagging the Niño index by 4 months.”

If we do get an El Niño, and it looks anything like the 1997/1998 one, then 2015 in particular should be the hottest year on record by far. Stay tuned.

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