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ENSO

I am here to talk about the coming of the boy child Jesus Christ. No, it’s not Christmas. No, you don’t get any presents. And no, I’m definitely not trying to convert you.

In fact, I maybe lied to you. I’m not really writing an article about Jesus, I’m writing one about the climate phenomenon known widely as El Niño, so named because South American fishermen noticed some funky shit happening in the Pacific around Christmas time. I just used the Jesus line to fool you into letting me in. 

Realistically, I decided to focus my attention on this matter today because there’s been some hubbub recently about how an awful lot of weather insanity has been occurring this year due to the fact that this has, in fact, turned out to be a year where there was an El Niño event. I also realized that I knew probably two things about it:

  1. This year’s has been a bit of a monster
  2. Something about warm water in the central Pacific

and that’s about it. In all fairness, that’s probably all I still know about it, only I have about 3 more details to go along with it.

As it turns out, warm ocean water off the coast of South America is only the tip of the iceberg (haha get it) and the real deal is a huge span of the equatorial Pacific, starting from just north of the Solomon islands and stretching all the way to the shores of Ecuador and Peru. For added complexity, El Niño actually only refers to the warm phase of the oceanic component of a larger climate system, and it’s atmospheric compatriot is called the Southern Oscillation. Fun fact: the whole shebang is called the El Niño Southern Oscillation, because apparently climatologists have vivid imaginations. A cold phase exists as well, and it’s called La Nina.

To be perfectly fair to the scientists, their plates are already stacked with issues that are more important that choosing interesting names. Interpreting climate data is fiendishly difficult do to the number of variables involved, and in an attempt to properly identify ENSO events, the central Pacific has been split into 3? 4? 5? regions where sea surface temperature is recorded.

The reason why I’m not entirely sure how many regions there are is because the divisions are a little strange:

  • Niño 1+2 is the furthest east and smallest of the regions, and it is the area defined by 0°-10°S, 90°W-80°W. This was the area in which El Niño was first identified. Niño 1 is the top half of the rectangle, and Niño 2 is the bottom. This (these?) region(s?) also have the highest variance of all of the indices, but it also has the most noise and a poor response to cold events.
  • Niño 3 lies between 5°N-5°S and 150°W-90°W. It used to be the main index region for monitoring sea surface temperature anomalies.
  • Niño 3.4 was created when researchers realized the best place for identifying ENSO was actually further west than they originally thought, and shifted to 170°W-120°W. A 5 month running average of SST is used, and El Niño is defined as when this average is greater than 0.4°C for more than six months, whereas La Nina is when the average drops below -0.4°C for the same amount of time. For added fun, a second index exists, called the Oceanic Niño Index, which uses the exact same region as Niño 3.4 but defines ENSO events differently. Under the ONI, a 3 month average is used and the threshold is ±0.5°C for 5 months or more. 
  • Niño 4 is the furthest west (and furthest east, really), even stretching over the date line at 160°E-150°W. It has the lowest variance of any index, and has a good response to cold events.

I don’t know where longitude lines are off the top of my head, so here’s a fun map to help out everybody else like me

image from NOAA Climate.gov by Fiona Martin

image from NOAA Climate.gov by Fiona Martin

That’s much nicer, isn’t it?

As a matter of note, Niño 3.4 is great for classifying El Niño, but Niño 4 might be better for La Nina because nothing is allowed to be straightforward on this planet, at all, ever. More complications arise as more indices, like the Southern Oscillation Index, are required to monitor the atmosphere, and the SOI correlates stronger to Nino 3 than any of the others.

The naming “Southern Oscillation” makes it particularly obvious that these events aren’t at all uncommon. In fact, the period is 3-7 years, but the intensity from one to another varies massively. In fact, we’re currently just coming down from a particularly massive El Nino session, to the point that it is the third recorded “super” El Nino since at least 1950, with the two previous being in ’82-83 and ’97-98. 1998 was a particularly awful year to start, with January and February showing devastation from ice storms in eastern Canada and the U.S. as tornadoes ripped through Florida and floods covered California. To be fair, California had been having an incredibly bad time the years before that as well, but not to the point where almost every part of the state experienced record rainfall. Similarly, 2015 and 2016 have been brutal as each consecutive month seemingly is the hottest on record, and that was joined by brutal storms along coasts and droughts inside the continents. For example, Chennai, an Indian city on the Bay of Bengal, received three times it’s ordinary rainfall in November, bringing about widespread flooding. To put that into context for Albertans, an average November in Chennai has as much rainfall as Edmonton gets—rain and snow—in a year. And speaking of Edmonton precipitation, I’m sure that almost everybody who lives here can attest to how ridiculously dry (and warm) this city has been so far this year, at least up until a couple of days ago.

This past year has shown only ever increasing temperatures (literally, May 2015-April 2016 have all broken heat anomaly records), and this was at least in part aided by the killer warm streak that the Pacific Ocean has been raining all over the planet as it dumps extra heat from the failed ’14-15 El Nino on top of the ’15-16 event. While this was likely largely carbon-induced, it does bring up the interesting question of how much the subsequent La Nina that’s mounting will swing things back in the opposite direction. La Nina is just as difficult to predict as its counterpart, however, so it’s anyone’s guess as to what whether or not the hot streak will be put on hold. This also brings up the excellent question as to what will happen to ENSO frequency and intensity as climate change progressively worsens, and research is still ongoing on the matter. Unfortunately for everybody involved, the answer is to almost every excellent question is “nobody really knows” and this one is no exception. Reports are all over the place, and indicate that it can get stronger, longer, shorter, and weaker. What is for sure is that it will probably continue and that climate change will likely alter the way that ENSO interacts with the planet, as a warming earth involves redistribution of rainfall, albeit in a different way than an anomalously warm or cold central Pacific does. Thus, there are certain situations (like a dry El Nino Indonesia) that will lessen, while others (for instance, California drying out during La Nina) that will become more extreme. Overall, attempting to predict future climate patterns is an exceedingly hard thing to do and just generally a bad time for everyone that’s trying to do it, apparently.

 

As before, I’m sure that this meandering thought process has been exceedingly difficult to follow for everyone, so here’s some sick links for extra reading (and also sources):

http://www.linkingweatherandclimate.com/ENSO/def.php

https://www.climate.gov/news-features/blogs/enso/what-el-niño–southern-oscillation-enso-nutshell

https://www.climate.gov/news-features/understanding-climate/climate-variability-oceanic-niño-index

https://climatedataguide.ucar.edu/climate-data/nino-sst-indices-nino-12-3-34-4-oni-and-tni

https://www.ncdc.noaa.gov/teleconnections/enso/

https://www.climate.gov/news-features/blogs/enso/enso-climate-change-headache

http://www.scientificamerican.com/article/earth-sees-11-record-hot-months-in-a-row/

http://www1.ncdc.noaa.gov/pub/data/techrpts/tr9802/tr9802.pdf

Extra: http://www.climate-lab-book.ac.uk/files/2016/05/spiral_optimized.gif is a cool animation on the rapid increase in world temperature over the past 150 years. The original post, and the comment section underneath it, provides some interesting insight into the data, especially how records from pre-globalization and pre-satellite data was obtained.

Alright, I'll see you all later

-Ben

THIS Term's Writer

THIS Term's Writer

Fire