It was only two years ago that a new record-warm global temperature was set, but things have already cooled off significantly. Temperature anomalies hit record peaks in 2016 but have been sliding since then. Global temperatures are still much warmer than normal, but according to NASA, the first quarter of 2018 (January-March) was the fourth warmest, behind 2015, 2016, 2017 and tied with 2010.
This is normal, of course. The world has not seen the last of global warming. The long-term upward trend in temperatures is the result of man-made fossil fuel emissions, but natural processes that affect global temperature — like El Niño — still play a role. Sometimes they make things warmer and sometimes they make things cooler.
The current cooling episode is mostly the result of a reversal of waters in the Tropical Pacific, which can modulate global temperature. Since the Pacific Ocean is our largest global body of water, what it does makes a big difference on global climate. A similar reversal followed the super El Niño in the late ’90s — 1998 was the hottest year on record at the time in part because of the warm El Niño water pushing global temperatures over the brink. Earth went from having one of the strongest El Niño events on record (very warm waters in the central Tropical Pacific) to a few years of cooler waters, thanks to a La Niña period.
Natural processes like El Niño and La Niña are why we end up with graphs like this. There’s a lot of fluctuation, but overall the trend is up.
Following the super El Niño of 2015-2016, we similarly hit a new warm global record in 2016, and since then, the waters have cooled back in the Tropical Pacific with a two-year La Niña period (This “ENSO” cycle oscillates back and forth every three to seven years).
You can see the dramatic difference in the central Tropical Pacific between 2018 and 2016’s peak here based on mapping out NOAA’s re-analysis data set:
The Indian Ocean is considerably cooler now vs. 2016, but the biggest changes are right along the equatorial waters through the Pacific and over to South America.
The ocean temperatures have a direct, causal relationship with air temperature, and La Niña is cooling things down over the Tropical Pacific. Here is the difference in air temperature over the ocean between 2016 and now — eight to 15 degrees cooler than before.
Much of Europe, Asia and North America have been running much cooler than the super El Niño-fired winter that included the first quarter of 2016. Some of the recent cooling may also be tied to stronger North Atlantic high pressure “blocking” patterns that were the strongest in about eight years:
Such strong blocking pattern signatures may be associated with an incoming deep solar minimum period similar to what we experienced between 2008 and 2011, which helps to flush more cool to cold air into the middle latitudes during the winter seasons mainly (record snows in Europe and a very cool North American March to April period). This may be something to watch for next winter, but for now, this current “cooling” seems to be mostly influenced by La Niña and the ENSO cycle.
Climate models from around the world are forecasting this relatively cooler La Niña narrative to end over the next six months as a weak El Niño tries to develop. This should put a stop to the stop and start sending global temperature upward again by winter and especially 2019.
When global temperatures dropped after the 1998 record, we hit our next global temperature peak by the 2002 El Niño, so it will be worth watching to see how quickly we get back on track. There are already signs of another El Niño by next winter.
Global warming isn’t a straight line. There will be record warm moments and not-so-warm moments, but overall the trend is upward.