Apr 26, 2018

Global temperatures have dropped since 2016. Here’s why that’s normal.

United States
by
Matt Rogers
,
Washington Post
Temperature difference from normal for the first part of 2018 (January through March). Image: NOAA
Temperature difference from normal for the first part of 2018 (January through March). Image: NOAA

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.