TO CALL WHAT’S happening in the oceans right now an anomaly is a bit of an understatement. Since March, average sea surface temperatures have been climbing to record highs.

A graph titled: SST World (60S-60N) NOAA OISST V2.1 | Maine Climate Office, Climate Change Institute, University of Maine. The image depicts yearly ocean temperatures dating back to 1981. 2022 is bright gold and 2023 is bold black, both of which stand out against the gray lines of previous years. 2023 sits far atop the others and has not yet dropped down as every other year in the graph shows. Instead it has remained very high depicting an ominous change.

Since this record-keeping began in the early 1980s—the other squiggly lines are previous years—the global average for the world’s ocean surfaces has oscillated seasonally between 19.7 and 21 degrees Celsius (67.5 and 69.8 Fahrenheit). Toward the end of March, the average shot above the 21-degree mark and stayed there for a month. (The most recent reading, for April 26, was just a hair under 21 degrees.) This temperature spike is not just unprecedented, but extreme

An Ominous Heating Event Is Unfolding in the Oceans | WIRED