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, as shown in the dark line in the graph below.

(credit: Sean Birkel/University of Maine)

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° Celsius (67.5° and 69.8° Fahrenheit). Toward the end of March, the average shot above the 21° mark and stayed there for a month. (The most recent reading, for April 26, was just a hair under 21°.) This temperature spike is not just unprecedented, but extreme.

“It’s surprising to me that we’re this far off the trajectory,” says Robert Rohde, lead scientist at Berkeley Earth, a nonprofit that gathers climate data. “Usually when you have a particular warming event, we’re beating the previous record by a little bit. Right now we’re sitting well above the past records for this time of year, for a considerable period of time.”