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.
"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."
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