The National Climatic Data Center has released its review of worldwide sea surface temperatures for August and for the stretch from June through August and finds that both the month and the “summer” (as looked at from the Northern Hemisphere) were the warmest at least since 1880, when such records were first systematically compiled.

Sea ice in the Arctic appears to be starting the slow late-summer freeze after reaching its minimum extent several days ago, by a couple of estimates (National Snow and Ice Data Center; International Arctic Research Center / Japan Aerospace Exploration Agency). Here’s the global sea ice trend, combining what’s going on up north and down south. This season’s Arctic ice retreat ranks well behind the extraordinary ice retreat of 2007 and also last year’s but remains below the average ice extent for the stretch since 1979, when satellites started monitoring Arctic conditions with some precision. Here’s a compilation of various groups’ experimental ice forecasts for this year and the results.

The National Oceanic and Atmospheric Administration summarized ocean temperature conditions for August in this description of the video above:

The world’s ocean surface temperature was the warmest for any August on record, and the warmest on record averaged for any June-August summer season, according to N.O.A.A.’s National Climatic Data Center in Asheville, N.C. Worldwide records began in 1880. Shown here is a visualization of the August global temperature anomalies — or in other words, how the average temperature in August differed from the average climate of 1961-1990. Notice that in some areas, such as the western United States, temperatures were much cooler than average. But overall, land and ocean temperatures were several degrees above normal.

Clearly the current El Niño warming in the tropical Pacific Ocean has contributed to the warm sea conditions. (UPDATE, 9/17: I’ve asked N.O.A.A. officials about their choice of temperature data sets, which has been criticized by some.) Variations in polar sea ice on short time scales, up or down, are essentially meaningless, my contacts studying the cryosphere always stress. Keep track of the long-term trends at the links above.