Ocean temperatures not what they seem

Scientists recently solved a longstanding puzzle about Earth's climate record. And human error is to blame.

Between 1940 and 1970, global temperatures suddenly — and mysteriously — declined. The largest drop happened in 1945. Researchers say an abrupt change in how we measured temperature explains the big slump.

Scientists use land and sea-surface temperatures to determine global mean temperatures. Since the 1800s, countries around the world have contributed sea-surface data. But they haven't always gathered the data in the same way.

Fortunately, any errors due to differences in method usually washed out because of the large number of countries involved.

Then World War II broke out.

During the war, U.S. ships collected most sea-surface data. But after 1945, the British took over. The two countries measured temperature very differently. These differences account for the mysterious mid-century decline in global temperatures, report David Thompson and his colleagues in Nature on May 29th.

Scientists will now need to adjust last century's climate record, which is used to make climate models. But the researchers say the correction shouldn't significantly affect estimates of future global temperature trends.

For more on this topic, check out Geotimes Online.

Erin Wayman

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