Finally let's listen to a recent research effort to measure the variation in ocean temperature over time from National Public Radio:

Ship Logs Help Scientists Trace Oceans' Warming
by RICHARD HARRIS
Sydney Levitus works in an ordinary government office building in the ordinary town of Silver Spring, Md. But his work frequently transports him — at least figuratively — back to the helms of ships that plied the seas many decades ago. He's looking at temperature readings from the ship's logbooks.
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