October 26, 2009

Global Warming Passes Blind Taste Test
Via Earth to Philly, I learned that global warming took the Pepsi Challenge a "blind taste test." And it passed!
In a blind test, the AP gave temperature data to four independent statisticians and asked them to look for trends, without telling them what the numbers represented. The experts found no true temperature declines over time.

...The AP sent expert statisticians NOAA's year-to-year ground temperature changes over 130 years and the 30 years of satellite-measured temperatures preferred by skeptics and gathered by scientists at the University of Alabama in Huntsville.

Statisticians who analyzed the data found a distinct decades-long upward trend in the numbers, but could not find a significant drop in the past 10 years in either data set. The ups and downs during the last decade repeat random variability in data as far back as 1880.

Saying there's a downward trend since 1998 is not scientifically legitimate, said David Peterson, a retired Duke University statistics professor and one of those analyzing the numbers.

...[One of the statisticians] produced three charts to show how choosing a starting date can alter perceptions. Using the skeptics' satellite data beginning in 1998, there is a "mild downward trend," he said. But doing that is "deceptive."

The trend disappears if the analysis starts in 1997. And it trends upward if you begin in 1999, he said.

Note that the current "cooling trend" is entirely consistent with normal variation. In other words, the weather can be unpredictable in the short term, but the climate is showing a clear warming trend.

Fudging the numbers -- a favorite past-time deniers of all stripes... Still, it's always nice to see reality pass a reality-check.

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