The peer-reviewed paper Hansen and his colleagues submitted stated “with a high degree of confidence” that some extremely high temperatures are in fact caused by human induced global warming.
The reasoning behind this assertion has to do with normal statistical variability. It specifically has to do with a statistical manipulation known as standard deviation which is a measure of variability that is well suited to address weather.
Hansen has clearly said that some of these anomalous weather events can be attributed to global warning. But what about the extreme cold snaps climate-change deniers keep pointing to? Even with global warming, Hansen told Time.com in an email, there “is still a broad bell curve. In fact, it has become broader, which means there will still be times when a season is colder than average. When that happens [people] should not say, ‘What happened to global warming?’ It will still be there — they are just looking at natural variability.”
Back in 1988, when Hansen was among the first and most credible scientists to sound the alarm about global warming, he, Ruedy and several co-authors came up with the concept of “climate dice.” Imagine dice with two sides red (for hot), two sides blue (for cold) and two sides white (average temperatures). If you roll the dice, you’re equally likely to get any result. With continued emissions of greenhouse gas, however, the authors predicted that by the early 21st century, four of the sides would be red.
“The climate dice are loaded now, just as we said back in the 1980s that they would be,” Hansen wrote to Time.com. “People should be able to recognize the change, especially the increasingly extreme events.”
© 2013, Richard Matthews. All rights reserved.
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