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When Scientists Talk Like Lawyers . . .We Should Be Skeptical

“I’m not saying it is global warming, but it’s what global warming would look like. It’s consistent with the kind of weather climate scientists predict will become more frequent and severe as greenhouse gas concentrations in the atmosphere increase.” This is standard rhetorical fare whenever extreme weather strikes somebody, somewhere on the planet.

“It,” in the preceding, refers to the persistent heat wave affecting the Mid-Atlantic region and thederecho that uprooted trees, downed power lines, and deprived nearly a million households in the D.C. metro area of electricity and air conditioning. Warmists, or most of them, know they cannot actually link a particular weather event to global warming, but they’d like you to make the connection anyway.

This is standard rhetorical fare whenever extreme weather strikes somebody, somewhere on the planet. A commenter on Georgia Institute of Technology Prof. Judith Curry’s blog notes the resemblance to an old court-room trick:

Kind of like a lawyer asking an improper question and then withdrawing it, because all s/he really wanted was to put the idea in the jury’s mind.

In her blog, Prof. Curry discusses an article by AP reporter Seth Borenstein titled, “This U.S. summer is ‘what global warming looks like’.” Mr. Borenstein interviewed 15 climate scientists in connection with the story, including Curry, yet did not include her responses to his questions in the article. How convenient! A few excerpts from their exchange:

SB: Can you characterize what’s going in the US in terms of a future/present under climate change? Is it fair to say this is what other scientists been talking about?

JC:  As global average temperature increases, you can expect periodically there to be somewhere on the globe where weather patterns conspire to produce heat waves that are unusual relative to previous heat waves. However, there have been very few events say in the past 20 years or so that have been unprecedented say since 1900.

SB:  This seems to be only US? Is it fair to make a big deal, since this is small scale and variability and is only US? However in past years, especially in late 1990s and early 2000s, the US seemed to be less affected? So what should we make of it?

JC:  Right now, this is only the U.S. Recall, 2010 saw the big heat wave in Russia (whereas in the U.S. we had a relatively moderate summer, except for Texas). Note, the southern hemisphere (notably Australia and New Zealand) is having an unusually cold winter.

SB:  What about natural variability? Are other scientists just making too much of what is normal weather variability?

JC: We saw these kinds of heat waves in the 1930s, and those were definitely not caused by greenhouse gases. Weather variability changes on multidecadal time scales, associated with the large ocean oscillations. I don’t think that what we are seeing this summer is outside the range of natural variability for the past century. In terms of heat waves, particularly in cities, urbanization can also contribute to the warming (the so-called urban heat island effect).

Data on hurricanes also confirm Dr. Curry’s point. Al Gore and others opined that 2004-2005 marked a shift to a new climate regime of increasingly powerful and destructive hurricanes. Dr. Ryan Maue of Florida State University finds that global tropical cyclone frequency has declined slightly from 1970 to the present, while global tropical accumulated cyclone energy (a measure of hurricane strength) has declined significantly since 2006.

Global Tropical Cyclone Frequency

Global Tropical Cycle ACE

Meteorologist Anthony Watts notes that the drought afflicting the U.S. Southwest and Midwest today is much less severe than the drought of the 1930s, before greenhouse gas emissions could have had much effect on global climate:

The 1930s drought was itself less severe than some that occurred in pre-industrial times.