"Answers For DeLong About The SuperFreaks, Part One"
Blogging economist J. Bradford DeLong has read the “global cooling” chapter of SuperFreakonomics and has made some suggested corrections. He also asked six wonkish questions about climate policy, spurred by the misleading portrayal of the field by University of Chicago economist Steven Levitt and journalist Stephen Dubner. The Wonk Room will be answering DeLong’s questions. Here are answers for the first two questions about passages from SuperFreakonomics:
1: “Wood notes that the most authoritative literature on the subject suggests a rise of about one and a half feet by 2100…” I had thought that the most authoritative estimates suggest a 1 to 7 feet rise in sea levels by 2100–not 1.5 feet. Am I wrong?
“Most authoritative” is a value judgment, of course. If we consider literature that was reviewed and summarized by the 2007 International Panel on Climate Change report (AR4) as the “most authoritative,” then the climate models considered there provide estimates of sea level rise of 0.18 – 0.59 m (0.59 – 1.93 ft), depending on future emissions and “excluding future rapid dynamical changes in ice flow.” [IPCC Fourth Assessment Report, Working Group 1, Summary for Policymakers, 2007]
However, that exclusion is a major caveat, and all the literature on “dynamical changes in ice flow” points to a much higher estimate for likely sea level rise by 2100. The MIT Joint Program on the Science and Policy of Global Change has found that the likelihood of warming of 4°C is almost 100 percent without efforts to limit carbon dioxide emissions. At the 4 Degrees and Beyond climate conference this September, lead climate researchers presented their latest estimates of sea level rise for 2100 given 4°C warming. Pier Vallinga summarized recent estimates of sea level rise under warm scenarios:
These estimates give a range of 0.4 to 2 m (1.31 to 6.56 ft), on average estimating 0.95 m (3.1 ft). It should be noted that sea level rise by 2200 will be about twice that of 2100, as the oceans continue to rise due to thermal expansion and the disintegration of the Greenland and West Antarctica ice sheets. In short, Wood is only off by a factor of 100 percent.
2: “Ken Caldeira… mentions a most surprising environmental scourge: trees…” I grant that covering the reflective Greenland ice sheet with green leaves might not be a good idea. But surely Ken Caldeira of Stanford did not say that your average tree is doing less to cool the earth by sucking up carbon dioxide than if the tree were cut down and decomposed and some other more-reflective typical use were made of its spot, is he?
In a word, no. In a 2007 New York Times op-ed discussing his research and opinions on forestation and climate change mitigation, Caldeira wrote:
This effect is most pronounced in snowy areas — snow on bare ground reflects far more sunlight back to space than does a snowed-in forest — so forests in areas with seasonal snow cover can be strongly warming. In contrast, tropical forests appear to be doubly valuable to the earth’s climate system. [New York Times, 1/16/07]
He also noted: “Clear-cutting mountains to slow climate change is, of course, nuts.”
Caldeira told me the book contains “many errors” in addition to the “major error” of misstating his scientific opinion on carbon dioxide’s role. . . . When I told Dubner that Caldeira doesn’t believe geoengineering can work without cutting emissions, he was baffled. “I don’t understand how that could be,” he said. In other words, the Freakonomics guys just flunked climate science.