George Will, Global Warming, and Accuracy

Last week conservative columnist George Will published an op-ed in the Washington Post, Dark Green Doomsayers, wherein he reiterated his skepticism of global warming and portrayed it as hype, and it's been bouncing around the blogesphere ever since. I'll summarize what I've found and provide some links. The column makes several claims; the ones that have gotten the most attention are:

Claim: Back in the 1970s everyone was worried about global cooling, which turned out to be wrong.

Response: See my last post, The Global Cooling Myth. The article cited there actually refers to previous columns by Will as perpetuating the myth.

Claim: "...according to the U.N. World Meteorological Organization, there has been no recorded global warming for more than a decade, or one-third of the span since the global cooling scare."

Response: Nobody seems to know where this claim came from. Here is what I think is going on (as explained by New Scientist). Depending on whose data you believe, 1998 had either the warmest or second warmest global mean temperature since observations began. Let's compare the data from NOAA and U.K. Met Office Hadley Centre.





In the U.K.'s data, 1998 sticks out as the warmest year. Will and others who claim that warming has stopped are privileging the data for a single year above the overall trend. The U.K. data also show a slight cooling in the last few years. I'll leave it to the reader to decide what that means for the overall picture.

Claim: "As global levels of sea ice declined last year, many experts said this was evidence of man-made global warming. Since September, however, the increase in sea ice has been the fastest change, either up or down, since 1979, when satellite record-keeping began. According to the University of Illinois' Arctic Climate Research Center, global sea ice levels now equal those of 1979."

Response: Most of the focus has been on this one. Let's take it in basic chronological order.

Jan 1, 2009: DailyTech website published a story, Sea Ice Ends Year at Same Level as 1979, which reported that a quick recovery in late 2008 resulted in global sea ice levels equivalent to those at the end of 1979. At first glance, this would seem to negate worries about reduced ice.

Jan (?): In response to the story, the Arctic Climate Research Center (ACRC)--which was a source for the DailyTech story--published a clarification (pdf) noting that the article compared global sea ice area. However, Northern Hemisphere ice area has decreased, an observation in line with climate models, and Southern Hemisphere ice area has increased, which is in line with some climate models. Further, although the area may be the same, the new ice is thinner and so ice volume is down.

Feb 15: George Will's column was published, which apparently relied on the DailyTech article for its claim that current global sea ice is the same as 1979.

Feb 15+: In response to Will's column, ACRC put the following statement on their website:

In an opinion piece by George Will published on February 15, 2009 in the Washington Post, George Will states “According to the University of Illinois’ Arctic Climate Research Center, global sea ice levels now equal those of 1979.”

We do not know where George Will is getting his information, but our data shows that on February 15, 1979, global sea ice area was 16.79 million sq. km and on February 15, 2009, global sea ice area was 15.45 million sq. km. Therefore, global sea ice levels are 1.34 million sq. km less in February 2009 than in February 1979. This decrease in sea ice area is roughly equal to the area of Texas, California, and Oklahoma combined.

It is disturbing that the Washington Post would publish such information without first checking the facts.

The Post stands by the column and has refused to print a correction. In support of their position, they cited the first statement from the ACRC, which stated "Observed global sea ice area, defined here as a sum of N. Hemisphere and S. Hemisphere sea ice areas, is near or slightly lower than those observed in late 1979." However, critics point out that they ignored the broader context of the statement, which pointed out the shift observed in the individual hemispheres and lower ice volume.

Defenders of Will point out that at the end/beginning of 2008-2009, he was correct: global sea ice area was equivalent to the end of 1979. So the ACRC's refutation of Will based on February data is irrelevant to his point. I've altered a figure published by the ACRC to show this.



However, the broader context gives a slightly different picture (click to enlarge):


There seems to be a trend in recent years of reduction in global sea ice area. This can be seen both by the trend in the red line, as well as by comparing the upper blue line with the superimposed gray line.

As Carl Zimmer points out, comparing individual days thirty years apart does not give an accurate sense of the overall picture, which is illustrated by looking at the individual hemispheres.





Rather than criticize Will, Carl Zimmer is using this as a lesson on poor fact-checking by a major newspaper. (Part 1, 2, 3, and 4.)

Chris Mooney is using it as a lesson on the generally poor shape of newspapers (The George Will Scandal).

I should also point out that a New York Times story, In Climate Debate, Exaggeration Is a Pitfall, mentions Will's column, as well as the fact that Al Gore has removed a slide that he recently added to his presentation after the source for the slide complained that it was being misused.

---

Update: (2/27/2009) George Will has responded in a new editorial. See George Will Responds; Sinks Deeper.

---