Even the venerable New York Times is prone to completely botching a discussion of the science of climate change. In a front page article today, the NYT reports on how the National Arbor Day Foundation has updated plant hardiness maps to reflect recent changes in climate. (A plant hardiness map presents the lowest annual temperature as a guideline to what plants will thrive in what climate zones.) The NYT misrepresents understandings of variability and trend and in the process confuse more than clarify.
However, it is Pielke Jr who has completely botched the discussion.
The new map updates a 1990 USDA map based on 1974-1986 data, and replaces it with data from 1990-2006. In most places the range of increased average minimum temperature has moved north as can be seen from a difference map between the two time periods. The difference map, shown here, has the horizontal lines because the zones used are so broad — 10 degrees — that the differences are only noticeable at the margins of the zones.
The New York Times reports that these differences can all be attributed to human-caused climate change, using the case of Atlanta as an illustration:
Using data from the National Oceanic and Atmospheric Administration, the Arbor Day map indicates that many bands of the country are a full zone warmer, and a few spots are two zones warmer, than they were in 1990, when the map was last updated.
Atlanta, which was in Zone 7 in 1990, is now in Zone 8, along with the rest of northern Georgia. That means that areas in the northern half of the state where the average low temperature was zero to 10 degrees Fahrenheit are now in a zone where the average low is 10 to 20 degrees. A scientific consensus has concluded that this warming trend has largely been caused by the human production of heat-trapping gases.
Because the zones span 10 degrees (or 5 degrees in the case of the 1990 USDA map) and the largest change shown on the difference map is 2 degrees, then clearly no location has jumped 2 zones! This is just an error.
Indeed it is, but the error is Pielke Jr’s. The difference map shows not the change in temperature, but the change in zones (Hint: the legend says “Zone Change”). The largest change is not 2 degrees as Pielke Jr thinks but 2 zones. NYT 1 Pielke Jr 0.
Pielke Jr continues:
More important than this simple mistake is the claim in the NYT that the changes in temperature observed in Atlanta can be attributed to human-caused greenhouse gases. In fact, the IPCC argues that it needs 30 years of records to detect trends, much less make attribution. In fact, the IPCC report just out has reported that the U.S. southeast has actually cooled over the period of record as shown below.
But Pielke Jr has shown the trends since 1901 even though the IPCC only stated that most of recent warming is anthropogenic, not warming since 1901. Right next to the graph that Pielke Jr chose to present is one that shows trends since 1979 (AR4 Chapter 3 22Mb pdf):
The graph shows that the US South East has warmed since 1979. Now it is true that the IPCC has only attributed warming mainly to human influences over the past 30 years and at the level of continents, but the trend in the US South East over the past 15 years is similar to that over North America over the past 30, so the NYT is justified in attributing to human influences. NYT 2 Pielke Jr 0.
Hans von Storch and Eduardo Zorita have a post on the hockey stick that is going to annoy everyone involved in the hockey stick wars:
In October 2004 we were lucky to publish in Science our critique of the ‘hockey-stick’ reconstruction of the temperature of the last 1000 years. Now, two and half years later, it may be worth reviewing what has happened since then.
The publication in 2004 was a remarkable event, because the hockey-stick had been elevated to an icon by the 3rd Assessment Report of the IPCC. This perception was supported by a lack of healthy discussion about the method behind the hockey-stick. In the years before, due to effective gate keeping of influential scientists, papers raising critical points had a hard time or even failed to pass the review process. For a certain time, the problem was framed as an issue of mainstream scientists, supporting the concept of anthropogenic climate change, versus a group of skeptics, who doubted the reality of the blade of the hockey stick. By framing it this way, the real problems, namely the ‘wobbliness’ of the shaft of the hockey-stick, and the suppressing of valid scientific questions by gate keeping, were left out.
Mann and company are not going to appreciate the insinuation that they were involved in the suppression of valid scientific questions, while McIntyre is already hopping mad that he wasn’t given credit for totally smashing the hockey stick.
Update: Since I can’t post images in the comments, here is a graph (from the NCDC) of Jan temperatures in the US. It warmed 2°F per decade.