In a recent letter to the Edmonton Journal, George Witt made a number of claims about NASA’s global temperature data program. Many were incorrect, some were insulting and all were unsubstantiated. They warrant a response.
1) Witt finds it interesting that NASA released its 2010 report before year end, suggesting they did so because of the UN Climate conference taking place in Cancun.
There is no conspiracy here. Since about the late 1700s meteorologist have been defining the seasons in groups of three whole months with winter, in the northern hemisphere, beginning on December 1, spring on March 1, and so on, making November 30 the meteorological year end.
2) Citing The Journal, Witt says that NASA used “only 30 odd sites to determine Canada’s 2009 temperature.”
In an e-mail to me about Witt’s letter, Dr. Reto Ruedy, the person in charge of analyzing monthly mean data at NASA’s Goddard Institute of Space Studies [GISS] says, “We never determined Canada’s temperature. We only combine monthly mean temperature anomalies which indicate how much warmer or colder a particular month is than normal.”
3) Witt is dismayed that there are only 3,000 world surface temperature monitoring sites in use today, when prior to the ‘60s there were over 7,000. He feels this makes it very difficult to compare results. “
Dr. Ruedy disagrees. “The number of additional station data in the Sputnik era did not significantly impact the margin of error of our estimates. Using only the 2 to 3,000 stations that are still reporting today, we get estimates that are statistically indistinguishable from our current estimates….”
In a Q&A article on an NASA website, Dr. Gavin Schmidt, a GISS climate researcher, says much the same: “Global weather services gather far more data than we need. To get the structure of the monthly or yearly temperature changes over the United States, for example, you’d need just a handful of stations, but there are actually some 1,100 of them. You could throw out 50 percent of the station data or more, and you’d get basically the same answers.”
4) Witt says that the GISS scientists, by “massaging” the data and selecting “preferred sites,” have corrupted the original “raw data.”
Ruedy dismisses this statement. “Since I have no idea what the author means by ‘raw data’ the rest of his article is meaningless. We download the monthly mean data from public access sites on the web, and that is exactly how close we get to the ‘raw data.’
When asked about manipulating data, Dr. Schmidt said, “That's completely inaccurate. We do an analysis of the publicly available data that’s collected by other groups. “
5) According to Witt says NASA refuses to release its raw data.
“All of the data is available to the public for download,” says Dr. Schmidt, “as are the computer programs used to analyze it. One of the reasons the GISS numbers are used and quoted so widely by scientists is that the process is completely open to outside scrutiny.”
Says Dr. Ruedy, “The claim that we refuse to release data – data we ourselves obtained from the public domain – is absurd, or more likely pure slander.”
NASA surface temperture data and the related programs are availabe at http://data.giss.nasa.gov/gistemp/.