NASA Climate Calculation Error
My brother sent me this week a copy of an article in the NY Sun that was hard for me to believe. It seemed incredible, and I figured there must be some mistake. So I looked it up. And, there appears to be no mistake.
First, the article, titled An Inconvenient Truth. Seems that NASA climate research department publishes temperature data, and has been for the last few years pointing out that each year in the 2000's has been very hot in the US in comparison to the last millennium. This was big news in January of this year, when they reported that 2006 had been the hottest year in the US of the previous 112 years (see, for example, this Washington Post article).
Turns out that the numbers were wrong. Earlier this month, Steve McIntyre, a climate researcher in Toronto, got suspicious about the numbers because of some peculiar anomalies that showed up out of the blue in 2000. He did some checking, some reverse engineering, and determined that the US numbers had been significantly off since 2000 (which, in some way that I don't understand, affects previous numbers as well). About a week later, NASA acknowledged the change and quietly adjusted their numbers.
I've been digging into this this morning to find more detailed information, and I'll pass along what I've discovered.
Anthony Watts has the best technical summary of the situation I've found. (Steve McIntyre's site is down, possibly because of a DOS attack.)
Roger Pielke also has a writeup, and the comments section has quite a bit of opinion and links to other information.
If you're interested in the raw data, here's an archived copy of the data before the update, and a direct link to the updated data. Note that you won't find any mention of the update on the NASA site itself.
The RealClimate blog has a post from Gavin Schmidt, a climate scientist at NASA, arguing that the differences are statistically insignificant and not worth mentioning.
So, what do I think?
Well, in the first place, it seems that the bulk of the comments on the Watts and Pielke blogs are taking this form: "See, global warming is disproven, because temperatures aren't rising! No hockey stick!" Well, not really. I mean, it's not like before this adjustment, NASA was saying that 1998 or 2006 were huge amounts hotter than 1934. They were pretty much in a dead heat even then. So, this doesn't seem to "disprove" anything.
On the other hand, there a number of responses that take this form: "If they can't see this type of problem, how reliable is the rest of their data"? I think there's some validity there. This isn't the first time that McIntyre has found data and calculation problems in widely-accepted (and widely propagandized) climate numbers. Every time something like this happens, my confidence in the reliability of the scientific research drops a bit.
I'm not convinced by Gavin Schmidt. I agree with him that the change in 1998 is statistically insignificant. However, it seems to me that the changes from 2000-2006 are much more noticeable. Quoting Gavin: "The net effect of the change was to reduce mean US anomalies by about 0.15 ÂșC for the years 2000-2006." Over a tenth of a degree is extremely significant for short-term climate change. Those sorts of changes have been used very recently (as I pointed out in my Washington Post example) to raise concerns of accelerating changes and impending doom. More than a tenth of a degree difference? That changes the picture in a big way.
It is worth mentioning that these are only US numbers, and they don't seem to make any significant difference in the global numbers.
But I would feel quite a bit better about the scientific honesty of the NASA scientists if they would publicly and prominently acknowledge this flaw in their numbers, and try to explain how they could make such a ridiculous mistake and not catch it for 7 years. Their dismissive attitude makes sense to me only from a political perspective, trying to control the media presentation of the information... and that does not make me confident about the impartiality of their science.
It also surprises me that the purportedly ultra-effective Bush administration politics-overriding-science machine wasn't able to catch this one and use it. Strangely, it seems that NASA (which, I believe, is part of the Bush administration) isn't taking the correct conservative political line here. Interesting.
Mark