Who understands global climate change?

Not me, that’s for sure. I’ve no doubt that command-and-control advocates would have trouble finding a better excuse to tell everyone what to do than to promise us that, if we don’t cooperate, we’ll all be flooded, starve to death, and die of thirst. Yet, maybe there is something to it.

I count on our friends at the Heartland Institute to debunk the climate change myths, if that’s what they are. The Feb ’09 issue of their Environment and Climate News presents some data, directly from one of Jim Hansen’s web sites, which tends to cast some doubt. Basically, they say that Hansen seems to have incorrectly adjusted data for the growing city of Santa Rosa, CA, so that it shows an increasing temperature trend where none exists in the original reports.

There’s no sign that James Taylor, author of the article, ever asked Hansen or his agency to explain the adjustments, but on the face of it I did find it strange to see that, in a growing city, Hansen felt that the weather station would under-report temperature increases.

So I set out to learn what had happened to the Santa Rosa weather station. What I discovered, after looking around a bit, was that the latitude (35.0 n) and longitude (104.7 w) of the data Taylor presented as Santa Rosa, CA, was, in fact, Santa Rosa, NM. Here is the unadjusted data and here is the adjusted.

But that still leaves the question, why would it be adjusted to show an increase not present in the original data? Let’s start by looking at the history of the weather station in Santa Rosa, NM. It turns out that there have been several weather stations in Santa Rosa over the years, a total of 15 stations in Guadalupe County, of which three remain in service. None of the 15 is located at 35.0n, 104.7w, and none shows data as early as 1907, when Hansen’s series (raw and adjusted) begin. Now, it would be possible to retrieve the data for these stations and perhaps figure out which Hansen’s crew used, but I haven’t done that. Rather, whichever it is, I want to know
how the adjustments are done.

It turns out that it is possible to find this out, at least in general terms, from a paper(pdf) posted on one of Hansen’s sites. Basically, it seems that they assume that, if readings at a local station differ inconsistently from those around it, these differences likely are due to a problem at the local station, so they adjust the temps up (or down) to reflect what’s happening around it. The authors state that the impact of the adjustment on measures of global climate change are likely negligible, which makes sense to me. After all, if surrounding stations show a change, whatever local effects might impact a local station probably aren’t globally important.

So does that mean that we should believe everything Hansen tells us about global climate trends? We’re finishing up the coldest January in 24 years around here, and apparently it’s been colder than normal in a lot of places.