L'Ombre de l'Olivier

The Shadow of the Olive Tree

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28 February 2008 Blog Home : February 2008 : Permalink

Sympathy for Climate Scientists

I have a certain amount of sympathy for the scientists involved in studying the global climate. The sympathy is due to the fact that they are studying a complex chaotic system and looking for trends in the 0.1-0.5 °/decade range from data that
  1. exhibits variation in the 40°/year range (minumum January temps of -5°c max august temps of +35°c are common over quite a lot of the temperate world - mid-continental higher lattitude locations often show more, tropical locations may show less)
  2. is measured by equipment and data recorders that may exhibit significant instrumentation biases and these biases may change dramatically when a sensor is replaced or a new recorder starts taking the data
  3. is further buggered up by local changes in the environment (urban heat islands, asphelt, changes in land use etc.) that again seem to be a good order of magnitude greater than the underlying trend
  4. is even further buggered up by changes of location and other factors which may well not be properly documented.
  5. and finally where reliable data is only available for a few decades in a few parts of the world (yes some good data is available for over a century but the majority isn't)
The result of all of this is that the signal to noise ratio is clearly more 1:100 instead of 10:1 as is common in many other data analysis examples. Hence determining trends is clearly going to be very difficult and hence my sympathy. This is particularly difficult for the paleoclimatologists who try to figure out what the temperature was in the centuries before mankind had thermometers and the like.

However I do think that climate scientists who make blanket "consensus" statements and who react to criticism by attacking the credentials of the critic do their cause no good at all. I do firmly believe that despite all the argument most climate researchers are basically honest and do believe that the science shows that the earth is warming. Indeed I too think the science shows that the earth is warming - that is to say I think you'd be an idiot to think that 100 or 200 years ago the earth was warmer than it is today.

Where I tend to lose agreement, and lose sympathy, is the way that the warming of the earth is automatically assumed to be caused by human activity and frequently to claim that the current global temperature is unprecedented etc. etc. To put it very simply, I'll believe the earth is above a record temperatures in the recent past when grapes grow in Greenland. We know the vikings grew wheat there, we know that you can't do that today, hence by implication Greenland is not as warm now as it was then. Unless someone can either
  1. come up with a convincing reason why Greenland's weather is a fluke and not representative
  2. come up with proof that Greenland is as warm now as it was c.1000 years ago
I'm going to remain highly skeptical that there is serious global warming. And I'll remain equally skeptical of a human cause until it can be shown that there was another reason for the temperatures 1000 years ago and that that reason does not apply now.

I'm also highly skeptical of the models because of artifacts like this which seem likely to produce spurious correlations. This means I have a lot of problems with many of the concepts of PCA (excellent explanation of how PCA works here, here and here) and how many scientists (Mann, Hansen for example) use PCA to detect spurious data points and add corrections to particular data series.

Which leads me back to another reason why I have so much sympathy for climate scientists. Their leaders have predicted disaster after tragedy and used that as a way to extort money from the rest of us. If the whole house of cards turns out to be built on garbage initial data then the whole pack of them are going to need to find a job suddenly and they won't have many qualifications. This might possibly explain why they seem so keen to defend the "consensus" and attack the critics. I'd do the same if my job were threatened too.