However, I was struck by the urge to tinker with the Web site today. Even if no one reads it, I still enjoy tweaking it. I mostly upgraded various components of the blog to their most recent versions; thus, most of the changes are not very noticeable. I also implemented a new login system. You can now log in with Google/Facebook/twitter/OpenID, or you can use your existing FoC login if you would prefer — you should be able to associate the existing FoC account with a third party login. Let me know if you have any trouble.

I also wanted to write something today because a subject came up (other than health care reform, about which I lack the perseverance to write) that I thought was well suited for regular blogging rather than microblogging.

A few days ago, a leading climate change research center was hacked. Among other things, their private e-mails have been spread around the Internet. Many climate change deniers have latched onto certain portions of these e-mails as proof — not just the smoking gun, but the mushroom cloud!! — that climate change is a big hoax.

The most talked about passage stated,

“I’’ve just completed Mike’s Nature trick of adding in the real temps to each series for the last 20 years (ie from 1981 onwards) amd from 1961 for Keith’s to hide the decline.”

Words like “trick” and “hide” certainly have a negative nuance, hinting that something untoward took place. However, based on my understanding of the matter, this was not the case. Although I feel silly having to cite the definition of a commonly known word, it is probably the simplest way to approach the first commonly cited point in the e-mail.

“Trick: A convention or specialized skill peculiar to a particular field of activity.”

Was this definition the intended meaning of “trick”, or does it instead refer to malicious deception? The answer to this question depends on the meaning of “hide the decline”. Many climate change deniers seem to interpret “hide the decline” to mean that global temperatures are actually decreasing and that any reported rise in global temperatures is the result of manipulation of data — a hoax dreamed up by Al Gore and George Soros. However, surely an enterprising scientist somewhere would notice this, right? Never mind the fact that decreasing temperatures would conflict with numerous separate observations, for example, sea ice thickness, weather patterns, and species extinction.

Therefore, I think it is safe to conclude that the scientists were not hiding declining real global temperatures. So, what were they hiding?

Climate scientists use a variety of proxies instead of actual temperature measurements, such as tree-ring growth and the isotopic composition of polar ice cores. These proxies are necessary to construct models of the global climate thousands of years in the past, since frequent, accurate, and widespread measurement of temperature is a fairly recent occurrence. However, these temperature proxies are not perfect. For example, the tree ring “divergence problem”, whereby the strong correlation between tree-ring growth and temperature considerably weakened after 1960, is well know. It has been reported that in the e-mail, “decline” referred to the decrease in the modeled temperature obtained by using tree-ring data.

In order to deal with large and complex data sets, various statistical treatments must be applied. In this case, tree-ring growth provides good data up to 1960. However, since the correlation subsequently weakened, the “decline” needed to be “hidden”, not because they were twisting the data to fit their political agenda, but because they were constructing a model to fit the observed data.