On February 14, 2023 we announced our Rebuttal Update Project. This included an ask for feedback about the added "At a glance" section in the updated basic rebuttal versions. This weekly blog post series highlights this new section of one of the updated basic rebuttal versions and serves as a "bump" for our ask. This week features "What do the 'Climategate' hacked CRU emails tell us?". More will follow in the upcoming weeks. Please follow the Further Reading link at the bottom to read the full rebuttal and to join the discussion in the comment thread there.
What do you do if you cannot overturn well-established scientific theories by fair means? In the case of climate science deniers, you cheat. You play foul.
This is exactly what happened in November 2009. Sometime earlier, the email server at the Climate Research Unit, University of East Anglia, was hacked (an illegal act in itself). A huge number of emails were stolen, sifted through and a selection was made available for download on a Russian server. The timing of the release was unsurprising, for early the following month the COP15 Climate Summit was due to be held in Copenhagen.
Selectively quoting parts of an email message removes all context. One of the most widely-quoted sentences, that will do nicely as an example, was as follows:
"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) and from 1961 for Keith's to hide the decline."
Those fanatically promoting this conspiracy theory encouraged people to take such sentences at face value. The implication that was intended to be the take-home in this case was that climate scientists were covering up declining temperatures. However – and serial misinformers have a long track-record in this kind of thing - it means nothing of the sort. The people in that email were not talking about measured temperatures. Let's take a look at the context to find out what it really meant.
"Mike's Nature trick" referred to a technique described in a 1998 Nature paper, presenting a 600 year-long global temperature reconstruction by Michael Mann and colleagues. Michael is a palaeoclimate specialist who has for many years used tree-ring growth patterns in ancient wood to reconstruct conditions at the time those rings formed. The basic idea is that in cold, dry years, trees grow more slowly so their rings are relatively narrow and densely-spaced. In warm wet years, it's the opposite.
The "trick" is the technique of plotting recent instrumental data (i.e. weather observations) alongside the reconstructed tree-ring data for the time they overlap. It's a good way of checking if the reconstructed tree-ring data are representative and meaningful. They're no good for anything if they are not.
So, what does the “decline” refer to? It's also known as the 'divergence problem', a point on the timeline beyond which the reconstructed tree-ring data stop being representative and meaningful. This is a well-known issue in certain tree-ring datasets from specific places. What happens is that when plotted against instrumental temperature data, the reconstructed tree-ring data fall away – decline - below the instrumental data. This is a recent phenomenon that only showed up after about 1960. Prior to that, it hadn't been a problem.
Climate scientists started discussing the decline in the literature as long ago as 1995 – by which time they had many years of data showing that, where present, it stood out like a sore thumb. It seems to have been caused by an apparent loss in temperature-sensitivity with respect to certain species of trees growing in certain areas. Something had changed, making affected datasets unrepresentative of actual conditions.
All that ado about nothing. Just how much taxpayer's money was wasted on all the public inquiries that followed is anyone's guess. None were necessary. All you need to remember is that when it comes to climate science deniers, the difference between fair means and foul is at best blurred and more usually non-existent.
Please use this form to provide feedback about this new "at a glance" section. Read a more technical version via the link below!
In case you'd like to explore more of our recently updated rebuttals, here are the links to all of them:
| Myths with link to rebuttal | Short URLs |
| Ice age predicted in the 1970s | sks.to/1970s |
| It hasn't warmed since 1998 | sks.to/1998 |
| Antarctica is gaining ice | sks.to/antarctica |
| CRU emails suggest conspiracy | sks.to/climategate |
| What evidence is there for the hockey stick | sks.to/hockey |
| CO2 lags temperature | sks.to/lag |
| Climate's changed before | sks.to/past |
| It's the sun | sks.to/sun |
| Temperature records are unreliable | sks.to/temp |
| The greenhouse effect and the 2nd law of thermodynamics | sks.to/thermo |
Posted by John Mason on Tuesday, 14 March, 2023
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