Hey guys. I've been having trouble finding a topic to write about this week, so I've decided to re-visit an old issue. People familiar with my writing know I have spent a fair amount of time examining what effect human adjustments to temperature data have had on temperature records. This has mostly focused on the work of the (questionably named) BEST group.
I am not going to re-visit the not insignificant history of this topic today. If you want to read a bit about it, this post should give you a bit of an introduction to the matter. There is one historical point I do need to bring up though. A year and a half ago, in April of 2015, the head of the BEST project Richard Muller gave an interview in which he said:
“Furthermore, because of the interest, we re-analyzed all the data with ZERO adjustments, just to see what we would get. These results have been made available online. What we found was that the conclusions we had previously drawn were unchanged. The data are available here
You can read up about the trials and tribulations surrounding that article here if you would like, but the salient point is the data Muller referred to has never been published. It had not been published in April of 2015 when the interview was given, and it has not been published as of today, in August of 2016.
I don't know why Muller claimed data had been published when it had not. I don't know why that data has never been published. That's a matter for another day though. The reason I bring this up today is I want to point out anyone hoping to analyze the effect human adjustments to recorded data have on the BEST temperature results will face the obstacle of the BEST group falsely having claimed to publish the data which would make that possible without completely redoing the BEST analysis.
Fortunately, as you may have noticed while reading the posts I linked to above, the BEST group has shared that data with me. Unfortunately, that only happened after we exchanged a number of e-mails and I publicly criticized them (multiple times) for failing to publish data then turning around and claiming it was published. Still, the result is I have the data. Because of that, I've spent some time comparing the BEST adjusted and unadjusted results. This is what BEST said of them in February of 2015:
The global time series is important, for example, if we want to make estimates of climate sensitivity or if we want to determine how much warmer it is today than in the Little Ice Age or if we want to compare today’s temperature with the temperature in the MWP or Holocene or if we want to make arguments about natural variability or anthropogenic warming.
Figure 1. Unadjusted data results are shown in the blue curve. The green curve shows the results if only metadata breakpoints are considered. The red curve depicts all adjustments.
As Figure 1 illustrates the effect of adjustments on the global time series are tiny in the period after 1900 and small in the period before 1900.
While I was critical of the blog post that was said in at the time, I was unable to do any real examination of what they said due to the fact they had not published the data one would need to check their claims. By the time I obtained any of the data, three months had passed and people had stopped talking about the post. As such, most people were unaware the BEST group's claim "the effect of adjustments on the global time series are... small in the period before 1900" was incredibly misleading.
At the time, I pointed out at the time, the BEST adjustments altered their temperatures in 1850-1900 period by roughly 15-20%. That seemed a bit larger than "small." However, it was only months later I realized the effect was much greater than 15-20% prior to 1850. For some reason, the BEST team chose not to show the 1750-1850 period in their graph. If they had shown it, this is what people would have seen:
As with the BEST figure, the Red line is the final result. The blue line is what would happen if no adjustments were made. The green line is what would happen if only some of the adjustments had been made. To get a better look, let's remove the blue line and smooth the data a bit more:
Here, we see there are differences of over half a degree at some times. That's more than 25% of the change in temperature the graph shows. Would any person reading that blog post have suspected such a large effect when the BEST team said it was "small in the period before 1900"? I don't think so.
And that's just the maximum difference in temperature at any single point. That doesn't account for the fact adjustments sometimes cool the results and other times warm them. Let's get a complete picture of the effect adjustments have:
For a 50 year period, BEST's adjustments warm their results by about half a degree. Then, BEST's adjustments switch to cooling, again by about half a degree. This cooling effect deminishes until about 1940, at which point adjustments have no effect. After 1940, adjustments again warm the results. This final change is smaller than previous ones and tapers off as we reach current times.
BEST's adjustments have a net effect of a degree change in temperatures. That is 50% of the total amount of warming BEST finds in its final results. You wouldn't know this though because BEST chooses not to publish these results anywhere. Even worse, when BEST publishes graphs depicting these results, it cuts off 100 years of its temperature record, hiding much of the effect their adjustments have.
I get the uncertainty in the BEST results prior to 1850 is quite large, but that does not justify going around telling people the effect adjustments have on its results are "small in the period before 1900" while conveniently failing to show 100 of the 150 years worth of results they have before 1900.
Now, the point of discussing this topic is not to criticize BEST. While I think criticism would be appropriate, the topic I wish to discuss is actually a different one. I want to talk about what effect these adjustments have on how people should interpret the global warming issue.
That'll be the subject for my next post though. This post has already run long, and I think it stands on its own well enough. People certainly deserve to know groups like BEST make misleading claims about the effect adjustments have on their results, choose only to display that data which appears to support their misleading claims, choose not to publish the the data which would let people examine the effect of adjustments themselves, then turn around and give interviews in which they falsely claim that data has been published.
As a final note, I should point out the results shown in this post are only for land temperatures. They do not include any data for ocean temperatures. Oceans tend to warm more slowly than land does, so the total amounts of warming will be noticeably different. Other differences may exist as well. I'll discuss that in the next post as well.