Arguments
Al Gore and Dr Thompson's thermometer
Posted on 15 November 2007 by John Cook
Steve McIntyre from Climate Audit has uncovered another error in An Inconvenient Truth. Al Gore argues that temperatures during the Medieval Warm Period were less than modern times, refering to the work of Dr Thompson (the graph is given the folky title of Dr Thompson's thermometer). However, where did this graph actually come from?
Dr Thompson's Thermometer was taken from Tropical Glacier and Ice Core Evidence of Climate Change on Annual to Millennial Time Scales (Thompson 2003). Specifically, from Figure 7d (rotated to match Al Gore's graph courtesy of Climate Audit):
While the graph was published in Thompson's paper, the actual data is a combination of Mann's hockey stick (Mann 1998) and CRU's surface measurements (Jones 1999). So Al Gore did err in attributing this graph to Thompson. What is the significance? Gore was trying to make the following point:
"As Dr Thompson’s thermometer shows, the vaunted Medieval Warm Period (the third little red blip from the left below) was tiny in comparison to the enormous increases in temperature in the last half-century - the red peaks at the far right of the graph."
Since Mann's study in 1999, there have been a number of proxy studies reconstructing past temperature, using a variety of proxy methods such as tree rings, bristle cones, stalagmites, coral, etc. The results are published in Surface Temperature Reconstructions for the Last 2,000 Years (freely available online). In summating the various studies, the NOAA came to the following conclusion (there's a lot more so it's definitely worth a read):
The similarity of characteristics among the different paleoclimatic reconstructions provides confidence in the following important conclusions:
- Dramatic warming has occurred since the 19th century.
- The recent record warm temperatures in the last 15 years are indeed the warmest temperatures the Earth has seen in at least the last 1000 years, and possibly in the last 2000 years.
So while Al Gore was in error attributing the Mann/Jones graph to Dr Thompson, the main conclusion that temperatures during the Medieval Warm Period were less than modern times is correct. This is an important point and seems to be overlooked in the eagerness to debunk Gore.
By the way, is the NOAA the last word on climate of the last millenium? Why do you pick them as an authority over the NAS, for instance?
NAS supports '98 global warming evidence
Now, setting aside the fact that MWP vs modern temperatures comparison isn't the basis for AGW theory, let's assume that AGW is only 66% probable, and not the >90% that the alarmist Saudi Arabia and Condoleezza Rice concluded in AR4. In constrast, what is the probability that your house is going to burn down? Just think of what you could do with all that money wasted on insurance. Mmm. Money.
Or let's say a bunch of drinking buddies bet you to stick a gun in your face. Only one bullet in the chamber. Spin the chamber. Pull the trigger. Win a $1000 bet. Only a 17% chance of shooting yourself in the face. Just who wouldn't take that bet?
I did a quick search using Google to see what relationship there might be between the authors. In a few minutes--I am no expert in doing such searches and I am not particularly familiar with who these authors are--I found that 10 of the studies were authored or co-authored by Jones, Mann or Briffa. And according to the linked article, together with the search I just did, these researchers have all co-authored papers together. I suggest other people try the same by putting these names in Google and using key words such as 'collaborators', 'global warming', etc.
I have no idea if the remaining authors are collaborators or have close relationships to this group.
I am sorry but how can you call this research independently replicated or verified by independent scientists? Or at least, there is some cause for concern here...
Isn't replication fundamental to science?
And if his work is solid, what has he got to fear? Wouldn't it be better to shut the critics up?
Also, if some of the world's most qualified and respected statisticians conclude that his statistical analysis is in error, why do you regard this as a problem that is 'overblown'?
I don't have any problem with proxy studies that replicate hockey sticks, so long as the studies do not disseminate from the same small group of researchers over and over again. I am not suggesting there is anything sinister here. The gold standard in scientific research is the double-blind test because everyone understands that scientists are human and subject to bias.
If there is solid independent research to back up hockey sticks, why not use it? Why quote 'apparently discredited' research? Whether you feel it is discredited or not is a separate issue. My point is that quoting the same small group of controversial researchers while at the same time misleadingly asserting that the evidence thus presented is independent, is at best disingenuous and at worst dishonest. To put it more bluntly: if the science is solid, you don't need them, so don't use them. Get your hockey stick data from a true independent source and then you have a solid argument to shut the deniers up.
It appears that McIntyre's actual contention is that it is not possible to check Thompson's graph as the ice core data sets it was supposedly derived from have not been archived. This by definition makes them not science because they can not be independantly reproduced or checked.
Mann's famous hockey stick from the IPCC 3rd report has vaninshed from the 4th report without comment but for darn good reason. It might be a good idea to admit it was incorrect and move on.
While CO2 increase may be a contributor to 20th century warming, the MWP, LIA and the Holocene Maximum are all strongly supported in the paleo record unless you cherry pick like crazy. All of these events had temperature changes as large or larger than the 1975-1998 one we're all worried about, and the rate of change coming in or out of them appears to have been at least as great.
I would also disagree with your comment about the MWP and LIA unless you are talking about regional events. The MWP seems to be most pronounced in the Western European areas. What climate reconstructions are you using to draw your conclusions?
Regards,
John
You might note that the current warming is also not universal on the regional scale.
So you are invoking the old "fake but accurate" defense? There is nothing scientific in that argument.
Do realize that you need a mirror to read the lower graph?
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You're taking this hook line and sinker with absolutely no skeptical inquiry at all. A careful review of the evidence convinces me that the opposite is as at least as likely to be true, namely that it could have been as warm or warmer during the MWP as it is now.
The IPCC summary of computer simulations you link above only go back to 1850 and blurs out problems with individual models by replacing the spaghetti curve with a grayed out region. (Errors in the simulations are highly correlated from year to year, the figure makes it seem they are not, which is false and misleading.)
Furthermore, there are no reconstructions of temperatures that *don't include tree ring chronologies* that conclude that the MWP was cooler than it is now. And there is every reason to be suspicious of tree rings as proxies for temperature, given the multivariate relationship between temperature, precipitation, and CO2 fertilization on tree ring growth.
Even if you ignored CO2 fertilization and precipitation as factors, there is an optimal temperature range for any plant: Presumably in their natural climate (the temperature zones for which they are optimized), you will find them near their optimal rate, otherwise you'd find the plants in a warmer climate than they are actually found. Ecology 101. Lower or *raise* the temperature, and you will see a decline in growth rate. One would certainly not expect anything approaching a linear relationship between the two. (Isotopic measurements of δ18O do not suffer from any of these problems, because they are measuring a ratio rather than an absolute quantity.)
I happen to agree that CO2 is playing a role in our current warming trend, but don't agree with Al Gore that it is "appropriate to have an over-representation of factual presentations on how dangerous it is." That's just coded words for lying.
And I am not nearly as infatuated with Mann's work as you appear to be. Even the plots the NAS make the answer to whether the MWP appear much less certain that you are portraying it to be: See Figure 11-1 on page 112: Most of the multi-proxy reconstructions show the modern temperature to be about 0.1-0.2 C above that of the Medieval Optimum, which is probably a smaller difference than the absolute uncertainly in the reconstructed temperature for that period.
BTW, I don't think it's appropriate to hot link to other people's blogs without getting permission first. I would hope you have done so, or would make a local copy of Steve's figure with a hyperlink to his original image.
Douglas