Posted on 01/29/2008 11:13:13 AM PST by E. Pluribus Unum
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A Global Temperature History of the Past Two Millennia
Reference
Loehle, C. 2007. A 2000-year global temperature reconstruction based on non-treering proxies. Energy and Environment 18: 1049-1058.
What was done
Using data from eighteen 2000-year-long proxy temperature series from all around the world that were not developed from tree-ring data (which provide significant interpretive challenges), the author (1) smoothed the data in each series with a 30-year running mean, (2) converted the results thereby obtained to anomalies by subtracting the mean of each series from each member of that series, and then (3) derived the final mean temperature anomaly history defined by the eighteen data sets by a simple averaging of the individual anomaly series, a procedure that he rightfully emphasizes is "transparent and simple."
What was learned
The results obtained by this procedure are depicted in the figure below, where it can be seen, in the words of its creator, that "the mean series shows the Medieval Warm Period (MWP) and Little Ice Age (LIA) quite clearly, with the MWP being approximately 0.3°C warmer than 20th century values."
What it means
Loehle notes that "the 1995-year reconstruction shown here does not match the famous hockey stick shape," which clearly suggests that one of them is a poorer, and the other a better, representation of the truth. Because of its simplicity and transparency, as well as a host of other reasons described in detail by Loehle -- plus what we have learned since initiating our Medieval Warm Period Record-of-the Week feature -- it is our belief that Loehle's curve is by far the superior of the two in terms of the degree to which it likely approximates the truth.
Reviewed 30 January 2008
Cue up that Aerosmith track again.
Judging by your style of discourse lately, I would guess that you would post an image of your middle finger accompanied by a rhetorical question.
That's not my style - sorry that you think it is. I still don't know what you meant by the rehabilitation process of the temperature record, and to respond to that I need you to explain a little more what you meant.
My hockey stick response was to show that there are now several different reconstructions available. Loehle's is another and different one. It should be pretty clear that the "answer" lies somewhere within the envelope defined by those reconstructions, and the range of possibilities gets larger the further back in time the analysis attempts to go.
So, was the hockey stick bad science? No, but the authors could have been a little more circumspect and respectful regarding inquiries.
Was it something more insidious? Certainly not.
And here's a rhetorical question: were a lot of the critiques of the hockey stick motivated by something other than concerns about its scientific accuracy?
That surface temperature data graph shows the 1940 temperature peak years to be about as warm as the 1980’s and 1990’s. That is incorrect data. You have heard that NASA corrected their temperature data and any relevant temperature graph needs to show the 1940 temperature peak to contain some of the hottest years recorded. As to why the temp chart is so incorrect, perhaps it is not factoring in ocean temps ?
I mean the IPCC showed a global temperature chart that looked like a hockey stick and this alarming chart was printed in the major media to boost support for the Kyoto treaty. Do you really think this was not bad science? I say it was political science used to advance a political agenda. 
Now that the original study has been exposed, we see new, (more credible?) charts to sell the same idea. At some point somebody has to question the veracity of the people who have promoted one lie, got caught, and are now trying to sell another lie.
Before we go any further, are you really of the opinion that the current global temperature is actually .3 degrees warmer than it was at the peak of the Medieval Warm Period as indicated by the graph you posted?
Unresolved issues with the assessment of multidecadal global land surface temperature trends
The correction was for the U.S. The plot shown is for global temperatures and is accurate (the U.S. correction barely nudged the global temperatures).
Rural temperatures actually had a more rapid warming trend, according to this study.
Put it this way; if you add the warming since 1992 to the end point of the Loehle plot, that's about what you get as well. So is there any data that DOESN'T indicate that? (Remember that it's warmed up globally about 0.4 C since 1975. That's a big spike. I'd have to say that the early 1990s were about as warm as the peak MWP -- maybe -- because I'm still not sure about the weighting effect in North America and Europe, where it was most strongly expressed.)
I mean the IPCC showed a global temperature chart that looked like a hockey stick and this alarming chart was printed in the major media to boost support for the Kyoto treaty. Do you really think this was not bad science?
The IPCC process is about evaluating scientific results for the edification of decision-makers. It is not science itself. Therefore, what you describe above is not bad science. Bad science is about poor methodology, erroneous result interpretation, letting a desired conclusion determine the methods of analysis (and many other "bad" practices). We could talk a lot about that; I prefer it to the mixture of policy and science that frequently colors this discussion.
"A continued mode of corrections using approaches where statistical uncertainties are not quantified is not a scientifically sound methodology and should be avoided, considering the importance of such surface station data to a broad variety of climate applications as well as climate variability and change studies."
By the way he cherry picked his sample stations.
So you are stating that the US experienced some of its warmest years (1940's) while the rest of the globe experienced near average temps. How is that possible ?
Since you didn’t answer my last comment, I had thought you were done with this thread, now I find you have been busy pulling links from all over to discount secondary arguments or comments here.
What, exactly, is your interest in all this?
We seem to be able to measure an increase in temps around the world at much greater resolution than before but there also seems to be a growing need to assign blame rather than isolate cause.
How would you characterize your personal position?
Long paper, I skimmed it. Seems like his final conclusion is that to have a better sense of the uncertainty of the temperature measurements, it would be good to have better station records and better-sited stations. Well, gee... it's hard to argue with that. It doesn't, however, invalidate the temperature trends derived from the station data.
Because the U.S. is a region and only 2% of the global surface. I actually authored a thread on this, which features some good illustrative graphics:
A little perspective on the U.S. and global temperature records
Something went wrong with the source links to the original images in the article. I recommend reading my original article. If you don't want to read everything in the comments, the post I recommend you examine is #69.
The plots of U.S. and global temperatures are here:
Bottom line: climate rarely behaves the way that you intuitively think it should (or want it to).
According to a review of the thread, this was your last comment:
It will be interesting if research continues to find some variable that accounts for the oscillations and resolves some of the contentions that seem to be driven by political expediency.
My reply would have been, and is now: "Yeah, it would be interesting." As far as I know, there are lots of oscillations: PDO, AO, AMO, ENSO -- off the top of my head. Multiple oscillating cycles produce some pretty interesting waves, don't they?
What, exactly, is your interest in all this?
Keeping the science straight. The thread touted the Loehle paper as "Because of its simplicity and transparency, as well as a host of other reasons described in detail by Loehle -- plus what we have learned since initiating our Medieval Warm Period Record-of-the Week feature -- it is our belief that Loehle's curve is by far the superior of the two in terms of the degree to which it likely approximates the truth." (This is from CO2Science, a notably biased skeptical source.) So I examined Loehle, examined the correction paper, determined that the correction paper's conclusions aren't nearly so stunning (but this still interesting and is respectable research), and discuss this.
We seem to be able to measure an increase in temps around the world at much greater resolution than before but there also seems to be a growing need to assign blame rather than isolate cause.
Weill, if you identify the cause, then you can easily blame the process identified as the cause, can't you? It IS important for science to identify/isolate the causes of climate change to correctly attribute anthropogenic forcing vs. natural forcing. Once that's done, the anthropoids should be blamed appropriately.
How would you characterize your personal position?
Vertical, fortunately. ;-) But I'm actually not sure what position you're asking me to characterize.
You know, temperature excursions of that magnitude have happened several times in recorded history. Going by this chart, from 1879 to 1912 there was drop of 0.6 degrees C. If we had today's politicians back then they would be calling for a stranglehold on the economy to prevent another ice age. From 1944 to 1956 there was another drop of 0.4 degrees. Or what about that huge increase of .7 degrees from 1912 to 1944, long before most of our CO2 was released? If back in 1912 or 1944 you had glued the recorded temperature record on to a 2000 year chart of proxy data you would have a very scary looking picture.
Temperature spikes happen. But ancient records don't show it because they don't have the one year temporal resolution that we have in recorded history. So it doesn't really mean much to talk about spikes if you don't have anything to compare it with.
Bad science is about poor methodology, erroneous result interpretation, letting a desired conclusion determine the methods of analysis (and many other "bad" practices). We could talk a lot about that; I prefer it to the mixture of policy and science that frequently colors this discussion.
Unfortunately we can't separate the mixture because government scientists who do environmental studies are being influenced and their careers threatened by political forces. So we can't avoid talking about it.
By the way, I neglected to answer your question about the possibility that objections to the Hockey Stick were motivated by other considerations. Yes. Absolutely. I think it was motivated by concern about grand theft Kyoto. Mega-theft. It it were about mating practices of bugs, no one would care. But the Hockey Stick affect was bad science being used by world politicians in a continued, unabashed attempt to grab money and control.
“Weill, if you identify the cause, then you can easily blame the process identified as the cause, can’t you?”
That’s the problem - the skeptic’s position is that we haven’t yet isolated the cause, which means we haven’t identified it.
Given today’s parameters, what would it take to lower the global mean temperature 0.1C?
When we can answer that, we then have to decide if we can afford or accomplish it.
Actually, rural areas that became more urbanized would, as you would expect, have a greater increase in temperature than big cities that are not laying down any new asphalt. More urbanization, more heat island effect, more warming. Of course he had to pose it as a refutation of urban heating. Don't these people get dizzy when they spin like that?
The view of science is that the primary causes are identified; precise percent attribution is still elusive, and also variable.
Given today’s parameters, what would it take to lower the global mean temperature 0.1C?
That's a question requiring a climate model. But let's do a classic back-of-the-envelope guesstimate: 1880-2008 atmospheric CO2 is up 80 ppm and temps are up ~0.8 C (0.6 C 20th century + 0.2 C 21st century).
So the first step of the experiment would be to reduce atmospheric CO2 by 10 ppm and then sit back a decade to let everything equilibrate and then measure the change.
I'm going to need a lot more funding.
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