Seems it’s not so hot after all
In a new paper, published in the journal Energy & Environment, Craig Loehle reconstructs the 2000-year temperature record without using tree rings as a proxy. He gets the following trend. Note the prominence of the medieval warm period and the little ice age, both of which are conspicuously absent from Mann’s hockey stick and various other reconstructions favoured by alarmists such as Al Gore.
He discusses in detail the reasons for omitting the abundant tree ring proxies. Here’s the abstract:
Historical data provide a baseline for judging how anomalous recent temperature changes are and for assessing the degree to which organisms are likely to be adversely affected by current or future warming. Climate histories are commonly reconstructed from a variety of sources, including ice cores, tree rings, and sediment. Tree-ring data, being the most abundant for recent centuries, tend to dominate reconstructions. There are reasons to believe that tree ring data may not properly capture long-term climate changes. In this study, eighteen 2000-year-long series were obtained that were not based on tree ring data. Data in each series were smoothed with a 30-year running mean. All data were then converted to anomalies by subtracting the mean of each series from that series. The overall mean series was then computed by simple averaging. The mean time series shows quite coherent structure. 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 at these eighteen sites.
A lengthy and forthright discussion by people considerably more qualified than I am, and with participation from Loehle himself, can be found at Steve McIntyre’s ClimateAudit site. It’s worth reading before picking holes in the paper.
Update: Something just occurred to me. The pronounced warm period prior to the year 1000 is missing from most reconstructions I’ve seen, because they all cover only the last 1000 years. Those charts, when they haven’t been piped through Michael Mann’s hockey stick maker, include the medieval warm period around 1200-1300 and little ice age around 1700-1800. Turns out if you go back just a little bit more, you get an even higher temperature peak than the medieval warm period. One wonders if the data endpoint selection for the “usual” charts is deliberate.
The most interesting thing about the graph in your story is the scale: over a 2000 year period the average temperature of the planet has vacillated in a range of no more than 1.2 degrees Celsius. So what’s all “climate change” the fuss about?
Good point. If you drew the graph on a scale from, say, zero to 30 degrees Celsius, you’d get a pretty flat line around 14 degrees (if I recall correctly).
You’re citing a study commissioned by a group funded by the forestry industry (the environmental resource for the forest products industry); it’s completely unsurprising that the report would. From their front page: I guess it slots nicely into your own established non-PC outlook. I find it interesting how you accuse, eg, Al Gore, of selectively choosing his source material, but then go ahead and find your own references without indicating their connections with special interest groups.
Here’s one from the United Nations, published last Saturday. http://www.dw-world.de/dw/article/0,2144,2930589,00.html
Ooh, ooh, it’s funded. By the tree people! The money tree people!
Yes, I accuse Al Gore of selectively choosing his source material, though I also accuse him of exaggerating and deliberately lying. Gore’s day job is to be a politician, and to make money out of companies that make money from climate change alarmism. Since he’s on my TV all the time, I hold him to a reasonably high standard.
I have a day job that doesn’t involve making money out of the “green” issue. I don’t run a global political campaign. I don’t have the resources of the IPCC at my disposal. I read one academic paper at a time. When I have time.
So I saw this paper. I read it. It raised some interesting specific questions that I had not considered before, though they did tie in with something that has puzzled me for a while, namely the origin, nature and accuracy of apparently contradictory temperature records.
The discussion about the paper at Steve McIntyre’s site also proved enlightening. So I pointed to both.
Accusing me of selective quotation is a red herring, from which I conclude that you have no answer to the substance of the paper. Same goes for the presumption that the funding of research automatically taints it, and therefore renders its substance not worth considering. By that standard no scientist would ever be credible. An independent publisher accepted it for publication, did it not?
Would you care to comment on the substance of the science of the paper, rather than throwing ad hominem attacks at its author or me for daring to question the wisdom of our kings and masters at the world’s biggest political jamboree?
“Would you care to comment on the substance of the science of the paper, rather than throwing ad hominem attacks at its author or me for daring to question the wisdom of our kings and masters at the world’s biggest political jamboree?”
You miss my point entirely and subsume it in shrillness. I am asking you to re-examine your intellectual rigor. Yes, this spills beyond just this post, and sure, I’m picking on the global warming thing. But whereas I started from a point of debate, my expectation now is that you’ll simply dismiss, with a few slurs for good measure. Probably label them as “ad hominem”; which it’s not, you know, and never was. I didn’t say “you are a bad person”, I said your methodology is sloppy and you have double standards. Your use of ad hominem is the ‘ad hominem fallacy fallacy’: http://plover.net/~bonds/adhominem.html. This does not strike me as the correct attitude of intellectual humility one needs when attempting to reason.
But, fine, whatever. You read the study (by the forestry industry) and linked to the discussion (on the global warming sceptic’s site). When I point out your sources are dodgy, you throw out a “red herring” saying that we should disregard where funding comes from elsewise we need to disregard all science. I think it’s intellectual integrity to say “hey, I wonder if the smoking companies are really doing their best to establish the link between tobacco and cancer?” So, yes, I am afraid that your over-generalization doesn’t apply. The source is important.
But on to the response to your point, that is, the substance of the paper. I’ll do so by refuting the Medieval warm period. I will now point you to the relevant sites (http://www.realclimate.org/index.php?p=11#myth2) and also here(http://www.ncdc.noaa.gov/paleo/globalwarming/medieval.html). Here’s a comparative graph from the wiki. Therefore, I conclude that the data has been massaged to fit the facts. Facts that fit your own particular point of view which is why you present it.
I have now done exactly the same now, simply sourced to support my point of view, and no real debate has happened. Of course, my sources include the “world’s largest collection of weather data”. I guess that doesn’t matter, either. Nor does the fact that they collect data using the apparatus of a political administration actively hostile to Global Warming Data, I suppose.
Furthermore, this guy is saying that tree ring samples are dodgy, but everything’s dodgy 500 years plus+. Only the last 145 years are certain, through instrumentation observation. So you move the debate from what’s observable happening right here and now, to some disputable point in the past. A red herring, again.
I’m an open-minded guy - I’m interested in dispassionate observations about science and I’m willing to listen to the other point of view on Global Warming. It’s just that you’re not convincing and (at least it feels to me that you) rely on shouting down the other side.
You say “no real debate has happened”, but the entire point of mentioning the Loehle temperature reconstruction is to provide an argument in the debate between Michael Mann (and by extension RealClimate.org) and those who think his hockey stick chart was, as Mann himself admitted, created to make the Medieval Warm Period disappear. It adds to the growing body of work — such as Steve McIntyre’s demonstration that Mann’s hockey stick is fatally flawed — which suggests that some commonly-used climate reconstructions are questionable, both on methodological grounds and on the basis of the underlying data that is used.
I agree there are different temperature records — one for the last century or so, another for the last couple of millennia, and yet another that reconstructs climate tens of thousands of year back. I agree that they use different data or proxy data. I agree that one argument does not apply to all of them. But that doesn’t mean anyone is trying to change the subject.
The Loehle reconstruction obviously applies to the second of these — the millennial timescale. It makes an argument about which proxy data are reliable and which aren’t. It doesn’t say anything about the reliability of the “world’s largest collection of weather data”, because that is based on recent measurement data, not historic proxy data. Different arguments apply there, such as those made by Anthony Watts, Steve McIntyre and others that suggest both station siting and the correction factors used to account for the urban heat island effect are problematic.
I’ve seen on one hand convincing arguments from the likes of McIntyre, and on the other some very suspicious defensiveness, dismissiveness, hostility and even outright secrecy from the people — like James Hansen of NASA’s GISS — who’s work he challenges. When Watts began to survey and question the siting of temperature stations in the continental US, Hansen simply removed the list of sites from the internet. When McIntyre pointed out an error in the GISS temperature record, new data was quietly published without so much as a press release to explain it. Therefore I value McIntyre’s recommendations on a particular research paper that presents a particular argument about a particular detail of one particular temperature reconstruction.
That the scientist in question works for a research outfit that serves the forestry industry seems to me neither here nor there — unless and until it is shown that his facts or arguments are actually wrong.