I have been quiet of late in part because of real world obligations, and in part because I’ve been trying to do a little “communications outreach” at social media sites like Reddit. Over at their anything but skeptical “climate skeptics” sub-message board, a handful of people spam links from the same handful of denialist websites day after day (though some discussions are more productive than others). Today, I noticed a link from WUWT that was terrible even for Watts’s incredibly low standards. So much wrong packed into so few sentences. What follows is a brief fisking I undertook in the Reddit comments, that might be useful to anyone looking for a rebuttal.
It follows that temperatures must have been higher than those of today’s during that first settlement of Greenland which lasted from approximately 900 until the mid-1400s AD, when these settlements died out.
No. It follows that temperatures were probably warmer for longer than the modern period until recently, but it does not follow that the recent warming, which is unearthing the items described, has not exceeded the medieval warming of Greenland. And in fact, we can look at the Greenland ice core record to see that it has:
This plot was from the last time WUWT tried to promulgate BS about warmer than present Greenland temps, showing the GISP2 ice core and GRIP updates scaled to GISP values for the modern warming.
Yet the whole reason for the existence of the Intergovernmental Panel of Climate Change (IPPC)
The IPPC is it?
is to thrust upon the world’s population the idea that industrialisation in the West over the last 100 years and our profligate use of fossil fuels is producing a run-away heating of the planet
This is a strawman on several counts. We’re not worried about a “run-away” warming like that on Venus. We’re worried about changes to climatic norms that will prove more detrimental than the cost of limiting emissions to avoid those changes.
through the emission of greenhouse gases, mainly CO2, which unless checked will lead to [the planet's] — and humanity’s — death.
I’d like to see the cite for that from any of the ARs. Again, strawman.
So the possibility that temperatures were higher in the past in any part of the world was a thorn in the sides of those Climatologists who are wedded to the whole idea of Anthopogenic Global Warming (AGW), also known as Climate Change.
Again, this is false. Warmer than present temperatures undeniably took place in Earth’s geologic past, this has no bearing on the reality of anthropogenic warming or its potential to disrupt climatic norms.
Unfortunately for them, an English Climatologist, Hubert H Lamb, first formulated the idea of a Medieval Warming Period (MWP) in 1965 and other surveys have found that this warming did not just occur in the northwestern hemisphere but was global (6).
Lamb’s maximum warming took place hundreds of years after (i.e. 1100-1300) the peak warming of the NH is now recognized to have taken place (prior to 1000).
The IPCC FAR curve, based on Lamb, along with the updated CET instrumental record in blue with the same 50 year smoothing (Jones 2009).
NH paleoclimatic reconstructions from Mann 2008, Moberg 2005, Ljungqvist 2010, and the NCDC instrumental record, courtesy of Zeke Hausfather at The Blackboard
Lamb did not believe that the Medieval Climate Anomaly (or “Medieval Warm Epoch” as he originally called it) was a period of continuous temporally and spatially coherent global warming, but rather that it was more pronounced in the Atlantic Northern Hemisphere. You can see Lamb’s own discussion of the subject here (note, I haven’t read the other contents of that page beyond verifying that the quotes from Lamb’s writings are correct and in context. I’m in a hurry and couldn’t find a publicly accessible version of Lamb’s texts. If the guy starts talking about Lizard people, disregard his comments and stick to what Lamb says).
Much like Lamb, modern paleoclimate scientists believe the MCA was characterized by a warm North Atlantic, giving rise to unusual warmth in Western Europe and Eastern North America. Like Lamb, they believe that the MCA was marked by cooling of much of the North Pacific and Asia.
Unlike Lamb, they have a wealth of paleoclimatic and physics-based modeling data that has only become available in past several decades. The MCA seems to have been dominated by persistent La Niña-like and positive NAO conditions, similar to but differing in origin and some specific consequences than Lamb’s proposed proximate causes.
But Dr David Darning (University of Oklahoma College of Earth and Energy) in his recent testimony to Congress (7) said ‘…I received an astonishing email from a major researcher in the area of climate change. It said “We have to get rid of the Medieval Warm Period”’
Where is this email? Why quote this “Darning” instead of the email itself?
Possibly because it’s an apocryphal quote, based on the innocuous comment by Phil Jones indicating a desire to reconstruct temps far back enough to capture the entirety of any MCA: “it would be nice to try to “contain” the putative “MWP”, even if we don’t yet have a hemispheric mean reconstruction available that far back”.
Note that “Darning” does not actually appear to exist, and this claim should be attributed to David Deming, apparently from back in 2006.
In 1998 a graph was produced by geophysicist Michael Mann, known as the Hock Stick Graph’, which managed to almost air-brush out of existence the Medieval Warming Period .
Mann et al. 1998 only went back ~600 years, and said nothing about the time of the MCA.
This was published in the eminent scientific magazine Nature and also in several places in the IPPC Report of 2001 and created a world-wide sensation. Here was proof positive the world was overheating and it was All Our Fault.
As has been pointed out exhaustively, the millennial NH reconstructions say very little on the issue of attribution, and indeed if you throw out all of our late Holocene reconstructions, that would have virtually no impact on the evidence for attribution of the present warming to human causes.
However, investigation of the graph by historians and climatologists who doubted the existence of global warming, brought criticism centred around the statistical method used and the associated computer programme. It was eventually called the most discredited study in the history of science
The author of this article was eventually called the dumbest person in the history of dummies. I was eventually called the tallest matador in all of Spain. Gee, this is fun!
and quietly dropped by the IPPC from the latest 2007 IPPC report for policy makers.
IPCC AR4 Figure 6.10: Records of NH temperature variation during the last 1.3 kyr.