“Paleo-clamatology“. Anthony Watts disparages scientific studies until he finds one that suits him. Incomplete data, cherry-picking, needs confirmation, wait for new data, they “don’t share”, whatever he can come up with to brush inconvenient research aside. But if he likes the conclusion the paper is immediately the Holy Grail.
In the case of this report from Nature about oxygen-18 isotopes in molluscs as paleoclimate indicators, Anthony thinks it will “surely stick in the craw of many who think we are living in unprecedented times of warmth“. He also ‘cautiously’ declares “the data resolution is incredible.” Good skepticism there, Anthony.
Now this kind of data is very interesting. It will be exciting to watch the study’s reception by knowledgeable scientists and how it develops under further scrutiny and deeper analysis. I hope to hear a lot more about it.
But a few things stick out in the context of Anthony’s praise: First, the data is from a single Icelandic bay. Not a global signal. Second, the author says “What we’re getting to here is palaeoweather.” Weather ain’t climate, right Anthony? Third, the presented data stops at 1600 AD, well before reliable direct temperature measurements were available or the onset of what some people call Global Warming.
Clams in Iceland whisper to Anthony that there is no Global Warming. Well, in one bay in Iceland anyway. Psst. See that downward trend on the end? It's 400 years ago. Click to enbiggen.
I bet Dr. William Patterson is about to find he has some creepy new friends that will be hard to shake.
Wott's Up With That? 
Wow! Science broke out at WUWT.
I just printed out the paper (available here, I think – site is down right now) and there are a couple of points that the commenters are missing. First, Mann’s reconstructions do not rely solely on tree rings; Second, Mann, et al. 2009 showed that the region around Iceland was considerably warmer during the Medieval Climate Anomaly (described here), particularly from 950 to 1100, at which time there was a sharp drop in temperature, and around 1200, at which time there was some recovery. The LIA also matches up nicely. The “Roman Warm Period” reported by Patterson, et al. is not during the time frame covered by Mann, et al.
Overall, I think that this is another promising temperature proxy, and Richard Alley agrees. Generally speaking, these results support other regional temperature reconstructions. In the WUWT comments, Leif Svalgaard and Phil. try to talk sense. Phil. notes that there seems to be some selection of what time periods (known warm and cold periods) were examined, based on other sediment data.
[I agree that this is a promising technique. The problem with Anthony’s conclusion is that he’s only looking at extremely local result and extrapolating (surprise!) – Ben]