Bishop Hill Get digging
Apr 21, 2010 Climate: MWP The European Geophysical Union is going to be discussing paleoclimate at its annual meeting at the start of next month. The papers to be presented look pretty interesting.
Do have a look through and let us know if there is anything exciting in there. I just peeked at Ljungqvist et al which looks at the Medieval Warm Period and the Little Ice Age to see if they were really localised, as is argued by those on the other side of this debate. While the paper only looks at Northern Hemisphere proxies, the authors seem to have reached a rather different conclusion.
We find evidence of a widespread medieval warming culminating in the 10–11th centuries, followed by a gradual cooling into the 17th century, succeeded by a warming from the 18th century that accelerated in the 20th century. Our result also indicate that the warmth in the 10th and 11th centuries was as uniform as in the 20th century. However, with a resolution of only 100 years it is not possible to assess whether any decade in the past was as warm as any in the late 20th or early 21st century.
Reader Comments (11)
"The disadvantage of allowing a low temporal resolution is that the records cannot be calibrated against instrumental temperature observations." That's where Mann went wrong - by attempting a calibration of his proxies against temperature observations he found that the proxies failed - hence his "Nature trick" to "hide the decline". Though whoever thought of rebranding failure as "divergence" should obviously have gone into politics rather than science. There again, by going into Climate Science, he did go into politics rather than science.
One of my favorite pages of graphs is page 3 of "Cosmic Rays and Climate," by Jasper Kirkby of the Geneva based European Organization for Nuclear Research. The multiple temperature proxies show a MWP and LIA for the Northeren hemisphere, but also shown is the advance and retreat of tropical Andes glaciers, all shadowing solar variability.
http://aps.arxiv.org/PS_cache/arxiv/pdf/0804/0804.1938v1.pdf
Don B - Thanks for referral to the EONR paper on cosmic rays and climate. Interesting comment on p. 4:
"There have been numerous other temperature reconstructions for the last millennium...,and their unweighted mean is often used as the combined best estimate. However, this can be misleading since many of the reconstructions share the same temperature proxy datasets, so they are not independent measurements."
Kirkby doesn't seem to put much credence into the 'hockey stick.'
The attempts to suppress the MWP represents the most bizarre aspect of the whole 'global warming' spin machine. Done, I suspect, to curry political favour as much as to 'strengthen' the AGW case, it allowed politicians to use the emotive 'unprecedented warming' soundbite. Ironically, in so doing, it sounded the first alarm bell for so many people destined to become sceptics like myself- for they were aware from their background knowledge that this was nonsense, and that the entire history of the Earth has been one of spectacular natural climatic variability.
May I recommend 'CO2 Science', to any who have not visited it, run by atmospheric climatologists Sherwood Idso and sons Keith and Craig, as an excellent port of call generally, and specifically for their MWP Project and their Plant Growth databases. They are found either via a dropbar from DATA on the main menu bar, or in the middle of the home page:
http://www.co2science.org/
Note that Eduardo Zorita will be participating in the EGU Oral Programme CL1.18: Multi-proxy investigations of European climates of the last millennium. That's refreshing!
Pharos
Just make sure you keep watching Real Climate as well as CO2 Science. If you are a sceptic it gives you this really warm feeling :)
I met someone called Dung some years ago, honest truth, in Vietnam.
Quote "However, with a resolution of only 100 years it is not possible to assess whether any decade in the past was as warm as any in the late 20th or early 21st century." Unquote.
What I see his statement really means and what his statement implies, is, "It is not possible to assess whether any decade in the late 20th or early 21st century was as warm as any decade in the past". Also, with a resolution of 100 years, why is he suddenly talking resolution in decades ? - His proofreader must have been asleep. Very sloppy statements.
from "Reconstructing the past climate variability in Svalbard from the
Lomonosovfonna and Holtedahlfonna 18O ice core records" final statement "It suggests that the climate conditions on Svalbard during the Medieval Warm Period were quite similar to those observed at the present time"
So what we see now is the normal changes in climate, jolly hockey sticks
Pharos
I like the 'Medieval Warm Period Record of the Week' on co2science!
There appear to be 2 Dungs on Bishop Hill! This town aint big enough for both of us and I demand a showdown.
I did not write the above post.