The tree rings "prove [the] climate was WARMER in Roman and Medieval times than it is now," the British newspaper the Daily Mail reported last week, "and [the] world has been cooling for 2,000 years."
Nope, this study looks only at tree data from Europe (hence, regional; not global), and tree ring proxy data is not comprehensive for the history of climate, as trees only survive so many hundreds or thousands of years. That's why climatologists use other proxies like Ice cores, ocean sediments, coral analysis, etc. to go back hundreds of thousands of years. Here's what I posted in another thread when this study came up. (Interestingly, Dr. Michael Mann, the hockey stick researcher, came to a similar conclusion as this study in one of his papers).
[youtube:3pkh1unx][/youtube:3pkh1unx]
Uploaded by ChangingClimates on Apr 16, 2010
Peter Brown from Rocky Mountain Tree Ring Research explains dendrochronology and how we can use it to understand the climate.
It’s been a tough few months for tree-rings, perhaps unfairly. Back in April,
we commented on a study
[that one of us (Mike) was involved in] that focused on the possibility that there is a threshold on the cooling recorded by tree-ring composites that could limit their ability to capture the short-term cooling signal associated with larger volcanic eruptions. Mostly lost in the discussion, however, was the fact–emphasized in the paper—that the trees appeared to be doing a remarkably good job in capturing the long-term temperature signal—the aspect of greatest relevance in discussions of climate change.
This week there have been two additional studies published raising questions about the interpretation of tree-ring based climate reconstructions.
click on the link for a detailed description of the scientific method in the papers and what it means in the big picture of climate data.
Tree ring data, like all proxies, has its limitations, which is why multiple proxies are used and factored into reconstructions of past climate (aka paleoclimate)
Progress in reconstructing climate in recent millennia
gavin @ 3 September 2008
The Value in Multiple Proxies
Michael Mann
[url=http://www.sciencemag.org" onclick="window.open(this.href);return false;]http://www.sciencemag.org[/url] SCIENCE VOL 297 30 AUGUST 2002
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