density and width of tree rings shows how warm it was |
during each year's growing season, and thereby
serves as a record of long-term climate trends.
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."Roger Cohen, a fellow of the American Physical Society, reviewing the paper wrote:
That and other articles suggest the current global warming trend is a mere blip when viewed in the context of natural temperature oscillations etched into tree rings over the past two millennia. The Star-Ledger, a New Jersey newspaper, mused that the findings lock in "one piece of an extremely complex puzzle that has been oversimplified by the Al Gores of the world."
If you read the paper, it begs a simple conclusion that the authors don’t make explicitly but is damaging to the AGW ‘cause.’ The authors say that the decline in solar forcing over 2K years was about 6 W/M^2, about 4 x anthropogenic forcing since 1750. Yet the long term cooling was only ~0.6 deg. Then the inferred climate sensitivity for the Northern Scandinavian region must be very small – since the climate sensitivity determines response for both warming and cooling. Also people who argue for an enhanced solar effect on climate via cosmic rays will say that the real solar forcing was much larger and therefore the climate sensitivity is yet smaller.