Speaking of the Medieval Warm Period:
Scientists confirm positive CO2 feedback

(The last paragraph.)

By chance yesterday I just finished reading Fred Pearce\'s New Scientist article, 18 March 2006. Sorry my reading is so out of date but whenever I read the magazine in bed I fall asleep after a few paragraphs.

But the arguments are still relevant.

The second graph on the web page shows the 2001 IPCC northern hemisphere reconstruction for 1000 - 2000 compared with graphs for the same area by Jones 1998, Briffa 2001, Esper 2002, Huang 2004, Moberg 2005, d\'Arrigo 2006 plus the recent instrumental record. The reconstructions are variously based on tree rings (with and without the controversial bristlecone pine data), corals, ice cores, historical records, lake and ocean sediments, boreholes, and records of glacier length. None of these northern hemisphere reconstructions shows much of a medieval warm period whose geographical extent is uncertain.

Regional temperature changes in reconstructions are quite large but they usually cancel each other out.

Thanks for the link. I suppose the big question is not \'is the climate warming\' but is it anthopogenic, a natural cycle or a mixture of both. So keep on crunching numbers until there is an answer.

Every reconstruction shows definite, though not constant, warming for about the last 80 years. The recent (to 2000) rise in the instrumental record is sharper than the reconstructions.

The shape doesn\'t look like a perfect hockey stick but it still looks approximately like a hockey stick.

What prompted my search was the \"Hocky Stick\" graph used by the IPCC without the Mededival Warm Period or the Little Ice Age in evidence. Even with my limited knowledge of Earth Science I knew this was wrong.

There are nice little essays on a variety of such issues at Skeptical Science, including Was there a Medieval Warm Period?

Esssentially the question is whether you suppose that what is the case in a particular region (e.g. a Medieval Warm Period in and around Europe) is actually the case everywhere in the world (e.g. both hemispheres). It could be, in which case the Hockey Stick should show it. But if the Medieval Warm Period and the Little Ice Age are regional and not global events then the Hockey Stick - which is a reconstruction of global temperature - should not and will not show them. So for you to be worried about the Hockey Stick on this basis you would have to believe that the Medieval Warm Period and the Little Ice Age applied to the whole world - and that requires convincing evidence.

Unfortunately, there are a lot of unscrupulous people out there who will use these kinds of arguments without ever acknowledging the confusion of local with global. When challenged they simply move on to another topic.

I have read on verious web sites and articles that senior people from the IPCC panel have resigned over the years because of the unscientific cherry-picking of data to suport their claims of anthopogenic climate influence, culmiating in the walk-out of the IPCC deligation to the Russian Academy of Science in 2004 when asked a question, the aswer to which was contradictory to the IPCC position.

Hi Sprinterst, welcome to the forum.

Could you please give us links to reports of the incident you describe?