Friday, May 14, 2010

CSIRO should see if there was medieval warming Down-Under

Because we just don't really know for sure. One of many things about the Earth's climate that we either understand poorly or not at all.
THE deferral of Australia's emissions trading scheme for three years allows us time for additional scientific studies that may be critical in shaping future legislation.

A touchstone in the debate on causes of global warming is the record of global temperatures of past millennia. Most who follow this debate are familiar with the cooling from the 16th to 18th centuries known as the Little Ice Age; this is generally accepted as a global phenomenon. Most are also aware of the Medieval Warm Period covering much of the 9th to 15th centuries. This has been the source of greater debate because, while it is clear in anecdotal descriptions from Europe, such as Vikings growing crops in Greenland, it is less clear whether it is a global phenomenon. The debate has high stakes because the rate of warming and temperatures attained in Europe during the MWP are of similar order to the warming of past decades. If the MWP were to be proven to be global, then the basis of present science stating that industrial-era carbon emissions are the dominant cause of today's warming would be significantly undermined.

One of the giants of global warming science, Wally Broecker of Columbia University in New York, wrote a discussion in 2001 of evidence for the MWP being a global phenomenon, concluding tentative support for its global nature. Three years later, Phil Jones, now director of the Climate Research Unit, East Anglia, co-authored a review that concluded the MWP was a regional phenomenon. The IPCC4 report of 2007 concluded similarly; curiously, Broecker's paper did not get a mention.

Posted via email from Garth's posterous

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