Phil Jones on the Medieval Warm Period

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Q&A Part One: Prof. Phil Jones on the MWP

Phil Jones is director of the Climatic Research Unit (CRU) at the University of East Anglia (UEA), which has been at the centre of the row over hacked e-mails.

The BBC’s environment analyst Roger Harrabin put questions to Professor Jones, including several gathered from climate sceptics.

Here’s the question about the MWP:

There is a debate over whether the Medieval Warm Period (MWP) was global or not. If it were to be conclusively shown that it was a global phenomenon, would you accept that this would undermine the premise that mean surface atmospheric temperatures during the latter part of the 20th Century were unprecedented?

Here’s Phil Jones’ reply:

There is much debate over whether the Medieval Warm Period was global in extent or not. The MWP is most clearly expressed in parts of North America, the North Atlantic and Europe and parts of Asia. For it to be global in extent the MWP would need to be seen clearly in more records from the tropical regions and the Southern Hemisphere. There are very few paleoclimatic records for these latter two regions.

Of course, if the MWP was shown to be global in extent and as warm or warmer than today (based on an equivalent coverage over the NH and SH) then obviously the late-20th century warmth would not be unprecedented.

Thanks, Phil.  Now, let me help you.  There may indeed be very few paleoclimatic records for the tropics and the Southern hemisphere, but there are data.  Plenty of data.

In Antarctica, there are very old glaciers, and cores samples have been extracted.  Would it not make sense to have core samples analysed to see what could be calculated about temperatures and CO2 content from, say 1 AD to the present?  So far, researchers have concentrated on the great ice ages, but nothing has been published about the last two millennia.

We know that in the northern hemisphere, temperatures declined markedly during the fourteenth century.  The Maori people, indigenous in NZ, were established by the beginning of the fourteenth century and were settled in both the North Island and the South Island.  Archaeological records of the population distribution of Maori at the beginning and end of that century could be very revealing.  It has been suggested that there was a large-scale shift in the Maori population from the South Island to the warmer North Island during that century.  If that can be confirmed, the most probable reason would be climate.  The Maori at the time had no tailored clothing and no shoes.  Without those, the snow and ice in the South Island would be very uncomfortable.

Core sample from the New Zealand glaciers might also give us some idea of climate changes in NZ between 1000 AD and 1500 AD.

There are kauri trees in New Zealand that are more than two thousand years old.  It is now illegal to fell them, but there are still plenty of stumps.  Tree-ring proxy data just waiting to be collected.

If Climate Change science claims that the twentieth-century warming is unprecedented, then it must rigorously test the claim.  The science is well-resourced and well-funded.  Why has it not gone looking for evidence of the climate in the Southern Hemisphere during and after the MWP?  Given Phil Jones statement highlighted above, it would seem to be very important.

References:

BBC Interview with Phil Jones: http://news.bbc.co.uk/2/hi/science/nature/8511670.stm

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