Andrew
If you check out Lyon and DeWitt doi:10.1029/2011GL050337, 2012 you
will see that reducing sea surface temperatures in the right place could
be beneficial. You would of course have to knoew where the right place was.
Stephen
Emeritus Professor of Engineering Design
Institute for Energy Systems
School of Engineering
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University of Edinburgh EH9 3JL
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Tel +44 131 650 5704
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On 24/02/2012 13:59, Andrew Lockley wrote:
Interesting article showing relatively small precip change in
MesoAmerica resulted in civilisation collapse. Apologies for lack of
paper. A cautionary tale for SRM, perhaps?
http://www.bbc.co.uk/news/world-latin-america-17149812
Mild drought caused Maya collapse in Mexico, Guatemala
Relatively mild drought conditions may have been enough to cause the
collapse of the Classic Maya civilisation, which flourished until
about AD950 in what is now southern Mexico and Guatemala.
Scientists have long thought that severe drought caused its collapse.
But Mexican and British researchers now think that a sustained drop in
rainfall of only 25-40% was enough to exhaust seasonal water supplies
in the region.
The findings were published in the journal Science.
The research was conducted by the Yucatan Centre for Scientific
Research in southern Mexico and the University of Southampton in the UK.
Scientists used advanced modelling techniques to estimate rainfall and
evaporation rates between AD800 and 950, when the classic Maya
civilisation went into sharp decline.
They found that a relatively modest decline in rainfall was enough to
deplete freshwater storage systems in the Yucatan lowlands, where
there are no rivers.
Future warning?
"These reductions amount to only 25 to 40% in annual rainfall, but
they were large enough for evaporation to become dominant over
rainfall, and open water was rapidly reduced," Professor Eelco Rohling
of Southampton University told the Press Association.
"Societal disruptions and abandonment of cities are likely
consequences of critical water shortages, especially because there
seems to have been a rapid repetition of multi-year droughts," he added.
The reconstructed droughts are similar in extent to some predictions
for the near future of the same region as a result of climate change.
"There are differences too, but the warning is clear - what seems like
a minor reduction in water availability may lead to important,
long-lasting problems," Professor Martin Medina-Elizalde said.
"The problem is not unique to the Yucatan Peninsula, but applies to
all regions in similar settings where evaporation is high," he added.
Archaeologists have long been intrigued by the collapse of the Classic
Maya civilisation, which flourished for around six centuries and
developed sophisticated architecture, mathematics and culture.
Other studies have variously blamed social unrest, disease and
deforestation for its demise.
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