Warmer is Wetter

The Sahel (sub-saharan Africa: home to some of the most destitute and ecologically challenged peoples on earth) is already showing steadily increasing rainfall AND increasing vegetation density, reversing the trend towards increasing aridity initiated by the period of declining global temperatures in the 50's 60's and 70's

This echos historical trends during what until recently were acknowleged to be "Climate Optimums" before we decided to see warming as a bad thing without regard to the clear historical evidence. In the past there were two significant periods where prevailing conditions changed so markedly that they actually altered civilization.

The Holocene Climate Optimum, around 7,000 years ago, refers to a world that saw warmer, wetter conditions throughout many parts of the world. While we don't have the ability to determine a global average temperature which is meaningful in relation to our current measurement points (many of which show current cooling trends), many sets of climate proxy datasets agree that the warmer wetter conditions were very widespread. The Sahara was a fertile land of lakes, grassland, and forests, and humans flourished. When the Earth cooled, the land dried, and the desert covered numberless archaeological sites which are regularly discovered, adding to a steady font of knowledge about this hidden history of mankind.

The Medieval Climate Optimum was neither as warm nor as wet as the Holocene Optimum, though in many places it was warmer than today as evidenced by agriculture being practiced in Greenland. During this period the Anasazi in the American Southwest developed thriving communities that collapsed as a result of the arridity that followed the temperatures down during the Little Ice Age. This era was also marked by high water levels in lakes in Australia and Asia, as well as many shallow lakes in the interior of the Arabian Peninsula that vanished when the earth cooled. But not forever, they are now, according to recent news reports, starting to reappear.

Links:

Africa: The longterm Paleoclimatological Record: Cool = Dry:
http://www.esd.ornl.gov/projects/qen/nercAFRICA.html

Pueblo Indians driven from their homes by Little Ice Age:
http://www.indiana.edu/~arch/saa/matrix/naa/naa_web/mod15D.html

Africa Now: The future appears damp:
http://www.nytimes.com/2007/02/11/world/africa/11niger.html?ex=1328850000&en=6f7869852a389205&ei=5088&partner=rssnyt&emc=rss
http://www.agu.org/pubs/crossref/2005/2005GL023232.shtml
http://www.guardian.co.uk/climatechange/story/0,12374,1571446,00.html
http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=2366&language=1

Arabia: Hello lakes, welcome back!
http://archive.gulfnews.com/articles/05/03/14/156080.html

And a balanced view (how rare)
http://press.princeton.edu/chapters/s6916.html