A bit out of date, but not many have posted on it, so I will mention Steven Stoll's article The Cold We Caused in the November 2009 Harpers Magazine.  Stoll's article makes the case that the Little Ice Age was caused by the world-wide death of millions of people due to the Black Death.  It is worth reading, but isn't available on-line except behind Harper's pay wall.  However, The Disaffected Lib has excerpts of it.

The key point of the article is to demonstrate that humans have long affected our world's climate and continue to do so with all of CO₂ we are pumping into the atmosphere and oceans.  Those who continue to deny that basic fact do so at our collective peril as was pointed out by Peter Watts in his blog post, Because We All Know, The Green Party Runs The World, on the CRU Email break in:

"I went running through Toronto the other day on a 17°C November
afternoon. Canada’s west coast is currently underwater. Sea level
continues its 3mm/yr creep up the coasts of the world, the western
Siberian permafrost turns to slush. Swathes of California and Australia
are pretty much permanent firestorm zones these days. The glaciers
retreat, the Arctic ice cap shrinks, a myriad migratory species still
show up at their northern destinations weeks before they’re supposed
to. The pine beetle furthers its westward invasion, leaving dead
forests in its wake— the winters, you see, are no longer cold enough to
hit that lethal reset button that once kept their numbers in check."