National Geographic is doing a special on Feb 10 called "Six Degrees" that explores, from 1 degree Celsius to 6 degrees Celsius warming, what the impact on the world would be. They have short video exerpts on-line for impact of each degree (1, 2, etc.). Well worth watching.
Most interesting to me was a comment that James Hanson made (one of THE world premier climate modellers, head of Goddard Institute).
If the world warms up 1 degree Celsius from where we are today, earth will be hotter than it has been in last 1 million years. Temperatures from 1 million years ago are known based on studies of Antartic ice cores and of ocean beds. One way to look at it is, there were no human beings 1 million years ago, so we've never tried to live in that type of climate.
I actually stated out life as a history major (had to switch to computers though to make a living!). I've always been interested in "Deep History", how humans originated in Africa, then some migrated out between 60-80,000 years ago to populate the world. One thing I learned is that climate has had a dramatic impact on where people went, when they went there, and if they were able to stay. As Ice Ages came and went, as deserts bloomed and faded back to dry, people settled in various areas and then were forced out again due to climate changes, etc., over span of last 100,000 years.
Another way to look at it is, the climate we have had for last 11,000 years is about as good as it gets on earth, at least for humans. We're in an inter-glacial period (in terms of long-scale history), with fairly regular, predictable (within ranges) climate and weather patterns. The Human population has exploded during this wonderful period.
Even without human interference, earth's climate will have changes in future (Ice Ages are caused by shape of earth's rotation around the sun, as it goes from rounder to more elliptical every 100,000 years and by changes in earth's tilt toward sun every 25,000 years). But these natural changes would tend toward cooler, not hotter. If humans influence (maybe I should say mess up!) Mother Nature's delicate balances, it could have unpredictable consequences for Earth and life on earth.
Second link I posted below (Bradshaw Foundation, Journey of Mankind) has a good overview of the history of human migrations that populated the world, what the climate conditions were at the time of each migration, and the impact of these global climate conditions on migration process.
http://channel.nationalgeographic.co...el/sixdegrees/http://www.bradshawfoundation.com/stephenoppenheimer/
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