A variety of sources to help:
A starting debate from Free Market Net and The Independent Institute.
IPCC, the American EPA, New Scientist, Globalwarm and The Tiempo Climate Cyberlibrary are all extensive starting points.

You may wish to do your own environmental footprint, visit Winchester City Council, then the a-z for sustainability, then measuring your impact for a series of useful sites.

You may also wish to think about human health, agriculture and transportation. Remember green organisations such as Greenpeace and Friends of the Earth.

These may in fact steer you in one direction so please consider the following as well, prominent sceptics, from the BBC, American Scepticism a site with many links, Association of British Drivers, motorists again, Bush's original stance and an extensive list of links from both persuasions.