Nasa study on Global Warming

[petek]

Originally Posted by KenWittlief

it really bothers me that the history of the temperature of the earth is based on several assumptions and many second order effects

True, but they're mainly based upon a well-tested, peer-reviewed and correllated proxy for temperature: the deuterium/oxygen isotopic ratio. First demonstrated by Willi Dansgaard in 1964, measurements of these trace gases trapped in ice core bubbles give a fairly accurate record of the temperature and atmospheric moisture content in the past. It may not be a direct measurement, but if it's good enough to be published in Science, Nature and a host of others, I figure it's good enough for me!