Here is an excerpt from the ongoing debate on MSNBC's discussion board "climate change".
Message #806/07/07 01:42 PM
Head: the facts and evidence against CO2 being the main driver of climate are not "mine," but the findings of hundreds of peer-reviewed studies by scientists with the credentials to support their position. I'm quite certain that they are up to your "challenge."
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The red curve illustrates the solar activity, which is generally increasing through over the past 100 years. At the same time, the Earth's average temperature as indicated by the black curve has increased by approximately 0.7C. (Reference: Friis-Christensen, E., and K. Lassen, Length of the solar cycle: An indicator of solar activity closely associated with climate, Science, 254, 698-700, 1991).
Matt: while we have only been directly observing changes in solar output for a few decades, there are thousands of years of historical records as well as geological proxies. Studies indicate that the sun has been hotter for the past 30 years than any time in the previous 10,000.
Sky: neither changes in solar brightness or CO2 can account for all of observed warming. This is why climate models use a positive feedback multiplier (an assumption that has never been identified) to achieve results consistent with observations. The Svensmark research has identified a mechanism for a positive solar feedback (greater solar output = fewer cooling clouds = additional warming), which will effectively shift some of this positive multiplier from CO2-based to solar-based. The more warming that is attributed to changes in TSI, the less that can be attributed to CO2.
The link between cloud cover changes and temperature is well documented.
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