Here is a recent post from Lubos on correlation, causation and the actual relationship between carbon dioxide and temperature in the historical record. And here is a similar discussion by Tim Patterson that reaches this conclusion:
- ...the geologic record clearly shows us that there really is little correlation between CO2 levels and temperature. Although CO2 can have a minor influence on global temperature the effect is minimal and short lived as this cycle sits on top of the much larger water cycle, which is what truly controls global temperatures. The water cycle is in turn primarily influenced by natural celestial cycles and trends.
It occurs to me that placing these facts before you is neither heresy nor denial, but a simple exposition of observed data with the obvious corollary: how can anyone view these facts and still seek to infer a cause and effect relationship without also positing the possibility that an alternative explanation may be self-evident. At what point do you cease to explain away the data that don't fit your hypothesis and just abandon it in favour of a different, more robust explanation?
As this post illustrates, the point of abandonment may occur when advocacy is over-extended and alienates those objective scientists who seek to support the AGW hypothesis but not at the expense of their intellectual integrity.