One way to find evidence concerning whether a politicized theory is being exaggerated or being stated overconfidently is to look at how experts from a very different worldview thought about the theory. I had been under the impression that theories about global warming were recent enough that it was hard to find people who studied it without being subject to biases connected with recent fads in environmental politics.
I now see that Arrhenius predicted in 1896 that human activity would cause global warming, and estimated a sensitivity of world temperature to CO2 levels that differ from current estimates by about a factor of 2. The uncertainty in current estimates is large enough that they disagree with Arrhenius by a surprisingly small amount. This increases my confidence in that part of global warming theory.
Arrhenius disagreed with modern theorists about how fast CO2 level would rise (he thought it would take 3000 years to rise 50% or to double, depending on whether you believe Nature or Wikipedia), and about whether warming is good. That slightly weakens my confidence in forecasts of CO2 levels and of harm from warming (although as a Swede Arrhenius might have overweighted the benefits of warming in arctic regions).