Deniers have known all along that they were lying.
Even industry scientists concluded that:
The scientific basis for the Greenhouse Effect and the potential impact of human emissions of greenhouse gases such as CO2 on climate is well established and cannot be denied… The contrarian theories raise interesting questions about our total understanding of climate processes, but they do not offer convincing arguments against the conventional model of greenhouse gas emission-induced climate change.
And that was from a memo written in 1995!
Of course that isn’t what the industry funded Global Climate Coalition, who’s scientists wrote the above memo, was saying:
“The role of greenhouse gases in climate change is not well understood,” the coalition said in a scientific “backgrounder” provided to lawmakers and journalists through the early 1990s, adding that “scientists differ” on the issue.
Of course none of this should be surprising, in fact the 1995 memo also debunks several denier talking points that are still used to this day, proving once again that deniers simply don’t care if their arguments are debunked.
Jastrow’s hypothesis about the role of solar variability and Michaels’ questions about the temperature record are not convincing arguments against any conclusion that we are currently experiencing warming as the result of greenhouse gas emissions. However, neither solar variability nor anomalies in the temperature record offer a mechanism for off-setting the much larger rise in temperature which might occur if the atmospheric concentration of greenhouse gases were to double or quadruple.
Lindzen’s hypothesis that any warming would create more rain which would cool and dry the upper troposphere did offer a mechanism for balancing the effect of increased greenhouse gases. However, the data supporting this hypothesis is weak, and even Lindzen has stopped presenting it as an alternative to the conventional model of climate change.
Remember, that was from industry scientists in 1995. Since then the conclusions from climatologists have only gotten stronger and more confident.
Michael Tobis sums it up nicely:
I think, that the failure of civil society to reject this cynical manipulation of factual information may turn out to be the single most salient historical fact of our time.
Cartoon by Marc Roberts.