“The Logarithmic Effect of Carbon Dioxide“. Geologist (and amateur climate and cancer researcher) David Archibald tries to show that CO₂‘s greenhouse effect impact is negligible at current levels and that rising levels will have even less impact. The only supporting references he mentions are an old blog post on the paragon of atmospheric physics, Climate Audit.

In fact, David’s ill-conceived idea was shot down all the way back in 2007. His conclusion is a product of deliberately selecting a very low climate sensitivity value for CO₂. Low sensitivity means low amplification. Kind of obvious if you think about it for a minute, but David clearly prefers to pick his question based on the answer he wants.

I have to mention his strange claim that ‘conventional climatology’ denies a logarithmic relationship to CO₂ forcing. This is contradicted by Arrhenius’ work in 1896 and the climate physics actually described in every IPCC Report to date. Even some of the denialist regulars are distancing themselves in the post comments, saying that while they resist the IPCC’s estimate of CO₂ forcing as too aggressive they accept that there is some degree of forcing.