I've had a new insight about atmospheric carbon dioxide. It's not something you'll see published elsewhere, because it's nuanced, and public discussions of global warming don't tolerate nuance. Anyway: the great weakness in atmospheric simulations is that they have no way at all to model cloud cover. Nobody knows what the effect of anything will be on cloud cover, despite that cloud cover affects absolutely everything climatic. (Some people have pretty good evidence that cloud cover is affected by solar activity and even by cosmic ray flux.) This means that even the very best models can't really tell us anything about the climatic effects of CO2 under conditions where cloud cover is changing, despite that a different climate will certainly have different cloud cover.
Why, then, should we worry about CO2? First, it clearly has been a primary influence on runaway global warming so far, and that ought to be enough to freak out anybody. (Cloud cover shows no sign of jumping up to save us yet!) But even if cloud cover were to jump and save us (and, who knows, plunge us into an ice age?), CO2 is certainly a direct cause of coral bleaching (via dissolution in the ocean, forming carbonic acid) and the crash of reef ecologies, the basis of the ocean ecosystem. We take millions of tons of food from the ocean ecosystem every year. Any sane person should find that enough reason, alone, to move heaven and earth to cut CO2 releases. Uncertainty over the effect of CO2 on the climate only redoubles the urgency.