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.