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June 21, 2005
One point apparently causing confusion among our readers is the relative abundance of CO2 in the atmosphere today as compared with Earth's historical levels. Most people seem surprised when we say current levels are relatively low, at least from a long-term perspective - understandable considering the constant media/activist bleat about current levels being allegedly "catastrophically high." Even more express surprise that Earth is currently suffering one of its chilliest episodes in about six hundred million (600,000,000) years.
Given that the late Ordovician suffered an ice age (with associated mass extinction) while atmospheric CO2 levels were more than 4,000ppm higher than those of today (yes, that's a full order of magnitude higher), levels at which current 'guesstimations' of climate sensitivity to atmospheric CO2 suggest every last skerrick of ice should have been melted off the planet, we admit significant scepticism over simplistic claims of small increment in atmospheric CO2 equating to toasted planet. Granted, continental configuration now is nothing like it was then, Sol's irradiance differs, as do orbits, obliquity, etc., etc. but there is no obvious correlation between atmospheric CO2 and planetary temperature over the last 600 million years, so why would such relatively tiny amounts suddenly become a critical factor now?
Adjacent graphic 'Global Temperature and Atmospheric CO2 over Geologic Time' from Climate and the Carboniferous Period (Monte Hieb, with paleomaps by Christopher R. Scotese). Why not drop by and have a look around?
