http://www.thenation.com/docprem.mhtml?i=20070514&s=cockburn
[WS:] Cockubrn is a crank, but his rants against left/liberal groupthink and bandwagon jumping may have a point from time to time despite a heavy dose of hot air. However, his argument against global warming looks like being mostly hot air.
This argument seems to rest on two claims or objections:
1. That the amount of CO2 emissions by humans and and the amount of CO2 is the atmosphere do not vary in the same way - the former goes up and down, while the latter grows steadily; and
2. That CO2 relesed from water due to natuaral variations in global temperature is far greater than the amount of CO2 released by human activity.
Both claims/objections seem easy to dismiss. IF the relationship between human produced emission and CO2 level in the atmosphere is cumulative i.e. CO2 already released stays there for a while, it is obvious that short term drops in human produced emissions (e.g. during the Great Depression, which Cockburn cites) will NOT be followed by drops in the CO2 level in the atmosphere. If there is any effect, it will be manifested by a slightly slower rate of accumulation rather than a drop.
As to the second objection (based on the mass of water on Earth and its CO2 emission), it does not apply if the relationship between emissions and warming is recursive and non-linear. Recursivity means basically a positive feedback, some CO2 emissions produce some warming which in turn intensifies future emissions, which produce more warming et. Non-linearity means that a samll change on the independent variable (emissions) may trigger a disproportionally large change on the depeneded variable (climate change). AFIK, climate models assume recursive and nonlinear relationships between human emissions and climate change, so Cockburn's argument is a nonsequitur.
Any thoughts from anyone who actually knows something on the subject?
Wojtek
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