The 800-Year Lag
One of the most serious flaws in the case for anthropogenic climate change is demonstrated in the graph that the AGW lobby uses to make its case:
This graph they tell us, shows clearly how temperature has tracked CO2 for the last few hundred millenia. It certainly looks like it. The apparent close fit is certainly sufficient to make people feel that there has to be a connection and to forget that correlation does not imply causation. This graph is almost always portrayed, as it is above, on a scale in which the thickness of the line itself is equivalent to a few thousand years. This is done to conceal the fact that the AGW lobby does not tell us at the same time, which is that the CO2 change lags behind temperature change by approximately 800 years. If this graph shows us anything, it is that temperature increase causes CO2 increase.
When the AGW lobby was confronted with this "problem" that it had attempted to conceal behind the thickness of the graph line, the response is typified by that of the pro-AGW web site realclimate.org:
"All that the lag shows is that CO2 did not cause the first 800 years of warming, out of the 5000 year trend. The other 4200 years of warming could in fact have been caused by CO2..."
Note the complete failure to assert what did cause this first period of warming. The AGW lobby wants us to believe that a mysterious, un-named, unidentified "something else" caused the first 800 years of warming but suddenly stopped and gave way to CO2, which then mysteriously took over for 4200 years. And then suddenly stopped. And it wants us to believe this in the face of mechanisms which can account for the entire warming/cooling cycles.
Note also the weakness of "could in fact have been caused by CO2" (let us exlude the "in fact" -- there are no facts here, only the sort of speculation that is usually reserved for the purveyors of pseudoscientific crackpotism). We are being asked to change our way of life and, more importantly, to keep the underdeveloped world in a state of underdevelopment, on something that could have been caused by CO2. That is about as logical as saying that it could have been caused by a mysterious and undiscovered species of pink Welsh dragons that, equally mysteriously, disappear without trace after warming the atmosphere with their breath for 5 millenia at a time. This is not science; it is pseudoscience of the worst kind.
An even worse argument to account for this lag is the The Earth was warming because it was coming out of an Ice Age" one. This is tantamount to saying that the Earth was warming because it was warming; i.e. it is tautology, not an explanation. Well, yes, the Earth goes through periods of warming and periods of cooling. That is the whole point!