The Voodoo Logic
If there is one ultimate example of the failure of critical thinking in this issue it's the one concerning the Vostok ice core records and the supposed reverse causal relationship between temperature and rises in carbon dioxide. It has been surmised by some -- most famously Dr. Tim Ball as seen in Martin Durkin's documentary, The Great Global Warming Swindle -- the the Vostok ice core records show that it isn't C02 that causes warming, but it is in fact temperature rises that cause a rise in C02 concentrations.
The Vostok ice core record. Compiled over the last two decades by several research teams, it was used, more famously, as a centerpiece of Al Gore's slideshow presentation in An Inconvenient Truth.
The supposed problem is this. While the ice core records do show a very strong correlation between C02 and temperature, temperature rises before C02 concentrations rise, ahead by around 600-800 years. As Tim Ball asserts in Swindle:"...they say that if the C02 increases, then the temperature will go up. But the ice core record shows exactly the opposite...so the fundamental assumption of human caused climate change is shown to be wrong...". See also here.
Interestingly, the papers that documented the research on the Vostok record didn't come to the same conclusion, nor did the IPCC in its treatment of the issue in 2001.
But there is a more fundamental flaw to the conclusion that "human caused climate change is shown to be wrong". Logically, it's an invalid argument. How does one go from claiming a reverse relationship to claiming a contradictory one? Well, you can't, because reverse relationships aren't neccessarily contradictory.
For example, how is Ball's argument no different than saying that since there are times when you've seen fire causing heat to spread, heat must not be able to cause fire, or cause fire to spread. Another more devious (and definitely not as effective or clear) analogy is if someone were to say that since in fact we can say that the sunrise follows moon rise, moon rise cannot follow sunrise. Thus, even though it's probably true that C02 rises after temperature, that doesn't automatically refute the idea that C02 causes temperature to rise! In fact, both relationships can exist without creating a contradiction.
Yet, we have supposed scientists -- great heretics, they like to call themselves -- that can't even get their logic straight. I can see how someone not trained to think critically might fall into the trap. But Ball? No wonder he hasn't published anything serious for a long time. If you find more examples of this flawed and overly tired argument, please post!
And what exactly was going on in the ice core record? While it's not entirely clear, temperature rises during those periods were likely due to changed in the earth's orbit around the sun -- Milankovtich cycles -- that are surmised to play a role in the onset and end of glacial periods. C02 is also thought to have amplified the effects of these cycles -- effectively creating the kind of glacial and interglacial periods seen in the ice core records. A lay summary of the issue can be found on NewScientist.