Creationists and climate change deniers have this in common: they don't answer their critics. They make what they say are definitive refutations of the science. When these refutations are shown to be nonsense, they do not seek to defend them. They simply switch to another line of attack. They never retract, never apologise, never explain, just raise the volume, keep moving and hope that people won't notice the trail of broken claims in their wake.

This means that trying to debate with them is a frustrating and often futile exercise. It takes 30 seconds to make a misleading scientific statement and 30 minutes to refute it. By machine-gunning their opponents with falsehoods, the deniers put scientists in an impossible position: either you seek to answer their claims, which can't be done in the time available, or you let them pass, in which case the points appear to stand. Many an eminent scientist has come unstuck in these situations. This is why science is conducted in writing, where claims can be tested and sources checked.

- George Monbiot

http://www.guardian.co.uk/commentisfree/cif-green/2009/sep/14/climate-change-denial