Recently hearing Fred Singer from the USA lecture on what he perceives to be the uncritical ways in which global change has been attributed to anthropogenic effects reminded me of the importance we should attach to those who question our current beliefs. For Fred it was not sufficient that the IPCC had engaged many of the best scientific brains in the world to reach the existing consensus; they might all be wrong because the original question or assumption was wrong. Fred was strongly challenged by the audience of Antarctic scientists, not least because some of his quotations were selective in order to initiate discussion. And we know that there are areas of considerable weakness amongst the several proxies used to compute the rate of temperature change, that we have only poorly quantified and modelled the role of clouds, energy transfer between the oceans and atmosphere, water vapour as a greenhouse gas and that we have yet to be certain that the Global Climate Models really do have all the most significant driving variables. So the IPCC conclusions are drawn on the best available evidence with complementary patterns derived from several different approaches and constitute the best we can do at the moment.