1 Beyond reasonable doubt

T he Internet is a wonderful research tool. With the click of a mouse, you can beam yourself into what seems an infinite number of important lectures by eminent thinkers around the world. Just such an opportunity awaits if you search for Richard A. Muller, professor of physics at the University of California, berkeley. The results of such a search include a video of Professor Muller castigating the scientists at the centre of the 2009 Climategate scandal. 'Climategate' is the name given by sections of the American media to the 2009 imbroglio surrounding leaked emails from the Hadley Centre in the United Kingdom. The emails were used to suggest that some scientists had been selective in their use of data to support the idea of global warming. In the video, Professor Muller berates the Hadley Centre scientists for smoothing data to produce alarming graphs that would make global warming 'incontrovertible' to the public. Professor Muller concludes by announcing his own major study into the measurement of global warming, the berkeley Earth Project, without 'the bias', he says in the video. Some months later, in March 2011, Professor Muller appeared before a US congressional committee at the invitation of Republican members opposing action on climate change. He was there to present the preliminary results of his bias-free project. To his surprise, he said, and certainly to the surprise of his hosts, the results of the project tallied very closely with those of the Hadley Centre's temperature measurements, as well as those of the US National Aeronautics and Space Administration and the National Oceanic and Atmospheric Administration. The fact is, that despite human imperfection, modern science on climate change has held up well under withering scrutiny. The vast majority of those who have spent their professional lives seeking to understand climate and the impacts of human activity on it have no doubt that average temperatures on earth are rising and that human-induced increases in greenhouse gases are making major contributions to these rises. They are supported in this by the learned academies of science in all of the countries of scientific accomplishment. Where dissent is found in the community of scientists with genuine climate credentials, it is among a small number who argue that the effects of increases in greenhouse gases are small compared with other sources of changes in temperature.