In trying to avert dangerous climate change, governments are aiming for something extraordinary. They want to transform the global economy because of a hypothesis for which the evidence is mostly inaccessible to the layman. It is the biggest pre-emption in history, and it relies on collective trust in science. That is why recent controversies around misreported evidence and exclusion of dissent at the University of East Anglia and the UN intergovernmental panel on climate change are so important. The worst allegations relate to the suppression of information – deleting emails, ignoring inconvenient data – in order to make aspects of the case for climate change tidier. The cover-up is the most toxic part in any scandal. The broad outline of the scientific case is unchanged, but confidence in the processes that got there is badly shaken. This is a big problem for advocates of political action on climate change. The case has always rested on a balance of risk. Few hypotheses in a system as complex as Earth’s climate can be asserted with 100% certainty. Yet if there is sufficient evidence that human emissions are having disastrous effects, it is worth acting because the risk […]