This is a critical time on climate. Scientific conclusions that had seemed largely settled and backed by professional consensus are today challenged with increasing confidence. Three months after Copenhagen, the policy pathway is still hard to discern. Opinion polls show growing numbers of people think the globe is not warming, or not because of human action, or, variously, that not much can, need or should be done about it. Last week a House of Commons committee queried the state of climate science in the wake of the publication of emails to and from the University of East Anglia’s Climate Research Unit; this week a new UN review has been launched to assess the work of the Inter-govermental Panel on Climate Change.