There is a growing consensus that climate change represents the world’s most pressing longterm threat to future prosperity and security. In his summary of the recent UN High Level Event on Climate Change, Secretary‐General Ban Ki‐moon noted that the gathering was an occasion to “express the political will of world leaders at the highest level to tackle the challenge of climate change through concerted action.” Meeting in Heiligendamm in June 2007, G‐8 leaders argued that climate change “has the potential to seriously damage our natural environment and the global economy.”
Informing these positions is the science on climate change, which grows ever more certain. The Inter‐governmental Panel on Climate Change, the world’s authoritative source of information on climate change, this year delivered its fourth assessment report, describing global warming as a “certainty,” and human causes of the problem as 90% certain. A changing climate will disrupt complex environmental, social and economic systems that have built up over centuries, and which cannot withstand rapid fundamental change.