In the past few centuries atmospheric carbon dioxide (CO2) has increased by more than 30% as a consequence of human activities, resulting in higher temperatures. The most advanced climate models are driven by a range of plausible assumptions for future emissions of all types (natural and anthropogenic drivers), and make it clear that the overall effect of human activity on the atmosphere is almost certainly a net positive forcing — anthropogenic warming. Now climate change is widely considered to be one of the most potentially serious environmental problems ever confronting the global community.