There is much less scepticism today about greenhouse gas-induced climate change and what its consequences might be, even though the full impacts of climate change cannot yet be predicted with certainty. On the other hand, the nature of weather variability – particularly in the northern hemisphere in recent years – has left some again questioning whether our climate really is warming. But the evidence is there for all to see, even as the sceptics refuse to accept the empirical data of increases in atmospheric CO2, for example, or the unprecedented summer melting of sea ice in the Arctic and the retreat of glaciers in the Alps.