Observations of increases in global average temperatures, widespread melting of snow and ice, and a rising global average sea level indicate that the climate is already warming (IPCC, 2007a). If greenhouse gas (GHG) emissions continue to grow, this could result in a wide range of adverse impacts and potentially trigger large-scale, irreversible and catastrophic changes (IPCC, 2007b) that will exceed the adaptive capacity of natural and social systems. The environmental, social and economic costs of inaction are likely to be significant.