The context

Whatever one's views, it cannot be doubted that there is a pressing need to respond to the social, economic and intellectual challenges of global environmental change. Much of the debate on these issues has been crystallised around the activities of the IPCC (Intergovernmental Panel on Climate Change). The IPCC process was set up in 1988, a joint initiative between the World Meteorological Organization and the United Nations Environment Programme. The IPCC's First Assessment Report was published in 1990 and thereafter, the Second (1996), the Third (2001) and the Fourth Assessment Report (2007) have appeared at regular intervals. Each succeeding assessment has become more confident in its conclusions.

The conclusions of the Fourth Assessment can be summarised as follows:

1. (a) warming of the climate system is unequivocal;

2. (b) the globally averaged net effect of human activities since AD 1750 has been one of warming (with high level of confidence);

3. (c) palaeoclimate information supports the interpretation that the warmth of the last half century is unusual in at least the previous 1300 years;

4. (d) most of the observed increase in globally averaged temperature since the mid twentieth century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations; and

5. (e) continued greenhouse gas emissions at or above current rates will cause further warming and induce many changes in the global climate system during the twenty-first century that would very likely be larger than those observed in the twentieth century. Details of the methodology used to reach these conclusions can be found in Appendix 1.1.

The IPCC assessments have been complemented by a number of comparable large-scale exercises, such as the UNEP GEO-4 Assessment (Appendix 1.2) and the Millennium Ecosystem Assessment (Appendix 1.3) and, for example, at a more focussed level, the Land Use and Land Cover Change (LUCC) Project (Appendix 1.4) and the World Heritage List (Appendix 1.5).