The Intergovernmental Panel on Climate Change (IPCC) was set up by the United Nations in 1988 to provide assessments of the latest peer-reviewed climate science for policy-makers. The Working Group I (WGI) contribution to its Fifth Assessment Report (AR5), published last year, concluded that we can now be more confident than ever that the release of heat-trapping greenhouse gases from deforestation and the use of fossil fuels has caused much of the global warming and other changes in the climate witnessed in the latter half of the 20th Century and, if unabated, will continue to drive warming in the future.
AR5 provides the best available summary of the prevailing scientific opinion on climate change currently available to policy-makers. Its conclusions have been reached with high statistical confidence by a working group made up of many of the world's leading climate scientists drawing on areas of well-understood science. The overall thrust and conclusions of the report are widely supported in the scientific community and its summaries are presented in a way that is persuasive to the lay reader. As in all areas of science that involve highly complex dynamic systems, there are uncertainties. But these uncertainties do not blur the overwhelmingly clear picture of a climate system changing as a result of human influence.
The IPCC has responded extremely well to constructive criticism in the last few years and has tightened its review processes to make AR5 the most exhaustive and heavily scrutinised Assessment Report to-date. We believe that the IPCC would benefit from increasing the level of transparency by recruiting a small team of non-climate scientists to observe the review process from start to finish including during the plenary meetings to agree the Summary for Policymakers. However, the authority of the reports comes not from the process and procedure per se, but from the evidence itself: the thousands of peer-reviewed academic papers that together form a clear and unambiguous picture of a climate that is being dangerously destabilised.
Of course there are those who will continue to be critical of the conclusions and the process through which the IPCC produces its Assessment Reports. But our conclusion here is clear. There is no scientific basis for downgrading the UK's ambition to reduce greenhouse gas emissions. The Government and the international community must heed the IPCC's warning and work to agree a binding global deal in 2015 to limit climate change to manageable levels.