The Intergovernmental Panel on Climate Change (IPCC) has issued its fourth assessment report, Climate Change 2007 (The Fourth Assessment Reports may be accessed via the IPCC website: http://www.ipcc.ch/), with the report of Working Group III, (Mitigation of Climate Change), recently agreed in Bangkok, to go alongside those of WGI (The Physical Science Basis) and WGII (Impacts, Adaptation and Vulnerability) agreed earlier in Brussels. Since the IPCC presented its first assessment report in 1990, the public debate (put simply) has moved over time from ‘is the global climate warming?’ to ‘to what extent may man be responsible?’ to ‘can anything be done in time and, if so, what?’ My comments do not seek to rehearse the complex scientific, social, economic and political arguments but to focus on the role of science, scientists and the scientific process and its interaction with the wider public and polity. At the heart of the scientific process is the better, if incomplete, understanding of the natural world that results from observation, measurement and experiment, tested for its validity, consistency and relevance through the process of peer review, replicability and accurate prediction. In most fields of scientific enquiry, the scientific data and the conclusions derived from them are usually subject to the scrutiny of fellow scientists for some time, and subsequently refined, before the broad body of the lay public becomes aware of them (if they ever do). Even in cases of heated scientific controversy, this has remained the case, certainly for much of the ‘scientific’ era of the last 200 years or so. On the other hand, where there may be a wider or worrisome impact, real or suspected, on the public, such controversies become a matter of public debate. The public can then be presented with a range of interpretations of complex matters about which scientists disagree, or worse, with incomplete or questionable data that one side of an argument or another has chosen to put into the public domain to promote their point of view. In these cases, the debate may be given wide publicity even before complete and fully analysed results have been published and subjected to peer scrutiny. With ever wider access to information, instantly available, combined with freedom of information legislation, the availability of scientific results and the debate about their interpretation and significance can now occur almost simultaneously, involving not only the scientific protagonists but others, often not scientifically expert, with particular interest in the matter under consideration. In such cases, the role of the media and the part played by scientists in their interaction with the media, become all important. I observed close up an earlier controversy, namely, that related to the depletion of stratospheric ozone caused by the emission of certain chlorineand bromine-containing products used in aerosol propellants, refrigerants, firefighting chemicals, cleaning solvents and fumigants. Once definitive scientific evidence became available and the Montreal Protocol entered into force the materials held to be responsible were phased out and, in some cases, alternatives phased in. The technologies for production of the key materials were operated by a relatively small number of international chemical companies so the process for their replacement, whilst a chemical and engineering challenge of some magnitude, took place with relatively little N. Winterton (&) Department of Chemistry, University of Liverpool, L69 7ZD Liverpool, UK e-mail: n.winterton@liverpool.ac.uk