Introduction

Policy decisions in many areas involving science, including the environment and public health, are both complex and contested. Typically there are no facts that entail a unique correct policy. Furthermore, political decisions on these problems will need to be made before conclusive scientific evidence is available. Decision stakes are high: The impacts of wrong decisions based on the available limited knowledge can be huge. Actors disagree on the values that should guide the decision-making. The available knowledge bases are typically characterised by imperfect understanding (and imperfect reduction into models) of the complex systems involved. Models, scenarios and assumptions dominate assessment of these problems, and many (hidden) value loadings reside in problem frames, indicators chosen and assumptions made.

The evidence that is embodied in scientific policy advice under such post-normal (Funtowicz and Ravetz 1993) conditions requires quality assessment. Advice should be relevant to the policy issue, scientifically tenable and robust under societal scrutiny. Governmental and intergovernmental agencies that inform policy and the public about complex risks increasingly recognise that uncertainty and disagreement can no longer be suppressed or denied, but need to be dealt with in a transparent and effective manner. In response to emerging needs, several institutions that interface science and policy have adopted knowledge quality assessment approaches, where knowledge refers to any information that is accepted into a debate (UK Strategy Unit 2002; EPA 2003; MNP/UU 2003; IPCC 2005).

Climate change: between democracy and expertise?

Climate change represents one of society's most challenging environmental concerns and has been a major factor in changes in the way that environmental policies are debated and informed. Climate change policy faces at least three major challenges: (1) what is known – or not known – about climate change, in particular regarding the relative importance of anthropogenic factors; (2) what can and should be done; and (3) who should do something about it?

Since the 1992 Rio Earth Summit, these challenges have been addressed in several ways: (a) by increasing research and international sharing and integration of expertise on climate change (e.g., the Intergovernmental Panel on Climate Change); (b) by developing international agreements on issues such as the reduction of carbon dioxide emissions; and (c) by promoting national/local strategies to fulfil international agreements (e.g., Local Agenda 21 – community defined strategies for sustainable development arising from the first “Earth Summit” held in Rio in 1992). These challenges all include policy and scientific aspects but also raise questions over the interpretation of Local Agenda 21 (Tuxworth 1996; Selman and Parker 1997; Voisey et al. 1996; Young 1996; Young 1997). How local is “local”? What kind of “agenda” is “Agenda 21”? Whose “agenda” is it? Answers to these questions vary according to the perspectives and purposes of those asking the questions in the first place.