The previous chapters have summarized present knowledge and uncertainty on the climate and how it is changing, the evidence for human causes of the observed changes, and the range of changes projected this century, as well as the less definitive current knowledge about potential climate change impacts and responses. This final chapter is more political, in a few senses. First, we examine the present politics of the issue, reviewing major actors' policies and positions. Second, we summarize and assess the main arguments being made against serious action to limit climate change. Finally, we present our own judgments of what kind of response to the climate issue appears appropriate in view of present scientific knowledge and political possibilities.

Climate-change politics: current policies and positions

Although climate change came onto policy agendas as early as 1990, little progress was made in policy debates in the 1990s and virtually none between 2001 and 2008, either in the United States or at the international level. During this period, the European Union and a few of its leading member states, as well as a few North American States and Provinces, took significant initial steps, but even these fell far short of what is needed to start the required energy-sector transformation. Other jurisdictions took only symbolic and small actions vastly too weak for the job, or none at all.