This paper discusses the nature of dangerous climate change, the problems of coordinating international action in response to it, and the importance of researching methods to supplement mitigation, at least temporarily. I defend the antipoverty principle for purposes of identifying dangerous climate change and guiding climate change mitigation policy. I then distinguish that identificatory account of dangerous climate change from the stated aim of international negotiations, namely to avoid global mean temperature warming in excess of 2ºC. I argue that climate change in excess of 2ºC is not necessarily dangerous climate change. The subsequent section discusses the nature of the collective action problem that bedevils mitigation negotiations; I also evaluate the pledge and review policy approach in light of its capacity to solve the collective action problems of mitigation. Although the pledge and review mechanism possesses the virtues of making a broad agreement possible and of protecting poor states against diplomatic duress, it is unlikely to provide a robust resolution of the collective action problems that results in climate change.

But there is no rival approach that seems likely to produce better results. Far from ideal, the pledge and review process is plausibly be the best one given the collective action problems. I also argue that limiting warming to 2ºC is unlikely. The risks of climate change are likely to be considerable; and the uncertainty of catastrophic events are worrying. So, I argue that uncertainty in light of several kinds of abrupt climate perturbations discussed in the AR5, the most recent report of the Intergovernmental Panel on Climate Change (IPCC), merits precautionary supplements to mitigation efforts. I close by endorsing the merits of research into carbon capture and storage and solar radiation management by means of sulfur injections into the stratosphere. If dangerous climate change is to be avoided, considerable supplementing of mitigation may be required.