Michael Oppenheimer was the Lead Author on the Third and Fourth Assessment reports of the Intergovernmental Panel on Climate Change (IPCC). His scientific understanding of global warming provides a framework for developing response policies at the local, national and international levels. Oppenheimer reviews this evidence in order to present a framework for policies to mitigate emissions and adapt to some level of inevitable warming. He also discuss changes in the relations among nations in the climate arena which were evident at Copenhagen and recent developments related to the public communication of the science of climate change. A Sydney Ideas event on 23 Feb, 2010 : http://sydney.edu.au/sydney_ideas/lectures/2010/professor_michael_oppenheimer.shtml