This seminar addresses what policy targets should be set to avoid severe impacts to the Great Barrier Reef (GBR) from climate change. The evidence of climate change and current knowledge of likely impacts to the GBR are reviewed, particularly the major coral bleaching events in 1998 and 2002. Three key conclusions are drawn. First, setting policy targets of stabilising atmospheric greenhouse gases and aerosols at 450–550 ppm carbon dioxide equivalents to limit increases in mean global temperatures to 2–3°C over pre-industrial levels are likely to be too high to avoid severe impacts of coral bleaching to the GBR. Second, stabilising greenhouse gases and aerosols around year 2000 levels, of 370 ppm carbon dioxide equivalents, and allowing a rise in mean global temperature of 1°C, appear to be the highest targets that should be set if the GBR is to be protected from serious degradation. Third, current policies are far from achieving or even setting these objectives and, consequently, severe impacts to the GBR are likely in coming decades. This seminar is of particular importance in the context of the current national political debate on emissions trading and emissions reduction targets.