Continuing emissions of greenhouse gases from human activities are predicted by the Intergovernmental Panel on Climate Change (IPCC) to lead to significant changes in global climate over the next century. The New Zealand Climate Committee of the Royal Society o f New Zealand prepared a report prior t o the IPCC Scientific Assessment, and its findings were generally consistent with those of the IPCC. Some of the conclusions reached in these 'scientific consensus' documents have been debated in scientific journals and articles in the popular media. However most of the critical questions commonly asked about climate-change science were examined as part of the IPCC scientific assessment. Important processes about which understanding is currently incomplete were identified, and the resulting uncertainty with regard to the timing, magnitude and regional patterns o f climate change discussed. I n this paper we summarise the findings of the IPCC scientific assessment, and discuss some of the issues which have been debated.