At the initiative of the Royal Society, a group of sixteen national academies of science from all parts of the world has agreed a statement about the science of climate change. The statement endorses the Intergovernmental Panel on Climate Change as the most reliable source of information on climate change and its causes. It calls for prompt action to be taken to reduce emissions of greenhouse gases and recognises the ratification of the Kyoto Protocol as a small but essential first step towards stabilising atmospheric concentrations of greenhouse gases. The statement was printed in Science on 18 May 2001.