Emissions of a broad range of greenhouse gases of varying lifetimes contribute to global climate change. Carbon dioxide displays exceptional persistence that renders its warming nearly irreversible for more than 1,000 y.

Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here we show that this acted to slow the rate of increase in global surface temperature over 2000

Last year, the Intergovernmental Panel on Climate Change (IPCC) was awarded the Nobel Peace Prize along with Albert Gore Jr., sending a strong message about the importance of the world's future climate. Indeed, for two decades, international scientists and policy-makers contributing to the IPCC process have provided assessments of climate change science, impacts and mitigation, addressing one of the most far-reaching and complex challenges that society has ever faced. Yet this is no time for IPCC to rest on its laurels.

In their policy forum ("The limits of consensus," 14 September 2007, P. 1505), M. Oppenheimer et al, make several misleading statements. They suggest that a premature drive for consensus led Working Group I to understate the risk of large future sea-level rise in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (WGI-AR4). (Letters)