One of the key statements from the 2007 IPCC report, is that warming of the climate is unequivocal. The evidence comes from air temperatures, from ocean temperatures, from reductions in the amounts of ice and snow on the surface of the planet, and from changes in sea level because additional water is being stored in the oceans and because the oceans are being warmed. Although there is a great deal of natural internal variability in the system, we have strong evidence that human activity has been driving these temperatures upwards over the past 100 years.