According to The Economist:
The world is warming
ON NOVEMBER 29th representatives of countries from around the world gathered in Cancún, Mexico, for the first high-level climate talks since those in Copenhagen last December. Incremental progress is possible, but continued deadlock is likelier. What is out of reach, as it was at Copenhagen, is agreement on a plausible programme for keeping climate change in check. The world warmed by about 0.7°C in the 20th century and by the end of the 21st century temperatures will be 3°C warmer than at the beginning of the industrial revolution. Increases in average temperature will be less noticeable than those in extremes. According to a 2009 comparison of over 20 climate models by David Battisti and Rosamond Naylor, by 2050 there is a 10-50% likelihood that the average summer in much of the world will be hotter than any summer recorded until now. By 2090 the likelihood of this happening rises to 90% in many places. For more on climate change, see article.