The difference seems to be largely due to a divergence in the older, 19th century data. (skepticalscience.com)
Does that mean the global mean surface temperature trends over the 20th Century, or just that some 20th Century data is used? (realclimate.org)
Climate models and the latest IPCC data reveal four possible futures for global population, economy and environment at the end of this century (newscientist.com)