Don't miss this from Fred Pearce: "The Met Office admits that we still know far too little about how these natural cycles work, and how big they are...it now looks like natural cycles played a big role in the unexpectedly fast warming of the 1990s"

Has global warming ground to a halt? - environment - 09 January 2013 - New Scientist

Atmospheric warming has certainly slowed greatly in the past decade. The Met Office says this appears to be due to natural cycles that are counteracting the warming effect of greenhouse gases. After incorporating new analysis of natural cycles into its latest model of atmospheric and ocean circulation, it has concluded that we are in for a few more years of little change.
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There is a growing awareness among climate scientists of the importance of natural variability in predicting climate change, especially in the short term, where it can completely obscure the global warming signal. This realisation has been bubbling up for a while.
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[] Are these cycles just something scientists have invented to explain away the lack of recent warming?
No. The Met Office admits that we still know far too little about how these natural cycles work, and how big they are. And climate scientists are open to the charge that they ignored the potential impact of natural variability when it was accelerating global warming. According to Brian Hoskins of Imperial College London, it now looks like natural cycles played a big role in the unexpectedly fast warming of the 1990s.