In a paper with the deliberately boring title “A Provisional Long Mean Air Temperature Series for Armagh Observatory” C.J. Butler and D.J. Johnston find a near perfect correlation between solar cycle length and temperature from 1796 to 1992 – which implies that recent warming is real, but wholly explained by events happening on the sun.
The paper starts off with lots of worthy, important, and extremely boring stuff about thermometers. The meat of the paper is at the end, in figures four and five. Skip right ahead to figures four and five. For a more polemical account, see David Archibald
An interesting extension then is to apply this result to recent times, to predict the temperature trend over the next decade or so and interpret the global temperature observed since 2002 by the Aqua satellite, which we will be able to do as soon as it becomes apparent that solar cycle twenty three has ended. Of course we will not know that solar cycle twenty three has ended until many months after it has ended, and no one knows when it will end. If, as seems likely, solar cycle twenty four starts in May 2008, or even later, then the period 2010-2025 is going to be pretty damned cold.