Following on from the pondering by Gordon Robertson on extra heat generated by the earth and how this might be accounted for in global warming theory, Mark Duffett has kindly sent in a note with some links:
For all of you out there who might actually be interested in learning something, this isn’t a bad introduction:
There is a flaw in the assumptions behind the statement contained therein about the practicality of geothermal energy extraction, but ignore that for the moment.
The bottom line here is the figure of 0.075-0.087 W/m2 for globally averaged heat flow (i.e. the flux of internally generated heat at Earth’s surface). Note this is fundamentally based on upwards of 20,000 direct measurements. For comparison, the flux of solar energy incident on Earth at the top of the atmosphere is ~1360 W/m2.
You can draw your own conclusions about the likely direct influence of Earth’s internal heat on climate.
http://www.agu.org/pubs/crossref/1993/93RG01249.shtml is recommended for a more in-depth treatment.