He or she had remarked that if a cheap, prolific, new way of harnessing energy were to be developed and became popular, this might constitute a new additional factor in global warming -- because the released energy, of whatever form, would eventually become heat. http://disq.us/p/25zwiea
The figures do not bear that out. World total energy use, if emitted as heat (and it is, pretty well all) contributes a tiny fraction to global temperature rise and it is NOT cumulative. In other words the temperature increase from dissipated anthropogenic heat is proportional to that heat power. Whereas the rise due to CO2 greenhouse effect accumulates since it is proportional to CO2 levels.
Considered over a short period the direct effect of heat (from, say coal) will be larger than the greenhouse contribution. Over longer timescales the CO2 dominates.
We are in trouble with AGW because of CO2 levels that are the result of 100 years of emissions (though due to increasing emission rate over time it is the last 40 years that predominate)
In fact the time for CO2 to dominate over direct heating when burning fossil fuels is only 124 days, and CO2 stays in the atmosphere for 200 years +. We have an average time of 40 years (v ballpark) for CO2 in atmosphere so the fraction of warming due to direct heating is (v ballpark) less than 1%. As AGW from greenhouse effect continues that fraction goes down.