Fossil fuel burning may be causing the recent observed surface warming.
According to the IEA the "Total Primary Energy" consumption in the U.S. in 2002 was 97.7 quadrillion Btu. If you assumed this was all heat energy, you get:.
97.7 x 1015 Btu = 1.03 x 1020 joule in 2002
or on average 3.27 x 1012 Watts
The area of the U.S. is 9,640,000 km2 to this average energy works out to be about 0.34 W/m2.
For a doubling of carbon dioxide, the net increase in thermal radiation at the surface is 0.5 to 1.0 W/m2. For the increase from 290 to 370 ppm over the last century, the corresponding net increase in radiation is 0.18 to 0.35 W/m2. Thus on a regional basis, some locations have a warming from fossil fuel burning comparable to that postulated by greenhouse gas increases over the last century.
Related to this topic is the recent publication by de Laat et al. (2004):
de Laat, A. T. J., and A. N. Maurellis, 2004. Industrial CO2 emissions as a proxy for anthropogenic influence on lower tropospheric temperature trends, Geophys. Res. Lett., Vol. 31, L05204, doi:10.1029/2003GL019024, March 11, 2004, online <http://www.sron.nl/~josl/Documents/2003GL019024.pdf>
Surface temperature trends during the last two decades show a significant increase which appears to be anthropogenic in origin. We investigate global temperature changes using surface as well as satellite measurements and show that lower tropospheric temperature trends for the period 1979–2001 are spatially correlated to anthropogenic surface CO2 emissions, which we use as a measure of industrialization. Furthermore, temperature trends for the regions not spatially correlated with these CO2 emissions are considerably smaller or even negligible for some of the satellite data. We also show, using the same measure, that two important climate models do not reproduce the geographical climate response to all known forcings as found in the observed temperature trends. We speculate that the observed surface temperature changes might be a result of local surface heating processes and not related to radiative greenhouse gas forcing.
Vincent Gray comments as follows “the energy from combustion is emitted in a highly irregular fashion. Over the USA it is 0.31 W/m2, in California 0.81 W/m2, and in San Francisco 89.24 W/m2. New Zealand is 0.08 W/m2, Auckland 28.2 W/m2 and Essen (Germany) 221.65 W/m2. Weather stations in industrialized countries, particularly if close to cities, are therefore likely to record temperature increases from local energy production which could be much greater than predictions from the greenhouse effect. The effect could extend into the lower troposphere.”