According to most climate experts, anthropogenic greenhouse gases add about 2 watts per square-meter of radiative forcing to earth’s environment. This is roughly the power used by a small Christmas tree lamp. In more personal terms, the human body generates approximately 100 watts of power and has a surface area of around 2 square-meters. Assuming that the sole of the average foot has an area of about 200 square-centimeters, it would emit 1 watt of power. Both feet, applied to a surface, would add 2 watts to that surface. Applied to a square-meter, that would be equivalent to the anthropogenic greenhouse effect.
If we could cover every square meter of the Greenland ice cap with a barefoot human — a magical, never frostbitten human willing to stand, day after day, pumping his 2 watts into the ice — would we expect the ice to melt?
The answer is “eventually.” A back-of-the-envelope calculation* suggests that it would take about 10,000 years, assuming an average ice depth of 2 kilometers. In light of this, Al Gore’s threat to invoke the wrath of Gaia to bring about a complete meltdown in 60 years seems off by a couple of orders of magnitude — unless, of course, he is willing to acknowledge the possibility that the warming we observe is due to a so-far unmeasurable anthropogenic effect superimposed on a poorly understood natural warming process that began when Abraham Lincoln was a baby, long before carbon dioxide levels changed.
Such an admission, however, might be inconvenient.
*2 Watts = 172800 Joules/day
333700 Joules melts 1 kg of ice
Therefore 2 watts melts 172800/333700=0.52 kg/day
1 kg = 1000 cubic centimeters of ice (yes, I know its really a bit more because of expansion)
Distributed over 1 square meter, this equals a depth of 0.1 cm
But our feet can melt only 0.52 kg/day, so a hotfooted human would melt a depth of (0.52)X 0.1 cm / day = 0.05 cm/day (half a millimeter)
THUS, the heat from a person’s feet would melt (distributed over a square meter), a depth of:
1 meter/2000 days (call it 5 years)
2000 meters in 10,000 years (This surprised even me, so I’d appreciate a check of this reasoning by more arithmetically adept readers).
NB: Junk Science has a detailed discussion of how to evaluate anthropogenic radiative forcing .