What is the impact of human activity on Earth's temperature?

[wolram]

Has there ever been an estimate for total human caused heat output?

If all humans and human activity were removed from Earth would the temperature fall?

 

[matthyaouw]

I can't remember where, but I have read the calculations and the figure was pretty insignificant compared to sources like Earth's heatflow from the crust.

 

[vanesch]

Indeed, it is insignificant. The solar input is about 10 000 times bigger than all human energy consumption. It is because greenhouse gasses are supposed to change *a tiny bit* the balance of that solar flux that global warming is possible.

 

[Andre]

However, it has been measured:

http://www.knmi.nl/~laatdej/2006joc1292.pdf

...These findings suggest that over the last two decades non-GHG anthropogenic processes have also contributed significantly to surface temperature changes. ...

 

[vanesch]

However, it has been measured:

http://www.knmi.nl/~laatdej/2006joc1292.pdf

Ah, yes, but these are still effects working upon the solar radiation balance (albedo and all that). I thought the OP asked about direct heating by humans (is your stove heating the earth?).

 

[wolram]

However, it has been measured:

http://www.knmi.nl/~laatdej/2006joc1292.pdf

Heat islands and change of land usage, yes i can understand they are warmers, and even that city warming can be reduced by careful management, surface pigments and plants, but surly even these warmers can change day to day dependent on wind for example.

 

[DEMcMillan]

You asked about more direct human warming. The EIA of DOE has been charged with estimating human energy production changes over time. I used their table to begin a direct assessment in quadrillion Btu’s www.eia.doe.gov/emeu/aer/txt/stb1101.xls. for the seven categories listed. The figure obtained for the rise from 1978 to 2004 was 166.7 quadrillion BTU’s or .127 W/m2. The MSU UAH observed rise in temperature for the period was .310oC. The increased outward radiation the rise generates is 1.012 W/m2 before losses. The original EIA figures were then adjusted for inefficiency of production, human and livestock body heat, use of other cooking fuels, wildfires, tobacco usage, agricultural burning, and several other identifiable human-related heat sources. This raised overall heat production to .177 W/m2. This figure is clearly still less than a fifth of the loss. A radiation balance disparity is still needed but direct increases in human heat energy production should not be neglected. This energy is also heavily consumed in cities of the Northern hemisphere where the warming has developed.

 

[vanesch]

This raised overall heat production to .177 W/m2.

That number must be about correct: 1/10000 of the sun input (~1300W/m^2 perpendicular).
Earth receives ~ 180 PW sun power, and consumes (which ends up as heat sooner or later) about 18 TW on average. Hence the factor 1/10000.

 

[DEMcMillan]

Remember that the numbers shown are increments from 1978 to 2006. The 1978 value was .212 W/m2, making the 2006 value from the table .339 W/m2. Assuming proportionality of the other estimates, the 2006 overall value would be .472 W /m2, a little higher than 1/10,000. Nonetheless, I am appreciative of your support of the numbers offered and your implied point on the potential for solar energy to supply more electricity for human use.