Jeff Engr asked in EnvironmentGlobal Warming · 8 years ago

Waste heat a meaningful impact on global surface temperatures?

I saw this and the numbers looked to be MUCH more significant than I would have imagined. Enough so that I want to post here and ask a question. What do you think? I have not checked the math, but Dr. Roy Spencer is well educated in this field so I am inclined to believe he did not make a significant error.

What do you think? Waste heat could account for as much a 0.33 w/square meter for CONUS (continental US). This is 20.6% of what solar forcing is. If this impact is true then I would think the overall impact would be tremendous!

What are your thoughts?



He was only comparing solar input for CONUS against waste heat from CONUS. Putitng global soalr against CONUS waste heat would be deceptive.

I will have to run some numbers on the CONUS portion of the Global, but even if he is off by an order of magnatude, wate heat being 2% would still be significant and waste heat is 24/7 and solar input is not.

5 Answers

  • Trevor
    Lv 7
    8 years ago
    Favorite Answer

    It looks like Dr Spencer has got his numbers wrong.

    Solar radiation provides the Earth with 174 petawatts of heat energy annually, waste heat accounts for 13 terrawatts. In percentage terms this is 99.97% and 0.007% of the total incoming energy. The remainder comes mainly from geothermal energy (radioactive decay and orbital friction), and tidal energy (friction).

    In terms of Watts per square metre, the average at Earth’s surface is 342W/m²/yr, waste heat accounts for 0.024 W/m²/yr, significantly less than Dr Spencer’s figure.

    What Dr Spencer is doing, and it’s very misleading, is assuming that all energy consumed in the US is converted into waste heat and that all of that waste heat subsequently contributes to warming. He’s wrong on both counts.

    Most energy does indeed end up as heat but not all of it, but only a proportion of that heat energy is actually radiated away from Earth’s surface as thermal radiation and subsequently trapped by the greenhouse gas molecules in the atmosphere. Dr Spencer’s calculation would require that every bit of heat were trapped and if that were the case the Earth would have spontaneously combusted a long, long time ago. It would be a one way street – all incoming heat energy, including that from the Sun, would be trapped within the atmosphere, none would ever escape. Earth would just get hotter and hotter until it melted.

    You may recall that it was Dr Spencer’s temperature record that was favoured by the skeptics as it showed the least amount of warming. That was until it was pointed out he’d got those figures wrong as well, once corrected they showed the same warming as all other records.

    I think he does need to be a bit more careful with his calculations.

    For more info do a search for “Earth’s Energy Budget”.

    - - - - - - - - -


    Thanks for the added details. The percentage figures I stated in my original answer are global averages but they’re not going to change all that much wherever you are on the planet unless you’re working to a very high resolution. If you happen to pick a geologically active area of Iceland that contains many geysers and geothermal vents then clearly the figures will be different – but only at or close to ground level.

    For a landmass the size of the US that lies in the mid latitudes the figures are accurate.

    What I omitted to mention in my original answer is that the sum total of anthropogenic forcing is about 1.6W/m²/yr – global average, also applicable to the US as a whole. The 0.024 W/m²/yr of waste-heat would therefore account for 1.5% of observed warming, but only if all of that waste-heat contributed to global warming, which clearly doesn’t happen.

    Some of that waste heat will be absorbed by the oceans where it will remain for millennia, a significant amount will be lost directly into space without any interactions with greenhouse gas molecules, some will be generated at frequencies that don’t permit absorption to take place. I don’t have figures to hand that would allow me to calculate just how much waste heat could contribute to global warming, but it is going to be a significant reduction from the 1.5% figure.

    If you do get the chance to run your own figures then please add further details, it would be interesting to see what you come up with.

  • 8 years ago

    It was an interesting read. And from the comments, I think I most closely align with this one:

    " Slipstick says:

    January 9, 2013 at 8:55 PM

    Ignoring that the entire energy consumption does not equate to the waste heat (a fair portion, although I have no way of calculating how much and it may be negligible) since the energy is used to perform work or is stored in constructions from the macro to the nano, I don’t understand how the value over less than 2% of the Earth’s surface can be compared to the global total."

    Another source I checked out sas the AMS definition of anthropogenic heat:

    "anthropogenic heat - Heat released to the atmosphere as a result of human activities, often involving combustion of fuels. Sources include industrial plants, space heating and cooling, human metabolism, and vehicle exhausts. In cities this source typically contributes 15–50 W m-2 to the local heat balance, and several hundred W m-2 in the center of large cities in cold climates and industrial areas."

    My general conclusion would be that there is indeed an Urban Heat Island effect and it needs to be carefully considered when doing an analysis of surface temperature measurements.

  • 8 years ago

    You're an energy auditor. You weren't wearing your professional hat when you read Spenser's article.

    Electricity is about 1/3 of the energy use in the U.S. According to the CIA factbook the U.S produced 4.12 trillion kw-hours of energy in 2010, and the area is about 10 million square km. If you've run those numbers yourself, you know that Spenser has to be off by considerably more than one order of magnitude. If Spenser had given this analysis while working for you, you would have fired him and contacted your firm's lawyers to deal with any project he had worked on.

    Source(s): %2Bmix%26tbm%3Disch%26tbo%3Du&zoom=1&q=U.S.+energy+mix&usg=__6zn0dCJUuiBgUTg0fWBnYoWdN2g=&docid=o4rdOjfEOTFxRM&hl=en&sa=X&ei=P3XvUIrSNK-10QHk4IHgBw&ved=0CEAQ9QEwAQ&dur=148
  • 8 years ago

    Spencer is an anti-science denier. Completely unreliable. Citing him makes about as much sense going to David Duke for information about World War II and the Holocaust.

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  • Anonymous
    8 years ago

    I went through much of the article and although I am convinced he is a GW skeptic, I am not at all convinced of his theory.

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