# Global warming: how much impact, if any, does waste heat have?
**URL:** https://boards.straightdope.com/t/global-warming-how-much-impact-if-any-does-waste-heat-have/282083
**Category:** Factual Questions
**Created:** [December 29, 2004, 11:36am UTC](https://boards.straightdope.com/t/global-warming-how-much-impact-if-any-does-waste-heat-have/282083 "2004-12-29T11:36:46Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@Colophon](https://boards.straightdope.com/u/Colophon)
#### Post date: [December 29, 2004, 11:36am UTC](https://boards.straightdope.com/t/global-warming-how-much-impact-if-any-does-waste-heat-have/282083/1 "2004-12-29T11:36:46Z")
Almost everything that is written about global warming seems to concentrate on the greenhouse effect cause by increasing concentrations of carbon dioxide, methane and other gases, but does the increased amount of physical heat generated by human activity also have a measurable impact?
Think about all the power stations burning coal, the millions of cars with hot engines, the central heating, the electric fires, the wood-burning stoves, plus all the heat generated by just about any electronic device… that must be a lot of heat escaping into the atmosphere. Is it enough to make a difference, or is it effectively lost in the intense heat coming in from the sun?
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### Author:  [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)
#### Post date: [December 29, 2004, 11:57am UTC](https://boards.straightdope.com/t/global-warming-how-much-impact-if-any-does-waste-heat-have/282083/2 "2004-12-29T11:57:17Z")
I managed to find Google for a figure of the energy received from the sun, which averages 345 W/sq. m., of which nearly half is retained as heat.
The earth has a total area of about 500 million sq. km., which makes the total energy being retained as heat similar to 50 trillion electric fires. I’ll let you draw your own conclusion 😉
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### Author:  [@Colophon](https://boards.straightdope.com/u/Colophon)
#### Post date: [December 29, 2004, 12:21pm UTC](https://boards.straightdope.com/t/global-warming-how-much-impact-if-any-does-waste-heat-have/282083/3 "2004-12-29T12:21:25Z")
> [@GorillaMan](#):
>
> I managed to find Google for a figure of the energy received from the sun, which averages 345 W/sq. m., of which nearly half is retained as heat.
>
> The earth has a total area of about 500 million sq. km., which makes the total energy being retained as heat similar to 50 trillion electric fires. I’ll let you draw your own conclusion 😉
OK… is that the energy that reaches the Earth’s atmosphere, or the actual surface? Remember that the waste heat is being released at ground level, whereas presumably large amounts of the sun’s energy is reflected away by clouds etc?
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### Author:  [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)
#### Post date: [December 29, 2004, 12:36pm UTC](https://boards.straightdope.com/t/global-warming-how-much-impact-if-any-does-waste-heat-have/282083/4 "2004-12-29T12:36:55Z")
[Here’s](http://www.grida.no/climate/ipcc_tar/wg1/fig1-2.htm) a better source than the one I found earlier - it still has a similar figure for the final absorbtion to the one I used for the calculation (168 vs 150 W/sq. m.). (I’ll show my working if you really want…)
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### Author:  [@Colophon](https://boards.straightdope.com/u/Colophon)
#### Post date: [December 29, 2004, 12:46pm UTC](https://boards.straightdope.com/t/global-warming-how-much-impact-if-any-does-waste-heat-have/282083/5 "2004-12-29T12:46:01Z")
Sorry, I missed the important part, “_of which nearly half is retained as heat_”.
Working in London, it’s hard to believe that all that heat blasting out of shop doorways etc isn’t warming the Earth, but there you go. (Well, I suppose it is, indirectly.)
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### Author:  [@GorillaMan](https://boards.straightdope.com/u/GorillaMan)
#### Post date: [December 29, 2004, 12:55pm UTC](https://boards.straightdope.com/t/global-warming-how-much-impact-if-any-does-waste-heat-have/282083/6 "2004-12-29T12:55:13Z")
I know what you mean - but go and stand on the roof of one of those buildings, and you’ll feel as cold as ever. Maybe it’s just the whole Londoner mentality, forgetting there’s a whole big world out there? 😛