How Much Energy?

January 20, 2007 2:27 PM

We hear a lot about global warming that is attributable to greenhouse effects, etc. Can anyone link-to/guestimate the actual thermal energy we are putting into the planet directly, as a result of burning, moving, etc.?

After looking at this pretty picture illustrating oil consumption, I realized there would be a lot of raw heat unleashed by burning that much oil. I expect direct heating is causing nowhere near as much as the increased solar capture caused by CO2, but it must none-the-less be a real big number.

Maybe we could also colloquialise the inferno some-how? e.g., Burning our oil production would be equivalent to burning X library of congresses, or stuffing N stadiums with TNT.

(Americans, If you're calculating, please include SI units.)

posted by clord to science & nature (9 comments total)

I found this related posting, which might help.
posted by clord at 2:33 PM on January 20, 2007

Figures for the period 1973 to 1995 included here (fig. 6-14). Extrapolate as you need, or look for later versions to satisfy your itch.
posted by paulsc at 2:43 PM on January 20, 2007

Global energy consumption in 1996 was around 390 exajoules; my rough attempt at extrapolating the historical numbers found at that link, without actually doing the regression, says it would be around 450 exajoules in 2006. (An exajoule is 10¹⁸ joules.)

Almost all of this is probably eventually released as heat. Although you'd have to take into account the fact that some methods of generating energy, such as hydroelectric, only generate as much heat as would be generated anyway from natural processes if the generating plant weren't there, so there's no net heat added to the environment. But the most common methods of energy generation, including burning of fossil fuels, certainly would.

If you want to know how much 450 exajoules per year translates to in terms of global warming, that's a much harder question, because you may have the majority of that heat being dumped into the atmosphere, but then the oceans act as a heat sink, but that's by no means instantaneous.

If the heat were all dumped directly into the oceans (it's not), and the oceans were well-mixed (in reality, it's not) so that that heat were evenly distributed, it would only increase ocean temperatures by about 0.00008°C per year, by my calcluations.
posted by DevilsAdvocate at 2:55 PM on January 20, 2007

Let's compare that number to the energy from the sun hitting the surface of the earth. Averaged over the entire surface of the planet in a 24 hour period, the flux of solar energy impinging on the earth is 164 W/m^2. The earth has a surface area of about 5x10^14 m^2, so the total power is 8x10^16 W. Over a day, that's 7x10^21 J, or 7,000 exajoules. So the sun contributes over ten times the amount of energy each day than humans contribute in a year.
posted by mr_roboto at 3:30 PM on January 20, 2007

Thanks for what we have so far, but I'd like to communicate these huge numbers to a less technical audience, as well. This was a major reason for the question. I can't think of a good analogy for this level of energy.

Are there any common events which generate as much energy as our yearly oil production? Some (understandable) multiple of a common event?
posted by clord at 5:37 PM on January 20, 2007

clord, if you wish, you could take DevilsAdvocate's and mr_roboto's numbers and compare them to the energy released in the nuclear explosion produced by the Hiroshima "Little Boy" bomb. Little Boy had a yield of 15 kilotons of TNS, which is approximately 63 terajoules (1 terajoule is 10¹² joules).

Global annual energy consumption (1996):
6.19 million Hiroshima bombs

Daily energy from the sun:
111 million Hiroshima bombs
posted by RichardP at 5:53 PM on January 20, 2007

Umm... TNT, not TNS.
posted by RichardP at 5:54 PM on January 20, 2007

I tried that, but even 6.8 million is a bit big. oh well.
posted by clord at 8:45 AM on January 21, 2007

Here's a nontechnical way it was described in a book I'm reading, "Something new under the sun; an environmental history of the 20th century world," J.R. McNeill:

We have probably deployed more energy since 1900 than in all human history before 1900. My very rough calculation suggests that the world in the 20th century used 10 times as much energy as in the thousand years before 1900AD. In the 100 centuries between the dawn of agriculture and 1900, people used only about two-thirds as much energy as in the 20th century.

p.15. The guy is a historian. There are a lot more numbers and tables in there too, of course.
posted by Listener at 10:39 PM on January 22, 2007