I think that you missed a time term somewhere. You're looking at global energy use for an entire year. Don't you want to normalize that to joules used per time period (i.e. power) before determining how it affects instantaneous-average wind speeds?
The lowest published estimate I have seen for extractable global wind power [1] is as little as 18 terawatts in the paper by Miller, Gans, and Kleidon:
"Estimating maximum global land surface wind power extractability and associated climatic consequences"
18 terawatts happens to be exactly equivalent to an annual energy output of 5.67 x 10^20 joules.
18 terawatts is the low end of the estimated range in this paper; the upper end is 68 terawatts.
[1] The authors only considered wind farms placed on land, perhaps because offshore wind was so much more expensive in 2011. Their lowest estimate is too low, even if you stick with the rest of their methodology, after adding offshore wind.
> I think that you missed a time term somewhere. You're looking at global energy use for an entire year. Don't you want to normalize that to joules used per time period (i.e. power) before determining how it affects instantaneous-average wind speeds?
Nope. I may have messed up my calculations somewhere, but I'm quite confident in my equation (kinetic energy E = 1/2 x m x v^2).
That paper looks pretty interesting, but I'm going to follow my own advice and admit I don't know: I don't have the background to evaluate the validity of their atmospheric model. The conclusion[1] is pretty important if it's true.
[1] "Furthermore, we show with the general circulation model simulations that some climatic effects at maximum wind power extraction are similar in magnitude to those associated with a doubling of atmospheric CO2. "
> You've calculated that a year of energy consumption is equivalent to the kinetic energy of the atmosphere moving at 14m/s.
> This says nothing about how energy flows through the system, which is what will determine the impact on wind speeds.
shrug
I'm not gonna teach you guys high school physics. You can look up E = (1/2)mv^2 in any Physics textbook or your favorite search engine.
Before you disagree further, try calculating this yourself. Look up how to calculate the final speed of an object from kinetic energy. Make sure you plug energy units (i.e. joules) into E and power units (i.e. watts) into P. This isn't hard math, and the necessary equations are all over the internet.
> The value you plugged in was a year of energy consumption. Why not a day, or a century?
...because when I pulled the number from wikipedia it said it was the energy consumption for a year, not for a day or a century.
> You're not using the equations incorrectly, but they're not telling you what you think they are.
> They are telling you - if we store up all the power use of humanity for this length of time, then use it to blow the air, how fast will it go.
...no, it's telling me if we collect the energy used by humanity during this length of time, then use it to blow the air, how fast will it go. You cannot use "energy" and "power" as if they were interchangeable, they are not.
What you may be missing is that these physics equations go both directions. If we take the blowing of the air and use it to produce the energy used by humanity during this length of time, we'd expect to see the same decrease in speed.
There's nothing wrong with my sentence. It might be a bit informal, but "power use for a length of time" is a quantity of energy.
The decrease in speed you're describing is one time, not continuous. This is the issue both parent and I are pointing out. It's a shame to me that you aren't willing to see your error and instead resort to nitpicking, but I'm not going to try to explain a third time.
The lowest published estimate I have seen for extractable global wind power [1] is as little as 18 terawatts in the paper by Miller, Gans, and Kleidon:
"Estimating maximum global land surface wind power extractability and associated climatic consequences"
https://www.earth-syst-dynam.net/2/1/2011/esd-2-1-2011.html
18 terawatts happens to be exactly equivalent to an annual energy output of 5.67 x 10^20 joules.
18 terawatts is the low end of the estimated range in this paper; the upper end is 68 terawatts.
[1] The authors only considered wind farms placed on land, perhaps because offshore wind was so much more expensive in 2011. Their lowest estimate is too low, even if you stick with the rest of their methodology, after adding offshore wind.