Unexplored AGW Contributer

[Kempesh]

I've spend a lot of time on other boards defending the science and reality of human induced global warming. But among all the studies about greenhouse gases and their power to trap heat generated by the sun's radiation, I've come to realize that none of them take into account the heat we actually make.

Think about it, almost everything we do produces heat. Air conditioning is nothing more than a conveyor belt moving heat out of our houses, offices, and cars, and into the environment. In addition to the solar energy trapping gases our cars produce, they also introduce a huge amount of BTU into the air for every gallon of gas burned. Electric motors produce movement, but also heat as a byproduct of friction. All our coal fired and nuclear plants produce massive amounts of heat in addition to electricity.

Has any effort been made to catalog, or even estimate the amount of heat our species produces annually in addition to the extra heat our CO2 is trapping from the sun? Is it possible that this figure is a significant percentage of the rise in heat we have observed?

Inquiring minds want to know.

K

[Noclevername]

It may contribute very slightly, but it's just a matchstick compared to how much energy we get from the Sun.

[Kempesh]

Well of course it is nothing compared to the total energy we get from the sun. But that's not what we're talking about here, is it? When discussion AGW, we're only talking about the extra solar energy our greenhouse emissions are trapping. And that number is much, much smaller than the total amount of energy we receive from the sun.

I want to know how the extra heat trapped by our CO2, methane, etc, compares to the heat we create directly. Maybe our direct heat contribution really is negligible, I have no idea. But I haven't seen any research to suggest the idea has even been explored.

K

[Noclevername]

Well of course it is nothing compared to the total energy we get from the sun. But that's not what we're talking about here, is it? When discussion AGW, we're only talking about the extra solar energy our greenhouse emissions are trapping. And that number is much, much smaller than the total amount of energy we receive from the sun.

But the amount trapped is proportionate to the amount generated. If the amout we make ourselves is .00000000000001 of what we get from outside, then it'll be about .00000000000001 of what's trapped.

[Demigrog]

Total global energy consumption was about 15 TW in 2004. The average energy from the sun across the cross section of the earth is about 170000 TW. Converting to units more familiar to global warming discussions, the heat effect due to human activity comes out to 15TW / 5.1x10^14 m^2 = 0.029 W/m^2. Compared to 1366 W/m^2 for the sun.

The energy imbalance behind global warming is estimated at 0.85 W/m^2, or about 30 times the human waste heat effect.

Even if you consider feedback mechanisms that might enhance the effects, human activity is insignificant as far as waste heat.

Where waste heat is significant is in the urban heat island effect. Supposedly that is taken into account in global temperature records.

[Kempesh]

But the amount trapped is proportionate to the amount generated. If the amount we make ourselves is .00000000000001 of what we get from outside, then it'll be about .00000000000001 of what's trapped.

Shut up you, with your reasoning and big brain.

Punk.

K

[Kempesh]

Total global energy consumption was about 15 TW in 2004. The average energy from the sun across the cross section of the earth is about 170000 TW. Converting to units more familiar to global warming discussions, the heat effect due to human activity comes out to 15TW / 5.1x10^14 m^2 = 0.029 W/m^2. Compared to 1366 W/m^2 for the sun.

The energy imbalance behind global warming is estimated at 0.85 W/m^2, or about 30 times the human waste heat effect.

Even if you consider feedback mechanisms that might enhance the effects, human activity is insignificant as far as waste heat.

Where waste heat is significant is in the urban heat island effect. Supposedly that is taken into account in global temperature records.

That works. One less thing to feel guilty about I guess.

K

[novaderrik]

the heat made by AC units on houses and other structures is probably pretty closely matched by the "coldness" it creates.
of course, that's just taking into account what happens at the AC unit itself doing what it was designed to do- there is heat created in making and transporting the electricity to run the AC unit, and some waste heat from the AC unit itself.

[hhEb09'1]

the heat made by AC units on houses and other structures is probably pretty closely matched by the "coldness" it creates.

Depends upon what you mean by closely. That would be a measure of its efficiency, more or less, and there are limits on how efficient it can be.

[korjik]

That works. One less thing to feel guilty about I guess.

K

Depends. If the heat island effect causes a climate change that turns a large area into a desert, that would be as bad as if AGW did it.

[NEOWatcher]

the heat made by AC units on houses and other structures is probably pretty closely matched by the "coldness" it creates.
of course, that's just taking into account what happens at the AC unit itself doing what it was designed to do- there is heat created in making and transporting the electricity to run the AC unit, and some waste heat from the AC unit itself.

And none of that matters except for the energy usage. No matter what the efficiency is, the extra heat generated is ultimately coming from the fuel that was burned to do the work. That fuel is ultimately from the sun.
Now the issue is, when did the sun play a part. If wind, water, solar, then its a wash.
If fossil fuels, then we have moved that solar energy from the past to the present. And the human contribution can be the amount of this relocation.

[MAPNUT]

I asked this question a couple years ago: http://www.bautforum.com/general-sci...-directly.html and only got some seat-of-the-pants answers. Demigrog does a nice job of quantifying it; thanks. (assuming you're right .

[Noclevername]

If fossil fuels, then we have moved that solar energy from the past to the present. And the human contribution can be the amount of this relocation.

And add to that, when we burn fossil fuels, the stored solar energy built up slowly over several million years gets converted to heat in a much shorter time.

[NEOWatcher]

And add to that, when we burn fossil fuels, the stored solar energy built up slowly over several million years gets converted to heat in a much shorter time.

I didn't think I needed to explain that, but yes, that is an important part of the point I was trying to make.
I picture global warming as a direct relationship on what energy we are pulling out of that which has been sequestored.

[Noclevername]

I picture global warming as a direct relationship on what energy we are pulling out of that which has been sequestored.

It may make a slight difference, but it's the added insulation that provides the bulk of the GW changes. The excess heat we generate from burning stuff radiates out into space at the same rate as sun-derived heat. More greenhouse gas means more heat kept around, and most of that still comes from O'l Sol.

[NEOWatcher]

It may make a slight difference...

Yes; but I did say relationship.
We can put as much greenhouse gas in the atmosphere as long as the fuel comes from above ground environmental sources, and that's because the gas came from the atmosphere anyway, and we are just recycling it.
Any excess gas buildup* is in relation to what we pull out of the ground.

So; when I say relationship, I'm talking about all the effects that are associated with it.

*Tums anyone?

[Noclevername]

Yes; but I did say relationship.
We can put as much greenhouse gas in the atmosphere as long as the fuel comes from above ground environmental sources, and that's because the gas came from the atmosphere anyway, and we are just recycling it.
Any excess gas buildup* is in relation to what we pull out of the ground.

So; when I say relationship, I'm talking about all the effects that are associated with it.

*Tums anyone?

*Burp* Thanks for the Tums.

If we burn wood from a forest, then build a parking lot there so the forest can't grow back, that's almost as effective, just on a smaller scale. Decades or centuries of solar buildup instead of MYs.

[Ken G]

Depends. If the heat island effect causes a climate change that turns a large area into a desert, that would be as bad as if AGW did it.

Or even moreso, if deforestation did it. It is certainly clear enough that human activity has affected our environment profoundly, even in the absence of AGW. That's the core fallacy in the "we humans are too puny to have that big of an effect on our planet" argument.

[Noclevername]

That's the core fallacy in the "we humans are too puny to have that big of an effect on our planet" argument.

Right, it's like saying bacteria and viruses are too puny to make us sick.

[Ken G]

Yes, which is just how the early skeptics felt, isn't it? Not that we can reason from analogy, but it is interesting to note.

[Ara Pacis]

Don't forget radioactives as a heat source. Those were generated a few suns ago.

[NEOWatcher]

If we burn wood from a forest, then build a parking lot there so the forest can't grow back, that's almost as effective, just on a smaller scale. Decades or centuries of solar buildup instead of MYs.

Yes; that is an important point. I will add a qualification that the above ground sources are to be sustainable.

I view deforestation as a seperate issue from energy use, but under the umbrella of GW, I guess it applies.

[kzb]

I've a couple of issues with the 15TW human energy consumption figure. I think the number has come from Wikipedia.

On the one hand, some of that energy is from solar-powered sources eg hydroelectric, biofuels, wind etc. So that does not count in this context as the sunlight would heat the Earth anyway, whether or not we diverted it to these uses.

On the other hand, it's not clear if the ELECTRICAL energy consumption is electricity consumption, or if it includes the waste heat from generating that electricity. For example if we have 1TW of electricity consumption, it has need another 2TW of heat to produce that from fossil fuels or nuclear generation. The Wiki article is not clear on this, but it would have a significant effect on the 15TW figure.

[Demigrog]

I've a couple of issues with the 15TW human energy consumption figure. I think the number has come from Wikipedia.

On the one hand, some of that energy is from solar-powered sources eg hydroelectric, biofuels, wind etc. So that does not count in this context as the sunlight would heat the Earth anyway, whether or not we diverted it to these uses.

On the other hand, it's not clear if the ELECTRICAL energy consumption is electricity consumption, or if it includes the waste heat from generating that electricity. For example if we have 1TW of electricity consumption, it has need another 2TW of heat to produce that from fossil fuels or nuclear generation. The Wiki article is not clear on this, but it would have a significant effect on the 15TW figure.

Yep, I was lazy and used Wikipedia's value. (I was also lazy and didn't link my data sources) I did not intend for it to be an exact figure, just a back-of-the-envelope type number. It is also an upper limit--not all of the energy would be released as waste heat (some would be trapped in chemical bonds, etc).

Just for comparison, I converted the DOE's 2004 estimate of world energy use (447 quad btu) and converted it to Watts... and got 14.9 TW.

[kzb]

Over on 'Questions and Answers', there is a related thread "what is Earth's intrinsic power". There appear to be some discrepancies with the accepted radiogenic heating of 19TW and the observed effects eg earthquakes. Perhaps the heat coming out of the crust is bigger than we think.

[George]

Just for comparison, I converted the DOE's 2004 estimate of world energy use (447 quad btu) and converted it to Watts... and got 14.9 TW.

I would expect you could double or triple this amount if the comsumption rate is energy used by the consumer, and not total heat output. For instance, a 100 watt light bulb produces 100 watts of heat (asuming the light doesn't escape into space), but around 300 watts of heat are generated at the power plant in order to give the consumer the 100 watts needed for the bulb.

[Demigrog]

I would expect you could double or triple this amount if the comsumption rate is energy used by the consumer, and not total heat output. For instance, a 100 watt light bulb produces 100 watts of heat (asuming the light doesn't escape into space), but around 300 watts of heat are generated at the power plant in order to give the consumer the 100 watts needed for the bulb.

The EIA data uses the gross heat content of each fuel, as opposed to the net heat content which only represents the usable heat. So, it is all inclusive.

[George]

Thanks. I glanced around for it, but missed it.

[kzb]

Let's say the human power consumption from non-renewables is 14TW.

Solar energy is 174000TW striking the planet. Some of this will be directly reflected, so not contributing to heating. I don't know how much, but I suspect only a small proportion of it is reflected back into space directly.

An estimate of the proportion of anthropogenic direct heating is therefore 100*14/174000 = 0.008% of the solar energy striking the planet.

[kzb]

Actually, the "Bond albedo" of the Earth is 0.29, according to Wikipedia:

http://en.wikipedia.org/wiki/Bond_albedo

This is the fraction of the entire EM spectrum that is scattered back into space. So the solar power absorbed is presumably (1-0.29)*174000TW = 124000TW. The calc in my previous contribution is then:

proportion of our direct heating = 100*14/123000 = 0.011%