Ozone hole may disappear by 2050

[taks]

Outside of our collision course with the Andromedia galaxy, I suspect that the exceptionally cold dust of nebulae and whatnot are rather insignificant.

energy does not have to be warm. and i would think you also aren't certain exactly what is out there, not just dust, but radiation, too. in short, you, nor i, know.

 

Uh, come again?  The Earth is a black body emitter, particularly in the low infrared (which happens to be the range the CO2 absorbs).  If the CO2 starts blocking it, and it's not absorbed by it because it's reached its threshold, it's not escaping into space, unless it converts to a different wavelength (which would result in something absorbing or giving that photon energy).

hate to tell you but lots of energy is reflected back into space. you're referring only to that which makes it to the surface in the first place. that's the mechanism... energy reaches the earth and it reradiates (it actually does shift in wavelength, btw). CO2 (and other things) absorb certain wavelengths but some make it back out regardless. some gets reflected before arriving.

 

How can it get into space if it can't get past the CO2 wall?  Hence why I mentioned reflected energy, because the energy emitted from the Earth would be reflected off of the atmosphere as it tried to escape Earth, back down to Earth.

not all energy makes it to the surface in the first place. that was part of my point. also, you were the one that just got done saying not all gets absorbed (75% was your number). it ain't a "wall" if only 75% is absorbed.

 

taks

[taks]

So Taks, are you published on this matter?

no, but it doesn't take publication on this matter to understand the science.

 

What publications have you read recently which support your contention that this global warming stuff is still under debate by scientists?

holy cow, i suggest you look up the work McIntyre and McKittrick or Roger Pielke Sr. and the list goes on and on. just because al gore runs at the mouth doesn't mean it's "settled".

 

I thought the debate was over among the reputable scientists and it was agreed that civilization is having a significant and decisive impact on global warming.

<{POST_SNAPBACK}>

according to al gore, yes. according to the scientific method. no.

 

taks

[taks]

there is a consensus that the Earth is warming,

yes. the actual number is 0.6 degrees celsius as reported by NASA-GISS. however, NASA also makes it clear that our resolution is greater than 1 degree celsius, i.e. 0.6 is not really within our ability to resolve.

 

and that human activity has some impact on it: the magnitude of the impact (and the underlying warming trend, which may or may not be completely natural and many measures of magnitude larger than the human contribution) are yet to be determined.

no, well not really. this is not settled. not even close. activists claim it is and keep pointing to a "consensus" that only the media seem to be aware of.

 

He still argues that theworld is not warmer than it was, which I dispute. No-one can say for certain what has caused any warming, with any certainty, yet.

<{POST_SNAPBACK}>

he is right and wrong... we are warmer now than in the 70s, but it was actually about the same in the 30s. it was cooler, MUCH cooler during the little ice age which really didn't end untill the 1800s. however, there is evidence it was MUCH warmer during what is known as the mideval warming period.

 

taks

[alanschu]

energy does not have to be warm. and i would think you also aren't certain exactly what is out there, not just dust, but radiation, too. in short, you, nor i, know.

 

Well, current astronomy theory has the collective universe having an average temperature of 2.73 Kelvin. So it's not exactly toasty warm. Convection and Conduction are pretty much moot as a result. And what do you mean by radiation? We can already detect radiation coming in every direction (considering radiation is emitted along the Electromagnetic Spectrum). Outside of our sun, the closest blackbody emitter is Proxima Centauri, at the cool distance of about 4.2 light years away. Given the intensity of light is measure is signficantly influenced by the distance (I = X * 1/r^2), this means it's not affecting us too much.

 

We receive more EM radiation from the Sun's energy reflecting off of Jupiter than we do from the nearest star.

 

hate to tell you but lots of energy is reflected back into space. you're referring only to that which makes it to the surface in the first place. that's the mechanism... energy reaches the earth and it reradiates (it actually does shift in wavelength, btw). CO2 (and other things) absorb certain wavelengths but some make it back out regardless. some gets reflected before arriving.

 

The energy emitted in the form of radiation is, according to the Stefan-Boltzman law, is emitted in the low infrared. Which happens to also be the range of EM radiation that is blocked and absorbed by CO2. I'm well aware of shifts in wavelength for light, since the energy that comes in is not part of the low infrared.

 

And yes, energy is reflected back into space, but the peak of the EM spectrum that the Sun emits energy at is in the visible spectrum. Which is not reflected by our atmosphere (otherwise we wouldn't see it). Ultraviolet light is also not reflected by our atmosphere). This energy heats the Earth, which as a black body emitter, radiates its own energy at a certain length (it's also the only way energy can leave Earth, since convection and conduction require matter, and there's not much in space)

 

not all energy makes it to the surface in the first place. that was part of my point. also, you were the one that just got done saying not all gets absorbed (75% was your number). it ain't a "wall" if only 75% is absorbed.

 

As much as you were suggesting that 75% was close enough to the maximum that there won't be a significant increase.

 

And I'm not saying that this is a concern now, and I never said that there was a wall now. But you were saying that even at 100% it was insignificant. At 100%, very little of the energy radiated from the planet can get past the atmosphere. It will either get absorbed, or reflected back.

 

The problem with the absorbed stuff is not only does it reemit EM radiation (which might not be bad thing, as it radiates out into space...though it also radiates back down to Earth). However, the energy absorbed by CO2 can also warm things up through convection and conduction, transfer its energy in that way.

 

The stuff that the planet emits and gets reflected back will get absorbed by something else, which will raise its energy level. This will increase conduction/convection temperature changes, as well as Black Body Emitter EM radiation changes. Since this raditation will, on the whole, be reabsorbed by the planet itself (some will be reflected as well, but since it can't escape the atmosphere and it's not going to bounce around forever, it will be absorbed by something), it will warm the planet, which will result in evaporating water, reducing CO2 sinks and increasing CO2 in the atmosphere. The concern is that if CO2 concentrations increase (since they're not at 100%), less and less energy will be able to escape. In order to balance itself, the planet will have to warm up (since the energy isn't escaping and will be reabsorbed...unless you think that trapping energy will somehow cool the planet) to a temperature where enough of its energy will be emitted above the low infrared (since hotter black body emitters have shorter wavelength radiation) in order to reach an equilibrium between the Sun's radiation and our planet's ability to regulate its temperature.

Edited May 29, 2006 by alanschu

[taks]

Well, current astronomy theory has the collective universe having an average temperature of 2.73 Kelvin.  So it's not exactly toasty warm.

read what i said, heat wasn't what i was referring to. matter, energy, of any sort. either way, this is a relatively moot point. at least, a minimal player but a player nonetheless.

 

The energy emitted in the form of radiation is, according to the Stefan-Boltzman law, is emitted in the low infrared.  Which happens to also be the range of EM radiation that is blocked and absorbed by CO2.

either ALL of the energy is absorbed or not, alanschu. make up your mind. if it is ALL absorbed, then how can we absorb any more heat due to CO2? if the latter is true, then my original point is proved beyond a shadow of a doubt: CO2 increases won't make a difference. if not, then, as i have stated several times now, it is reradiated into space. really man...

 

I'm well aware of shifts in wavelength for light, since the energy that comes in is not part of the low infrared.

energy arrives at the earth from a lot of wavelengths. some is shifted after being absorbed by the earth then reradiated.

 

And yes, energy is reflected back into space, but the peak of the EM spectrum that the Sun emits energy at is in the visible spectrum. Which is not reflected by our atmosphere (otherwise we wouldn't see it). Ultraviolet light is also not reflected by our atmosphere). This energy heats the Earth, which as a black body emitter, radiates its own energy at a certain length (it's also the only way energy can leave Earth, since convection and conduction require matter, and there's not much in space)

 

As much as you were suggesting that 75% was close enough to the maximum that there won't be a significant increase.

it is, and there won't.

 

But you were saying that even at 100% it was insignificant.  At 100%, very little of the energy radiated from the planet can get past the atmosphere.  It will either get absorbed, or reflected back.

NO. man, this isn't rocket science. CO2 ONLY ABSORBS CERTAIN WAVELENGTHS!!! how many times do i have to say this? once it has reached its 100% peak, CO2 is no longer a contributor, and it's not far from there now (CO2 will need to get to toxic levels before it is 100% of its absorption capacity, btw).

 

CO2 is a bit player as it is, and once it is at 100%, it can't contribute any further. this has ZERO bearing on other frequencies radiated by the planet.

 

The concern is that if CO2 concentrations increase (since they're not at 100%), less and less energy will be able to escape.

at certain wavelengths, only.

 

In order to balance itself, the planet will have to warm up (since the energy isn't escaping and will be reabsorbed...unless you think that trapping energy will somehow cool the planet) to a temperature where enough of its energy will be emitted above the low infrared (since hotter black body emitters have shorter wavelength radiation) in order to reach an equilibrium between the Sun's radiation and our planet's ability to regulate its temperature.

<{POST_SNAPBACK}>

and this amount is only a few degrees worst case (when analyzed by credible scientists). given that the planet has supported life at 10s of degrees warmer than now, i don't think there's any concern here. in fact, given that we are still sort of coming out of an ice age, i'd posit that a few degrees warmer is what we want.

 

taks

[alanschu]

read what i said, heat wasn't what i was referring to. matter, energy, of any sort. either way, this is a relatively moot point. at least, a minimal player but a player nonetheless.

 

Heat is a type of energy. What other energy were you referring to? Mechanical Energy? Sound energy? And heat is directly correlated with the EM radioactive properties of matter. It is a minimal player, and according to most astronomers, an insignificant player. It does not, and will not, play a role in affecting the temperature of our planet.

 

either ALL of the energy is absorbed or not, alanschu. make up your mind. if it is ALL absorbed, then how can we absorb any more heat due to CO2? if the latter is true, then my original point is proved beyond a shadow of a doubt: CO2 increases won't make a difference. if not, then, as i have stated several times now, it is reradiated into space. really man...

 

What?

 

NO. man, this isn't rocket science. CO2 ONLY ABSORBS CERTAIN WAVELENGTHS!!! how many times do i have to say this? once it has reached its 100% peak, CO2 is no longer a contributor, and it's not far from there now (CO2 will need to get to toxic levels before it is 100% of its absorption capacity, btw).

 

CO2 is a bit player as it is, and once it is at 100%, it can't contribute any further. this has ZERO bearing on other frequencies radiated by the planet.

 

And, as I've stated before, the certain wavelengths are the wavelengths that the Earth radiates energy as a block body emitter.

 

energy arrives at the earth from a lot of wavelengths. some is shifted after being absorbed by the earth then reradiated.

 

Yes. And it's reradiated in the low infrared, which is a frequency that CO2 affects.

 

at certain wavelengths, only.

 

I know, at the low infrared. Which is what the Earth radiates most of its energy at.

 

and this amount is only a few degrees worst case (when analyzed by credible scientists). given that the planet has supported life at 10s of degrees warmer than now, i don't think there's any concern here. in fact, given that we are still sort of coming out of an ice age, i'd posit that a few degrees warmer is what we want.

 

A few degrees warmer will not result in a significant change in the wavelength emission of the planet, so energy will still be radiated at the level that CO2 affects.

[alanschu]

Interesting:

 

http://physics.indiana.edu/~brabson/p510/s...vesurfaces.html

 

It's been a while since I took my astronomy and physics courses, so I've had to check on some things to make sure I'm not remembering something wrong or making other mistakes

 

Heat is energy.

 

Heat is the total amount of energy possessed by the molecules in a piece of matter. This energy is both kinetic energy and potential energy.

 

When heat, (i. e., energy), goes into a substance one of two things can happen:

 

    1. The substance can experience a raise in temperature. That is, the heat can be used to speed up the molecules of the substance. Since Kelvin temperature is directly proportional to the average kinetic energy of molecules in a substance, an factor increase in temperature causes an equal factor increase in the average kinetic energy of the molecules. And if the kinetic energy of the molecules increase, the speed of the molecules will increase, although these increases are not directly proportional. The kinetic energy of a body is proportional to the square of the speed of the body.

 

    2. The substance can change state. For example, if the substance is ice, it can melt into water. Perhaps surprisingly, this change does not cause a raise in temperature. The moment before melting the average kinetic energy of the ice molecules is the same as the average kinetic energy of the water molecules a moment after melting. Although heat is absorbed by this change of state, the absorbed energy is not used to speed up the molecules. The energy is used to change the bonding between the molecules. Changing the manner in which the molecules bond to one another constitutes a change in potential energy. Heat comes in and there is an increase in the potential energy of the molecules. Their kinetic energy remains unchanged.

 

So, when heat comes into a substance, energy comes into a substance. That energy can be used to increase the kinetic energy of the molecules, which would cause an increase in temperature. Or that heat could be used to increase the potential energy of the molecules causing a change in state that is not accompanied by an increase in temperature.

 

When I mentioned 2.73 Kelvin, that is a temperature rating. But an exceptionally cold one. I can't imagine something having too much potential energy that close to absolute zero, so I suspect a lot of the particles not relating to stars and whatnot do not have much energy (heat) at all. I was going to say heat is energy in my previous post, but I wasn't sure I was correct in that statement so I said heat is a type of energy (which ironically is wrong statement). I was equating heat with temperature (a common mistake). I still contend that something that has an average temperature of 2.73 doesn't have that much heat/energy. Temperature is related to kinetic energy (double the kinetic energy and you double the measurement on the Kelvin scale). I should have known better after thinking a bit about things like the Specific Heat Capacity and whatnot :">

 

Considering the temperature of the fusion reactions of stars is in the billions of Kelvin, and the fact that no matter how small of a sample we look at in space with Hubble for any type of time exposure, we see clusters of galaxies (which naturally are made up of a massive amount of stars, which have fusion reactions in them otherwise they wouldn't by warm enough to emit the visible light for us to see on the HST), leads me to believe that there's a whole heck of a lot of particles out there that don't have much energy in them at all.

 

Though it does have to do with entropy and whatnot, which wasn't covered in too much detail in my physics and astronomy courses.

Edited May 29, 2006 by alanschu

[213374U]

Heat is a type of energy.  What other energy were you referring to?  Mechanical Energy?  Sound energy?  And heat is directly correlated with the EM radioactive properties of matter.  It is a minimal player, and according to most astronomers, an insignificant player.  It does not, and will not, play a role in affecting the temperature of our planet.

Taks probably meant radiation at shorter wavelengths. Radiation at those wavelengths isn't "heat" per se (as that's IR radiation), but visible light (which incidentally is the spectrum band in which most of the sun's energy is emitted) and UV rays. That's how I interpreted his post, anyway.

 

 

And, as I've stated before, the certain wavelengths are the wavelengths that the Earth radiates energy as a block body emitter.

You are not taking into consideration that the atmosphere radiates heat in both directions, not only towards the surface. Convection and condensation to form clouds transfer a lot of heat into the atmosphere, which is emitted to space. If the temperature increases, those processes increase as well.

 

 

A few degrees warmer will not result in a significant change in the wavelength emission of the planet, so energy will still be radiated at the level that CO2 affects.

True. I'm sure you realize that if you don't consider other means of liberating heat, this logic leads to a cyclical heat exchange between the atmosphere and the surface of the planet that would continue until the surface reached a temperature high enough to start emitting most of its radiation in the near IR and visible spectre, effectively a furnace. That is obviously absurd.

 

Therefore, and considering the present heat emission properties of the atmosphere (and taking into consideration what taks said about CO2 heat absorption) I'm inclined to think that the impact of human CO2 emissions in global warming is negligible.

[alanschu]

Taks probably meant radiation at shorter wavelengths. Radiation at those wavelengths isn't "heat" per se (as that's IR radiation), but visible light (which incidentally is the spectrum band in which most of the sun's energy is emitted) and UV rays. That's how I interpreted his post, anyway.

 

If the average temperature is 2.73 Kelvin though, and there's an immeasurably large number of stars that have fusion reactions in them that range in Billions of Kelvin, means that there's a whole lot of stuff out there that doesn't have much energy at all. And since they don't have enough heat/energy, the bulk of their EM radition will be with really long wavelength.

 

You are not taking into consideration that the atmosphere radiates heat in both directions, not only towards the surface. Convection and condensation to form clouds transfer a lot of heat into the atmosphere, which is emitted to space. If the temperature increases, those processes increase as well.

 

An important thing to consider is that clouds would also prevent additional energy from the sun as well. White clouds are fantastic reflectors for visible light obviously. I actually did comment in post 104 that energy absorbed in the atmosphere would also be radiated into space as well. I guess the big thing is that currently some of it seems to get past (as we only have 75% effectiveness), which means of those photons, 100% of the energy is gonzo. Now, if none of it escapes, at the very least we should be able to conclude that not all of it is gone.

 

I know has air temperature rises, the amount of water vapour that can be absorbed in the air increases. Is cloud formation a factor of absolute quantity of water vapour in the air, or is it also a factor of what percentage of the air has water vapour?

 

True. I'm sure you realize that if you don't consider other means of liberating heat, this logic leads to a cyclical heat exchange between the atmosphere and the surface of the planet that would continue until the surface reached a temperature high enough to start emitting most of its radiation in the near IR and visible spectre, effectively a furnace. That is obviously absurd.

 

How else does the planet liberate heat outside of EM radiation? I'm not so sure it really is that absurd either. It would help make sense of the runaway greenhouse on Venus, a planet which is significantly hotter than Mercury (so it's not just distance to the Sun).

 

Therefore, and considering the present heat emission properties of the atmosphere (and taking into consideration what taks said about CO2 heat absorption) I'm inclined to think that the impact of human CO2 emissions in global warming is negligible.

 

I agree. The discussion more evolved into discussing the plausibility of whether or not a runaway greenhouse could occur.

Edited May 29, 2006 by alanschu

[213374U]

I was going to say heat is energy in my previous post, but I wasn't sure I was correct in that statement so I said heat is a type of energy (which ironically is wrong statement).

Well, energy is energy. Saying that heat is a form of energy is not wrong, since heat can actually be transformed into other forms of energy.

 

 

I still contend that something that has an average temperature of 2.73 doesn't have that much heat/energy. [...]

 

Considering the temperature of the fusion reactions of stars is in the billions of Kelvin, and the fact that no matter how small of a sample we look at in space with Hubble for any type of time exposure, we see clusters of galaxies (which naturally are made up of a massive amount of stars, which have fusion reactions in them otherwise they wouldn't by warm enough to emit the visible light for us to see on the HST), leads me to believe that there's a whole heck of a lot of particles out there that don't have much energy in them at all.

That's correct. But what really counts when calculating the average temperature of the universe is the immensity of empty space. Ultra low particle densities in interstellar space more than make up for the many stars that make up those huge galaxy superclusters. All in all, space is more empty than cold.

 

I read somewhere that if you could find a way to compensate for the very nasty effects of vacuum and harmful radiation, you could make spacewalks in a t-shirt, since loss of heat due to radiation is a rather slow process at relatively low temperatures.

[alanschu]

It seems as though, according to a quick look around through the internets and my old astronomy textbook, heat = energy.

 

Temperature = kinetic energy, but temperature != total energy.

 

That link I posted indicated that heat = kinetic energy + potenetial energy = total energy.

 

Taks probably meant radiation at shorter wavelengths. Radiation at those wavelengths isn't "heat" per se (as that's IR radiation), but visible light (which incidentally is the spectrum band in which most of the sun's energy is emitted) and UV rays. That's how I interpreted his post, anyway.

 

Empty space wouldn't contribute to an average temperature rating, since there's nothing to hold the energy.

[alanschu]

I see your italicized name down there....hurry up

[213374U]

If the average temperature is 2.73 Kelvin though, and there's an immeasurably large number of stars that have fusion reactions in them that range in Billions of Kelvin, means that there's a whole lot of stuff out there that doesn't have much energy at all.  And since they don't have enough heat/energy, the bulk of their EM radition will be with really long wavelength.

The thing is that, the colder something is, the less energy it does emit. The Stefan-Boltzmann law not only gives a correlation between energy emitted and temperature. It also provides a measure of the speed of that emission.

 

 

An important thing to consider is that clouds would also prevent additional energy from the sun as well.  White clouds are fantastic reflectors for visible light obviously.  I actually did comment in post 104 that energy absorbed in the atmosphere would also be radiated into space as well.  I guess the big thing is that currently some of it seems to get past (as we only have 75% effectiveness), which means of those photons, 100% of the energy is gonzo.  Now, if none of it escapes, at the very least we should be able to conclude that not all of it is gone.

Well, I'm not quite sure what you mean by that. But according to the Wikipedia, directly reflected energy only accounts for 30% of the total emitted, the amount reflected by clouds accounting for 20%. That means that 70% is actually IR radiation being emitted mostly by the atmosphere (since according to taks, only 25% gets through). So clouds, while important, are probably more a radiation leak outwards than a radiation mirror.

 

 

I know has air temperature rises, the amount of water vapour that can be absorbed in the air increases.  Is cloud formation a factor of absolute quantity of water vapour in the air, or is it also a factor of what percentage of the air has water vapour?

I'm not sure water vapour pressure is a factor by itself. Clouds aren't actually water vapour, they are condensed water. So, at higher temperatures, there's more vapour that condenses forming clouds, because the atmosphere can accept more water in vapour form. That's my opinion, but I'm not an expert by any means.

 

 

How else does the planet liberate heat outside of EM radiation?  I'm not so sure it really is that absurd either.  It would help make sense of the runaway greenhouse on Venus, a planet which is significantly hotter than Mercury (so it's not just distance to the Sun).

No, the planet liberates heat only in the form of EM radiation, to space. In a vacuum, there's no other way of transferring energy. However, heat is transferred from the surface and lower strates of the atmosphere by means of convection and cloud formation, which in turn is emitted both into space and back to the surface in the form of IR radiation.

 

As for Venus, you need to consider that its atmosphere is incredibly dense (90 times more massive than our own, again according to the wikipedia). It is also richer in CO2. Compared to Mercury that has no atmosphere to speak of, it's not so strange that Venus is much hotter.

 

 

I agree.  The discussion more evolved into discussing the plausibility of whether or not a runaway greenhouse could occur.

I'm clueless on the subject. Reading a bit on it, it seems unlikely, though, since Venus atmospheric conditions are completely different.

[213374U]

That link I posted indicated that heat = kinetic energy + potenetial energy = total energy.

Um, what link? The "Selective Surfaces" one? I can't find anything there regarding potential energy. At any rate, I'm not sure what potential energy you are referring to. Mechanical? Electrical? Chemical?

 

And, you can't determine a piece of matter's "total energy". You can only measure energy exchanges, but knowing exactly how much energy something has (considering all aspects) involves breaking a few principles.

 

 

Empty space wouldn't contribute to an average temperature rating, since there's nothing to hold the energy.

Of course, where there is nothing, it makes no sense to measure temperature. However, there are also empty spaces between the particles that make up gases, and we measure their temperature no problem. Now, if you take that to places where the gas density is incredibly low, such as interstellar space, it's easy to understand how average temperatures are so damn low.

 

 

I see your italicized name down there....hurry up

Yeah, I'm actually having to think this stuff through before posting. It's been a while since I made use of these stuff and I'm also having to look up a lot of data... damn memory.

[alanschu]

The thing is that, the colder something is, the less energy it does emit. The Stefan-Boltzmann law not only gives a correlation between energy emitted and temperature. It also provides a measure of the speed of that emission.

 

That would make sense. I'm not sure why this was brought up though.

 

Well, I'm not quite sure what you mean by that. But according to the Wikipedia, directly reflected energy only accounts for 30% of the total emitted, the amount reflected by clouds accounting for 20%. That means that 70% is actually IR radiation being emitted mostly by the atmosphere (since according to taks, only 25% gets through). So clouds, while important, are probably more a radiation leak outwards than a radiation mirror.

 

The cloud part was a reference to the fact the idea that warmer temperatures would cause an increase in water vapour (and hence clouds), which would help to reflect sunlight.

 

I suspect that if more clouds occurred, the amount of energy reflected would account for more than 30% (since most energy from the sun is in the visible spectrum, and given that clouds are white, they are reflecting in the entire visible spectrum). Though at the same time, water vapour is also a greenhouse gas so any bonus here would probably be nullified.

 

Interesting points about the clouds being emitters as well. Any idea what spectrum they would emit at, and what the density the particles of a cloud is compared to CO2? They obviously don't emit very well in the visible spectrum (since poor absorbers are poor emitters, and clouds reflect visible light quite well). Though if the CO2 is still above the clouds, does this provide any real benefit?

 

No, the planet liberates heat only in the form of EM radiation, to space. In a vacuum, there's no other way of transferring energy. However, heat is transferred from the surface and lower strates of the atmosphere by means of convection and cloud formation, which in turn is emitted both into space and back to the surface in the form of IR radiation.

 

At the same time, energy from the cloud formation and whatnot will still be transferred via conduction to other air molecules, though IIRC conduction among gases isn't as common.

 

As for Venus, you need to consider that its atmosphere is incredibly dense (90 times more massive than our own, again according to the wikipedia). It is also richer in CO2. Compared to Mercury that has no atmosphere to speak of, it's not so strange that Venus is much hotter.

 

Is this cause or effect though? A runaway greenhouse is supposed to result in extreme increases of CO2 into the atmosphere. If we're before and they are after, it would make sense that our atmosphere would be less dense. It isn't composed of nearly as much CO2. What would happen to our atmosphere if a runaway greenhouse did occur?

[alanschu]

Um, what link? The "Selective Surfaces" one? I can't find anything there regarding potential energy. At any rate, I'm not sure what potential energy you are referring to. Mechanical? Electrical? Chemical?

 

And, you can't determine a piece of matter's "total energy". You can only measure energy exchanges, but knowing exactly how much energy something has (considering all aspects) involves breaking a few principles.

 

Err, I posted the wrong link. Which would probably confuse people because my previous quote was from a different link.

 

Try this

 

 

Of course, where there is nothing, it makes no sense to measure temperature. However, there are also empty spaces between the particles that make up gases, and we measure their temperature no problem. Now, if you take that to places where the gas density is incredibly low, such as interstellar space, it's easy to understand how average temperatures are so damn low.

 

We do? I did not know that we could measure the empty spaces between particles, as I thought temperature was a measurement of the kinetic energy of particles.

 

http://www.answers.com/topic/temperature

 

A measure of the average kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale.

 

I don't understand how you could measure the energy/heat/temperature of a void.

 

A measure of the average kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale.

 

Me too. And apparently I still screw up as I post the wrong links.

 

 

EDIT: Going home now, so I'll be a while before next post.

Edited May 30, 2006 by alanschu

[213374U]

That would make sense.  I'm not sure why this was brought up though.

Well, I was trying to point out that it's not that everything that isn't a star or a really hot rock really has a very low energy. But matter with low energy (and thus low temperature) takes much longer to lose energy via radiation.

 

The 2,74K figure is somewhat inconsequential, I think, since there's a large part of the universe we can't see and many things that don't fit well into the present model (dark matter, for instance). So, while that temperature is probably deducted from observed irradiance, I'm not too convinced of any drawn conclusions from it.

 

 

I suspect that if more clouds occurred, the amount of energy reflected would account for more than 30% (since most energy from the sun is in the visible spectrum, and given that clouds are white, they are reflecting in the entire visible spectrum).  Though at the same time, water vapour is also a greenhouse gas so any bonus here would probably be nullified.

Nope, not nullified, since a part of the energy lost in water condensation does not get sent back to the surface. Think of it as a means of heat transport. Some of the heat from the surface is taken up to the clouds, where some is sent back to the surface, and some irradiated.

 

 

Interesting points about the clouds being emitters as well.  Any idea what spectrum they would emit at, and what the density the particles of a cloud is compared to CO2?  They obviously don't emit very well in the visible spectrum (since poor absorbers are poor emitters, and clouds reflect visible light quite well).  Though if the CO2 is still above the clouds, does this provide any real benefit?

Clouds can only emit in lower frequencies than visible light. Condensation is a thermodinamic process, and theferore energy lost is liberated in form of heat. It also doesn't matter if the CO2 is above the clouds, as a part of the IR energy absorbed and then irradiated back by the CO2 will always end up on the surface.

 

 

At the same time, energy from the cloud formation and whatnot will still be transferred via conduction to other air molecules, though IIRC conduction among gases isn't as common.

No, but convection is. Heated gas will ascend, until it cools down.

 

As for Venus, you need to consider that its atmosphere is incredibly dense (90 times more massive than our own, again according to the wikipedia). It is also richer in CO2. Compared to Mercury that has no atmosphere to speak of, it's not so strange that Venus is much hotter.

 

 

Is this cause or effect though?  A runaway greenhouse is supposed to result in extreme increases of CO2 into the atmosphere.  If we're before and they are after, it would make sense that our atmosphere would be less dense.  It isn't composed of nearly as much CO2.  What would happen to our atmosphere if a runaway greenhouse did occur?

That's a valid point, I guess. At this point it's all speculation, though. Venus is much closer to the sun, too. A runaway greenhouse is a rather catastrophic atmospheric process, which seems unlikely if we consider environmental conditions in past periods, when it was much hotter. Something of greater impact than human influence would have to occur for the system to destabilize, I think.

[213374U]

Err, I posted the wrong link.  Which would probably confuse people because my previous quote was from a different link.

 

Try this

Oh, right. Well, that's not what I was taught. Chemical potential energy is a form of energy alright, but it has nothing to do with the current heat a piece of matter posesses at a given time, even though it can affect it if chemical reactions do appear.

 

We do?  I did not know that we could measure the empty spaces between particles, as I thought temperature was a measurement of the kinetic energy of particles.

 

http://www.answers.com/topic/temperature

 

A measure of the average kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale.

 

I don't understand how you could measure the energy/heat/temperature of a void.

Um, no. You don't measure the temperature of the empty spaces between particles. You measure the gas as a whole, regardless of the distance between its constituent particles.

 

 

A measure of the average kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale.

 

Me too. And apparently I still screw up as I post the wrong links.

You too... what?

 

 

EDIT: Going home now, so I'll be a while before next post.

I'm calling it a night myself... its 3:20 AM over here.

[alanschu]

Well, I was trying to point out that it's not that everything that isn't a star or a really hot rock really has a very low energy. But matter with low energy (and thus low temperature) takes much longer to lose energy via radiation.

 

At the same time then, wouldn't it have an even lesser impact on the state of our planet as it doesn't emit radiation at a fast enough rate? (since taks seemed to be indicating that sources of energy outside of our sun may be significant contributors).

 

Nope, not nullified, since a part of the energy lost in water condensation does not get sent back to the surface. Think of it as a means of heat transport. Some of the heat from the surface is taken up to the clouds, where some is sent back to the surface, and some irradiated.

 

I was referring to any benefit of having additional clouds in the sky, and resulting in an increase in light reflection away from the planet from the Sun. While increased clouds may reduce the energy from the sun, the increase in water vapour required for an increase in cloud coverage would also trap energy in, as water vapour contributes to the greenhouse effect.

 

Clouds can only emit in lower frequencies than visible light. Condensation is a thermodinamic process, and theferore energy lost is liberated in form of heat. It also doesn't matter if the CO2 is above the clouds, as a part of the IR energy absorbed and then irradiated back by the CO2 will always end up on the surface.

 

The energy loss would be more pronounced if it was above the CO2, since energy radiated from clouds towards space would not get reabsorbed by the CO2 (assuming it radiates in the low infrared).

 

No, but convection is. Heated gas will ascend, until it cools down.

 

Absolutely. You had already mentioned it so I decided to only comment on conduction, which at first glance seems insignificant given the nature of convection.

 

That's a valid point, I guess. At this point it's all speculation, though. Venus is much closer to the sun, too. A runaway greenhouse is a rather catastrophic atmospheric process, which seems unlikely if we consider environmental conditions in past periods, when it was much hotter. Something of greater impact than human influence would have to occur for the system to destabilize, I think.

 

No argument here.

 

Um, no. You don't measure the temperature of the empty spaces between particles. You measure the gas as a whole, regardless of the distance between its constituent particles.

 

I don't recall temperature being dependant on volume though, but rather on the average kinetic energy of the particles. I definitely agree that you measure the gas as whole (since it's an average), but as a whole of its matter (which excludes the void between molecules).

 

naturally being the equation for kinetic energy.

 

Wiki had an interesting discussion about it here.

 

Temperature of the vacuum

The temperature of an object is proportional to the average kinetic energy of the molecules in it. In a pure vacuum, there are no molecules. There is nothing to measure the kinetic energy of, and temperature is undefined. If a thermometer were placed in a vacuum, the reading would be a measurement of the internal temperature of the thermometer, not of the vacuum which surrounds it.

 

All objects emit black body radiation. Over time, a thermometer in a pure vacuum will radiate away thermal energy, decreasing in temperature indefinitely until it reaches the zero-point energy limit defined by it

Edited May 30, 2006 by alanschu

[thepixiesrock]

In other news,scientists say that the hole in BattleWookiee's head will never fully disappear.

[alanschu]

Hahaha.

 

Go away, this is actually an interesting discussion

[thepixiesrock]

I know that, it's not like I haven't been following along or anyhting, and am now rushing to read the last two pages to keep up...

[alanschu]

In other news, if the Ozone hole goes away, wouldn't that result in a decrease of UV radiation and as a result, a decrease in the amount of energy absorbed?

[Colrom]

So Taks, are you published on this matter?

no, but it doesn't take publication on this matter to understand the science.

 

What publications have you read recently which support your contention that this global warming stuff is still under debate by scientists?

holy cow, i suggest you look up the work McIntyre and McKittrick or Roger Pielke Sr. and the list goes on and on. just because al gore runs at the mouth doesn't mean it's "settled".

 

I thought the debate was over among the reputable scientists and it was agreed that civilization is having a significant and decisive impact on global warming.

<{POST_SNAPBACK}>

according to al gore, yes. according to the scientific method. no.

 

taks

<{POST_SNAPBACK}>

 

I had in mind something like:

 

Article Title: CLIMATE RESPONSE TO INCREASING LEVELS OF GREENHOUSE GASES AND SULFATE AEROSOLS

Authors: Mitchell, JFB, Johns, TC, Gregory, JM, Tett, SFB

Journal: NATURE

Volume: 376

Page: 501-504

Year: 1995

 

Here is some text from a Special Topics interview [http://www.esi-topics.com/gwarm/interviews/DrSimonTett.html] of Dr. Tett:

 

"Q: Your most-cited paper, "Climate response to increasing levels of greenhouse gases and sulphate aerosols," has had a huge impact. What's this paper all about?

 

A: All attempts at detecting and attributing climate change signals need a reliable observed data set and simulations with mechanisms that drive climate change included. In a nutshell, this paper is important because it was the first study to investigate the effect of sulphate aerosols in a general circulation model of the climate system. The general circulation model we employed had 20 layers in the ocean and 19 for the atmosphere. The experiments simulate the climate back to 1860 (which is when the global records of surface temperature became reliable), and they are projected forward to 2050. We found that the greenhouse-gas forcing increased slowly from 1860-1960, but then accelerated markedly. After 1970 our model with greenhouse gases alone begins to depart significantly from the observations. However, when we included sulphate aerosols, which have a cooling effect, the model agreed with the data from the 1930s and onwards. The rapid warming that has taken place since 1970 is, according to the model, attributable to a heating effect from greenhouse gases and a cooling effect from sulphate aerosols. Fundamentally we showed that climate models cannot simulate the observations unless forcing factors additional to greenhouse gases are included.

 

Q: At the end of the paper you mention the need to consider tropospheric ozone in the models.

 

A: Yes, and that was the next step: feeding in the ozone, which enabled us to get the stratospheric cooling and tropospheric warming correct. In 1996 Ben Santer, myself, and other colleagues published a paper ("A search for human influences on the thermal structure of the atmosphere," B. D. Santer, et al., Nature 382 [6586]: 39-45, 4 July 1996) that was to win us NOAA's "Best Scientific Paper" award in 1998. But despite our successes I was still feeling that we hadn't got to the bottom of whether or not natural forcing could explain everything. We ran simulations that included the effects of volcanic aerosols and changes in solar irradiance. We published those findings in papers in 1999 ("Causes of twentieth century temperature change near the earth's surface," Tett et al., Nature 399 [6736]: 569-72, 10 June 1999) and 2001 ("Attribution of twentieth century temperature change to natural and anthropogenic causes," Stott et al., Clim. Dyn. 17 [1]: 1-21, January 2001). Read a Special Topics interview with Climate Dynamics.

 

Q: What's your current thinking on the causes of climate change?

 

A: We've got a paper in press with the Journal of Geophysical Research on the natural and anthropogenic contributions to 20th century temperature change. This describes experiments with the third-generation Hadley Centre Coupled Model (HadCM3) . We find that the warming which took place early in the 20th century can be accounted for through natural variability. That warming is best explained by changes in solar brightness, a scarcity of explosive volcanoes, and internal climate variability. But in the second half of the 20th century there's no way that nature alone can account for the warming, and human activity is the major driving force.

 

Q: How does your work relate to the Reports produced by the Intergovernmental Panel on Climate Change?

 

A: In the Second Assessment Report, I was a contributing author to three of the chapters dealing with the science of climate change. That Report had quite a controversial closing statement in chapter 8, where we said, "the balance of evidence suggests a discernible human influence upon global climate." I was a contributing author to chapter 12 of the third assessment report, which made a stronger statement on the detection of climate change."

 

By the way, I have seen Al Gore's slide presentation. It's very impressive.

[taks]

It's very impressive.

<{POST_SNAPBACK}>

it is disingenuous at best. what is more impressive is what he leaves out (because it makes him a: look bad and b: destroys most of his claims). if you'd like to see a rebuttal to mr. environmentalist why not try Dr. Spencer's open letter.

 

most of what we've been discussing, btw, is unrelated to whether or not you want to say the science is "settled" or not. mostly basic chemistry, actually. and, for alanschu's benefit, at the bottom of this page, there's a nifty graphic on which wavelenghts CO2 absorbs. there's also a better explanation of the absorption process in the text that accompanies the picture (at this moment, i have not read it in detail... my information was originally from other, varied, sources including wiki).

 

taks