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Water Vapor Effect On Climate Change

02/19/2013 8:05 AM

I keep hearing about how water vapor ties into climate change, from both sides.

http://www.sciscoop.com/climate-change-evidence.html

This morning I started wondering how humans affect water vapor content in the atmosphere, and it seems like it might be significant.

It occured to me, that all around the planet, regardless of fuel used, including nuclear, almost all of our power comes from steam driven turbines, which release large amounts of water vapor into the atmosphere, above and beyond natural evaporation.

In fact, the water content in ethanol is also released as water vapor when we burn it.

http://en.wikipedia.org/wiki/Ethanol_fuel#Hydrous_ethanol_corrosion

Here's my question(s):

Since it doesn't seem to ever get any mention, is the human output of water vapor itself, completely insignificant to the conversation?

Wouldn't human introduced water vapor, (in the form of steam), create areas of air that would be more saturated than would be the case with natural evaporation, and therefore influence weather patterns?

Has anyone studied it?

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#1

Re: Water Vapor Effect On Climate Change

02/19/2013 8:19 AM

I'm probably just missing something and getting myself confused.

Everybody seems to agree that water vapor plays a significant role in climate change/warming, but at the same time, we hear about what a wonderful fuel hydrogen would be, because the primary biproduct would be harmless water vapor.

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#2

Re: Water Vapor Effect On Climate Change

02/19/2013 8:19 AM

While water vapor is considered to be a more efficient greenhouse gas, the rate and magnitude of anthropogenic change is very much smaller than the amount of CO2 changes over the same time period.

For that reason water vapor is not considered a significant actor on the equation of anthropogenic climate change.

However, there are studies that seem to show that water vapor concentrations are now just starting to show an upward trend where it has been fairly steady state previously.

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#3
In reply to #2

Re: Water Vapor Effect On Climate Change

02/19/2013 8:36 AM

I just found a NASA link, that shows that they are just now getting to the point that water vapor can be accurately measured, and it is going up.

http://www.nasa.gov/topics/earth/features/vapor_warming.html

Everything I can find seems to be looking at the temp, water vapor, CO2 relationship. Maybe I'm completely off the wall here, but I don't understand why our contribution to water vapor isn't considered.

For example, I can't find any data on how many tons or gallons, (however they would measure it), of water are pumped into the atmosphere by human activity.

Interesting.... there is a link at the bottom of the page about runaway water warming the world, and it's been removed.

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#6
In reply to #3

Re: Water Vapor Effect On Climate Change

02/19/2013 9:29 AM

"...but I don't understand why our contribution to water vapor isn't considered."

As I said, the general consensus is/was that water vapor concentrations have not changed much over the last several centuries and therefore have not been considered a factor.

However, CO2 concentrations have changed and indicates a strong(er) correlation between CO2 levels and surface temperatures; whereas water vapor does not.

As you pointed out, that thinking has been evolving over the last 20 years and water vapor is believed to be a more significant player than first thought.

The other possibility is that water vapor trends might be more reactionary than an actual initial causative agent. This trend would would act as an amplifier.

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#4

Re: Water Vapor Effect On Climate Change

02/19/2013 8:55 AM

Maybe your on to something with this. The graph of climate warming does pretty much match world population growth.

The average person expels about a liter of water a day. So that's 7 million kiloliter or 1.8 billion gallons. A small lake! It maybe be a important contributing factor. But no one going to say it's the real cause. What they going to do ration breathing.

Imagine if we all hold our breath for an hour it might snow in the Sahara.

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#5
In reply to #4

Re: Water Vapor Effect On Climate Change

02/19/2013 9:08 AM

As usual, these queries lead me to some wild stuff.

I don't remember hearing anything about this, but I'm not the first one to think of it:

http://www.ecoenquirer.com/EPA-water-vapor.htm

EPA Director of the Department of Pollutant Decrees, Ray Donaldson, said, "Back before carbon dioxide was dangerous, we simply assumed that water vapor was also benign. But all reputable scientists now agree that the increased water vapor content of the atmosphere from such sources as burning of fuels and power plant cooling towers will also enhance the greenhouse effect, leading to potentially catastrophic warming."

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#40
In reply to #5

Re: Water Vapor Effect On Climate Change

02/21/2013 7:02 PM

read the disclaimer of the Ecoenquirer! You be surprised to find yourself in a satirical fun environment with this one!

Note: this is not to be taken as general statement about my opinion on this! Just this link is fun! We had that yesterday but I am too lazy to pull out the link!

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#7

Re: Water Vapor Effect On Climate Change

02/19/2013 2:07 PM

Since it doesn't seem to ever get any mention, is the human output of water vapor itself, completely insignificant to the conversation?


Water vapor is mentioned all the time in discussion of global warming and climate change. Virtually all the models take into account the effects of water vapor, which is a potent GHG. And no, the effect is not insignificant.


When you burn a gallon of gasoline, you emit about 19-20 lbs of CO2 and about 7 lbs of water vapor. Any hydrocarbon, (and of course hydrogen) emits water vapor when burned.


From the Wikipedia article on climate change feedback loops:

  • If the atmospheres are warmed, the saturation vapor pressure increases, and the amount of water vapor in the atmosphere will tend to increase. Since water vapor is a greenhouse gas, the increase in water vapor content makes the atmosphere warm further; this warming causes the atmosphere to hold still more water vapor (a positive feedback), and so on until other processes stop the feedback loop. The result is a much larger greenhouse effect than that due to CO2 alone. Although this feedback process causes an increase in the absolute moisture content of the air, the relative humidity stays nearly constant or even decreases slightly because the air is warmer.[45] Climate models incorporate this feedback. Water vapor feedback is strongly positive, with most evidence supporting a magnitude of 1.5 to 2.0 W/m2/K, sufficient to roughly double the warming that would otherwise occur.[59] Considered a faster feedback mechanism.[49]

If other things remained constant (but they do not) then more water vapor would lead to more clouds, and more clouds would lead to higher earth albedo, which would (by itself) have a cooling effect. But the effects are much more complex than can be described in a post or a wikipedia article. The IPCC reports offer some summaries, and the Wikipedia articles offer links.

But the short answer is that the effect of water vapor has been included in the models for a few decades.

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#8
In reply to #7

Re: Water Vapor Effect On Climate Change

02/19/2013 4:52 PM

I agree that it's been mentioned in the equation, but not human contribution to vapor levels. I guess we're back to....there's really no way to tell, because all water vapor looks the same.

This site puts human contribution at .001%, but I don't know how they reached that number.

http://www.geocraft.com/WVFossils/greenhouse_data.html

I also don't know why I start asking myself these questions; I should get back to GMO food, which I will soon.

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#9

Re: Water Vapor Effect On Climate Change

02/19/2013 6:31 PM

A while back Wasn't someone whining about why we humans as a collective whole cant shoot giant jets of water up into the air to increase the water vapor levels to increase them so that it would rain more?

That being said I have read on a number of scientific studies that the typical water vapor replenishment cycle globally is around 7 - 10 days. That being that if 100% of the water vapor in the atmosphere was taken away it would only take around 7 - 10 days for it ti fully return.

For rough approximations for each of the 7 billion or so of us around 28,000 - 35,000 gallons of water naturally evaporate and re condense every 24 hours which when weighted against our world average human consumption of something like 10 - 30 gallons per person per day we really don't add enough to the overall volumes being cycled to make any difference.

I would post links but all of these number are from past links I have posted in other threads here relating to this sort of stuff so am not considering any of this new info here.

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#10
In reply to #9

Re: Water Vapor Effect On Climate Change

02/19/2013 6:48 PM

Yeah, I wasn't looking to get into another climate change debate. Just human contribution to water vapor.

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#11

Re: Water Vapor Effect On Climate Change

02/19/2013 8:59 PM

You're asking a good question, but it's not an easy one to answer. Not because the answer is unknown, but because it's complex. Any attempt to simplify it is likely to be misleading. One thing I can say, with assurance, is that climate scientists are well aware of the complexities relating to atmospheric water vapor. They work hard to get it right in their models.

To a first approximation, direct human output of water vapor, in the form of evaporation from cooling towers or the water vapor content of combustion exhaust, is indeed insignificant. Water vapor doesn't accumulate in the atmosphere the way CO2 does. There's a constant turnover from evaporation in one area, and precipitation in another. The flux from humans' direct output of water vapor is six to eight orders of magnitude down from this ongoing natural flux.

That said, the indirect effects of human activities on atmospheric water vapor and climate can be quite significant. Humans can and have left deserts where there were once forests or rich savannas. We have also, more recently, managed to transform some desert regions into productive farmland. Those activities change the distribution of water vapor within the atmosphere and affect temperature and precipitation over large areas. They certainly affect local micro-climates; how they affect global temperatures overall is hard to say.

One point worth making is in response to a favored meme of the denialist community: the idea that since water vapor is both much more potent as a greenhouse gas than CO2 (molecule per molecule) and vastly more abundant in the atmosphere, all the fuss about atmospheric CO2 levels must be bunk! Not true. Not true at all!

CO2 is an essential "thermostat" for global climate. In the lower atmosphere, it's insignificant compared to water vapor. But in the upper atmosphere, the water vapor has frozen out and CO2 dominates. If there were no CO2 in the atmosphere to provide a "signal", the air would slowly become colder and drier. The end point, after a few hundred thousand years of cooling, would be a return to the "snowball earth" that has existed at times in the past.

One of the mysteries of paleoclimate research is how the cold dry atmosphere of a snowball earth managed to reacquire enough CO2 (or methane!) to pull the earth out of its iceball trap. Massive volcanic eruptions are one possibility. Another, paradoxically, is slow geothermal warming of the deep ocean waters under the insulating cover of surface ice. Huge quantities of methane liberated from icy clathrates in the warming waters could have broken through the ice and done the trick.

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#12

Re: Water Vapor Effect On Climate Change

02/20/2013 12:26 AM

No one seems to have mentioned that water vapor reaches an equlibrium in the atmosphere that's related to temperature.

So, if Humans put more into the atmosphere then it rains out. So no long term green house effect.

However, a small increase in the CO2 level causes a small increase in global temperature so more water vapor can be held in the atmosphere where it has an additional greenhouse effect. It's a feedback mechanism.

This is a well understood phenomena.

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#13
In reply to #12

Re: Water Vapor Effect On Climate Change

02/20/2013 3:06 AM

That gets into one of the complexities I was trying to avoid. Your answer is correct, and merits a GA vote, with the caveat that "equilibrium" must be interpreted very loosely.

It's certainly true that the amount of water vapor that can be carried depends on air temperature. For the most part, adding water vapor to the air at one point does just increase precipitation a few days later somewhere down wind. Still, it's a stretch to say that water vapor ever reaches an equilibrium. Humidity is rarely 100%, and when it is, it's temporary.

One of the most basic facts about the atmosphere is that it's in a constant state of disequilibrium. Thermal energy from the sun, in the form of visible and near-infrared light, passes mostly unhindered through the atmosphere, to be deposited at the surface; a portion of it is re-radiated from the surface, but a lot of it warms the air and then re-radiates from higher in the atmosphere. That's what the greenhouse effect is all about; it drives convection and is the root source of all weather.

Portions of the climate system are bi-stable with respect to water vapor. The Amazon basin is an example. It's hot, wet, and humid now, and has been for a long time. But most of the rain that falls in the afternoon evaporated from a nearby region in the morning or the day before. The whole basin amounts to a standing wave of high temperature and humidity, stabilized by transpiration from leaves in the rain forest. If deforestation proceeds too far, and too many trees are replaced by pastures for cattle grazing, the whole system could dry out. There would be much less rainfall, because there would be much less evaporation, and with less rainfall, there would be less water to evaporate in the first place.

Vegetation and large-scale changes in land use are major factors in shaping climate, and have to be considered in advanced climate models.

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#16
In reply to #12

Re: Water Vapor Effect On Climate Change

02/20/2013 6:15 AM

I was about to make that point when I read your post. It's not at all clear not (to me anyway) that the amount humans put into the atmosphere has any noticeable effect.

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#14

Re: Water Vapor Effect On Climate Change

02/20/2013 4:21 AM

So if water vapor is such a potent greenhouse gas, does that suggest that a shift from crude oil based fuels to biofuels, would accelerate AGW?

.

Both a gallon of Fossil fuel and gallon of biofuel would both be adding about the same amount of water vapor to the air when burnt.

The plants grown to make the biofuel certainly transpire far more than that into the air while they are growing.

.

Given the view that water vapor is a potent green house gas, wouldn't expanding agriculture enough to meaningfully offset crude oil use, be likely to accelerate AGW, the very thing that motivates such a shift?

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#15
In reply to #14

Re: Water Vapor Effect On Climate Change

02/20/2013 5:40 AM

See #11. Water vapor dominates at lower elevations in the atmosphere, but CO2 dominates in the upper atmosphere. CO2 serves as the "thermostat" for the atmosphere. It strongly influences the temperature profile in the cold upper atmosphere, where there is virtually no water vapor. The temperature profile in the lower atmosphere follows from that in the upper atmosphere, according to the adiabatic lapse rate. The latter is about 10 C per kilometer; a global warming of 1 C corresponds to an upward shift of only 100m in the mean temperature profile.

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#18
In reply to #15

Re: Water Vapor Effect On Climate Change

02/20/2013 6:54 AM

'...Water vapor dominates at lower elevations in the atmosphere, but CO2 dominates in the upper atmosphere. CO2 serves as the "thermostat" for the atmosphere.....'

.

It is a little weird to hear that water vapor is a much more potent greenhouse gas than CO2 but then be assured that because water vapor does not reach the upper atmosphere in large amounts that its concentration doesn't really matter that much.

.

From your statement, it doesn't sound like water vapor is dominating the lower atmosphere, it sounds like you are saying CO2 from the upper atmosphere is dominating the lower atmosphere.

.

I realize it is probably far to black and white to suggest that water vapor either is or isn't a potent greenhouse gas, but it seems reasonable to put it in a different category. If it doesn't factor the same as other greenhouse gasses, maybe we should call it a greenhelper gas...or a sprout gas or something.

.

.

This next part of what you wrote is causing some confusion for me:

'...The temperature profile in the lower atmosphere follows from that in the upper atmosphere, according to the adiabatic lapse rate....'

.

I don't see that in the limited data I have had an opportunity to review.

Furthermore, it seems that if greenhouse gasses were causing more heat to be retained near the surface, that just the opposite would occur: temperatures in the upper atmosphere would be lower since less heat is being lost from below.

Which is basically in line with observations of a cooling stratosphere and warming ground level atmosphere. It also seems to be an opinion popular with NASA:

'...Scientists theorize that there may be a multi-decadal trend in solar output, though if one exists, it has not been observed as yet. Even if the Sun were getting brighter, however, the pattern of warming observed on Earth since 1950 does not match the type of warming the Sun alone would cause. When the Sun's energy is at its peak (solar maxima), temperatures in both the lower atmosphere (troposphere) and the upper atmosphere (stratosphere) become warmer. Instead, observations show the pattern expected from greenhouse gas effects: Earth's surface and troposphere have warmed, but the stratosphere has cooled.

Satellite measurements show warming in the troposphere (lower atmosphere, green line) but cooling in the stratosphere (upper atmosphere, red line). This vertical pattern is consistent with global warming due to increasing greenhouse gases, but inconsistent with warming from natural causes. (Graph by Robert Simmon, based on data from Remote Sensing Systems, sponsored by the NOAA Climate and Global Change Program.)

The stratosphere gets warmer during solar maxima because the ozone layer absorbs ultraviolet light; more ultraviolet light during solar maxima means warmer temperatures. Ozone depletion explains the biggest part of the cooling of the stratosphere over recent decades, but it can't account for all of it. Increased concentrations of carbon dioxide in the troposphere and stratosphere together contribute to cooling in the stratosphere....'

.

Having had some decent discussions with you in the past, I am of the opinion you generally do know what you are talking about, and tend to make sound well supported assertions.

That strongly suggests I have either misunderstood your previous comment above or have misunderstood the what I have gathered from other sources like the NASA quote above.

Do I seem to be misconstruing your previous statement if I find it at odds with this quote from the NASA site?

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#26
In reply to #18

Re: Water Vapor Effect On Climate Change

02/20/2013 6:18 PM

I'm glad you found that statement at the NASA site, and I'm glad that they're making it. One of the things that has bothered me, even in the IPCC reports and climate science literature, is their tendency to reduce the warming effects of atmospheric CO2 to an equivalent "radiative forcing". It's not that the calculations they use to derive the numbers are wrong, but by discussing AGW factors only in terms of radiative forcings, they leave the impression that the warming effects of CO2 are identical to the effects of increased solar radiation. They're not identical, and that NASA statement you quoted is the first one I've seen on a popular web site ("popular" as in "intended for the general populace") to make that clear.

Water vapor is indeed a different sort of greenhouse gas than CO2 or methane. It's different because it's condensible; its concentration both affects and is affected by temperature. Any time you have a positive feedback loop, the immediate question you want to ask is "what's the loop gain?" If the gain is greater than unity, you have runaway feedback. We know for sure that the loop gain for the water vapor - temperature feedback loop is not greater than unity, because if it were we wouldn't be around to worry about it.

When the loop gain is less than unity, what you have is an amplifier. Atmospheric water vapor is an amplifier -- and a rather strong one -- for weaker warming signals from other GHGs outside the loop. The water vapor system itself has no natural "set point" that it wants to hold. In the absence of other non-condensible GHGs, it would spiral downward until it hit bottom at the snowball earth scenario -- the average temperature that the world would have if there were no greenhouse warming at all. Furthermore, an increase in solar radiation equal to the calculated "radiative forcing" of atmospheric CO2 would have little effect. It would raise the average surface temperature by a small amount, but it wouldn't provide the persistent warming signal needed to drive the amplifier away from its resting state.

The reason that increased CO2 levels in the upper atmosphere cause warming in the troposphere is that the higher concentration of CO2 creates an "insulating blanket" that blocks portions of the thermal IR spectrum for outbound radiation from the upper troposphere. In order to lose its quota of outgoing thermal energy through the remaining windows, temperatures in the upper troposphere must increase. The reason that increased CO2 reduces temperatures in the coldest layer of the stratosphere is that the increased CO2 below that layer reduces the energy in the absorption bandwidths arriving from below, while increasing the radiation in those bandwidths to the cold of space above.

That's enough for one post. Maybe we can discuss the adiabatic lapse rate and how it figures into all this another time. Cheers.

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#27
In reply to #26

Re: Water Vapor Effect On Climate Change

02/20/2013 8:19 PM

Another dumb question, but what keeps CO2 aloft? I thought it was heavier than air, and should settle to the surface.

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#32
In reply to #27

Re: Water Vapor Effect On Climate Change

02/20/2013 11:54 PM

Pure CO2 is heavier than air, and a stream of pure CO2 would flow downhill for some distance, until it became thoroughly mixed with the air. But it would mix. One of the defining properties of gases is that they are all infinitely miscible with one another. Two separate volumes of pure gas, inserted into a closed chamber, will diffuse into one another until each fills the whole volume of the container.

What sustains the partial pressure of CO2 at high altitude is simply the partial pressure of CO2 at lower altitudes. The concentration of CO2, in parts per million by volume, is no greater at high altitude than it is a low altitude. The concentration of water vapor, by contrast, falls off sharply at high altitudes. That's simply because the air is very cold at high altitudes, and the water vapor virtually all has condensed out.

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#36
In reply to #32

Re: Water Vapor Effect On Climate Change

02/21/2013 5:54 AM
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#33
In reply to #26

Re: Water Vapor Effect On Climate Change

02/21/2013 1:49 AM

'....The reason that increased CO2 levels in the upper atmosphere cause warming in the troposphere is that the higher concentration of CO2 creates an "insulating blanket" that blocks portions of the thermal IR spectrum for outbound radiation from the upper troposphere. In order to lose its quota of outgoing thermal energy through the remaining windows, temperatures in the upper troposphere must increase. The reason that increased CO2 reduces temperatures in the coldest layer of the stratosphere is that the increased CO2 below that layer reduces the energy in the absorption bandwidths arriving from below, while increasing the radiation in those bandwidths to the cold of space above.....'

.

Thank you for that. This is the FIRST technical explanation of a portion of the proposed mechanism that has not included some blatant effrontery to the laws of thermo.

.

I appreciate your response. GA

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#17

Re: Water Vapor Effect On Climate Change

02/20/2013 6:52 AM

Okay, how about if we leave out AGW, and consider short term weather patterns?

Rainfall, hurricanes, snow storms, etc.

For example: Living on the east coast and having air movement from west to east, I would think that, (due to human activity), the air that reaches NC is a lot wetter than it would be without introduced water vapor, and it seems like it would have an effect on our weather patterns.

Now to swing it back into AGW......we are told that AGW will cause bigger hurricanes, snowstorms, and other weather anomalies; but what if these are being primarily caused by human introduced water vapor?

We know that water vapor plays a big role in weather, when we see the big snowstorms that hit the eastern Great Lakes area, due to lake effect moisture.

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#19

Re: Water Vapor Effect On Climate Change

02/20/2013 7:40 AM

I'm just throwing this out. It's a map of existing US power plants. It seems to me that areas of concentrated, (man made), water vapor could impact local weather patterns. Rainfall, snowfall, possible frequency and strength of tornadoes, etc.

I'm not jumping to conclusions, but it's notable that tornadoes feed on warm, moist air, and there happens to be a string of plants in the mid west.

http://www.universetoday.com/71983/how-are-tornadoes-formed/

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#22
In reply to #19

Re: Water Vapor Effect On Climate Change

02/20/2013 11:13 AM

It is reasonable to assume that all the outputs from large powerplants (water vapor and particulates) and other large sources have an affect on local weather, but not on global climate. The particulates can act as cloud "seeds" (providing condensation sites) helping to trigger cloud formation. I believe that I have seen this sort of activity downstream from powerplants when flying around in small planes, but I have never seen precipitation resulting from the effect -- but perhaps with enough power plants...

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#31
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Re: Water Vapor Effect On Climate Change

02/20/2013 11:39 PM

'...It is reasonable to assume that all the outputs from large powerplants (water vapor and particulates) and other large sources have an affect on local weather, but not on global climate.....'

.

er....What?

.

How can a ubiquitous process affecting local weather all over the world, somehow NOT affect global climate???

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#37
In reply to #31

Re: Water Vapor Effect On Climate Change

02/21/2013 6:25 AM

I think it may be fairly insignificant when compared to natural evaporation; on the other hand, whenever we get odd weather anomalies, large hurricanes, freak snowstorms, floods, etc., we are told that it is all evidence of global climate change.

I think it is disingenuous to not consider large masses of warm, moist, (man made), air, that could have a major impact on localized weather events.

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#39
In reply to #31

Re: Water Vapor Effect On Climate Change

02/21/2013 3:16 PM

How can a ubiquitous process affecting local weather all over the world, somehow NOT affect global climate???


Good question. I probably should have italicized assume. You can see the local weather effect of even a fairly small lake (such as a Finger Lake in NY) when flying around on a sunny day. Larger lakes (like the Great Lakes) affect local (and relatively local) weather in a more pronounced and broader way (such as "lake effect" weather in upstate New York, which extends across much of western New York). A power plant can have an apparent affect similar to that of a small lake.

When I wrote (unclearly) "all" the outputs from large power plants the "all" meant both water vapor and particulates, the latter being generally necessary for cloud formation. I didn't mean the output from all large power plants, but rather all the output from a single large plant, or group of closely spaced plants.

Getting back to "assume": Yes, these plants can affect local weather, just as lakes do. That is a reasonable assumption, because you can see that clouds are formed near both. But one cannot assume that the local weather then affects global climate, at least in any way that is easily predicted. In other words, a lot of rain from local power plants does not make the planet warmer or cooler. The total water vapor from power plants is just too small to have a measurable effect on global temperatures globally.

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#42
In reply to #39

Re: Water Vapor Effect On Climate Change

02/21/2013 8:32 PM

Rereading what I wrote, I should have thought about it a little longer.

.

The two statements are not mutually exclusive. Agreement between the statements is possible if just the sign of the effect varies regularly.

.

Even if the sum the magnitudes of the local effects were large, the total (global) effect still has the possibility of being negligible if in some places the effect is negative while in others it is positive.

.

Sorry about that.

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#43
In reply to #31

Re: Water Vapor Effect On Climate Change

02/21/2013 11:02 PM

more localized rain in areas of concentrated power production probably.

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#23
In reply to #19

Re: Water Vapor Effect On Climate Change

02/20/2013 1:37 PM

Like saying that Tornados hit Trailer Parks, with White reflective roofs with a greater frequency than other structures???

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#20

Re: Water Vapor Effect On Climate Change

02/20/2013 7:57 AM

Here we go. Doesn't look like a big deal in relation to AGW, but they do mention increased local concentrations:

http://www.netl.doe.gov/energy-analyses/pubs/Water%20vapor%20impacts_final2.pdf

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#21

Re: Water Vapor Effect On Climate Change

02/20/2013 10:41 AM

How about the vapor trails from jet planes that turn clear skies to cloudy ones? I read somewhere that a guy studied the days after 9/11/2001 when planes were not allowed to fly in the US. He noticed a slight drop in temperature, thought that is not conclusive.

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#24
In reply to #21

Re: Water Vapor Effect On Climate Change

02/20/2013 3:04 PM

Actually, just the opposite. Lack of contrails produced a slight warming effect.

http://www.activistpost.com/2012/07/artificial-weather-revealed-by-post-9.html

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#25
In reply to #21

Re: Water Vapor Effect On Climate Change

02/20/2013 5:03 PM

I found a link about those, but didn't post it. I'll see if I can find it.

Here's what I read:

http://phys.org/news/2011-03-airplane-contrails-worse-co2-emissions.html

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#28
In reply to #25

Re: Water Vapor Effect On Climate Change

02/20/2013 9:47 PM

Interesting. Actual measurements when no contrails are present indicate that contrails lower temperatures. A NASA computer model indicates that contrails (which they assume are the same as cirrus clouds) not only cause warming, but can account for all the global warming that has occurred since aviation became prevalent, and is a much bigger effect than CO2 emissions. ( kramarat article above)

Then NASA flip flops, and says that maybe contrails are different.

Is it any wonder the average person has trouble with "science"?

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#30
In reply to #28

Re: Water Vapor Effect On Climate Change

02/20/2013 11:36 PM

No, NASA hasn't flipped on anything. You've been visiting junk web sites. The effects of very high altitude clouds, cirrus or contrails, has always been understood to be cooling. They reflect incoming sunlight, increasing earth's albedo. And because they're so cold, they don't significantly radiate outbound heat back to the ground.

Low altitude clouds, OTOH, also reflect incoming sunlight, but being much warmer, they radiate much more heat back to the ground. The net effect is enhanced warming. So high clouds, cooling, low clouds warming. What climate scientists have had trouble nailing down is just where the crossover falls at different latitudes and seasons.

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#35
In reply to #30

Re: Water Vapor Effect On Climate Change

02/21/2013 3:22 AM

Well, it seems I will have to eat at least some of my words here. I wrote what made sense to me and what I thought was the scientific consensus as well, but I didn't confirm it before I shot my mouth off (so to speak).

In belatedly researching the issue, I've found multiple articles that assert that cirrus clouds have a net warming effect. In fact, one of them (http://www.atmosphere.mpg.de/enid/Information_2/Cirrus_clouds_5sw.html) suggests that cirrus "are maybe the only clouds for which it is nearly secured, that their warming influence on the atmosphere is stronger than their cooling influence." Since contrails form at roughly the same altitude as cirrus clouds, it's quite possible that there was an automatic assumption that they would also produce a net warming effect. Subsequent research has apparently called that assumption into question.

The reason that cirrus clouds are believed to have a net warming effect is that they don't, in fact, reflect much of the incoming sunlight back to space. They scatter light, which makes them appear white from the ground, but the scattering, it seems, is mostly confined to a narrow forward cone. As little as 10% ends up as backscatter. At the same time, they are apparently fairly effective in reflecting outgoing thermal radiation back toward the ground.

That doesn't entirely make sense to me; if the ice particles are too small to produce wide angle scattering of visible light, they should be all but transparent at thermal IR wavelengths. I don't understand what mechanism is available to make the clouds reflective to thermal IR.

Be that as it may, the salient difference between regular cirrus clouds and jet contrails is that the ice particles in contrails are larger and more densely distributed. That makes them more reflective to incoming solar radiation, and apparently less reflective to outgoing thermal radiation.

I'll try to post a follow-up once I've done more research.

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#38
In reply to #35

Re: Water Vapor Effect On Climate Change

02/21/2013 11:27 AM

Funny, I will eat some of my words too. I read the 9/11 report when it first came out, and remembered that lack of contrails produced higher daily temperatures. What I forgot is that he also found lower night time temperatures when no contrails were present. When asked about it later, the author said that he felt that his results would indicate that contrails produced an overall net warming effect, but that it was very slight.

So, envelope guy was right in terms of the net effect.

I'm sure it's tough to tease out the data, as contrails do seed the formation of cirrus clouds. The contrails may have one effect, but that may reverse as they break up to form actual cirrus clouds.

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#44
In reply to #35

Re: Water Vapor Effect On Climate Change

02/21/2013 11:22 PM

It's the shape of the crystals and how they stacked...
http://en.wikipedia.org/wiki/Cirrus_cloud#CITEREFDowlingRadke1990

The ice crystals in cirrus clouds have different shapes in addition to different sizes. Some shapes include solid columns, hollow columns, plates, rosettes, and conglomerations of the various other types. The shape of the ice crystals is determined by the air temperature, atmospheric pressure, and icesupersaturation. Cirrus in temperate regions typically have the shapes segregated by type: the columns and plates tend to be at the top of the cloud, whereas the rosettes and conglomerations tend to be near the base.[6] In the northernArctic region, cirrus clouds tend to be composed of only the columns, plates, and conglomerations, and these crystals tend to be at least four times larger than the minimum size. In Antarctica, cirrus are usually composed of only the columns, and these columns are much longer than normal.

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#29

Re: Water Vapor Effect On Climate Change

02/20/2013 10:04 PM

Yes it is significant. Jet contrails cover a significant portion of the sky at all times for example. Atmospheric pressure is about 15psi, that means a square inch of ground supports a column of air stacked up that tapers off to vacuum and weighs 15 pounds. How much pollution would you have to add to it to change its properties? Not much. Drive a truck cross country and you have an exhaust pipe sized cylinder of unbreathable air coast to coast. Add millions more, and you can maybe visualize why burning stuff to move 6 billion people around the planet every day might not be a good idea considering the fact that we only have a fixed amount of air to breath...

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#34
In reply to #29

Re: Water Vapor Effect On Climate Change

02/21/2013 2:04 AM

'....might not be a good idea considering the fact that we only have a fixed amount of air to breath.......'

.

OH! NO! What do you mean!?! They aren't making any more? When did this happen?

.

This is part of those damn Sequestrations, isn't it.

.

Why did they have to cut the whole program? Couldn't they have just furloughed it? Just cut back on the number of days a month we couldn't breathe... but not cut the whole thing. That is just too extreme.

.

I wonder if those Flora Union air manufacturers that were displaced

by the 'we-are-the-government,-we-know-the-perfect-solution-to-problems-you-didn't-even-know-you-had,-because-we-are-untainted-by-experience-morals,-or-intelligence' Bill,

might be willing to come off strike?

.

That would certainly make me breathe a little easier.

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#41

Re: Water Vapor Effect On Climate Change

02/21/2013 8:18 PM

"We know for sure that the loop gain for the water vapor - temperature feedback loop is not greater than unity, because if it were we wouldn't be around to worry about it."

Is it unreasonable to assume, that on a global average, water vapor content of our atmosphere is dependant upon planetary temperature?

Is saturation a linear function of temperature? If it is not linear - does it increase or decrease as temperature?

If the amount of water vapor at saturation increases non-linearly as temperature, would there ever be a temperature where the "water vapor - temperature feedback loop gain" becomes greater than unity?

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#46
In reply to #41

Re: Water Vapor Effect On Climate Change

02/22/2013 3:31 PM

Yes on all counts. Yes, on a global average, water vapor content of the atmosphere is very much dependent on temperatures; yes, saturation vapor pressure is non-linear with temperature; and yes, it's possible for the water vapor - temperature feedback loop gain to exceed unity. Not at our current distance from the sun and solar intensity, fortunately, but it wouldn't take a large change..

The earth's natural black body radiation temperature -- the average surface temperature that would balance incoming solar and outgoing thermal radiation if the earth were a black body with no greenhouse gases in its atmosphere -- is well below the freezing point of water. Something like -30C, I believe (but don't quote me on that exact number). At that temperature, the sublimation vapor pressure of ice is so low, and the slope of its increase with temperature so slight, that the feedback loop gain is well under unity. That's why a "snowball earth" is possible.

If the sun were brighter, however, or the earth a bit closer to it, it could be a different story. If the earth's natural black body radiation temperature were above water's freezing point, then the steeper slope of the vapor pressure vs. temperature curve in that region would make the feedback loop gain greater than unity. Then we'd have runaway greenhouse warming. The warming would continue until the seas had all boiled dry, and earth would have an extremely thick atmosphere of water vapor. Over geological time, as water molecules were split by solar UV radiation, the hydrogen would escape to space, the oxygen left behind would combine with any carbon or sulfur it could find, and the atmosphere would evolve into a thick atmosphere of mainly CO2 and SO2, with sulfuric acid clouds.

In other words, if the earth were at the same distance from the sun as Venus is, it would come to closely resemble Venus. Aside from the accident of orbital positions, Venus and the earth really are twin planets.

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#45

Re: Water Vapor Effect On Climate Change

02/22/2013 12:45 PM

I have a more general commentary I thought of posting. Two things are preventing it. 1) I don't have the time to put what's in my head into words right now (lucky for ALL), and 2) It can, quickly become depressing. (Actually, as long as I concentrate on the depressing part, it would probably be rather short. Then the depression tells me why post it at all -- that's the circular depressive nature of it.) I'm sure if I look around I can probably find a book that resonates with the overall pessimism and just post that link. It would save all the way around. There really is very little new under the Sun.

As I was surfing, looking for a contributing idea to my depression, I happened across this site called "Web of Stories." It is interesting in that it seems to feature a number of famous scientists. Living science history records. I guess some might characterize it as a bunch of "geezers," sometimes having trouble remembering events in their lives; or romanticizing those memories. I find it enjoyable. Because I consider there may be a general interest in the link, I'm not marking this post OT, where, it, otherwise, would qualify.

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