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Post by france on Oct 24, 2010 15:40:43 GMT
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Post by nautonnier on Oct 24, 2010 17:11:05 GMT
"So the actual effect was assumed then modeled the references I gave to glc actually measured the forcing of the clouds directly" The forcing is expected to be negative. The issue isn't what the sign of the forcing current is now, it's how that will change in a warmer world. Of course you can't measure that without a time machine. Therefore you have to calculate it based on theory (ie models). The key part from the links though is support for my claim that high level clouds have a warming effect on Earth while low level clouds have a cooling effect: "Clouds both reflect sunlight, which cools the Earth, and trap heat in the same way as greenhouse gases, thus warming the Earth. Different types of clouds do more of one than the other. The net effect of clouds on climate change depends on which cloud types change, and whether they become more or less abundant, thicker or thinner, and higher or lower in altitude." "The forcing is expected to be negative. The issue isn't what the sign of the forcing current is now, it's how that will change in a warmer world. Of course you can't measure that without a time machine. Therefore you have to calculate it based on theory (ie models)."SoCold clouds of ice crystals will the same reflective albedo effect regardless of the 'average temperature' The only change is that in a warmer world there will be more clouds increasing the albedo and only two or three percent increase in cloud albedo is enough to offset the _projected_ CO 2 forcing. Remember SoCold that clouds can only trap heat that is there to be trapped. If the cloud cover remains for several days temperatures will drop - regardless of the type of cloud. Clouds will keep the surface cold just as well.
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Post by socold on Oct 24, 2010 20:47:37 GMT
Some clouds have a stronger warming effect than a cooling one. So if those types of cloud increase more than the low level clouds, the net effect would be warming. Alternatively the net effect could be negligible.
We are back to the Earth being much warmer in the past again. If cloud levels increase by 3% to a doubling of co2 (or a 2% increase in solar activity) then the Earth would be physically unable to warm more than it is already.
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Post by nautonnier on Oct 24, 2010 21:01:09 GMT
Some clouds have a stronger warming effect than a cooling one. So if those types of cloud increase more than the low level clouds, the net effect would be warming. Alternatively the net effect could be negligible. We are back to the Earth being much warmer in the past again. If cloud levels increase by 3% to a doubling of co2 (or a 2% increase in solar activity) then the Earth would be physically unable to warm more than it is already. SoCold you are confusing the 'temperature' of the cloud tops with the albedo of the clouds. Satellite measures are showing that the albedo reflecting incoming shortwave radiation together with outgoing IR is negative forcing. So it is quite possible that there is a level of warming that cannot be exceeded due to the albedo of clouds that would be formed. Trenberth's diagram that you regularly publish here always assumes a fixed amount for cloud albedo - this is apparently not borne out by recent satellite observations. Clouds are not a fixed parameter as in the GCMs they are a variable.
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Post by socold on Oct 24, 2010 21:04:16 GMT
clouds are not fixed in GCMs, they are variable too
I am not confusing cloud tops. If the amount of high level clouds increase but lower clouds don't, the net effect is warming, even though overall the amount of clouds has increased.
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Post by sigurdur on Oct 25, 2010 2:08:22 GMT
It is obvious we are talking about clouds and what they do. I have to quible with Socold a bit. Near the 49th parralel, high clouds at night do NOT act to retain heat. How do I know this? I live here. Now.....low clouds at night DO act to retain heat very well. You can have a day that has a high of 50F, and if it is slightly cloudy or the clouds are high, you can be certain that it will freeze at night. I am talking October, November time frame. IF you have a layer of low clouds, even with only a 50F high, the temp will prob not drop below 40 at night. Tonight is a good example of that. High today, 53 and dense clouds. Low projected tonight, 44 with those low clouds. At this time of year, one only has to look at what clouds are going to role in to decide how cold the night will be and plan for the next days work.
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Post by nautonnier on Oct 25, 2010 11:00:42 GMT
clouds are not fixed in GCMs, they are variable too I am not confusing cloud tops. If the amount of high level clouds increase but lower clouds don't, the net effect is warming, even though overall the amount of clouds has increased. I like the dogma in the face of evidence SoCold - your cognitive dissonance is showing
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Post by nautonnier on Oct 25, 2010 11:04:08 GMT
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Post by icefisher on Oct 25, 2010 20:05:03 GMT
Wow! Lets see more CO2 = more warming and more water vapor; and more water vapor = more cooling. Sure looks like negative feedback! Seems to me the jig is up. Observation wins again!
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Post by socold on Oct 25, 2010 21:27:00 GMT
clouds are not fixed in GCMs, they are variable too I am not confusing cloud tops. If the amount of high level clouds increase but lower clouds don't, the net effect is warming, even though overall the amount of clouds has increased. I like the dogma in the face of evidence SoCold - your cognitive dissonance is showing I've already provided two links that mention high level clouds have a net warming effect on climate. Look at this (the top graph): The top panel shows net cloud radiative forcing, annually averaged as observed by the ERBE. Negative values (red colors) indicate that clouds reduced the energy balance of Earth by reflecting more solar radiation than the amount by which they reduced the escaping infrared radiation.www.nap.edu/openbook.php?record_id=11991&page=29Conversely then the blue areas are clouds increasing the energy balance of the Earth by reducing escaping IR more than they reflect sunlight. and: Clouds play a leading role in this real-life mystery. Clouds both reflect sunlight, which cools the Earth, and trap heat in the same way as greenhouse gases, thus warming the Earth. Different types of clouds do more of one than the other. The net effect of clouds on climate change depends on which cloud types change, and whether they become more or less abundant, thicker or thinner, and higher or lower in altitude.Many people assume that since more water will evaporate from the oceans as the climate warms, it will be cloudier, with thicker and denser clouds. However, a warmer atmosphere needs more water vapor molecules to become saturated and to condense into clouds, so it is hard to anticipate exactly how clouds respond to human-induced climate perturbations. For example, although summer is warmer than winter, and the humidity is usually higher in summer, nevertheless the sky is not noticeably cloudier on average in summer than in winter.www.giss.nasa.gov/research/briefs/delgenio_03/
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Post by icefisher on Oct 25, 2010 22:21:19 GMT
Many people assume that since more water will evaporate from the oceans as the climate warms, it will be cloudier, with thicker and denser clouds. However, a warmer atmosphere needs more water vapor molecules to become saturated and to condense into clouds, so it is hard to anticipate exactly how clouds respond to human-induced climate perturbations.Thats all fine and good Socold but you are back to talking theory here. What you need to do is take the charts provided by Naut... and show us where those places are. . . .places where there is more water vapor and less IR being emitted. It just jumps out at us where more IR is being emitted with more water vapor. Maybe its a color issue or something but lets talk real observations here and show us how it is occurring rather than keeping on with the untested and unvalidated theoretical speech. Show us where IR is up and water vapor is down because those regions would be the only available source of more greenhouse effect. I have to suspect that there is a very small percentage of the earth surface where you could demonstrate that. I think that because of real greenhouse experiments that show so little warming due to blocking IR suggests that IR emission is already mostly above the surface due to saturation at the surface. If some areas remain to decrease IR emissions via increasing water vapor its probably mostly overwhelmed by the increasing clouds that will result. To suggest no increasing thick clouds is nonsense and everywhere clouds do increase it will be a negative feedback just as the GHE becoming progressively less potent itself. It seems logical that the greenhouse effect started very potent with positive feedbacks with water vapor then progressively became saturated at the surface maybe when cloud cover got high. What we see now is probably fluxuation over and under the saturation point. But I will be waiting for some observational evidence before I challenge myself with anymore theory from you.
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Post by icefisher on Oct 25, 2010 23:21:23 GMT
I've already provided two links that mention high level clouds have a net warming effect on climate. Look at this (the top graph): Conversely then the blue areas are clouds increasing the energy balance of the Earth by reducing escaping IR more than they reflect sunlight. What I see on the legend is the light sky blue, being the biggest blue area being in negative territory (zero to minus 5) so all you are looking at in this regard is the dark blue areas. And of course this does not factor in the transport of heat from the surface by convection which would reduce surface radiation and shift the color scheme zero further into the dark blue areas. So probably what is happening is we are riding the saturation point fluctuating above and below it in time with ocean storage exchange and we can't go too far above the saturation point because we need heat to put more water vapor up in the air.
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