AGW- Does it rest all with the Climate Models?

[blizzard1024]

The Earth's climate has warmed since the 1970s. No doubt. There are many metrics.... summer arctic Sea ice extent dropping...warmer Ocean Heat Content...satellite and surface stations all show some warming. Glaciers retreating, summer NH snow cover dropping and many more record highs vs record lows. I probably forgot some. Anyone who denies this or blames UHI etc is a quack. The Arctic is always the most sensitive to climate changes both directions vs the Antarctic, i.e Glacial cycles etc. So a warming climate is going to rapidly show up in the Arctic as it is now. But, how do we know this warming trend is based mostly on increasing CO2? The "proof" that is always given is running climate models with increasing CO2 vs without. The only way to explain the warming trend from the 1970s to 2000s is by increasing CO2 in the model world. I don't see modeling anything as proof. They are models. Are we that arrogant to think we have a handle on our complex climate system that we can model all the feedbacks? Solar insolation has been steady or slowly declining (I think). Could it be ocean currents? I am trying to rule out any other possibilities, like PDO/AMO etc as the reason for the recent warming in my mind. I have read arguments about the PDO and AMO and how the PDO is dropping and once the AMO drops we will see global cooling. Also the 20th century had a maximum in solar activity vs the Little Ice Age minimums and now is declining some. But, wouldn't the heat stored in the oceans take some time to work through like decades or even longer? Again, can we really rule out natural variability as the dominant cause? CO2 doubling without feedbacks = about 1.2C. The water vapor feedback is key here and also clouds and convection in the tropics. All these are not modelled very well. So you can see why someone with an atmospheric science background should be skeptical....too learn! We know how models work and how feedbacks etc are poorly modeled in NWP. The global climate models produce a double ITCZ structure in the Pacific which they know is wrong for example. The NWP models also do too! If convection is a primary way to remove excess energy, then this is very unsettling to me as a scientist. So my point is: What is the proof that CO2 is the dominate mechanism in driving our climate in the present day? It didn't in the past and don't use the models as arguments. I like to hear what others say. Again, I am not a "troll" or trying to get people going. I am sincerely trying to learn and convince myself of CO2 effects. My problem is I have had extensive training in radiative transfer, thermodynamics, atmospheric dynamics, paleoclimatology and I just don't see CO2 as a major driver of climate climate. It depends on feedbacks which nobody has proven to my knowledge. In my opinion,there was a feeble attempt...Solen tried with the reduction in temperature due to Pinatubo. But that was a different more dramatic driver of short term climate change. Let's collectively express our points with facts and not attack each other. This is supposed to be a forum for learning right??? Anyway, I am all ears here folks.

[skierinvermont]

It has nothing to do with models. It doesn't even rely on the fact that we have been warming for the last 100 years and especially the last 40.

The basic fact is that based on simple radiative physics doubling CO2 causes 1.2C of warming. You yourself said that. If you already accept that, then I do not see what the problem is. You already accept the fact that CO2 causes significant warming on its own. Feedbacks could enhance or diminish this forcing, but not eliminate it. Even very strong negative feedbacks would only cut it in half at most. But it is very obvious from paleoclimate records that the net feedbacks of the climate system are positive, likely very positive. It would be impossible to see 6C+ swings in temperature without net positive feedbacks (or massive external radiative forcings on the order of 50W/m2++ which do not exist). We also know that water vapor is an exceptionally strong positive feedback. This alone approximately doubles the effect of CO2 alone to 2.4C.

So 2.4C is a good starting point for climate sensitivity IMO. Then it comes down to are the remaining feedbacks besides water vapor positive or negative. We have much less certainty about that. But it's very unlikely (just based on common sense) that any of the other forcings total more than +/-2W/m2 (~.8C). Also paleoclimate tells us that net feedbacks are likely very positive.

So even if we couldn't rule out other factors, it is still possible to conclude CO2 has caused a large part of the warming to date. But it is also possible to rule out the other factors as having an effect as large as CO2.

It is also very easy to rule out the PDO and AMO. The PDO and AMO move energy around within the system. They do not add or remove energy. And yet the oceans have absorbed an incomprehensible amount of energy over the last 100 years. The earth continues to absorb far more energy than it emits. The only viable candidates are solar, the greenhouse effect, or cloud cover. It's fairly easy to rule out solar or cloud cover.

Cloud cover would require fairly major changes that in order to produce enough warming that we would have noticed. Also there is no reason that cloud cover would suddenly change so drastically. Solar also does not make sense because all of the solar factors have been pointing towards cooling since about 1970. The massive lag effect you proposed does not make sense. When the solar cycles increases, surface temperature responds immediately. This is why we observe around a .1-.15C effect over the course of the 11-year solar cycle from min to max. Also your proposed lag does not explain why the earth remains in a very large energy imbalance. The massive warming since 1970 (increasing outgoing long wave radiation) and the decrease in the hypothesized solar parameters, should have helped to close (actually reverse) the energy imbalance. Instead we continue to net absorb an incomprehensible amount of energy year after year.

One more piece of evidence I find convincing is sea level reconstructions over the last 2000 years. Sea levels have now likely reached and surpassed the highest levels in the last 2000 years and are continuing to rise rapidly. Even if the earth stopped warming today (magically), sea levels would continue to rise for another 50-100+ years. This would put us far far above the highest sea levels of the last 2000 years. Is it merely a coincidence this coincides with massive accumulation of a greenhouse gas in the atmosphere? Of course not.

And the most impressive thing about the massive energy imbalance, rising surface temperatures, and rising sea levels is that it has all occurred despite the fact that all of the sulfates we have been spilling into the atmosphere amount to a Pinatubo-sized eruption every few years which has a dramatic cooling effect.e

I don't understand why you are having such a hard time with this once you already accept the fact that doubling CO2 causes 1.2C of warming. That fact alone dictates that CO2 has caused a large portion of the warming to date. From there it is not very difficult to understand that the net feedbacks must be positive.

[WeatherRusty]

The net anthropogenic radiative forcing to date is estimated at about 1.6W/m^2. That also happens to be about the absolute radiative forcing given by increased atmospheric CO2. Total anthropogenic positive forcing is about 2.4W/m^2, with negative forcing of about 0.8W/m^2 cancelling the difference out. So humans have added about 1.6W/m^2 to the radiative forcing.

We get about 0.3C of warming per 1W of forcing according to the Planck Law/Stefan Boltzmann, so we can see that about 0.5C of the warming to date (before feedback) could be attributed to CO2 if the system were to have reached thermal equilibrium with the forcing....which it has not.

Some of the 0.8C global warming to date is due to this Planck Response, while some additional is due to feedback. Some of the growing forcing has not been equilibrated to surface temperature, thus we detect an in/out energy imbalance at the top of atmosphere.

When a full doubling of CO2 has occurred to about 560ppm over the pre-industrial level of 280ppm, another several decades will be required to fully equalize surface temperature with the radiative forcing. You will then expect 1.2C of direct warming as a consequence of the 3.7W/^2 radiative forcing given by CO2 as an isolated factor. What happens in addition to that involves total climate sensitivity to the 1.2C of warming influence, which science has every indication is positive to some degree.

With regard to convection, remember every bit of energy lost to space from the surface is in the form of radiation, most of it emanating from high in the troposphere at a radiation temperature of 255K.

[blizzard1024]

It has nothing to do with models. It doesn't even rely on the fact that we have been warming for the last 100 years and especially the last 40.

The basic fact is that based on simple radiative physics doubling CO2 causes 1.2C of warming. You yourself said that. If you already accept that, then I do not see what the problem is. You already accept the fact that CO2 causes significant warming on its own. Feedbacks could enhance or diminish this forcing, but not eliminate it. Even very strong negative feedbacks would only cut it in half at most. But it is very obvious from paleoclimate records that the net feedbacks of the climate system are positive, likely very positive. It would be impossible to see 6C+ swings in temperature without net positive feedbacks (or massive external radiative forcings on the order of 50W/m2++ which do not exist). We also know that water vapor is an exceptionally strong positive feedback. This alone approximately doubles the effect of CO2 alone to 2.4C.

So 2.4C is a good starting point for climate sensitivity IMO. Then it comes down to are the remaining feedbacks besides water vapor positive or negative. We have much less certainty about that. But it's very unlikely (just based on common sense) that any of the other forcings total more than +/-2W/m2 (~.8C). Also paleoclimate tells us that net feedbacks are likely very positive.

So even if we couldn't rule out other factors, it is still possible to conclude CO2 has caused a large part of the warming to date. But it is also possible to rule out the other factors as having an effect as large as CO2.

It is also very easy to rule out the PDO and AMO. The PDO and AMO move energy around within the system. They do not add or remove energy. And yet the oceans have absorbed an incomprehensible amount of energy over the last 100 years. The earth continues to absorb far more energy than it emits. The only viable candidates are solar, the greenhouse effect, or cloud cover. It's fairly easy to rule out solar or cloud cover.

Cloud cover would require fairly major changes that in order to produce enough warming that we would have noticed. Also there is no reason that cloud cover would suddenly change so drastically. Solar also does not make sense because all of the solar factors have been pointing towards cooling since about 1970. The massive lag effect you proposed does not make sense. When the solar cycles increases, surface temperature responds immediately. This is why we observe around a .1-.15C effect over the course of the 11-year solar cycle from min to max. Also your proposed lag does not explain why the earth remains in a very large energy imbalance. The massive warming since 1970 (increasing outgoing long wave radiation) and the decrease in the hypothesized solar parameters, should have helped to close (actually reverse) the energy imbalance. Instead we continue to net absorb an incomprehensible amount of energy year after year.

One more piece of evidence I find convincing is sea level reconstructions over the last 2000 years. Sea levels have now likely reached and surpassed the highest levels in the last 2000 years and are continuing to rise rapidly. Even if the earth stopped warming today (magically), sea levels would continue to rise for another 50-100+ years. This would put us far far above the highest sea levels of the last 2000 years. Is it merely a coincidence this coincides with massive accumulation of a greenhouse gas in the atmosphere? Of course not.

And the most impressive thing about the massive energy imbalance, rising surface temperatures, and rising sea levels is that it has all occurred despite the fact that all of the sulfates we have been spilling into the atmosphere amount to a Pinatubo-sized eruption every few years which has a dramatic cooling effect.e

I don't understand why you are having such a hard time with this once you already accept the fact that doubling CO2 causes 1.2C of warming. That fact alone dictates that CO2 has caused a large portion of the warming to date. From there it is not very difficult to understand that the net feedbacks must be positive.

Well, I don't see 1.2C of warming as that big of a deal. We already have added some to this...so maybe another .5C to 1C in 100 years without feedbacks? I believe the most important feedback in the glacial cycles is the ice albedo effect NOT the water vapor feedback. It explains the rapid warm up out of ice ages and slow descent back into ice ages. It takes a long time to build ice sheets, but they collapse fast. The water vapor feedback should immediately have an effect because it is a condensing GHG with a short residence time in the atmopshere. Why do you see a rapid ramp up in temperature and then a slow decline in the glacial to interglacial cycles. It is the ice albedo effect IMHO. Models I believe grossly overstate the positive feedback with water vapor. If the water vapor feedback is so sensitive then the climate would have sprialled out of control when the CO2 levels rapidly rose out between glacials and interglacials. I don't think our earth climate is that vulnerable to slight changes in trace gases...CO2.

And back to Solar forcing....solar forcing is what heats the oceans. Long wave energy does not heat the oceans to much extent. It is short wave energy...so there could easily be a lag. It is the sun that drives changes in the ocean temperatures. CO2...has little effect...especially since H20 absorption bands overlaps CO2 bands at temperatures above freezing. I find it hard to believe or to be convinced that a trace gas will sprial the earth's climate out of control. 1.2C is not much and within the range of variability in the last 10,000 years. It actually I believe would benefit mankind.

Sea levels are also rising because of isostatic rebound from the glaciers that once covered much of the land in the NH. So they should be rising. We are coming out of an ice age which was only 15K years ago. Again, this does not convince me that this period of warming is any different from other periods of warming. And also, there really has not been much if any warming since 1998.

Good points though and thought provoking. THANKS.

[WeatherRusty]

Well, I don't see 1.2C of warming as that big of a deal. We already have added some to this...so maybe another .5C to 1C in 100 years without feedbacks? I believe the most important feedback in the glacial cycles is the ice albedo effect NOT the water vapor feedback. It explains the rapid warm up out of ice ages and slow descent back into ice ages. It takes a long time to build ice sheets, but they collapse fast. The water vapor feedback should immediately have an effect because it is a condensing GHG with a short residence time in the atmopshere. Why do you see a rapid ramp up in temperature and then a slow decline in the glacial to interglacial cycles. It is the ice albedo effect IMHO. Models I believe grossly overstate the positive feedback with water vapor. If the water vapor feedback is so sensitive then the climate would have sprialled out of control when the CO2 levels rapidly rose out between glacials and interglacials. I don't think our earth climate is that vulnerable to slight changes in trace gases...CO2.

And back to Solar forcing....solar forcing is what heats the oceans. Long wave energy does not heat the oceans to much extent. It is short wave energy...so there could easily be a lag. It is the sun that drives changes in the ocean temperatures. CO2...has little effect...especially since H20 absorption bands overlaps CO2 bands at temperatures above freezing. I find it hard to believe or to be convinced that a trace gas will sprial the earth's climate out of control. 1.2C is not much and within the range of variability in the last 10,000 years. It actually I believe would benefit mankind.

Sea levels are also rising because of isostatic rebound from the glaciers that once covered much of the land in the NH. So they should be rising. We are coming out of an ice age which was only 15K years ago. Again, this does not convince me that this period of warming is any different from other periods of warming. And also, there really has not been much if any warming since 1998.

Good points though and thought provoking. THANKS.

Water vapor increases exponentially with a rise in temperature per the Clausius-Clapeyron equation. That's not an output of models, it's a well known physical relationship.

The climate would not have spiraled out of control as CO2 increased coming out of full glaciation. Atmospheric CO2 rose from 180ppm to 280ppm, or a little more than one half a doubling, accounting for about 0.7C or 0.8C of warming before feedback.

As to being a trace gas, it is estimated that if CO2 were reduced to zero, the greenhouse effect would collapse and the oceans would freeze nearly to the equator within 50 years. That trace gas is the scaffolding which supports the greenhouse effect on Earth.

You are correct, the additional down welling IR does not warm the oceans in the same manner in which shortwave radiation does. The effect is to slow the loss of IR to space, thereby retaining thermal surface energy for a longer time. A surface which cools more slowly will be a warmer surface.

Glacial rebound elevates the continental masses further above sea level. I fail to see how you think this appears to raise sea levels.

[blizzard1024]

Water vapor increases exponentially with a rise in temperature per the Clausius-Clapeyron equation. That's not an output of models, it's a well known physical relationship.

The climate would not have spiraled out of control as CO2 increased coming out of full glaciation. Atmospheric CO2 rose from 180ppm to 280ppm, or a little more than one half a doubling, accounting for about 0.7C or 0.8C of warming before feedback.

As to being a trace gas, it is estimated that if CO2 were reduced to zero, the greenhouse effect would collapse and the oceans would freeze nearly to the equator within 50 years. That trace gas is the scaffolding which supports the greenhouse effect on Earth.

You are correct, the additional down welling IR does not warm the oceans in the same manner in which shortwave radiation does. The effect is to slow the loss of IR to space, thereby retaining thermal surface energy for a longer time. A surface which cools more slowly will be a warmer surface.

Glacial rebound elevates the continental masses further above sea level. I fail to see how you think this appears to raise sea levels.

actually glacial rebound is known to raise the land well inland and drop the land closer to shore. There are many instances of this. Yes Clausius-Clapeyron equation means warmer temperatures = more water vapor. But it is an exponential function, so if it warms from more water vapor for instance...it should keep warming and warming and spiral out of control. well it doesn't. there are breaking mechanisms like the formation of clouds and precipitation. Can anyone prove that a given level of CO2 in the atmosphere leads to a certain amount of water vapor? why is downwelled IR from CO2 so special? What about downwelled IR from H20? why does that not lead to an increase in temperature which in turn leads to more water vapor and so on? What if the sun gets a little brighter...then it gets a little warmer and then once again you have this spiral.

When Mt Pinatubo erupted, the earth cooled, water vapor went down causing further cooling which again should have spiralled out of control. What is the breaking mechanism? It is clouds and precipitation, convection that regulate our climate. Not a trace gas IMO. If CO2 were reduced to zero how do you know the greenhouse effect would collapse? Probably computer models I would imagine that are tuned to be sensitive to CO2 and do not handle clouds, precipitation or convection well. That's not proof. Has someone done a study to show the radiative effects of increasing CO2 using satellite data? It would be neat to compare data from the 1960s or even 70s to present and see what changes have occurred to the absorption spectra. Is it just the CO2 bands that are widening or do we see H20 bands are also

widening. If so, can they calculate, using satellite measurements (not models), to prove the increasing IR absorption of the atmosphere. Now that would be a cool study and help prove that a trace gas has such power over our whole climate. I imagine someone has got to have done a study like this. if so, please share.

I do agree doubling CO2 based on radiative transfer leads to some warming around 1.2C...of which maybe we have already seen .5C??? That is physics that I agree with. But another .7C over 50-100 years assuming some lags? I think we can handle that. It is the feedbacks that we have to figure out. My opinion is that we don't understand them well. I believe they are slightly negative...otherwise small changes in climate are amplified and the climate would spiral out of control. our climate has had massive swings and life still abounds. common sense states that there are breaking mechanisms. again...appreciate the thoughtful feedback. thanks.

[WeatherRusty]

actually glacial rebound is known to raise the land well inland and drop the land closer to shore. There are many instances of this. Yes Clausius-Clapeyron equation means warmer temperatures = more water vapor. But it is an exponential function, so if it warms from more water vapor for instance...it should keep warming and warming and spiral out of control. well it doesn't. there are breaking mechanisms like the formation of clouds and precipitation. Can anyone prove that a given level of CO2 in the atmosphere leads to a certain amount of water vapor? why is downwelled IR from CO2 so special? What about downwelled IR from H20? why does that not lead to an increase in temperature which in turn leads to more water vapor and so on? What if the sun gets a little brighter...then it gets a little warmer and then once again you have this spiral.

When Mt Pinatubo erupted, the earth cooled, water vapor went down causing further cooling which again should have spiralled out of control. What is the breaking mechanism? It is clouds and precipitation, convection that regulate our climate. Not a trace gas IMO. If CO2 were reduced to zero how do you know the greenhouse effect would collapse? Probably computer models I would imagine that are tuned to be sensitive to CO2 and do not handle clouds, precipitation or convection well. That's not proof. Has someone done a study to show the radiative effects of increasing CO2 using satellite data? It would be neat to compare data from the 1960s or even 70s to present and see what changes have occurred to the absorption spectra. Is it just the CO2 bands that are widening or do we see H20 bands are also

widening. If so, can they calculate, using satellite measurements (not models), to prove the increasing IR absorption of the atmosphere. Now that would be a cool study and help prove that a trace gas has such power over our whole climate. I imagine someone has got to have done a study like this. if so, please share.

I do agree doubling CO2 based on radiative transfer leads to some warming around 1.2C...of which maybe we have already seen .5C??? That is physics that I agree with. But another .7C over 50-100 years assuming some lags? I think we can handle that. It is the feedbacks that we have to figure out. My opinion is that we don't understand them well. I believe they are slightly negative...otherwise small changes in climate are amplified and the climate would spiral out of control. our climate has had massive swings and life still abounds. common sense states that there are breaking mechanisms. again...appreciate the thoughtful feedback. thanks.

Satellite measurements confirm less longwave radiation is escaping to space at carbon dioxide absorptive wavelengths. Surface measurements find more longwave radiation returning back to Earth at these same wavelengths.

SEE HERE

Also, there is nothing special about downwelling IR from CO2. It is no different from that produced by water vapor in this context. When any greenhouse gas absorbes IR some of the energy is transferred to adjacent atmospheric molecules of oxygen and nitrogen etc. by molecular collision..thereby slightly warming the air. It is this IR, which is thermal radiation, which warms the surface due to the greenhouse effect. The atmosphere radiates in the infrared because it has a temperature. All bulk matter above absolute zero radiates at wavelengths inversly proportional to temperature. Greenhouse gases slow the loss of IR radiation to space, thereby maintaining a warmer near surface.

Behind water vapor and clouds, CO2 is the strongest contributor to that greenhouse effect.

Water vapor 50%, clouds 25%, CO2 20%.....everything else combined 5%.

You are arguing against very well established physics.

You understand and trust the physics which indicates any doubling of CO2 creates as surface warming of 1.2C apparently. That is all CO2 will do, no more, no less. Nothing special or magic. Just a consequence of reducing outgoing IR at specific wavelengths to the tune of 3.7W/m^2.

Your point that we lack a firm grasp of equilibrium climate sensitivity is acknowledged. Despite your reluctance to accept it, the peer-reviewed literature supports a climate sensitivity somewhere between 2C and 4.5C for a doubling of CO2...or its equivalent in radiative forcing from any source (3.7W/m^2).

[skierinvermont]

Lots of misinformation in here.

Sea level rise is not due to glacial rebound. Global sea levels were steady for the last 2000 years. In fact, they had been falling since the medieval warm period until the turn of the century. Now they have surpassed the MWP, and will continue to rise far beyond that even if no further warming takes place.

Yes studies have been down showing that the atmosphere is absorbing more LW radiation in the emission bands of CO2 and H2O. Yet another nail in the coffin so to speak.

Third, if you agree with Clausian-Clapeyron and the fact that radiative physics dictates a 1.2C rise per doubling of CO2, then there really is nothing to debate further. You have already agreed that CO2 causes moderate warming and you have already agreed that warming causes an exponential rise in water vapor. And presumably you understand that water vapor is a highly active greenhouse gas. Therefore it is a strong positive feedback.

And yet you refuse to accept this because you incorrectly believe that that would cause an uncontrollable feedback spiral. Even if that were true, it would not disprove the very basic logic that CO2 --> warming ---> water vapor via claus-clap---> more warming. That logic is not disputable.

But you are wrong that it would cause an uncontrollable feedback spiral. Uncontrolled feedbacks only occur when the feedback is greater than 1. CO2 causes 1.2C of warming, the water vapor feedback adds .6C, which adds another .3C, which adds another .15C, which adds another .075C, which adds another .0375C.... etc. etc. etc. The total feedback from water vapor would be 1.2C.

Uncontrolled spiraling feedbacks only occur when the warming caused by the feedback is greater than the initial warming effect itself. Say 1.2C of warming causes a 1.3C feedback.. which would cause an additional 1.4C of warming.. causing another 1.5C of warming etc etc etc.

The effect of water vapor is not that strong.

[OUtwister]

I will have to find the reference about glacial rebound. I know there is a component of that. Anyway. That aside. The clausius claperon eq is for saturation vapor pressure. Not vapor pressure. So really the cc equation does not prove more water vapor from warming. It is saturation vapor pressure. Atmosphere is far from saturated in most areas. I agree the water vapor feedback is not strong. So some moderate warming might occur from increased co2 emissions. Big deal.

I am unconvinced we have a disaster in the future. Should we strive for sustainabilty on our planet.YES. Should we should reduce pollution. Yes. I agree with all this. But I fail to see the proof that agw will be catastrophic. That's all.

[skierinvermont]

Seems more like you have already concluded this and are now ignoring the evidence.

[WeatherRusty]

I will have to find the reference about glacial rebound. I know there is a component of that. Anyway. That aside. The clausius claperon eq is for saturation vapor pressure. Not vapor pressure. So really the cc equation does not prove more water vapor from warming. It is saturation vapor pressure. Atmosphere is far from saturated in most areas. I agree the water vapor feedback is not strong. So some moderate warming might occur from increased co2 emissions. Big deal.

I am unconvinced we have a disaster in the future. Should we strive for sustainabilty on our planet.YES. Should we should reduce pollution. Yes. I agree with all this. But I fail to see the proof that agw will be catastrophic. That's all.

However, the atmosphere does apparently maintain near constant relative humidity. If this were not so, then the warmer climates would not produce increased precipitation like they do. Humidity needs to be maintained with increasing temps or clouds would not so readilly form.

Over the past 30 years, specific humidity over the oceans has been shown to have increased by about 4%.

[blizzard1024]

However, the atmosphere does apparently maintain near constant relative humidity. If this were not so, then the warmer climates would not produce increased precipitation like they do. Humidity needs to be maintained with increasing temps or clouds would not so readilly form.

Over the past 30 years, specific humidity over the oceans has been shown to have increased by about 4%.

But specific humidity has dropped in the upper levels where it has the most greenhouse effect. how is that?

Warmer temperatures globally and slight decreases in specific humidity aloft. This is counter to the theory of a positive feedback for water vapor.

[blizzard1024]

But specific humidity has dropped in the upper levels where it has the most greenhouse effect. how is that?

Warmer temperatures globally and slight decreases in specific humidity aloft. This is counter to the theory of a positive feedback for water vapor.

here is the temperature's at 300 mb same time period. This is not a constant relative humidity and water vapor is the dominant greenhouse gas. Something else is at work in our recent climate system's warming.

[bluewave]

But specific humidity has dropped in the upper levels where it has the most greenhouse effect. how is that?

Warmer temperatures globally and slight decreases in specific humidity aloft. This is counter to the theory of a positive feedback for water vapor.

A recent paper explains what you are seeing.

http://www.agu.org/p...0JD014192.shtml

A recent paper (Paltridge et al., 2009) found that specific humidity in the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis declined between 1973 and 2007, particularly in the tropical mid and upper troposphere, the region that plays the key role in the water vapor feedback. If borne out, this result suggests potential problems in the consensus view of a positive water vapor feedback. Here we consider whether this result holds in other reanalyses and what time scale of climate fluctuation is associated with the negative specific humidity trends. The five reanalyses analyzed here (the older NCEP/NCAR and ERA40 reanalyses and the more modern Japanese Reanalysis (JRA), Modern Era Retrospective-Analysis for Research and Applications (MERRA), and European Centre for Medium-Range Weather Forecasts (ECMWF)-interim reanalyses) unanimously agree that specific humidity generally increases in response to short-term climate variations (e.g., El Niño). In response to decadal climate fluctuations, the NCEP/NCAR reanalysis is unique in showing decreases in tropical mid and upper tropospheric specific humidity as the climate warms. All of the other reanalyses show that decadal warming is accompanied by increases in mid and upper tropospheric specific humidity. We conclude from this that it is doubtful that these negative long-term specific humidity trends in the NCEP/NCAR reanalysis are realistic for several reasons. First, the newer reanalyses include improvements specifically designed to increase the fidelity of long-term trends in their parameters, so the positive trends found there should be more reliable than in the older reanalyses. Second, all of the reanalyses except the NCEP/NCAR assimilate satellite radiances rather than being solely dependent on radiosonde humidity measurements to constrain upper tropospheric humidity. Third, the NCEP/NCAR reanalysis exhibits a large bias in tropical upper tropospheric specific humidity. And finally, we point out that there exists no theoretical support for having a positive short-term water vapor feedback and a negative long-term one.

http://www.skepticalscience.com/humidity-global-warming.htm

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[blizzard1024]

A recent paper explains what you are seeing.

http://www.agu.org/p...0JD014192.shtml

A recent paper (Paltridge et al., 2009) found that specific humidity in the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis declined between 1973 and 2007, particularly in the tropical mid and upper troposphere, the region that plays the key role in the water vapor feedback. If borne out, this result suggests potential problems in the consensus view of a positive water vapor feedback. Here we consider whether this result holds in other reanalyses and what time scale of climate fluctuation is associated with the negative specific humidity trends. The five reanalyses analyzed here (the older NCEP/NCAR and ERA40 reanalyses and the more modern Japanese Reanalysis (JRA), Modern Era Retrospective-Analysis for Research and Applications (MERRA), and European Centre for Medium-Range Weather Forecasts (ECMWF)-interim reanalyses) unanimously agree that specific humidity generally increases in response to short-term climate variations (e.g., El Niño). In response to decadal climate fluctuations, the NCEP/NCAR reanalysis is unique in showing decreases in tropical mid and upper tropospheric specific humidity as the climate warms. All of the other reanalyses show that decadal warming is accompanied by increases in mid and upper tropospheric specific humidity. We conclude from this that it is doubtful that these negative long-term specific humidity trends in the NCEP/NCAR reanalysis are realistic for several reasons. First, the newer reanalyses include improvements specifically designed to increase the fidelity of long-term trends in their parameters, so the positive trends found there should be more reliable than in the older reanalyses. Second, all of the reanalyses except the NCEP/NCAR assimilate satellite radiances rather than being solely dependent on radiosonde humidity measurements to constrain upper tropospheric humidity. Third, the NCEP/NCAR reanalysis exhibits a large bias in tropical upper tropospheric specific humidity. And finally, we point out that there exists no theoretical support for having a positive short-term water vapor feedback and a negative long-term one.

http://www.skeptical...bal-warming.htm

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is this new data accessible? would like to see it. basically if you can see specific humidity rises then you know we have a stronger greenhouse effect and how well it correlates to increasing temperatures. I have always used NCEP reanalysis data and yes years ago I was told by a climate scientist that is was not reliable. BUT no reason was given. To me it seemed like an inconvenience to the theory. If we have new datasets I would love to see this stuff.

[bluewave]

is this new data accessible? would like to see it. basically if you can see specific humidity rises then you know we have a stronger greenhouse effect and how well it correlates to increasing temperatures. I have always used NCEP reanalysis data and yes years ago I was told by a climate scientist that is was not reliable. BUT no reason was given. To me it seemed like an inconvenience to the theory. If we have new datasets I would love to see this stuff.

That's a good question. Maybe you could contact the authors of the paper and they could tell you how to access the data.

[blizzard1024]

That's a good question. Maybe you could contact the authors of the paper and they could tell you how to access the data.

I'll get right on it!

[WeatherRusty]

I'll get right on it!

You had asked about any studies indicating changes in CO2 spectral absorption over time. Did you look at the link I provided above which cites several such studies? You seemed so very interested!