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Le réchauffement et la double rétro-action de la vapeur d'eau


david3
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Si on veut que les déserts reculent il faut arrêter de les aggrandir mais il faut les irriguer!

Les activités humaines participent à l'asséchement des continents. Sans discernements, en n'importe quel point de la planète si on a besoin d'eau , on fait un forage et on pompe. Il ne faut pas s'étonner que les déserts avancent Maintenant si on vous dit comment les faire reculer personne va le croire. Il suffit de les irriguer , c'est à dire de mettre plus d'eau que les pompeurs n'en retirent . Comment ? En infiltrant les eaux de ruissellement. Quand on a trop d'eau il ne faut pas l'évacuer en drainant selon la pente en dilluant ses ordures chez le voisins aval, mais il faut préserver l'eau propre en trop pour l'infiltrer en suivant la courbe de niveau.

canimoulf1.gif

Quel est le rapport avec le sujet ?
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Pourquoi l'Europe s'est réchauffée trois fois plus vite que la moyenne de l'hémisphère nord ?

Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe

http://www.agu.org/pubs/crossref/2005.../2005GL023624.shtml

Abstract

Europe's temperature increases considerably faster than the northern hemisphere average. Detailed month-by-month analyses show temperature and humidity changes for individual months that are similar for all Europe, indicating large-scale weather patterns uniformly influencing temperature. However, superimposed to these changes a strong west-east gradient is observed for all months. The gradual temperature and humidity increases from west to east are not related to circulation but must be due to non-uniform water vapour feedback. Surface radiation measurements in central Europe manifest anthropogenic greenhouse forcing and strong water vapor feedback, enhancing the forcing and temperature rise by about a factor of three. Solar radiation decreases and changing cloud amounts show small net radiative effects. However, high correlation of increasing cloud-free longwave downward radiation with temperature (r = 0.99) and absolute humidity (r = 0.89), and high correlation between ERA-40 integrated water vapor and CRU surface temperature changes (r = 0.84), demonstrates greenhouse forcing with strong water vapor feedback.

Un article explicatif vraiment excellent sur RealClimate :

Busy Week for Water Vapor

http://www.realclimate.org/index.php/archi...vapor/#more-212

Measurements from a network of six Alpine surface budget stations indicate that the primary radiative forcing driving the increase in surface temperature is an increase of downward clear sky infrared from the atmosphere to the surface. The annual average increase in this term is nearly 4 Watts per square meter between 1995 and 2002. Net cloud effects are relatively less important. Moreover, the increase in downward clear sky infrared is correlated with an increase in atmospheric temperature, and also an increase in the water vapor content of the surface layer of the atmosphere. Using a simple radiation model, the authors conclude that about a third of the increase in downwelling infrared is due to the increase in atmospheric temperature,and the rest is due primarily to an increase in the water vapor content of the low level atmosphere.

This happens because water vapor is a greenhouse gas, so increasing the water vapor content makes air act more like a perfect blackbody emitter, if the air is not already opaque to infrared. In this case, increasing water vapor content will make the air a better absorber and emitter, even if its temperature doesn't change. From this result we learn that: (a) observations confirm the expected increase of low level water vapor content with temperature , and ( b ) the increase in water vapor accounts for the bulk of the increase in downward radiation heating the surface

The authors then subtract off the part of the downward infrared radiation increase attributable to temperature and water vapor increase, and thus estimate the part due directly (as opposed to via feedbacks) to the increase in anthropogenic greenhouse gases such as CO2. They estimate this to be about one third of a Watt per square meter.

It is striking that the changes in the Earth's surface radiation budget due to anthropogenic greenhouse gases are so profound that they can be directly observed on a regional scale, over such a short time period. So far, so good. Physics seems to be working as it should, and climate scientists seem to be basing their understanding of climate change on rock-solid physical principles. The authors do not fall into the trap of assuming that water vapor is the root cause of the observed warming. They understand fully well that water vapor acts as a feedback to amplify forcing due to CO2 increase, and make this clear in their paper. This paper does not, however, deal directly with the problem of whether European warming can be attributed to CO2 increase. It only shows that, whatever mechanism is causing the warming of the atmosphere in this region, the surface warming is being amplified by low level water vapor feedbacks.

Réchauffement ....> rétro-action de la vapeur d 'eau

Vraiment intéressante cette étude. "Sceptiques", attention à en bien comprendre le sens... default_mellow.png

" (...) sound article was published with the unfortunate sub-header "Water vapour rather than carbon dioxide in the atmosphere is the main reason why Europe's climate is warming, according to a new study." This gives the casual reader the erroneous impression that the study concludes CO2 is unimportant. It feeds the old, discredited skeptics' notion that the water vapor greenhouse effect is so dominant that there's no need to be concerned about CO2. "

[une vieille notion sceptique discréditée : la vapeur d'eau est tellement dominante qu'il est inutile de se préocupper du CO2 ]

All of this was relatively harmless, but all the coverage missed the boat in the same way. Press reports failed to note that the water vapor feedback discussed in Philipona et al. is not the same water vapor feedback usually discussed in connection with global warming. It is instead a surface water vapor feedback which adds additional surface warming on top of the usual things we talk about. The effect is already incorporated in the climate models used in IPCC forecasts, but the new observational study will be useful as a reality-check. (...)

For the most part, surface temperature changes are determined by perturbations to the top-of-atmosphere budget, and the surface budget is just dragged along, accomodating itself to whatever changes in surface temperature are demanded in order to be able to satisfy the top of atmosphere budget. It is impossible to understand the greenhouse effect without thoroughly understanding this point.

I shall try to explain. In equilibrium, the Earth must lose as much energy out the top of its atmosphere as it gains by absorption of Solar energy. This is the principle of energy balance that controls the climate of all Earthlike planets. Currently our planet is out of equilibrium because the rapid rise of carbon dioxide is more than the slow response time of the oceans can keep up with; even if CO2 increase were halted today, the planet would continue to warm for a while as it comes into equilibrium.

Planets only have one way of losing energy, which is by infrared radiation to space, often called "Outgoing Longwave Radiation," or OLR. The next piece of the story is that convection is always lifting air from the ground to high altitudes in the troposphere, causing the air to cool by expansion as it rises. This is the basic reason that temperature goes down with height in the troposphere. Convection and other dynamical heat transport mechanisms link together all the air in the troposphere, so that, to a first approximation, the whole troposphere can be considered to warm and cool as a unit. It doesn't matter much where you put in or take out heat from the troposphere.. It is mainly the net energy budget of the troposphere that counts.

Now, if the atmosphere contains a greenhouse gas, the atmosphere will be partly opaque to infrared trying to escape from the surface. Infrared from the surface will be absorbed before it gets very far. As a result, the infrared that escapes to space comes more from the higher, colder parts of the atmosphere. Since infrared radiation increases like the fourth power of temperature, the radiation from these layers is much feebler than the radiation that would escape from the ground. On the other hand, the radiation into the ground comes predominantly from the warm layers nearest the ground.

RCWaterFig1.jpg Canicule 2003, Paris

(...)If we increase the concentration of a greenhouse gas (say, CO2), then that makes more of the atmosphere opaque to infrared, and so the infrared escapes from yet higher and thinner and colder parts of the atmosphere. This would reduce the OLR, if the temperature of the atmosphere were held fixed at its original value. The planet would then be receiving more Solar energy than it gets rid of. Solar energy is primarily absorbed at the surface and communicated to the troposphere by surface heat fluxes. This energy input stays the same, while the reduction in OLR has reduced the rate at which the atmosphere is losing energy. As a result, the troposphere must warm until the top of atmosphere energy budget is brought back into balance. Remember that the whole troposphere warms more or less as a unit. That means that the air near the ground must warm along with the rest. In this way, we see that the warming of the entire troposphere can mostly be inferred just by thinking about the top of atmosphere budget, without bringing the surface budget into the picture in any detail.

So far, all we need to know about the surface budget is that all the energy absorbed at the surface eventually makes its way into the atmosphere.

We are not done yet. We still have to say how this change in the tropospheric temperature translates into a change in the temperature of the solid underlying surface on which we live. This is where the surface energy budget comes in. The complication here is that, while the top-of-atmosphere balance has only one loss term (the infrared), the surface has many ways to exchange energy with the overlying atmosphere:

- Sensible heat flux (warming or cooling air in immediated contact with the surface and then mixing it aloft by turbulent motions)

- Latent heat flux (cooling the surface by evaporation)

- Infrared heat flux (cooling by emission of infrared by the surface, and warming by absorption of downelling infrared from the atmosphere)

...latent heat flux tends to be the dominant term, because evaporation is such an effective way of transferring heat.

The buffering of the surface budget by evaporation limits the leverage of the surface budget on surface temperature over much of the rest of the globe, though not to the same extent as in the tropical oceans.(...) the top of atmosphere budget determines the warming of the low level air temperature, while the surface budget determines the difference between the air temperature and the surface temperature.

(...) If the Sahara were made moister (as it was some thousands of years ago) the surface would cool regardless of what CO2 is doing. Conversely, if the moister parts of North America dry out in response to CO2 increase, the reduction in soil moisture will compound the surface temperature increase. Getting back to the implications of Philipona's results, since Europe is not in a completely evaporation-dominated regime, the downwelling infrared increase could possibly allow the surface temperature to warm more rapidly than the air temperature, compounding the general global warming driven by CO2.

RCWaterFig2.jpg

The water vapor involved in the effect of water vapor on infrared downwelling to the surface is almost a completely separate issue – a different water vapor, as it were – from the water vapor we speak of when talking about the role of "water vapor feedback" in the context of global warming.. Water vapor feedback of the latter sort is a consequence of the effect of water vapor on the top of atmosphere radiation budget. (...)

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ff.jpg

The Radiative Signature of Upper Tropospheric Moistening

Brian J. Soden,1* Darren L. Jackson,2 V. Ramaswamy,3 M. D. Schwarzkopf,3 Xianglei Huang4

Climate models predict that the concentration of water vapor in the upper troposphere could double by the end of the century as a result of increases in greenhouse gases. Such moistening plays a key role in amplifying the rate at which the climate warms in response to anthropogenic activities, but has been difficult to detect because of deficiencies in conventional observing systems. We use satellite measurements to highlight a distinct radiative signature of upper tropospheric moistening over the period 1982 to 2004. The observed moistening is accurately captured by climate model simulations and lends further credence to model projections of future global warming.

http://www.sciencemag.org/cgi/content/abstract/310/5749/841

http://www.gfdl.noaa.gov/reference/bibliog...005/bjs0501.pdf

De l'eau, de l'eau partout !

http://www.colorado.edu/chemistry/chem5151/McBride.pdf

(...) There would appear to be less and less room for skeptics to dismiss climate model predictions on the grounds that we aren't sure they do water vapor feedback right. The picture is about to become even clearer, as researchers begin analyzing microwave upper level water vapor data, which will allow the analysis to be taken deeper into the convective, cloudy regions.

(...) it becomes increasingly clear that whyever the models do what they do to upper level water vapor, there can't be anything too terribly wrong with what they are doing.

http://www.realclimate.org/index.php/archi...vapor/#more-212

Water Vapor & Climate Change

New study confirms global warming predictions

http://www6.miami.edu/UMH/CDA/UMH_Main/1,1...41812-3,00.html

Soden said : “What’s most significant about our research is that we have identified a distinct characteristic of moistening in the satellite record. We can now see how the climate’s behavior is consistent with current models, validating their accuracy and their projections of future global warming.”

NB - Publications de Brian J. Soden : http://www.gfdl.noaa.gov/reference/bibliog...hors/soden.html

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De l'eau, de l'eau partout !

http://www.colorado.edu/chemistry/chem5151/McBride.pdf

(...) There would appear to be less and less room for skeptics to dismiss climate model predictions on the grounds that we aren't sure they do water vapor feedback right. The picture is about to become even clearer, as researchers begin analyzing microwave upper level water vapor data, which will allow the analysis to be taken deeper into the convective, cloudy regions.

(...) it becomes increasingly clear that whyever the models do what they do to upper level water vapor, there can't be anything too terribly wrong with what they are doing.

Les citations et les références sont un petit peu mélangées, dans le post de David, mais si je prends les conclusions de la présentation de McBride et Soden reprises ici, voici ce qu'elles donnes :Soden.jpg

La première conclusion (que j'ai encadrée en rouge) signifie :

  • Soit qu'on a pas compris encore cette fameuse rétroaction de la vapeur d'eau
  • Soit qu'on a besoin de financements complémentaires
  • Soit (et plus probablement) les deux.

Dans tous les cas, il vaut donc mieux être prudent et ne pas brandir cette présentation comme une preuve qu'elle n'est pas.

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Les citations et les références sont un petit peu mélangées, dans le post de David, mais si je prends les conclusions de la présentation de McBride et Soden reprises ici, voici ce qu'elles donnes :

Soden.jpg

La première conclusion (que j'ai encadrée en rouge) signifie :

  • Soit qu'on a pas compris encore cette fameuse rétroaction de la vapeur d'eau
  • Soit qu'on a besoin de financements complémentaires
  • Soit (et plus probablement) les deux.

Dans tous les cas, il vaut donc mieux être prudent et ne pas brandir cette présentation comme une preuve qu'elle n'est pas.

Ces conclusions sont simplement ceci

1 la vapeur d'eau dans la haute tropo joue un rôle clé et on ne domine pas parfaitement le sujet

mais

2 les observation satellie confortent bien modèles

autrement dit, on progresse.

En recherche, il est rare qu'un pb soit définitivement résolu. En fait, jamais sans doute sauf en Maths.

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Les citations et les références sont un petit peu mélangées, dans le post de David, mais si je prends les conclusions de la présentation de McBride et Soden...

Dans tous les cas, il vaut donc mieux être prudent et ne pas brandir cette présentation comme une preuve qu'elle n'est pas.

De quoi tu parles ?

Il ne s'agit pas, saur erreur de ma part, d'une présentation de "McBride et Soden" mais de McBride. Mais là n'est pas l'essentiel.

Raymond T. Pierrehumbert : (...) There would appear to be less and less room for skeptics to dismiss climate model predictions on the grounds that we aren't sure they do water vapor feedback right. The picture is about to become even clearer, as researchers begin analyzing microwave upper level water vapor data, which will allow the analysis to be taken deeper into the convective, cloudy regions.

http://www.realclimate.org/index.php/archi...vapor/#more-212

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A propos des nuages de l'Arctique (rétro-action) :

Arctic scientists look to clouds for climate clues

(...) The mystery is the droplets of water in the clouds. With the North Pole just 685 miles away, they should be frozen, yet more of them are liquid than anyone expected. (...)

(...) "Much to our surprise, we found that Arctic clouds have got lots of super-cooled liquid water in them. Liquid water has even been detected in clouds at temperatures as low as minus 30 degrees Celsius ," said Taneil Uttal, chief of the Clouds and Arctic Research Group at the Earth Systems Research Laboratory of the U.S. National Oceanic and Atmospheric Administration (NOAA). (...)

(...) Uttal noted that water clouds are more likely to warm the Arctic atmosphere than ice clouds, because the liquid clouds retain more heat radiated by the Earth's surface. "This means that the ice-to-water ratios in clouds may be very important in controlling the Arctic surface temperatures and how it melts," she said. (...)

(...)"The majority of the world's population hasn't really felt the global warming," said Awa. "But right now in the Arctic and in Nunavut, we're really worried because it's already affecting us. We are a thermometer of the world for what could happen." (...)

http://www.theeagle.com/stories/112606/world_20061126035.php

http://www.esrl.noaa.gov/psd/psd3/arctic/

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A propos des nuages de l'Arctique (rétro-action) :

Arctic scientists look to clouds for climate clues

(...) The mystery is the droplets of water in the clouds. With the North Pole just 685 miles away, they should be frozen, yet more of them are liquid than anyone expected. (...)

(...) "Much to our surprise, we found that Arctic clouds have got lots of super-cooled liquid water in them. Liquid water has even been detected in clouds at temperatures as low as minus 30 degrees Celsius ," said Taneil Uttal, chief of the Clouds and Arctic Research Group at the Earth Systems Research Laboratory of the U.S. National Oceanic and Atmospheric Administration (NOAA). (...)

(...) Uttal noted that water clouds are more likely to warm the Arctic atmosphere than ice clouds, because the liquid clouds retain more heat radiated by the Earth's surface. "This means that the ice-to-water ratios in clouds may be very important in controlling the Arctic surface temperatures and how it melts," she said. (...)

(...)"The majority of the world's population hasn't really felt the global warming," said Awa. "But right now in the Arctic and in Nunavut, we're really worried because it's already affecting us. We are a thermometer of the world for what could happen." (...)

http://www.theeagle.com/stories/112606/world_20061126035.php

http://www.esrl.noaa.gov/psd/psd3/arctic/

Je me demande si cet auteur ne découvre pas le fil à couper le beurre.

Des gouttes surfondues à -30°C , on connait depuis longtemps dans des nuages des latitudes moyennes . Il suffit qu'ils soient suffisamment hauts.

De satellite, on détecte aussi (depuis au moins 10 ans) la présence de particules sphériques à des températures aussi basses que ça. Or, les cristaux de glace ne sont pas sphériques.

Par ailleurs, l'indice imaginaire de glace n'est pas très élevé non plus et la forme n'importe pas en émission. Donc glace ou eau liquide , cela change peu les choses .

C'est pas ça le pb (même si lui, il trouve que les pouièmes de différence sont importants)

Le pb, c'est pltôt de savoir si il y va y avoir davantage de nuages en Arctique ou pas. Parce que ces nuges, réchauffent , même les nuages bas si c'est audessus de la glace.

Ensuite avec la diminution probable de l'englacement d'été, l'albédo va fortement chuter mais le flux d'évaporation va nettement augmenter puisqu'il y aura de l'eau libre disponible. Les nuages devraient être sans doute plus nombreux ce qui compenserait partiellement la diminution d'albédo due à ladisparition de la glace.

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Des gouttes surfondues à -30°C , on connait depuis longtemps dans des nuages des latitudes moyennes . Il suffit qu'ils soient suffisamment hauts. De satellite, on détecte aussi (depuis au moins 10 ans) la présence de particules sphériques à des températures aussi basses que ça. Or, les cristaux de glace ne sont pas sphériques.

Cela semble, d'après cette équipe du NOAA, surprenant dans l'Arctique...
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  • 2 weeks later...

Pourquoi l'Europe s'est réchauffée trois fois plus vite que la moyenne de l'hémisphère nord ?

Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe

http://www.agu.org/pubs/crossref/2005.../2005GL023624.shtml

Abstract

Europe's temperature increases considerably faster than the northern hemisphere average. Detailed month-by-month analyses show temperature and humidity changes for individual months that are similar for all Europe, indicating large-scale weather patterns uniformly influencing temperature. However, superimposed to these changes a strong west-east gradient is observed for all months. The gradual temperature and humidity increases from west to east are not related to circulation but must be due to non-uniform water vapour feedback. Surface radiation measurements in central Europe manifest anthropogenic greenhouse forcing and strong water vapor feedback, enhancing the forcing and temperature rise by about a factor of three. Solar radiation decreases and changing cloud amounts show small net radiative effects. However, high correlation of increasing cloud-free longwave downward radiation with temperature (r = 0.99) and absolute humidity (r = 0.89), and high correlation between ERA-40 integrated water vapor and CRU surface temperature changes (r = 0.84), demonstrates greenhouse forcing with strong water vapor feedback.

Un article explicatif vraiment excellent sur RealClimate :

Busy Week for Water Vapor

http://www.realclimate.org/index.php/archi...vapor/#more-212

Measurements from a network of six Alpine surface budget stations indicate that the primary radiative forcing driving the increase in surface temperature is an increase of downward clear sky infrared from the atmosphere to the surface. The annual average increase in this term is nearly 4 Watts per square meter between 1995 and 2002. Net cloud effects are relatively less important. Moreover, the increase in downward clear sky infrared is correlated with an increase in atmospheric temperature, and also an increase in the water vapor content of the surface layer of the atmosphere. Using a simple radiation model, the authors conclude that about a third of the increase in downwelling infrared is due to the increase in atmospheric temperature,and the rest is due primarily to an increase in the water vapor content of the low level atmosphere.

This happens because water vapor is a greenhouse gas, so increasing the water vapor content makes air act more like a perfect blackbody emitter, if the air is not already opaque to infrared. In this case, increasing water vapor content will make the air a better absorber and emitter, even if its temperature doesn't change. From this result we learn that: (a) observations confirm the expected increase of low level water vapor content with temperature , and ( b ) the increase in water vapor accounts for the bulk of the increase in downward radiation heating the surface

The authors then subtract off the part of the downward infrared radiation increase attributable to temperature and water vapor increase, and thus estimate the part due directly (as opposed to via feedbacks) to the increase in anthropogenic greenhouse gases such as CO2. They estimate this to be about one third of a Watt per square meter.

It is striking that the changes in the Earth's surface radiation budget due to anthropogenic greenhouse gases are so profound that they can be directly observed on a regional scale, over such a short time period. So far, so good. Physics seems to be working as it should, and climate scientists seem to be basing their understanding of climate change on rock-solid physical principles. The authors do not fall into the trap of assuming that water vapor is the root cause of the observed warming. They understand fully well that water vapor acts as a feedback to amplify forcing due to CO2 increase, and make this clear in their paper. This paper does not, however, deal directly with the problem of whether European warming can be attributed to CO2 increase. It only shows that, whatever mechanism is causing the warming of the atmosphere in this region, the surface warming is being amplified by low level water vapor feedbacks.

Réchauffement ....> rétro-action de la vapeur d 'eau

Vraiment intéressante cette étude. "Sceptiques", attention à en bien comprendre le sens... default_wink.png/emoticons/wink@2x.png 2x" width="20" height="20">

" (...) sound article was published with the unfortunate sub-header "Water vapour rather than carbon dioxide in the atmosphere is the main reason why Europe's climate is warming, according to a new study." This gives the casual reader the erroneous impression that the study concludes CO2 is unimportant. It feeds the old, discredited skeptics' notion that the water vapor greenhouse effect is so dominant that there's no need to be concerned about CO2. "

[une vieille notion sceptique discréditée : la vapeur d'eau est tellement dominante qu'il est inutile de se préocupper du CO2 ]

All of this was relatively harmless, but all the coverage missed the boat in the same way. Press reports failed to note that the water vapor feedback discussed in Philipona et al. is not the same water vapor feedback usually discussed in connection with global warming. It is instead a surface water vapor feedback which adds additional surface warming on top of the usual things we talk about. The effect is already incorporated in the climate models used in IPCC forecasts, but the new observational study will be useful as a reality-check. (...)

For the most part, surface temperature changes are determined by perturbations to the top-of-atmosphere budget, and the surface budget is just dragged along, accomodating itself to whatever changes in surface temperature are demanded in order to be able to satisfy the top of atmosphere budget. It is impossible to understand the greenhouse effect without thoroughly understanding this point.

I shall try to explain. In equilibrium, the Earth must lose as much energy out the top of its atmosphere as it gains by absorption of Solar energy. This is the principle of energy balance that controls the climate of all Earthlike planets. Currently our planet is out of equilibrium because the rapid rise of carbon dioxide is more than the slow response time of the oceans can keep up with; even if CO2 increase were halted today, the planet would continue to warm for a while as it comes into equilibrium.

Planets only have one way of losing energy, which is by infrared radiation to space, often called "Outgoing Longwave Radiation," or OLR. The next piece of the story is that convection is always lifting air from the ground to high altitudes in the troposphere, causing the air to cool by expansion as it rises. This is the basic reason that temperature goes down with height in the troposphere. Convection and other dynamical heat transport mechanisms link together all the air in the troposphere, so that, to a first approximation, the whole troposphere can be considered to warm and cool as a unit. It doesn't matter much where you put in or take out heat from the troposphere.. It is mainly the net energy budget of the troposphere that counts.

Now, if the atmosphere contains a greenhouse gas, the atmosphere will be partly opaque to infrared trying to escape from the surface. Infrared from the surface will be absorbed before it gets very far. As a result, the infrared that escapes to space comes more from the higher, colder parts of the atmosphere. Since infrared radiation increases like the fourth power of temperature, the radiation from these layers is much feebler than the radiation that would escape from the ground. On the other hand, the radiation into the ground comes predominantly from the warm layers nearest the ground.

RCWaterFig1.jpg Canicule 2003, Paris

(...)If we increase the concentration of a greenhouse gas (say, CO2), then that makes more of the atmosphere opaque to infrared, and so the infrared escapes from yet higher and thinner and colder parts of the atmosphere. This would reduce the OLR, if the temperature of the atmosphere were held fixed at its original value. The planet would then be receiving more Solar energy than it gets rid of. Solar energy is primarily absorbed at the surface and communicated to the troposphere by surface heat fluxes. This energy input stays the same, while the reduction in OLR has reduced the rate at which the atmosphere is losing energy. As a result, the troposphere must warm until the top of atmosphere energy budget is brought back into balance. Remember that the whole troposphere warms more or less as a unit. That means that the air near the ground must warm along with the rest. In this way, we see that the warming of the entire troposphere can mostly be inferred just by thinking about the top of atmosphere budget, without bringing the surface budget into the picture in any detail.

So far, all we need to know about the surface budget is that all the energy absorbed at the surface eventually makes its way into the atmosphere.

We are not done yet. We still have to say how this change in the tropospheric temperature translates into a change in the temperature of the solid underlying surface on which we live. This is where the surface energy budget comes in. The complication here is that, while the top-of-atmosphere balance has only one loss term (the infrared), the surface has many ways to exchange energy with the overlying atmosphere:

- Sensible heat flux (warming or cooling air in immediated contact with the surface and then mixing it aloft by turbulent motions)

- Latent heat flux (cooling the surface by evaporation)

- Infrared heat flux (cooling by emission of infrared by the surface, and warming by absorption of downelling infrared from the atmosphere)

...latent heat flux tends to be the dominant term, because evaporation is such an effective way of transferring heat.

The buffering of the surface budget by evaporation limits the leverage of the surface budget on surface temperature over much of the rest of the globe, though not to the same extent as in the tropical oceans.(...) the top of atmosphere budget determines the warming of the low level air temperature, while the surface budget determines the difference between the air temperature and the surface temperature.

(...) If the Sahara were made moister (as it was some thousands of years ago) the surface would cool regardless of what CO2 is doing. Conversely, if the moister parts of North America dry out in response to CO2 increase, the reduction in soil moisture will compound the surface temperature increase. Getting back to the implications of Philipona's results, since Europe is not in a completely evaporation-dominated regime, the downwelling infrared increase could possibly allow the surface temperature to warm more rapidly than the air temperature, compounding the general global warming driven by CO2.

RCWaterFig2.jpg

The water vapor involved in the effect of water vapor on infrared downwelling to the surface is almost a completely separate issue – a different water vapor, as it were – from the water vapor we speak of when talking about the role of "water vapor feedback" in the context of global warming.. Water vapor feedback of the latter sort is a consequence of the effect of water vapor on the top of atmosphere radiation budget. (...)

Ci-dessus l'article en question
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Ci-dessus l'article en question

Mais the Fritz, c'est avec Pierre-Ernest que j'ai eu une discussion sur le sujet, pas avec toi.

Je te cite :

1° je parle de la conclusion du document que tu m'as conseillé de lire

/index.php?s=&showtopic=17529&view=findpost&p=360482'>http://forums.infoclimat.fr/index.php?s=&a...st&p=360482Hypothèse 1 : Pierre-Ernest = the fritz

Hypothèse 2 : tes propos ne sont pas cohérents

?

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