What Do We Think About Climate Change

Guillermo · Oct 10, 2010

Boston said: ↑

ok
so given that the deniers are also constantly spewing about how water vapor is the major contributing green house gas then it stands to reason that if water vapor is decreasing and temp is still increasing then there must be another factor involved. Like CO2 for instance, specially since the rise in CO2 corresponds perfectly with the rise in temp.

kinda looks like you shot yourself in the foot on that one Guillermo

want to try again

ps
just out of curiosity what does it pay to be an oil and gas internet shill Guillermo. There isn't really any logical reason why anyone would so consistently embarrass themselves like this unless they were getting paid for it. You have been exposed to many times presenting deceptive or misrepresenting data at this point and it just begs the question, why?
Click to expand...

Your comments only exhibit once again the enormity of your ignorance and the deepness of your idiotice.

As always you are incorrectly assuming you know why I post what I post (and you are not the only one here), which you don't -even remotely- just making a fool of yourself with your illiterate commentaries.

Perhaps you could try to learn some basic physics before ridicuolously commenting.

Boston · Oct 10, 2010

OK find the flaw again

Guillermo said: ↑

Atmospheric relative humidity has been decreasing from at least 1950, as per the NOAA data.

First image is for the 1000 mb level and second one for 300 mb (whole globe)
Click to expand...

Guillermo can you maybe explain to the group what the difference between relative and specific humidity is without looking it up

then please explain what happens to specific humidity when you raise temp yet keep relative humidity roughly the same or even a bit less

also how does the equilibrium vapor pressure play into the calculations

my bet is you have no clue and are just mindlessly repeating something you got from the oil and gas PR campaign

also why you have chosen such a limited data set were data from only two MB ranges is available when much more complete data is available

just curious

love
B

deal is your incorrect about your assumptions based on incomplete data
again

your attempts to ridicule and insult the opposition rather than actually be able to present any rationally cohesive argument are obvious

it might bear repeating at this point that your complete inability to present a cohesive and working counter theory incorporating the same or greater level of research as that of Rapid Global Climate Shift is glaringly apparent and your only response is to complain about the one working theory we do have

basically your nipping at heals while the science runs off ahead of you, so far you are simply unable to comprehend nuances of a myriad of particulars and instead randomly posting things you mistakenly believe question the theory.

Boston · Oct 10, 2010

OK readers lets begin to look a the vast quantities of data that specifically show an increase in overall atmospheric humidity

you might want to read along G
might help you understand some of the basics

Busy Week for Water Vapor

— raypierre @ 21 November 2005

It’s been a busy week for water vapor, and I have two recent papers to discuss. The first is the paper "Anthropogenic greenhouse forcing and strong water vapor feedback increase temperature in Europe" by Rolf Philipona et al. (GRL, 2005, subscription required for full text), which has attracted a certain amount of media attention. The overall goal of the paper is to understand, from a physical standpoint, why European temperatures have been increasing three times faster than the Northern Hemisphere average. It focuses on the changes between 1995 and 2002, over which time good surface radiation budget observations are available. The paper reports some results on the role of large scale circulation changes (which they conclude are minor) but I’ll concentrate on the results relating to water vapor.

The most interesting result may be summarized as follows. 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. This is not in bad agreement with estimates from detailed radiation models run by the authors, which say that the change in surface radiation due to the 12ppm CO2 increase between 1995 and 2002 should be about one fourth 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.

The accuracy of the media coverage of Phillipona et al. is decidedly mixed. The BBC got the scientific story straight (warming due to water vapor amplifying anthropogenic effects, everything working as it should, no worries about the physics, mate.), but their otherwise 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. National Geographic is a little breathless: " The latest villain on global warming’s most-wanted list is all wet—and a little surprising. Water vapor, experts say, is the culprit behind Europe’s rapidly rising temperatures." However, they get the basic scientific story straight, quoting Philipona as saying "It is an experiment that clearly shows which factors are driving the higher temperatures. It is not the clouds, not the sun, not the aerosols. It is the increased greenhouse gases and the strong water vapor impact." UPI is probably the worst of the bunch. They state "Swiss scientists say Europe’s recent rapid temperature increase is likely due to an unexpected greenhouse gas: water vapor." Unexpected? If they were readers of RealClimate, they’d know better.

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.

Phillipona et al. analyzed trends in the energy budget of the Earth’s surface. While this is definitely an aspect of climate change, it comes as a surprise to many that the surface energy budget plays a decidedly secondary role in climate change compared to the top-of-atmosphere energy budget. The fact is, that even if the diligent Swiss authors of this paper had found that increasing CO2 contributed nothing to the changes in the surface budget, this would have in no way contradicted our understanding of the way anthropogenic greenhouse gases influence climate. 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. Even the authors of Phillipona et al. seem to be a little fuzzy on this matter. They seem to think they are looking at the same water vapor feedback discussed in various review articles on the subject (e.g. Held and Soden (Annu. Rev. Energy Environ., 25, 441– 475. (2000)), Pierrehumbert et al. ("On the Relative Humidity of the Earth’s Atmosphere" in The General Circulation, T. Schneider and A. Sobel, eds. Princeton U. Press 2005,) Pierrehumbert (Subtropical water vapor as a mediator of rapid global climate change. . in Clark PU, Webb RS and Keigwin LD eds. Mechanisms of global change at millennial time scales. American Geophysical Union:Washington, D.C. Geophysical Monograph Series 112, 394 pp1999), and the RealClimate article on the subject). but they are not. 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.

This situation is illlustrated in Figure 1, showing actual values of fluxes which I computed for a sounding over Paris during the August heat wave of 2003 (with an idealized water vapor profile having 80% relative humidity near the ground and 50% aloft). The red arrows in this figure originate at the mean altitude from which radiation escapes upward or downward. Because the radiation to space and the radiation to the ground come from different places, increasing the greenhouse gas concentration of the atmosphere would affect the two radiations in different ways.

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)

with latent heat flux tends to be the dominant term, because evaporation is such an effective way of transferring heat. In fact, in warm, wet places like the Tropical Pacific Ocean, the evaporative heat transfer is so effective that all the surface budget tells us is that the surface temperature must stay quite close to the overlying air temperature. In a case like this, we don’t even need a detailed surface heat budget to say what the surface temperature change is — it is just dragged along with the tropospheric temperature increase. Changes in the surface budget instead affect the amount of evaporation needed to close the budget, and hence affect the precipitation rather than the temperature. 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 preceding reasoning does not mean that changes in the surface budget cannot affect the surface temperature. The right way to view the system is that (approximately) 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. There are many cases where this could further modulate the primary climate change, adding to or decreasing the primary top-of-atmosphere driven warming. This is particularly the case when a formerly wet land surface dries out. For example, the hot Sahara sands are around 10 degrees C warmer than the overlying air in the daytime, because in the absence of moisture the relatively inefficient sensible and radiative heat transfers need to have a pretty large temperature difference to work with in order to get rid of the necessary amount of heat. This is also why a dry sidewalk (pavement, to UK readers) gets very hot on a hot summer day. 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. Whether or not this happens depends in large measure on how evaporative and sensible heat fluxes adjust. This aspect of the problem was not treated by the paper. Philipona et al find that the observed downward radiation increases by roughly 2.7 Watts per square meter over and above what would be expected from the air temperature increase alone. This would lead to a surface warming of about six tenths of a degree C if it were balanced entirely by an increase in surface infrared cooling. Sensible heat flux would bring the warming down by about a factor of two. Evaporative heat flux would bring the warming down yet more, but at the expense of increasing the evaporation and aggravating the drying of soils. These climate changes are not inconsequential, especially in view of the fact that they have taken place over a relatively short period and come on top of the "normal" global warming driven by the top-of-atmosphere balance.

To see why the anthropogenic greenhouse effect does not, however, rely on the direct perturbation of the surface energy budget by greenhouse gas changes, let’s consider an idealized limiting case. Suppose that the lowest dozen meters or so of the atmosphere is so full of water vapor or cloud water that it acts like a perfect black body. It is as opaque as it can be to infrared. Now suppose that we double the atmosphere’s CO2 content. This doesn’t increase the infrared emission to the ground, because the low level air already has so much greenhouse-substance in it that it is radiating like a perfect blackbody, whose emission is determined by its temperature alone. It is radiating as much as it possibly can, for its given temperature. In radiative transfer-speak, its emission is "saturated." Furthermore, since the low layer is opaque to infrared, the CO2-caused change in downward emission aloft does not reach the ground. Does that mean there can be no further global warming in this case? No! What happens is that the increase in CO2 throws the top-of-atmosphere budget out of kilter, forcing the whole troposphere to warm up to bring the planet back into balance. Convection links the whole troposphere, which means the low level air warms up. The warming of the low level air, in turn, increases the flux of energy into the ground by all three of the mechanisms enumerated previously. In particular, the downward infrared flux increases because the air itself has become warmer — not because it has become more optically thick in the infrared. The increase in downward flux then communicates the warming to the surface. As Phillipona et al. show, the real midlatitude European boundary layer is not perfectly opaque to infrared, so increases in water vapor content or CO2 can directly increase the infrared heating of the surface. This is very interesting, but it is in no way essential to the anthropogenic greenhouse effect.

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. Water vapor near the surface has very little effect on this. Making the surface layer of the atmosphere a more effective infrared absorber/emitter has little influence on the infrared upwelling into the rest of the atmosphere because the temperature of the ground differs little from the temperature of the overlying air; one is just replacing one radiating surface with another radiating surface of practically the same temperature. In contrast, the relatively small quantities of water vapor aloft have a much greater effect on the top-of-atmosphere budget, because they increase the infrared opaqueness of layers of the atmosphere that are much colder than the surface; they block the infrared flowing upward from the warmer parts of the atmosphere, and replace it with "new" infrared emission from the cold layer.

That brings us to the second of the two recent water vapor papers, which is perhaps the more important of the two, though the subject matter it treats is less novel. . This one ( B. J. Soden, D. L. Jackson, V. Ramaswamy, M. D. Schwarzkopf, X. Huang, Science 310, 841 (2005); October 2005 (10.1126/science.1115602)., subscription required for full text) has been more or less ignored by the media. Soden et al. deal with the aspect of water vapor feedback that affects the top of atmosphere radiation budget. The analysis consists in using various satellite observations to compare the behavior of mid to upper tropospheric water vapor between a general circulation model and reality. The analysis is carried out for the period 1982-2004, corresponding to the period of satellite data availability. The basic technique is the "model to satellite" method, in which the model temperature and humidity are used to directly simulate the brightness of radiation that would be observed by satellites looking at the atmosphere in various wavelength bands. By choosing satellite observations that are sensitive to the higher-altitude water vapor distribution, one can zero in on how well the model is doing in these all-important regions. Because of the relatively short period of the comparison, this exercise should not be regarded as an attempt to detect a trend in atmospheric water vapor and compare it with models. Rather, it is a check on whether the model does the same thing to upper layer water vapor as the real world, under varying year-to-year conditions (which do contain a trend over this period, as well as other things, e.g. El Nino).

By examining infrared satellite data, Soden et al. find that upper-level moisture increases in warmer conditions, in much the same way as predicted by the model. Further, by artificially suppressing moisture changes in the computation of the synthetic satellite data, they decisively reject the hypothesis that the atmospheric upper layer water content stays fixed as temperature changes. Synthetic satellite data computed on the basis of this hypothesis look nothing at all like the real thing. The authors take their analysis even further. Because the radiation measured by the satellites depends both on moisture and temperature,there is the possibility that faults in the climate model’s upper level temperature predictions might be leading to spurious agreement with the infrared satellite data. To rule this out, they make use of microwave satellite data that is sensitive to the mid to upper tropospheric temperature, in order to formulate a diagnostic that is primarily sensitive to upper level moisture changes rather than temperature changes. Again, they find that the data demand that the upper troposphere get moister in warmer conditions. They conclude: "Reproduction of the observed radiance record requires a global moistening of the upper troposphere in response to atmospheric warming that is roughly equivalent in magnitude to that predicted under the assumption of constant relative humidity." This is probably the most direct evidence to date that there is nothing terribly wrong about the way general circulation models handle water vapor feedback. This is quite remarkable, given the potential role of small scale cloud processes in moistening the atmosphere. To be sure, the analysis only deals with clear sky regions, but the moisture in these regions originates in the cloudy convective regions, and so it provides a fair test. In any event, within the cloudy regions themselves, the clouds rather than water vapor have the dominant effect on the radiation budget.

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. To be sure, there is still a gap in understanding what the models are actually doing, in that it is far from clear why such complex processes boil down to a simple behavior: that the water vapor over a deep region of the troposphere changes in such a way as to keep relative humidity approximately constant. I have some ideas on this myself, but the general picture is still very much a work in progress. Meanwhile, 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.
Click to expand...

Boston · Oct 10, 2010

some of our readers may not realize the relationship between vapor and temp so I will include the following in our study on atmospheric vapor content

one of the ongoing failures of some of our long time readers (G) is an inability to comprehend this relationship, but I think most of us are able to grasp the concepts fairly quickly

in the end it should be a piece of cake to show that one graph showing what is presumably contrarian data is actually simply another sad attempt to muddle what is pretty clear and easily understood science

Water vapour: feedback or forcing?
Filed under:

— gavin @ 6 April 2005 - (Deutsch)

Whenever three or more contrarians are gathered together, one will inevitably claim that water vapour is being unjustly neglected by ‘IPCC’ scientists. “Why isn’t water vapour acknowledged as a greenhouse gas?”, “Why does anyone even care about the other greenhouse gases since water vapour is 98% of the effect?”, “Why isn’t water vapour included in climate models?”, “Why isn’t included on the forcings bar charts?” etc. Any mainstream scientist present will trot out the standard response that water vapour is indeed an important greenhouse gas, it is included in all climate models, but it is a feedback and not a forcing. From personal experience, I am aware that these distinctions are not clear to many, and so here is a more in-depth response (see also this other attempt).

First some basics. Long-wave (or thermal) radiation is emitted from the surface of the planet and is largely absorbed in the atmosphere. Water vapour is the principle absorber of this radiation (and acknowledged as such by everybody). But exactly how important is it? In terms of mass, water vapour is much more prevalent (about 0.3% of atmospheric mass, compared to about 0.06% for CO2), and so is ~80% of all greenhouse gases by mass (~90% by volume). However, the radiative importance is less (since all molecules are not created equal). One way to quantify this is to take a radiation model and remove each long-wave absorber (principally the greenhouse gases, but also clouds and aerosols) and see what difference it makes to the amount of long-wave absorbed. This gives the minimum effect from each component. The complementary calculation, using only each particular absorber in turn, gives the maximum effect. Generally these will not be equal because of overlaps in the absorbing spectra (i.e. radiation at a particular frequency can either be absorbed by water vapour or CO2).
Removed absorbers Fraction LW Rad. Forcing
absorbed Tropo. (W/m2)
None 100% 0
H2O 64 (64, RC78) -56
Clouds 84 (86, RC78) –
CO2 91 (88, RC78) -23
O3 97 (97, RC78)
Other GHG 98 -3
H2O+Clouds 34 –
H2O+CO2 47 -89
All except H2O+Clouds 85 –
All except H2O 66 (60-70, IPCC90) –
All except CO2 26 (25, IPCC90) –
All except O3 7 –
All except Other GHG 8 –
All 0% –
Instant calculation, global mean, Jan. 1, 1979 RC78=Ramanathan and Coakley (1978)
‘All’ includes aerosols, O3 and other minor gases as additional absorbers.

The table shows the instantaneous change in long-wave aborption when each component or combination of components is removed using the radiation code from the GISS GCM. (The source code is available for those who have the patience to get it to work). This isn’t a perfect calculation but it’s quick and easy and is close enough to the right answer for our purposes. (N.B. This is very similar to what was done by Ramanathan and Coakley (1978) using a single column model – their numbers are in the table for reference). Because of the overlaps, the combined changes are larger than the changes due to each individual component. Another calculation is the instantaneous radiative forcing at the tropopause, but that is complicated for clouds, O3 and Aerosols which have impacts on solar radiation as well as the long wave, so I only give that value for the ‘pure’ greenhouse gases.

The overlaps complicate things, but it’s clear that water vapour is the single most important absorber (between 36% and 66% of the greenhouse effect), and together with clouds makes up between 66% and 85%. CO2 alone makes up between 9 and 26%, while the O3 and the other minor GHG absorbers consist of up to 7 and 8% of the effect, respectively. The remainders and uncertainties are associated with the overlaps which could be attributed in various ways that I’m not going to bother with here. Making some allowance (+/-5%) for the crudeness of my calculation, the maximum supportable number for the importance of water vapour alone is about 60-70% and for water plus clouds 80-90% of the present day greenhouse effect. (Of course, using the same approach, the maximum supportable number for CO2 is 20-30%, and since that adds up to more than 100%, there is a slight problem with such estimates!).

Since we are looking at the whole of the present-day greenhouse effect (around 33 C), it is not surprising that the radiative forcings are very large compared to those calculated for the changes in the forcing. The factor of ~2 greater importance for water vapour compared to CO2 is consistent with the first calculation.

So where does the oft quoted “98%” number come from? This proves to be a little difficult to track down. Richard Lindzen quoted it from the IPCC (1990) report in a 1991 QJRMS review* as being the effect of water vapour and stratiform clouds alone, with CO2 being less than 2%. However, after some fruitless searching I cannot find anything in the report to justify that (anyone?). The calculations here (and from other investigators) do not support such a large number and I find it particularly odd that Lindzen’s estimate does not appear to allow for any overlap.

While water vapour is indeed the most important greenhouse gas, the issue that makes it a feedback (rather than a forcing) is the relatively short residence time for water in the atmosphere (around 10 days). To demonstrate how quickly water reacts, I did a GCM experiment where I removed all the water in the atmosphere and waited to see how quickly it would fill up again (through evaporation from the ocean) . The result is shown in the figure. It’s not a very exciting graph because the atmosphere fills up very quickly. At Day 0 there is zero water, but after only 14 days, the water is back to 90% of its normal value, and after 50 days it’s back to within 1%. That’s less than 3 months. Compared to the residence time for perturbations to CO2 (decades to centuries) or CH4 (a decade), this is a really short time.

Only the stratosphere is dry enough and with a long enough residence time (a few years) for the small anthropogenic inputs to be important. In this case (and in this case only) those additions can be considered a forcing. Oxidation of anthropogenic methane (which is a major source of stratospheric water) and, conceviably, direct deposition of water from increases in aircraft in the lower stratosphere, can increase stratospheric water and since that gives a radiative forcing effect, they do appear on the forcings bar chart (under “H2O from CH4“). Some scientists have argued that changes to irrigation and other land use changes (which effect evaporation) are also direct forcings to water vapour amounts, but I think it’s cleaner to think of that as an indirect water vapour response to the change.

When surface temperatures change (whether from CO2 or solar forcing or volcanos etc.), you can therefore expect water vapour to adjust quickly to reflect that. To first approximation, the water vapour adjusts to maintain constant relative humidity. It’s important to point out that this is a result of the models, not a built-in assumption. Since approximately constant relative humidity implies an increase in specific humidity for an increase in air temperatures, the total amount of water vapour will increase adding to the greenhouse trapping of long-wave radiation. This is the famed ‘water vapour feedback’. A closer look reveals that for a warming (in the GISS model at least) relative humidity increases slightly in the tropics, and decreases at mid latitudes.

How do we know that the magnitude of this feedback is correctly simulated? A good test case is the response to the Pinatubo eruption. This caused cooling for up to 3 years after the eruption – plenty of time for water vapour to equilibriate to the cooler sea surface temperatures. Thus if models can simulate the observed decrease of water vapour at this time, it would be a good sign that they are basically correct. A good paper that demonstrated this was Soden et al (2002) (and the accompanying comment by Tony DelGenio). They found that using the observed volcanic aerosols as forcing the model produced very similar cooling to that observed. Moreover, the water vapour in the total column and in the upper troposphere decreased in line with satellite observations, and helped to increase the cooling by about 60% – in line with projections for increasing greenhouse gases.

To be sure there are still some lingering uncertainties. Some recent data indicates that tropical upper tropopsheric water vapour does not quite keep up with constant relative humidity (Minschwaner and Dessler, 2004) (though they still found that the feedback was positive). Moist convection schemes in models are constantly being refined, and it’s possible that newer schemes will change things . However, given the Pinatubo results, the models are probably getting the broader picture reasonably correct.
Click to expand...

Guillermo · Oct 10, 2010

And now here the plots for specific humidity at 1000 and 300 mb, from jan 1948 to sept 2010

Guillermo · Oct 10, 2010

More or less flat trend at around 850 mb....

Boston · Oct 10, 2010

or I could take the short and easy rout and simply post the IPCC data

from chapter 3 IPCC WG1 pg 238

Surface specific humidity has generally increased after 1976 in close association with higher temperatures over both land and ocean. Total column water vapour has increased over the global oceans by 1.2 ± 0.3% per decade from 1988 to 2004, consistent in pattern and amount with changes in SST and a fairly constant relative humidity. Strong correlations with SST suggest that total column water vapour has increased by 4% since 1970. Similar upward trends in upper-tropospheric specific humidity, which considerably enhance the greenhouse effect, have also been detected from 1982 to 2004.
Click to expand...

Click to expand...

and from section 3.4.2 (p. 271, 272):

The network of radiosonde measurements provides the longest record of water vapour measurements in the atmosphere, dating back to the mid-1940s. However, early radiosonde sensors suffered from significant measurement biases, particularly for the upper troposphere, and changes in instrumentation with time often lead to artificial discontinuities in the data record (e.g., see Elliott
et al., 2002). Consequently, most of the analysis of radiosonde humidity has focused on trends for altitudes below 500 hPa and is restricted to those stations and periods for which stable instrumentation and reliable moisture soundings are available.
Click to expand...

seems pretty clear that the preponderance of data shows a clear and unmistakable rise in overall atmospheric humidity exactly as anyone with even a basic understanding of the science would expect

so for all the readers I must ask

why Guillermo, would you present data from only two specific altitudes and only one specific study which do not represent the overall findings?

or is it that you are presenting a deceptive and dishonest argument again?

I have to admit these games of "find the flaw" are truly entertaining

cheers
B

Guillermo · Oct 10, 2010

Keep on copying and pasting as much as you like, scatterbrained Weasel. You will not understand more because of that

Guillermo · Oct 10, 2010

And also keep on with your daring, ridiculous and illiterate assumptions....

Boston · Oct 10, 2010

Guillermo said: ↑

More or less flat trend at around 850 mb....
Click to expand...

sorry
but once again
you've lost another rousing round of "find the flaw"

would you care to present data and then average that data for the remaining 197 divisions of altitude in the atmosphere

only looking at 3 out of 200 readings ( taking it 50 mb at a crack over the full 1000 mb range ) isn't going to fool anyone now that I've revealed what your up to

same old same old

cherry picking data is not sound science Guillermo

wanna try another game or would you prefer to continue embarrassing yourself with this one

love
B

An independent check on globally vertically integrated water vapour amounts is whether the change in water vapour mass is reflected in the surface pressure field, as this is the only significant influence on the global atmospheric mass to within measurement accuracies. As Trenberth and Smith (2005) showed, such checks indicate considerable problems prior to 1979 in reanalyses, but results are in better agreement thereafter for ERA-40. Evaluations of column integrated water vapour from the NASA Water Vapor Project (NVAP; Randel et al., 1996), and reanalysis data sets from NRA, NCEP-2 and ERA-15/ERA-40 (see Appendix 3.B.5.4) reveal several deficiencies and spurious trends, which limit their utility for climate monitoring (Zveryaev and Chu, 2003; Trenberth et al., 2005a; Uppala et al., 2005). The spatial distributions, trends and interannual variability of water vapour over the tropical oceans are not always well reproduced by reanalyses, even after the 1970s (Allan et al., 2002, 2004; Trenberth et al., 2005a).

To summarise, global, local and regional studies all indicate increases in moisture in the atmosphere near the surface, but highlight differences between regions and between day and night. Satellite observations of oceanic lower-tropospheric water vapour reveal substantial variability during the last two decades. This variability is closely tied to changes in surface temperatures, with the water vapour mass changing at roughly the same rate at which the saturated vapour pressure does. A significant upward trend is observed over the global oceans and some NH land areas, although the calculated trend is likely influenced by large interannual variability in the record.
Click to expand...

TeddyDiver · Oct 10, 2010

Just a remark Guillermo of those last graphs of yours... According them in low altitudes the specific humidity has risen 0,2g, mid altitudes stayed the same and at higher fallen 0,03g so it says the atmospheric specific humidity has risen by ~0,17g or something...
BR Teddy

Guillermo · Oct 10, 2010

I'll comment later, Teddy. Let me now keep on with my little digression...

Boston · Oct 10, 2010

wrong again Guillermo on all counts
one would think you get tired of being so wrong so often
( going to comment later eh, not likely )

science is all about doing your homework rather than blindly cutting and pasting cherry picked data from information you don't comprehend
even just a cursory review of the data pool showed the flaw in your thinking

cheers
B

care to play again ?

Guillermo · Oct 10, 2010

Now total amount of water vapour
Credit: Climate4you
Rough trend lines are mine.

Figure:
Variations in the total column water vapour in the atmosphere since July 1983. The upper graph (blue) shows the total amount of water in the atmosphere. The green graph shows the amount of water in the lower troposphere between 1000 and 680 mb, corresponding to altitudes up to about 3 km. The lower red graph shows the amount of water between 680 and 310 mb, corresponding to altitudes from about 3 to 6 km above sea level. The marked annual variation presumably reflects the asymmetrical distribution of land and ocean on planet Earth, with most land areas located in the northern hemisphere. The annual peak in atmospheric water vapour content occur usually around August-September, when northern hemisphere vegetation is at maximum transpiration. The annual moisture peak occurs simultaneously at different levels in the atmosphere, which suggests an efficient transport of water vapour from the planet surface up into the troposphere. The time labels indicate day/month/year. Data source: The International Satellite Cloud Climatology Project (ISCCP). There is a possibility that the step-like change shown 1998-1999 to some degree may be related to changes in the analysis procedure used for producing the data set, according to information from ISCCP. Last data: June 2008. Last figure update: 14 June 2009.

Water vapour is the single most important greenhouse gas, wherefore it is interesting to note that global warming since 1978 apparently terminated in 1998, simultaneously with the step-like decrease in atmospheric water vapour content. Global climate models forecast an increasing amount of atmospheric water vapour along with global temperature increase.

Guillermo · Oct 10, 2010

Now precipitation rates (seasonal)....
Credit: NOAA
(Rough trend lines are mine)

Log in or Sign up

What Do We Think About Climate Change

Guillermo Ingeniero Naval

Boston Previous Member

Boston Previous Member

Boston Previous Member

Guillermo Ingeniero Naval

Attached Files:

global specific humidity 1948-2010 1000 mb.JPG

global specific humidity 1948-2010 300 mb.JPG

Guillermo Ingeniero Naval

Attached Files:

global specific humidity 1948-2010 850 mb.JPG

Boston Previous Member

Guillermo Ingeniero Naval

Guillermo Ingeniero Naval

Boston Previous Member

TeddyDiver Gollywobbler

Guillermo Ingeniero Naval

Boston Previous Member

Guillermo Ingeniero Naval

Attached Files:

Water vapour 1983-2008.JPG

Guillermo Ingeniero Naval

Attached Files:

seasonal precipitation rates 1948-2010.JPG

Climate change

Climate Change is Political Football, Not Just a Complex Subject

Climate Change is a Complex Subject, Not Just a Political Football

Cruising boats flee Thailand after rules change