From AGU highlights, measurements from 2002 to 2009 show short term feedback still subject to short-term climate variability, long term feedback still in the realm of models.
Measuring the effect of water vapor on climate warming
Water vapor is a potent greenhouse gas. In the atmosphere, the concentration of water vapor increases with the temperature, setting up a powerful positive feedback loop. This water vapor feedback is the strongest known positive feedback, with the potential to roughly double the effect of warming caused by other sources. Determining the exact strength of the water vapor feedback, then, is incredibly important to limiting uncertainty in future climate change projections.
From 2002 to 2009, an infrared sounder aboard NASA’s Aqua satellite measured the atmospheric concentration of water vapor. Combined with a radiative transfer model, Gordon et al. used these observations to determine the strength of the water vapor feedback. According to their calculations, atmospheric water vapor amplifies warming by 2.2 plus or minus 0.4 watts per square meter per degree Celsius. This value, however, is only the “short-term” feedback—the strength of the feedback as measured during the observational period. This value is subject to short-term climate variability. The true value of the feedback, the “long-term” value, is what the short-term observed values should trend towards when given enough time.
Using a series of climate models, the authors estimate the strength of the long-term water vapor feedback. Extrapolating from their short-term observations they calculate a long-term feedback strength of 1.9 to 2.8 watts per square meter per degree Celsius. They find that most models get to within 15 percent of their long-term value within 25 years. The accuracy of calculations, then, could be improved with a longer set of observations.
Source: Journal of Geophysical Research-Atmospheres, doi: 10.1002/2013JD020184, 2013 http://onlinelibrary.wiley.com/doi/10.1002/2013JD020184/abstract
Title: An observationally based constraint on the water-vapor feedback
Authors: N. D. Gordon: Lawrence Livermore National Laboratory, Livermore, California, USA; A. K. Jonko: National Center for Atmospheric Research, Boulder, Colorado, USA; P. M. Forster: School of Earth and Environment, University of Leeds, Leeds, UK: K. M. Shell: College of Earth, Ocean and Atmospheric Sciences, Oregon State University, Corvallis, Oregon, USA.
Abstract:
The increase in atmospheric concentrations of water vapor with global warming is a large positive feedback in the climate system. Thus, even relatively small errors in its magnitude can lead to large uncertainties in predicting climate response to anthropogenic forcing. This study incorporates observed variability of water vapor over 2002–2009 from the Atmospheric Infrared Sounder instrument into a radiative transfer scheme to provide constraints on this feedback. We derive a short-term water vapor feedback of 2.2 ± 0.4 Wm−2K−1. Based on the relationship between feedback derived over short and long timescales in twentieth century simulations of 14 climate models, we estimate a range of likely values for the long-term twentieth century water vapor feedback of 1.9 to 2.8 Wm−2K−1. We use the twentieth century simulations to determine the record length necessary for the short-term feedback to approach the long-term value. In most of the climate models we analyze, the short-term feedback converges to within 15% of its long-term value after 25 years, implying that a longer observational record is necessary to accurately estimate the water vapor feedback.
There’s nothing we can do, it’s too late to stop the warming accelerating. We are on a warming track and the feedbacks are positive, so it is just a matter of time before we all burn up. We might as well go on burning fossil fuels as a fast as we can then and enjoy ourselves in the warmth. All those plants will love it, so lots of cheap food as well. What’s not to like.
What is worst than being cold and hungry? Being wet, cold and hungry.
According this study, the next time I’m out hiking I’ll camp by a waterfall to stay warm.
Bill Illis wrote
They were also careful to ensure that they included aerosol fudge factors which they could fine tune to always agree with temperature data, while still maintaining high feedbacks.
So a summer with only cloudy days will make it a hot one. I don’t think you can attract many tourists with that slogan.
Welcome to Florida the cloudy State.
http://blakerealestate.com/wp-content/uploads/2012/03/welcome-sign-at-the-Florida-state-line.jpg
How would you warm the Oceans with constant cloud cover?
http://www.klimaatfraude.info/images/sverdrup.gif
What surface temperature would Earth have with a 100% cloud cover. Would the temperature be as stable as the Venus surface temperature ?
Positive feedback V negative feedback. Which one wins out during our paleo observations?
If water vapour is a potent greenhouse gas how come dry deserts are hotter than wet rainforest of the same latitude and altitude??????????????
Mike Borgelt—
You forgot that all cloud contains latent heat held in the water vapour. This is a lot of heat. And having flown over the Indian Ocean many times at night, the convective cloud is still there and very active.
Berthold, very few people are going to read 25 pages of poorly formatted text.
I am not sure about how can I introduce my thoughts in here. I feel a sense of cautiousness when approaching debates on human impact in the global ecosystem due to the strong positions taken that can react in a somehow “fighting” mode. I am in a transition period (job seeking) and opening my thoughts to scrutiny it is a challenge than can well take me away from building bridges instead of creating them. But any way I would like to add my input in this debate by incorporating what for me it my be the role played in the models by the lack of understanding on the mechanisms of resilience working in the global environment. Which under my point of view might be a key issue creating distortion in our interpretations of data getting incorporated in the predictive models based on linear patterns. Since I have already created posts in my blog about it I would like to leave here two links in order to extend my point for those interested and with no other intention that join the debate and expand my perception of things through constructive feedback.
http://diegofdezsevilla.wordpress.com/2014/02/25/resilience-in-our-environment/
http://diegofdezsevilla.wordpress.com/2014/02/21/resilience-in-our-models/
The oceans are warmed by solar SW radiation. The DWLW radiation (IR from greenhouse gases) is so efficiently absorbed by the water molecules on the surface that effectively the surface becomes opaque to IR. The surface water molecules absorb the photons and the energy is converted to kinetic energy, causing the water molecules to vibrate vigorously.
The surface water molecules eventually have enough energy to overcome the cohesive force (surface tension) and the short range attractive forces (Van der Waals) that bind them to the rest of the water molecules. This energy of phase change (latent heat) is efficiently achieved by the IR radiation.
The molecule enters the vapour phase and is borne on winds and convection currents into the atmosphere. It contains the energy provided by the IR radiation as well as the energy it initially possessed as a water molecule in the surface of the ocean. The ocean has lost some heat.
As the air containing the water vapour molecule cools, condensation will occur, releasing the latent heat in the atmosphere.
The energy required to achieve evaporation is massive compared to the energy required to raise the water temperature, so the efficiency of IR absorption achieves much more evaporation than simply raising the temperature of the sea.
Greenhouse gas DWIR radiation facilitates evaporation and cooling of the oceans.
RS says:
March 11, 2014 at 5:20 pm
Seeing that atmospheric CO2 was over 1000 and as much as 8000 ppm in dinosaur days without the planet going Venus, I would say that there is no strong positive feedback loop.
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The atmosphere of Venus is 95% CO2 and is two orders of magnitude more massive than the Earth’s atmosphere.
Thus for Earth to go Venus, CO2 concentration (relative to Earth’s current atmosphere) would have to increase by 95,000,000 ppm. Yes, that is 95 million parts per million.
There should be no arguments. We have an observable situation on this planet that tells us how water vapor, or its absence, affects temperature. Compare the diurnal temperature range of the central Sahara (~85 F) with the diurnal range of the wet tropics (~ 25 F). Note that the effect of increasing water vapor is a moderation temperatures. This means that adding water vapor to dry climates will moderate extremes and adding water vapor to wet climates will only increase rainfall. But this is observation, and the climate modelers hate observations that refute their cherished models. They turn a blind eye to anything that contradicts AGW theory. If they respond to such observations at all (and usually they do not) their response is an effusion of theory, as if theory nullifies observations. For them it does.
It is ironic that someone who embraces the climate models should cite the engineering disciplines as support, because these universally reject the GCM’s as egregiously contrived.
A strongly positive water vapour feedback is highly unlikely because such feedback would cause frequent climate temperature spikes and the climate would be unstable. There would be localised runaway warming in the tropics. The reverse is true. The climate of our planet has been remarkably stable for long periods. The predicted hot spot over the tropics has never been observed. The large increase in humidity has not been observed. There has been a small increase at the surface and decreases in the middle and upper troposphere humidity.
The small temperature rise allegedly blamed on GHG could be explained by CO2 alone so there is no evidence to support a positive water vapour feedback.
I understand the logic being proposed but observation suggests that the process is capped by other factors such as the mechanism I proposed above. Furthermore, warming is likely to speed up a number of heat removal processes such as convection to the upper atmosphere and lateral transfer of heat away from the equator. The dynamics of the system change and I doubt if the models simulate that.
Where is some sense of geological history? Let’s assume that at many points in Earth’s long history, we’ve had a warm climate with high humidity levels at the higher temperate zone latitudes. Did this create a Venus style planet? No? Why not? Obviously, positive feedback stops being positive at some point, and turns negative. This should be an assumed axiomatic truth. Now, could we please look to see if we can learn the reasons and switchover point(s), and stop with the boring alarmist BS?
I may be wrong, but the last I understood, clouds are not water vapor, the are in fact liquid, however tiny the cloud droplet. Clouds are liquid, suspended by convective currents at the elevation in the atmosphere where condensation occurs. In addition to expending energy in supporting billions of tons of liquid water against gravity, thermal exchanges between the earth and space are being enhanced in multiple ways. Nature is truly amazing.
The Gordon et al paper reminds me of the (apocryphal) story that scientists, using impeccable mathematics, have proven that a bumblebee absolutely and unquestionably cannot fly:
http://www.snopes.com/science/bumblebees.asp
Here the authors “prove” that the so-called “Global Average Temperature” should be increasing rapidly as a result of “water vapor feedback”, yet the real atmosphere, like the bumblebee, stubbornly refuses to cooperate.
One of these two stories of self-deluding scientists is all too real.
Steven Mosher says:
March 11, 2014 at 7:07 pm
Box of rocks.
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Steven Mosher – I seriously doubt that. Radiative transfer to me means the conversion of radiation to sensible heat.
Antenna design has it roots in Maxwell’s equations. Yeah, that portion of Engineering Physics 2 that lasted about two weeks, only to be revisited by EE’s a couple of years later as a class over 2 semesters.
There is a a huge difference between converting electrical energy into radio waves that are propagated by an antenna. Just look at an array for a SPY-1(series) radar whose latest iteration is used for ballistic missile defense. In terms of radiation a whole different set of problems to solve in terms of radiation – low frequency at that.
When clouds form latent heat in the form of radiation is released – this we know. Whether the energy released is in a form that can do ‘work’ is another question and whole different set of equations that (I bet) are largely or at least very poorly developed…
michael hart says:
March 12, 2014 at 4:15 am
Berthold, very few people are going to read 25 pages of poorly formatted text.
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….and in about the middle was blood sugar and insulin levels. Another cut and paste gone awry.
If increased water vapour gives higher temperatures, why aren’t the tropics warmer than the deserts?
I suspect much of the whole issue on global warming revolves around this issue. It is likely that with greater c02 the temperatures in temperate and polar latitudes increase to a point, but the tropics stay the same, due to negative feedback and saturation with water vapour and the effect of thunderstorms, evapotranspiration, and clouds. This also means there is a buffering effect in the atmosphere, and runaway greenhouse is very unlikely.
What you do also probably get is polar migration of climate zones, so deserts move poleward (e.g. Perth is getting drier) and tropics also move poleward (eg Darwin and Brisbane, both of which do not show warming in recent decades, due to the increased water vapour and negative associated feedback).
MaxS
Venus surface atmospheric pressure is 90atmospheres (earth atmospheres). Venus has an albedo of 0.67, more than twice ours. It receives twice our solar radiation so actually looses more than twice our radiation to space through albedo. Very little radiation actually makes it to the surface. Pictures from the Russian Venus probe showed a red landscape due to lack of light. It was then crushed. the high temperature on Venus is due to adiabatic atmospheric compression. The atmosphere is 70Km deep,( ours 12-15), the lapse rate is just over 10C/km giving you the 700+K surface temperature.
Not GHE at all.
thingadonta
rainforest is cooler because of the water vapour. evapouration requires latent heat and a lot of it, plus the clouds formed, convective heat removing clouds, reflect heat from their white tops. So less heat for the surface.
@johnmarshall
You point out many differences between Earth and Venus, but except for the solar radiation differences due to orbital distance from the sun, don’t you think most of those differences would diminish significantly if you suddenly added the quantity of CO2 in Venus’s atmosphere to Earth’s Atmosphere?
” in lab experiments at least, water vapor has been shown to reduce, not increase, the greenhouse effect of CO2″
This is effective sequestration. CO2 averages 2% of water in the atmosphere by mass, but CO2 is nearly three times as heavy and spectral florescence is by molecule, not by mass. So let’s say CO2 .7% by molecules. The absorption spectra overlap. Water is strongly concentrated near the surface. Who gets the photon?
We think of the greenhouse effect as bottom up but really half of it is top down from incoming solar radiation. Water fluoresces over many incoming spectra but CO2 is marginalized by its spectral properties on this side of the ledger.
http://geosciencebigpicture.com/2014/02/23/a-graphic-study-of-the-greenhouse-effect/
Water vapour is not a GHG and it is simple to demonstrate.
Using scientific principles you first look at an area with little water vapour, say the Sahara Desert. The daily temperature can vary by up to 35C – baking hot in the day and freezing overnight. This also a good way to demonstate the effect of GHGs – pretty much zero! GHGs will be much the same over the Sahara as the rest of the world. All one can say about GHGs is that they may make the hottest part of the day slightly hotter, but the effect will soon disappear once the sun is lower in the sky.
Although the temperature ranges over most of the world would be less it demonstrates that the effects of GHGs are lost overnight so any warming must be started fresh EVERY DAY.
Now take a hot place with a lot of water – say the Brazilian rain forest. Here the daily temperature range is 2C to 5C, with an average temperature of 25C. The effect of water vapour has a dramatic effect on the climate. Note that the water causes cooling during the day and warming during the night. By definition this means it is not a GHG. It acts more like an insulator – call it ‘the Thermos Effect’!
This is further demonstrated by looking at the annual change in temperature. The rain forest varies by only 2C over the year but the Sahara goes from daily maximums of 40C to 15C, further showing the lack of effect of GHGs.
Finally, consider that the Sun heats the Earth by 390C. Easy to work out : take the temperature of the universe [-270C] and add the hottest temperature on the Moon [120C]. The thin layer of atmosphere has to drop this temperature by over 80C, mostly by water vapour. If water vapour was a GHG the oceans at the equator would be boiling!
Also note that 80C is a LOT of cooling. I think that plus or minus 3C on the current global temperature would cover the temperature of Earth for almost all of the past 4 billion years. Small variations in water vapour could have a large effect on global temperatures.
To anticlimatic,
You are confusing the effects of evaporation and condensation with the effects of radiative transfer of energy to space. Strong evidence of the “greenhouse effect” of water vapor is observed at the poles where concetrations are lowest but vary by orders of magnitude seasonally. The resistance to OLR at TOA is strongly related to this variation. http://www.kidswincom.net/CO2OLR.pdf.