Guest Post by Willis Eschenbach
I got to thinking again about the thunderstorms, and how much heat they remove from the surface by means of evaporation. We have good data on this from the Tropical Rainfall Measuring Mission (TRMM) satellites. Here is the distribution and strength of rainfall, and thus evaporation, around the middle of the planet.
Figure 1. Evaporation in W/m2 as shown by rainfall data from the TRMM. It takes about 80 watt-years of energy to evaporate a cubic metre of water, so a metre of rainfall per year is equivalent to an average surface cooling of 80 watts per square metre. The TRMM satellite only covers from 40° North to 40° South.
I have held for some time that the global surface temperature is restricted to a fairly narrow region (e.g. ± 0.3°C over the 20th century) by the action of emergent phenomena (see references at the end of the post). Chief among these emergent phenomena are tropical thunderstorms. My hypothesis says that when the tropical surface temperature goes over a certain threshold, that thunderstorms emerge to put a firm cap on the temperature by cooling the surface.
Thunderstorms cool the surface in a number of ways, but the main cooling method uses the exact same mechanism used by the refrigerators that keep our food cold. Thunderstorms use a standard evaporation/condensation cycle. In one part of the cycle the working fluid evaporates, cooling the surroundings. In another part of the cycle in another location, the working fluid condenses. For a refrigerator, the working fluid used to be some form of Freon, nowadays it’s some other fluid. For thunderstorms, the working fluid is water. When it evaporates at the surface, it cools the local area, and the heat is moved from the surface to the clouds and on upwards.
Now, for my hypothesis to be correct, the number and intensity of thunderstorms needs to increase quickly as temperatures go above a certain temperature threshold. In addition, the change in the resulting evaporation needs to be quite large in order to successfully control the system.
With that in mind, I made a scatterplot of sea surface temperature versus thunderstorm evaporative cooling. Figure 2 shows that result.
Figure 2. Scatterplot of 1° x 1° gridcell annual average ocean-only thunderstorm evaporative cooling on the vertical axis, in watts per square metre (W/m2) versus 1° x 1° gridcell annual average sea surface temperature on the horizontal axis.
As you can see, the thunderstorms are clearly functioning to cap the temperature. When the ocean surface gets hot, thunderstorms form and exert immense cooling power. There are some points worth noting about Figure 2.
First, the red area shows the tropics. This part of the earth is important because it is not only about 40% of the planet’s surface. In addition, just over half of all the energy absorbed by the surface of the earth is absorbed in the tropical regions of the planet. As a result, the regulation of this large amount of incoming energy by albedo control is crucial to the overall energy balance of the planet.
Next, these are annual averages. However, they are also daily averages. But during the day/night cycle in the tropics, the evaporation is by no means constant. At night the evaporation is small, some tens of watts per square metre. During the day, on the other hand, evaporation is quite large, hundreds of watts per square metre, because the strong tropical sunshine evaporates the water directly, plus the thunderstorms are largely a daytime phenomenon. This means that the peak hourly thunderstorm evaporative cooling is on the order of twice the average values shown above, up to about 600 W/m2.
Next, the cooling effect of the thunderstorms is not applied blindly or randomly. The thunderstorms only form as and when the local area is above the temperature threshold. This means that the cooling effect, which can be up to 500-600 w/m2, is always located where it is most needed, on the local hotspots.
Finally, here is the most important consideration. The timing and the amount of thunderstorms are NOT a function of greenhouse gas forcing, or of solar forcing, or of volcanic forcing, or of any other kind of forcing. As Figure 2 shows, they are a function of temperature. As long as the surface-atmosphere temperature difference is large enough, thunderstorms will form even at night when the radiative forcing is quite small.
This means that their effect will be to maintain the same temperature, regardless of reasonable-sized fluctuations in the amount of forcing. Clouds don’t know about forcing, they form and disappear based on local conditions.
And this is simply one more piece of observational support for my hypothesis that emergent phenomena regulate the temperature and maintain it within a fairly narrow range.
My best to everyone. Here in California, we have about 150% of the usual snowpack in the Sierra Nevada mountains. When it was drought, it was said to be the result of global warming … and of course, now that there is heavy snow, that is also said to be the result of global warming.
Buckle your seatbelts and keep your hands inside the vehicle, it’s gonna be a long, uphill struggle to get rid of this madness …
My best to all,
w.
My Usual Request: If you disagree with me or anyone, please quote the exact words you disagree with. I can defend my own words. I cannot defend someone’s interpretation of my words.
My Other Request: If you think that e.g. I’m using the wrong method on the wrong dataset, please educate me and others by demonstrating the proper use of the right method on the right dataset. Simply claiming I’m wrong doesn’t advance the discussion.
Some Of My Previous Posts On The Subject:
Cooling and Warming, Clouds and Thunderstorms
Data:
TRMM Data is here, see the bottom of the page for the NetCDF file.
CERES Data is here, I used the EBAF dataset.
Willis,
You wrote:
“I’m sorry, but your uncited and unsupported claim that volcanoes “have a strong global cooling effect and the effect lasts until the dust settles” does NOT constitute “evidence that the thermostat effect of thunderstorms, while real, is not sufficient to overcome the cooling effect of aerosol forcing”. Evidence is verifiable facts and observations, Thomas, not your uncited claims.”
But I did cite the evidence to support my claim. I told you the global temperature data are from UAH and the Optical Thickness data are from the following GISS sites.
GISS Global Stratospheric Aerosol Optical Thickness site:
http://data.giss.nasa.gov/modelforce/strataer/
GISS Global Stratospheric Aerosol Optical Thickness DATA
http://data.giss.nasa.gov/modelforce/strataer/tau.line_2012.12.txt
I also emailed a chart to Anthony. (I don’t know how to post an image here.)
You wrote:
“Nope. If they had, the lack of volcanoes since 1992 would have led to continual warming, but in fact the world hasn’t warmed in almost two decades.”
I disagree. There were major volcanos that increase aerosol loading, which decreased sunlight (see the GISS data) in the 80’s and 90’s but none since Pinatubo in 1992. Those eruptions clearly caused cooling, which lasted until the aerosol loading settled or rained out. We would not expect “continuous warming” after recovery from volcanic cooling. All else being equal, we would expect temperatures to recover back to their previous levels not to continue warming
As it turned out, all things were not equal. A major El Neño caused “warming” at the end of the 1990’s. I put warming in quotation marks because an El Neño doesn’t introduce more energy into the system, it just spreads around heat that had been concentrated in the wester pacific.
Nevertheless, the dramatic increase in stratospheric aerosol loading caused by El Chichon and Pinatubo are clearly evident in the GISS aerosol data and the UAH temperature data shows concurrent cooling. The mechanism is obvious, the aerosols cause less sunlight to reach the surface.
Your idea that thunderstorms act as a governor on surface temperature seems correct to me. If the surface is hot, convection causes more surface winds, the heat and wind cause more water to evaporate, causing more or larger storms, which cool the surface. Conversely, if the surface is cool, fewer or smaller storms form so the surface gets hotter.
Additional evaporation during the cumulative stage of a thunderstorm, which is caused by both increased surface wind and heat, does lower the temperature but the total heat content of the air is constant. Evaporation is an adiabatic process, meaning there is no change in total heat (called enthalpy). The cooling from evaporation is returned as sensible heat when the water vapor condenses to form cloud particles. Likewise, when air rises in a thunderstorm it cools due to expansion, but this is also an adiabatic process and the heat is returned to the surface when the air descends.
It seems to me that the only process in your thunderstorm hypothesis that actually removes heat from the atmospheric system is the fact that clouds reflect sunlight. But if clouds can cool by reflecting sunlight why wouldn’t volcanic aerosols also cool?
Anyway, it does seem to be true that your thunderstorm-governor effect is not large enough to keep the surface at a near-constant temperature when the system is forced by, for example, volcanic aerosols. Even though they lower the global temperature by only a few tenths of a degree C. The GISS data show large increases in stratospheric aerosol loading accompanied by precipitous declines in global lower troposphere temperature and those declines persist for extended periods of time (years) while thunderstorms operate on daily time scales.
Hmm. After I had posted my long post I went back and looked at Gymnopserms post about IR radiation equivalent temperatures of cloud versus open skies.
The notches in the clear sky spectra show exactly the effect of CO2 when its NOT cloudy, and exactly the effect I mentioned when it was cloudy, that in essence the cloud radiation is almost independent of CO2 concentration.
What I couldn’t understand, and still can’t fully is that his contention that clouds radiate a lot less than hot ground, is supported by the evidence. Well some of it. It fully explains warm nights with cloud cover versus cold ones without.
And that makes me suspect I may have been wring to criticise Thomas when he said that albedo would be the only dominant effect for daytime clouds, yes Thomas perhaps that is in fact the case. My bad.
Looking at Gymnopserms data and doing a rough calculation reveals that yes, the difference between ground temps and cloud top radiation terms is the same as a T^4 rule would allow for ( (290k/215k) ^4 ~ = 3.3 or so) which is of course precisely the sort of difference one sees at night.,.,. but that doesn’t gybe with the fact that overall thunderstorms cool the surface, and so do clouds, by day.
So where is all the heat going? According to gymnosperm its not radiating to space in the infra red… Thomas must be right, something greater than a factor of 3.3 must be reflecting visible and UV light (not covered by IR thermometers) back into space before it even gets near the ground. And that’s albedo. So to get a net reduction in temperature that means net outflowing radiation must be greater than net inflowing..and that means that the reduction in radiation in terms of reflected visible light must be greater than the 3.3 figure gain that the IR radiation shows.
Well as a photographer who grew up in the days of manual cameras and hand held exposure meters, for sure full cloud is two, three or four stops, depending how thick it is. Which is in incoming (visible) radiation reduction of 4-16 times! And the bulk of the sun’s radiation is at or near the visible spectrum as are some of the absorption spectra dues to GHG etc.
What does this mean – well it means that when we stop looking at local transport, we have a figure – albedo modulation – more than big enough to account for the loss of radiation due to cloud cover. By day the net energy balance of cloud cover will be to cool – often dramatically, just as by night the reverse is true.
Ergo I may have been half right, because yes, clouds do carry energy way to space to radiate there, but not as much as direct ground and a clear sky does, BUT the important thing is, that the albedo of total cloud cover is massive and more than large enough to provide overall net cooling by day.
What this leads to is a picture of thunderstorm energy balance that goes like this. Warm wet air rises, and due to adiabatic lapse, cools condenses and transfers heat to the upper atmosphere, but if it were to fall as rain, would warm up again and become warm wet air again with only a little overall cooling from the 215k cloud top radiation.
BUT what must be happening is that albedo increase absolutely stamps on the incoming radiation. Not where the IR satellites are measuring it, but in the visible and UV spectrum. That’s where the net energy balance is adjusted, and because it’s cloud tops above the GHG effect, and radiation in a band where CO2 holds no sway, CO2 et al are completely irrelevant. So with clear skies CO2 rules, but when its cloudy, it’s almost irrelevant.
What this boils down to is this: ultimately we know that the energy balance of the earth has to be – for a steady temperature – a net zero. Negative feedback has to be in place to maintain it that way or we would go into thermal runaway. Radiative effects on an assumed steady level of incoming radiation are what AGW theories deal with – the T^4 radiation means that night time radiation loss is hugely proportional to temperatures, so the AGW alarmist – perhaps we should call them scientists of the Dark Side – of the planet are correct in terms of analysing energy loss (by night) but they have completely failed to account for the energy gain modulation of incoming radiation by albedo variation by day..
If there were no albedo variation then AGW would probably be almost correct. Gymnosperms graph showing deep water vapour and CO2 notches in the IR would rule the day (or rather the night!!!) .
But what we are seeing perhaps is that where it’s really at, by day, on the Light Side, is albedo. Anything that modifies albedo will have a massive effect on surface temperature. If a volcano erupts, that’s extra albedo, If a thunderstorm happens, that is, too. And consider, if land masses concentrate in polar regions, that’s a massive increase in albedo, as not only will the tropics be open sea and therefore more albedo than land, but the polar land will be snow covered and have a higher albedo as well. Land all at the poles might very well be a high albedo snowball earth.
So whilst its true that the effect of a thunderstorm is to suck heat from the surface and chuck it up high which cools the surface, it also must be warming the upper atmosphere somewhat, and the energy hasn’t been lost, just moved. But the albedo gain will reflect massive amounts of extra sunlight away from the surface so that such radiation as there is in the 215k cloud top radiation is enough to overall cool the system because the incoming radiation is now far lower. That’s the only way it makes sense to me. And of course if that results in rain and clear night time skies, you will get a very nice extra cooling effect. Albedo is no use at night – it doesn’t cool you – just stops you getting too hot by day.
This brings a much clearer picture to me than I had earlier today, about the net effect of cloud cover..a subject I couldn’t get my brain around, which was this. Is the net effect of cloud cover overall warming, or cooling?
The IR graphs absolutely show that clouds massively reduce IR radiation which is the dominant form of heat loss by night, and of course by winter too where there is ‘more night than day’. Cloudy polar regions ought to be much warmer in winter than cloudless ones. So here where heat input is transported heat from the tropics, and the cooling is IR dominated, maybe we expect to see overall warming if its cloudy
But in the tropics, where the heat input is direct solar radiation, extra cloud cover by day will be more than enough to compensate for extra cloud cover by night (and that may go if there is a thunderstorm to ‘clear the air’) , and clouds will have a net cooling effect overall.
And that confirms my suspicion. CO2 and the GHG effect is real and it affects night time radiative LOSSES a bit, but its almost completely irrelevant by day, where albedo variations from cloud cover will dominate the energy balance, especially in the tropical regions.
And the argument from scientists of the Dark side, that water vapour will amplify temperature variations, is true. By night. And somewhat in the Polar regions. By Day its exactly the opposite effect, extra water vapour means extra cloud, and that means a lot cooler overall, in the tropics.
And as there is a lag in transporting heat from tropics to poles, that means that positive fluctuations in cloud will first cause high latitude warming, where heat loss by night dominates, before cooler ocean currents driven by cooler tropical temperatures will lead to colder winters, and then snow ice and less cloud, and a nasty big freeze up.
And so on ad infinitum Colder subsea currents will then cool the tropics, reduce cloud cover and the tropics will start to warm up again…
And it may explain why the Antarctic is somewhat different from the arctic – the heat transport there is weird. It is a land mass surrounded by sea and the circumpolar current more or less isolates that land mass from tropical heat. It would be interesting to compare polar cloud cover over the last few decades..my guess is there is less cloud in the Antarctic.
[Long analysis. Thank you. .mod]
The GHE & blanket analogies are both inadequate since they don’t account for the water cycle. If I chop wood on a cold day in a heavy coat, sweat will cool me off. If I blanket my house & don’t turn down the heater it’s going to get warm. The sun doesn’t have a thermostat, although there are both short and long term fluctuations in output. The earth does have a powerful thermostat in the clouds and water vapor cycle. However: 1) they are difficult to model and 2) not due to man.
Willis,
Your world map of the TRMM data shows the main band of thunderstorm activity (in the Pacific and Atlantic oceans) to be north of the equator.
Given that the Earth is some 5 million km closer to the sun in the southern hemisphere summer (Dec) one would expect the global average activity to be slightly south of the equator.
Is there any known reason for it to be North of the equator ?
Here in NZ the intensity of sunlight mid summer is far greater than in the Northern Hemisphere (in terms of how quickly one gets burnt by the Sun) A lot of that will of course be due to significantly lower air pollution but not all of it can be so attributed.
Bernie January 8, 2016 at 11:17 am
pete January 8, 2016 at 12:47 pm
Pete, if you add more heat to a pan of boiling water, the excess heat simply goes into evaporation.
However, as Figure 2 clearly demonstrates, the water doesn’t need to be boiling in order for the excess heat to be lost to evaporation. The key is understanding that thunderstorms actively increase evaporation. Once a local area crosses a certain temperature threshold, thunderstorms begin to form. They increase evaporation via several mechanisms.
First, evaporation is a linear function of wind speed. If the wind goes from 1 m/sec (2.2 mph) to 10 m/sec (22 mph), you get about ten times the evaporation. A thunderstorm easily generates winds of 20 mph (~ 10 m/sec) or more around the base. So a thunderstorm can change local evaporation rates by an order of magnitude.
Next, waves on the ocean and spray both on land and in the ocean each increase the evaporating surface area.
Next, the air exiting from the top of the thunderstorm tower has had almost all of the water wrung out of it. This dry air descends on all sides of the thunderstorm, delivering bulk dry air to the surface. Evaporation is a function of the difference between surface vapor pressure and the air vapor pressure, so dry air gives greater evaporation.
So those are some of the the ways that the thunderstorms cool the surface through increased evaporation. However, they also cool the surface in several other ways.
First, cold rain from aloft immediately cools the surface of whatever it hits. This cooling effect is so strong that if the thunderstorm stands still and the rain just falls directly under the lowest part of the thunderstorm, it’s like Smokey the Bear micturating on a campfire—the thunderstorm goes out. It has to move to survive.
Next, the rain is cold because it evaporates as it falls, cooling both the rain and the surrounding air. This air is entrained by the rain. Unlike the rain, it spreads radially when it hits the surface, cooling a much larger area than the thunderstorm itself. In the tropics, this cool wind is the sign that there is a thunderstorm in the neighborhood.
Next, on the ocean the thunderstorm-driven wind cause whitecaps, spray, and spindrift. These are all white in color, so they reflect incoming solar energy back to space.
Next, the thunderstorm towers greatly increase the reflective area of the clouds. This is particularly true in the late afternoon when the sunlight strikes the sides of the towers, and they cast long shadows.
So those are the major cooling mechanisms that restrict the maximum temperature in areas of tropical thunderstorms. And since the increase in evaporation is the largest of these, the analogy with boiling water is indeed apt. Yes, nothing is boiling, but the major mechanism is the same—excess heat goes into increased evaporation.
Finally, this is the beauty of WUWT. In answering your question, I’ve just realized that I have been underestimating the total evaporative cooling. This is because I haven’t included the evaporative cooling of the rain as it falls to the surface. See, I’ve been estimating total evaporative cooling based on total rainfall. But however much of the rain that evaporates before hitting the surface also needs to be counted, and it’s not counted in the rain fall because it has already evaporated.
Or at least some of it is not counted in the rainfall …. I’ll have to think about how to best estimate that evaporative cooling. However, from experiencing how cold it can be under a tropical thunderstorm on even the warmest day, due to both the cold rain and the cold entrained wind from that rain, I’d say it is not negligible.
Best regards to you,
w.
richard verney January 9, 2016 at 4:25 am
Willis
You are of course correct that there is horizontal transport of water vapor. However, over the tropical ocean the transport distance must be short and the transported amount must be small, as evidenced by the clear and quickly varying boundaries of the areas where there is rain.
The close coupling of evaporation and subsequent rainout is also demonstrated by the strong correlation of rainfall with local temperature.
No, it doesn’t mean that those areas have no evaporation. It means that they have little rain. Remember, generally in the tropics rain means thunderstorms, so as I’ve pointed out, I’m discussing thunderstorm evaporative cooling.
Ah. Actually, what you need is the latent heat of vaporization at a given temperature. I use a PDF of seawater properties from MIT, see page 7. It gives the latent heat of vaporization at ~30°C and a salinity of 35 g/kg as being 2350 megajoules (MJ)/tonne.
Next, density. Again from the MIT paper, seawater at 30°C and 35 g/kg salinity is about 2% heavier than freshwater. So it takes 2% more energy to evaporate the extra weight, or a total of 2350 * 1.02 ≈ 2400 MJ.
Now one watt is 31 megajoules per year, We need 2400 megajoules per year to evaporate the cubic metre of seawater. So … 2400/31 = 76 watts of evaporation per metre of rain. Because I work a lot in my head, and to allow for some inefficiencies, I round it to 80 W/m2.
I have listed these for you previously. However, we don’t need to understand the exact mechanism to be certain that some mechanism exists.
Let me give you actual measurements from one of the TAO buoy, on the Equator at 165°E, measurements which also agree with the CERES data. All data is 24/7 averages.
Downwelling solar radiation at the surface: 248 W/m2
Upwelling solar radiation at the surface: 12 W/m2
Solar energy absorbed by the ocean: 236 W/m2
Now losses.
Evaporation: 187 W/m2
Radiation: 473 W/m2
Total energy lost from surface: 660 W/m2
Now, you have claimed over and over that the downwelling longwave radiation (DLR) at the TAO buoy is NOT absorbed by the ocean.
My question is, if the DLR is not absorbed, then the ocean at the TAO buoy is absorbing 236 W/m2 of energy, and meanwhile it is constantly losing 660 W/m2 of energy … so why is it not frozen? In other words, All I want to know is what physical process can on a 356 24/7 basis provide over 400 W/m2 to the ocean to keep it from freezing?
I have answered your courteously posed questions, and have done so many, many times in the past. I now await your answer to my single question—at the TAO buoy at 165°E, what physical process is providing over 400 W/m2 of energy 24/7 to the ocean surface if the energy is not from DLR?
w.
Willis,
Rain can evaporate as it falls but moisture from the surrounding air can also condense on cold rain droplets. This is why relative humidity at the surface often falls during a rain shower. Rain droplets are born relatively high in the troposphere, where the air is cooler due to the lapse rate. Therefore, rain is usually cooler than the air it is falling through when it reaches close to the surface. Water is incompressible so, unlike air, rain does not heat as it falls—except for some minor heating due to friction with the air it is falling through.
However, it seem to me that no amount of evaporative cooling can remove heat from the global troposphere because evaporation is an adiabatic process. Evaporation consumes heat, which cools the surrounding air, but when the evaporated moisture condenses back to liquid, the heat is returned through the latent heat of condensation. Heat is moving around in the system but no heat leaves the system.
Therefore, it seems to me that no amount of thunderstorm evaporation could overcome even a small amount of greenhouse gas heating. Greenhouse gasses “trap” radiant heat in the atmosphere, which causes the atmosphere to equilibrate at a new, higher, temperature. Evaporation and condensation are internal processes and they do not change the exchange of heat between the troposphere and deep space.
Thunderstorms can have a damping effect on global temperature but the effect would be mostly, or only, due to the fact that clouds reflect sunlight. This effect does not seem to be sufficient to overcome the cooling effect of a those rare volcanic eruption that are large enough to spew large amounts of reflective particles into the stratosphere. Those particles reflect sunlight and that causes global cooling because less of the radiant energy from the sun reaches the surface.
Since the damping effect of thunderstorms does not seem to be sufficient to counter act the cooling effect of stratospheric aerosols, I doubt that the effect could counteract greenhouse warming. I suppose it’s possible that the effect might require years to counter the rapid cooling that occurs with increased aerosol loading but I doubt that too because global temperature falls when stratosphere aerosol levels increase, then rises again when the aerosols settle out.
The two coldest years in the UAH temperature recored occurred after the eruptions of El Chichon and Pinatubo, when aerosol loading caused stratospheric optical depth to increase by as much as a factor of 24.
Willis,
At 12:56 PM you wrote:
“Next, density. Again from the MIT paper, seawater at 30°C and 35 g/kg salinity is about 2% heavier than freshwater. So it takes 2% more energy to evaporate the extra weight, or a total of 2350 * 1.02 ≈ 2400 MJ.”
The salt doesn’t evaporate. It stays in the ocean. Only water vapor leaves the surface.
We know that heat loss to space can only occur via radiation
We know GHGs absorb most of the radiation that hits them of the correct wavelengths
We know this absorbed radiation is mainly lost to other molecules via collisions. (At altitudes of 20km the MFP is 9.139e-07 metres and the Collision frequency is 4.354e+08 / sec)
we know that heat loss to space can only occur where the mean free path is sufficiently great and radiation finally leaves the earth
we know that only radiation from the ground which is not absorbed by ghgs reaches space
it must therefore be true for radiation from cloud tops – radiation that would have escaped from the ground will also escape from the cloud tops (clouds will emit a near BB radiation pattern). BUT radiation that excites ghg molecules will still excite ghg molecules and will be indistinguishable from the IR from the ground.
Radiation from cloud tops is therefore exactly the same as radiation from the ground from where the heat was transported.
If this is the case then I do not see where thunderstorms change the overall energy balance. Do they simply transport the heat to cooler areas. Where is the mechanism for reducing the overall energy content of the globe?
I think the answer is that clouds reflect visible light, which has too short a wavelength to be absorbed by greenhouse gasses. Look at a photo of the earth from space. Clouds are bright.
Thomas January 10, 2016 at 1:39 pm
Remember that the metric at issue is not the total amount of heat in the system. It is the surface temperature.
Tropical evaporation is only one of the many ways that the suface temperature is controlled by emergent phenomena. The first line of defense is varying the time of the emergence of tropical cumulus clouds, which regulates the amount of solar energy reflected into space.
Beyond that, the thunderstorms act as huge air conditioners. Latent heat is moved from the surface up to the LCL, the lifting condensation level. At that point it condenses, releasing the heat. This heat then fuels the development and maintenance of the cumulus tower. This means that much of the heat is converted into work. Finally, the dehumidified air from the surface is lifted to the cloud tops.
Bear in mind that throughout the whole process from the condensation up through the middle of the cumulus towers up to the cloud tops, the air doesn’t interact with the surrounding atmosphere. It is not radiating energy which can be absorbed by CO2 in the surrounding atmosphere. Inside the cloud the radiation goes nowhere.
And at the altitude of the cloud tops, there is very little of any of the GHGs. This means that whatever heat is left in the air at the top of the cloud towers is free to radiate to space.
Finally, it is the evaporation and deep tropical convection resulting from that evaporation that drives the transfer of heat from the tropics to the poles, where it radiates to space. So at the end of the day evaporation drives the whole shebang.
Regards,
w.
Converting a ton of water into a ton of ice requires 288,000 Btu/ton, aka 317,376 Btu/tonne.
One cubic meter holds 1,000 kg, aka 1 tonne of water. Yes, ice is less dense, but does it really matter?
The area of Antarctica is about 1.4E7 km^2, 1.4E13m^2. A meter deep layer of ice would be, duh, 1.4E13m^3, aka 1.4E13 tonne. Converting that tonne of water to ice absorbs 4.44E18 Btu.
ToA spherical surface area is 5.12E14 m^2. ToA solar input is 340 Btu/m^2. Over 24 hours the complete ToA spherical surface area would receive 1.74 E17 Watts, 5.95E17 Btu/h, total over 24 hours 1.43E19 Btu.
It would take 3.21 meters of ice to absorb the entire ToA input of 340 Btu/m^2. The additional 2.0 W/m^2 of anthropogenic RF between 1750 and 2011 could be absorbed by 0.02 m, 0.74 inch. RCP 8.5 could be absorbed by 0.08 m, 3.16 inch.
Water’s latent heat of evaporation/condensation is about 1,000 Btu/lb, 293 Wh/lb. Sensible heats: water, 1 Btu.lb-F, air, 0.24 Btu/lb-F.
This all makes it pretty clear why water vapor is the 1,000 pound/454 kilo gorilla of all the GHGs.
A similar analysis could be applied to the ocean surface.
The numbers are subject to review. Everybody makes mistakes. Want it all metric, help yourself.
@ur momisugly Willis.
“And at the altitude of the cloud tops, there is very little of any of the GHGs. This means that whatever heat is left in the air at the top of the cloud towers is free to radiate to space.”
——————————-
are you sure?
That statement says we have a real problem because above the cloud tops there is little GHG so no saturation. Increase the GHGs and you have a linear not log relationship to the GH effect.
for discussion below see 2009 Schlatter_Atmospheric Composition and Vertical Structure_eae319MS-1.pdf
1st From wiki
Genus Cumulonimbus (heap, storm/rain)
Altitude 2,000–22,900 m (6500-75000 ft)
so upper limit is about 23km
at this altitude co2 is still well mixed
http://s5.postimg.org/5mewbepqv/mixing_ratio.jpg
And collisions occur every 45ns so a photon would only be able to travel 13.5 metres so plenty of collisions of photons between GHGs before top of clouds and space. and since the mfp is only a couple of micrometres there will still be a lot of heat transfer molecule to molecule by collisions. heat transferred to non ghg molecule would of course have to be retransferred to a ghg molecule in order to escape to space.
http://s5.postimg.org/xb1jixcrb/mfp.jpg
The only ghg in short supply at these altitudes would be water vapour so that would allow some heat to escape.
Willis,
Thanks. You wrote:
“Remember that the metric at issue is not the total amount of heat in the system. It is the surface temperature.”
That’s part of the problem. GHGs should increase total heat in the system but temperature is not a measure of total heat. Enthalpy is a measure of total heat. It’s expressed in kJ/kg of dry air. At a given temperature the enthalpy will be higher when the humidity level is higher. So knowing only temperature doesn’t tell us anything about the energy in the earth’s system. The total heat on a 110 °F day in Phoenix could be the same as in Orlando when the temperature is only 80 °F. Air temperature is at best a rough proxy for total heat.
The air at the top of a large cumulus cloud might be hotter than it would be without the convective activity, even though it is still very cold. That might mean that it radiates more heat to space then it otherwise would but that depends on the distance it takes, at those rarified altitudes, for a LW IR photo to strike an air molecule. If that distance is short, there is no net removal of heat from the system.
It seems like the the only way thunderstorms could remove significant heat from the troposphere is by reflecting sunlight.
In the article you wrote:
“This means that [the thunderstorm] effect will be to maintain the same temperature, regardless of reasonable-sized fluctuations in the amount of forcing. Clouds don’t know about forcing, they form and disappear based on local conditions.”
Both El Chichon and Pinatubo ejected sufficient aerosols into the stratosphere to cause global cooling that lasted for several years. The two lowest annual temperatures in the UAH record correspond with those two eruptions. El Chichon occurred when the ENSO 3.4 index was low and it took several years for temperature to recover. Pinatubo occurred when the ENSO index was high, which might explain why the cooling was less and the recovery was faster, but it still took several years to recover to the mulit-decadal average.
(ENSO data from NOAA.)
So your posited thunderstorm effect seems to not be able to quickly overcome the forcing from stratospheric aerosols. However, it would be interesting to take a look at what happened to tropical storms directly after those eruptions. If they really did decrease, that might support your theory.
It’s been interesting discussing this with you. Thanks for taking the time.
Sergei, the difference regarding CO2 is not in the ratios of the gases. The difference is in the density. At an altitude of 10 km, for example, the pressure is only a quarter that of the surface. So it is correspondingly easier for a photon to make it to space unhindered.
SMK
please see new plot
As I said and you agreed water vapour is not going to have much effect above thunderclouds. However CO2 is well mixed even at 100km so increasing CO2 will widen absorption band and reduce the transfer of heat to space. from the plot the current transmittance at 16um is still only 10% at 15km
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W
However, the main change is that as your lovely graphic above neatly illustrates, there is very little water vapor up high.
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agreed. The IR blocked by H2O vap will be the only change by which thunderclouds will be able to cool the planet
But you must then agree that increasing CO2 will actually cause a reduction in IR transmitted from top of cloud to space reducing the cooling effect.
As a result, between the reduced pressure and the reduced water vapor, any heat at altitude has a much easier path to space than does heat at the surface.
http://s25.postimg.org/wf2bvc7fz/ir_transmission_15km.png
https://books.google.co.uk/books?id=QPBQ5w4X8RkC&pg=PA88&lpg=PA88&dq=ir+transmittance+at+30km&source=bl&ots=dE3xEQmCKZ&sig=h4Qv2q1PG7TEY117cucdBuPMKpI&hl=en&sa=X&ved=0ahUKEwjb-6zD36HKAhVHWRoKHX6gDfgQ6AEIIjAA#v=onepage&q=ir%20transmittance%20at%2030km&f=false