Evaporation Redux

Guest Post by Willis Eschenbach

I got to thinking again about the question of evaporation and rainfall. I wrote about it here a few years ago. Short version—when the earth’s surface gets warmer, we get more evaporation and thus more rainfall. Since what comes down must go up, we can use the Tropical Rainfall Measuring Mission (TRMM) satellite rainfall data to calculate the corresponding rainfall-related evaporation.

From that TRMM data, we can also calculate how much the evaporation changes with additional warming. Figure 1 shows the trends in evaporative cooling with respect to temperature, in units of W/m2 of additional evaporative cooling per degree of additional warming

CERES trends evaporative cooling per °C

Figure 1. Amount of additional evaporative cooling per additional degree of temperature. Red areas have the greatest rainfall and thus the greatest evaporative cooling. The area of greatest cooling is the Inter-Tropical Convergence Zone (ITCZ) just above the Equator. Note that this includes three additional years of CERES and TRMM data compared to my earlier analysis.

As you can see above, the change in evaporative cooling per degree C ranges from a drop in evaporation of -70 watts per square metre per degree of surface warming (W/m2 per °C), all the way up to an increase in cooling of well over one hundred W/m2 per °C of surface warming.

Now, I’d gotten that far in my previous analysis, but I was stymied by the incomplete coverage. At the time I said:

As noted above, the TRMM data covers about two-thirds of the surface area of the Earth. From appearances, unlike in the tropics, the correlation of evaporation and temperature is negative in the unsurveyed areas of both the northern and southern extratropics. The grey line at about 30°N/S shows where the relationship goes negative. This is no surprise. In the extratropics, rain is associated with cold fronts instead of being associated with thermally driven tropical thunderstorms. As a result, although the overall average change in cooling shown in Fig. 6 is 11.7 W/m2 per degree of warming, I suspect this be largely offset once we have precipitation data for the currently unsurveyed areas.

So my quick guess at the time was that overall the value might be around zero. However, this question continued to bother me. So I started thinking about how I could estimate the trends in the areas not covered by the TRMM data. I began by looking at the average evaporative cooling by degree of latitude. Figure 2 shows that result.

average evaporative cooling trend by latitude

Figure 2. Latitudinal averages of evaporative cooling (W/m2 per °C), in 1° wide latitude bands.

This was quite encouraging. I had previously assumed that as we went towards the poles, the trend would continue to go more negative. But both in the northern hemisphere (positive latitude) and the southern hemisphere (negative latitude), the trend is heading back towards zero as we go towards the poles. This would indicate that the values nearer to the poles might be around zero.

Next, I took a different look at the data. Figure 3 shows a scatterplot of the evaporative cooling trends versus the average surface temperature. It shows on a gridcell-by-gridcell basis the relationship between the evaporative cooling trend for that gridcell versus the long-term temperature of that gridcell. There are 28,800 gridcells shown in Figure 3.

scatterplot evaporative cooling trend 2000 2015

Figure 3. Scatterplot of the evaporative cooling trends versus the average surface temperatures, 40° North to 40° South.

Now, this is quite revealing. It shows that at the cold end of the temperature scale, the evaporative cooling trend is quite small. Where the surface temperature is 0°C to 5°C, the average trend is -0.05 W/m2 per °C. For a surface temperature of 5°C to 10°C, the average trend is -0.6 W/m2 per °C.

SO … I think we can reasonably estimate that the average trend in the unmeasured areas of the globe shown in Figure 1 is on the order of -0.5°C. Recalling that the area from 40°N to 40°S is about 2/3 of the globe, and that the average for that area is 10.7 W/m2 per °C, that means that the global average is (1/3) * -0.5 + (2/3) * 10.7 = 7.0 W/m2 per °C.

Now, if this estimate is high and the actual value in the white unsurveyed areas in Figure 1 is say -3.0 W/m2 per °C, that would give a value of 6.1 W/m2 per °C. And if the estimate is low and the actual average value in the unsurveyed areas is 3.0 W/m2 per °C, that gives us an average of 8.1 W/m2 per °C.

So it appears that a likely global value for the trend in the evaporative cooling for each °C of additional warming is on the order of 7 ± 1 W/m2 per °C.

Next, note that in the tropics the evaporative cooling trend goes up rapidly with temperature. The average in the tropics is 16.7 W/m2 per °C, with some areas cooling at over 100 W/m2 per °C.. Since the tropics is the area where the most energy enters the system, this provides a strong mechanism to prevent overheating.

Next, it is important to understand that this strong cooling effect is not applied at random. Instead, in general it occurs preferentially where the surface is warmer than the surrounding areas. As a result of the targeted application of the cooling, it has a larger effect than if it were applied willy-nilly.

Finally, in IPCC terms this would be classed as a feedback. That is to say, if the surface is warmed (by increased forcing or any other cause), when it warms the increased number of thermally-driven thunderstorms act to increase the evaporation and cool the surface back down. However … as far as I can find it is not included in the IPCC analysis of all feedbacks.

Regards to all,

w.

My Usual: If you comment please QUOTE THE EXACT WORDS YOU ARE DISCUSSING, so we can all understand your subject.

Further Reading On Evaporative Feedback:

Dr. Judith Curry

Dr. Roy Spencer

Advertisements

151 thoughts on “Evaporation Redux

  1. Willis

    Interesting article. I miss your posts on this site.

    Don’t forget that wind impacts upon the rate of evaporation. Do you know what the average how does average wind speed is over different regions, and do you know whether there has been any trend in average wind speeds over different regions.

    If warming leads to more storminess, as AWGers often claim, then there will be more evaporation, and this will lead to more evaporative cooling.

    It looks to me as if there is the potential for a number of negative feedbacks which act as governors and help keep the system stable.

    • Don’t forget that wind impacts upon the rate of evaporation.
      =========================
      very good point. especially in the tropics with the trades and monsoon.

    • Not really, why are 90% of glaciers melting very, very quickly. Just a guess, but the planet might be warming. Actually its not a guess is it.

      [??? 90%? .mod]

      • Humidity can melt glaciers. Any psychrometric data out there?

        The heat transfer rate from condensation is far higher than convection.

      • And as they melt, they reveal all sorts of things…
        intact trees and flora…
        ancient mines and farms…
        frozen people, who, no doubt dug holes through hundreds of feet of ice, and crawled down into the ice to die and then freeeze…
        Sure.

      • Steve

        Not really, why are 90% of glaciers melting very, very quickly. Just a guess, but the planet might be warming. Actually its not a guess is it.

        Steve. Actually, roughly 1/3 of the world’s glaciers are expanding (lengthening/gaining mass.)
        1/6 are steady.
        And only about 1/2 are receding/losing mass.

        You do understand that means 1/2 are steady or gaining mass, and 1/2 are receding or losing mass, right?

      • 90 percent melting VERY QUICKLY.

        Words need evidence, show it please.
        Do you remember when
        CAGW advocacy groups said Himalayan glaciers were melting rapidly, and as it turns out, they are not.

        Further question, when you turn on the heat to high under a large pot of water and then slowly turn the heat down, will the water T rise continue while the source heat is reducing? Now study the LIA and calculate the thermal inertia in our global oceans.

      • “David A June 11, 2017 at 5:16 am

        90 percent melting VERY QUICKLY.

        Words need evidence, show it please.”

        Evidence from Griff and tony macleod is enough for some.

      • There’s a study of the Alps, which began to shrink around 1850 (or so), that put the blame on industrial-age soot. Soot is likely responsible for some melting in Greenland.

      • Basically, as long as the planet is above a certain temperature, glaciers will be mostly melting. We can get warmer and cooler in cycles and remain above that temperature the whole time. So, even though we have been cooling since 2002, we are still warm enough for melting to persist.Melting will slow in many places, but still continue. Cooling warm water does not make ice, except if you cool it enough, to below 0 deg C.

      • Steve, you mean ALL glaciers everywhere ?? My understanding is in the Arctic there is some melting, but there is intense ice build up in the Antarctic… I was thinking Greenpeace could ferry all those hungry polar bears cooling off on little bits of melting Arctic ice floe down to Antarctica for some nice cool weather.

      • Hey, Steve, many retreating glaciers are revealing vegetation that was covered hundreds and thousands of years ago. Some artifacts are being uncovered for the first time since the beginning of the Little Ice Age.

        The cooling began before significant use of fossil fuels and the warming too. Most likely, mankind will be better prepared to handle the next cooling, whenever that might be.

      • Steve actually it’s very much a guess, since we found out government employees at the global repository of climate records at the CRU campus at East Anglia in the UK, have destroyed global records to the point that actually, nobody knows the exact historical temperature profile of the planet.

        You – most especially if you are in fact able to ”Guess” what people mean when the literally, write in stuff for you to read between the lines – of code – to other phd. – would be very, very well educated to look up and read,

        the text file called ”HarryReadMe.txt” as one of the climatologists explains how MOST data is either entirely fabricated out of thin air,

        or corrupted so badly from such fabrications without record of the alterations and fabrications, that they’re long, long since useless.

        ”harryreadme.txt” is the name. I don’t know if it is ok to include links, but it’s one of the most famous

        ‘omfg what have these people done?! moments

        in all of climategate.

      • “Not really, why are 90% of glaciers melting very, very quickly.”

        Because they aren’t.

        Stop making stuff up.

      • …why are 90% of glaciers melting very, very quickly. Just a guess, but the planet might be warming. Actually its not a guess is it.

        When I looked into the state of knowledge on glaciers, my sources indicated that less than 50% of the world’s glaciers were even inventoried, let alone studied precisely and consistently enough to arrive at a 90% melt rate for them ALL. Where did this 90% statistic come from? … I’m thinking it’s bogus.

        Correct me, if you have other sources that say otherwise.

      • Most glacier retreat is due to increased solar insolation. Check out the Cascade glaciers around volcanos. You will find far more retreat in south facing glaciers than north facing glaciers. This is true all over the world, and many north facing glaciers are in fact advancing, in the Himalayas for example..

      • To Steve:-

        If you are aware of the Little Ice Age which affected earth from the early 1300s until the mid 1800s then you will know that it reached its coldest depths between 1645 and 1750 and that Glaciers had expanded and grown throughout the ~400 years of the LIA.

        The LIA followed the Medieval Warm Period when temperatures were around 1 deg C or more higher than the 20th century average. During the LIA much of civilisation and human development went into reverse due to the extreme cold conditions and the daily battle to survive them.

        Crops in Scotland, parts of England and Wales and elsewhere in Europe simply did not ripen and widescale famine arose across Europe and elsewhere in the world. In Germany wine production dropped to a little over 50% of what it had been during the 1300s; rivers as far south as Italy Froze solid in the worst winters and in London Ice Fairs, complete with ox roasts on the ice, were held annually on the River Thames when it froze for months on end.

        When Henry VIII came to the throne of England in 1509 there were still 139 large vineyards in the UK – enough to provide strong competition for French wines. These vineyards All disappeared during the increasing depths of the LIA. Despite temperatures beginning to recover from the LIA in the latter part of the 19th century it was not until 1951 that it had become warm enough again for the first commercial vineyard to be established in the UK. It was not until the 1980s that it was warm enough again for vineyards to be established across parts of southern england and into the midlands and subsequently into parts of Wales.

        Steve, you will of course note that the IPCC and climate scientists have carefully chosen the latter part of the 19th century as the starting point for modern ‘global warming’. The fact that this has been a natural recovery from the LIA to more normal temperatures such as the MWP is carefully airbrushed out or pushed to one side. Hence the desparate but failed attempts by ‘leading’ ‘climate scientists’ to remove the MWP from history. Without the MWP the recovery from the LIA is made to appear as if there has been a dramatic, mankind-influenced increase in temperature and that is aimed at the uninformed or those deliberately kept ignorant.

        Incidentally both the Roman and Minoan warm periods were 1 deg C or more warmer than the MWP and not one of these reached the higher temperatures of the Holocene Climate Optimum of around just 6,000 years ago .

        So Steve, given that glaciers expanded significantly during the LIA and with it only ending 150 years or so ago how can you even begin to think it surprising that as temperatures have been recovering from the LIA that around 50% of glaciers are shrinking slightly and giving up the growth they put on during the LIA?

        As a matter of fact it is around 50% of glaciers and not the 90% you erroneously claim.

        As a final remark, as the planet has been warming and cooling naturally throughout the millennia with temperatures just a few centuries ago warmer than today there is no reason for mankind to assume or to pretend that we can alter our climate and temperatures. That is simply hubris, or it would be were the underlying motives not entirely political.

      • One of the best things about your postings Steve is that it provides the opportunity for genuinely informed and factual rebuttal of them.

        That is of great benefit to the average reader, or as we might say in the UK ‘the man on the clapham omnibus’, and the ability to adress and directly expose falsehoods in your comments is of significant value in exposing the disinformation that is put out by climate alarmists.

        Thanks for your help and please keep up the good work.

      • Take an ice cube out of your freezer. Put it in a jar and keep the temperature constant at one degree over zero.

        Wow, it melts! Even though the temperature is not increasing,

        But, but how? Doesn’t melting require temperatures to be increasing?

      • 100% of the glaciers could have already melted completely and it still WOULDN’T prove CAGW theory.

  2. “Finally, in IPCC terms this would be classed as a feedback. That is to say, if the surface is warmed (by increased forcing or any other cause),”
    Yes, but the notion of feedback there is to the global system, not just surface. As you note, what goes up must come down, restoring the latent heat. It just moves heat from one place to another. It’s true that it moves heat upward ( as in the Trenberth diagram), and that may partly counter the hindering of that flux by GHGs. But of course, at the expense of more wv hindering.

    • Nick Stokes, as the energy is transported upwards where most of the spaceward radiation takes place, can’t evaporation be seen as a step in the process of radiative cooling? And so as a feedback?

      • At Wim, BINGO, that is the very process that increases radiation to space.

        How much energy is used in accelerating the hydrological cycle???

        Also increasing w/v, even in clear sky’s prevents a large amount of energy from reaching the surface. Some of that energy is PREVENTED from reaching our oceans which have a vastly longer energy residence time, meaning the net affect of W/V on that spectrum is cooling. Add in clouds and the feedback is???
        CAGW science is very uncertain regarding all the above, but the observations indicate they greatly over estimate warming, underestimate negative feedbacks, and may well have the results backwards regarding a cost benefit analysis of additional atmospheric CO2.

      • that’s the main heat exchange but there is also some when water freezes- as in when the largest moiety of evaporation, being north of the equator, is deposited on the arctic.
        which may explain a bit of another puzzle, too.

    • what goes up must come down, restoring the latent heat….It’s true that it moves heat upward ( as in the Trenberth diagram), and that may partly counter the hindering of that flux by GHGs. But of course, at the expense of more wv hindering.

      Er, excuse me, what goes up does not have to come down.

      Heat that rises above the bulk of the CO2 is not subject to being modulated by the existence of that CO2.

      Radiation from cloud tops is what we are talking about as compared with radiation from the ground.
      In addition the increased albedo from clouds will stop incoming radiation even reaching the ground.

      The AGW mythology requires that we focus on one aspect only – ground radiation. In reality we know that ~50% of ground heat loss is via convection and evaporation etc etc. That heat does not all come back.

      As I said, the effect of water vapour is to transfer heat from the surface to higher altitudes: This may help prevent night time cooling but in less arid places its effect is overwhelmingly to lower day time temperatures both by direct albedo increase and by radiation from cloudtops that transfers heat completely out of the ecosphere.

      This is clearly demonstrated by the fact that desert regions are massively hot by day, with no cloud to shield them, and no water to evaporate, and cold by night as the lack of water vapour or clouds allows unfettered direct radiation from the ground to space.

      Less arid places are controlled by the presence of cloud, which cools by day and warms by night.

      What this effect should show is that hot deserts are less cold by night and a little less hot by day with increasing CO2, but in areas where the temperature is essentially controlled by the water vapour cycle, temperature should be almost completely independent of CO2.

      The IPCC ignores all this not just because it is counter-narrative, but also because it is ultra vires. The IPCC is not there to determine whether or not AGW is a fact, it is set up to provide information based on the assumption that AGW IS fact.

      That is why so many ancillary articles and reports are so farcical.

      Essentially if you start from entirely false premises you will actually inevitably end up with nonsense.

    • As you note, what goes up must come down, restoring the latent heat.

      When water evaporates from the surface it removes heat. The heat is carried upward to between 10,000 and 40,000 feet. link The water condenses, giving up the heat, and falls back to the surface. The water in each rain drop has less energy than it had as vapor. The latent heat doesn’t come back down. It eventually radiates to space.

      • “The heat is carried upward to between 10,000 and 40,000 feet.”
        Your link is referring to thunderstorms, and fairly extreme updrafts in that particular context. A lot of condensation happens at lower altitudes. Even in those thunderstorm updrafts, while the water can be carried a long way, it may condense at an early stage.

        My issue was the arithmetic in bold: “a likely global value for the trend in the evaporative cooling for each °C of additional warming is on the order of 7 ± 1 W/m2 per °C.”. That is just the loss at the surface. It reappears somewhere else. And it’s not true that the heat “can’t come down”. When the heat is transferred up by LH transport, the cooler surface is radiating less. There are a lot of things that need to be balanced before you can say what the net effect is.

      • commieBob June 11, 2017 at 3:47 am
        “The water in each rain drop has less energy than it had as vapor. The latent heat doesn’t come back down. It eventually radiates to space.”
        —————————————
        The earth radiates to space some of this radiation (not in the absorption bands of ghgs) reaches space unhindered, Some of the radiation will hit CO2, and other ghg, molecules and be absorbed to be again conductively transferred to other molecules including n2 o2. or radiated to other ghg molecules non-ghg molecules cannot radiate energy to space so transfer to these molecules has to be transferred to other ghg molecules, conductive transfer predominates until the collision rate is similar to the radiation emissive time. When the distance between ghg molecules gets very large then radiation will begin to escape the planet without further absoption in ghgs or conduction to any molecules.

        It verging on a vacuum before photons mfp is sufficiently large for the photon to leave the “earth”

      • Nick writes

        When the heat is transferred up by LH transport, the cooler surface is radiating less. There are a lot of things that need to be balanced before you can say what the net effect is.

        What mechanism do you propose allows the energy that has been transported high into the atmosphere to warm the surface again?

        You’re right that the net effect is unknown. Completely unknown…models dont model clouds using physics so they cant resolve it. So as a further question, how can we possibly know what the net effect will be in to the future?

      • Nick Stokes: That is just the loss at the surface. It reappears somewhere else. And it’s not true that the heat “can’t come down”. When the heat is transferred up by LH transport, the cooler surface is radiating less. There are a lot of things that need to be balanced before you can say what the net effect is.

        I see that you are doubling down. If ” there are a lot of things that need to be balanced before you can say what the net effect is”, then it is surely too soon for a massive effort to reduce CO2 emissions. The increased water vapor could produce increased cloud cover that would cool the Earth surface. However,, the increased transfer of latent heat from the surface to the cloud condensation layer most likely produces an increase in the rate of transfer of energy from the Earth to space. Overlooking that leads to an overestimate of surface heating by increased tropospheric CO2.

        And also, “just the loss at the surface” glosses over the fact that the surface is the most important part of the system affecting humans and other life.

      • “Yada yada yada…There are a lot of things that need to be balanced before you can say what the net effect is.”

        But the science is settled and taxation is the only remedy.

      • Nick Stokes June 11, 2017 at 4:42 am

        “My issue was the arithmetic in bold: “a likely global value for the trend in the evaporative cooling for each °C of additional warming is on the order of 7 ± 1 W/m2 per °C.”. That is just the loss at the surface. It reappears somewhere else.”

        Nick, you are correct … but the issue at hand is the temperature at the surface. Your claim is as wrong as saying that sweating doesn’t work to cool us down, because the water evaporated from our skin will condense and release its heat somewhere else …

        w.

      • TimTheToolMan,

        What mechanism do you propose allows the energy that has been transported high into the atmosphere to warm the surface again?

        While I don’t follow the CAGW crowd, that heat is given up to the surroundings. Some radiates to space, some is thermalized in the air that is transported to the Hadley circulation and is returned at the atmospheric downwelling at the great deserts. That air which descends has been wrung of its moisture and has been warmed by the condensation and freezing of the water. It then undergoes compression warming and gravitational warming as it descends to the surface. That of course is why there are great belts of deserts north and south of the tropics.

        I still think that most of it winds up in space, but to say all would be wrong.

      • Smueller June 11, 2017 at 4:59 am

        … The earth radiates to space some of this radiation …

        The infrared window is open from 8 um to 14 um. If we go to this Wien’s law calculator, we find that corresponds to peak emission temperatures between 192 °F and -87 &def;F. As far as I can tell, the top of a thunder cloud is well within that range. link It seems that most of the energy that reaches the top of the cloud would be able to radiate to space.

    • Nick how is that latent heat released?
      Where is it released?
      We both know…why dont you complete the circle for those who dont?

      • Enough is released to help maintain air temps at night to near dew point temp. Energy is stored during the day, and released late at night, but in this process a lot of energy is released to space, it just makes surface temps a little warmer.
        The enthalpy in tropical air at max temp is ~72KJ/m^3, drops about 9KJ/m^3 at night, US SW deserts have ~35KJ/m^3, and drop ~18KJ/m^3 at night.
        And Min T globally follows dew points. And dew points are independent of Co2, it just doesn’t have enough power of evaporation, plus most land areas, only have the water vapor the air mass carries with it to work with. Water limits the amount of water evaporated in tropical oceans, and water regulates cooling at independent of co2.

        This is why they have to make up data. Or change the definition of what their surface temp series is. The problem is co2 doesn’t linearly add to existing GHG processes.

    • restoring the latent heat

      What does that term even mean?

      Evaporative cooling moves heat from the surface to the clouds. Once it’s there it can escape earth, as LWIR more quickly. So more evaporative cooling means faster cooling of the surface.

      • Yep, it takes energy to move all this. It is called the hydrological cycle, and excellerating it, accelerates cooling.

        Nick S above said, “When the heat is transferred up by LH transport, the cooler surface is radiating less” but forgot to add, receiving less as well.

      • That sensible heat late in the morning(pre-dawn) actually slows temperature loss at the surface, probably speeds it up up the atm column, but at the surface cooling rates slow.
        Clear night

        Note the inflection point a little after 22:00

    • I don’t think the CSIRO will save Nick this time. Seriously Nick, your science is flawed. Explain and answer the questions.

    • Nick ignores the fact that more wv will lead to a less dense parcel of air. This speeds up the convection which must drive the wv higher into the atmosphere. When this happens the colder air condenses larger amounts of the wv.

      The bottom line is you get more lower altitude wv and less higher altitude wv.

      Which is more important? The higher altitude wv by more than an order of magnitude. Hence, besides getting more clouds you also REDUCE the radiation being “trapped” at precisely the place where it has the most effect. This is a double negative feedback

    • Nick
      In my experience the rain that falls is always cooler than the surface. In terms of latent heat, you are correct. You seem to have forgotten about sensible heat. You also seemed to have forgotten about kinetic energy, adiabatic lapse rate and blackbody radiation.

    • Nick Stokes: As you note, what goes up must come down, restoring the latent heat. It just moves heat from one place to another.

      I think you know better than that. The water vapor from the surface warms the tropospheric atmosphere, which then radiates the energy to space. The radiation is omnidirectional, but an increase in the water vapor transport produces an increase in the rate of radiation to space. the latent heat is not “restored” to the surface.

      • ” but an increase in the water vapor transport produces an increase in the rate of radiation to space”
        It may do, but that needs to be quantified. The regions of high troposphere that are radiating to space are too cold to sustain much water vapor. The LH transfer from surface to wherever it is cold enough to condense (usually not so far up) helps, but how much? My point here is that the 7 W/m2 quoted here at the surface is just a part of the story.

        As to the LH being somehow stuck up there, as K&T recounted, there are very large fluxes of heat up and down, and heat that was once latent is just as mobile as any other.

      • Nick Stokes: It may do, but that needs to be quantified. The regions of high troposphere that are radiating to space are too cold to sustain much water vapor. The LH transfer from surface to wherever it is cold enough to condense (usually not so far up) helps, but how much? My point here is that the 7 W/m2 quoted here at the surface is just a part of the story.

        This is a start on the quantification, and the surface is the most important part of the story for life on Earth and hence for the public policy debate about reducing fossil fuel use. You’ll have noticed that the expected increase in the LH transfer from the surface is close to the expected result of doubling CO2, which (if corroborated by other accounts [I wrote out an estimate about 2 years ago, and I am hopeful that many more will follow]) would make it hard for doubling the CO2 concentration to raise the surface temperature by 1C.

      • Nick and Matt: The only thing that cools the Earth is LWR escaping across the TOA from various altitudes. The rate of cooling depends on temperature and the probability that an emitted photon avoids being absorbed by CO2 or H2O. If enough heat escapes, then an unstable lapse rate develops and latent heat is connected upwards. But that can’t happen if the upper troposphere hasn’t emittEd radiation to space fast enough. That rate depends on how much water vapor is in the upper troposphere. As Nick says, it is relatively little – but it is still critically important. Relative humidity falls with altitude and that drying is important to radiative cooling to space. IIRC, the hot spot is created by increasing water vapor in the upper troposphere. More efficient drying with altitude means more radiative cooling to space and less cirrus.

      • Frank: The only thing that cools the Earth is LWR escaping across the TOA from various altitudes.

        How fast the energy transfers from the surface to the various altitudes matters.

      • Matt: If too much heat remains in the upper troposphere, convection stops. Carrying this to absurdity, even evaporation could cease as relative humidity rise to 100%.

      • Nick writes

        It may do, but that needs to be quantified.

        The effect of LH on moving energy higher into the atmosphere where it can be radiated away is just as much “unquestionable physics” as the idea the effective radiation level changes with more CO2. Of course there are other factors that must be taken into account. In both cases!

        Its just that somehow CO2 seems to have won the hearts of alarmists everywhere with the idea there will be dangerous net surface warming.

      • Frank: Matt: If too much heat remains in the upper troposphere, convection stops.

        Who says heat remains in the upper troposphere? It’s radiated omnidirectionally, and the rate of radiation, including radiation out to space, increases with temperature

    • Nick, Willis: the clue is in another direction, see this paper: http://onlinelibrary.wiley.com/doi/10.1002/2016JD025827/abstract
      They also used TRMM and other observations to conclude: The Iris ( Lindzen!) is real. If there is more convective rain in the tropics ( or better in the WPWP) than the upper air is dryer and they find less cirrus-clouds. This leads to more OLR, what means: more heat, more convective rain, less cirrus, cooling. A strong negative Feedback. From the paper:

      They estimate the ECS with comparing CMIP5-models with obs:

      The observed value in the upper figure is 108 and with this the second figure gives a ECS near 2 K/ 2*CO2.
      The clue is NOT more concective precipipation but less upper couds.
      best Frank

    • Not to be a stickler, but what Willis actually said was the reverse, “what comes down must go up”.

      Rainfall does not restore latent heat to the surface. Quite the reverse, rainfall restores the cooled transport medium to the surface. In addition, downdrafts around convection cells “restore” a lot of cold air to the surface.

  3. I think this must be the final nail in the coffin of the “Radiative Forcing” model.

    – The models don’t predict real-world results
    – Attempts to make the models more complex to model the complexities of the real world turn them into noise generators
    – The model (Radiative Forcing) they are built around is deeply flawed.

    • Just like the earth centered models of the solar system. Galileo and Copernicus were fighting a similar campaign.

    • Radiative forcing is based on radiative transfer according to the Schwarzschild equation. This equation uses terms for absorption and emission. The equation is used improperly in models regarding CO2 because the assumption is made that CO2 has an emissivity of 1, as if it were a perfect blackbody. CO2 is actually a lousy blackbody. Its highest measured emissivity is ~.2.

      Radiative forcing is real, and part of the energy balance. They just need to use correct values for the terms.

      • Radiative forcing is based on radiative transfer according to the Schwarzschild equation

        It also change throughout the night(and I don’t mean log cooling, which it’s also doing), so what it’s doing at 10PM is not what it’s doing at 4:00AM

  4. Yeah, The earth cools by perspiring.

    All that lubberly water vapour warm and wet rises to well above where the bulk of the CO2 exists, radiates gaily into space, and comes down as snow and cold rain.

    Massive negative feedback

    That’s why the IPCC calls it positive feedback of course….

  5. So reducing evaporation should lead to a warmer ocean? I can’t find it now — it is years since I read the reference — but somewhere out there is a paper about Israeli farmers increasing crop? fish? yields by floating light oil on ponds/paddy fields in order to speed up spring warming.

    Just imagine what would happens if we did that on an oceanic scale.
    .
    https://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/peril_oil_pollution.html

    Nearly there, Willis!

    Rgds

    JF

    • In earlier days of aquaculture, motor or similar oil was used in ponds to kill predatory insects prior to introducing very young stages of fish. Not sure how widespread it was, but now it would be a problem.

  6. It is a giant, gas-loaded Perkins Tube. That is a gravity assisted heat pipe. Heat pipes are known for their thermal conductivity but working against gravity limits heat flux if the hot reservoir is higher in gravimetric potential. When the heat source is beneath the heat sink, flux is only limited by fluid dynamics.

  7. Earth could soon be much rainier than scientists previously expected, NASA study warns

    http://www.dailymail.co.uk/sciencetech/article-4589792/Earth-soon-rainier-previously-expected.html
    As our planet continues to warm, the amount of rain that will fall in tropical regions will increase, research suggests.

    The study found that global climate models may underestimate the amount of rain that will fall in these regions, because they underestimate decreases in high clouds over the tropics seen in recent NASA observations.

    High-altitude tropical clouds trap heat in the atmosphere, but global warming appears to create fewer of these clouds, which would lead to the tropical atmosphere cooling – leading to increased tropical rainfall.

    OMG a feedback loop. It is runaway global raining. We are all going to drown.

    • “As our planet continues to warm, the amount of rain that will fall in tropical regions will increase, research suggests.”

      No shist Sherlock. Now, let’s put a number on that. How much additional rain needs to fall in tropical to completely counteract a CO2 increase of 200%?

      Is it 1%, 5%, 10%?

      If the forcing per doubling of CO2 is 0.6 W/m^2 then we expect two doubling, far more than a practical value, would heat by 1.2 degrees. Evaporative cooling, without the cloud cooling feedback, is easily larger than CO2 based heating.

    • “High-altitude tropical clouds trap heat in the atmosphere, but global warming appears to create fewer of these clouds, which would lead to the tropical atmosphere cooling – leading to increased tropical rainfall.”

      Um, the tropical atmosphere cooling? So, global warming leads to the warmest band of the atmosphere cooling . . and further settling of “the science”, no doubt . .

    • We have been doing something similar to that in Spain for centuries. The thing is called “Botijo”.

      https://en.wikipedia.org/wiki/Botijo

      A botijo, also called búcaro in Spanish, is a traditional Spanish porous clay container designed to contain water. The botijo has the property that once filled and placed in the sun, it cools the water that it contains, acting as an evaporative cooler.

      The botijo has a wide belly and one or more mouths where it is filled and one or more outputs called pitón o pitorro to drink from. The botijo is a typical element of Spanish culture and may vary in shape, color and material.

      Operation <
      The operating principle of the botijo is as follows: the stored water is filtered through the pores of the clay and in contact with the outside dry environment (characteristic of Mediterranean climate), it evaporates, producing a cooling (2.219 kilojoules per gram of evaporated water). The key for cooling it, is by the evaporation of bleed water, as the water evaporates, it extracts thermal energy from the water stored inside the jug.

      Mandatory pic: :-)

      BTW congratz to Rafa Nadal on his 10th Roland Garros Trophy. Nadal, master of clay.

  8. In my agrometeorological studies over several countries, I presented relationship between rainfall and radiation, evaporation and evapotranspiration. A review of this can be seen from Solar Energy 38:97-104, 1987 (Pergamen Journals Ltd] — The estimation of global solar radiation and evaporation through precipitation – A Note. This study includes for the northeast Brazil.

    However, vice versa is not true. That is evaporation does not relate directly rainfall. For true evaporation, require water resources to evaporate.

    Dr. S. Jeevananda Reddy

    • Dr S. Jeevananda Reddy: That is evaporation does not relate directly rainfall

      Thank you for the comment and the reference.

      Surely the total surface rainfall must equal the total surface evaporation? So the area-weighted rainfall change should be informative?

    • While a good point, how valid is a comparison of land compared to the greater ocean? There are gradients that show this, Texas a good one, where it gets drier to the west and down the coast from less rainfall and runoff (current conditions somewhat excepted). There are many complications but you get among other effects hypersalinities on the coast and caliche in the land when you pass the point where evaporation dominates. Clouds don’t seem to always cooperate.

      Are there similar places in the open ocean that stand still long enough to study gradients? Back to the ships!!

  9. It makes no sense to me that Figure 1 implies evaporative cooling over the deserts of Australia.

    • Of course it makes no sense, because it’s nonsense. There is no such thing as an evaporation meter. Ceres is reading the amount of water vapour over a particular location, then they are overlaying temperature and coming up with absolute humidity. Then they have the unmitigated gall to imply that the location they scanned is the source of evaporation. How can The Sahara, The centre of Australia and the oceans have the same evaporation rate?

      • There are evaporation pans. The rate of evaporation is monitored be most farmers.

        Prof Lloyd, the Nutty Professor who posts here, said a study of the evaporation pan numbers in South Africa for more than 1000 farms over a 100 year period. No change yet.

      • Crispin in Waterloo June 11, 2017 at 5:17 pm

        … The rate of evaporation is monitored be most farmers. …

        I think the evaporation rate per se is a red herring. Figure 1 is “Trends, Evaporative Cooling Per °C Warming”. Surely, to have any evaporative cooling, it is necessary to have some water to evaporate. As Alex points out, it is unlikely that a desert can exhibit the same evaporative cooling as the adjacent ocean.

      • Figure 1 does not show that deserts and oceans have the same evaporation rate, just that the change in evaporation rates have the same trend.

      • Alex,
        I get the feeling that our government research agencies employ a large number of technicians who have mastered multiplication tables, but employ very few real scientists with enquiring minds.

    • Ted June 12, 2017 at 10:38 pm

      … the change in evaporation rates have the same trend.

      The units are watts per meter squared per degree C. That implies that evaporation is actually happening.

      • I think that a distinction has to be made between potential evaporation rates, as measured with evaporation pans, and the actual, water-limited evaporation rate.

  10. the change in evaporative cooling per degree C ranges from a drop in evaporation of -70 watts per square metre per degree of surface warming (W/m2 per °C) …

    This does not make sense. All warm bodies of water (including the blue regions on the map) should show evaporative cooling (a negative feedback on warming). Evaporative cooling is always net cooling of the earth. Negative values (blue areas) imply some ocean areas are getting warmer than the sun makes them!

    • All warm bodies of water … should show evaporative cooling
      ================
      the likely explanation is increased cloudiness increasing albedo and thereby reducing evaporation. Perhaps if Willis added cloudiness to his calculations a more complete picture would emerge.

      from my years sailing in the pacific and indian oceans, those areas showing positive cooling in the eastern pacific for example are those area where the water is colder and the skies are clearer. those areas in SE asia for example showing negative cooling are those areas where the water is warmer and the skies are cloudier/hazier.

  11. Soil moisture is the key. As long as it exists, there is a negative feedback for increased forcing – any extra energy just goes into accelerating the evaporation-condensation cycle as if it were an energy dissipation dynamometer. But if soil moisture is lost, we get runaway warming and the dust bowl. Plants facilitate the negative feedback through transpiration. Desertification waxes and wanes, and is reversible with the help of plants, which happily happen to love carbon dioxide.

    • I was not clear on what Willis meant with the negative numbers, but figured it was just me.

      • True, although the climate that concerns Humans most is terrestrial. This discussion also points out how the warmistas conception of climate as a global average is not helpful. Most actual measurements are of terrestrial microclimates under some influence of man (crop cultivation, irrigation, urbanization). Humans have dramatically altered the climate of Palm Springs with golf courses, but not likely made any significant impact to the broad swaths of ocean surface that dominate the planet. The local climate may give a little where we push on it, but we are foolish to think we have enough leverage with fossil CO2 or fossil water vapor or direct heating to move the needle on the atmosphere-ocean heat budget.

  12. Great post.

    But I wonder if you could expand on what you meant by saying that

    in general it occurs preferentially where the surface is warmer than the surrounding areas

    • I was curious about that as well. Interesting to note that the ocean surface is on average warmer then land.

      • Naively I would expect less evaporation from land than from seas. To my surprise, Sahara or Australia do not stand out in Figure 1.

      • Also, I would think that for an area that has a larger temperature difference with surrounding areas, evaporated moisture will tend to move out faster, due to density differences, clearing the way for further evaporation.

    • Thanks, Joe. I meant that thunderstorms, being thermally-driven, occur preferentially over the warmer areas of the surface. This means that the hottest spots are preferentially cooled by the resulting increase in evaporation.

      w.

      • There are few thunderstorms in the deserts of Australia, and even fewer in Sahara.

  13. The point is “why does Willis need to calculate this?”

    This is obviously a major component of the climate of water-covered Earth.

    We spend billions of dollars putting these satellites in space and no scientist does anything with the data (except for the occasional distorted cherry pick of some of the data which is irrelevant to what the satellites are really showing).

    Why does the IPCC essentially ignore this component and how it might be changing.

    It is such a poorly developed field. Billions of dollars spent on research and Willis has to calculate one of the more important components at home in his spare time.

    • Because “Climate Science” is not a science, but a tool for bureaucrats, the UN, and NGO’s to forward an agenda. If Willis wrote up the above and tried to get funding from the feds, it would in the circular file instantaneously.

    • The US and the IPCC (UN) fund science to PROVE the existence of CO2 caused global warming. There is no money to be spent to disprove it. Thus any area that could be possible show that there are negative feedbacks to AGW are to be EXPRESSLY ignored. It is quite obvious in the climate science published by the AGW side. I have not even seen ONE negative feedback mechanism published by the AGW scientists. Surely there must be some negative feedbacks in a very surprisingly temperature world such as ours, yet they cannot (more correctly… will not) find any.

    • The whole thing is politics, not science. If they acknowledged plain truths about climate history, negative temperature feedbacks or the fact that there has been no warming for nearly 20 years, the whole multi-trillion dollar farce would collapse! Therefore, they avoid looking for that which they do not wish to see.

    • “We spend billions of dollars putting these satellites in space and no scientist does anything with the data …”

      “Why does the IPCC essentially ignore this component and how it might be changing.”

      I’m thinkin’ that first quote there is perhaps not truly true . . to answer the second ; )

  14. Don’t forget Willis, a likely global value for the trend in the atmospheric heating via condensation of water vapor is for each °C of additional warming is on the order of 7 ± 1 W/m2 per °C. There really is no “cooling” just moving the energy from one place to another.

    • LA, disagree. The higher in the troposphere the condensation, the easier the heat can radiate to space. Less water vapor, and ‘thinner’ remaining CO2 layer. And there is also Lindzen’s cirrus mediated adaptive iris.

      • It doesn’t matter where the outbound heat radiates from. The “cooling” is balanced by the “heating,” just in a different place. In effect there is no “cooling.”

      • Luis Anastasia: It doesn’t matter where the outbound heat radiates from. The “cooling” is balanced by the “heating,” just in a different place. In effect there is no “cooling.”

        You missed the point about latent heat transfer. The latent heat does not return to the surface, so there is net cooling of the surface, and net cooling of the whole system.

      • Matthew, evaporation does not add to, nor subtract from the “net cooling of the whole system.” The only way the “whole system” can cool is for an EM photon to leave the system at TOA. Evaporation does not emit EM photons.

      • You are correct ferdberple, moving heat energy from one place on the planet to another is neither “net heating” nor “net cooling.” Heat can come from Sun, radioactive decay or tidal friction, but there is only one way for “net cooling” to occur, that is via EM photons escaping.

      • LA says, ” The only way the “whole system” can cool is for an EM photon to leave the system at TOA. Evaporation does not emit EM photons.,

        Not correct IMV. There are only two ways for any system in a radiative balance to change energy content. Either a change in the input, ( The sun) or a change in the residence time of energy in the system.

        Evaporation is not required to emit photons to space, only to accurate the process whereby they are radiated. Our system is a heat engine, and accelerating the hydrological cycle shortens the residence time pf converting heat to the location of emission.

        Your car under an increase in energy, accelerates its cooling water more efficiently so it does not overheat. In affect the water movement accelerates the movement of conducted and convected heat to the radiator, thus shortening the residence time of heat energy within the engines system.

      • Typo correction,… “Evaporation is not required to emit photons to space, only to accurate ( change accurate to accelerate) the process whereby they are radiated….”

      • Luis writes

        but there is only one way for “net cooling” to occur, that is via EM photons escaping.

        And any effect that moves the energy into location that allow the photons to escape the earth and its atmosphere is one that is a cooling effect. Clearly any effect that gets energy higher into the atmosphere qualifies.

  15. I’m curious about the “knee” in the second graph from 0ᵒ to ~-20ᵒ. Any idea what the reason is? More water in the Southern Hemisphere? Thunderstorms?

  16. Noted on Judith Curry’s Climate Etc.:
    “Data defy notion that seas get fresher with more #rain and saltier with more #evaporation.”

    http://bit.ly/2rI6maD

    The use of “notion,” here, is evidently pejorative, and the conclusion is counter-intuitive. I haven’t time to check, but I suspect the data have been subjected to a novel methodology.

  17. Since what comes down must go up, we can use the Tropical Rainfall Measuring Mission (TRMM) satellite rainfall data to calculate the corresponding rainfall-related evaporation.

    How does the satellite measure surface rainfall?

  18. The normal way potential evapotranspiration is calculated is by the Penman formula which uses temperature, wind speed, humidity and solar radiation. An analysis based almost entirely on temperature will be misleading.

  19. When water or ice is present at the surface, the surface temperature will approach the DP/FP. This is also applicable to water/ice in clouds. These surfaces will radiate at that temperature. If you know the DP and pressure, you can calculate specific humidity and amount of perceptible water. From the rate of change in perceptible water we can calculate the rates of energy transfer associated with evaporation/precipitation. We should be able to do mass and energy balances on vertical columns of air. In the tropics, Thunderstorms are pumping moisture (and CO2) into the upper atmosphere. At the poles, moisture (and CO2) are being delivered from the upper atmosphere to the frozen surface. The moisture will freeze while the CO2 will be carried over the ice until it reaches open water sink.

  20. “…However … as far as I can find it is not included in the IPCC analysis of all feedbacks…”

    Very true. The IPCC doesn’t want to hear about it.

    The broader term is evapotranspiration. The IPCC mentions it briefly and cherry-picks a few findings.

    One of the water authorities that I do consulting for picked 3 climate models (CCSM, HadCM3, and GFDL) with nearly identical predictions (errr, projections) of future temperatures and downscaled them to the regional level. Using the same rainfall-runoff models for each, they were able to reproduce historical river flows quite well. But when it came to future projections…one suggested a ridiculous reduction in river flows, one said things would be about the same, and one said flows would be about the same for most months but increase dramatically during certain periods of the year. When it came to evapotranspiration, they suggested dramatic reduction, substantial increase, and about the same, respectively. Lots of disagreement and nonsense and absolutely no guidance on future water supply issues.

    They then took a number of GCMs and applied 10 different evapotranspiration models across the US, looking at the difference between projected precipitation and evapotranspiration. The results couldn’t have varied more between the evapotranspiration models, ranging from a net increase in runoff and storage everywhere in the US to runaway desertification of the entire US while covering everything in-between.

    • Michael: Evaporative cooling or evapotranspiration is only important for surface, not TOA, energy [im]balance. Traditional feedbacks change the TOA flux. Nevertheless, changes in evaporation with surface temperature are linked to ECS. See my comment below.

      • It appears you would agree that errors in modeling are substantial in this regard.

    • I have done similar calculations in a range of countries. Apart from the fact that the trend for temperature is always upwards, there is little agreement between the models.

  21. Willis: The average water molecule spends 9 days in the atmosphere between the time it leaves the surface as vapor and returns to the surface as liquid. (Total precipitable water vapor in column divided by precipitation rate.). A 10 mph wind could carry water vapor more than 2000 miles in 9 days. So the site of evaporation (where evaporative cooling occurs) and the site of condensation (where the latent heat is released several km above the surface) and the site of rainfall can be very different. Rain falls from ascending air masses.

    In the tropics, trade winds generally sweep evaporated water into the ITCZ, where rising air causes it to precipitate. In temperate zones, weather fronts can determine where rain falls. In some cases, such as localized thunderstorms, evaporation/evaporative cooling and precipitation may occur in the same grid cell, but this isn’t the typical situation. So I respectfully question whether your plots of how evaporative cooling varies with Ts are meaningful.

    • Evaporation rate also is dependent on humidity. Convection is highly driven by the hydrologic cycle. Rising water vapor shoves air into the atmospheric wringer of the tropopause. This forces dry air down sweeping more water vapor into convection.

  22. Luis Anastasia June 11, 2017 at 10:01 am
    You are correct ferdberple, moving heat energy from one place on the planet to another is neither “net heating” nor “net cooling.” Heat can come from Sun, radioactive decay or tidal friction, but there is only one way for “net cooling” to occur, that is via EM photons escaping.

    Luis, I do not think people will argue that the only EM photons cool the planet, the issue is, do the number of EM photons change, and what effects do those photons have/experience on their way from the surface and top of clouds to out of space?

    Are additional clouds a help or hindrance, is a change on CO2 concentration a help or hindrance to the flow of EM photons?

    And what experiments support either view?

    • I will argue that point. Not all heat is lost as photons. Some heat is carried away from the planet in the kinetic energy of molecules that happen to achieve escape velocity at TOA. All natural hydrogen gas on Earth is produced by nuclear chemistry under ground and migrates rapidly upward through the atmosphere to be lost this way, and presumably fractions of the lighter diatomic gases and especially their even lighter ionized atoms as well. Molecules can achieve escape velocity by kinetic motion or by electric field potentials. At the same time, there is interplanetary matter being swept up by the earth that has been cold-soaked to low sensible heat levels but has considerably kinetic energy of relative motion. Curious if anyone is aware of research that attempts to quantify this heat budget.

      • There must be some work on the mass, Google reveals numbers of 40,000 to 50,000 t per year but I suspect there is significant uncertainty in magnitude and changes in flux.
        Q=mct. My hunch is it’ll be tiny, but i’m off to find an envelope!

  23. Willis: Above you discuss evaporative cooling as a feedback. Changes in evaporative cooling are critical to surface energy balance. If evaporation increases at a C-C rate of 7%/K, that is 5.6 W/m2/K.

    If ECS is high, say 3.7 K/doubling, then the change in the TOA flux with rising surface temperature must be 1 W/m2/K ( 3.7 W/m2/doubling divided by 3.7 K/doubling ). So, if ECS is high, only about 1 W/m2 more heat escapes to space or is reflected back to space for each degC the planet warms.

    Obviously, we can’t have evaporative cooling sending something like 5.6 W/m2/K up from the surface indefinitely and only 1 W/m2/K escape to space. So feedback in evaporative cooling is as critical to ECS as traditional feedbacks. This is important work.

  24. It seems to me you could partially answer Nick Stoke’s comment by comparing the low altitude temperature with the high altitude temperature for those same gridcells that are showing massive evaporative cooling and see how they compare to the low vs. high for low evaporative cooling.

    • Thanks, Peter. Nick’s basic point is that the whole system is not cooled when water evaporates at the surface. On the simplest level, this is true. However, there are other issues at play.

      The main issue is … thunderstorms. Much of the tropical rain that we see in Figure 1 comes from thunderstorms. The intensity of tropical rainfall is a result of the increased evaporation right at the base of the thunderstorm. This increased evaporation is driven by the winds at the base of the storm. These winds increase the evaporation up to five-fold or more.

      Now, what happens to the energy removed from the surface at the base of the thunderstorm? As Nick points out, it is released when the water condenses. However, the story doesn’t stop there. The released heat warms the air at the cloud base. This warmed air then rises up through the cumulus tower, and finally exits at the top of the tower.

      So let’s look at the path taken by the heat. It starts out as thermal energy at the surface. It is converted to latent heat by the evaporation of the water. It is converted back to thermal energy by condensation at the base of the cumulus tower. It then rises through the center of that tower to exit high in the troposphere.

      There are two things to note about this thermal journey.

      First, the energy has moved from the surface to the upper part of the troposphere. Up there it is much freer to radiate to space. This is because there is less CO2 and much, much less water vapour than at the surface.

      Second, at no point during the journey is the energy exposed to the greenhouse gases. From the surface to the base of the cloud it is transported physically as latent heat. And during its travel from the base of the cloud to the upper troposphere, the warmed air is shrouded by the cumulus tower.

      At no point is the energy free to radiate to the open atmosphere.

      This means that the thunderstorm is able to pipe the heat from the surface to the upper troposphere without exposing it to most of the poorly-named “greenhouse effect”.

      And by avoiding the “greenhouse effect” in the trip from the surface to the upper atmosphere, it allows for much greater energy loss to space than we would see otherwise.

      To make a long story short, Nick is right in the short run (surface to the lifting condensation level), but he’s left out the rest of the vertical voyage.

      Best to all,

      w.

  25. I question the premise: “Short version—when the earth’s surface gets warmer, we get more evaporation and thus more rainfall. Since what comes down must go up, we can use the Tropical Rainfall Measuring Mission (TRMM) satellite rainfall data to calculate the corresponding rainfall-related evaporation.”

    1) There is no need for the moisture in the atmosphere to remain constant. What must come up, does not need to come down. In other words, the amount of moisture in the air does not have to be constant.

    2) Just like evaporation is a cooling process, condensation is a warming process. If you assume that there is no net gain in air moisture, then you are assuming that there is no net evaporative cooling. Rainfall seems like a poor measure of evaporation.

    3) It is curious to me how close that picture looks like the El Nino pattern. I wonder if what you are measuring is only an approximation of the ENSO cycle.

  26. Willis

    “This was quite encouraging. I had previously assumed that as we went towards the poles, the trend would continue to go more negative. But both in the northern hemisphere (positive latitude) and the southern hemisphere (negative latitude), the trend is heading back towards zero as we go towards the poles. This would indicate that the values nearer to the poles might be around zero”

    “SO … I think we can reasonably estimate that the average trend in the unmeasured areas of the globe shown in Figure 1 is on the order of -0.5°C. Recalling that the area from 40°N to 40°S is about 2/3 of the globe, and that the average for that area is 10.7 W/m2 per °C, that means that the global average is (1/3) * -0.5 + (2/3) * 10.7 = 7.0 W/m2 per °C.”

    I was looking at figure 2 and if the curve was a Mesokurtic curve I could go along with your estimate of 30 to 90 degrees but I see a Polymonial curve and this fits the global air circulation at 30 60 90 degrees and my guess based looking at figure 2 is 15 watt m 2 at 60 degrees.

    0 & 60 degrees is low pressure.
    30 & 90 degrees is high pressure and deserts.
    0 & 45 degrees and wet forests.

    Interesting is the peak of the curve is not at the equator and the step in the curve? Any one have thoughts on them?

  27. WE: “Nick, you are correct … but the issue at hand is the temperature at the surface. Your claim is as wrong as saying that sweating doesn’t work to cool us down, because the water evaporated from our skin will condense and release its heat somewhere else …”

    Surely this comparison is faulty. Sweating cools us down precisely because when the evaporated sweat condenses it condenses elsewhere on the surface, or later, or over a wider area of the surface. If we look at the total system there is no “cooling” of the surface by evaporation. There is an unbroken cycle of cooling by evaporation and corresponding warming by condensation. The cooling is local and temporary and does not exist for the whole system. (You can say that some of the energy from evaporation leaks into space but that’s a different issue from sweating, i.e. local versus whole system.)

  28. I should have said “corresponding warming by condensation and precipitation” of course. When the rainfall hits the ground, it warms it.

    • You are missing the Earth’s heat engine.
      Increase convection and you accelerate the motion of energy to the LOCATION where heat escapes earth system via radiation.

      Take your car merrily driving along at a constant. Speed and T. Now punch it, sending considerable energy to your car. If you do not accelerate the hydrological system in your car, which is converting conducted heat to the place where it radiates, curiously called the radiator, the car will overheat. Fortunaly the motion of water and air from the fan in your car quickens it’s pace, thus shortening the residence time of heat in the system and your car stays the same T despite greater input because the response of water and air has REDUCED THE RESIDENCE time of heat in your car’s engine.

      The earth does the same thing. The Earth’s radiator is up high in the atmosphere. Accelerating the hydrological cycle expedites the movement of energy in air and water to Earth’s radiator, thus shortening the residence time of energy in Earth’s system, NOT just at the surface.

      This is, without questuon, a negative feedback to any increase in the energy of Earth’s system. I appreciate Willis’s attempt to quantify it.

  29. Willis, your figure 2 seems to have invented evaporative warming – i.e. cooling less than zero. Surely that can never be the case?

    Also where the rain falls and where the rain evaporated from are two very different places once non-convective weather is concerned, or there would never be much rain in Kansas. The frontal weather and orographic precipitation are normally caused by lifting of humid air until the water vapor condenses out and precipitates. The humidity may have come from hundreds of miles away so the frontal rain in Kansas has no relationship to surface heating in Kansas nor necessarily any relationship with Kansas latitude. Consider a pulse of humid air from the Gulf of Mexico carried North in a frontal system dropping rain, I think that there are relationships there but they are a lot more complex once you move away from convective weather over the oceans.

  30. Willis, the great thing about your analyses is that they would make, together, a fine climate science for “Dummies”. I say this with the greatest respect. All your readers scientists, engineers, poets, social scientists (whether they wish to or not) can understand your simple exposition and logic. You have a gift. I have no doubt you would have a best seller if you produced a “CliSci by Colours” “(I thought” by numbers” in allusion to the popular “paint by… numbers” but that may scare many off). It would have the added bonus of revealing the wondrous stuff of satellite instruments and the beauty of the scientific method- “… Hey, I can understand this stuff…”

  31. Things left out. Thunderstorms are violent especially “towering” types. Are they well researched?
    Some of the precipitation may be/usually is hail which may or may not make it to the surface before melting. Lots of energy transfers.
    Joe and Joe at Weather Bell talk about the “Texas perma-drouth” and how poorly the models do forecasting long range weather more less climate.

  32. Willis, have you ever considered subtracting these two graphs? The predicted and observed tropospheric hotspot. Looking at the equator, it seems plain that there is tropospheric cooling in the observed data, while the climate models predict warming. I see this as strong evidence that water feedback is negative.

    A similar effect is visible comparing northern and southern hemispheres, with cooling in the south consistent with increased oceans, and warming in the north consistent with increased land. The graphs are from David Evans’s 2008 work.


  33. Willis, have you ever considered subtracting these two graph’s? The one of the left is model projection based on the assumption of positive water feedback. The one of the right is observed. It would seem to me that the difference between these could be used to calculate actual water feedback. Looking at the observed warming on the equator and southern hemisphere as compared to the northern hemisphere, it does appear consistent with your graph above.

Comments are closed.