Guest Essay by Willis Eschenbach
Abstract
The Thermostat Hypothesis is that tropical clouds and thunderstorms, along with other emergent phenomena like dust devils, tornadoes, and the El Nino/La Nina alteration, actively regulate the temperature of the earth. This keeps the earth at an equilibrium temperature.
Several kinds of evidence are presented to establish and elucidate the Thermostat Hypothesis – historical temperature stability of the Earth, theoretical considerations, satellite photos, and a description of the equilibrium mechanism.
Historical Stability
The stability of the earth’s temperature over time has been a long-standing climatological puzzle. The globe has maintained a temperature of ± ~ 3% (including ice ages) for at least the last half a billion years during which we can estimate the temperature. During the Holocene, temperatures have not varied by ±1%. And during the glaciation periods, the temperature was generally similarly stable as well.
In contrast to Earth’s temperature stability, solar physics has long indicated (Gough, 1981; Bahcall et al., 2001) that 4 billion years ago the total solar irradiance was about three-quarters of the current value. In early geological times, however, the earth was not correspondingly cooler. Temperature proxies such as deuterium/hydrogen ratios and 16O/18O ratios show no sign of a corresponding warming of the earth over this time. Why didn’t the earth warm as the sun warmed?
This is called the “Faint Early Sun Paradox” (Sagan and Mullen, 1972), and is usually explained by positing an early atmosphere much richer in greenhouse gases than the current atmosphere.
However, this would imply a gradual decrease in GHG forcing which exactly matched the incremental billion-year increase in solar forcing to the present value. This seems highly unlikely.
A much more likely candidate is some natural mechanism that has regulated the earth’s temperature over geological time.
Theoretical Considerations
Bejan (Bejan 2005) has shown that the climate can be robustly modeled as a heat engine, with the ocean and the atmosphere being the working fluids. The tropics are the hot end of the heat engine. Some of that tropical heat is radiated back into space. Work is performed by the working fluids in the course of transporting the rest of that tropical heat to the Poles. There, at the cold end of the heat engine, the heat is radiated into space. Bejan showed that the existence and areal coverage of the Hadley cells is a derivable result of the Constructal Law. He also showed how the temperatures of the flow system are determined.
“We pursue this from the constructal point of view, which is that the [global] circulation itself represents a flow geometry that is the result of the maximization of global performance subject to global constraints.”
“The most power that the composite system could produce is associated with the reversible operation of the power plant. The power output in this limit is proportional to
where q is the total energy flow through the system (tropics to poles), and TH and TL are the high and low temperatures (tropical and polar temperatures in Kelvins).
The system works ceaselessly to maximize that power output. Here is a view of the entire system that transports heat from the tropics to the poles.
Figure 1. The Earth as a Heat Engine. The equatorial Hadley Cells provide the power for the system. Over the tropics, the sun (orange arrows) is strongest because it hits the earth most squarely. The length of the orange arrows shows relative sun strength. Warm dry air descends at about 30N and 30S, forming the great desert belts that circle the globe. Heat is transported by a combination of the ocean and the atmosphere to the poles. At the poles, the heat is radiated to space.
In other words, flow systems such as the Earth’s climate do not assume a stable temperature willy-nilly. They reshape their own flow in such a way as to maximize the energy produced and consumed. It is this dynamic process, and not a simple linear transformation of the details of the atmospheric gas composition, which sets the overall working temperature range of the planet.
Note that the Constructal Law says that any flow system will “quasi-stabilize” in orbit around (but never achieve) some ideal state. In the case of the climate, this is the state of maximum total power production and consumption. And this in turn implies that any watery planet will oscillate around some equilibrium temperature, which is actively maintained by the flow system. See the paper by Ou listed below for further information on the process.
Climate Governing Mechanism
Every heat engine has a throttle. The throttle is the part of the engine that controls how much energy enters the heat engine. A motorcycle has a hand throttle. In an automobile, the throttle is called the gas pedal. It controls incoming energy.
The stability of the earth’s temperature over time (including alternating bi-stable glacial/interglacial periods), as well as theoretical considerations, indicates that this heat engine we call climate must have some kind of governor controlling the throttle.
While all heat engines have a throttle, not all of them have a governor. In a car, a governor is called “Cruise Control”. Cruise control is a governor that controls the throttle (gas pedal). A governor adjusts the energy going to the car engine to maintain a constant speed regardless of changes in internal and external forcing (e.g. hills, winds, engine efficiency, and losses).
We can narrow the candidates for this climate governing mechanism by noting first that a governor controls the throttle (which in turn controls the energy supplied to a heat engine). Second, we note that a successful governor must be able to drive the system beyond the desired result (overshoot).
(Note that a governor, which contains a hysteresis loop capable of producing overshoot, is different from a simple negative feedback of the type generally described by the IPCC. A simple negative feedback can only reduce an increase. It cannot maintain a steady state despite differing forcings, variable loads, and changing losses. Only a governor can do that.)
The majority of the earth’s absorption of heat from the sun takes place in the tropics. The tropics, like the rest of the world, are mostly ocean; and the land that is there is wet. The steamy tropics, in a word. There is little ice there, so the clouds control how much energy enters the climate heat engine.
I propose that two interrelated but separate mechanisms act directly to regulate the earth’s temperature — tropical cumulus and cumulonimbus clouds. Cumulus clouds are the thermally-driven fluffy “cotton ball” clouds that abound near the surface on warm afternoons. Cumulonimbus clouds are thunderstorm clouds, which start life as simple cumulus clouds. Both types of clouds are part of the throttle control, reducing incoming energy. In addition, the cumulonimbus clouds are active refrigeration-cycle heat engines, which provide the necessary overshoot to act as a governor on the system.
A pleasant thought experiment shows how this cloud governor works. It’s called “A Day In the Tropics”.
I live in the deep, moist tropics, at 9°S, with a view of the South Pacific Ocean from my windows. Here’s what a typical day looks like. In fact, it’s a typical summer day everywhere in the Tropics. The weather report goes like this:
Clear and calm at dawn. Light morning winds, clouding up towards noon. In the afternoon, increasing clouds and wind with showers and thundershowers developing as the temperature rises. Thunderstorms continuing after dark, and clearing some time between sunset and early hours of the morning, with progressive clearing and calming until dawn.
That’s the most common daily cycle of tropical weather, common enough to be a cliché around the world.
It is driven by the day/night variations in the strength of the sun’s energy. Before dawn, the atmosphere is typically calm and clear. As the ocean (or moist land) heats up, air temperature and evaporation increase. Warm moist air starts to rise. Soon the rising moist air cools and condenses into clouds. The clouds reflect the sunlight. That’s the first step of climate regulation. Increased temperature leads to clouds. The clouds close the throttle slightly, reducing the energy entering the system. They start cooling things down. This is the negative feedback part of the cloud climate control.
The tropical sun is strong, and despite the negative feedback from the cumulus clouds, the day continues to heat up. The more the sun hits the ocean, the more warm, moist air is formed, and the more cumulus clouds form. This, of course, reflects more sun, and the throttle closes a bit more. But the day continues to warm.
The full development of the cumulus clouds sets the stage for the second part of temperature regulation. This is not simply negative feedback. It is the climate governing system. As the temperature continues to rise, as the evaporation climbs, some of the fluffy cumulus clouds suddenly transform themselves. They rapidly extend skywards, quickly thrusting up to form cloud pillars thousands of meters high. In this way, cumulus clouds are transformed into cumulonimbus or thunderstorm clouds.
The columnar body of the thunderstorm acts as a huge vertical heat pipe. The thunderstorm sucks up warm, moist air at the surface and shoots it skyward. At altitude the water condenses, transforming the latent heat into sensible heat. The air is rewarmed by this release of sensible heat and continues to rise within the thunderstorm tower.
At the top, the rising much dryer air is released from the cloud up high, way above most of the CO2, water vapor, and other greenhouse gases. In that rarified atmosphere, the air is much freer to radiate to space. By moving inside the thunderstorm heat pipe, the rising air bypasses any interaction with most greenhouse gases and comes out near the top of the troposphere. During the transport aloft, there is no radiative or turbulent interaction between the rising air inside the tower and the surrounding lower and middle troposphere. Inside the thunderstorm, the rising air is tunneled through most of the troposphere to emerge at the top.
In addition to reflecting sunlight from their top surface as cumulus clouds do, and transporting heat to the upper troposphere where it radiates easily to space, thunderstorms cool the surface in a variety of other ways, particularly over the ocean.
1. Wind driven evaporative cooling. Once the thunderstorm starts, it creates its own wind around the base. This self-generated wind increases evaporation in several ways, particularly over the ocean.
a) Evaporation rises linearly with wind speed. At a typical squall wind speed of 10 meters per second (“m/s”, about 20 knots or 17 miles per hour), evaporation is about ten times greater than at “calm” conditions (conventionally taken as 1 m/s).
b) The wind increases evaporation by creating spray and foam, and by blowing water off of trees and leaves. These greatly increase the evaporative surface area, because the total surface area of the millions of droplets is evaporating as well as the actual surface itself.
c) To a lesser extent, the surface area is also increased by wind-created waves (a wavy surface has a larger evaporative area than a flat surface).
d) Wind-created waves in turn greatly increase turbulence in the atmospheric boundary layer. This increases evaporation by mixing dry air down to the surface and moist air upwards.
e) As spray rapidly warms to air temperature, which in the tropics can be warmer than ocean temperature, evaporation also rises above the sea surface evaporation rate.
2. Wind and wave driven albedo increase. The white spray, foam, spindrift, changing angles of incidence, and white breaking wave tops greatly increase the albedo of the sea surface. This reduces the energy absorbed by the ocean.
3. Cold rain and cold wind. As the moist air rises inside the thunderstorm’s heat pipe, water condenses and falls. Since the water is originating from condensing or freezing temperatures aloft, it cools the lower atmosphere it falls through, and it cools the surface when it hits. Also, the droplets are being cooled as they fall by evaporation.
In addition, the falling rain entrains a cold wind. This cold wind blows radially outwards from the center of the falling rain, cooling the surrounding area. This is quite visible in the video below.
4. Increased reflective area. White fluffy cumulus clouds are not very tall, so basically they only reflect from the tops. On the other hand, the vertical pipe of the thunderstorm reflects sunlight along its entire length. This means that thunderstorms reflect sunlight from an area of the ocean out of proportion to their footprint, particularly in the late afternoon.
5. Modification of upper tropospheric ice crystal cloud amounts (Lindzen 2001, Spencer 2007). These clouds form from the tiny ice particles that come out of the smokestack of the thunderstorm heat engines. It appears that the regulation of these clouds has a large effect, as they are thought to warm (through IR absorption) more than they cool (through reflection).
6. Enhanced night-time radiation. Unlike long-lived stratus clouds, cumulus and cumulonimbus often die out and vanish in the early morning hours, leading to the typically clear skies at dawn. This allows greatly increased nighttime surface radiative cooling to space.
7. Delivery of dry air to the surface. The air being sucked from the surface and lifted to altitude is counterbalanced by a descending flow of replacement air emitted from the top of the thunderstorm. This descending air has had the majority of the water vapor stripped out of it inside the thunderstorm, so it is relatively dry. The dryer the air, the more moisture it can pick up for the next trip to the sky. This increases the evaporative cooling of the surface.
8. Increased radiation through descending dry air. The descending dry air mentioned above is far more transparent to surface radiation than normal moist tropical air. This increases overall radiation to space.
In part because they utilize such a wide range of cooling mechanisms, cumulus clouds and thunderstorms are extremely good at cooling the surface of the earth. Together, they form the governing mechanism for the tropical temperature.
But where is that mechanism?
The problem with my thought experiment of describing a typical tropical day is that it is always changing. The temperature goes up and down, the clouds rise and fall, day changes to night, the seasons come and go. Where in all of that unending change is the governing mechanism? If everything is always changing, what keeps it the same month to month and year to year? If conditions are always different, what keeps it from going off the rails?
In order to see the governor at work, we need a different point of view. We need a point of view without time. We need a timeless view without seasons, a point of view with no days and nights. And curiously, in this thought experiment called “A Day In the Tropics”, there is such a timeless point of view, where not only is there no day and night, but where it’s always summer.
The point of view without day or night, the point of view from which we can see the climate governor at work, is the point of view of the sun. Imagine that you are looking at the earth from the sun. From the sun’s point of view, there is no day and night. All parts of the visible face of the earth are always in sunlight—the sun never sees the nighttime. And it’s always summer under the sun.
If we accept the convenience that the north is up, then as we face the earth from the sun, the visible surface of the earth is moving from left to right as the planet rotates. So the left-hand edge of the visible face is always at sunrise, and the right-hand edge is always at sunset. Noon is a vertical line down the middle. From this timeless point of view, morning is always and forever on the left, and afternoon is always on the right. In short, by shifting our point of view, we have traded time coordinates for space coordinates. This shift makes it easy to see how the governor works.
The tropics stretch from left to right across the circular visible face. We see that near the left end of the tropics, after sunrise, there are very few clouds. Clouds increase as you look further to the right. Around the noon line, there are already cumulus. And as we look from left to right across the right side of the visible face of the earth, towards the afternoon, more and more cumulus clouds and increasing numbers of thunderstorms cover a large amount of the tropics.
It is as though there is a graduated mirror shade over the tropics, with the fewest cloud mirrors on the left, slowly increasing to extensive cloud mirrors and thunderstorm coverage on the right.
After coming up with this hypothesis that as seen from the sun, the right-hand side of the deep tropical Pacific Ocean would have more clouds than the left-hand side), I thought “Hey, that’s a testable proposition to support or demolish my hypothesis”. So in order to investigate whether this postulated increase in clouds on the right-hand side of the Pacific actually existed, I took an average of 24 pictures of the Pacific Ocean taken at local noon on the 1st and 15th of each month over an entire year. I then calculated the average change in albedo and thus the average change in forcing at each time. Here is the result:
Figure 2. Average of one year of GOES-West weather satellite images taken at satellite local noon. The Intertropical Convergence Zone is the bright band in the yellow rectangle. Local time on earth is shown by black lines on the image. Time values are shown at the bottom of the attached graph. The red line on the graph is the solar forcing anomaly (in watts per square meter) in the area outlined in yellow. The black line is the albedo value in the area outlined in yellow.
The graph below the image of the earth shows the albedo and solar forcing in the yellow rectangle which contains the Inter-Tropical Convergence Zone. Note the sharp increase in the albedo between 10:00 and 11:30. You are looking at the mechanism that keeps the earth from overheating. It causes a change in insolation of -60 W/m2 between ten and noon.
Now, consider what happens if for some reason the surface of the tropics is a bit cool. The sun takes longer to heat up the surface. Evaporation doesn’t rise until later in the day. Clouds are slow to appear. The first thunderstorms form later, fewer thunderstorms form, and if it’s not warm enough those giant surface-cooling heat engines don’t form at all.
And from the point of view of the sun, the entire mirrored shade shifts to the right, letting more sunshine through for longer. The 60 W/m2 reduction in solar forcing doesn’t take place until later in the day, increasing the local insolation.
When the tropical surface gets a bit warmer than usual, the mirrored shade gets pulled to the left, and clouds form earlier. Hot afternoons drive thunderstorm formation, which cools and air conditions the surface. In this fashion, a self-adjusting cooling shade of thunderstorms and clouds keeps the afternoon temperature within a narrow range.
Now, some scientists have claimed that clouds have a positive feedback. Because of this, the areas where there are more clouds will end up warmer than areas with fewer clouds. This positive feedback is seen as the reason that clouds and warmth are correlated.
I and others take the opposite view of that correlation. I hold that the clouds are caused by the warmth, not that the warmth is caused by the clouds.
Fortunately, we have way to determine whether changes in the reflective tropical umbrella of clouds and thunderstorms are caused by (and thus limiting) overall temperature rise, or whether an increase in clouds is causing the overall temperature rise. This is to look at the change in albedo with the change in temperature. Here are two views of the tropical albedo, taken six months apart. August is the warmest month in the Northern Hemisphere. As indicated, the sun is in the North. Note the high albedo (areas of light blue) in all of North Africa, China, and the northern part of South America and Central America. By contrast, there is low albedo in Brazil, Southern Africa, and Indonesia/Australia.
Figure 3. Monthly Average Albedo. Timing is half a year apart. August is the height of summer in the Northern Hemisphere. February is the height of summer in the Southern Hemisphere. Light blue areas are the most reflective (greatest albedo)
In February, on the other hand, the sun is in the South. The albedo situation is reversed. Brazil and Southern Africa and Australasia are warm under the sun. In response to the heat, clouds form, and those areas now have a high albedo. By contrast, the north now has a low albedo, with the exception of the reflective Sahara and Rub Al Khali Deserts.
Clearly, the cloud albedo (from cumulus and cumulonimbus) follows the sun north and south, keeping the earth from overheating. This shows quite definitively that rather than the warmth being caused by the clouds, the clouds are caused by the warmth.
Quite separately, these images show in a different way that warmth drives cloud formation. We know that during the summer, the land warms more than the ocean. If temperature is driving the cloud formation, we would expect to see a greater change in the albedo over land than over the ocean. And this is clearly the case. We see in the North Pacific and the Indian Ocean that the sun increases the albedo over the ocean, particularly where the ocean is shallow. But the changes in the land are in general much larger than the changes over the ocean. Again this shows that the clouds are forming in response to, and are therefore limiting, increasing warmth.
How the Governor Works
Tropical cumulus production and thunderstorm production are driven by air density. Air density is a function of temperature (affecting density directly) and evaporation (water vapor is lighter than air).
A thunderstorm is both a self-generating and self-sustaining heat engine. The working fluids are moisture-laden warm air and liquid water. Self-generating means that whenever it gets hot enough over the tropical ocean, which is almost every day, at a certain level of temperature and humidity, some of the fluffy cumulus clouds suddenly start changing. The tops of the clouds streak upwards, showing the rising progress of the warm surface air. At altitude, the rising air exits the cloud, replace by more air from below. Suddenly, in place of a placid cloud, there is an active thunderstorm.
“Self-generating” means that thunderstorms arise spontaneously as a function of temperature and evaporation. They are what is called an “emergent” phenomenon, meaning that they emerge from th background when certain conditions are met. In the case of thunderstorms, this generally comes down to the passing of a temperature threshold.
Above the temperature threshold necessary to create the first thunderstorm, the number of thunderstorms rises rapidly. This rapid increase in thunderstorms limits the amount of temperature rise possible.
“Self-sustaining” means that once a thunderstorm gets going, it no longer requires the full initiation temperature necessary to get it started. This is because the self-generated wind at the base, plus dry air falling from above, combine to drive the evaporation rate way up. The thunderstorm is driven by air density. It requires a source of light air. The density of the air is determined by both temperature and moisture content (because curiously, water vapor at molecular weight 16 is only a bit more than half as heavy as air, which has a weight of about 29). So moist air is light air.
Evaporation is not a function of temperature alone. It is governed a complex mix of wind speed, water temperature, and vapor pressure. Evaporation is calculated by what is called a “bulk formula”, which means a formula based on experience rather than theory. One commonly used formula is:
E = VK(es – ea)
where
E = evaporation
V= wind speed (function of temperature difference [∆T])
K = coefficient constant
es = vapor pressure at evaporating surface (function of water temperature in degrees K to the fourth power)
ea = vapor pressure of overlying air (function of relative humidity and air temperature in degrees K to the fourth power)
The critical thing to notice in the formula is that evaporation varies linearly with wind speed. This means that evaporation near a thunderstorm can be an order of magnitude greater than evaporation a short distance away.
In addition to the changes in evaporation, there at least one other mechanism increasing cloud formation as wind increases. This is the wind-driven production of airborne salt crystals. The breaking of wind-driven waves produces these microscopic crystals of salt. The connection to the clouds is that these crystals are the main condensation nuclei for clouds that form over the ocean. The production of additional condensation nuclei, coupled with increased evaporation, leads to larger and faster changes in cloud production with increasing temperature.
Increased wind-driven evaporation means that to get the same air density, the surface temperature can be lower than the temperature required to initiate the thunderstorm. This means that the thunderstorm will still survive and continue cooling the surface to well below the starting temperature.
This ability to drive the temperature lower than the starting point is what distinguishes a governor from a negative feedback. A thunderstorm can do more than just reduce the amount of surface warming. It can actually mechanically cool the surface to below the required initiation temperature. This allows it to actively maintain a fixed temperature in the region surrounding the thunderstorm.
A key feature of this method of control (changing incoming power levels, performing work, and increasing thermal losses to quelch rising temperatures) is that the equilibrium temperature is not governed by changes in the amount of losses or changes in the forcings in the system. The equilibrium temperature is set by the response of wind and water and cloud to increasing temperature, not by the inherent efficiency of or the inputs to the system.
In addition, the equilibrium temperature is not affected much by changes in the strength of the solar irradiation. If the sun gets weaker, evaporation decreases, which decreases clouds, which increases the available sun. This is the likely answer the long-standing question of how the earth’s temperature has stayed stable over geological times, during which time the strength of the sun has increased markedly.
Gradual Equilibrium Variation and Drift
If the Thermostat Hypothesis is correct and the earth does have an actively maintained equilibrium temperature, what causes the slow drifts and other changes in the equilibrium temperature seen in both historical and geological times?
As shown by Bejan, one determinant of running temperature is how efficient the whole global heat engine is in moving the terawatts of energy from the tropics to the poles. On a geological time scale, the location, orientation, and elevation of the continental land masses is obviously a huge determinant in this regard. That’s what makes Antarctica different from the Arctic today. The lack of a land mass in the Arctic means warm water circulates under the ice. In Antarctica, the cold goes to the bone …
In addition, the oceanic geography which shapes the currents carrying warm tropical water to the poles and returning cold water (eventually) to the tropics is also a very large determinant of the running temperature of the global climate heat engine.
In the shorter term, there could be slow changes in the albedo. The albedo is a function of wind speed, evaporation, cloud dynamics, and (to a lesser degree) snow and ice. Evaporation rates are fixed by thermodynamic laws, which leave only wind speed, cloud dynamics, and snow and ice able to affect the equilibrium.
The variation in the equilibrium temperature may, for example, be the result of a change in the worldwide average wind speed. Wind speed is coupled to the ocean through the action of waves, and long-term variations in the coupled ocean-atmospheric momentum occur. These changes in wind speed may vary the equilibrium temperature in a cyclical fashion.
Or it may be related to a general change in color, type, or extent of either the clouds or the snow and ice. The albedo is dependent on the color of the reflecting substance. If reflections are changed for any reason, the equilibrium temperature could be affected. For snow and ice, this could be e.g. increased melting due to black carbon deposition on the surface. For clouds, this could be a color change due to aerosols or dust.
Finally, the equilibrium variations may relate to the sun. The variation in magnetic and charged particle numbers may be large enough to make a difference. There are strong suggestions that cloud cover is influenced by the 22-year solar Hale magnetic cycle, and this 14-year record only covers part of a single Hale cycle. However, I have yet to find any significant evidence of this effect on any surface weather variables, including clouds.
Conclusions and Musings
1. The sun puts out more than enough energy to totally roast the earth. It is kept from doing so by the clouds reflecting about a third of the sun’s energy back to space. As near as we can tell, over billions of years, this system of increasing cloud formation to limit temperature rises has never failed.
2. This reflective shield of clouds forms in the tropics in response to increasing temperature.
3. As tropical temperatures continue to rise, the reflective shield is assisted by the formation of independent heat engines called thunderstorms. These cool the surface in a host of ways, move heat aloft, and convert heat to work.
4. Like cumulus clouds, thunderstorms also form in response to increasing temperature.
5. Because they are temperature driven, as tropical temperatures rise, tropical thunderstorms and cumulus production increase. These combine to regulate and limit the temperature rise. When tropical temperatures are cool, tropical skies clear and the earth rapidly warms. But when the tropics heat up, cumulus and cumulonimbus put a limit on the warming. This system keeps the earth within a fairly narrow band of temperatures (e.g., a change of only 0.7°C over the entire 20th Century).
6. The earth’s temperature regulation system is based on the unchanging physics of wind, water, and cloud.
7. This is a reasonable explanation for how the temperature of the earth has stayed so stable (or more recently, bi-stable as glacial and interglacial) for hundreds of millions of years.
Further Reading
Bejan, A, and Reis, A. H., 2005, Thermodynamic optimization of global circulation and climate, Int. J. Energy Res.; 29:303–316. Available online here.
Richard S. Lindzen, Ming-Dah Chou, and A. Y. Hou, 2001, Does the Earth Have an Adaptive Infrared Iris?, doi: 10.1175/1520-0477(2001)082<0417:DTEHAA>2.3.CO;2, Bulletin of the American Meteorological Society: Vol. 82, No. 3, pp. 417–432. Available online here.
Ou, Hsien-Wang, Possible Bounds on the Earth’s Surface Temperature: From the Perspective of a Conceptual Global-Mean Model, Journal of Climate, Vol. 14, 1 July 2001. Available online here (pdf).
Another good one I referenced above is:
http://ams.allenpress.com/archive/1520-0442/7/4/pdf/i1520-0442-7-4-559.pdf
Fig 5/7 gives high trop cloud amount vs SST (very little cloud if SST is less than 299K
Unfortunately it concludes that the cloud forcing is near zero for the tropics
oms (00:17:30) :
But if you are talking about sea level rise which is severe enough to inundate a sizeable part of Central America, then yes I’m sure you’d find a much different pattern of ocean circulations as well. 🙂
The summit section of the Panama Canal is 26 metres above sea level.
There is a 9500 year old submerged city in the gulf of Bombay which is 36 metres below sea level.
Willis Eschenbach (03:41:47) :
E.M.Smith (23:36:13), you ask:
And what, exactly, is a ‘cloud forcing’? What physical property, documented in a physics text, is a ‘forcing’? In what units is a ‘forcing’ measured?
In climate science, a “forcing” is some kind of energy that enters or is transferred around the climate system. “Solar forcing” for example refers to the energy entering the climate system from the sun. Forcing is measured in Watts per square metre (W/m2). As such, it is an instantaneous measurement.
I was surprised also when for the first time I heard the word “forcing” in Climate Science in the Faculty. Then the teacher explained us why climatologists used the word “forcing” comparing it to “external operator”. The problem is that in physics we understand that a “forcing” factor is nothing less than a man-made mechanism which forces the heat to go anywhere, for example a fan, a coolant liquid in an engine, etc.
Given that the Sun, the clouds, the oceans, the water vapor, etc. are all natural, from the physics standpoint the heat transfer from one system to another performed by any natural operator is not considered a “forcing” process, but a “natural” process.
That’s the origin of the confusion. “Forcing” in climate science is for “external operator” acting onto the system. “Forcing” in physics, biophysics, etc. is for any artificial process, not natural.
Willis wrote :
“As you you say that “this idea is not really new”, I’d be very interested in any references you might have to the idea that the earth’s temperature is regulated by cumulus/cumulonimus being put forwards previously.”
To be more precise .
There are 2 ideas in your “thermostat” proposal .
.
First is to consider the Earth’s system as a dynamical heat machine .
This one is not new as Bejan already worked on it . R.Courtney also provides a reference . There are more .
Bejan with a relatively simple model convincingly showed how the general circulation system will organise itself in order to transfer heat from equator to poles . He was even able to predict the size of the Hadley cell with a surprising accuracy for such a simple model .
This part shows that ANY planetary system equipped with a transfer medium (atmosphere&liquid) will spontanously organise itself to transfer heat from hot to cold with the highest efficiency possible .
A corollary of that “maximum efficiency” principle is that the system will have to regulate the “hot end” which can potentially move much because the “cold end” moves little .
.
Second is new and original . At least to my knowledge nothing has been published along this road .
It is the idea of OVERSHOOTING .
If one admits the idea supported by observation of 4 billions years that the system operates at constant (or very slightly varying) temperature , the overshooting hypothesis becomes almost necessary .
Indeed anybody faimliar with non linear dynamics (and there are several of this kind here) knows that if you have a lagged system and want to regulate it , you MUST overshoot (or undershoot) .
The trick being to get the right timing when to stop overshooting (or undershooting) because else the system won’t stabilize .
If you have a lagged system , reacting proportionally (via feedbacks) on deviations will NEVER stabilise the system , it will make it either oscillate wildly or to blow up .
Now as our Earth system is a lagged system AND it is stable , the natural consequence is that the regulating mechanism must necessarily be overshooting (and undershooting) .
I found it really impressive to see formulated for the first time a real mechanism which seems to do exactly that – overshooting and undershooting .
I freely admit that while I have always been conviced that such a mecahnism must exist and that it will manifest itself on the “hot end” (aka equator) I have never thought about your cumulus/cumulonimbus interactions .
Now to be honest , I also noticed that while you have stated that this mechanism overshoots and undershoots , you have not given the proof that it really does so over longer time periods (more than a season) .
.
2 particular remarks .
– This overshooting/undershooting mechanism would also explain the appearance 2 or more different stable states (f.ex Ice Earth , Desert Earth etc) in the case if the climate was chaotic . Indeed the chaotic bifurcations (analogous to the phase change of a fluid) can happen even with an infinitesimal variation of the control parameter provided that the system finds itself in the right region of the attractor .
– The 19th century physics based on equilibriums and time independent states which is what 90% of the official authorised climate science is doing can neither confirm nor falsify your idea because they simply live in another (non dynamical) world .
More particularly no numerical model based on equilibriums will be able to reproduce your result .
This is of course no problem because computer programs are not reality so one doesn’t need to consider them .
But I bet that there is/will be a large amount of people who would say “Willis is wrong because the computer models don’t say what he’s saying” 🙂
Correction: Bay of Cambay
was unable to copy the thermostat hypothesis. why?
Ron de Han, Indiana Bones:
Re: abundance of resources (specifically Lithium for electric cars). I know this is OT but the subject is so broadly misunderstood that it should be pointed out. Reserves of a material are the measured economically mineable tonnages, not how much there is out there. When there has been only slight demand for a metal, no one is “developing reserves”. Indeed, there are almost innumerable lithium-bearing pegmatite deposits (as well as brines and billions of tons of clays with adsorbed lithium ions. Average abundance in the earth’s crust is 20ppm. Compare that with the battery materials lead- 14ppm and cadmium 110 pp billion. As we speak, lithium reserves are busy doubling and redoubling.
Dave Middleton (05:57:34) :
If the Milankovitch Cycles really are the drivers of the Plio-Pleistocene glacial-interglacial cycles, cloud/albedo negative feedbacks aren’t much of a deterrent to cooling…The Earth simply receives less heating from the Sun. As the Earth “wobbles” into glacial episodes, sea level drops by more than 100 meters…This might release sufficient methane hydrates from the sea floor to actually accelerate the warming process as the Earth “wobbles” its way out of glacial episodes.
The direct forcing from Milankovitch cycles is tiny- a fraction of a W/M2.
But M cycles result in cooler summers in the northern hemisphere, which allows winter snow and ice to last longer into the spring/summer, which increases the earths albedo (a positive feedback), which lowers temperatures, and allows more snow and ice to accumulate…
Nobody has come up with way to get ice ages without strong positive feedbacks. Climate sensitivities calculated by comparing modern conditions to the last glacial maximum (LGM) are the same as determined by climate models (about 3C +/-).
In the calculations using the LGM, clouds did whatever they do (positive or negative feedback). The fact that the LGM calculations yield sensitivities of around 3C shows that if clouds are a negative feedback, that feedback is not strong enough to overcome the other positive feedbacks in the system.
I’m not sure about Milankovitch yielding only a fraction of a w/m-2…But that’s the basic process – At least as far as it’s understood.
By “ice ages”, I’m assuming you mean Plio-Pleistocene glacial episodes (as opposed to the large-scale icehouse periods that occur about every 130 million years.)
The feedback mechanism is probably the ice accumulation in the Northern Hemisphere and its effects on sea level and oceanic circulation.
That’s correct. Clouds aren’t a strong enough mechanism to prevent warming events on the scale of the Holocene or the Medieval Warm Period. However, they certainly can play a role in moderating those type of events. And clouds could play a major role in smaller-scale cycles like the PDO and ENSO.
bill (03:25:37) :
Nasif Nahle (22:06:36) :
The info on Fig. 13 says it clearly:
Figure 13. This figure illustrates that as the sea level record becomes
longer, the relative sea level trend estimates become more stable and reliable. The reason for this is that the trends from short sea level records are affected by the natural sea level variability occurring on inter-annual, El Niño and decadal timescales due to atmospheric, oceanographic and geological processes. (Bolds are mine
What are you saying!!??
Fig 13 shows a time average of rate of sea level rise The average becomes more stable as more readings are taken (the max and min excursions become less significant). The plot shows that the rise is positive. From the table this is 5.5mm/year.
Hahaha… It’s not me who said it, but the authors of the paper. I only copied and pasted the quote… 🙂
Yes you are correct viewing that closed loop system. Energy in must equal energy out. To use your heat pipe analogy, x amount of energy is put into the heat pipe to evaporate water to vapor (warming the ground and sea surface). That vapor moves to the cold end of the heat pipe and condenses releasing exactly the same amount of energy.
The point I was making is the cold end of the thunderstorm heat pipe is a heat sink that must dissipate that heat of condensation to some place. That heat released as latent heat of condensation must either go into the upper atmosphere warming the air near the tropopause, or it must be radiated to space. In either case the quantity of water condensed to liquid is probably a valid proxy for the amount of heat lost to one or the other of those heat sinks.
If satellite measurements do not show significant warming of the air near the cloud tops, then they must be losing that energy to space by radiation (unless I am missing another heat sink). Most likely they are losing the energy to space via both mechanisms one being prompt radiation directly to space as the warm updraft cools by radiation, and physical mixing with cold high altitude air, and delayed radiation to space as this slightly warmed high altitude air re-radiates heat energy to space from the top of the anvil cloud structure.
This then forms the basis for a testable case:
That would allow you to determine how much energy a large thunderstorm dumps to the upper atmosphere by advection and mixing, (which in short order gets radiated to space), and how much gets immediately radiated directly to space in the IR spectrum.
The cooling effect of a thunder storm as I am visualizing it, consists of several components.
1. direct reflection of incoming solar energy from the cloud tops (reducing heat input to the earth system)
2. Heat mechanically carried to high altitude by the updraft in the latent heat of the moisture and released to space via either direct prompt radiation or delayed radiation from the slightly warmer cloud tops. (active cooling of the earth system as warm lower altitude air, is lifted, and physically transported to high altitude. This air which has already absorbed solar energy would be a form of active refrigeration as heat is mechanically moved to high altitude for rapid re-radiation of that heat to space).
My comments were intended to point out a possible test.
If thunder storm cloud tops are only reflecting incident solar energy (simple albedo effects) they cannot be radiating more energy to space than the current solar flux striking them.
If they are actively pumping heat to high altitude, they will be radiating more energy to space than the incident solar energy and their reflectivity would imply. This extra energy is a measure of the active cooling they provide above and beyond their simple change in albedo.
If true, once demonstrated and quantified, the storm total rain fall from the storm should be able to be used to estimate how much energy that storm actively moved to high altitude for radiation to space, as all the heat lost as the humidity condensed must be lost to a heat sink at high altitude. This would provide a relatively simple means to quantify the active heat pumping of a large storm by measuring its total precipitation.
Hope that makes sense?
Larry
Just a thought:
If clouds cause a negative feedback because of albedo changes, that feedback range should be large on a warm planet. Basically the upper limit is reached when the whole sun-exposed hemisphere is covered in clouds. The feedback “gain” is the albedo change between cloud covered and clear surface.
On the cold side the cloud feedback should be limited. Clouds over an ice or snow covered surface would not change albedo appreciably and in that case hardly have an albedo feedback towards warmer condition.
Just looking at it simplistically, the clouds could therefore prevent runaway warming, but can not prevent runaway cooling once a lower temperature threshhold is crossed.
Am I on the right track, or am I falling in Heinleins trap:
“Logic is an organized way to go wrong with confidence” ?
“”” Willis Eschenbach (03:41:47) :
E.M.Smith (23:36:13), you ask:
And what, exactly, is a ‘cloud forcing’? What physical property, documented in a physics text, is a ‘forcing’? In what units is a ‘forcing’ measured?
In climate science, a “forcing” is some kind of energy that enters or is transferred around the climate system. “Solar forcing” for example refers to the energy entering the climate system from the sun. Forcing is measured in Watts per square metre (W/m2). As such, it is an instantaneous measurement.
For example, TOA (top of atmosphere) instantaneous solar forcing perpendicular to the sun is about 1360 W/m2. However, this has to be divided by 4 to average it over the surface of the earth. Thus, incoming solar forcing is usually taken to be 340 W/m2.
“Cloud forcing” comes in two varieties. Clouds reflect about 70 W/m2 of the incoming sun, which is called a negative forcing. They also emit infrared that warms the surface. This is called a positive forcing.
The question at hand regards the “net cloud forcing”. In total on a global average basis, do clouds reflect more sunlight (in W/m2) than the amount of infrared they emit (again in W/m2)? The models say yes. I and others say no. “””
Willis, E.M’s question is an issue that also rankles me; I detest the term “forcing”, and the notions behind it. The solar “forcing” of 1366 W/m^2 is simply the energy input to the earth’s environment, and it isn’t forcing anything; and it is 1366 W/m^2 and not 340; it does not fall on all of the earth’s surface at the same rate at the same time. You yourself ddescribe a forcing as instantaneous.
Well I submit that an instantaneous input of 1366 W/m^2 has a totally different effect on the earth from a 24 hour time average, 4pi.r^2 surface average 340 w/m^2.
After atmospheric losses, the surface insolation is about 1kW/m^2, normal to the sun, and not the 168 +30 W/m^2 that the official NOAA earth energy budget diagram asserts. Those NOAA figures imply a 15% reflection coefficient at the earth’s surface, yet 71% of that surface is ocean, and an even greater fraction of that surface in the tropical zones is ocean, and the reflection coefficient of the oceans for solar radiation is more like 3%, not 15%.
My point is that the whole physics of the interraction between intermittent solar energy incident on earth, is totally different from that which would be elicited by a fictional 168 +30 reflected system that is described by the NOAA budget chart; which I am told originated with Trenberth et al.
The real world numbers drive surface temperatures much higher resulting in much higher infrared radiation fluxes, which have totally different IR spectra via Wien displacement.
Well I’m not going to go on and on, I am sure you already know all this anyway.
As to the effect of cloud “forcings”, you talk about the 70W/m^2 cloud reflectance; NOAA’s chart suggests 77, but here once again this is a fictitious number extracted from the 342 W.m^2 allegedly incoming from the sun. So maybe your 70 number should be 280-308 W/m^2; those clouds can only reflect sunlight during the daylight hours.
You then assert that the IR emission from clouds is greater than the reflected solar energy. How do those clouds come by that large amount of energy; what is the energy generation mechanism inside those clouds.
Well I can think of several; three to be precise. First there is the one time deposition of around 545 calories per gram of Latent heat of condensation, plus possibly another 80 calories per gram of latent heat of freezing, if ice crystals are formed; but that is a one time event to form the cloud in the first place, and ALL of that energy came from the surface of the earth; mostly from the oceans, so it is a vast transfer of energy towards outer space.
Then there is the direct absorption of incoming solar radiation in the spectral range beyond about 750 nm . That solar sourced energy is a loss from the ground level insolation, and it is a very important loss. If that energy which might be as much as 270 W/m^2 out of the sunlight had reached the surface; mainly the oceans, it would have propagated many tens of metres into the oceans, before slowly returning to the surface due to the vertical convection gradient set up by the warming of the ocean water. Instead that energy is absorbed by the cloud, warming the cloud and atmosphere, resulting in a nearly isotropic emission of infrared radiation, and since the cloud region is a lot colder than the ground,a nd colder than the mean earth temperature, then the spectral peak wavelength of that IR is longer than surface emitted IR. On average, only half of that emitted IR from the clouds is going to proceed downward toward the surface, and that half is going to run the gauntlet of an increasing density and temperature atmosphere, and GHG, whose IR absorption bands become increasingly broad at lower altitudes due to collision (pressure) and Doppler (temperature) broadening, all of which inhibits the passage of that ir downwards; while the exact opposite effects enhance the escape of the upward components.
The third source of cloud energy to fuel that IR emission is the upward IR emission from the surface that was heated by the sun.
As to the effect of the downward IR, which you say warms the surface; what fraction of it survives the multiple absorption cascades is mostly going to be absorbed in the top ten microns of the ocean surface and is going to lead to prompt evaporation, which returns that energy back to the upper atmosphere in the form of latent heat of evaportation, and more water vapor to form more clouds (see Wentz et al, SCIENCE for July 7 2007; “How Much More Rain Will Global Warming Bring ?”
I enjoyed your paper immensely Willis; and largely it goes to solidify my conviction that cloud feedback is NEVER positive; clouds ALWAYS cool the surface of this planet (speaking climatically of course; not last night’s weather).
George
It is postulated that
Stephen Wilde (03:28:17) :
Where we seem to disagree is that you do not see ocean emissivity as varying much so, inevitably, logic pushes you to favour the tropical convection scenario. Nor do you yet accept those oceanic variations and the solar variations as the underlying driver of all those changes in the air which you describe.
I still think that the base temperature is set by sun and sea and not by the physics of air and clouds. I think that the physics of air and clouds (more broadly the air circulation systems) modulates the oceanic variations in emissivity just as the physics of the ocean circulations modulates solar variations in energy supply to the oceans.
I have been trying to connect this with my day to day experience. When a high pressure sits on Siberia, we get cold winds in Greece and the temperature falls several degrees. When a low sits over Italy we get winds from the Sahara and can fast get into the 45C in summer. etc. etc. Day do day experience tells me “it is the winds stupid”, mostly changing from west to east .
But I do see the el Nino and la Nina argument, due to the computer age practically day to day, and realize the great heat capacity of the oceans.
In this thermostat picture of Willis the PDO ENSO etc are not there.
The solutions must lie in treating the full complexity dynamically, as Tom Vonk has been saying. One needs to pay more than lip service to the fact that climate is complex and chaotic. Tsonis et all did make an effort to model the chaotic nature of the ocean currents , as was discussed here a while ago. This thermostat function seems to be important and should be incorporated in a bigger framework.
I am a bit confused by all of the comments that suggest that the heat-engine model of atmospheric/oceanic water here expounded is inconsistent with CO2-mediated AGW. The reason why the political emphasis is being placed on CO2 is that we are able to -control- CO2 emissions, whereas we would be hopeless to influence the water cycle directly by drawing down water vapor.
The scientific community has long acknowledged that water is the most important greenhouse gas, and a good understanding of clouds has been big missing piece of the puzzle for some time. This theory of clouds makes everything fall much more neatly into place. In particular, it provides a rather succinct mechanism for the magnification of the heating effect of CO2, which as several commenters before have pointed out, would not alone suffice through its own spectral absorption to cause the amount of warming we have seen. Extra heat trapped by CO2 gets shunted to the poles by the global heat engine. As the poles warm, the global heat engine’s efficiency decreases, causing it to dissipate less heat and us to experience warming at all latitudes.
For a while the cloud umbrella will be able to stave it off as described here. This is entirely consistent with the greater frequency and severity of tropical storms that we have endured in recent years. We will have lost the Arctic ice cap by 2015. If we’re barking up the right tree with this model, then (optimistically speaking) all of that albedo will be made up for in the form of additional tropical storms cooling the earth for the same amount of heat that would have been reflected into space by the ice cap.
(Whether or not that’s a “good thing” is another debate. I doubt, for instance, that the economic benefits of having a navigable Arctic ocean would outweigh the damage caused by the storms, the damage to the agricultural industry caused by warming-associated droughts, etc.)
An extremely valuable contribution to our understanding of our changing climate.
Stephen Wilde (03:28:17), you say:
The emissivity of water is about 0.96. You seem to think that it varies considerably. I don’t understand this. Perhaps you could explain a) what causes the emissivity to vary, and b) what is the size of that variation?
I think that the clouds cap the temperature of the earth in part because I live in the deep tropics (9°S) and I see the process happening every day. The temperature is not governed by “sun and sea”. The temperature falls when the clouds come over, and when the rain comes. It does not fall before that, it is rising. Seems fairly obvious …
Thanks,
w.
Kalirren (12:48:32), you say:
We’re able to “-control-” CO2? Funny, the Kyoto Protocol tried that and failed miserably.
In any case, my Thermostat Hypothesis is not inconsistent with the effects of CO2. It is simply much stronger than the effects of CO2. Perhaps you believe that a change in CO2 levels from 0.03% (three hundredths of a percent) to 0.04% will radically change the earth’s temperature. But the models are only able to predict this by including a non-physical positive feedback. This feedback is said to be larger than the actual change in forcing due to the CO2 itself. I doubt that greatly.
I’m not sure you understand the size of the forces involved. A 2% change in albedo (undetectably small) gives the same effect as CO2 going from its current 380 ppmv to 1520 ppmv. Clearly the cloud umbrella is much more powerful than CO2.
Next, I’d need a citation for the “greater frequency and severity of tropical storms”. While storm frequency and size have increased slightly in the Atlantic, this is not matched in any other ocean.
And if you’d like to make a large-money bet on whether we will have “lost the Arctic ice cap by 2015”, well, I’m your man.
Additionally, for the reasons given in my post to Patricia (03:29:29), snow and ice have only a small effect on the albedo. This is because during the wintertime there is fewer hours of sun, and it is at a low angle to the horizon. What sun there is travels through lots of atmosphere. In addition, it is at an ideal angle for reflection rather than absorption. So atmospheric absorption and both cloud and surface reflectance is high, and surface absorption is low towards the poles, whether or not there is snow on the ground. This greatly reduces the effect of the change in ground albedo due to snow and ice.
Finally, you mention “the damage to the agricultural industry caused by warming-associated droughts”. In general, a warmer world is a wetter world, because of increased evaporation. Let me repeat that in case someone missed it. A warmer world is, ceteris paribus, a wetter world. Droughts historically have been more severe during colder times. If you truly want to spend your time worrying about the effects of a possible temperature increase … that’s not one of them.
Regards,
w.
anna v (12:16:38), thanks for your contribution. You say:
…
The earth is chaotic, as you point out, and it does not run smoothly. The earth releases its energy in the same way, in chunks and gouts. Thunderstorms are an example of this. Another is the inter-seasonal swings in tropical temperature described by Spencer et al, whose reference I don’t have to hand. During these times, the numbers of thunderstorms rise and fall.
On a larger scale, we have things like the El Niño, the Atlantic and the Pacific Oscillations, the Madden-Julian Oscillations, and the like.
I see all of these as examples of how the earth self-organizes to lose heat. Radiation goes up as the fourth power of temperature. This means that if an object spends two days at 30° and two days at 34°, it will lose more energy than if it spends the same four days at the average temperature.
My sense is that all of these are ways that the earth varies the temperature above and below the average, in order to increase the average heat loss … but that is another Hypothesis outside the scope of this one.
Much appreciated,
w.
KLA (11:41:59), thanks for your thoughts, viz:
While your logic is correct, the effect of snow and ice on the albedo is smaller than you would think at first blush. Ice and snow hang out where the sun is weak or absent (think long winter nights and no sun at the poles). As a result, they do not have as large an effect as one might imagine.
Next, the daily shift in the cloud albedo is about 60 W/m2 (see Fig. 2). If you believe the IPCC climate sensitivity (I don’t, but let’s use it), if this shift were permanent that would equate to about 50°C. Even with a more reasonable climate sensitivity that doesn’t contain the bogus positive feedbacks used by the IPCC, it is still 10°-20°C.
So as you can see, the power of the albedo is very large. My sense is that it is actually larger on the cold side. This is because at the equator, the sun is strongest, so a cloud-free day can let in a huge amount of energy in a short time.
w.
“”” Finally, you mention “the damage to the agricultural industry caused by warming-associated droughts”. In general, a warmer world is a wetter world, because of increased evaporation. Let me repeat that in case someone missed it. A warmer world is, ceteris paribus, a wetter world. Droughts historically have been more severe during colder times. If you truly want to spend your time worrying about the effects of a possible temperature increase … that’s not one of them.
Regards,
w. “””
Willis, to me, one of the biggest fallacies perpetrated by the warming alarmist crowd is the silly notion that warmer means dryer; eg drought.
I find the crucial bit of experimental actual real world measured evidence in this regard is the paper by Wentz et al (he’s at RSS) “How Much More Rain Will Global Warming Bring ?” SCIENCE July 7 2007.
The essentials of this paper are from satellite measured data. A 1 deg C increase in mean global suface temperature (global warming) CAUSES a 7% increase in total global evaporation; a 7% increase in total atmospheric water, and a 7% increase in total global precipitation. It isn’t rocket science that total evap = total precip overall, otherwise we would end up with the oceans over our heads.
In contrast Wentz reported that the GCMs (of unknown species) AGREE with the 7% increase in total atmospheric moisture, BUT they claim only a 1-3% increase in total global precipitation (and ergo evaporation. That is a 2.33 to 7:1 discrepancy between what a fictional computer model predicts and what a real world experiment measures.
Yes I can see it now, a 1% increase in evaporation causes a 7% increase in total atmospheric water, nad of course precipitation can’t exceed evaoration for any length of time; what an absurd claim that is.
Now wentz et al didn’t say so; but I did; that a 7% increase in total global precipitation sort of implies (or at least I infer) something like a 7% increase in total global precipitable cloud cover; that comprising either an increase in total cloud area, or an increase in total cloud density and moisture content, or an increase in total cloud persistence time, or some combination of all three of those. In any case, I would infer that there might be a very significant reduxction in ground level insolation as a result of that increase in precipitable cloud cover. And yes I would expect most of that extra cloud to appear in the tropics where most of the ocean water is, and where most of the incoming solar energy arrives; so the negative cooling feedback from that cloud modulation is not insignificant; but it certainly renders the impact of CO2 doubling as quite negligible; the water can do it all without any CO2 assistance.
And water in all three phases is a permanent part of the atmosphere, and has been for the duration of life on earth. So nutz to those who claim that CO2 is a long lived component of the atmosphere, but water vapor isn’t.
This whole surface warming/evaporation/cloud formation/solar flux blockage/precipitation cycle is so 8th grade high school science; and it boggles my mind that there are serious scientists who don’t see that and adhere to the ridiculous CO2 and “climate sensitivity” “forcing” that Arrhenius bequeathed to us.
It is time to tell climatologists that the forcing (W/m^2) due to a CO2 doubling varies by at least a factor of 12:1 depending on where you are on earth, and the local terrain and temperature; so to imply that it is some universal constant that can be applied all over the globe is laughable; and puts “climatology” in the same class as “economics” and “ancient astrology”.
And while they are trying to measure and compute some global mean value for “climate sensitivity” please make sure they conform to the rules of sampled data systems, specifically the Nyquist sampling theorem.
Whatever the “climate sensitivity” value for the San Francsisco Bay area may be, it is certainly not possible to use that value 1200 km away in the middle of the Sea of Cortez; like they do for “temperature anomalies”.
Anyhow, it is well past time to put CO2 and clouds both in their proper places in global climate; which is nowhere for the CO2, and stage front and center for clouds.
George
“”” Willis Eschenbach (13:19:44) :
Stephen Wilde (03:28:17), you say: “”
Willis, it is amazing how easily misunderstood this simple fact is.
Water has a refractive index of 1.333 over the solar spectrum range, so the Fresnel reflection coefficient is about 2% ((n-1)/(n+1))^2 for normal incidence.
also the Brewster angle for water (arctan(n)) is 53 degrees, so the reflection coefficient is almost constant out to that angle of obliquity, and then climbs quickly to 1005 at grazing incidence. The net effect is about 3% of incident solar flux is propagated into the surface of the oceans, and the bulk of that is ultimately absorbed. Consequently the world’s oceans are quite close to black body absorbers for solar radiation, and even moreso for long wave infra red radiation where water is nearly totally opaque.
So as you state the total emissivity of the oceans over the range of wavelengths of interest to weather and climate has to be in the 96-97% range.
Were it not for atmospheric scattering, this planet would be the black planet, rather than the blue planet.
You mention that the oceans have a max temperature limit of 305K; about 32 C or around 89 F. they also have a minimum of about -3 deg C, so the total temperature range of the earth’s oceans is around 35 deg C from extreme to extreme. Contast this with a total global surface range from about +60 deg C (or higher) and -90C, giving a total global range of 150 deg C (all of which could be present on the same day, in northern midsummers, and Antarctic winter midnights.
So the oceans are hardly the global temperature drivers; althought they do play an immense role via the evaporation cloud formation cycle.
Certainly oceanic circulations affect local climates and weathers, but they are not the drivers of temperature extremes.
Willis (13:19:44)
During an El Nino the SSTs in the Pacific become warmer and impart more energy to the air.
During a La Nina the SSTs in the Pacific cool and withhold energy from the air.
Those are the most obvious examples of changing ocean energy emissivity.
There are similar phenomena in other oceans.
The amount of variation in emissivity varies from cycle to cycle.
It seems that during the entire positive phase of 30 years or more the enhanced energy emissivity of the Pacific gradually warms up the temperature of the air and at the same time the air circulation systems migrate poleward.
The opposite happens during a 30 year negative phase.
The scale of the changing energy input to the air dwarfs anything that Tropical convection can achieve hence the need for the air systems to move latitudinally IN ADDITION TO any enhancement of just the Tropical convection process.
If the Tropical convection process were able to deal with such changes in energy transfer values from the oceans over 30/60 year timescales then we simply would not observe those latitudinal shifts in ALL the air circulation systems.
As you seem to agree cloudiness follows warming rather than causing it.
Warmer seas do enhance Tropical convection but cooler seas suppress it.
The driver is the ocean not the air and cloudiness is a response and not a driver.
I do agree that this is where I appear to differ from you, Erl Happ, Bob Tisdale, Svensmark and others who rely on the cloudiness changes as a driver to explain their opinions about how it all works.
We shall just have to see where the data leads us over time.
Best Wishes.
Stephen.
Stephen Wilde (15:42:17) :
I find it hard to clearly separate the driver from the response when both are so intertwined. The behavior of the ocean is pretty clearly related to wind driving (closely linked to convection in the tropics) and differential heating (affected by clouds, for example).
On the other hand, I also find it hard to agree with strong assertions in the other direction, such as
George E. Smith (15:26:51) :
If the ocean heat transport goes one place and not another, are the currents then the anti-drivers of extreme temperature differentials?
George E Smith (15:26:51)
You say:
“So the oceans are hardly the global temperature drivers; althought they do play an immense role via the evaporation cloud formation cycle.
Certainly oceanic circulations affect local climates and weathers, but they are not the drivers of temperature extremes.”
The oceans do and must control the flow of solar energy passing into the air because such a huge amount is stored in the oceans.
Oceanic cycles over 30/60 years or more vary that supply of energy to the air.
Those cycles are not what are ordinarily referred to as currents or circulations. By virtue of the observed fact that Pacific SSTs vary on multidecadal timescales it must be the case that there are other inadequately understood events within the oceans that give rise to such changes.
Those ocean changes do not need to drive temperature extremes. All they do is alter the rate of solar energy transfer from oceans to air.
All else follows from those changes.
The combination of sun and oceans sets the global equilibrium temperature and the air has to adjust to deal with variations in the energy flow from sun to ocean to air to space.
The air does not and never did set the global equilibrium temperature and changes in the air alone cannot change it.
I am aware of the uniqueness of this proposition and that it tramples on ideas not only of warming alarmists but also of those sceptics who, like the alarmists, think that the drivers are all in the air (whether from cloudiness or whatever).
The key observation is the recognised latitudinal shift in the air circulation systems in response to changes in ocean SSTs. That observation is inconsistent both with alarmist theory and any sceptic theory that relies on the air as a driver.
To make that simple observation consistent with such sceptical theories the changes in SSTs would have to FOLLOW the latitudinal shift in the air circulation systems and it would have to be accepted that warmer air warms the oceans DESPITE the efficiency of the evaporative and convective processes.
It would also be necessary to postulate HOW the changes in the air alone might cause those global latitudinal shifts without oceanic involvement.
If you can deal with those inconsistencies I will reconsider.
Willis (14:16:38):
Thank you for your answer.
Just to clarify:
My thoughts were more directed towards why, with cloud feedback, it is still possible to have a “snowball earth”, but not an AGW hell. Increasing snow/ice cover to lower latitudes would constitute an accelerating positive feedback mechanism towards cold, even when cloud cover decreases (likely) or stays the same (unlikely). However, an increase of thermal energy input into the heat engine would cause (I think) a total increase in cloud cover, and therefore would cause a strong negative feedback to dampen increased temperatures, overwhelming positive “forcings”.
While cloud feedback works mainly on diurnal cycles, the ice/snow feedback would work much slower though.
BTW, I have not seen mentioned anywhere in the climate discussion the Anasazi people, which lived in the American southwest around the time of the medieval warm period. I understand the archaelogical “consensus” is that they dissapeared from there because of increasing drought. And they disappeared just about at the end of that medieval warm period.
Coincidence?