La hipótesis termostato. Una explicacion del clima, pasando del CO2.

Una explicación brillante y clara del sistema climático, sin miedos ni apocalipsis. Y sin gimnasia estadística. Viene de WattsUpWithThat, propuesta por Willis Eschenbach.

The Thermostat Hypothesis

Resumen La Hipótesis Termostato consiste en que las nubes y las tormentas del trópico regulan  activamente la temperatura de la tierra. Eso mantiene la tierra alrededor de una temperatura de equilibrio.

Se presentan varios tipos de pruebas para establecer y explicar la Hipótesis Termostato - la estabilidad térmica histórica de la tierra, consideraciones teóricas, fotos de satélites y una descripción del mecanismo de equiibrio.

Estabilidad histórica La estabilidad de la temperatura de la tierra en el tiempo ha sido un largo puzzle climatológico. El globo ha mantenido una temperatura de ± ~ 3% (incluyendo las galiaciones) durante por lo menos los 500 milones de años durante los que es posible estimar la temperatura. Durante el Holoceno las temperaturas no han variado mas del ±1%. y durante las glaciaciones, la temperatura era en general igualmente estable.

En contraste con la estabiliad de la temperatura de la tierra, la física solar muestra hace tiempo  (Gough, 1981; Bahcall et al., 2001) que 4.000 millones de años atrás la rradiación total solar era unas tres cuartas partes de los valores actuales. En los primeros tiempos geológicos la tiera no era correspondientemente más fría. Los “proxies” de temperatura, como los ratios de deuterio / hidrógeno y los ratios de O16 / O18 no muestran signo de un 30% de calentamiento de la tierra en ese período. ¿por qué no se calentó la tierra según se calentaba el sol?

A esto se le llama la “paradoja del débil sol primitivo” This is called the “Faint Early Sun Paradox” [–>] (Sagan y Mullen, 1972), y se suele explicar suponiendo una atmósfera primitiva mucho más rica en gases invernadero.

Sin embargo esto implicaría un descenso gradual en el forzamiento de los gases invernadero que se correspondiera exactamente con el incremento en el forzamiento solar durante miles de milones de años hasta su valor actual. Parece sumamente improbable.

Un candidato mucho más probable es algún mecanismo naturalque haya reguado la temperatura de la tierra durante el tiempo geológico.

Consideraciones teóricas. Bejan (Bejan 2005) ha mostrado que el clima se puede modelar muy bien como un motor térmico, siendo el océano y la atmósfera los fluidos de trabajo. Los trópicos son la parte caliente del motor. parte de ese calor se radia de vuelta al espacio.El trabajo se lleva a cabo por los fluidos en el transporte del resto de ese calor desde los trópicos a los polos. Allí, en la parte fría del motor, el calor se radia al espacio. bejan mostró que la existencia y la cobertura espacial de las células de Hadley [–>] es un resultado derivable de la Teoría Constructaj [–>] . También mostró como se determinan las temperaturas de sistema de flujo.

“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

donde q es el flujo total de energía del sistema (de trópicos a polos) y TH y TL son las temperaturas alta y baja (temperatura tropical y temperaura polar en grados Kelvin). El sistema trabaja incesanetemente para maximizar la fuerza resultante. Aquí hay una vista completa del sistema que transporta el calor de los trópicos a los polos.

Figura 1. La tierra como un motor térmico.Las células ecuatoriales de Hadley proporcionan la fuerza del sistema. Sobre los trópicos, el sol (flechas naranjas) es más fuerte porque llegan a la tierra más perpendicuares. la longitud de las flechas naranja representa la fuerza relativa. Aire caliente desciende hacia los 30N y 30S formando los cinturones desérticos que rodean el globo.El calor es transportado a los polos por una combinación de la atmósfera y los océanos. En los polos, el calor es radiado al espacio.

En otras palabra los sistemas de flujo como el del clima de la tierra no asumen una temperatura estable “por narices”. Ahorman su propio flujo de modo que maximizan la energía consumida y producida. Es un proceso dinámico, y no una transformación lineal simple de los detalles de la composición de gases de la atmósfera que estableciera el rango de temeratura de trabajo del planeta.

Observa que la Teoría Constructal predice que cualquier sistema de flujo se “cuasi estabilizará” en órbita alrededor (pero nunca justo) algún estado ideal.En el caso del clima, es el estado de máxima producción de fuerza y cosumo. Y esto a su vez implica que cualquier planeta acuoso tendrá una temperatura de equilibrio mantenida activamente por el sistema de flujo.ver el artículo de Ou listado más abajo para mayor información del proceso.

El mecanismo de gobierno del clima Todo motor de calor tiene un acelerador. El acelerador es la pieza que controla cuante energía enra en el motor. una moto tiene un acelerador de mano. En el automovil se llama pedal de gas. Controla la energía que entra.

La estabilidad de la temperatura de la tierra en el tiempo (incluyendo los períodos bi-estables de glaciaciones ( interglaciares), así como las cosideraciones teóricas, indican que este motor térmico que llamamos clima tiene que tener algún tipo de mecanismo conrolando el acelerador.

Así como todas las máquinas de calor tienen acelerador, no todas tienen un mecanismo gobierno. En un coche el mecanismo de gobierno se llama “Control de Crucero”. Controla con el acelerador la energía que va al coche manteniendo constante la velocidad, a pesar de los forzamientos externos (cuestas, viento eficacia mecánica y pérdidas).

Podemos reducir los candidatos para este mecanismo de gobierno observando primero que el mecanismo controla el acelerador (que a su vez controla la energía suministrada al sistema). Y segundo, vemos que un mecanismo de control exitoso tiene que ser capaz de llevar el sistema más allá del resultado deseado (recalentarlo).

(Nota que un mecanismo de gobierno que contiene una histéresis [–>] es distinto de una realimentación negativa. Una realimetación negativa solo puede reducir un incremento. No puede mantener un estado estable contra forzamientos diferentes, cargas variables y pérdidas cambiantes. Solo un mecanismo de gobierno puede hacer eso.)

La mayor parte del calor que la tierra absorve del sol tien lugar en los trópicos. los trópicos, como el resto del mundo, son principalmente océano. Y la tierra que hay allí está húmeda.ocean; and what land is there is wet. Los trópicos sauna, en una palabra. Tienen poco hielo, así que las nubes controlan cuanta energía entra en la máquina de calor.

Propongo que dos mecanismos interrelacionados pero separados regulan la temperatura de la tierra - los cúmulos y los cumulo-nimbos tropicales. los cúnulos son las suaves nubes  “bolas de algodón” que abundan cerca de la superficie en las tardes calientes. Los cumulo-nimbos son las nubes de tormentas que empiezean como cumulos. los dos tipod de nubes forman parte del mecanismo de control, reduciendo la energía de entrada.Además los cumulo-nimbos son máquinas de calor activas que proporcionan la aceleración para actuar como mecanismo de gobierno del sistema.

Un agradable experimento mental muestra como funciona este mecanismo de control. Se llama “un día en los trópicos”.

Vivo en el profundo y húmedo trópico, a 9ºS, con vistas al Océano Pacífico. Así es como transcurre un día típico. De hecho, es un día típico de verano en cuaquier parte del trópico. El parte meteorológico dice:

Clear and calm at dawn. Light morning winds, clouding up towards noon. In the afternoon, increasing clouds and wind with a chance of showers and thundershowers as the storms develop. Clearing around or after sunset, with an occasional thunderstorm after dark. Progressive clearing until dawn.

– Este es el ciclo diario más normal del clima tropical. Tan normal coma para ser un cliché en todo el mundo.

Está producido por las variaciones noche / día en la fuerza de la energía del sol. Antes del amanecer, la atmósfera está típicamente calma y clara. Según el mar se calienta (o la tierra húmeda), aumentan la temperatura y la evaporación. El aire cálido y húmedo empiezan a ascender. Pronte este aire ascendente se enfría y condensa en nubes. las nubes reflejan la luz del sol. este es el primer paso de la regulación climática.El aumento de temeratura produce nubosidad. las nubes cierran un poco el acelerador, reduciendo la energía que entra en el sistema. Empiezan a enfriar la cosa.Esta es la parte de retroalimentación negativa del conrol climático.

El sol tropical es fuerte, y a pesar de la retroalimentación negativa de los cúmulos, el día se sigue calentando. Cuanto más calor solar llega al océano, más aire húmedo y caliente dse forma, y más cúnulos apareen.Esto, por supuesto, refleja más luz solar, el acelerador se cierra un poco más. Pero el día se sigue calentando.

El desarrollo completo de cúmulos establece el paso para la segunda parte de la regulación de temperatura. Esto ya no es simple retroalimentación negativa. Es el mecanismo de gobierno del sistema climático. Según la temperatura sigue aumentando, según la evaporación escala, algunos de los cúmulos algodonosos se transforman. Rápidamente crecen hacia el cielo, creando en poco tiempo una pila de nubes de miles de metros de altura. Los cúmulos se tranforman en cumulo-nombos o nubes de tormenta. El cuerpo columnar de una tormenta actúa como una gran manguera vertical de calor. La tormenta chuoa aire caliente y húmedo de la superficie y los dispara hacia el cielo. Hacia alturas donde el aire se condensa, transformando el calor latente en calor sensible. El aire se recalienta por esta suelta de calor sensible, y continúa ascendiuendo.

Arriba, el aire es soltado por encima, mucho más alto que la mayor parte del CO2. En esa atmósfera enrarecida el aire es mucho más libre de radiar al espacio.Al moverse dentro de esta manguera de calor de la tormenta el aire se salta la mayor parte de los gases invernadero y sale cerca del final de la troposfera. Durante el transporte, no hay interacción radiativa ni turbulenta entre el aire ascendente y la baja y media troposfera. Dentro de la tormenta, el aire ascendente pasa como por un tunel a través de la mayor parte de la troposfera, para emerger en lo más alto.

Además de reflejar la lus del sol desde su superficie superior como hacen los cúnulos, y de transportar el calor a la troposfera superior donde radia facilemnte al espacio. las tormentas enfrían la superficie en una variedad de otras maneras, epsecialmente sobre el océano..

1. Enfriamiento porevaporación producido por el viento. Una vez que la tormenta empieza, produce su propio viento alrededor de la base. Este viento auto-generado incrementa la evaporación de varias formas, especialmente sobre el océano.

a) La evaporación aumenta linealmente con la velocidad del viento. A la típica velocidad del viento de un chubasco (20 nudos, 35 km/h), la evaporación es unas diez veces mayor que en condiciones de calma.

b) El viento incrementa la evaporación creando aerosol marino (spray). Esto aumenta mucho la superficie de evaporación, porque la superficie total de los millones de gotitas están evaporando igual que la superficie misma.

c) En un grado menor, la superficie de evaporación también aumenta con las olas creadas por el viento, porque una superficie ondulada tiene mayor área evaporativa que una plana.

d) Las olas creadas por el viento aumentan mucho la turbulencia en la capa límite. Esto incrementa la evaporación mezclando aire seco descendente con aire húmedo ascendente.

e) Según el spary se calienta a la temperatura del aire, que en los trópicos suele ser mayor que la del mar, la evaporación también sube por encima del nivel de la suerficie del mar

–. 2. El albedo aumenta por el viento. El spray blanco, los rociones, los borregos de las olas, y los ángulos cambiantes de incidencia, aumentan mucho el albedo de la superficie del mar. Esto reduce la energía absorvido por el océano.

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. 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.

4. Increased reflective area. White fluffy cumulus clouds are not 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 shade 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 (Linden 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 generally die out and vanish as the night cools, 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. In part because they utilize such a wide range of cooling mechanisms 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 night time. And it’s always summer under the sun.

If we accept the convenience that 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 tropics would have more cloud than the left hand side), I though “Hey, that’s a testable proposition to support or demolish my hypothesis”. So in order to investigate whether this postulated increase in cloud on the right hand side of the earth 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. Red line on graph is solar forcing anomaly (in watts per square meter) in the area outlined in yellow. Black line is 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 less 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, the clouds form, and those areas now have high albedo. By contrast, the north now has 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 the 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 catch fire. The tops of the clouds streak upwards, showing the rising progress of the moisture laden surface air. At altitude, the rising air exits the cloud, replace by more moist air from below. Suddenly, in place of a placid cloud, there is an active thunderstorm.

Self-generating means that the thunderstorms arise spontaneously as a function of temperature and evaporation. Above the 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, drive the evaporation rate way up. The thunderstorm is driven by air density. It requires a source of light, moist 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).

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.

So increased wind-driven evaporation means that for the same density of air, 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 timese?

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.

On a 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. 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, this system of 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.

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 at http://homepage.mac.com/williseschenbach/.Public/Constructal_Climate.pdf

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 at http://ams.allenpress.com/pdfserv/10.1175%2F1520-0477(2001)082%3C0417:DTEHAA%3E2.3.CO%3B2

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 at http://ams.allenpress.com/archive/1520-0442/14/13/pdf/i1520-0442-14-13-2976.pdf

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