Fire From Heaven: Climate Science And The Element Of Life--Part Two, The Cloud By Night

Sunlight, the ‘fire from heaven,’ is source of almost all life on Earth—or at least, the energy it relies upon. In Part One of “Fire From Heaven,” we saw how scientists sought to measure that fire, and how succeeding generations attained better and better values for what was long termed the ‘solar constant’—roughly, the amount of energy per square meter reaching the top of Earth’s atmosphere.

Later they instead examined ‘TSI’—‘Total Solar Irradiance.’ This term was introduced in recognition of the small but not necessarily insignificant variations that occur in solar output. The ‘solar constant’ isn’t constant—not quite.

PMOD reconstruction of solar radiation--'Total Solar Irradiation,' or TSI.
PMOD reconstruction of solar radiation--'Total Solar Irradiation,' or TSI.

We also noted that French physicist Claude Pouillet, who in the 1830s made the best early estimate of the solar constant, also measured energy flows by night. He found that even then, with the sun screened by the bulk of the Earth, energy flows to the Earth from the sky.

This downward flow takes place, not in the shorter wavelengths that characterize visible light, but in the longer ones that we call ‘infrared radiation,’ and that used to be termed 'radiant heat.' This ‘flux’ has come to be termed DLR (for "downwelling longwave radiation"), or sometimes DLW—the “L-W” meaning "Long-Wave."

A thermopile by Claude Pouillet.  Image courtesy CNAM, Paris.
A thermopile by Claude Pouillet. Image courtesy CNAM, Paris.

But though Pouillet was the first to examine DLR in the large context of Earth’s heat budget, he was not the first to make experimental measurements of radiation at night. Nor was he first to draw shrewd analytic conclusion, nor to publish his results. Those honors go to a medical doctor and amateur scientist, William Charles Wells (May 24, 1757-September 17, 1817.)

The Charleston, S.C., of Wells' childhood.  Image courtesy Wikimedia Commons.
The Charleston, S.C., of Wells' childhood. Image courtesy Wikimedia Commons.

Wells was born in Charleston, South Carolina, but lived most of his life in England, where he made a modest living as a physician and devoted much of his time to scientific investigation. As one might expect, most of his scientific papers related to medicine--but his most famous study was quite different. As a younger contemporary wrote:

He began an inquiry into the nature of dew, and published ' An Essay on Dew' in 1814. He demonstrated, after a series of well arranged observations made in the garden in Surrey of his friend James Dunsmure, that dew is the result of a preceding cold in the substances on which it appears, and that the cold which produces dew is itself produced by the radiation of heat from those bodies upon which dew is deposited. For this, the first exact explanation of the phenomena of dew, he was awarded the Rumford medal of the Royal Society.

Rumford Medal.  The Royal Society has awarded it biennially since the first years of the 19th century; winners have included some of the most famous names in science.  Image courtesy Royal Society.
Rumford Medal. The Royal Society has awarded it biennially since the first years of the 19th century; winners have included some of the most famous names in science. Image courtesy Royal Society.

Reading his Essay reveals Wells to have been a careful observer, a resourceful experimenter, and an analyst who reasoned closely and paid attention to detail. (“An Essay Upon Dew” is available free via Google Books.)

It must be remembered that in Wells’ day, dew was variously thought to rise from the Earth, or to literally fall from the skies, like mist. It was even believed to cause putrefaction, to produce cold, or to be a threat to health. These beliefs go back to antiquity—Wells cites Aristotle several times, for instance. In this context it’s remarkable how essentially modern Wells’ thought was--despite his eighteenth-century writing style.

Dew on grass.  Image courtesy Taro Taylor and Wikimedia Commons.
Dew on grass. Image courtesy Taro Taylor and Wikimedia Commons.

Wells did his work with relatively modest technological means—basically, a selection of thermometers and a few additional ‘props’—mostly either coverings or supports for the thermometers.

(Although it's worth remembering in this context that affordable, reliable measurement of temperature was a relatively recent phenomenon in his day—Fahrenheit’s scale, the first widely-accepted system to feature fixed reference points, dates to 1724. Prior to that, thermometers essentially measured only relative temperature. Wells' collection of thermometers was not so typical of his day.)

An antique thermometer, marked in the "Reaumur" scale used by Pouillet in the 1830s.
An antique thermometer, marked in the "Reaumur" scale used by Pouillet in the 1830s.

Wells measured nighttime temperatures in various places and under various physical positions, and observed the temperature changes relative to the appearance of dew and to meteorological conditions. He found that clear nights were especially favorable to the production of dew, and that on those nights temperatures tended to be lower at the surface of the garden’s grass than either at the ground or in the air.

Particularly interesting for our purposes were observed changes in sky conditions:

. . .I have frequently seen, during nights that were generally clear, a thermometer lying on the grassplat rise several degrees, upon the zenith being occupied only a few minutes by a cloud. On the other hand, upon two nights I observed a very great degree of cold to occur on the ground, in addition to that of the atmosphere, during short intervals of clearness of sky, between very cloudy states of it.

Moon, clouds and treetops.  Image courtesy Ordale and Wikimedia Commons.
Moon, clouds and treetops. Image courtesy Ordale and Wikimedia Commons.

It’s a startling observation for many, even today—it may seem strange that clouds affect night-time ground temperatures, when there is no sunlight to be blocked by cloud shadows. It may even seem as if this involves some kind of spooky ‘action at a distance.’

But Wells was not puzzled. He realized that there were two factors at work. Firstly, the ground radiates energy to the sky:

. . . bodies situated on or near to the surface of the earth become, under certain circumstances, colder than the neighbouring air, by radiating more heat to the heavens than they receive in every way. . .

Secondly, the sky radiates—or at least, the clouds in the sky radiate—energy back to earth:

Dense clouds near the earth must possess the same heat as the lower atmosphere, and will therefore send to the earth, as much, or nearly as much heat as they receive from it by radiation.

Moreover, this radiation from sky to earth is variable—clouds radiate more than clear sky, and different clouds radiate differently:

. . . similarly dense clouds, if very high, though they equally intercept the communication of the earth with the sky, yet being, from their elevated situation, colder than the earth, will radiate to it less heat than they receive from it, and may, consequently, admit of bodies on its surface becoming several degrees colder than the air. In the first part of the Essay an example was given of a body on the ground becoming at night 5º colder than the air, though the whole sky was thickly covered with clouds.

A thermograph of a cloud (image on right), from the Mallama et al IR cloud detector makes visible the sense of Wells' observations.  Image courtesy of Mallama et Al and NASA.
A thermograph of a cloud (image on right), from the Mallama et al IR cloud detector makes visible the sense of Wells' observations. Image courtesy of Mallama et Al and NASA.

(Wells was quite aware of what we now call the lapse rate—the decline of temperature with increasing altitude; observers such as Horace De Saussure, whom we met in Part One, had written about this. Wells also knew about inversions, in which warmer air overlies colder air; for example, he discusses measurements of inversions made by scientifically-inclined balloonists.)

Chart of atmospheric temperatures.  When temperature decreases with height the 'lapse rate' is positive; when (as in the stratosphere) the reverse occurs it is negative.  Note the steep atmosphere in the lowest layer, the 'troposhpere.'
Chart of atmospheric temperatures. When temperature decreases with height the 'lapse rate' is positive; when (as in the stratosphere) the reverse occurs it is negative. Note the steep atmosphere in the lowest layer, the 'troposhpere.'

Wells’ observations, then, disclose two opposing radiative fluxes. At night the earth radiates to the sky; this flux came to be termed ‘nocturnal radiation’--though as Wells himself noted it is not strictly nocturnal:

Radiation of heat by the earth to the heavens must exist at all times; but, if the sun be at some height above the horizon, the degree of which is hitherto undetermined, and probably varies according to the season, and several other circumstances, the heat emitted by it to the earth will overbalance, even in places shaded from its direct beams, that which the earth radiates upwards.

There is also an opposing flux from sky to earth—later termed ‘sky radiation.’ Like its counterpart, sky radiation occurs around the clock. But when (as would remain the case for decades) the instruments available to study it were limited to variations on the alcohol thermometer, measuring daytime fluxes other than the overwhelming direct solar ‘fire from heaven’ was not very practical.

Rumford medal, reverse.  The inscriptions translates roughly as "Judged best in the study of the nature of radiant heat by the Royal Society, London."
Rumford medal, reverse. The inscriptions translates roughly as "Judged best in the study of the nature of radiant heat by the Royal Society, London."

Though the Rumford Medal gave Wells’ work a forceful endorsement, his ideas also attracted opposition from some—even, at times, opposition with a political agenda. A nineteenth-century English commentator, writing of the eminent Italian physicist Macedonio Melloni (1801-1853), explains some of this context:

[In Naples], in the autumn of 1846, he conducted his researches on the nocturnal cooling of bodies. His memoirs on this subject were read before the Royal Academy of Naples, in February and March, 1847. Mr. Tomlinson, in giving an account of these experiments, says: "The most curious point connected with this inquiry is its origin. It will hardly be believed that the Austrian and Bourbon governments, in their dread of novelty, would not allow the true theory of dew to be taught. Melloni, in order to show that the laws of terrestrial radiation are the same in Italy as in countries where there is more political liberty, undertook these researches.”

Macedonia Melloni.  Image courtesy Wikimedia Commons.
Macedonia Melloni. Image courtesy Wikimedia Commons.

Of course, “the true theory of dew” refers to the work of Wells.

Melloni’s confirmation of Wells was carried out with instrumentation similar to the original study, but he had previously pioneered another approach:

He had already assisted his friend and countryman, Nobili, in perfecting the idea of a highly sensitive thermometric instrument, based on the thermo-electric pile, and recording its indications by means of a galvanometer. By means of this instrument and his own marvellous experimental skill, it was proved that rays of heat present phenomena as complex as those of light.

Melloni died of typhoid at a comparatively young age, with important work still undone. Nevertheless, his work on heat had already earned him a Rumford medal, and the nickname “the Newton of heat.”

Samuel Langley, in full academic regalia.  Image courtesy Wikipedia.
Samuel Langley, in full academic regalia. Image courtesy Wikipedia.

This use of electric technology anticipates research themes of Samuel Langley, whose quest for the ‘solar constant’ was outlined in Part One. (Langley, like Wells and Melloni--and for that matter, like John Tyndall, who famously first discovered specific greenhouse gases--would in due course receive a Rumford Medal of his own.)

In particular, Langley’s electric instrument, the bolometer, vastly increased the sensitivity with which radiation could be observed. Both Langley and his disciple Charles Greeley Abbott focused primarily upon the ‘fire by day,’ not the ‘cloud by night.’ But Abbott, like Langley, was nothing if not systematic, and in 1912 and 1913 collaborated with physicist Anders Knut Angstrom to study nocturnal radiation. This collaboration would result in a lengthy 1918 paper by Angstrom, “A Study Of The Radiation Of The Atmosphere.”

Angstrom and his Assistant, Dr. Kennard, Mt. Whitney, 1913.
Angstrom and his Assistant, Dr. Kennard, Mt. Whitney, 1913.

Angstrom--not to be confused with his more famous grandfather, Anders J. Angstrom, the physicist after whom the "Angstrom" is named--had developed an electric instrument of his own, conceptually a type of actinometer which he usually termed a ‘pyrgeometer.’ (This term has come to be standard for modern instruments intended to measure DLR.)

Citing Wells, Melloni and Pouillet as pioneers, Angstrom credited the Swiss researcher Maurer as being the first to attempt measurement of nocturnal radiation in 1886. (Presumably this means direct measurement, as opposed to less-direct thermometric studies.) Angstrom also noted related work by Perntner (1888), Homen (1897), Exner (1903), K. Angstrom (1903) and Lo Surdo (1908.)

Charles Greeley Abbott in front of the shelter he and Angstrom used during the 1912 expedition in Bassouj, Algeria.
Charles Greeley Abbott in front of the shelter he and Angstrom used during the 1912 expedition in Bassouj, Algeria.

Abbott and Angstrom undertook two campaigns of observation: a preliminary season in Algeria (1912) and a more extensive one at Mount Whitney in 1913.

Both featured synchronous observations at different altitudes, including in the latter case an extension by means of automated instruments flown by balloon to 1500 meters—the balloon flights were made both from the Lone Pine site at the foot of the mountain and from the summit.

America's first balloonsonde flight, 1904.  Image courtesy NOAA.
America's first balloonsonde flight, 1904. Image courtesy NOAA.

Angstrom presents eleven “principal conclusions.” They are too lengthy to quote in full here, but interested readers can find the paper online via Google Books.

In general, the conclusions deal with the influence of temperature and humidity upon what Angstrom terms “effective radiation.” This term is introduced to replace “nocturnal radiation,” since, as noted above, it occurs during the day, too:

VIII. There are indications that the radiation during the daytime is subject to the same laws that hold for the radiation during the night-time.

Less equivocally, Angstrom roughly quantified the effect of cloud altitude Wells had noted:

X. The effect of clouds is very variable. Low and dense cloud banks cut down the outgoing effective radiation of a blackened surface to about 0.015 calorie per cm.1 per minute; in the case of high and thin clouds the radiation is reduced by only 10 to 20 per cent.

A conclusion of great moment:

IX. An increase in altitude causes a decrease or an increase in the value of the effective radiation of a blackened body toward the sky, dependent upon the value of the temperature gradient and of the humidity gradient of the atmosphere. At about 3,000 meters altitude of the radiating body the effective radiation generally has a maximum. An increase of the humidity or a decrease of the temperature gradient of the atmosphere tends to shift this maximum to higher altitudes.

This very nearly amounts to a statement of today’s consensus view of the essential mechanism of the greenhouse effect: that greenhouse gases (specifically water vapor, in Angstrom’s conclusion) shift the effective radiating altitude higher as their concentrations increase.

The unstated corollary is that since higher altitudes are generally colder—the concept of the ‘lapse rate’ noted above—radiative intensity is thereby decreased.

A graph relating altitude (vertical axis), radiation frequency (horizontal axis) and temperature (color code.)  Image courtesy ESPERE.
A graph relating altitude (vertical axis), radiation frequency (horizontal axis) and temperature (color code.) Image courtesy ESPERE.

Angstrom develops this idea further later on in the paper:

These considerations have given a value of the radiation from a perfectly dry atmosphere, and at the same time they lead to an approximate estimate of the radiation of the upper atmosphere, which is probably chiefly due to carbon dioxide and a variable amount of ozone. The observations indicate a relatively high value for the radiation of the upper layers—almost 50 per cent of the radiation of a black body at the prevailing temperature of the place of observation. Hence the importance of the upper atmosphere for the heat economy of the earth is obvious. . .

I think it very probable that relatively small changes in the amount of carbon dioxide or ozone in the atmosphere, may have considerable effect on the temperature conditions of the earth. This hypothesis was first advanced by Arrhenius, that the glacial period may have been produced by a temporary decrease in the amount of carbon dioxide in the air. Even if this hypothesis was at first founded upon assumptions for the absorption of carbon dioxide which are not strictly correct, it is still an open question whether an examination of the "protecting" influence of the higher atmospheric layers upon lower ones may not show that a decrease of the carbon dioxide will have important consequences, owing to the resulting decrease in the radiation of the upper layers and the increased temperature gradient at the earth's surface. The problem is identical with that of finding the position of the effective layer in regard to the earth's radiation out to space.

Knut Angstrom as a young man.  Image courtesy University of Frankfurt.
Knut Angstrom as a young man. Image courtesy University of Frankfurt.

It’s an interesting passage for the son of Knut Angstrom to write—the elder Angstrom had strenuously argued against Arrhenius’ ideas. Also interesting is the fact that certain modern writers claim that Arrhenius was ‘falsified’ by contemporaries, but fail to note either Anders Angstrom’s data or his conclusions regarding carbon dioxide in the atmosphere.

Another aspect of this paper foreshadows later developments. Anders Angstrom was a physicist, like most of the researchers we have mentioned, from Greeley back to Pouillet.

But in 1904 another physicist, the Norwegian Vilhelm Bjerknes, had put forth the idea that his “primitive equations”—a set of differential equations providing for a reasonable mathematical description atmospheric flow—could provide the foundation for numerically-based weather prediction methods that could potentially be much more accurate than existing methods.

Increasingly, sophisticated study of the atmosphere would acquire a practical side, as the still-young but aspiring field of meteorology incorporated the mathematical tools provided by physics.

Vilhelm Bjerknes.
Vilhelm Bjerknes.

Angstrom wrote:

As has been emphasized on several occasions, our observations indicate that the atmospheric radiation in the lower layers of the atmosphere is dependent chiefly on two variables: temperature and humidity. Hence it is obvious that if we know the temperature and the integral humidity as functions of the altitude, we can calculate the radiation of the atmosphere at different altitudes, provided that the relation between radiation, temperature, and humidity is also known. It has been the object of my previous investigations to find this relation; hence, if the temperature and humidity at the earth's surface are known, together with the temperature gradient and the humidity gradient, I can from these data calculate the radiation at different altitudes.

It's not clear whether Angstrom saw such calculations as a practical matter when he wrote these words, but the practical applications would become increasingly prominent over the ensuing years.

A 5-day pressure forecast, made by numerical forecasting methods.  Image courtesy NOAA and Wikipedia.
A 5-day pressure forecast, made by numerical forecasting methods. Image courtesy NOAA and Wikipedia.

Turning toward the meteorological side of atmospheric studies, we may consider the career of William Henry Dines (August 5, 1855-December 26, 1926.) Contemporaries called him a “giant,” and in many ways he exemplifies the development of meteorology in the first decades of the twentieth century, although in others he was a 'Victorian gentleman.'

W.H. Dines, preparing to make a kite observation.
W.H. Dines, preparing to make a kite observation.

Trained as a mathematician—he attained the coveted title of ‘wrangler’ at Cambridge, from whence he received a B.A in 1881—Dines was the son of a prosperous builder who was also a Fellow of the Royal Meteorological Society.

As talented in practical matters as mathematical ones, the younger Dines invented and built numerous meteorological instruments, and mounted several notable observational campaigns, including efforts to make systematic observations at high altitudes broadly similar to the Mt. Whitney campaign of 1913. For the last, Dines designed light and inexpensive autorecording instruments which could be lofted by kite or balloon, organized the observations, and analyzed the data.

Clare Bridge, Cambridge; the view would have been familiar to Dines.  Image courtesy Wikimedia Commons.
Clare Bridge, Cambridge; the view would have been familiar to Dines. Image courtesy Wikimedia Commons.

From the 1920s on his attention turned toward the study of radiation in the atmosphere. He devised yet another instrument, the "ether differential radiometer." ('Ether' refers to the chemical formerly used as an anesthetic, not to the purported pre-Einsteinian medium for electromagnetic radiation.)

A 1920 paper described it thus:

It consists essentially of a sensitive differential thermometer, upon the bulbs of which radiation from any part of the sky, or radiation from a full radiator at a given temperature, can be directed. . .

The differential thermometer is formed of two ordinary glass test tubes each containing a few drops of ether. The tubes communicate with each other by a “U” tube of about 0.7 mm. bore containing ether to form a pressure gauge. As the change of vapour pressure of ether is large for small changes of temperature the thermometer is very sensitive to small changes in the radiation falling on either bulb. It suffices to build up the thermometer with rubber stoppers to the test tubes. A completely sealed-up pair of bulbs nearly exhausted of air would no doubt be better, but would be very fragile and liable to break; but the rubber stoppers answer quite well and the ether will serve for months without renewing.

The pragmatic, practical Dines is very much in evidence here!

Working with his son, L.H.G. Dines, he used his radiometer to make a study of sky radiation at his home in Benson, Oxfordshire—often referred to as “the Benson observatory.” The younger Dines describes the result thus:

The paper consists chiefly of four tables of monthly mean values of radiation from the sky observed at Benson, Oxfordshire, during the five years 1922-1926. The radiation is dealt with under two heads (1) Luminous rays, (2) Dark heat rays of wavelength exceeding about 2 micrometers. Each is measured under conditions of (1) Clear skies, (2) Completely overcast skies. The conditions under which the observations were made are stated and a few of the more salient features of the tables are briefly discussed.

Today a modern subdivision stands upon the site of Dine's "Benson Observatory," but this photo of farmland outside the village gives us an idea of the terrain Dines called home.  Image courtesy Andrew Smith and Wikimedia Commons.
Today a modern subdivision stands upon the site of Dine's "Benson Observatory," but this photo of farmland outside the village gives us an idea of the terrain Dines called home. Image courtesy Andrew Smith and Wikimedia Commons.

The paper appeared in 1929 in the Quarterly Journal of the Royal Meteorological Society; the lead author is given as “The late W.H. Dines, F.R.S.” It proved a fitting memorial, directly inspiring or informing work by Sir David Brunt (1930) and Guy Callendar (1938)—and even work as late as Swinbank’s “Long-wave Radiation From Clear Skies” (1963.)

Title page of Callendar (1938.)
Title page of Callendar (1938.)

Guy Callendar’s The Artificial Production of Carbon Dioxide and Its Influence On Temperature was undoubtedly the most consequential of these.

Drawing not only upon Dines and Dines (1929), but upon Brunt (1930) and Angstrom (1918), it began Callendar’s ultimately successful campaign to update the ideas of Svante Arrhenius to which Anders Angstrom had referred, and to bring them once again into the scientific mainstream.

Guy Callendar.  Image courtesy Wikipedia Commons.
Guy Callendar. Image courtesy Wikipedia Commons.

Perhaps partly due to the influence of Dines and Dines, it focused strongly upon the role of ‘sky radiation’ in the greenhouse effect. As Callendar’s abstract puts it:

The radiation absorption coefficients of carbon dioxide and water vapour are used to show the effect of carbon dioxide on “sky radiation.” From this the increase in mean temperature, due to the artificial production of carbon dioxide, is estimated to be at the rate of 0.003ºC. per year at the present time.

A particularly interesting feature of Callendar (1938) is that it was published with a “Discussion”—one which reads rather like a transcript of a Doctoral dissertation Defense. (This ritual ‘trial by fire’ forms a normal part of the Doctoral process today.) Callendar apparently faced a committee of leading meteorologists.

To begin with, there was L.H.G. Dines, whom we have already encountered, and Sir David Brunt, who Guy may well have known through mutual connections with the Imperial College. (At that time it was still simply 'Professor Brunt'--he would only be knighted for his contributions to meteorology in 1949.)

Also present were Mr. J.H. Coste, Drs. C.E.P. Brooks and F.J.W. Whipple, and Sir George Simpson, who was perhaps the most famous of all--he had worked in places as diverse as India and Antarctica, and had acquired tragico-romantic luster as a surviving member of the Scott expedition.

All in all, the committee must have been highly intimidating: Whipple had only recently completed his term as President of the Royal Meteorological Society; Simpson's presidency was just a couple of years in the future; and Brunt would, as it turned out, succeed Simpson.

Their questions seem a mix of admiration, condescension toward an outsider (albeit an outsider who was the son of one of England’s leading physicists), and proper scientific skepticism:

Sir George Simpson expressed his admiration of the amount of work which Mr. Callendar had put into his paper. It was excellent work. . . [But Simpson] thought it was not sufficiently realized by non-meteorologists who came for the first time to help the Society in its study, that it was impossible to solve the problem of the temperature distribution in the atmosphere by working out the radiation. The atmosphere was not in a state of radiative equilibrium. . . temperature distribution in the atmosphere was determined almost entirely by the movement of the air up and down. . . One could not, therefore, calculate the effect of changing any one factor. . .

Sir George Simpson--pre-Knighthood--recording observations in 1911.  Simpson had famously accompanied Scott to Antarctica as meteorologist.
Sir George Simpson--pre-Knighthood--recording observations in 1911. Simpson had famously accompanied Scott to Antarctica as meteorologist.

Callendar replied that:

. . . he realized the extreme complexity of the temperature control at any particular region of the earth’s surface, and also that radiative equilibrium was not actually established, but if any substance is added to the atmosphere which delays the transfer of low temperature radiation, without interfering with the arrival or distribution of the heat supply, some rise of temperature appears to be inevitable in those parts which are furthest from outer space.

Walter M. Elsasser.  Image courtesy Wikipedia.
Walter M. Elsasser. Image courtesy Wikipedia.

At the same time in America, a young physicist was working on meteorological problems. His name was Walter M. Elsasser, and he had left a Europe increasingly shadowed by Adolf Hitler. Elsasser (March 20, 1904-October 14, 1991) was employed at the Meteorology Department at CalTech. Although he had no background in meteorology—his work in Europe, which had twice laid foundations for Nobel-winning studies by others, had been in sub-atomic physics—he obtained a modest position addressing the problem of atmospheric radiation:

The American Meteorological Society had for years been urging the American Physical Society to do research on infrared radiation in view of its importance for the atmosphere, but nothing was done. The far infrared spectra of the atmosphere have a very complicated structure that required an understanding of quantum mechanics. . .

Walter spent the years 1937-41 analyzing the properties of far-infrared atmospheric radiation from first principles. After lengthy calculations, he ended up with tables and graphs that a practitioner could use to find the cooling and heating of the atmosphere when he knew the distribution of temperature and moisture. . .

Walter then set out to measure the far-infrared transmission of the atmosphere along paths up to 300 meters in length. This was done on an athletic field next to CalTech with equipment he built. . .

The Bridge Physics Building, Caltech.  Image courtesy Wikimedia Commons.
The Bridge Physics Building, Caltech. Image courtesy Wikimedia Commons.

Elsasser published “Heat Transfer by Infrared Radiation in the Atmosphere” in 1942. It essentially carried out the project Angstrom had proposed: accurate calculation of heating and cooling due to radiation in the atmosphere. (Interestingly, Elsasser’s work was reviewed by none other than C.G. Abbott, but sadly this writer has not yet been able to access that review.) The work today is much-cited in the scientific literature, boasting 248 citations in Google Scholar as of this writing. Refinements, extensions and validations of his work were proposed well into the 1960s.

The interest was two-fold: practically, Elsasser had provided a way for forecasters to quickly calculate radiative cooling or heating in specific situations where temperature and humidity were known: this was to be done by a graphic ‘calculator’ printed on the back cover of the original book. In the reissue from the early 1960s the values were also presented in tabular form.

On the theoretical side, Elsasser’s results could be—and were—compared with other similar calculations. The goal was to refined and improve understanding of the radiative behavior of the atmosphere.

As Kondratiev and Neilisk wrote in 1960:

One of the most reliable and widespread methods of calculating thermal radiation fluxes in the atmosphere is the usage of radiation charts.

As nowadays this is a number of radiation charts based on various principles, their comparison and study is of considerable interest. . . We have examined seven radiation charts by the following authors: F.A. Brooks, A.A. Dmitriev, W.M. Elsasser, R. Mugge & F. Moller, F.N. Shekhter, G. Yamamoto.

On this theoretical front, too, the use of computers was increasingly important. This had been pioneered by Canadian-American physicist Gilbert Plass in the 1950’s.

Gilbert Plass.
Gilbert Plass.

(Plass, who worked for Lockheed on the practical problem of using infrared radiation to guide missiles, “moonlighted” on studies of the radiative effects of atmospheric CO2, and was the first to use computers to perform the lengthy calculations necessary to achieve a really accurate quantitative picture of radiative transfers throughout the atmosphere.) Elsasser’s work naturally informed an important strand of this burgeoning research.

But physics always comes back to measurement, and measurement always relies on technology. And already in 1954, another milestone was reached in the measurement of the “cloud by night.” Sidney Stern and Frederick Schwartzmann published a study in the American Meteorological Society Journal describing their:

. . .long-wave radiometer . . . whose response is essentially independent of air flow and ambient temperature changes. By shielding the sensing element with a hemispherical “window,” the integrated value of the back radiation from the sky can be measured.

Click thumbnail to view full-size
Exploded view of the radiometer.Key to the radiometer was finding a shielding material with suitably flat transmissivity over the IR frequencies of interest for the 'window.'  KRS-5 was the answer.
Exploded view of the radiometer.
Exploded view of the radiometer.
Key to the radiometer was finding a shielding material with suitably flat transmissivity over the IR frequencies of interest for the 'window.'  KRS-5 was the answer.
Key to the radiometer was finding a shielding material with suitably flat transmissivity over the IR frequencies of interest for the 'window.' KRS-5 was the answer.

But Stern and Schwartzmann didn’t stop at simply documenting their instrument. By making radiometer observations (giving observed IR flux) simultaneously with nearby radiosonde flights (giving temperature and humidity readings from which Elsasser tables allowed the computation of calculated fluxes) they showed that:

Satisfactory agreement has been found between theoretical and measured values of the back radiation from the sky during the day and night.

In other words, Elsasser was validated. His calculated values, based primarily upon ‘first principles,’ had come very close indeed. Clearly, a very good understanding of radiative propagation in the atmosphere already existed by 1942.

Mallama's et al. prototype cloud detector in the field.  It is just one practical application of IR imaging and measurement.
Mallama's et al. prototype cloud detector in the field. It is just one practical application of IR imaging and measurement.

Today the design of radiometric IR instruments is no longer the province of the researcher and ‘in-house’ custom instrument fabricator. It is the work of commercial enterprises specializing in scientific instrumentation—Googling ‘ir radiometry company’ returned nearly a million hits as of writing. IR radiometry, spectrometry and imaging are used for a bewildering variety of purposes today.

Click thumbnail to view full-size
A contemporary catalog image highlighting various uses of infrared measurement and imaging.  Image courtesy spi infrared.An infrared spectrometer, use for materials analysis.Mallama et al cloud detector, using IR radiometry to monitor and document cloud cover automatically.  Image courtesy Mallama et al and NASA.
A contemporary catalog image highlighting various uses of infrared measurement and imaging.  Image courtesy spi infrared.
A contemporary catalog image highlighting various uses of infrared measurement and imaging. Image courtesy spi infrared.
An infrared spectrometer, use for materials analysis.
An infrared spectrometer, use for materials analysis.
Mallama et al cloud detector, using IR radiometry to monitor and document cloud cover automatically.  Image courtesy Mallama et al and NASA.
Mallama et al cloud detector, using IR radiometry to monitor and document cloud cover automatically. Image courtesy Mallama et al and NASA.

Indeed, even a hobbyist today can afford an instrument that would have stunned researchers of the past, with prices for digital IR thermometers beginning well under $100. Duplicating Wells’ results is easy, as comments by anonymous blog commenter “DST” show:

I bought myself a cheap $30 IR thermometer recently and was hoping somebody here could offer a possible explanation for some of the measurements I am getting. Over the last two nights I have gone outside just before sunset and measured the ground temperature at between 2C and 5C. At the same time I pointed the thermometer towards the clear sky and received readings between -23C and -27C. It was a few degrees warmer when pointing towards clouds.

About 3 hours after sunset I took the same readings again. This time the sky was clear but fog was starting to settle in. The ground temperature was a couple of degrees cooler as expected but the measurements pointing up into the fog were about 10C warmer.

"Infrared Sky," by Heath Brown.  Image courtesy Heath Brown and Panoramio.
"Infrared Sky," by Heath Brown. Image courtesy Heath Brown and Panoramio.

On the scientific side, the ‘cloud by night’ remains more difficult to measure than the ‘fire by day.’ For the latter, as we saw in Part One, satellite measurements have become the norm and give good coverage—albeit with difficulties stemming from orbital changes and changes of instrumentation still remaining.

But you can’t measure DLR from orbit; you need ground sites, and that fact, combined with the fact that pyrgeometers remain quite expensive, means you can’t achieve the same global coverage that satellites give. Moreover, since DLR varies widely according to atmospheric conditions, it is very important to achieve enough coverage to be sure that we understand how the localized measurements can be generalized to the global scale.

A modern pyrgeometer.  Image courtesy Sch and Wikimedia Commons.
A modern pyrgeometer. Image courtesy Sch and Wikimedia Commons.

To that end, there are more than twenty stations world-wide which maintain an ongoing program of DLR measurements. To date, over 19,000 measurements are archived. As with much climatically relevant data, the Baseline Surface Radiation Network (BSRN) data is available online, though one needs to register as a ‘bona-fide researcher.’ (BSRN is now curated at the Alfred Wegener Institute at Bremerhaven.) More information can be found here:

http://www.bsrn.awi.de

Baseline Surface Radiation Network stations, supplying ongoing high-quality observations of DLR.  Image courtesy Alfred Wegener Institute.
Baseline Surface Radiation Network stations, supplying ongoing high-quality observations of DLR. Image courtesy Alfred Wegener Institute.

One sometimes hears claims that back-radiation ‘violates the Second Law of Thermodynamics’ or is ‘not well-enough understood.’ (Sometimes such claims have been made by those who should understand the need to ‘Read The (Freaking) Literature’ before opining.) As we've seen, such claims, if at all sincere, are proceeding from ignorance.

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25 comments

Doc Snow profile image

Doc Snow 5 years ago from Atlanta metropolitan area, GA, USA Author

Comments, corrections, questions and reactions are all welcome. Let me know what you think!


Anonymous Coward 5 years ago

Anders K Ångström 1888-... is somebody different from Anders Jonas Ångström 1814-1874. Better use the full name.

http://www.wmo.int/pages/publications/bulletin_en/...


Doc Snow profile image

Doc Snow 5 years ago from Atlanta metropolitan area, GA, USA Author

Good point. The elder Angstrom you mention was the grandfather of Anders K. Angstrom, whose work is discussed in this article; the Angstroms formed a bit of a dynasty in physics. But the grandfather was the best-known of the three. I'll clarify that in the text. Thanks!


Robert Kernodle profile image

Robert Kernodle 3 years ago

I honestly do not know what people are measuring, when they claim to measure "downward-welling long-wave radiation" or "back radiation" or "sky radiation" or whatever the preferred term of the day is. I have seen articles by highly credentialed scientists (physicists and applied mathematicians) who question the very legitimacy of such a concept.

But let's put these unconventional views aside for a moment, and accept that certain atmospheric gases (e.g., CO2, for one) DO absorb more heat radiation than their more neutral cohorts (e.g., nitrogen and oxygen mostly). These same absorbers of heat radiation (e.g., CO2) also EMIT the absorbed heat very fast to the surrounding air (mostly nitrogen and oxygen again). So, the CO2 seems to serve as a sort of gateway to move the heat around differently than if only the nitrogen and oxygen were there without it.

CO2 does not exist only at some restricted area in the atmosphere - somewhere high up in the sky, where it radiates absorbed heat from an imaginary, invisible ceiling. Instead, presumably, CO2 is fairly evenly distributed all through the atmosphere - all around our heads and arms and legs - all the way up higher into the troposphere at every location in the troposphere - absorbing and radiating some of its absorbed heat to the also all-surrounding nitrogen/oxygen. CO2 seems to be a sort of heat conduit that causes the nitrogen and oxygen to be a bit warmer, in other words.

But what happens to warm air? It rises, right? The CO2 absorption/emission is going on everywhere to move heat into the nitrogen/oxygen everywhere too, creating masses of air that rise and are displaced by cooler air, pushing the warmer air still higher up, where eventually heat is emitted into outer space.

This process seems to go on continuously: CO2 absorbs heat; ... CO2 emits heat; ... CO2, thus, warms the air a bit; ... the warm air is always rising and getting displaced by relatively cooler air.

So, how does any excessive heat build-up happen near the surface? This convective process always seems to be outrunning any potential buildup, by raising the heat transfer up into the atmosphere AWAY from the surface.

The layers of the atmosphere, then, are mostly caused by fluid dynamics, NOT by radiation. Specifically, the convection of fluid air is the dominant player in Earth's atmospheric heat dynamics. CO2 only seems to be along for the ride. There appears to be no static atmospheric layer where heat just keeps building up. Instead, heat is always being moved up and down. Warm air up. Relatively cooler air down. Warmth ultimately dissipated into outer space.

CO2, thus, seems to ONLY influence how heat moves, NOT how much heat remains in any one layer.

Now if "back radiation" exists, then from WHERE is it coming back? Remember, if I understand correctly, there is no ONE, clearly defined, isolated layer or interface high up, like an imaginary ceiling, where an exclusive unidirectional downward flow originates uniquely. Instead, radiation from CO2 seems to be coming from ALL AROUND, FROM EVERYWHERE, because CO2, presumably, is well distributed throughout the entire atmosphere in question.


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

Comment: "I honestly do not know what people are measuring, when they claim to measure "downward-welling long-wave radiation" or "back radiation" or "sky radiation" or whatever the preferred term of the day is. I have seen articles by highly credentialed scientists (physicists and applied mathematicians) who question the very legitimacy of such a concept."

Response: They are measuring infrared radiation coming from the sky. Those questioning the concept need to explain the 200 years of measurement of this DWLR if they wish to have any claim to legitimacy in commenting upon the greenhouse effect.

It's pretty ironic that many commenters try to pillory mainstream science for the supposed 'mistaken theoretical construct' of DLWR, calling them 'ivory tower theorists' and the like, when those same commenters refuse to deal with this body of empirical, hard data.

Comment: "CO2 does not exist only at some restricted area in the atmosphere..."

Response: Correct. It is a 'well-mixed gas.'

Comment: "But what happens to warm air? It rises, right? The CO2 absorption/emission is going on everywhere to move heat into the nitrogen/oxygen everywhere too, creating masses of air that rise and are displaced by cooler air, pushing the warmer air still higher up, where eventually heat is emitted into outer space."

Response: Correct, more or less. Convection is very important in the atmosphere--it's important in determining the lapse rate.

Comment: "So, how does any excessive heat build-up happen near the surface? This convective process always seems to be outrunning any potential buildup, by raising the heat transfer up into the atmosphere AWAY from the surface."

Response: Well, you *say* "it seems to be outrunning any potential buildup," but without saying why you think so. But there is a normal atmospheric lapse rate, by which temperature tends to decrease as a function of altitude. Wouldn't you say that IS "a buildup" of heat in the lower layers of the atmosphere?

Comment: "Instead, radiation from CO2 seems to be coming from ALL AROUND, +FROM EVERYWHERE..."

Response: Yes, CO2 (and other GHGs, such as water vapor) radiate in all directions, and are indeed observed to do so. However, only (more or less) downward fluxes do anything to counteract any convective transport that may be occurring.


Robert Kernodle profile image

Robert Kernodle 3 years ago

So, you appear to contend that radiative heat transport counteracts convective heat transport. My understanding is that convective heat transport is many, many orders of magnitude greater than radiative heat transport, ... dwarfing it, in fact, which is what leads me to suggest that the radiative aspect is only "along for the ride", having very little effect on the overall temperature of any particular atmospheric layer.

Now to answer your question, [["But there is a normal atmospheric lapse rate, by which temperature tends to decrease as a function of altitude. Wouldn't you say that IS "a buildup" of heat in the lower layers of the atmosphere?"]]:

I would say that there is a partitioning of atmospheric layers, aligned by the fluid dynamic actions of the whole atmospheric mass, mediated by gravity, pressure, and convective heat transport. Fairly definite interfaces can occur in fluids, whether air or water or whatever, because of density differences, pressure differences, chemical concentration differences, and other factors unrelated to immediate heat input. This is what I would say delineates the various atmospheric layers.

And as to your response, [["Those questioning the concept {BACK RADIATION} need to explain the 200 years of measurement of this DWLR if they wish to have any claim to legitimacy in commenting upon the greenhouse effect."]]

Those questioning the concept do a very convincing job of explaining precisely why the 200 years of measuring DWLR might be a confusion, which is why I myself started questioning it.


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

Comment: "My understanding is that convective heat transport is many, many orders of magnitude greater than radiative heat transport..."

Response: Then you are incorrect. These things are measured, and have been measured for quite a while now. See, for example, the famous Kiehl-Trenberth diagram which you dismiss as 'fiction.' If you read the source paper, you will find that the energy terms in that diagram are arrived at by collating and comparing a great many empirical studies.

A rather new review article summarizing the state of the art is here:

http://link.springer.com/article/10.1007/s10712-01...

I should add also that while convection is important within the atmosphere, the only way that Earth as a whole can lose heat is via radiation. No meaningful convection at the 'top of the atmosphere!'

Comment: "I would say that there is a partitioning of atmospheric layers..."

Response: Perhaps you don't realize it, but you are changing the subject. The point is that there *is* a 'build-up,' not what causes it--unless you are just agreeing with me in a roundabout fashion. Moreover, your description of factors that 'could' affect stratification in general really offers nothing toward why the temperature profile of the atmosphere is what it is.

Comment: "Those questioning the concept do a very convincing job of explaining precisely why the 200 years of measuring DWLR might be a confusion..."

Response: Really? Then you should point me to it. I found no such account in G & T; in fact, I found no clear indication that they were even aware of that measurement at all.


Robert Kernodle profile image

Robert Kernodle 3 years ago

I, Robert, previously said: "My understanding is that convective heat transport is many, many orders of magnitude greater than radiative heat transport..."

You, Doc, responded: [["Then you are incorrect."]]

Am I, indeed incorrect? Let's first look at a fairly neutral information source, for example:

http://jarred.github.com/src-img/

... which states,

"Convection is the most effective form of heat transfer in liquids and gases."

Here, I assume it's okay to consider the words, "transport" and "transfer" as synonyms.

A person, thus, is led to consider that the Earth's atmosphere convects heat away from the surface through this continuous process, vertically upward, as the MOST EFFECTIVE form of heat transfer in the gaseous Earth atmosphere.

And let's look at what Clive Best [Bsc in Physics, PhD in High Energy Physics, research fellow at CERN for 3 years, Rutherford Lab for 2 years, JET Nuclear Fusion experiment for 5 years, and The joint Research Centre in Italy] has to say:

http://clivebest.com/blog/?p=4432

"The atmosphere receives 5 times more heat energy from convection and evaporation latent heat than it does from radiation."

_________________________________________________

Doc, you then remind me: [["I should add also that while convection is important within the atmosphere, the only way that Earth as a whole can lose heat is via radiation. No meaningful convection at the 'top of the atmosphere!'"]]

I now point out that I NEVER suggested that the "Earth as a whole" could loose heat via convection. Rather, I suggested that convection is always MOVING heat upwards to a place where it can be radiated into space. Radiation does NOT keep heat statically in the lower levels where it builds up without this intervening pumping of air to the upper atmospheric layers.

_________________________________________________

Our next interchange deserves a complete representation, so here it is:

{ Comment: "I would say that there is a partitioning of atmospheric layers..."

Response: Perhaps you don't realize it, but you are changing the subject. The point is that there *is* a 'build-up,' not what causes it--unless you are just agreeing with me in a roundabout fashion. Moreover, your description of factors that 'could' affect stratification in general really offers nothing toward why the temperature profile of the atmosphere is what it is.}

Change the subject? Absurd, Doc, I did no such thing. I clarified a point. I agree that there is a so-called "build-up", but the build-up is NOT the reason you adhere to, and to explain this, I have to clarify the point, which you call "changing the subject", which I call your making an absurd response to a clarifying attempt on my part. Next, you dismiss my further general comments to clarify the point as "offering nothing". Again, absurd. Gravity and pressure most certainly offer something towards explaining why the temperature profile of the atmosphere is what it is.

_________________________________________________

... and our next exchange went like this:

{Comment: "Those questioning the concept do a very convincing job of explaining precisely why the 200 years of measuring DWLR might be a confusion..."

Response: Really? Then you should point me to it. I found no such account in G & T; in fact, I found no clear indication that they were even aware of that measurement at all.}

Okay, Doc, maybe take another look at this:

http://hubpages.com/education/CO2-Greenhouse-Theor...

As I point out in the section headed, A NEW CLIMATE PARADIGM,

Ned Nikolov, Ph.D. & Karl Zeller, Ph.D. (2011). Unified Theory of Climate: Expanding the Concept of Atmospheric Greenhouse Effect Using Thermodynamic Principles -- Implications for Predicting Future Climate Change, http://tallbloke.files.wordpress.com/2011/12/unifi...

"Modern Global Climate Models do NOT solve simultaneously for radiative transfer and CONVECTION. This failure to account for all actual heat transports is the main reason the models project surface warming in response to rising atmospheric greenhouse gas concentrations. Consequently, CO2-driven global temperature forecasts are model artifacts!"

And here's a link to an illustration of the mathematical MIScalculation of convection often used in popular accounts:

http://s4.hubimg.com/u/6498575_f496.jpg


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

1) Robert, there's a big difference between "most effective" across a wide range of liquids and solids and "many orders of magnitude."

And in fact your source, Clive Best, makes quite clear that the relative efficacy of radiation vs. convection depends upon the circumstances.

2) Robert, you did say that there was no 'buildup' of heat. I'm glad that you are willing to retract that statement, so that we don't need to discuss that point anymore.

We also don't need to discuss the idea that convection does move heat upward; I've been saying that all along. However, radiative cooling is also important. As noted in this Hub, calculating that cooling (or warming) is an important facet of practical weather forecasting. (Cf., the discussion of Elsasser's work, above.)

3) Gravity and pressure may have something to do with the atmosphere's temperature profile. But you really haven't said what.

4) I fail to see the relevance of the statement you quote to the proposition that backradiation is a 'fiction' or a 'misunderstanding.'

Moreover, climate models do model convection:

http://journals.ametsoc.org/doi/abs/10.1175/1520-0...

(Note that that paper was from 1999, and that it was mainly concerned with improving the modeling of water vapor transport by convection; the temperature effects were already reasonably well handled, as I understand it.)


Robert Kernodle profile image

Robert Kernodle 3 years ago

Doc,

It is always an interesting exercise to compare notes on the sources that have shaped our beliefs, and this is what I am doing here.

Nikolov & Zeller do a pretty good job of explaining the gravity/pressure issues:

Ned Nikolov, Ph.D. & Karl Zeller, Ph.D. (2011). Unified Theory of Climate: Expanding the Concept of Atmospheric Greenhouse Effect Using Thermodynamic Principles -- Implications for Predicting Future Climate Change, http://tallbloke.files.wordpress.com/2011/12/unifi

As for back radiation being a misunderstanding, Claes Johnson (I'll have to relocate the link) does a pretty good job with that point. He is a distinguished applied mathematician, who, of course has received heated criticism by anthropogenic warming enthusiasts, but his credentials and accomplishments in his field sure make you wonder whether he has nailed one of the greatest misconceptions of our times.

Since the issues here revolve around carbon dioxide and back radiation, an illustrative example might serve to help reveal the "misunderstanding".

Comparing the almost-all-carbon-dioxide atmosphere of Venus to the LESS-than-ONE-percent-carbon-dioxide atmosphere of Earth, a person can have a startling realization, which is this:

The radiating temperature of the two planets can be accounted for with NO references to the chemical compositions of their atmospheric gases and with NO references to the radiating properties of those atmospheric gases, as if CO2 makes no difference whatsoever in determining these respective planetary radiating temperatures. The only main factors that seem to matter are how close the planet is to the sun and what the atmospheric pressure is in the region being measured.

Venus is 1.38 times CLOSER to the Sun than Earth. The intensity of the Sun's radiation increases, of course, the closer the planet is, by a factor of the distance squared, which means Venus gets 1.38-squared (or 1.91) MORE solar radiation than Earth. The RADIATING TEMPERATURE of Venus, then, is the fourth root of 1.91, or 1.176 greater than the radiating temperature of Earth.

On Earth, at sea level or zero altitude (1000mb pressure), the Earth temperature (Kelvin) is about 287K. On Venus, at about 50 kilometers up, at the same pressure of 1000mb, the Venus temperature (Kelvin) is about 339K. Here's the shocker: when you multiply Earth's 287K by Venus' 1.176 greater radiating temperature, figured from Sun distance alone, you get very close to Venus' 339K, within a degree or two. Remember, the only main considerations have been distance from the Sun and atmospheric presssure. This same relationship seems to hold all throughout the Venusian atmosphere, so when you go to OTHER altitudes on Venus where the pressures are the same as on Earth, you see temperature differences in the same ratio, 1.176 (within a reasonable margin of error).

Here it is again:

Earth .... our point of reference with reference radiating temperature

Venus ... 1.176 greater radiating temperature, figured from difference in planets' distances from the Sun

Earth ..... 1000mb pressure, zero altitude........ 287K

Venus.... 1000mb pressure, 50 km altitude .... 339K

Earth's 287K multiplied by 1.176 greater, SUN-DISTANCE-figured radiating factor equals (very nearly) Venus' 339K.

Conclusion, CO2 (and its "back radiation") makes LITTLE difference, because at the same level of pressure on BOTH planets, the only thing that seems to matter is planetary distance from the sun. If CO2 (and its "back radiation") had any significant effect, then a person would expect that, at the same atmospheric pressure, an almost-all-carbon-dioxide-atmosphere would show a much greater "greenhouse effect", but what the almost-all-carbon-dioxide-atmosphere shows is ONLY an incremental temperature increase based on closer proximity to the Sun.

A similar comparison between other planets in the solar system reveals similar relationships between the planets' various distances from the Sun and the planets' various atmospheric pressures, regardless of chemical compositions of the planets' atmospheric gases, ... regardless of those atmospheric gases' abilities to produce "back radiation".

Radiative properties of atmospheric gases, thus, seem to be minor players in atmospheric thermodynamics.


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

Robert, I'll consider your comment in more detail later because it will take some time to consider the information, and I don't have much time right now.

However, I must say that your "conclusion" doesn't at all follow from the facts you present, striking though the correspondence you present may be. Basically all you are showing is that you can scale the lapse rate of Venus and Earth, which is not surprising given that lapse rate is related to the ideal properties of gases.

I'll save the details for later, but will quickly mention two salient facts:

1) The Venusian atmosphere is pretty opaque at most frequencies due to dense permanent clouds of (IIRC) sulfuric acid, which is why planetary probes going there had to land or use radar to derive information about the surface. Not so Earth, obviously. Clearly a big difference that's quite material to the planet's heat budget.

2) Venus has a day longer than its year--'retrograde' as it is (or used to be) called. Yet despite this very slow rotation, the temperature varies quite little between day and night sides. Again, clearly very different to Earth.

So, no, I don't think at first blush that the comparison of the two planets suggests that chemical composition of the atmosphere is unimportant.


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

Robert, with a little more time to work through what you wrote, it appears to me that the reasoning--I'm not sure if it's yours or Claes Johnson's--is circular.

I check you on the insolation of Venus compared to Earth--well, actually I got 1.92, but I'm sure that's just a rounding error which we can neglect.

However, things become a bit fuzzy when the term 'radiating temperature' comes in. Googling it did not reveal it to be a standard term, but the fourth root used to calculate it suggests that it is either equivalent to, or directly derived from, "blackbody temperature" (as calculated from the Stefan-Boltzman equation.)

If so--and I welcome your clarification--it seems that the assumption is that the 'radiating temperature' is uniquely determined by insolation. Unfortunately for your (or Dr. Johnson's) argument, that is what is supposedly being proven. But you can't prove something by assuming it to be true.

Of course, we *can* check the actual temperature of the Venusian surface, since we have direct measurements. The surface temperature of Venus is (as you probably know) a hefty 740 K. That's much higher than the simple comparison of insolation would indicate.

Intriguing is the comparison to Mercury, which has only a trace of atmosphere:

"The large amount of CO2 in the atmosphere together with water vapour and sulfur dioxide create a strong greenhouse effect, trapping solar energy and raising the surface temperature to around 740 K (467°C) hotter than any other planet in the solar system, even that of Mercury despite being located farther out from the Sun and receiving only 25% of the solar energy Mercury does."

By the logic of the comment, Mercury should have a 'radiating temperature' that's 1.34 times Venus. You may object that Mercury doesn't have an atmosphere, and that must account for the difference. I rather imagine that is true. But follow the calculation you gave:

"Venus is 1.38 times CLOSER to the Sun than Earth. The intensity of the Sun's radiation increases, of course, the closer the planet is, by a factor of the distance squared, which means Venus gets 1.38-squared (or 1.91) MORE solar radiation than Earth. The RADIATING TEMPERATURE of Venus, then, is the fourth root of 1.91, or 1.176 greater than the radiating temperature of Earth."

The 'radiating temperature is determined without reference to *any* atmospheric component--including pressure.

I know, elsewhere in the comment the difference between the 50 km temp and surface temp is *said* to be accounted for by atmospheric pressure--somehow, in some way not defined in what you write, at least. However, that's not what the work shows.

Anyway, the assumption of temperature having some kind of simple relationship to atmospheric pressure seems quite counterfactual, as you will see if you compare the temperature profiles of Venus, Earth and Jupiter. (I'll forbear linking, since you can Google those up as readily as I can, and so, I expect can any interested readers who may happen along.)


Robert Kernodle profile image

Robert Kernodle 3 years ago

Doc,

The temperature DOES appear to have a simple relationship to the COMBINATION of distance from the Sun AND atmospheric pressure. This is the surprise.

I did NOT say the relationship is between atmospheric pressure ALONE, as you seem to attribute to me. I am comparing an almost-all-carbon-dioxide atmosphere to a less-than-one-per-cent carbon dioxide atmosphere, and I stand by the comparison. I will have to study how you are trying to confuse it.

I am comparing [pressure] AND [sun distance] WITH REGARD to [atmospheric CO2]. Three RELATED considerations. Remove the sun distance consideration, and you are not observing the proper comparison. Underplay the CO2 atmospheric composition, and again you are not observing the proper comparison.

The fact that Venus shows little day/night variation seems to add even more support to the idea that CO2 radiation is having little to do with its temperature. Something else is acting MORE strongly than the gas radiating properties to create that temperature.

If a planet with 98% CO2 can show this lack of relationship with CO2 and temperature, then why would we expect a planet with less than 1% CO2 to, all of a sudden, give CO2 some magical heat radiating properties in its ridiculously smaller proportionate measure?


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

Robert, no offence, but I'm quite bemused by this response.

I never "removed the sun distance consideration," as you suggest. In fact, I extended it to consideration of Mercury--a notion you seem to be ignoring.

Specifically, I pointed out that since Mercury's insolation is basically 4 times Venus's--and that's even before we get to planetary albedo!--one should expect from your example that Venus's surface temperature would be much less that Mercury's. Yet in reality, it's roughly 100 degrees higher!

You will tell me that that is due to Mercury lacking an atmosphere--that the difference is due to atmospheric pressure.

OK. But how? You haven't said, and the one example of working it out ignored pressure completely. Please explain how pressure affects planetary temperature. (Remembering, as I pointed out above, that the vertical temperature profiles of Earth, Venus and Jupiter don't suggest that the relationship is simple.)

I'm equally bemused by your statement that:

"The fact that Venus shows little day/night variation seems to add even more support to the idea that CO2 radiation is having little to do with its temperature. Something else is acting MORE strongly than the gas radiating properties to create that temperature."

In fact, that's exactly what we would expect from a super-strong greenhouse effect: the whole point of the greenhouse effect is that it decreases the rate at which the planet can cool, by decreasing radiative efficacy at (local) thermal wavelengths. That means that the greenhouse effect can have a very great effect at night, when there is no insolation. "It must be something else," you insist. But you've really not shown what it might be, other than a statement that pressure could have something to do with it.

So, to sum up, in Venus we see a planet in which radiative cooling seems nearly nonexistent, and which sustains ambient temperatures far in excess of what Mercury achieves even after 20 or so Earth days of straight sunshine at an intensity roughly 4 times that of Venus! By an amazing 'coincidence', the atmosphere there features 92 bars of CO2, as you point out.

So--WHAT "lack of relationship" between CO2 and temperature do you see, exactly? Venus is an inferno, and it's drowning in CO2 (metaphorically speaking, of course.) It's just what one would predict from greenhouse theory. (And of course, both Carl Sagan and James Hansen cut their scientific teeth on studies of the Venusian atmosphere.)


Robert Kernodle profile image

Robert Kernodle 3 years ago

Doc, no offense taken, and I hope you will not take offense at my amusement with your own previous reply, which I have now had time to work through a bit.


Robert Kernodle profile image

Robert Kernodle 3 years ago

Let's look at some of your earlier points, together with my responses to them:

[["... it seems that the assumption is that the 'radiating temperature' is uniquely determined by insolation. Unfortunately for your (or Dr. Johnson's) argument, that is what is supposedly being proven. But you can't prove something by assuming it to be true."]]

Radiating temperature IS uniquely determined by insolation. "Insolation" is the amount of the sun's energy adding heat to the atmosphere. This is THE major determinate of a planet's temperature. This is a given. It does NOT need to be proven. It is a fundamental assumption that is already proven and accepted. It is basic physics. What other primary source outside the planet provides its foundational heat? I thought that there was only one - again, the SUN.

[["The surface temperature of Venus is (as you probably know) a hefty 740 K. That's much higher than the simple comparison of insolation would indicate."]]

Higher than the comparison? No, it is NOT - it follows from the curve on which the other temperatures are located. See the graphs here:

http://www.datasync.com/~rsf1/vel/1918vpt.htm

[["Intriguing is the comparison to Mercury, which has only a trace of atmosphere:

You will tell me that that is due to Mercury lacking an atmosphere--that the difference is due to atmospheric pressure. OK. But how? Please explain how pressure affects planetary temperature. (Remembering, as I pointed out above, that the vertical temperature profiles of Earth, Venus and Jupiter don't suggest that the relationship is simple.)”]]

Pressure causes heat. How do stars form? - they aggregate under huge pressures that cause the temperature to rise. Planetary atmospheres obey the same physics, except under much smaller pressures than star-forming pressures. I never said that the relationship was simple across the entire solar system. But the relationship seems fairly simple, with regard to the inner planets, Mercury, Venus, Earth, and Mars. The gas giants, Jupiter, Saturn, Uranus, and Neptune do NOT have solid surfaces or distinctive solid/liquid/gas interfaces like the inner planets, so here we are talking about another “species” that operates more consistently fluid dynamically throughout the ENTIRE planet, not just in the planetary atmosphere. On Jupiter, there is NOT a surface. There is NOT a DELINEATION between a gaseous “atmosphere” and a solid or liquid “surface”. Jupiter is gas, or more properly, fluid, through and through.

[["The 'radiating temperature is determined without reference to *any* atmospheric component--including pressure."]]

Yes, because we are talking about the radiating temperature of the planet AS A WHOLE (“black-body temperature”, I believe is an acceptable term), which INCLUDES the atmosphere, ...the whole body as seen from a distance in space. The pressure observation comes in, when we go deeper into the whole. Here is when we observe the pressure/temp/CO2 relationship. With terrestrial-like planets, the relationship is consistent - consistent with pressure profiles viewed from WITHIN, and consistent with distance-from-sun profile viewed from WITHOUT. This is the surprise. Why exactly is not even necessary to know in noting the fact itself. The fact itself is that the relationship is there, and it has ZERO to do with carbon dioxide.

[["Anyway, the assumption of temperature having some kind of simple relationship to atmospheric pressure seems quite counter-factual, as you will see if you compare the temperature profiles of Venus, Earth and Jupiter."]]

The assumption is actually QUITE factual.

Again, when we start talking about Jupiter, we are talking about the so-called “gas giant” planets, which also include Saturn, Uranus, and Neptune. These really do NOT compare to the inner terrestrial-like planets, Mercury, Venus, Earth, and Mars.

Jupiter does NOT have any solid surface - it is essentially ALL fluid, all the way down to its core apparently (almost like a cold star that never ignited due to its sub-star mass). Jupiter's dynamics are better thought of as completely fluid dynamic, as though it were one big ball of liquid, where fluid dynamic currents throughout its entire mass determine the various temperatures.

So what you are doing incorrectly, first, is trying to relate my information to a planet with NO atmosphere (Mercury), and incorrectly, second, trying to relate my information to a planet with NO solid surface (Jupiter). Again, you are MIS-comparing, to cause needless confusion of the simple facts. Planets with solid surfaces and with CO2 in their atmospheres show a clear pattern of relationships between atmospheric pressure, distance from the sun, and radiating temperature. This relationship shows that temperature of the planet has nothing to do with the heat radiating properties of CO2 gas.

And ALL planets, both terrestrial-like planets AND “gas giants”, seem to demonstrate that pressure is a dominant player in the temperature profile.


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

"Radiating temperature IS uniquely determined by insolation."

Well, no--not if, as you seem to say, it is equivalent to the 'blackbody temperature.' Certainly the sun is the only significant source of heat for most planets. However, the atmosphere plays a role in determining the temperature at the surface. That is clearly shown by the example of Venus and Mercury: Mercury should be hotter but the reverse is true.

Moreover, I would suggest that you are forgetting something: the temperature of any object is the result of two things: its heat gain, and its heat loss. Mercury, with no atmosphere, radiates heat away very efficiently indeed. Earth is thought to be about 30 degrees warmer on average than it would be with no atmosphere. Clearly, the case for Venus is remarkable: it would not be nearly as hot, if, like Mercury, it could radiate so efficiently.

As to the putative 'simple relationship between temperature and pressure,' please look at the vertical temperature profiles of Venus and Earth:

http://en.wikipedia.org/wiki/File:Comparison_US_st...

http://en.wikipedia.org/wiki/File:Venusatmosphere....

If you choose not to consider Jupiter because it is a gas giant, fine--I thought it an interesting case, since there you can find pressure comparable to Venus's, unlike on Earth.

But the temperature curves for Venus and Earth simply cannot be scaled to one another as you suggested. They aren't even the same shape. (Ironically, Jupiter's is rather closer to Venus's than is Earth.)

"Pressure causes heat."

No, frankly, it doesn't. In a star in the process of forming, contraction under gravitational pressure causes temperature to rise--but it's not the pressure, it's the contraction. In other words *changes* in pressure cause heating. To take a familiar real-world example, if you quickly inflate a tire, it may warm due to the increase in internal pressure. However, that increased warmth will increase radiation--Stefan-Boltzman again--which will bring the tire back into thermal equilibrium with its surroundings. (Yes, convection too.)

By contrast, the atmospheres of the various planets have been approximately as they are for a very long time indeed: no change in pressure to speak of to power warming (or cooling, for that matter.)

To claim otherwise is to claim that energy is being created ex nihilo--and that, if you'll recall, would be a rather stark violation of the First Law of Thermodynamics. You'd be claiming, in essence, that a planet could radiate forever, powered only by its atmospheric pressure, and without ever cooling down.

Robert, I am not causing "needless confusion of the simple facts." I am offering you the opportunity to exercise critical thought by affording factual points of reference.

So again, think about these questions without simply dismissing them as contradicting Holy Writ:

--If insolation is the sole determinant of 'radiating temperature', why is Venus hotter than Mercury, despite the fact that the latter gets roughly 4x as much sun? I say it's because the 92 bars of CO2 create an enormous greenhouse effect which warms Venus far beyond what we would otherwise expect.

--Why, if pressure is the sole determinant, do atmospheres show different patterns of temperature changes as pressure changes?


Robert Kernodle profile image

Robert Kernodle 3 years ago

Doc,

I could answer all your points exactly in order, as you have posed them, but in THIS post, let's first look at Venus again, very closely:

Given Venus' closer distance to the Sun, Venus receives almost twice the Earth's solar radiation. Since 76% of this radiation is reflected by clouds, and most of the rest of the radiation is absorbed by these clouds at the top of Venus' atmosphere, only a tiny 2.5% of the solar radiation ever reaches Venus' surface.

Venus, as you have pointed out, has a day/night cycle of 117 days (meaning, of course, that one side of the planet is sunny much of the time, while one side of the planet is dark much of the time). This means that the proposed CO2 greenhouse effect there would have to boost the tiny 2.5% of Venus' incident solar radiation to heat BOTH the sunny side and the dark side of the planet to its immense average temperature of over 700K!

Let me say this again: CO2 would have to be able to boost only 2.5% of the solar radiation to produce temperatures of 700K on BOTH the sunny side AND the dark side of the same planet at the same time. I do NOT know of any scientific proof that CO2 has this magical heat-enabling property.

I would venture to say that nobody really understands in detail how Venus' atmsphere works. If CO2 WERE a main player, then I suspect that it would be from the TOP of the atmophere down, instead of the popular bottom of the atmosphere up. But even so, this would not fully explain the high surface temperatures on both sides of the planet. This is why I wrote that I believe something else has to be going on, and, consequently, there is even MORE reason to discount a so-called “greenhouse effect” on Venus, as the driver of the planet's temperature.

Venus' huge atmospheric pressure, then, seems like an attractive candidate for some of the heating, at least. Perhaps geothermal heating might be another candidate. ... A combination of causes might be the truth, for example, top-down radiative heating, geothermal heating, a tiny bit of surface heating from the Sun, all amplified by atmospheric pressure. But “back-radiating” CO2 greenhouse effect alone? No way in Venus' hell, so to speak.

And atmospheric pressure, while it does NOT introduce constantly NEW pressure, DOES maintain a consistent pressure on constantly new INCOMING energy, thereby enhancing or amplifying kinetic energy, rather than just providing a neutral container into which such energy develops. So, NO "energy ex nihilo" from me.

You wrote:

[["No, frankly, it doesn't. In a star in the process of forming, contraction under gravitational pressure causes temperature to rise--but it's not the pressure, it's the contraction. In other words *changes* in pressure cause heating. To take a familiar real-world example, if you quickly inflate a tire, it may warm due to the increase in internal pressure. However, that increased warmth will increase radiation--Stefan-Boltzman again--which will bring the tire back into thermal equilibrium with its surroundings. (Yes, convection too.)"]]

This is twisted, ... to attribute the EFFECTS of pressure ONLY when pressure is in the ACTION of changing from one quantity to the next.

A star forms, because a given pressure is so great that heat is generated, then MORE pressure causes MORE heat. The heat is already there from the first pressure increase, and it does not magically go away waiting for the next pressure increase to react.

An inflated tire, once the inflation stops, has nothing new being added to it, so the initial heat dissipates. But under a given pressure, adding energy IN ADDITION to the pressure already there, exposes the added energy to a force that causes the molecules to move more vigorously than they would under a lesser pressure. The molecules, under less pressure, would have more room to move around more slowly, so to speak. Thus, adding solar radiation to a 1 bar atmosphere is NOT the same as adding the same amount of solar radiation to a 92 bar atmosphere.


Robert Kernodle profile image

Robert Kernodle 3 years ago

First, some people used to say that "back radiation" adds additional heat to the atmosphere. Now these people say, "NO, we never said that. We said that 'back radiation' does not add heat - it 'slows down' cooling, which means 'back radiation' slows down heat movement."

So, how does "cooler heat" slow down "hotter heat", if not by adding additional heat SOMEWHERE in between, additional heat derived from the first heat that it now "slows down"?

THERE's your "energy ex nihilo".

How many different wrong ways can a person say it, before coming to a realization that the mechanism just might not exist, as it is popularly conceived?

There is radiation. There is absorption. There is emission. In the atmosphere, there is convection; there is evaporation, condensation, and other factors, ... in a whole THERMODYNAMIC process that far outstrips the radiative process ALONE.


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

Robert, you are totally wrong. But I may not be able to explain in detail for a couple of days, due to extremely intense work commitments. Sorry...


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

I have a few moments, so a few quick comments:

"Let me say this again: CO2 would have to be able to boost only 2.5% of the solar radiation to produce temperatures of 700K on BOTH the sunny side AND the dark side of the same planet at the same time. I do NOT know of any scientific proof that CO2 has this magical heat-enabling property."

Well, "proof" is a problematic term in science, but there is a *lot* of *evidence* that CO2 can indeed create just such an intense greenhouse effect--albeit the mechanism is far from "magical." My Hubs lay out the early science on this, from Fourier--1824 or so--to Gilbert Plass, from 1938 into the early '60s. Other pivotal early work came from Manabe, in the '60s and '70s, and his collaborators.

Your incredulity that such an intense greenhouse effect is possible has, I am afraid, no probative value whatever. In fact, "argument from incredulity" is considered a logical fallacy.

"If CO2 WERE a main player, then I suspect that it would be from the TOP of the atmophere down, instead of the popular bottom of the atmosphere up."

Good intuition! The supposed 'popularity' of the 'bottom-up' model you discuss is mostly among debunkers who haven't been reading the literature. Mainstream researchers seem to be in agreement that the greenhouse effect does indeed work from the top of the atmosphere down to the surface. Although back radiation is real, it does not play a major role in the greenhouse effect--mostly because of the lapse rate, which is mostly set by convection. (I actually thought the Clive Bell discussion of this point that you linked to was pretty good.)

What *does* drive warming is that, as the mean free path length of thermal radiation shortens, the mean altitude at which radiation escapes to space rises. The lapse rate means that radiation is reaching space from ever-cooler regions--which also means that radiative efficacy decreases.

"But even so, this would not fully explain the high surface temperatures on both sides of the planet."

Sorry, but with no analysis to support this statement, it is once again a pure argument from incredulity.

"And atmospheric pressure, while it does NOT introduce constantly NEW pressure, DOES maintain a consistent pressure on constantly new INCOMING energy, thereby enhancing or amplifying kinetic energy, rather than just providing a neutral container into which such energy develops. So, NO "energy ex nihilo" from me."

Sorry again, but energy ex nihilo is precisely what you are describing. Radiation raises temperature by a specific amount--the energy of the radiation must precisely balance the energy of the temperature change. Any "amplification" by pressure would amount to the creation of 'new, extra' energy. Doesn't happen--unfortunately, I suppose, because if it did we'd really be able to build perpetual motion machines.

"A star forms, because a given pressure is so great that heat is generated, then MORE pressure causes MORE heat."

Nope. The essence of the process is that accumulating of mass increases gravity, which makes further mass increases more probable. At some 'tipping point,' the process becomes pretty much unstoppable except by exhausting the nearby matter. As the matter accumulates, it condenses under gravitational pressure. If there is sufficient matter, the increasing density/pressure will drive temperatures high enough for nuclear 'ignition.' Then the expansive force of the nuclear reaction, and the heat it generates, can balance the But the critical point is that it is all driven by gravitational 'collapse.'

Regarding your second comment, I hope that what I said above helps clarify the matter of 'back radiation." It is a real phenomenon, as the long history of directly measuring it shows. And it makes sense: as mean optical path lengths shorten, at the surface you would expect to see more intense back radiation, because it would be reaching you from lower, warmer altitudes on average. (Just the converse of what I wrote above about the top of the atmosphere.)

But convection makes it a bit of a sideshow--albeit one that often must be taken into account, especially for smaller-scale investigations (or forecasts--cf., the story of Elsasser, which I told above.)


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

By the way, some of the 'how a star forms' stuff is pretty fascinating. I think a lot has been learned about it since I last read up on it. Check this out:

http://en.wikipedia.org/wiki/Star_formation#Protos...


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

And specifically on Venus: Carl Sagan's reputation was established with his work with the microwave radiometer instrument flown aboard Mariner 2, which did a 'fly by' mission to observe Venus. Sagan had proposed very high Venusian surface temperatures, and ascribed them to an ultra-strong greenhouse effect on the basis of careful calculations using all that was then known. Mariner confirmed that he was correct about the surface temperature; Sagan published a seminal paper on the topic in 1960.

But exploration continued, with multiple probes landing throughout the succeeding decades, and much was learned about the structure of the Venusian atmosphere. In 1980, 20 years of science was summed up in this paper by James Pollock et al.:

http://onlinelibrary.wiley.com/doi/10.1029/JA085iA...

Their abstract states:

"We find that the observed surface temperature and lapse rate structure of the lower atmosphere can be reproduced quite closely with a greenhouse model that contains the water vapor abundance reported by the Venera spectrophotometer experiment. Thus the greenhouse effect can account for essentially all of Venus' high surface temperature. The prime sources of infrared opacity are, in order of importance, CO2, H2O, cloud particles, and SO2, with CO and HCl playing very minor roles."

As far as I can tell, the 'big picture' hasn't changed that much since then. Work toward increasing the knowledge in detail about Venus continues, but there seems to have been more of a focus on vulcanism and the SO2 content of the atmosphere. There is this paper from 1996, for example:

http://onlinelibrary.wiley.com/doi/10.1029/95JE038...

"The surface temperature and pressure on Venus coincide approximately with the P-T equilibrium of the calcite-wollastonite mineral reaction, and atmospheric sulfur species are probably involved in rapid heterogeneous reactions with the surface. Perturbations to the atmospheric inventory of radiatively active species may have a significant impact on the climate of Venus and upon the stability of the greenhouse effect. Through the use of a Venus climate model that couples atmospheric radiative-convective equilibrium with surface processes, we show that it is likely that Venus' climate is at or near a state of unstable equilibrium. Furthermore, we show that only moderate perturbations in the abundances of radiatively active volatiles may be sufficient to precipitate changes to new climate regimes."


Robert Kernodle profile image

Robert Kernodle 3 years ago

Why would a person display incredulity, unless reasoning were so confused, and physical facts were so ignored, by so many, for so long?

Emotional tone is a register of the logic that underlies it. In a discussion forum, such mixture of tones seems appropriate. This is NOT a peer-reviewed journal, after all.

In my view, you still try to complicate a very basic, physical, real, known relationship, which is: At equal pressures on BOTH Venus and Earth, the difference in temperature can be accounted for ONLY by the ratio of the two planet's distances from the sun. There is NO observable, runaway greenhouse effect on Venus at 1 bar, ... ONLY a factor of temperature increase related to the ratio of solar distances.

If there were a CO2 greenhouse effect at 1 bar in Venus' atmosphere, then a person would expect to see a much higher temperature at this pressure. Not until we descend to the crushing depths of Venus' atmosphere, however, do we see the extremely higher temperature. There is NOT such a pressure comparison point on Earth, because the pressure at Earth's surface is ninety-some bars LESS than on Venus.

Again, let me repeat it another way for clarification:

At 1 bar pressure on Earth, we observe a physical quantity that we can measure - an average Earth temperature. At 1 bar pressure on Venus, we observe another physical quantity that we can measure - an average higher Venus temperature. We ask, "Why is the temperature at 1 bar pressure on Venus higher than the temperature at 1 bar pressure on Earth?"

The temperature difference in these equivalent pressure zones is about 17%. Venus has a 17% higher temperature at 1 bar pressure than Earth has at 1 bar pressure. Logic dictates that a 300,000 times greater CO2 atmosphere would produce more than a 17% temperature difference at the same pressure, IF a CO2 "greenhouse effect" were operating . But the temperature difference we DO see is something quite at odds with the idea of a CO2 "greenhouse effect".

What Venus' 300,000 times greater CO2 atmosphere DOES do, physically, measurably, is to increase the MASS and DENSITY of Venus' atmosphere. This mass/density increase, thereby, increases Venus' atmospheric PRESSURE tremendously. The huge pressure at the surface is where we observe the high Venusian temperature. At 1 bar pressure, we do NOT observe the high Venusian temperature; we observe ONLY about a 17% difference from Earth temperature at this 1 bar pressure zone of Venus.

Now the supposed "slowing down" of cooling caused by the supposed CO2 "greenhouse effect", even if this properly expressed the mechanism, would imply that the "slow down" somehow causes an INCREASE.

Let me repeat. The most popular version of the CO2 "greenhouse effect" now claims that a "slow down" of cooling is equivalent to an increase in temperature.

What does "slowing down cooling" really mean? It means HOW heat moves, NOT how much heat is statically trapped in any isolated layer.

It means how HIGH up in the atmosphere heat radiation occurs into outer space. The heat still rises from the surface. Even if the level at which heat radiates into outer space moves upward a bit, still there is convection, evaporation, and condensation, and these speed up TOO.

There is NO excessive build-up of heat that amounts to a higher temperature, because the speed of cooling in the radiation portion of the process affects the speed of cooling in the thermodynamic portion of the process. I like the analogy of a pot of boiling water, where adding more heat does NOT increase the temperature, ONLY the speed of heat transfer. No matter how much heat you continue to add to the pot, the water does NOT get hotter - it only boils faster to move the heat. Earth's atmosphere very roughly might be compared to something like this.

When these clear facts cannot stand in the face of reasoning, then what reaction remains other than incredulity?

Doc, beginning your own response just saying outright that I am "wrong" is no different, really, than my supposed "incredulity". Such a blunt statement initiating your reply shows your own incredulity, in a slightly cooler style.

We could go on at this exchange indefinitely, but I honestly do not have the time. I could dissect each and every point you make, but, again, I do not have the time. A scenario similar to ours has been played out many times before in many forums across the internet, with far better savvy, in some cases, than either of us are capable of achieving.

The fact that such a scenario of conflicting words CAN be repeated so many times seems to support the greater truth that there is legitimate disagreement,.. and legitimately two EQUALLY credible sides to an often ONE-sided presentation of a popular idea.

As you did with me in one of MY hubs, I will leave the final word with you. The only thing you have convinced me of is that you know well where you stand, as do I.

Again, thanks for playing.

Robert G. Kernodle


Doc Snow profile image

Doc Snow 3 years ago from Atlanta metropolitan area, GA, USA Author

"Why would a person display incredulity, unless reasoning were so confused, and physical facts were so ignored, by so many, for so long?"

The point isn't the emotion--the point is the failure to supply a substantive reason to support the incredulity. You simply say that you don't believe the greenhouse effect can be responsible for Venusian temperatures and move on--despite the fact that some very, very fine scientific minds thought quite differently, and had the math to prove it.

"In my view, you still try to complicate a very basic, physical, real, known relationship, which is: At equal pressures on BOTH Venus and Earth, the difference in temperature can be accounted for ONLY by the ratio of the two planet's distances from the sun."

I wonder if you really mean "accounted for by ONLY the ratio..." It would make more sense, since your claim seems to be that the correspondence you note is *adequately* accounted for by the two named variables, not *uniquely* accounted for by them.

At any rate, I find it odd that you place so much weight on this correspondence. After all, while total insolation at the top of the Venusian atmosphere does follow the relationship you give, the 1 bar level is still something like 30 kilometers below the tops of those opaque sulfuric acid clouds, and I very much doubt that there's much sunlight at all! Yet it's still hotter than 1 bar on Earth.

"Even if the level at which heat radiates into outer space moves upward a bit, still there is convection, evaporation, and condensation, and these speed up TOO."

Oh, really? Do you have some basis for this claim? I know of none, except that evaporation at the surface should increase with warming--and in fact is observed to do so.

As to the analogy of the boiling water, it seems singularly misguided: what is the 'clamp' on temperature in the Earth system that's comparable to the phase change of the water in the pot?

"Doc, beginning your own response just saying outright that I am "wrong" is no different, really, than my supposed "incredulity". Such a blunt statement initiating your reply shows your own incredulity, in a slightly cooler style."

True. But I promised to back up that statement with solid reasons, and attempted to do so. (I rambled much more than I should, but some of the science is just so fascinating! One drawback of being me...)

Well, if you are out of time to 'play,' then I must follow your lead, and thank you in turn. I'll add that although you've been blunt at times (as have I), you've done a nice job of remaining courteous (as, I hope, have I.) That doesn't always happen in these dialogues, and I appreciate it.

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