Greenhouse Analogy

The Greenhouse Analogy

If Earth’s atmosphere were like a greenhouse, calculations involving temperature would be trivial. However, Earth’s atmosphere is nothing like a greenhouse. There is no valid analogy between Earth’s atmosphere and a greenhouse. Greenhouses are, by design, containers closed to airflow that allow solar energy in. Gas percentages have no significant effect on the function of a greenhouse. Greenhouses warm up due to a lack of airflow, not gas percentages. Yet, if higher specific heat gases replaced air in a greenhouse, the greenhouse would warm slower in the morning and then cool off slower in the evening- nothing profound, magic, or new about that. It would be tricky to measure any difference.

Unlike a greenhouse, in Earth’s open atmosphere, hot gases are never trapped. The atmosphere is an open container without ceiling or walls. Convection always moves hot gases away from Earth’s surface to high atmospheric levels. If there is no cloud cover, radiant heat ejected from Earth’s surface, more often than not, passes straight through the atmosphere to space. Heat absorbed at Earth’s surface of any bandwidth, infrared or otherwise, when re-emitted dissipates primarily away from Earth and mostly to space without ever returning to Earth. The clarity of satellite views of Earth in the infrared demonstrates Earth’s ability to radiate heat through atmospheric gases and directly to space.

For several decades and in a subtle way, the greenhouse gas misnomer has been woven into the various technical disciplines like a mysticism that few bother to dispute. Texts make mention of “greenhouse gases” as if spreading a rumor but forego any in depth discussion; “… it is true but beyond the scope of this text.” Most everyone seems to default to the expertise of those illusive others.

The temperature history of ancient Earth’s surface has been plotted out based on CO2 proportions using data acquired from rocks of known age and using isotope ratios and has become generally accepted. This may be an accurate (as far as is currently possible) way of plotting CO2 percentages and perhaps is even suggestive of past temperature trends- trends, not absolute temperatures. Any connection via CO2 percentage to actual past surface temperatures is much more elusive- currently impossibly elusive.

If there is a situation of rising surface temperatures, it might be helpful to understand the problem’s cause rather than attributing it to an irrelevant greenhouse scenario.

If one is looking at any past combination of gases to determine absolute temperature, the pressure, equal to some function of gravity and gas volume, must be known (the Ideal Gas Law). Instead of known, an assumed pressure and some median temperature are used; medians roughly equivalent to modern conditions; a baseless approach. In addition, knowing temperature trends does not explain the causes of the temperature trends.

It is more reasonable to establish absolute temperature trends based on Earth’s initial molten temperatures, rates of cooling, and the age of Earth. Rates of cooling are a direct result of Earth’s ability to radiate heat to the near absolute zero temperature of space while gaining some heat from the Sun.

Instead, Hadean Earth is assumed molten while all points between Hadean Earth and modern Earth are generally assumed to be some mild median temperature roughly equivalent to modern temperature. This assumption leads one to believe that at during the very high CO2 concentration of the Hadean Eon, Earth cooled dramatically- completely contrary to global warming claims- it cannot work both ways.

Earth’s Refrigerant

There is another overwhelming consideration concerning Earth’s temperature and involving atmospheric pressure levels both ancient and modern- namely the refrigerant properties of water. Although not to levels some think necessary for Noah’s flood, Earth has been covered by water since before first sunlight- a completely reasonable and very well supported claim. Because of extremely high pressure, a sea of liquid water existed on a very hot Earth. However, Earth’s pressure has changed dramatically since water first condensed on its surface.

Water is Earth’s most abundantly available refrigerant. Earth is an open refrigerant container with refrigerant trapped by gravity. Currently at globally constant pressure, the refrigerant container that is the Earth System is a nearly isobaric container- certainly in the modern short term. When a refrigerant evaporates off a surface, it cools the surface by removing heat in a predictable way. Total pressure including non-condensable gas pressure is a big factor, while percentages of non-condensable gases are irrelevant. Refrigerant systems are well understood and are completely predictable. Refrigeration computations are common to mechanical engineers- the theoretical and practical application experts on thermodynamics.

A look at Earth’s temperature separate from the influence of a water cycle is available in desert regions such as the Atacama Desert where rainfall is virtually zero. The Atacama Desert demonstrates the effect of minimal cloud cover and minimal rain on Earth’s surface temperature. Deserts demonstrate the absence of refrigerant- the absence of water. Desert temperatures are extreme in the course of each day but daily averages are typical for their latitude.

Water offers other enhanced temperature stability as well. Cloud cover increases the atmosphere’s reflectivity (albedo) and limits heat gained from the Sun (insolation) effectively throttling the amount of heat at Earth’s surface. As surface conditions cool, cloud cover diminishes and a range of temperatures becomes typical for a particular season and in a particular region- in a simplified view at least. Wind currents add complications leaving some areas typically cool and others typically hot.

Note that cloud cover is not a gas. Cloud cover is made of miniscule droplets of liquid water. Cloud cover cycles cooled and condensed refrigerant back to Earth’s surface in the form of rain where it removes heat and re-evaporates into cloud cover- an endless cycle that is subject only to atmospheric pressure and heat from the Sun- not gas percentages. Unlike gases, clouds reflect some radiant heat back to Earth’s surface. Without cloud cover, dew freezes on the ground on mildly cool nights. Like a sort of mechanical governor, cloud cover reduces Earth’s nighttime exposure to the near absolute zero temperatures of space and reduces heat from sunlight in the daytime. Cloud cover offers stability not available in desert regions- a Control Theory problem.

In the big picture, Earth’s atmosphere is a heat pump driven by solar energy. The atmosphere and the frozen regions are the heat pump’s condenser. The surface of Earth is the heat pump’s evaporator. We all live inside a refrigeration system and on the inside surface of its evaporator.

As with any refrigeration system, the presence of non-condensable gases adds a complication. Non-condensable gases are those that do not exist in both liquid and gas states within Earth’s temperature and pressure range. There are several non-condensable atmospheric gases such as nitrogen, oxygen, and CO2 contaminating Earth’s heat pump system. Water is the only atmospheric gas operating in its refrigerant range.

Any refrigeration technician can explain what happens in a refrigeration system when non-condensable gases are present in the system. Because of the system’s added partial pressures, evaporating temperatures go up as do condensing temperatures. In the Earth System, the added partial pressures of non-condensable gases makes Earth’s surface warmer than it would be without them; take some of the pressure away and Earth becomes a deep freeze.

Operating pressure has a direct effect on any refrigerant’s evaporating temperature and the evaporating temperature of water has a direct effect on Earth’s surface temperature. If CO2 is a culprit gas in any true global warming scenario, it is because its added partial pressure is driving atmospheric pressure up. I cannot find any indication that global atmospheric pressure is anything but constant. Is anybody checking? Do not confuse global pressure with local pressure variations that local weather quickly corrects.

If gas percentages made a significant difference in heat gains, then an entrepreneur might push it to an extreme where the highest specific heat gas available is the only gas in his greenhouse. For instance, the heat gained by using pure CO2 in a greenhouse might allow crop growth in extreme regions year around. Sadly, it will not improve temperatures and is no better than common air.


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