Talk:Greenhouse effect

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Real Greenhouses and Real Atmospheres[edit]

Convection and conduction can only transfer heat from a hotter place to a colder one, so by definition, since a greenhouse is hotter on the inside than it is on the outside, heat will always flow from the inside to the outside, cooling it off instead of heating it up -- the exact opposite of what the greenhouse effect is supposed to do. Long-wave radiation given off by the warm Earth is absorbed by water vapor, clouds, and carbon dioxide in the atmosphere. The trapping of ground radiation (heat) by the Earth's atmosphere is called the greenhouse effect. In a greenhouse, glass takes the place of the water vapor and carbon dioxide. The sun's short-wave rays pass through the glass roof, but the glass will not permit the long waves to escape. As an example of the atmosphere's greenhouse effect, the temperature does not drop as much on a cloudy night as it does on a clear night. — Preceding unsigned comment added by 72.54.91.26 (talk) 17:26, 17 December 2018 (UTC)

In other words, it is physically impossible for real greenhouses warm up due to convection or conduction, they can only warm up due to radiation ("by allowing sunlight to warm surfaces"). Warming up is the greenhouse effect; cooling down is not.

So whether it is a real greenhouse or a real atmosphere, the only way for energy to get into either one of them is via radiation, therefore the ONLY role convection or conduction can ever play in the greenhouse effect or in real greenhouses, is by counteracting the greenhouse effect by cooling them off.

This is all elementary thermodynamics and explains why radiation is considered the primary factor for creating a greenhouse effect (the warming effect), and not the other way around, i.e. -- by limiting convection or conduction (limiting the cooling effect).

Case in point, Standford engineers invented a coating to help cool buildings, and the way in which this coating worked was presented in a peer reviewed science journal using a miniature real greenhouse, i.e. -- a "rooftop apparatus" in which convection and conduction were minimized using polystyrene and an enclosed container. This setup was very much like the Wood's Experiment, only the Stanford experiment was properly conducted under rigorous scientific conditions and clearly eliminated any unknown variables that the Wood's experiment did not. The thing to note about this peer reviewed scientific experiment is that without any convection or conduction, THE TEMPERATURE NOT ONLY DID NOT RISE, IT EVEN COOLED TEN DEGREES BELOW AMBIENT. This proves that limiting convection does cannot create or cause the greenhouse effect, but that convection is just merely undesirable effect, detrimental to the greenhouse effect, with RADIATION BEING THE PRIMARY CAUSE OF THE GREENHOUSE EFFECT, both in real greenhouses and in the real atmospheres.

Just like a perfectly built real greenhouse, the real Earth cannot gain or lose heat by convection or conduction, it can only gain or lose heat by radiation. An imperfectly or improperly built real greenhouse can lose excessive heat by way convection or conduction, but that only counteracts the greenhouse effect, it does not contribute to it in any way, shape, or form.

References:

[1] Heat Transfer. Wikipedia. https://en.wikipedia.org/wiki/Heat_transfer

[2] Second Law of Thermodynamics. "Heat always flows spontaneously from hotter to colder bodies, and never the reverse, unless external work is performed on the system". Wikipedia, https://en.wikipedia.org/wiki/Second_law_of_thermodynamics

[3] Aswath Raman et al (2014). Passive radiative cooling below ambient air temperature under direct sunlight. NATURE, VOL 515, 27 NOV 2014, http://www.nature.com/nature/journal/v515/n7528/full/nature13883.html

writing[edit]

The section on the mechanism does a particularly bad job at explaining how it works. Completely incoherent writing style. Does a poor job at informing the public on such an important topic. — Preceding unsigned comment added by Chrimas1 (talkcontribs) 12:33, 5 March 2019 (UTC)

see WP:SOFIXIT NewsAndEventsGuy (talk) 12:56, 5 March 2019 (UTC)

Basic Error in Attribution of Source of Back Radiation[edit]

The statement in the article

″The atmosphere near the surface is largely opaque to thermal radiation (with important exceptions for "window" bands), and most heat loss from the surface is by sensible heat and latent heat transport. Radiative energy losses become increasingly important higher in the atmosphere, largely because of the decreasing concentration of water vapor, an important greenhouse gas.″

This makes a common, but incorrect assumption that the thermal energy from radiative absorption, sensible heat and latent heat can be separated once they are absorbed. In fact thermal emission results from the temperature of the part of the atmosphere that emits and this is a function of the total amount of thermal energy in the emitting volume. An analogy is that if there are three sources of black jelly beans being put in a jar, and one of them pulls beans out, how can you tell what the original source was.

There is an interesting point buried in the current statement, which is low in the atmosphere the amount of thermal energy from surface radiation is very high. This decreases with altitude, but at the same time the amount of thermal radiation received from greenhouse molecules increases (but so does that from sensible and latent heat, the later being very altitude/temperature dependent)

Untangling this is going to require some careful wordsmithing

Joshua Halpern (talk) 16:27, 4 April 2019 (UTC)

Ok, please take care to ensure that any changes you propose are verifiable from cited reliable sources. Thanks, . dave souza, talk 16:55, 4 April 2019 (UTC)

Semi-protected edit request on 10 April 2019[edit]

On the third line of the article the phrase is: "If a planet's atmosphere contains radiatively active gases (i.e., greenhouse gases) they will radiate energy in all directions."

The word "radiatively" was misspelled and it should be "radioactively". Viniciusnmelo (talk) 09:59, 10 April 2019 (UTC)

Thanks, this points up wording which isn't very explanatory. Radiatively is used to mean the property of greenhouse gases; that they absorb and emit radiant energy within the thermal infrared range. Think that could be phased more informatively. However, it's not the same as radioactive. . . dave souza, talk 10:22, 10 April 2019 (UTC)

Semi-protected edit request on 20 May 2019[edit]

An ideal thermally conductive blackbody at the same distance from the Sun as Earth would have a temperature of about 5.3 °C (41.5 °F). However, because Earth reflects about 30%[12][13] of the incoming sunlight, this idealized planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C (0 °F).[14][15] The surface temperature of this hypothetical planet is 33 °C (59 °F) below Earth's actual surface temperature of approximately 14 °C (57 °F).[16]

should read, due to incorrect conversion.

An ideal thermally conductive blackbody at the same distance from the Sun as Earth would have a temperature of about 5.3 °C (41.5 °F). However, because Earth reflects about 30%[12][13] of the incoming sunlight, this idealized planet's effective temperature (the temperature of a blackbody that would emit the same amount of radiation) would be about −18 °C (0 °F).[14][15] The surface temperature of this hypothetical planet is 15 °C (59 °F) above Earth's actual surface temperature of approximately 14 °C (57 °F).[16]

2600:8804:4900:6A:6C92:7828:5960:AD41 (talk) 00:34, 21 May 2019 (UTC)

How is a 15 C interval the same as a 59 F interval? Since we're talking about a difference in temperature (number of degrees), you don't adjust for the difference in freezing point. Guettarda (talk) 03:08, 21 May 2019 (UTC)