Anti-greenhouse effect
The anti-greenhouse effect is a process that occurs when energy from a celestial object's sun is absorbed or scattered by the object's upper atmosphere, preventing that energy from reaching the surface, which results in surface cooling – the opposite of the greenhouse effect.
[3][4] It has been suggested that Earth potentially had a similar haze in the Archean eon, causing an anti-greenhouse effect.
[5] Other atmospheric phenomena besides organic hazes act similarly to the anti-greenhouse effect, such as Earth's stratospheric ozone layer[4] and thermosphere,[3][4] particles formed and emitted from volcanoes,[6] nuclear fallout,[3][6] and dust in Mars's upper atmosphere.
[6] Outside of the Solar system, calculations of the impact of these hazes on the thermal structure of exoplanets have been conducted.
In the most extreme case, suppose that a planet's upper atmosphere contained a haze that absorbed all sunlight which was not reflected back to space, but at the same time was nearly transparent to infrared longwave radiation.
By Kirchhoff's law, since the haze is not a good absorber of infrared radiation, the haze will also not be a good emitter of infrared radiation and will emit a small amount in this part of the spectrum both out to space and towards the planet's surface.
By the Stefan–Boltzmann law, the planet emits energy directly proportional to the fourth power of surface temperature.
Since the haze is not a good absorber of this longwave radiation, it can be assumed to all pass through out to space.
The incoming solar flux is divided by four to account for time and spatial averaging over the entire planet and the
Earlier discussions in the scientific community pre-dating the current definition established by Dr. Christopher McKay in 1991 referred to the anti-greenhouse effect as a precursor to the Late Precambrian glaciation, describing it more as a carbon sequestration process.
[9] This is no longer the current usage of the term, which emphasizes surface cooling due to high-altitude absorption of solar radiation.
The negative greenhouse effect is a phenomenon that can produce localized, rather than planetary, cooling.
[3][12] In the ideal anti-greenhouse case described above, the maximum impact of the organic haze on Titan is (1-0.84)
These methane-derived polymers can be made of polycyclic aromatic hydrocarbons (PAHs) and polyacetylene.
[3] Additionally, the presence of this organic haze is the cause of the temperature inversion in Titan's stratosphere.
[4] The presence of an organic haze in Earth's Archean atmosphere was first suggested in 1983 and could have been responsible for an anti-greenhouse effect.
[14][15] This hypothesis stems from attempts at resolving the faint young Sun paradox, where a reduced solar output in the past must be reconciled with the existence of liquid water on Earth at that time.
[14][15] It is posited that the organic haze allowed the creation of a negative feedback loop to stabilize the climate on Archean Earth.
This would lead to a higher methane to carbon dioxide ratio and would stimulate the production of the organic haze.
One estimation of the anti-greenhouse effect on Archean Earth calculated the impact to be up to about 20 K in surface cooling.
It has been suggested that stratospheric ozone and Earth's thermosphere create a partial anti-greenhouse effect due to their low thermal opacity and high temperatures.
[19] All of these sources act to create a temperature structure where a hot upper layer lies above a cold surface, which typifies the anti-greenhouse effect.
There has been discussion about a weak anti-greenhouse effect on Mars, where storms carry dust into the upper atmosphere.
Evidence for this effect came from Viking 1 measurements made in 1976–77 when in the aftermath of a global storm, the average daytime temperature above the ground dropped by 5 degrees Celsius.
[6] Studies using computer simulations have investigated the impact of photochemical hazes on exoplanets' thermal structure.
Applying this model to hot Jupiters, scientists found that the inclusion of haze for HD 189733 b led to an expansion of the atmosphere, helping to explain an observed steep transit signature in the electromagnetic spectrum.
