CC3 -- Why I believe that a third option is needed for climate change

posidonia wrote: »

Humm, so what N&Z are saying that that they have discovered a 57C atmosphere temperature error no one else has ever noticed, and for over more than a century. Not 1C, not a few C, 57C!



They must be kidding, or trolling...

Gaoth Laidir wrote: »

That seems to be what they're saying, yes. Is their method wrong? Please explain how.

Thargor wrote: »

https://en.wikipedia.org/wiki/Gish_gallop

Even if he were to spend hours of his time disproving it you'll just be back copying and pasting some other gibberish argument from spurious sources after a quick Google that backs up your prejudices an hour later.

Do you have no sense of scale when it comes to evidence? There is no 57 deg C temperature error undiscovered all this time and missed by literally millions of researchers except these nobodies, its moronic.

Thargor wrote: »

Yeah its debate alright, an extremely low form of debate favoured by anti-vaxxers, flate-earthers and climate change deniers, my totally irrelevant Wikipedia link explains its purpose.

posidonia wrote: »

You, (seriously?), think there could be a 57C hole in our understanding of the atmosphere?

posidonia wrote: »

You don't see anything ELSE glaringly wrong you mean


What's wrong with the paper? That they claim a 57C error isn't damning enough then? That can be overlooked because there isn't anything 'glaringly' wrong?



Hummmm.....

Thargor wrote: »

Ive honestly wasted enough time on it at this stage.

Gaoth Laidir wrote: »

You didn't waste any time at all on it by the looks of it.

M.T. Cranium wrote: »

I can accept that their estimate is correct for the Moon but their assumption that an airless earth would achieve a similar mean temperature (of a very thin atmosphere as the Moon possesses, which of course is a physical impossibility for a body with our gravitational pull, even Mars retains considerably more of an atmosphere than the Moon has) seems flawed to me. They obtain a similar albedo to the lunar regolith (around .13) but in any case, this is all rather pointless speculation since we are only concerned in this debate about how much the 19th to early 20th century atmosphere (which may have had a global average temperature of 14 C) could warm up under various assumptions of added greenhouse gases.

But as an isolated proposition, the 57 deg differential rests on whether or not you can accept that an airless earth would achieve the same mean temperature as the slower-rotating Moon. Had the earth always been airless it would not have had oceans at any point, but a suddenly airless earth would have vast frozen surfaces. These are probably considerations outside the investigative focus of the authors. I can't imagine conditions on an airless earth and I think it is rather pointless to imagine them, so the 57 deg difference between two impossible situations is the ultimate example of angels dancing on pins.

I should add that even with a weak atmosphere of less than 1 mb, Mars has stabilized at a higher temperature than they estimate for the earth. Temperatures of -77 C might occur in polar nights on Mars (as they do in Antarctica) but mean planetary temperatures on Mars are around -25 C, I think the authors were accused of changing that variable in their model but I don't see where they quote anything much lower than that. Thus for whatever implausible reason they seem to be saying that an airless earth could be colder than Mars. That makes no sense to me.

A tenuous atmosphere, on the other hand, is one that has not had a measurable influence on the surface albedo and regolith thermo-physical properties and is completely transparent to shortwave radiation. The need for such delineation of atmospheric masses when calculating Tna arises from the fact that Eq. (10a) accurately describes RATEs of planetary bodies with tangible atmospheres over a widerange of conditions without explicitly accounting for the observed large differences in albedos (i.e. from 0.235 to 0.90) while assuming constant values of αe and ηe for the airless equivalent of these bodies. One possible explanation for this counterintuitive empirical result is that atmospheric pressure alters the planetary albedo and heat storage properties of the surface in a way that transforms these parameters from independent controllers of the global temperature in airless bodies to intrinsic byproducts of the climate system itself in worlds with appreciable atmospheres. In other words, once atmospheric pressure rises above a certain level, the effects of albedo and ground heat storage on GMAT become implicitly accounted for by Eq. (11). Although this hypothesis requires a further investigation beyond the scope of the present study, one finds an initial support for it in the observation that, according to data in Table 2, GMATs of bodies with tangible atmospheres do not show a physically meaningful relationship with the amounts of absorbed shortwave radiation determined by albedos. Our discovery for the need to utilize different albedos and heat storage coefficients between airless worlds and worlds with tangible atmospheres is not unique as a methodological approach. In many areas of science and engineering, it is sometime necessary to use disparate model parameterizations to successfully describe different aspects of the same phenomenon. An example is the distinction made in fluid mechanics between laminarand turbulent flow, where the non-dimensional Reynold’s number is employed to separate the two regimes that are subjected to different mathematical treatments.

We do not currently have sufficient data to precisely define the limitbetween tangible and tenuous atmospheres in terms of total pressure forthe purpose of this model. However, considering that an atmosphericpressure of 1.0 Pa on Pluto causes the formation of layered haze [93],we surmise that this limit likely lies significantly below 1.0 Pa. In thisstudy, we use 0.01 Pa as a tentative threshold value. Thus, in the contextof Eq. (10b), we recommend computing Tna from Eq. (4c) if P > 10^-2 Pa,and from Eq. (4a) (or Eq. 4b, respectively) using observed values of αeand ηe if P ≤ 10^-2 Pa. Equation (4a) should also be employed in cases,where a significant geothermal flux exists such as on the Galilean moonsof Jupiter due to tidal heating, and/or if S ≤ 0.15 W m-2. Hence, the 30-year mean global equilibrium surface temperature of rocky planets depends in general on five factors: TOA stellar irradiance (S), a reference airless surface albedo (αe), a reference airless ground heat storage fraction (ηe), the average geothermal flux reaching the surface (Rg), and the totalsurface atmospheric pressure (P). For planets with tangible atmospheres(P > 10-2 Pa) and a negligible geothermal heating of the surface (Rg ≈ 0), the equilibrium GMAT becomes only a function of two factors: S and P, i.e. Τs = 32.44 S0.25 Eα(P). The final model (Eq. 10b) can also be castin terms of Ts as a function of a planet’s distance to the Sun (rau, AU) by replacing S in Equations (4a), (4b) or (4c) with 1360.9 rau-2.

Although Mars is the third most studied planetary body in theSolar System after Earth and the Moon, there is currently no consensus among researchers regarding its mean global surface temperature (TM). TM values reported over the past 15 years span a range of 40 K. Examples of disparate GMATs quoted for the Red Planet include 200 K [79], 202K [82,130], 210 K [32], 214 K [80], 215 K [6,81], 218 K [77], 220 K [76], 227 K [131] and 240 K [78]. The most frequently cited temperatures fall between 210 K and 220 K. However, a close examination of the available thermal observations reveals a high improbability for any of the above estimates to represent Mars’ true GMAT.

Figure B.1 depicts hourly temperature series measured at 1.5 m above ground by Viking Landers 1 and 2 (VL1 and VL2 respectively) in the late 1970s [60]. The VL1 record covers about half of a Martian year, while the VL2 series extends to nearly 1.6 years. The VL1 temperatureseries captures a summer-fall season on a site located at about 1,500 m below Datum elevation in the subtropics of Mars’ Northern Hemisphere (22.5o N). The arithmetic average of the series is 207.3 K (Fig. B.1a). Since the record lacks data from the cooler winter-spring season, this value is likely higher than the actual mean annual temperature at that location. Furthermore, observations by the Hubble telescope from the mid-1990s indicated that the Red Planet may have cooled somewhat since the time of the Viking mission [132,133]. Because of a thin atmosphere and the absence of significant cloud cover and perceptible water, temperature fluctuations near the surface of Mars are tightly coupled to diurnal, seasonal and latitudinal variations in incident solar radiation. This causes sites located at the same latitude and equivalent altitudes to have similar annual temperature means irrespective of their longitudes [134]. Hence, one could reliably estimate a latitudinal temperature average on Mars using point observations from any elevation by applying an appropriate lapse-rate correction for the average terrain elevation of said latitude. At 22.5o absolute latitude, the average elevation between Northern and Southern Hemisphere on Mars is close to Datum level, i.e. about 1,500 m above the VL1 site. Adjusting the observed 207.3 K temperature average at VL1 to Datum elevation using a typical near-surface Martian lapse rate of -4.3 K km-1 [78] produces ~201 K for the average summer fall temperature at that latitude. Since the mean surface temperature of a sphere is typically lower than its subtropical temperature average, we can safely conclude based on Figure B.1a that Mars’ GMAT is likely below 201 K. The mean temperature at the VL2 site located at ~48o N latitude and 3,000 m below Datum elevation is 191.1 K (Fig. B.1b). The average terrain elevation between Northern and Southern Hemisphere at 48o absolute latitude is about -1,500 m. Upon adjusting the VL2 annual temperature mean to -1,500 m altitude using a lapse rate of-4.3 K km-1 we obtain 184.6 K. Since a planet’s GMAT numerically falls between the mean temperature of the Equator and that of 42o absolute latitude, the above calculations suggest that Mars’ GMAT is likely between 184 K and 201 K.