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Comments for RealClimate



Climate science from climate scientists...



Last Build Date: Sat, 24 Sep 2016 22:51:51 +0000

 



Comment on Can a blanket violate the second law of thermodynamics? by Barton Paul Levenson

Sat, 24 Sep 2016 22:51:51 +0000

Silk 78: Let’s be clear here. There is no “radiation from the atmosphere”, in that the atmosphere isn’t /generating/ radiation. BPL: Yes it is. The atmosphere is at nonzero temperature and positive emissivity; therefore it radiates, like any other physical body.



Comment on Why correlations of CO2 and Temperature over ice age cycles don’t define climate sensitivity by Simon Edmonds

Sat, 24 Sep 2016 22:50:01 +0000

The is our initial source of heat, but is their another source of heat that has not been taken into account? and if it has, ok. What i'am talking about is that when we use fossil fuels we release GHG's but also generate heat which escapes to the atmosphere, think of a car engine or an airconditioner for example. Has this been taken into effect? Simon.



Comment on Can a blanket violate the second law of thermodynamics? by Barton Paul Levenson

Sat, 24 Sep 2016 22:49:22 +0000

Mack 75: …. ” Joseph Fourier first calculated it in 1824. It’s basic earth science based on the amount of sunlight reaching the top of the earth’s atmosphere (1350 w/sq.m.)…” Hang on Jim, if you look at Trenberth’s Earth Energy Budget diagram, he shows 342w/sq.m. solar radiation arriving at the top of the earth’s atmosphere. BPL: The Earth receives sunlight on its cross-sectional area, π R^2. But its total surface area is that of a sphere, 4 π R^2. So the amount at top of atmosphere, per unit area, is the Solar constant divided by 4. For the latest TSI figure, 1361.5 W m^-2 (Kopp and Lean 2011), the TOA insolation is then 340.375 W m^-2.



Comment on Why correlations of CO2 and Temperature over ice age cycles don’t define climate sensitivity by Scott Denning

Sat, 24 Sep 2016 22:30:11 +0000

A very common way to *miscommunicate* this subject is to conflate "climate sensitivity to CO2" with "climate sensitivity to radiative forcing." In the scientific literature, the jargon is often used interchangeable with an implicit understanding that 2xCO2 = 3.7 W/m2 of RF. But this distinction is often lost on even well-informed lay readers, so it's very easy for the discussion to go off the rails pretty badly. As Eric pointed out in #4, the key is to estimate *all* radiative forcing. So for example deglaciation warmed global mean temps by about 5 C over 10k years with a radiative forcing of about 6.5 W/m2 (total of both GHG increases and albedo decreases). This leads to a calculated climate sensitivity *to radiation* of about 0.77 C/(W/m2). Converting this to climate sensitivity *to CO2* we get [3.7 W/m2 RF per 2xCO2] * [0.77 C per W/m2 of RF] = 2.85 C per 2xCO2, which is right in line with other estimates from both paleo and modeling studies. As Gavin points out in this post, there are also subtleties involving different feedbacks operating over dramatically different time scales (clouds & water vapor over 1 year vs ice sheets & carbon cycle over millennia). Also, the onset of glaciation or deglaciation appears to be triggered by orbital effects that have big seasonal/regional impacts but apply almost zero RF in the global mean. Sorting out forcing from feedback from response in this case therefore involves some semantic parsing. It's no wonder people get wrapped around the axle on this subject!



Comment on Can a blanket violate the second law of thermodynamics? by Jim Eager

Sat, 24 Sep 2016 21:29:24 +0000

Ray, to be charitable it may just be a case of Mack's failure to take into account simple geometry. I used to frequently run into a similar failure over Gigatonnes of carbon vs carbon dioxide. Even when I explained the difference (atomic weight of 12 vs 44) I was more often than not met with undeterred incredulity. We'll see if Mack gets it eventually, or if he really does think generations of scientists could have gotten it that wrong for this long.



Comment on Why correlations of CO2 and Temperature over ice age cycles don’t define climate sensitivity by Eric Steig

Sat, 24 Sep 2016 21:26:35 +0000

See also my old RealClimate post on the subject, here:

http://www.realclimate.org/index.php/archives/2007/04/the-lag-between-temp-and-co2

As I explained, you *can* get at climate sensitivity with the ice core record, but only by taking into account all the forcing (including, in particular, the ice sheet albedo). When you do that, you get essentially the same answer as the standard IPCC sensitivity. Claude Lorius, Jim Hansen, and others, all had this figured out more than two decades ago.




Comment on Can a blanket violate the second law of thermodynamics? by Jim Eager

Sat, 24 Sep 2016 21:02:56 +0000

Mack, you obviously missed this part of what I wrote, or had no idea what it means: "earth’s cross section area integrated over earth’s surface area." Solar insolation is 1350 w/m^2 (actually more like 1368) at top of atmosphere spread evenly over earth's projected cross sectional area. Now spread that 1368 w/m^2 over earth's surface area by dividing by 4. Since earth's surface is curved, the top of earth's atmosphere is also curved, with insolation at maximum at the equator, falling toward zero at the poles where sunlight is tangent to both the surface and atmosphere, the average being 342/m^2. So your perceived conflict evaporates.



Comment on Can a blanket violate the second law of thermodynamics? by Vendicar Decarian

Sat, 24 Sep 2016 20:51:22 +0000

80 - "An educated citizenry is a vital requisite for our survival as a free people " This is why Libertarian organizations like the Koch (Cato) institute, Competitive Enterprise Institute, the Heritage foundation, the American Enterprise institute have worked for years to abolish public schools and public Libraries. Public Libraries you see, are "places of wholesale theft" of intellectual property.



Comment on Can a blanket violate the second law of thermodynamics? by Radge Havers

Sat, 24 Sep 2016 20:49:41 +0000

On Nye, "I do not know why..." Maybe there can be a down side to Dancing with the Stars.



Comment on Can a blanket violate the second law of thermodynamics? by Vendicar Decarian

Sat, 24 Sep 2016 20:46:14 +0000

53 - "doesn’t color correspond to emissivity?" Only for a perfect radiator (black body) Most solids don't have an emissivity that differs much from a black body.