Klimaforskning - hjemmeside
Startet av Jostemikk, februar 22, 2012, 18:06:08 PM
Sitat fra: Jostemikk på februar 28, 2012, 10:07:58 AMDette er noe alle bør lese.KevinK gir drivhuseffekten en skikkelig rett høyre på bloggen til Roy Spencer.
Sitat fra: Jostemikk på februar 28, 2012, 15:19:05 PMArtig at du nevnte akkurat det, ConTrari! Jeg snakket med noen på telefon i dag, og da fikk jeg samme beskjed. Den jeg snakket med sa KevinK skulle vært lærer!
SitatNullius in Verba says: March 16, 2012 at 1:05 PMmkelly,I think Dr Spencer's two-step is aimed at proving the existence of a greenhouse effect, not explaining its mechanism. So it's sufficient to show that not all the heat radiated from the surface gets to space. If the atmosphere slows the rate of cooling, the temperature must rise.Eschenbach's four steps are a fairly conventional explanation of the mechanism. The trouble is, the last step is incorrect. This is how it would work in a *non-convective* atmosphere, but convection is not simply a minor correction to be applied on the end of the radiative physics. In a convective atmosphere, convection takes over completely, and backradiation – while it exists and is thermally absorbed by the surface – has no *net* effect.We can illustrate the concept with a sunlit pond of water. Let's suppose we can ignore convection and conduction, and the sunlight hitting the bottom of the pond adds heat which can only escape by radiation. We divide the water into layers, each one just thick enough to be totally opaque to thermal IR. The sunlight adds X units of heat, all of which must escape from the top surface of the pond. It radiates X units up, and X units down into the layer below. It's losing 2X units of heat in total, which have to be balanced by input from somewhere, and the only place it can come from is the layer below. So the layer below has to be hotter, and radiates 2X units up and 2X units down into the third layer. The second layer is now losing 4X units, and only receiving X units from above, so must receive 3X units coming up from the layer below. And so on. The 3rd layer emits 3X, the 4th layer emits 4X, and generally the power emitted is proportional to the optical depth. The temperature rises with the 4th root of optical depth.Since the minimally opaque layers in a pond are about 20 microns thick, the pond water provides an imensely strong 'greenhouse' resistance to the escape of heat, and would boil within a few centimetres of the surface. Liquid water constitutes a "super-greenhouse gas".Obviously, it doesn't happen like that. This is because in water convection dominates. As soon as the slightest difference in temperature occurs, the water starts moving and erases it. You cannot get greenhouse warming in a pond, because it is convective. You still get backradiation though. Even with every layer at the same temperature, every 20 micron layer is still emitting X units up and X units down, constituting a huge amount of radiation in every cubic metre. But the net effect of almost all of it is cancelled by the radiation going in the opposite direction. Only radiation from the surface is not cancelled. This is what allows us to generally ignore the radiation going on inside a body, and treat it as if only the outer surfaces emitted.The fundamental equation for the greenhouse effect in a convective atmosphere is T_surf = T_eff + LR * AARTS The surface temperature is the effective radiative temperature plus the lapse rate times the average altitude of emission to space.For a pond of water, the lapse rate is effectively zero, so you get no greenhouse warming. For the stratosphere, the lapse rate is negative, so you get greenhouse cooling. For the planet Venus, the average altitude of emission to space is about 70 km, so the greenhouse warming is huge. For the planet Mars it's about 1 km so the effect is tiny. They all fit in to the same basic pattern.And incidentally, if you suppress convection in a pond of water by setting up a salt-water density gradient, the bottom of the pond can warm to 90 C within a metre or so of the surface. This is not as strong an effect as it would be if radiation was the only heat transport mechanism, but it is in a sense an *actual* example of a radiative greenhouse effect.
Sitat fra: Gordon Robertson says:April 11, 2013 at 5:15 AMHeat can only be transferred from a warmer body to a cooler body through ordinary means. To reverse that process, external energy is required. GHGs in the atmosphere are cooler than the surface, case closed. I know you have argued based on thought experiments that heat can flow from cooler objects to warmer objects. Sorry, you may be a brilliant meteorologist and an expert on AMSU units, but your understanding of thermodynamics is faulty.I';s a no-brainer. Since heat is a measure of the kinetic energy of a gas, which is the degree to which the gas molecules are excited, then transferring that energy to a cooler body requires emitting the warmer energy as infrared and having it absorbed by the cooler molecules. So far so good.When the cooler gases re-emit whatever portion they intercepted, that energy is now at a lower intensity and in a reduced frequency range. How is that energy going to raise the temperature of the surface, as the AGW theory requires?Please don't talk about blankets. That is a naive theory that Craig Bohren has called plain silly. Heat is not trapped by GHGs and the 1% of GHGs in the atmosphere would be the equivalent of having 99 panes of glass removed from a greenhouse with 100 panes.It's not good enough to point a meter ta the sky and claim that as proof of a greenhouse effect. Where are the numbers? I think you pointed out before, with reference to a satellite, that no one has those numbers. Even Trenberth-Kiehle admitted their energy budget is based on a fictitious scenario.So is the Greenhouse Effect Theory, which is based on a crude calculation of the temperature of a planet without an atmosphere and oceans and one with an atmosphere and oceans. It is far too complex to calculate either scenario given the number of parameters required.
Sitat fra: Jostemikk på april 11, 2013, 15:44:40 PMDet er nok ingen god idé at Spencer begynner å bygge girkasser, for det han påstår er jo at hvis man har to like tannhjul koblet sammen, med kraft kun på det ene, vil det andre tannhjulet hvis det blir frikoblet ei god stund og mister rotasjonshastighet, få det kraftdrevne tannhjulet til å gå raskere rundt hvis de kobles sammen igjen.
Sitat fra: Jostemikk på april 11, 2013, 17:47:15 PMHvis jeg ved et slumpetreff klarer produsere noe du har lyst til å bruke, Okular, så er det bare å kaste seg over.