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Originally Posted by Windguy
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Originally Posted by Paradox
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Both Cbacba and I are currently involving ourselves what is the greater forcing, and as Cbacba pointed out solar is 0.8W/m^2, I've pointed out a 2.417W/m^2 for man made GHG's (or termites). But as a 11 year sunspot cycle a 0.2 degree increase and decrease isn't as comparable to the 0.7 degrees as a total so far, what, we've got to decide is do we deny figures out there or do we believe them. But in saying that the IPCC hasn't denied solar forcing, they've just maintained it is not the main forcing, and a thirty year increase definately doesn't fit in the 11 year sunspot cycle.
Don't worry I still believe in the potential for an ice age, but it will be brought on by GW as in, Greenland melting, lowering the saltiness of the ocean, slowing down the thermohaline cycle, snap freezing europe then changing the albedo affect towards more reflection. So be the same if a massive iceberg snaps off and doesn't melt and ends up near the equator creating a cooling spot, lowering albedo etc.. But the flip side of massive rising ocean levels lowering albedo, creating more heat, rising more ocean levels again and changing the storms into superstorms is just as bad a prediction as the other two show we really need to halt the ocean temperatures from rising anymore, and so far the only way to do that is minimise man made GHG production, as we can't block the sun. |
Windg,
I've applied the hitran output to another calculation. It too is quite interesting.
As mentioned previously, Only about 55W/m^2 exit the atmosphere from the surface and 230W/m^2 are absorbed. The number would be more except that the 62% (K&T) cloud cover blocks most of it.
By taking into careful account the numbers for absorption and insolation and cloud cover and doing an energy balance calculation between surface atmosphere and space in equilibrium conditions, I was able to get valid temperatures for mean atmosphere and mean earth. By varying the absorption by 1W/m^2, I was able to get a second value to establish a delta T over delta F just based on the energy budget. (originally, I had started doing a curve from 0 to future values but the assumptions were a bit too far from the situation to be of much practical use other than to show the shape of the curve.
On the other hand, this purely thermodynamic model calculation showed actual values right on the money so to say. The delta results for adding 1 W/m^2 absorption came out with the sensitivity results of 0.130 deg K/W/m^2 for the atmosphere and and 0.117 deg K/W/m^2 for the surface.
It was most interesting in that the sensitivity is dependent upon cloud cover and that more cloud cover reduces the sensitivity for the same amount of added GHG absorption.
It's interesting to note that the surface sensitivity is less than my upper limit estimate based on the mathematical nature of the curve and the chord from 0 absorption and temperature rise to the 'now' values for those. This is the one that uses the real atmospheric change so contains all the currently active feedback mechanism at play.
Net result is that according to this analysis, earth's temperature has risen by 0.187 deg K since 1750 due to co2,and your 2.5W/m^2 ghg rise has contributed to a total of just under 0.3 deg K, leaving 0.4deg K unaccounted for by ghgs.
Also, a doubling of co2 from 1750 leads to a result of 0.42 deg K rise in temperature. The 2.5W/m^2 increase also leads to a rise of 0.325 deg K. in mean atmospheric temperature since 1750.
The mechanism is actually quite fascinating. It seems that by blocking a bit more of the surface radiation, the atmosphere as seen from space must increase by a bit to compensate for the lost amount. This lost amount is not the full amount of the forcing change but is rather reduced by the fraction of clouds in the sky. It seems the clouds are already blocking the emissions where present. The total energy going into the atmosphere also goes up by the difference between what was going out and what is going out after the increase. The outgoing into space balances what the sun is bringing in, no more, no less (for equilibrium). The atmosphere as viewed from space then increases to accomodate the change in energy lost from the surface radiation which is again, a fraction of the total, depending upon overall cloud cover.
The mean atmospheric temperature (in the simplified model) is the average. It can be ascertained by taking the new TOA viewed temperature and averaging with the bottom of atmosphere temperature - as seen from earth looking up. This bottom temperature can also be calculated based on the low side energy budget which includes that solar radiation that makes it through the atmosphere to the surface. The low side of the atmosphere radiates down the amount of energy according to its apparent temperature and the surface radiates upward based upon its own temperature. These (and the incoming and outgoing energy) form the balance for that as well.
Changing the balance - by adding some ghg forcing - results in minor increases in the surface temperature and slightly larger increases in the atmosphere. The net radiation doesn't change leaving earth but rather shifts more towards the upper atmosphere and away from the surface emitted radiation. The slightly hotter atmosphere means the surface has to warm slightly to reach radiaton balance but not quite as much as the mean atmospheric temperature rises.
In this system, it appears that to achieve a 1 degree rise in temperature due to co2, it would seem that we would need over 2 doublings of co2 from present levels (actually about 2.4x to gain 8.3W/m^2 increase in forcing ghgs).
Unlike my chord estimate, based upon an upper limit to the actual atmospheric response including all active feedbacks, this model doesn't have any positive or negative feedbacks in it. We do know from the chord estimate, that the value must be less than the chord, (which is not even twice the value of these sensitivities). Also, as stated numerous times before, there is not such thing as a positive net feedback forcing as such a thing completely unstable and would feed on itself (would have fed on itself long ago) with the first infinitesimal variation in values and moved the planete to some stable state, presumably much hotter, like boiling ocean hot or something that you might notice is not the case. Instead, the feedbacks will undoubtedly be net negative, and will tend to reduce these sensitivities even further by some small amount.
It does make for the interesting question of just what is causing the majority of of the warming we've seen as it's not any GHGs associated with man. Note too that since there is about 0.4 deg K warming occurring from some other source, it then becomes questionable as to whether the co2 is actually being caused by man or is in fact itself a consequence of the warming, further slightly enhancing the warming effect.
One interesting notion is since we are well on our way to a magnetic field flip, is there possibly something going on underneath our feet that is increasing the thermal release from below the earth's surface. It's not really the sort of number we can readily put measurement to. Since the deep oceans are where the crust is thinnest, and since most of that region has virtually never been explored other than some minimal mapping efforts, it would seem plausible that it might not be as well understood or measured as some might think.
Linear Mode
