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Comments 1 to 25 out of 173:

1. RW1 at 05:46 AM on 19 December, 2010
   If the cloud feedbacks are indeed positive and inline with the IPCC model predictions of about a 3 C rise in temperature from a doubling of CO2 (a 3.7 W/m^2 gross increase in radiative forcing; 1.85 W/m^2 net), then why doesn’t the same proportional amount of positive feedback amplification lead to 16+ C rise in temperature when the net albedo adjusted incident solar power at perihelion is about 14 W/m^2 higher? Instead, average global temperatures are actually colder at perihelion in January then at aphelion in July. What is so special about 1 W/m^2 of additional power from CO2 that it’s at least 5 times more powerful than 1 W/m^2 of additional power from the Sun?
2. VeryTallGuy at 06:57 AM on 19 December, 2010
   RW1 I've no idea if your figures are correct (reference please?). However the answer to your question is that CO2 adds the heat all the time, year after year (think of a bathtub filling), whereas changes during a year cancel out over longer timescales (think of waves in the bathtub).
3. RW1 at 07:28 AM on 19 December, 2010
   Then how do you explain the relatively large and fast seasonal temperature changes that occur in each hemisphere every year? The seasonal hemispheric fluctuations in radiative forcing that occur are astronomically greater than the measly 1.85 W/m^2 that will come from a doubling of CO2. If what you’re saying is true, we wouldn’t see anywhere near the seasonal variability that occurs each year. (*The peak to peak difference in solar radiance between perihelion and aphelion is about 80 W/m^2. Divide by 4 to get the average of 20 W/m^2, then subtract out the albedo of about 0.3 and you get a net increase of about 14 W/m^2 at perihelion.
4. muoncounter at 07:41 AM on 19 December, 2010
   #3: "difference in solar radiance between perihelion and aphelion" Are you suggesting that seasonal temperature changes are solely due to the difference in sun-earth distance at peri vs. api?
5. RW1 at 07:56 AM on 19 December, 2010
   Here is a summary of where I'm getting my figures: The average incident solar energy is about 340 W/m^2. If you subtract the effect of the earth’s albedo (about 30% or 0.3 = 102 W/m^2), you get a net incident solar energy of about 238 W/m^2 (340 – 102 = 238). (*The albedo is the amount of incoming short wave radiation from the sun that gets reflected back out to space off of clouds, snow, ice, etc., and cannot be absorbed by GHGs or contribute to the greenhouse effect, which is why it’s subtracted out). From this you take the surface power at the current average global temperature of 288K, which is about 390 W/m^2 (from Stefan Boltzman), and with it you can calculate the gain or the amount of surface warming as a result of the greenhouse effect in the atmosphere. To get this you divide the current surface power by the net incident solar power, which comes to about 1.6 (390/238 = 1.6). What this means is that for each 1 W/m^2 of solar input, you get 1.6 W/m^2 of power at the surface due to the presence of GHGs and clouds in the atmosphere – a boost of about 60%. A doubling of CO2 alone absorbs only about 4 W/m^2 of additional power. About half this is directed upward out to space and the other half is directed downward toward the surface, resulting in a net of about 2 W/m^2. If you then multiply this additional 2 W/m^2 of power by the same gain calculated for solar power (as a result of the greenhouse effect), you get an increase in the surface power of about 3.2 W/m^2 from a doubling of CO2 (2 x 1.6 = 3.2). Using Stefan Boltzman, an additional 3.2 W/m^2 will increase the surface temperature only about 0.6 degrees C (390 + 3.2 = 393.2 W/m^2 = 288.6K). This is much less than the 3 degrees C predicted by the IPCC. Even if you assume all of the 4 W/m^2 from a doubling of CO2 goes to the surface, the temperature increase would still only be 1.2 degrees C – significantly less than the low end of the IPCC’s claimed range of 2 – 4.5 C. To get the 3 degrees C claimed by the IPCC, an additional 16 W/m^2 would be needed. This requires a gain of 8 rather than 1.6 (or at least a gain of 4 instead of 1.6 if we assume all of the absorbed power is directed back to the surface). The bottom line is the actual response of atmosphere (from GHGs and clouds) relative to net incident solar power, measured in W/m^2, is far less than the response claimed by the IPCC from a doubling of CO2, which is also measured in W/m^2. A watt/meter squared of heat and power is watt/meter squared of heat and power, independent of where it originates from – whether it’s the Sun, or redirected back to the surface as a result of more CO2 in the atmosphere (*If this was not true, then power from the Sun and additional power from CO2 cannot both be expressed in W/m^2 as they are). Ultimately, the total power flux at the surface is directly tied to temperature via Stefan-Boltzman - there is no escaping this. In short, the surface gain factor of about 1.6 supports an upper limit of only about 0.6 C from a doubling of CO2 because there is no physical or logical reason why a small increase of less than 2 W/m^2 will behave radically differently than the original 99+ percent - i.e. a gain of 8 or more needed for a 3 C rise is simply way outside the bounds of empirically derived observations of how the system responds to changes in radiative forcing.
6. RW1 at 07:57 AM on 19 December, 2010
   muoncounter (RE: 4) "Are you suggesting that seasonal temperature changes are solely due to the difference in sun-earth distance at peri vs. api?" No, not at all.
7. VeryTallGuy at 09:02 AM on 19 December, 2010
   RW1@3 "Then how do you explain the relatively large and fast seasonal temperature changes that occur in each hemisphere every year?" They are the ripples on the bathtub. Effects of external forcing are additive to them. @5 you are putting forward a logical fallacy. The greenhouse effect is made up of forcings (largely CO2) and feedback (largely H2O). The overall effect on the heat balance is the sum of both. Let's put a bizarre analogy together. Celebrities (CO2) are stalked by paparazzi photographers (H2O feedback). Each celebrity attracts 2 paparazzi. With one celeb, how many people are on the pavement - 3 Add one more celeb - by your calculation we only get 4 people, a 33% increase. In reality, of course, we get 6, a 100% increase. And your arbitrary halving of the CO2 effect from 4 to 2 W/m2 is also incorrect.
8. Riccardo at 09:31 AM on 19 December, 2010
   RW1 if you wish to (even roughly) calculate the result of an energy (im)balance you have to do it at the top of the atmosphere (TOA). You can not take two different pieces, at surface and at TOA, and mix them together.
9. RW1 at 10:10 AM on 19 December, 2010
   Very Tall Guy (Post # 7), You need to be more specific - I'm not sure what you're trying to say. The halving of the CO2 absorption is because the re-radiated energy goes out in all directions - meaning half is radiated upward in the same general direction it was already headed; thus it cannot contribute to additional warming.
10. RW1 at 10:16 AM on 19 December, 2010
    Riccardo (RE: Post 8), I'm not sure what you're trying to say either. Can you give me some specifics?
11. muoncounter at 10:25 AM on 19 December, 2010
    #5: "from a doubling of CO2 ... an additional 3.2 W/m^2 will increase the surface temperature only about 0.6 degrees" We've already had more than 0.6C warming since ~1960, which only represents an increase of atmospheric CO2 from 317 to 388, nowhere near a doubling. So its clear your numbers are coming up short. But at least you agree that it's warming and that CO2 is part of the GHE, so that's a start. The general climate sensitivity question was dealt with on prior threads, notably here. You should check there for additional information.
12. Riccardo at 11:05 AM on 19 December, 2010
    RW1 you first calculated a sort of energy balance at the earth surface to calculate the "amplification factor"; then you took the (net) energy imbalance at TOA, the 4 W/m2 for doubling CO2, and used the same "amplification factor" to calculate the extra energy received by the surface and the increase in temperature.
13. RW1 at 11:15 AM on 19 December, 2010
    Riccardo (RE: Post 12), All I did was apply the same gain factor for solar power to additional power from CO2.
14. RW1 at 11:18 AM on 19 December, 2010
    I'm asking the question because I think it's a significant hole in the AGW theory that I've yet to see adequately explained. What I'm trying to show is that the CO2 AGW theory is saying that the climate system is all of the sudden going to treat an additional 2 W/m^2 of power at the surface radically different than it does the original existing 99+ percent, and while I suppose that is theoretically possible, there is no physical, empirical or logical reason why it would, especially in a system that is constantly changing everywhere, by relatively large magnitude. Ultimately, what matters is the total infrared power at the surface, independent of where all the power orginates from - the the Sun, GHGs and/or clouds. Both 2 W/m^2 of additional infrared power from the Sun "forcing" the surface and 2 W/m^2 of additional infrared power from CO2 "forcing" the surface are the same - all the surface 'knows' is what the total power is, and the total power is directly tied to temperature via Stefan-Boltzman (*if this was not true, then power from the Sun and additional power from CO2 cannot both be expressed in W/m^2 as they are). The point I was making about the perihelion power increase of about 14 W/m^2 was that a much larger increase in radiative forcing above the average doesn't have anywhere near the proportionally predicted effect as the AGW warming theory says will happen with just a 2 W/m^2 increase in radiative forcing from a doubling of CO2. Now of course one can always say that it will be the 2 W/m^2 increase above the total cumulative average that will cause a much larger amount of warming by suddenly triggering very large positive feedbacks (that don't happen to exist or act on the original 99+%), but there really isn't any physical, logical, or empirical basis for that, especially given the total amount of radiative forcing is constantly changing spatially and in time...all the time (warming, cooling, etc). If the climate as a whole was a steady state and static system, it might be more plausible, but the climate system is incredibly dynamic instead. That the global climate doesn't even appear to be phased by a 14 W/m^2 increase in radiative forcing, suggests the net feedback operating on the system as a whole is strongly negative - not positive, and the tiny increase of only about 2 W/m^2 from a doubling of CO2 will be - if not infinitesimal, benignly small.
15. Riccardo at 12:04 PM on 19 December, 2010
    RW1 there are a few pieces that got to be fixed. "All I did was apply the same gain factor for solar power to additional power from CO2." You did it wrong as I explained in my previous post, you're confusing surface and TOA. "Ultimately, what matters is the total infrared power at the surface" The energy balance of the planet is governed by what happen at TOA, not at the surface. What we see (measure) at the surface is the effect of the change at TOA. "The point I was making about the perihelion power increase of about 14 W/m^2 was that a much larger increase in radiative forcing above the average doesn't have anywhere near the proportionally predicted effect as the AGW warming theory says will happen with just a 2 W/m^2 increase in radiative forcing from a doubling of CO2." (emph. mine) You should not expect any proportionality, indeed. When you have a cyclic forcing, the effect depends of the response time of the system. If the response is slow you won't get the full effect of the forcing; you are comparing a forcing with a one year period with a response time of the order of decades. An extreme example is the diurnal cycle, where you have the forcing going from about 240 W/m2 to zero but the temperature doesn't change proportionally.
16. RW1 at 13:20 PM on 19 December, 2010
    Riccardo (RE: Post 15), How am I confusing the surface and the TOA? Are you saying that power from the Sun and additional power redirected from CO2 are not both "forcing" the surface? The energy balance is determined by the rate at which incoming power from the Sun is allowed to leave the planet (at the TOA): The incoming short wave infrared energy from the Sun is mostly transparent to the clear sky atmosphere. Cloudy sky is obviously different, as a lot of the energy is reflected off of and absorbed by the clouds - a much smaller amount makes it through. The short wave energy that hits the surface is re-radiated back up in the form of long wave infrared, which in certain wavelengths is absorbed and re-radiated by greenhouse gases and/or clouds. In effect, the presence of greenhouse gases and clouds delay the release of infrared heat energy by redirecting some of it back toward the surface, which makes the surface warmer than it would be otherwise. The albedo adjusted gain factor of about 1.6 means that due to the greenhouse effect, it takes about 1.6 W/m^2 of power at the surface for each 1 W/m^2 of power to leave the system, offsetting each 1 W/m^2 entering the system from the Sun. In other words, power in = power out. The albedo adjusted solar input of about 238 W/m^2 = 238 W/m^2 leaving the planet, and a power of 238 W/m^2 equates to a temperature of about 255K, which is the so-called effective temperature of the earth as seen from space. There is no difference between power sourced from the Sun and additional power re-directed back to the surface as a result of more CO2 being added to the atmosphere. Afterall, a watt/meter squared of energy and power is watt/meter squared of energy and power, independent of where it originates from. Put another way, the surface doesn't "know the difference" between heat or power sourced from the Sun or additional heat or power re-directed back down from GHGs and/or clouds - all it "knows" is what the total heat and power is at the surface; and the total power at the surface in W/m^2 is directly tied to temperature via Stefan-Boltzman because the surface of the earth is considered to be very close to a perfect black body radiator. At an average global temperature of 288K, the surface emits 390 W/m^2 of power. About 240 W/m^2 of this is from the Sun and the additional 150 W/m^2 is from GHGs and clouds in the atmosphere re-directing infrared power back down toward the surface. If the albedo adjusted power from the sun increases 2 W/m^2, the infrared power at the surface increases 2 W/m^2, plus about an additional 1.2 W/m^2 will be redirected back downward from the atmosphere (due to the presence of GHGs and clouds) for net increase of about 3.2 W/m^2 - raising the surface power total to about 393.2 W/m^2 (or a temperature of 288.6K). If instead, the albedo adjusted power from the Sun is unchanged, but an additional 2 W/m^2 of infrared power is redirected downward to the surface as a result of a doubling of CO2, the most additional power that can amplify (or in effect re-redirect down) the added 2 W/m^2 is only about the same 1.2 W/m^2 because there is no physical or logical reason why an additional 2 W/m^2 of infrared power at the surface will behave radically different from either the original 99+% or an additional 2 W/m^2 from the Sun.
17. RW1 at 15:34 PM on 19 December, 2010
    Riccardo (RE: Post 15) The hemispheric seasonal responses to large changes in radiative forcing are relatively quick – certainly not years or decades. If they were, we wouldn't see anywhere near the seasonal variability throughout each year. There is a delay or "seasonal lag", but it’s only about one month. This contradicts the notion that a tiny increase in radiative forcing of less than 2 W/m^2 from a doubling of CO2 gradually added to atmosphere over decades will take decades longer after to reach equilibrium. If anything, because CO2 is added incrementally and so slowly over such a long period of time, the response time is a non issue.
18. muoncounter at 16:33 PM on 19 December, 2010
    #17: The two paragraphs in your comment don't seem to have any logical connection. Don't the oceans have thermal inertia? Is there any research regarding 'albedo adjusted gain', beyond this website?
19. RW1 at 17:15 PM on 19 December, 2010
    muoncounter (RE: post 18), Yes, the oceans have thermal inertia, as evidenced by the roughly one month of "seasonal lag", but the overall response is still relatively fast in each hemisphere every year. This contradicts the ocean thermal inertial taking decades to fully respond. The albedo adjusted gain is just an aggregate empirical measure of the system's response at the surface to incoming power from the Sun. As you can see from that site, it varies a little but is roughly about 1.6 on average.
20. archiesteel at 18:34 PM on 19 December, 2010
    @RW1: that site (www.palisad.com) doesn't seem very credible. The best analogy that has been given is the tub filling in vs. ripples. Seasonal variations tend to cancel out over time, while the current warming we are seeing keeps going up. The whole isn't in AGW theory, it's in your understanding of the theory.
21. Riccardo at 19:54 PM on 19 December, 2010
    RW1 the often quoted 4 W/m2 is the imbalance at TOA, i.e. the amount of energy not allowed to leave the planet after a doubling of CO2. Following your scheme, an equal amount is radiated back to the surface. In this way you get a 1.2 K increase in temperature; incidentally, this is equal to the so-called Plank sensitivity. To know the equilibrium temperature increase you still need to multiply it by the feedback factor, which is not included in the 4 W/m2.
22. VeryTallGuy at 02:36 AM on 20 December, 2010
    RW1 @9 The 4 W/m2 is total change in radiative forcing at the top of the atmosphere (TOA). 4W/m2 extra heat absorbed by the earth's system. That's the change in total heat balance at that point. You can't just halve it to suit your argument.
23. RW1 at 02:37 AM on 20 December, 2010
    Riccardo (RE: Post 21), The cumulative effect of all the feedbacks are already accounted for in the measured gain response of 1.6. This is why the total increase in temperature is greater than the intrinsic response.
24. muoncounter at 03:05 AM on 20 December, 2010
    How do these statements, taken together, make any sense? #16: "The albedo adjusted gain factor of about 1.6 ..." #19: "... is just an aggregate empirical measure of the system's response at the surface ..." #23: "... cumulative effect of all the feedbacks are already accounted for in the measured gain response of 1.6. This is why the total increase in temperature is greater" If gain=1.6 and gain is an 'aggregate empirical measure', then 23 is contradicted. If the total increase in temperature is greater than you predict (and it is), then either 16 or 19 are incorrect. It appears that your numbers put you in line with the "ultra-conservative unrealistic low climate sensitivity scenario", which is addressed in a very thorough treatment here.
25. RW1 at 03:39 AM on 20 December, 2010
    VeryTallGuy (RE: Post 22), 4 W/m^2 would the total that affects the surface only if all the absorbed power is directed back toward the surface, but only about half of it does because GHG infrared absorption and re-radiation is in all directions - i.e. about half goes down and other half goes up out to space in the same general direction it was already headed.

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