CO2 is actually a stronger greenhouse gas, but at the slope of the log curve CH4 is at, yes, it has a higher "radiative efficiency." CO2 at the same level has even a greater radiative efficiency than CH2. I just don't want people thinking CO2 is a weaker greenhouse gas then CH4. Radiative efficiency is the value of change in W/m^2 for a 1 ppb increase in the gas from it's current level.
I don't know which paper you're looking at, but in the copy of Kiehl & Trenberth I'm reading, Section 3, Radiative energy budget, is divided into three subsections, a. Top-of-atmosphere fluxes, b. Longwave radiation, and c. Shortwave radiation. The only reference to Table 3 is in subsection 'b' which is clearly talking about longwave radiation. In subsection c. on shortwave radiation, it directs you to Table 4, which puts the contribution from CO2 at only 1 W/m2. And what is the corresponding value for the greenhouse contribution from H2O in those texts? Even if you combine the total longwave (125 W/m2) and shortwave (60 W/m2) contributions from Kiehl & Trenberth, 43% of the 324 W/m2 back radiation is still missing. Shouldn't that tell you that these numbers are not the same?
OK, I missed the part where table three is discussed in part b. Maybe you can explain this then. Where does the total 324 W/m^2 back radiation come from? Perhaps from the clouds themselves, once you account tor CH4, N2O, etc; which would be water back radiation? Sill, the stated longwave downforcing total in various papers for CO2 is in the neighborhood of 30 W/m^2. The total longwave downforcing in in the neighborhood of 340 W/m^2 by various papers. This puts CO2 at under 10% of the longwave downforcing effect. I have to leave soon, probably won't have another post tonight.
The 342 W/m2 back radiation appears to be the sum of 350 W/m2 surface radiation, 78 W/m2 latent heat flux, 24 W/m2 sensible heat flux, and 67 W/m2 shortwave absorption, minus the 195 W/m2 longwave radiation emitted back into space. Since climate forcing is by definition measured at the tropopause (top-of-atmosphere), isn't comparing it to the heat fluxes between the surface and the atmosphere like comparing apples to oranges?
Yes, and most of the backradiation is from H2O. CO2 is only about 30 W/m^2 of it. What else, if not H2O? Ah.... That's how they reduce water values in the downfocing. By this point, there is almost no water in the atmosphere! Meaningful discussions about forcing and temperature change need to be in the lower few miles. Not at 6 to 11 miles up. CO2 is evenly spread throughout the atmosphere. Even CH4 and N2O are rather even. H2O however liquifies and freezes in the atmospheric layers, and falls out as rain.
But not all of the 324 W/m2 back radiation is forcing climate, is it? Much of it is cancelled out by the latent and sensible heat fluxes coming from the surface. Since clouds can extend upwards as high as 60,000 feet (11 miles), wouldn't focusing on lower altitudes overlook a significant factor in climate change?
The latent and sensible heat, is heat added to the greenhouse effect. The back radiation of the 324 to 342, depending on the paper you look at, is the gross greenhouse effect. It's called the greenhouse effect because it traps and returns heat rather than it all disappearing into space. Even if you remove the sensible and latent heat, there is the 390 surface radiation that cannot be ignored. These few clouds probably reduce the suns intensity to the surface more than cause any warming. Regardless, you cannot use any defined layer and claim a percentage of forcing from it. It's far more complex that that. The closer you get to the surface, the more the percentage of H2O matters. If those numbers indeed come from the tropopause, then the are completely inaccurate for the radiative forcing caused by H2O. Again, CO2 is well mixed, H2O is not. Looking at H2O on a log scale for the polar winter and tropical: Look at the scale of difference by height. The tropopause is near where the H2O gas volume trend stops reducing as we move away from the surface. There is around 10,000 times more water in the tropics at the surface than 20 km up. The polar winter has around 140 times as much water at the surface air than around 13 km up. I find it interesting that the polar winter has more water vapor at around 1.5 km that the surface. It suggests to me that this is the height that might be best suited to look at radiative forcing.
I'm not ignoring the 390 surface radiation, in fact it is the key to the whole problem. The Earth adds 390 W/m2 to the atmosphere, 235 W/m2 of which escapes into space, leaving 155 W/m2 of energy in the atmosphere. Of the 342 W/m2 back radiation, 169 W/m2 either returns to the atmosphere from as latent and sensible heat or directly from solar radiation, giving us the same 155 W/m2 difference. Why would you measure climate forcing against back radiation only when it is energy that remains in the atmosphere that drive's Earth's climate? That's not what experiments show. Low clouds are good radiators while also blocking more shortwave radiation. But higher clouds are better absorbers and are virtually transparent to shortwave radiation. If you're looking to measure the greenhouse effect, you need to look at the whole atmosphere.
it depends on weather patterns, if increased heat is driving increased heat over continents, it would increase desertification and reduce water vapor in the atmosphere, or result in more energetic weather systems which remove water vapor from the air.
Why don't you go to a reputable source of information, like the NASA website linked to in this thread, and get some real information.
The values are important to keep in the absolute terms so blackbody formulas still work. What do they mean by "higher clouds? At what elevation? I'm running out of time and have to leave soon, but here is the link for the first reference listed, the whole article: http://thingsbreak.files.wordpress....nce-for-positive-low-level-cloud-feedback.pdf I didn't note anything of interest, but just quickly scanned it. The third reference doesn't quantify anything: Higher by how much? 0.0001 degrees? 0.1 degrees? 10 degrees? It is not quantified!
"The last time there was this much carbon dioxide (CO2) in the Earth's atmosphere, modern humans didn't exist. Megatoothed sharks prowled the oceans, the world's seas were up to 100 feet higher than they are today, and the global average surface temperature was up to 11°F warmer than it is now".http://www.climatecentral.org/news/the-last-time-co2-was-this-high-humans-didnt-exist-15938 So if the CO2 increase is caused by burning carbon (fossil fuels) why was it higher prior to humans? Until that question is proven "scientifically", IMO we don't need to start taxing fossil fuels as the EPA is suggesting. We would have to stop all use of fossil fuels globally to have even a small decrease in atmospheric CO2. Scientific hypothesis does not warrant increased taxation of energy we rely on and need to survive in the current environment.
Who told you that? Weather has everything to do with climate, but that doesn't mean that weather IS climate.
Absolute values are important for calculating Earth's total energy budget, but climate is only forced by the net heat flux. Usually 5 to 12 km. Here's something else you can scan in your free time. http://nenes.eas.gatech.edu/Cloud/NASAClouds.pdf
Just because humans are causing the current increase in CO2, doesn't mean humans are the only reason CO2 can increase. But we know "scientifically" that humans are causing current increases because burning fossil fuels produces different carbon isotopes than other sources.
One should be cautious to try to compare such ancient pasts with present day. There are so many other reasons, especially ocean mass and temperature. A warmer ocean of an earth with more dense jungles, humidity, temperature, etc, will not absorb so much CO2. There is approximately 50 times more dissolved CO2 in the ocean than there is in the atmosphere. If that 98% were to change to 90% with increased temperature, then they atmosphere would have 5 times as much CO2. Look at Henry's law sometime and the associated science, and see how dramatically small temperature changes can make dramatic changes of gas solubility in water.
Still need a zero reference point to properly asses changes. If I increase a gas by 40 ppm, since changes are logarithmic instead of linear, it makes a big difference. If I'm starting at 40 ppm, then I doubled the gas concentration, but if I'm at 400 ppm, I only increased it by 10%. Forcing is the same since forcing to temperature is a fourth power function. We can go by percentage increases to calculate from, not not additions. Well, it seems to me that is rather meaningless. For one, the densities are so low. Now because of that such clouds offer a huge increase in water vapor at that altitude, and since forcing is on a log curve, the changes for that altitude would be significant. However, in the end, I think it has little or no significance for surface temperatures. What free time? I already spend too much time here. Still, it was short, but nothing new. Again, nothing is quantified.
It is also important to use the proper reference point. If a source increases a gas by 40 ppm, but a sink is reducing it by 20 ppm, then the forcing is only due to the remaining 20 ppm. What it seems to you and what you think are irrelevant to me. I go by what the science says.
I'd say we simply have to grow more trees, BUT: "Trees cause more pollution than automobiles do." -- Ronald Reagan, 1981.
People that believe in GW mainly. When it is mentioned that temps are colder in a region they say that's just weather. When it is warming in a region they say it's global warming.
Whoever you've been listening to, they've been lying to you. Here is a more reputable source for you. http://www.nasa.gov/mission_pages/noaa-n/climate/climate_weather.html
I didn't know he was a climate scientist, either. Apparently he was a climate scientist or he wouldn't have run his big mouth. The man was the Sarah Palin of his decade. Never read his books.
