Saturday, April 9, 2011

My (incorrect) Answer to the Energy Budget Puzzle

There are several things I find interesting about the energy budget and the Stefan-Boltzmann law. If the Earth had no atmosphere, we would be about 33 degrees cooler. So by the same equation that gives 46016.5 W/m^2 for three degrees warming, 5.67e-8 * [(291)^4-(255)^4 would gives us 6175 167 Watts/meter^2. That's a lot of Watts! While the atmosphere has only been at this temperature for a little over 10,000 years, I doubt that the warming lag time of the oceans hasn't been fairly close to met. Intuitively, I would think that temperature rise of the atmosphere is proportional to the increase in Watts by the S-B law. That would lead me to believe that 6175167/33 equals 187 5.1 watts per degree. It is not of course, it is just a linearization purely for estimation. The 460 16.5Watts/m^2 divided by 3 is 1.53e-1 W/m^2 per degree K or C if you like. So while making the Watt/K relationship linear is not proper, it is a fair estimate for the temperature range.

Because of a typo and dropping the exponent, the numbers above are off. I'll revise the numbers in the morning. That's what I get for posting without letting it set before final proof.

Looking at the NASA cartoon a couple things stick out, the 6% radiated directly to space and the 23% heating by latent or evaporation to water vapor. The average temperature of Earth is 288 degrees K which is 15 degrees above 273K which is the freezing point of fresh water. Using another simple ratio, 23%/15 equals 1.5% per degree. So with a three degree warmer atmosphere, the latent heat would increase by 4.5% to 27.5%. Since the original 23% is 78 Watts/m^2, the increase due to the 3K is about 15 Watts/m^2 or 5 Watts/m^2 per degree.

The 6% radiated to space is about 20.5 Watts/m^2. CO2 doubling will close some of that atmospheric window. Just for an estimate, let's say it closes it all. So instead of the ~4 Watts/m^2 estimated by the IPCC we have 20.5.

While this is essentially mixing apples and oranges, the 20.5 Watt/m^2 by closing the window plus the 15 Watts/m^2 assuming increased water vapor due to 3 C warming is about 36 Watts/M^2.

We have a lot of apples and oranges plus maybe a mango. The Mango is the Sun. It puts out 342 Watt/m^2 roughly and that is not changing, much anyway. If we close the window and assume 3 degrees K worth more latent heat, we only have 36 Watts/m^2. The S-B law says that radiation will increase by 460 16.5 Watts/m^2 at 291 K which is the expected temperature in 2100 roughly. We also have 6175167 Watts/m^2 that S-B Law says that is what happened when we got an atmosphere that raised the surface temperature by 33 degrees. Other than minor fluctuations, energy into the atmosphere will equal energy out of the atmosphere. That is unless there is some work being done in the system. We can't just create energy out of thin air, so we are not going to get more work and the same energy out. So how are we going to get to some semi-stable temperature of 291 K with a CO2 doubling? My guess is we won't. Just as we obviously do not have 6175 Watts/m^2 emitted from the surface, that is emitted at the top of the thermosphere where the temperature is 70 C or 343K. Something else is happening under the thermosphere just like something else is happening in the depths of the oceans.

Just for shits and grins, let's say that a doubling of CO2 with water vapor feedback leads to 1.3 degrees K of warming. If you look at the NASA cartoon you will see that there are three layers of different color blue. In the bottom darker layer, no radiation from the Earth is absorbed. There is some of course, but it is dominated by latent heat and conduction/rising air. The absorbed radiation from the Earth's surface dominates in the middle blue layer even though there is some latent and conduction/rising air in that layer due to major convective storms. The change in CO2 impact should dominate in that layer. The doubling of CO2 may very well increase the absorbed radiation budget of that layer by 4 Watt/m^2. That does not mean the impact of the 4 Watts/m^2 in that layer will manifest itself as 3 K warming at the surface. It will have some impact at the surface and that impact will increase evaporation. Just as a guess, let's say the impact by CO2 alone is 1 K at the surface with the other 0.3 K due to water vapor.

Based on that assumption, the window is shut a little so now it is 16.5 Watts/m^2 The latent heat increases from 78Watt/m^2 to 79.5 Watt/m^2. So why would I think something so silly? I mean, CO2 doubling increases the radiative forcing by about 4 Watts/m^2, but only increases the surface by 1 degree with water feedback that kicks the impact up to 1.3 degrees. The reason is where the 4Watts/m^2 main impact dominates, is a low temperature region of the atmosphere. Energy in is going to equal energy out, with minor fluctuations. The apparent temperature from space is the thermosphere where the temperature is warmer than the surface of the Earth. The top of the troposphere (on average) into the lower stratosphere is the lowest temperature of the atmosphere in relation to the major layer where CO2 increased forcing will have an impact. Just like the apparent temperature of the ocean is the surface. The change in the radiation budget will not be at the top of the thermosphere, it will be in the upper troposphere into the lower stratosphere and less so at the surface. While the increased CO2 will decrease the lapse rate, heat still flows from warm to cold, which implies that most of the heat from CO2 doubling will flow to the nearest cold region of the atmosphere. Major warming of the surface will not occur until the nearest cold region of the atmosphere, the region around the tropospause and 10 kilometers into the stratosphere, warms uniformly. So the lapse rate would have to decrease by over 50%, for the majority of the CO2 forcing to be of impact at the surface.

Since I can't find an English copy of Arrhenius' second paper where his impact of CO2 doubling reduced from 5 C to 1.6 C, I can't be sure. I doubt he just caved. I suspect he reconsidered the Tropopause sink, which lead to his re-evaluation. If I were to redo the Energy Budget cartoon's, I would be more specific about the layers of the atmosphere where the dominate impacts occur. That would simply the cartoons without over simplifying them.

So my answer is there will be no 3 degrees warming by 2100 at the Earth's surface due to CO2 doubling, but the window will shut a little and there will be more water vapor. Then Stefan's law is not violated, Arrhenius' revised law is not violated nor are the laws of thermodynamics. But then, I am just a fisherman, that applied for a job at a Holiday Inn Express.

My Epiphany may be shot because of the S-B mistake, I will need to redo my spread sheet, because of the garbage. The flow from the CO2 heating "Zone" should still have a significant sink component.

1 comment:

Dallas said...

As Fred noted before, when I typed this I did not use the full 5.67 e-8 for the 5.67. So that is off by only a factor of e-8 Sheeze! Still, S-B law appears to be lost in mix with the real action being at the top of the troposphere. I will revise the puzzle.

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