The Unsettled Earth Energy Budget
An examination of the energy budgets for the Earth of recent years gives one reason to be unsettled about the settled science claimed for the catastrophic man-made global warming hypothesis. The energy budget currently posted by NASA is shown in Figure 1 below.
Figure 1 shows the principal NASA energy budget for the Earth as of February 2013. Note the huge surface radiation and the huge radiation from the atmosphere all of which is absorbed by the surface. The surface-absorbed atmospheric down radiation is 100% of the solar insolation at the top of the atmosphere and it is all claimed to be absorbed by the surface! The greenhouse gases absorb a very unrealistic 90% of all of the radiation emitted from the surface!
It is interesting to compare this most recent energy budget with the energy budget with an energy budget briefly found on a NASA website and still found in an educational resource here. This energy budget looks like this:
Figure 2 shows this ephemeral NASA energy budget much more realistically showed a much reduced radiation emission from the surface and no radiation from the atmosphere to the surface. Most of the time, there will be very, very little radiation from the air to the surface, but sometimes the air over the surface is warmer and it will provide some warming of the surface. But zero radiation is much, much more realistic than 100% back radiation. The IR-active gases absorb 71% of the radiation emitted by the surface, which is much more realistic than 90%, but is still too high.
We will compare these recent energy budgets from NASA with the Kiehl-Trenberth energy budget of 1997 which was featured in the UN IPCC report of 2007. That budget is shown below with my conversions to percentage of the solar insolation energy density at the top of the atmosphere.
Figure 3 shows the The Kiehl-Trenberth energy budget for the Earth of 1997, which was featured in the UN IPCC report of 2007. This energy budget claims a 114.0% emission of radiation from the surface with an unbelievable 90% of it absorbed by IR-active gases in the atmosphere just as with the NASA budget of Figure 1. Radiation from the atmosphere to the surface is a fantastic 94.7% and it is claimed to be entirely absorbed by the surface.
The items in the several energy budgets can now be compared and I will try to determine the best likely values for the various items in the following table (Fig4):
I will discuss these item by item.
Atmospheric Reflection: This is reflection from the boundary layers of the atmosphere, from aerosols, and from clouds. The energy budgets vary from 22.5% to 26%. But what is constant is the sum of the atomspheric and the surface reflectivities at 30%. The problem is in how the reflectivity is divided by type. The most recent NASA values ought to be the best, especially given that there is no real advantage to the global warming alarmists as long as the sum of the surface reflection and the atmospheric reflection is 30%. The newest values also lie between the older values.
Surface Reflection: See the discussion under Atmospheric Reflection. In addition, a 4% reflection as stated in the NASA 2011 budget is clearly too low a reflection value in my experience with UV, visible, and shortwave IR on surfaces.
Atmospheric Absorption: This is a hard value to measure by itself directly, but it is the difference between 100% and the sum of the Atmospheric and Surface Reflections (30%) and the Solar Surface Absorption.
Solar Surface Absorption: I am inclined to believe the NASA 2011 energy budget on this one since a belief in a large back radiation or radiative warming of the surface by the atmosphere will tend to bias the absorption believed to be due to direct solar radiation downward. Fixing this number at 51% then fixes the Atmospheric Absorption at 19%, which actually does agree well with many prior analyses.
Conduction, Convection from Surface: Only the NASA 2013 value is different from 7% and it is likely lower because that budget increased the back radiation or warming of the surface by the atmosphere to an outrageous 117%. Since they had increased the water evaporation cooling to 25%, this meant the Conduction, Convection from Surface value had to go down. Lowering this value from 7% is surely the wrong direction to go in. For reasons I have discussed in my long paper discussion
within a very short distance of 200 m from the surface almost all of the IR radiation from the surface that can be absorbed by IR-active gases has been absorbed and shared with the 99.97% of the non-active gases. Conduction and convection then rises rapidly close to the surface with increasing distance and then stabilizes. This is why I believe the 7% initial power density increases to 21% at less than 200 m from the surface. The sum of the Conduction, Convection from the Surface, Evaporation, and Surface Radiation must equal the sum of the Solar Surface Absorption and the Radiation from Atmosphere Absorbed by Surface.
Evaporation: I just averaged the three energy budgets and weighted the most recent a bit more. Richard Lindzen believes that the cooling by water evaporation has been underestimated as well.
Surface Radiation: I set this in accordance with the NASA 2011 energy budget since the other two energy budgets hugely exaggerate this to accommodate their huge back radiation values. I showed in my analysis in the paper Infrared-Absorbing Gases and the Earth’s Surface Temperature that there was an upper bound of 5.8% on the amount of back radiation incident on the surface. This was without even invoking the fact that heat flows from warm to cool surfaces and conditions when the air is warmer than the surface other than within a very few tens of meters are infrequent. Because I set the back radiation warming at an estimated value of 1%, the Surface Radiation is (51 + 1 – 7 – 24)% = 21%.
Surface Radiation Absorbed by Atmosphere: The sum of this and the Surface Radiation Emitted to Space must equal the Surface Radiation immediately at the surface, which is 21%. All of the surface radiation that can be absorbed was calculated in the paper and found to be about 65% of the Surface Radiation. With Surface Radiation at 21%, this value is 14% here. That value is close to the most believable NASA value of 2011 for this, so I am sticking with 14% here.
Surface Radiation Emitted to Space: This was determined to be about 35% of the Surface Radiation in my paper.
Radiation from Atmosphere Absorbed by Surface: Because there is much less radiation from the surface in the first place than assumed by NASA 2013 and by K-T 1997, the mean free path for absorption of radiation is so short, the molecular collision rate is so high, and the non-radiating molecules are about 99.97% of the atmosphere, I showed that there was a maximum back radiation to the surface of about 5.8%. Not all of that would be absorbed even if from a warmer atmosphere and since the atmosphere a very short distance above the surface is usually cooler than the surface, a realistic estimate of warming by atmospheric radiation is about 1% in close agreement with the NASA 2011 energy budget. This value is certainly realistically less than 2%.
Radiation Emitted by the Atmosphere into Space: This plus the Surface Radiation Emitted to Space must equal 100% minus the solar insolation reflected back to space, which is 30%. Since I set the Surface Radiation Emitted to Space to 7%, the value for the Radiation Emitted by the Atmosphere into Space is 63%. This is above the average of the energy budgets shown above, but less than the NASA 2011 budget.
Total Radiation Once Absorbed Emitted to Space: This value clearly should be 100% minus the reflected sum, which all accounts set at 30%. Despite this, the NASA 2013 and K-T 1997 values are not quite 70% as they should be.
% of Surface Radiation Absorbed by Atmosphere: This is just the (Surface Radiation – Surface Radiation Emitted to Space)/ (Surface Radiation). My value is lower than the NASA 2011 value and much lower than the high surface emission energy budgets yield.
I have made this evaluation of the various items in the energy budget so that I might recalculate some of the numbers such as the Earth’s effective surface emissivity and the consequences upon the surface temperature due to such effects as the absorption of solar radiation due to water vapor and carbon dioxide using a consistent and realistic set of these items from an energy budget.
As we can see, there are some disagreements in the settled science, especially stemming from the values for Surface Radiation and Radiation from Atmosphere Absorbed by Surface. Those big errors may also be the cause of many of the other items being a bit off. It is important to understand this background to the catastrophic man-made global warming hypothesis to critically evaluate it.