On the battle between Arrhenius and Ångström.
Story submitted by John Kehr, The Inconvenient Skeptic
Any serious discussion about the Theory of Global Warming will eventually include the absorption band argument that started more than 100 years ago between Arrhenius and Ångström. One of the arguments presented by Ångström was that the main CO2 absorption band is between 14-16 micron and that band is also absorbed by water vapor (which is correct). The counter to this by Arrhenius was that it didn’t matter in the upper atmosphere where there was no water vapor. Of course none of this matters because radiative heat transfer is only 20% of the energy transferred to the atmosphere, but that is generally ignored by both sides of the argument.
At the time there was no way to measure the temperature in the upper atmosphere so there was no way to determine what was going on there, but of course now there are many ways to measure the temperature there. When I started looking at the annual temperature behavior of the stratosphere and the top of the troposphere I found something very interesting that is as usual, bad for the warmists.
Here is the average daily temperature of the troposphere (at ~4.2 km) and the stratosphere (41 km).
What makes this so interesting is that they are completely out of phase with each other.
The tropospheric temperature is matched to the natural global temperature cycle. This is highly dependent on the geography of the Earth’s surface. The stratospheric temperature is not in phase at all with the surface temperature. It is however in phase with the Earth’s orbit around the Sun. The distance the Earth is from the Sun determines how much energy the Earth gets from the Sun. Here is the stratospheric temperature and the solar constant over the course of the year.
While I would not say that the upper atmospheric temperature is completely independent, it is mostly independent of the of the lower atmosphere. The cooling in the stratosphere each spring is exactly what would be expected based on the changing solar constant. The warming that takes place in July is likely caused by the peak atmospheric temperatures in the NH that take place during the summer months. That warming stops in October, but by that point the increasing solar iconstant warms the stratosphere.
What determines the stratospheric temperature is absolutely critical to understanding why it has been cooling over the past 60 years (which is about how long it’s temperature has been measured). If the stratosphere’s temperature is primarily dictated by the incoming solar energy then the argument made by Arrhenius is meaningless. That is because the increase in CO2 would never have an impact on the temperature there, simply because so little of the energy needed to warm the stratosphere comes from the Earth’s surface.
Based on the scientific data, the stratosphere is mostly influenced by the solar constant (basically the distance from the Sun for this discussion). There appears to be some influence from the lower atmosphere, but it is clearly marginal. This is not really a surprise since the energy transfer mechanisms are very limited above 12km. The low atmospheric density results in low vertical mixing rates which only leaves radiative transfer which is a poor method for heat transfer when low absolute temperatures are involved.
When the temperature of the stratosphere and the troposphere are compared for the period from 2003-2011 it is also interesting to note that the peak stratospheric temperature was lowest of the whole period in early 2009. This also matches the period of minimal solar activity over the entire period of time. All of these pieces together clearly demonstrate the importance of the solar constant on the stratospheric temperature. This also means that any impact by atmospheric CO2 levels on the stratospheric temperatures is very limited.
Total Solar Insolation