Ordinarily, one expects the outgoing long-wave IR radiation to be proportional to the incoming solar short-wave radiation. From about 1979 to 2009, the outgoing long-wave radiation was increasing, as was the incoming solar radiation. But from 1948 to 1975, the average temperature was flat according to the first graph above. This suggests that the incoming solar short-wave radiation was not greatly increasing in that time-frame. Contrary to that, the period from 1948 to the mid-1970s shows a big increase in the outgoing long-wave IR radiation, especially between 1950 and 1966. No big increase in incoming solar radiation and increasing CO2 concentrations in the atmosphere should preclude such a large increase in outgoing long-wave radiation if the standard CO2-induced catastrophic warming hypothesis were correct. The increasing CO2 concentrations should be causing the outgoing long-wave radiation to decrease as CO2 molecules re-emit half of the long-wave radiation they absorbed back toward the Earth's surface. Increased concentrations of CO2 in the upper atmosphere, where radiative cooling dominates over convective processes, should allow the very energetically excited CO2 molecule which has absorbed incoming short wave radiation from the sun to efficiently re-emit that short-wave energy back into space. Still more mysterious in terms of this CO2 hypothesis is the sudden jump in outgoing long-wave radiation from 1976 to 1981! Basically, the overall strong increase in outgoing long-wave IR radiation from 1950 to 2009 should correspond to a major decrease in the amount of CO2 in the atmosphere. There was no such decrease, but was instead a steady increase in CO2 concentrations, at least according to the data popularly presented by the advocates of catastrophic CO2-induced warming.
So, the low concentrations of CO2 in the atmosphere do not account for the temperature record constructed by the advocates of a strong CO2 warming effect. What phenomena are then causing both the increased outgoing long-wave IR radiation and the broadly rising temperature? For one thing, during the same period from 1983 to 2009 that the incoming solar radiation was increasing as shown above, the global cloud cover was decreasing. This is consistent with the theory of Henrik Svensmark that when the Sun has an increase in solar activity, the sun projects its electromagnetic field further and that protects the Earth more from cosmic rays. The decreased flux of cosmic rays is said to allow for the nucleation of fewer clouds, consistent with the decreased cloud cover in the plot below as the Earth warmed in its last warming cycle.
But, it turns out that this is not the only effect affecting global temperatures. The following graphs show the atmospheric humidity at various pressures, which drop as the altitude increases. I will also give an altitude, which is that of the U.S. Standard Atmosphere of 1976, for which the sea level temperature was 288.15 K or 15 C. The time history of the humidity at 1000 mbar (1 bar) pressure or sea level is:
As the temperature has increased since the mid-1970s, the sea level humidity has increased. This is expected. Increased temperature causes increased water evaporation from the oceans and land. This also causes a counterbalancing cooling effect since it takes a huge amount of energy to cause water to warm up and still more to cause the phase change into a gas as water vapor.
At the atmospheric pressure of 925 mbar, or about 750 meters altitude, the history of water vapor is shown in the following graph:
The humidity at this altitude may be said to have fallen from the 1950s a bit, then held steady from the mid-1960s to the mid-1990s. After the mid-1990s, the concentration of water vapor increased. The increase at this altitude lagged that at sea level by about two decades. At this altitude, cooling of the Earth's near surface is dominated by convection processes and molecular collisions. The historical trend is very different when we examine the humidity record at 600 mbar (4170 meters) as shown below:
Thus, we see that at the higher altitudes, where radiative cooling dominates, water vapor has become rather less common in the upper atmosphere. As I have previously discussed, the effect of either CO2 or water vapor on temperatures at the Earth's surface depends both on their absorption of incoming short-wave radiation and on outgoing long-wave radiation. Increased IR-absorbing gases, often called greenhouse gases, cause the absorption of more of the sun's incoming radiation well above sea level. This has a cooling effect upon the Earth's surface. An increase in water vapor, the primary IR-absorbing gas, in the higher altitudes of the last two graphs would have a considerable cooling effect on the Earth at sea level. The IR radiation absorbed by water vapor molecules would be very quickly and effectively radiated back into space. Conversely, the observed decrease in water vapor in these higher altitudes means more solar radiation reaches the ground or that part of the atmosphere where convection dominates as the mechanism for transferring energy. Because convection moves energy into the upper atmosphere where it can be effectively radiated out into space rather slowly, increased solar energy absorbed in the lower atmosphere or at the ground level lingers longer.
We see that the history of lower water vapor in the upper atmosphere is consistent with global warming, while increased CO2 is not. This lowered humidity of the upper altitudes combines with the increased incoming solar radiation and the decreased cloud cover to cause an increase in the amount of solar energy reaching the ground and sea level. The result is warming of the Earth's surface. Furthermore, the absorption of more solar radiation at sea level results in more long-wave IR radiation into space since the added energy delivered to the surface is partitioned among many molecules very quickly due to the very short mean free path length in the dense atmosphere near the ground and the many molecular collisions to divide that energy among many gas molecules, especially the most prevalent nitrogen and oxygen molecules. The smaller energy per molecule means they emit at longer wavelength, so outgoing long-wave IR radiation increases. Back in 1950, with higher humidity at higher altitudes, water molecules absorbed large amounts of energy and simply re-emitted that shorter wavelength radiation since at those altitudes the time between collisions is greater. The so-called greenhouse effect of CO2 is clearly not a major factor, being inconsistent with the data discussed above. This is consistent with many other arguments made on this blog that the catastrophic man-made CO2 emissions hypothesis is a failed hypothesis.
Given that socialists and Progressives have strongly advocated this hypothesis for many years and seen to it that climate change research was focused on the effects of increased atmospheric CO2 for many years with tens of billions of dollars of funding, it is incredible that so many fatal problems with this hypothesis have been documented. It is a wonder to behold that so much contradictory data has not long since caused this hypothesis to be abandoned in failure. It has become impossible to believe that the explanation for the continued backing for this hypothesis and the many claims that it is accepted science has any basis but a religious adherence to its usefulness to socialist elitists, radical environmentalists, and some crony businesses.
The data used was borrowed from a talk by Dr. Ir. Noor van Andel, the former head of research at Akzo Nobel, to the Dutch Meteorological Institute KNMI. The arguments I have used differ somewhat from his and they are simpler. Compared to his talk, this presentation is nearly free of climate jargon.
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