Guest Post by Willis Eschenbach
Back in 1987, V. Ramanathan noted that we can measure the very poorly named “greenhouse effect”. This effect has nothing to do with greenhouses. Instead, what happens is that some of the upwelling longwave radiation from the surface is absorbed by “greenhouse gases” in the atmosphere, mainly CO2 and H2O. This absorbed energy, of course, is added to the thermal energy in the atmosphere, which is then radiated again with about half going to space and about half going back to the ground.
What Ramanathan noted is that to calculate the size of the “greenhouse effect”, you simply subtract the longwave emitted to space at the top of the atmosphere (TOA) from the longwave emitted upwards at the surface. Here’s Ramanathan’s drawing of the concept:
Figure 1. Drawing by Ramanathan showing upwelling surface longwave of 398.6 watts per square meter (W/m2), TOA radiation to space of 267.5 W/m2, and atmospheric absorption (greenhouse effect) of 131.1 W/m2. Note that Ramanathan has also calculated the absorption as a fraction of surface radiation (0.334, or 33.4% of radiation absorbed).
The use of a percentage to measure the “greenhouse effect” eliminates one of the variables. Where it is warmer the ground emits more radiation, so naturally more will be absorbed by the atmosphere. That means if we want to compare different areas of the earth, we need to use percentages instead of absolute values. Below are two graphs showing the percentage of the upwelling surface longwave radiation absorbed by the atmosphere, shown from two opposite sides of the planet.
Figure 2. Percentage of upwelling longwave absorbed by the atmosphere, Pacific-centered and Atlantic-centered.
There are a few things of interest here. First, where it’s very cold, almost no upwelling longwave is absorbed by the atmosphere. Second, in the cloudy areas around the equator, about half of the upwelling radiation is absorbed. Third, you can see the Gulf Stream along the east coast of the US …
Much is made by climate alarmists of the fact that the percentage of the upwelling surface radiation absorbed by the atmosphere is increasing. This indeed shows that the greenhouse effect is real … but it shows nothing about whether that affects the temperature. Figure 3 shows the rate of increase.
Figure 3. Change in absorbed upwelling surface radiation from March 2000 to February 2021.
Now, I entitled this post “A CO2 Puzzle”, and true to my word, here it is. The increase in the absorbed upwelling radiation is supposed to be from the increase in CO2 … but in fact, the increase in absorbed upwelling longwave is slightly less than half of what we’d expect from CO2. And that’s without the claimed increases in absorption due to methane and other minor greenhouse gases, from”water vapor feedback”, and from “cloud feedback”, all of which are said to increase the slope of the trend in absorption.
Figure 4. As in Figure 3, but also showing the expected trend from the increase in CO2 over the period.
So there’s the mystery. Between CO2, methane and minor greenhouse gases, water vapor, and cloud feedback, the percentage absorbed should be increasing far faster than it actually is … why isn’t it?
And what is the answer to the puzzle? I don’t know, other than to note that as I’ve pointed out in a number of contexts, emergent climate phenomena act to minimize factors that tend to warm the earth. However, I have no idea exactly what is occurring here, all suggestions welcome.
Me, I’m currently in Florida with my gorgeous ex-fiancee, enjoying the rain, the sunshine, and the pleasant and friendly people here. Our profound thanks to the most interesting and kind WUWT folks who have hosted, educated, and entertained us on our peregrination, you know who you are, much appreciated.
My best to everyone from the land of oranges and bikinis …
PS—Two things. First, I implore you not to turn this into a discussion of whether a cold object can warm a hot object, or whether the greenhouse effect is real. There are plenty of places for you to have those discussions. This is not one of those places, and I will snip comments that go over the line. And please, if you get snipped, don’t whine about censorship or the like. It is merely my effort to keep the conversation focused on the topic of the post, you’ve been asked in the strongest terms to stay away from those topics, and if you don’t, it’s on your head, not mine. Oh, and please, leave out the politics … there’s plenty enough division of opinion in the climate world, no need to increase it by including politics.
Second, as always, I request that you quote the exact words you are discussing, so that all of us can understand just who and what you are referring to.