An Act of Equalization – Get Up With That?

Guest Post by Willis Eschenbach

I am a picture guy. I understand the numbers, but not the table. I turn them into graphs and charts and maps so I can understand what’s going on. I have to rethink the total absorbed radiation on the surface. The total radiation absorbed by the earth’s surface is a mixture of long-wave (heat) and short-wave (solar) radiation. In my last post, Put it in reverseI was looking at the correlation of that absorbed radiation with temperature.

So, as a visual person, I created a global map of where this total radiation is being absorbed on the surface. But before showing that result, let me digress a bit about shortwave radiation (solar) and long wave reduced wave radiation (heat). (Note that “descending radiation” is radiation directed toward the Earth’s surface and “ascending radiation” directed toward space.)

Solar radiation begins to be relatively constant at the top of the atmosphere. That’s about 340 watts per square meter (W/m2) which is a 24/7 global average. It only changes by about ±0.1 W/m2 during the sunspot cycle.

Next, at any given time and place, somewhere between a little and a lot of incoming sun will be reflected by clouds and aerosols. The amount reflected varies by day, season, temperature, location, altitude, and local weather.

Next, the amount of sun remaining after reflection at that location, somewhere between a little and a lot of downward solar radiation is absorbed in the atmosphere, mainly as clouds, water vapor, and aerosols. (smoke, fog, volcanic aerosols, mineral dust). Again, the amount absorbed varies by day, season, temperature, location, type of spray, and local weather.

Finally, when the sun hits the surface, somewhere between a little and a lot will be reflected back into space by the surface itself. Again, the amounts reflected vary by day, season, water state (liquid compared to ice and snow), wind, ground cover, location, altitude, and local weather.

Briefly, The amount of sunlight absorbed by the ground varies widely across space and time on all scales.

Infrastructure radiation, on the other hand, is radiation emitted by something in the atmosphere above us — by greenhouse gases like water vapor and CO2, by aerosols, and by clouds.

The large difference in downwave radiation is due to different amounts of clouds, water vapor, and aerosols. CO2 is a fairly well-mixed gas, whereas, by contrast, water vapor can vary over short distances from barely to a large enough amount to condense. Again, the amount of thermal radiation emitted by water vapor, greenhouse gases, aerosols, and clouds varies with day, season, wind, location and local weather.

And like solar radiation, clouds are the big variable. Clouds are almost a perfect black body for thermal radiation. On a clear winter night when a cloud passes, you can feel the warmth immediately. And as above, the amount of thermal radiation emitted by clouds varies by day, season, temperature, location and local weather.

In short, just like the sun, The amount of thermal radiation absorbed by the earth’s surface varies widely across space and time on all scales.

So, with a preamble, here’s Figure 1, showing the total amount of radiation (shortwave + longwave) absorbed by the earth’s surface.

Figure 1. Map of 1° longitude by 1° latitude of total radiation absorbed by the earth’s surface.

I have to admit, I looked at that painting when I first made it, scratched my head and said, “How curious!”. I love surprises in science, and this is one of them.

Here’s what I find strange. The southern hemisphere is mostly water, with a rock cover at the bottom. It is very different from the northern hemisphere, where there is more land, and water instead of ice at the top.

From Figure 1, per square meter, the ocean is absorbing about 20% more radiation than land. So you would think that the southern hemisphere, with significantly more oceans, would absorb more energy than the northern hemisphere.

But it’s not. In fact, the two hemispheres are the same to the nearest tenth of W/m2… that’s why I scratched my head and said “That’s curious”.

Naturally, I’d like to know if this is just a coincidence, or if this hemispheric equality is a lasting feature of the climate system. So I looked at the changes over time. Below is the annual average for the period of CERES satellite data.

Figure 2. Annual average, total absorbed, short-wave and long-wave radiation.

More curious and more curious. Year after year, the total annual energy absorption of the North and the South is almost identical — half a year, the two hemispheres are within 1/10th of a percent (~half a watt per square meter) of each other. .

The long wave and short wave components are equally interesting. Each year, slightly more long-wave radiation than short-wave radiation is absorbed in the northern hemisphere. However, the opposite is true for shortwave radiation. Possibly due to the larger amount of ocean, in the southern hemisphere more solar energy is absorbed than longwave. In all cases, when long and short waves are added, the total radiation absorbed by the two hemispheres is almost the same.

Now, I start by saying that because both solar and thermal radiation are functions of many different factors, with clouds leading the group, they are constantly changing over time and space. So a priori, we have no reason to assume that the two hemispheres will absorb the same radiation at the surface, and any reason to suppose that they will not.

I mean, we have volcanoes and floods, droughts and wildfires and many things that affect longwave and shortwave radiation… and even so, each hemisphere receives the same amount of radiation, year after year.

Putting that oddity aside for a moment, climate can be profitably analyzed like a giant heat engine. It turns solar energy into an endless physical work that promotes the motion of the oceans and atmosphere against chaos and friction. These oceanic and atmospheric movements carry thermal poles from the tropics, where it is radiated into space.

This unexpected stability over time of the total absorbed surface energy clearly indicates that this is a heat engine with a governor. And not just one governor. The governor works in part by controlling the throttle valve of a climate heat engine.

A “throttle” is any mechanism that regulates the amount of energy entering a heat engine. In your car, the throttle is what is controlled by your accelerator pedal. Clouds perform that function for climate. They control how much energy goes into the system by denying some of the solar energy that gets there back into space. And not just a small amount. Hundreds of watts per square meter. Here’s an example, one-day record from a TAO buoy moored on the Equator at 110° West (east Pacific Ocean).

Figure 3. Solar energy diminishing over time of day, December 30, 1998.

You can see the clouds change the amount of solar energy dropping to a few hundred watts per square meter within an hour or so.

And this adjustment of incoming solar energy must be a major part of what’s behind the annual stability of the amount of solar absorbed by each hemisphere individually and by both hemispheres together.

My hypothesis is that a hierarchy of emerging climate phenomena, mainly in tropical oceans but elsewhere, regulates incident energy. As can be seen in Figure 3 above, a typical tropical day starts to clear.

Figure 4. Typical early morning tropical ocean conditions. Clear sky.

After passing a certain temperature threshold, the cumulus field is quickly established. This immediately reduces the amount of solar generated it on the surface.

Figure 5. Typical conditions of a tropical ocean in the late morning. The Cumulus field is growing. Cumulus clouds form on top of the ascending portions of the air’s circulation cells.

Then, when the higher temperature thresholds are crossed, some cumulus clouds develop into towering thunderstorms. These cause further reflective losses, as well as direct surface cooling.

Figure 6. Typical conditions of the tropical ocean from afternoon to night. The field of thunderstorms develops.

All these emergent transitions increase the amount of sunlight that is either reflected back into space or absorbed before it reaches the surface. And the time of occurrence, quantity and intensity of those phenomena are all regulated at the threshold temperature.

The common result of all of this is that as temperatures rise, clouds form in response and cut down on the total energy absorbed by the surface. The following graph shows a grid-cell scatter plot of temperature versus surface grid-cloud radiation (CRE). The surface net cloud radiation effect (CRE) is the average change in the total irradiance that falls to the surface due to the presence of clouds.

Figure 7. Scatterplot, gridcell according to gridcell temperature versus net cloud radiation effect (CRE). The grid cell size is 1° latitude x 1° longitude. There are a total of 64,800 grid cells shown above.

As you can see, when the temperature is high, the clouds work hard to reduce the energy reaching the surface. In many grid cells, the clouds are cutting out more than 50 W/m2 of sunken energy at the surface.

In any case, that is my explanation for why, despite the very different natures of clouds, water vapor, and aerosols, both in time and space, the total amount of radiation is halved. the annual absorption demand is the same. The climate phenomenon depends on the operating temperature threshold to limit the energy that can be absorbed.

I am pleased to hear alternative hypotheses about the unusual stability of absorbed radiation at the surface. Please don’t say “thermal inertia” unless you can explain how “thermal inertia” is controlling the diminishing amount of solar energy.

Late summer afternoon here in our redwood grove. Can’t see the ocean today, there’s fog at the coast, but no clouds here. My nine-month-old grandson cries in the kitchen, my daughter comforts him. My three-year-old niece explains how she dropped her sock in cat water. She wanted me to play the role.”City of New Orleans” on the computer. It’s done, lady, it’s done.

The sun was slanting across the house, hitting the tall redwoods visible through my window.

Time to go to bed for my daughter. She wants to fade away to “Mercury Blues“. I don’t complain.

Best wishes to each of you, may your life be full and full.


PS — When you comment, please QUOTE the exact words you are discussing. I can defend my word. I cannot defend your restatement of them. Thank.

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