[I originally posted this in the Coffee with Scott Adams community. I'm copying it here because I'm vain and want to see it again.]

Why I'm not worried about global warming:

According to geologists, large-scale ice sheets used to cover millions of square miles of the northern hemisphere. That theory is based on evidence, not on a prediction from a computer model which could have been curve-fit to produce the results that the programmer wanted.

Based on information gathered over the last 150 years, geologists say that ice sheets have grown and receded many times over the last million years. The periods of glacial expansion lasted much longer than the warmer periods. We're fortunate to be living during such a warm era, even if our descendants may have to move some cities farther inland in a hundred years.

The pattern of cooling and warming is apparently based on orbital fluctuations which affect the amount of sunlight received at the Earth's surface. If the pattern of glacial expansion and retreat continues, then sometime between next year and a few thousand years from now the winter snow over Canada and Siberia will not melt during the summer. The following winter, the snow will pile up even higher. Then people will say, "Oh, fuck! What happened to global warming? The news people said we were going to burn up!"

Then the Mexicans will say, "Mierda! The gringos are coming! Build a wall!"

And the Africans living south of the Sahara desert will say to the North Africans, "Don't even think about coming down here. You and the Europeans look alike to us. We don't want either of you."

The overheating of the planet has only occurred in computer models paid for by people who will get more grant money if they can show disaster in the not-too-distant future. If they make models where everything looks like it's within natural variation, will legislators who want to control the economy pay for them? Will the news media report predictions that don't fit the sky-is-falling paradigm?

Climate is the average of weather conditions over some arbitrary period of time. Any two periods that you compare will have some differences. That is climate change. 99.999% of climate change is innocuous.

As for the greenhouse effect, imagine a car parked in direct sunlight, with the windows rolled up and the engine off. The car is not a convertible. Sunlight passes through the windshield and the windows, striking the surfaces in the car, which causes the air inside of the car to heat up. The hot air would naturally rise, but the roof and the closed windows keep the air from convecting. The air is trapped. Denied the ability to transfer heat via convection, the air in the car gets increasingly hot, which is similar to the way the air in a greenhouse gets hot. The air outside of the car will generally be cooler than the air inside the car or in a greenhouse because the outside air can convect and circulate laterally.

The atmosphere does not work like a greenhouse. There is no roof trapping the air near the surface. Hot air will convect upwards, and that will create lateral circulation as the surrounding air moves to replace the air that moved upward.

Mountains can have a similar effect to the closed doors and windows of a parked car. They can impede circulation between the air in the bowl of a valley and the air on the other side of the mountains, but the air can still convect upward and can still flow above the mountains, so even in those circumstances the atmosphere and a greenhouse are dissimilar. And valleys where lateral air circulation is limited are a very small portion of our planet's surface. On the vast majority of the planet's surface, convection and lateral air movement are unimpeded.

Carbon dioxide can intercept radiation from the planet, slowing the radiative transfer of heat energy into space. When a molecule of carbon dioxide gets warmer from that intercepted energy, it will immediately begin conducting that energy to the oxygen and nitrogen molecules with which it collides (according to the law of conservation of energy), and the warmer air can be convected upward where it will be cooled when colliding with other, cooler molecules. The oxygen and nitrogen molecules that are thus warmed will immediately begin radiating a portion of that heat energy outward, and some of that energy will be radiated directly into outer space.

Nitrogen and oxygen comprise 99% of the atmosphere. The atmospheric carbon dioxide level is about 400 parts per million. That's 0.04% of the atmosphere. It is a trace gas that is essential for plant life, and therefore essential for our own lives. It is not pollution.

Imagine standing in a room with a flat, glass ceiling, with a light suspended several feet above the ceiling. Imagine someone emptied a large box of ping ping balls onto that ceiling until there was a single layer of ping pong balls completely covering it. You'd be able to see gaps between the balls, but the balls would block most of the light.

Now imagine another load of ping pong balls were dropped onto the first layer until there was a complete second layer covering the first layer. You would be able to see less of that second layer than of the first one, and you'd see less light coming from above. That second layer would make less difference than the first one, but it would have a noticeable effect. Each succeeding layer that was added on top would make less and less difference because of the lower layers. In that same way, adding more carbon dioxide to the atmosphere has a decreasing degree of effectiveness regarding heat retention than the previous levels. The carbon dioxide at the lower levels will intercept the radiation from the planet, and the upper layers would have less and less effect.

Carbon dioxide isn't going to lay flat like a bunch of ping pong balls, so that example isn't perfect, but it illustrates the general principle of additional quantities having a decreasing effect.

There is a limit to the amount of carbon dioxide that humans can safely breathe. According to this page from the CDC (https://www.cdc.gov/niosh/pel88/124-38.html), there are studies indicating that continuous exposure to levels of 15,000 ppm to 30,000 ppm produces few if any adverse affects. To err on the side of caution, OSHA sets the limit of continuous exposure during an 8 hour period to 5,000 ppm (https://www.osha.gov/annotated-pels/table-z-1). We're at about 400 ppm in the atmosphere. It could increase by a factor of 10 and still not be directly harmful to our health.

If we ever do have to lower the carbon dioxide level in the atmosphere, the U.S. by itself has the financial resources to irrigate every desert on Earth. But we wouldn't have to act alone. The resulting plant life that could be grown in the deserts could pull more carbon dioxide from the atmosphere than I know how to calculate, and it could do so in just a few years.

If carbon dioxide in the atmosphere rises to 4,000 ppm, and if after irrigating and sowing plants in every desert those plants don't bring the level of carbon dioxide down to less than 1,000 ppm after ten years, I'll wash and dry the laundry of everyone on Earth for a week.

Can humans affect the average global temperature? Of course.

A city built in the middle of a hot desert will be cooler than the surrounding desert because of vegetation and open water. Las Vegas is one example of such a city.

A city built in a temperate zone surrounded by forest will be warmer than its surrounding area because of the asphalt and concrete in the city. That describes most cities in the U.S.

The air above paved roads is also hotter than the air temperature above the surrounding areas.

Those man-made changes create a greater warming effect than a cooling effect, and that affects the global average. But not by much. Seventy percent of the Earth's surface is covered by water, and the portion of the Earth's land surface that is urbanized (and paved) is still very small.

According to infoplease.com (https://www.infoplease.com/math-science/weather/record-highest-temperatures-by-state), more than half of the states in the U.S. had their highest recorded temperature before 1940. If the Earth's atmosphere is warming, it's taking its time about it.

If the temperature gets significantly warmer (with or without human aid), it will be gradual. There will be plenty of time to rebuild farther inland, like people did when the sea level gradually rose thousands of years ago. When you have years to adjust to a change, that's not a disaster or an emergency. It's an inconvenience.

There are potential climate disasters worth worrying about, like the Yellowstone supervolcano. If the Yellowstone supervolcano explodes again the blast could eject 250 cubic miles of debris into the atmosphere. Aside from the disaster of the blast wave itself, the particulates in the atmosphere could reduce the sunlight reaching the Earth's surface, possibly for years. It could cause ice sheets to form, and it could cause crop failures that might result in billions of people starving to death. Keeping that from happening is an important problem to solve.

The squawking about anthropogenic global warming and its dangers has been going on for thirty years now. If the people of Grand Cayman Island (see photo) haven't seen enough change in the last thirty years to cause them to abandon their island, then maybe, just maybe, the "anthropogenic global warming"/"climate change" emergency is just a song and a dance to mesmerize the willing believers. With enough believers properly conditioned, the government could take more of everyone's money and their freedom too. And that seems to be what some people want.

But not me.