Heat, Energy, and Climate: The Three Amigos

I’m going to start off by saying that I don’t care if anyone reading this article believes in man-made climate change or thinks it’s a scam. I’m not here to champion anything, I just feel there is a lot of misunderstanding of the topic because everyone discusses it 3 or 4 levels above the fundamental points of understanding. So that’s what I’m here to talk about, the absolute, bog basic fundamentals.

Now here’s my disclaimer, I am not a climate scientist. I don’t study ice cores or geological historical climate records. I am a materials engineer so what I understand is Heat so that’s what I’m going to focus on.

Some of you might remember seeing a chart like this on your high-school science room wall. The bottom most part will come into play later.

Thanks to the Laws of Thermodynamics, every bit of energy contained or used by any object or process eventually turns into “waste heat” (thanks entropy you greedy bastard). “Waste heat” is just a term for any form of energy emitted due to inefficiency in a physical process. Rubbing your hands to warm them up on a cold day is you making “waste heat” due to friction between your palms. This “heat” doesn’t actually even need to be heat, it can be basically any kind of energy on the electromagnetic spectrum, from infrared to radio-waves, even visible light or ultraviolet and beyond. Generally it doesn’t matter what kind of energy it is, so we will just call it Heat.

But! There is one that is relevant to our conversation where it matters that the energy isn’t heat to begin with that is quite important. Firstly though we need to talk about the very basics of heat balancing.

Fundamentally everyone should understand that all the energy that is pumped into the biosphere has to be pumped right back out otherwise the planet would just heat up continuously like a tea kettle on a stove. This act of shedding heat at the same rate it comes in is called the Energy Balance. It’s like pouring water into a jug with a hole in it, if it goes in faster than it comes out the jug fills up(planets heat goes up), if it goes in slower then the jug empties (planet cools off). Super simple stuff right? Now we don’t ever want the bucket to be either full Or empty, but rather some level in between. Too hot or too cold and all sorts of problems occur for us, but right at the balance point things are comfortable and predictable with all the very interesting things on our planet working fine.

There are all sorts of interesting things that happen inside the “bucket” that help manage how much heat is in any one place on the planet, but to really understand those we need to talk about the energy that is coming into the biosphere and leaving the biosphere. There are three main sources of incoming energy: Human activity, heat from inside the planet, and energy from the sun. Two of them are essentially insignificant compared to the third.

All human activity produces about than 20 Terawatts of power. It’s probably less than that but we’ll just assume 20 for easier math. The heat from the inside of the earth is measured at approximately 47 TW of power. all that power is what drives plate tectonics, makes earthquakes and provides the energy to erupt volcanoes all over the planet.

And other much less destructive phenomena. Image from iStock

But, here’s where I tell the climate skeptics that they are right. Any heating of the planet is primarily driven by the sun. Due to the fact that the sun deposits approximately 173,000 Terawatts of power on the surface of the Earth. The combined impact of humanity and the Earth itself on the earth’s heat balance amount to a measly 0.04% of the total input. However, the climate skeptics are not totally right but to show how, we need a very small lesson on quantum mechanics and blacksmithing.

Everything in the entire universe has a temperature above absolute zero. That means that everything in the universe has some amount of energy. And as I said earlier, thanks to entropy, that means that everything is slowly releasing that energy as “heat”. But what kind of heat it releases as is dependent on the objects temperature. This is where the blacksmithing comes into this. I’m sure you’ve heard about things becoming “red-hot” or “white-hot”. It’s a pretty common vernacular that smiths have been using for thousands of years to basically eyeball the temperature of the metal they are working with. As the metal moves through the colours of red-yellow-white the smith knows generally what temperature the object is at. But it took until we figured out quantum mechanics is to really nail down the rules behind this behaviour.

Graphs are how people learn things best right?

These are Blackbody Radiation curves. They are how we know what temperature things are by measuring the amounts of the different wavelengths of light that they emit. So knowing that it is possible to compare the incoming heat from the sun to the outgoing heat from the earth due to their blackbody curves.

Climate change in a nutshell right here. Image is Figure 2.2 from these lecture pages

So here we see a breakdown of the incoming heat from the sun as the 6000K curve, and the outgoing energy from the earth as the 255K curve. Below those curves is a tiny bit of chemistry. These lines show how much of each wavelength is absorbed by certain gaseous molecules in the atmosphere. there’s more information here than necessary so I’ll highlight the two important parts.

The green box on the left shows how the incoming energy from the sun pretty much passes through the atmosphere unmolested. Which is good because otherwise it would be very dark all the time. However the thinner red bar on the right shows how a huge portion of a specific band of infrared wavelength heat is absorbed by carbon dioxide at all levels of the atmosphere. And that is the important bit because all the heat in that band is being kept in the atmosphere until it can radiate away as either lower energy heat, or higher energy heat. And what helps determine which way it goes is dependant on how Much CO2 there is in the atmosphere.

The less CO2 there is, the more heat each bit of CO2 absorbs, which as we said shifts it’s curve to higher energy. This means that the amount of heat in the atmosphere saturates quicker and the CO2 is more likely to radiate it away at higher energy levels on the left side of the red box, which are not absorbed as well by other gases in the atmosphere. However, the more CO2 in the atmosphere, the longer it takes to saturate and get those energy levels pumped up. Meaning the heat is more likely to radiate out in lower energy bands that are on the right side of the red box which are almost as efficiently absorbed by other airborne molecules like water.

Thank you Matthew.

I know it seems like a tiny sliver of energy, but when you are dealing with the huge numbers that we are, even a tiny sliver can actually be an enormous amount. If the excess CO2 in the atmosphere absorbs just 0.1% of the heat being radiated away from the surface, that would be equivalent to our civilization producing 10 times the heat it does now. All that heat is just hanging around in our biosphere for however long it takes to radiate away.

And the longer heat sticks around in the atmosphere, while more heat is being pumped in by Mr. Golden Sun. It means that the temperature of the atmosphere starts to rise. And as anyone who lives in a tropical climate can tell you, as the temperature rises, there can suddenly be a lot more humidity. All that water traps more heat, which just like CO2, the more of something there is then the longer it takes to get saturated with heat so it just keeps radiating it out in the wavelengths that it is easily reabsorbed.

The important thing about the whole climate change thing is that it’s not a question of whether it is man made or natural. What we are experiencing is humanity finally having the energy at its disposal to purposefully affect the environment around it on a global scale. We now have the knowledge and capability to change how the heat balance stabilizes and thus steward our planet to the benefit of everyone and everything on it. How we do it doesn’t matter. Why we do it doesn’t even really matter, the only important thing is that we do do it. Because if we have the ability to improve the lives of those around us at no detriment to ourselves and we don’t…

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