Friday, September 22, 2023

Climate change is about entropy

 Veritasium has a briliant video explaining entropy

Entropy always increases if anything at all is happening. It is tempting to think that the universe wants to increase entropy as fast as possible. While this is not true, it often seems like it is. So I'm going to personify the Universe with that motivation.

Living things, including us, are little islands of low entropy. We use energy to create that low entropy state while increasing the entropy of the wider environment at a faster rate than would otherwise occur. It seems as though the Universe invented life to speed up entropy production. Then it invented intelligent life to speed it up even more. And now it has invented social co-operating civilised life forms to really put the foot to the floor of entropy production.

When the carbon was in the ground and the oxygen was in the air, that was a lower entropy state. When we combine the carbon with the oxygen we increase entropy. What we get directly is energy, and what we do with that energy is to create pockets of low entropy, which we call civilised life. Whether the pocket of low entropy is a car or a baby or a movie, it is in an organised and differentiated state which is the complete opposite of the high entropy mess that the Universe will eventually make of everything.

It won't be enough to stop burning carbon, we are going to need to reduce the carbon in the air to get back to a comfortable interglacial climate. The correct way to look at this is that we want to reduce the entropy of the atmosphere. The reverse of what we have always done. You need a lot more energy to reduce entropy than you got out of increasing it in the first place. Where is that energy going to come from?

The Sun sends us low entropy energy and the Earth emits high entropy energy, and this allows life to make its pockets of low entropy. We can use power from solar and wind and hydro to take more and more of that bounty that life on Earth depends on. Luckily we don't have to do this.

In the enormous energy released in supernova explosions and other astronomical events, tiny pockets of low entropy are created in the form of radioactive elements. We can extract that low entropy by making those atoms decay sooner than they naturally would. That is fission energy. We can also mimic stars by increasing the entropy of small atoms by merging them into slightly bigger ones. That is fusion energy. These are energy sources that the rest of life on Earth doesn't use. By switching to these energy sources and giving the sun back to other life forms, we can recreate the bountiful world that we have gone so close to annihilating. Let's do it.

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