Eli5 how did fossil fuels damn the world? I learned about coral reef deaths in 7th grade, I’m now 30

There is an interesting aspect to point out. The CO2 content of the atmosphere is actually very low. It’s now 421 parts per million (ppm), or about 0.042%.

In pre-industrial times, it was 280 ppm (0.028%)
By 1950, it had only risen to 310 ppm

Those making climate denial arguments in bad faith will try to tell you “CO2 has only increased by 0.14%“. Do not be fooled by this idiocy. The increase is 50%.

Very long, because I like explaining through metaphor, but I promise there’s no scientific jargon so bear with me:

CO2 is one carbon atom + two oxygen atoms. Oxygen is easy to find. So is carbon. Every time you burn something what you’re really doing is adding oxygen to carbon and creating CO2. The oxygen comes from the air. The carbon comes from the ground.

Every living thing is made of carbon. Trees are carbon. And when trees and other living things die and spend a long, long, long time getting pressed by the earth, they turn into oil–and that oil is made of carbon too.

But where did that carbon come from originally? Funny enough, it came from the air. Plants don’t breathe oxygen, remember, they breathe CO2. They breathe out oxygen. So what did they keep? They kept the carbon. And they used that carbon to grow.

CO2 is a greenhouse gas. Others have explained it better in the comments, and there are many YouTube videos explaining the greenhouse effect, so I won’t go into it here. What confuses many people is that everything we’re doing has always been there, so why is it bad now?

It’s bad because plants spent hundreds of millions of years collecting carbon from the atmosphere through CO2 and putting it into the ground. Think of it like money. Imagine an immortal billionaire starts collecting money, slowly, forever. And then one day that immortal billionaire decides they’re sick of the money and they dump it all into the economy. They give everyone their money. What would happen? Easy: chaos. The worth of everything would become fucked. The value of money would become fucked. The relation of our money to everyone else’s money would become fucked, and what even is the point of working anymore if everyone is rich? But if no one’s working then who’s making the things we’re buying?

Everything became fucked because the economy, although incredibly complex, is sensitive–in fact, it’s sensitive because it’s complex. It requires a delicate balance where everything works as it should with only the kind of minimal upsets that it’s used to. Eventually, in this scenario, the economy will rebalance. But that balance will be different. Maybe, after everything is said and done, bananas will be $50 a bundle and the US will have twice the number of people and farming won’t exist as a job, it’ll be outsourced to Ukraine. It’ll look different, but it’ll rebalance.

What we’re doing is the same thing as that billionaire. We’re releasing a massive reservoir of CO2 (and methane, and other greenhouse gases) to a very well-balanced planet–that is to say, economy–and fucking it all to kingdom come because that balance cannot handle it.

Just like an economy with a sudden flood of money will compensate to a new normal, so will our climate. But that new normal will be devastating to us. Everything alive requires the balance we’re used to. The new balance that the Earth will eventually achieve will cause the death of everything, except for the few organisms that adapted fast enough. But we won’t be one of them. New life will rise again, adapted to that new normal, and we won’t be part of it, and the world will never look the same again.

P.S.: This didn’t fit anywhere else, but this process, once it gets going, is very difficult to stop. It feeds itself. For example: when things decay, they release CO2, which warms the earth, which causes things to decay faster, which causes things to release CO2 faster, which causes… That’s what the runaway part of the runaway greenhouse effect describes.

Fossil fuels are a huge reservoir of carbon. When we extract this carbon and put it into the atmosphere as carbon dioxide through burning it we change the composition of the atmosphere.

The atmosphere is generally transparent to solar radiation. So what happens is sunlight travels through the atmosphere and smashes into the surface which causes the surface atoms to vibrate and release that energy as heat.

Carbon dioxide is opaque to infrared radiation (heat) so the sunlight is unobstructed on entry but the resulting thermal radiation is now being blocked more than it was previously due to the presence of more carbon dioxide.

The effect of this is that the effective altitude where heat is radiated into space is raised which lowers the efficiency of the process because the temperature is colder at a higher altitude. The net result of this is that temperate of the atmosphere has to increase to balance the reduction in radiative cooling and there’s your global warming and increased weather instability due to there being more energy in the atmosphere.

The most important part of the science is human behaviour and global politics. Humanity has known this would be a problem for over a century, and has had the solutions for 50 years or more. But the shifts in industry required would make a different set of people rich to those who got rich off exploiting fossil fuels, so they used some of their vast wealth to bribe politicians and pay media to brainwash the public. Thus the issue is clouded in deliberately poor education (as shown by the fact that you don’t know how it works and your coworkers think it’s fake…), nonsense “scientific controversy” or “it’ll be too expensive to fix” or “we need to do something but not like that”, etc etc etc.

Excess carbon dioxide in the atmosphere is like a “blanket” over the earth that warms things up.In terms of coral reefs a lot of the excess Co2 gets absorbed by the oceans, increasing acidity. There already is a great example. The planet, Venus’s run away greenhouse effect makes it the hottest planet in the solar system despite being the 2nd closest from the sun. Venus’s atmosphere is primarily carbon dioxide.