Imagine you’re at the petrol station filling up your car, when a splash of petrol hits the ground.
The last time these atoms saw the Sun was 300 million years ago, when the world crawled with millipedes over 8 feet in length and dragonflies flew with 30 inch wingspans through a vast global swampland.
This was the geological period known as the Carboniferous.
This dramatically different world was in largely a consequence of a different atmosphere, when both carbon dioxide and oxygen had much higher concentrations than we’re used to today.
More oxygen allowed the ancestors of today’s insects to grow gigantic proportions – long before mammals or even dinosaurs existed.
Today, most of these extra gasses have long been pulled out of the atmosphere by natural processes. They now exist trapped in rocks, the ocean, in soil, and in fossil fuels like petrol.
Burning fossil fuels releases one of the reservoirs of these gasses, returns them to the atmosphere, and as a consequence these ancient atoms are now changing our atmosphere and shaping our 21st Century.
At first glance carbon dioxide doesn’t look like much. Much like oxygen, it is a colourless, odourless gas that is a natural part of our atmosphere.
But the two are invisible partners in an immense dance between all life on the planet that’s been going on for hundreds of millions of years, older than even the 8-foot millipedes.
Animals breathe out carbon dioxide, plants absorb it. Plants emit oxygen, and animals breathe it in.
You could say that the cycle starts within plants, where they use carbon dioxide in ‘photosynthesis’.
They pull it out of the air and mix it with water from the soil.
Using the energy of the Sun that hits their leaves they break carbon dioxide molecules into their components, which are carbon and oxygen atoms. Then they recombine them in a different way, making oxygen and a new chemical called ‘glucose’.
The equation for photosynthesis. Source: BBC
Plants releasing bubbles of oxygen into the atmosphere.
Glucose, which now carries some of the Sun’s energy in chemical form, is moved to young branches and leaves where it’s used as a LEGO block to build new plant cells.
When animals eat plants (or other animals), they redirect glucose and its energy into their own growing cells.
Image source: BBC
Every time we inhale, the caustic oxygen in the air attacks glucose molecules in our blood and tissues.
This is called ‘respiration’. It’s a reversal of photosynthesis, and it allows animals to access the Sun’s energy that was stored by plants.
Just like burning a log of wood, respiration produces heat plus carbon dioxide as waste, and the cycle is completed.
Plants and animals have evolved in this way to sustainably reuse each other’s waste for (almost) their entire history.
Image source: Photosynthesis Education
While there aren’t any new oxygen and carbon atoms being made on Earth, the portion of them in that’s in the air can change.
The Carboniferous, which was the geological period with the giant millipedes and dragonflies, was about 300 million years ago. Back then, there was more oxygen and more carbon dioxide in the air.
Because insects have a different and less efficient respiratory system than animals that have lungs, the higher level of oxygen meant they could access more energy than they can now, and they grew to enormous sizes.
Meanwhile, the higher carbon dioxide levels in the air acted as a thick chemical blanket that trapped sunlight in the atmosphere. This heated up the Earth, turning almost the entire planet into a sprawling swamp that was the habitat of these giant creatures.
The Carboniferous. Image source: The Economist
But the greatest legacy of the Carboniferous came from something tiny.
Plants had only just evolved bark, and they used its strength to grow tall and beat other plants into the sunlight. It’s the first time on Earth that there were forests of plants (although in the past there have been forests of fungi).
But their invention of bark was still so new that no bacteria, fungus, or animal had evolved to digest it and access the glucose hidden inside.
So when the trees died and fell into their swamps, they stayed there.
They never rotted, because there was no bacteria to rot them.
Image source: Mary Parrish at the Smithsonian Institution
Millions of years later, bacteria and fungus worked it out. Nowadays a fallen tree rots through in a few years, and it’s energy is returned to its ecosystem.
But this evolutionary lag between bark and digesting it was a small but crucially important thing in the history of the Earth, like the proverbial butterfly’s wing that causes a hurricane.
300 million years later, it allowed human beings to create the Industrial Revolution.
When layers of dead trees piled up in the swamps, they sunk under the silt until they were beneath the ground.
After millions of years they were compacted by the internal pressures of the Earth and changed forever. Under the pressure of the Earth, glucose fused together to create a mix of hydrocarbon chains, also known as coal, crude oil, and natural gas.
The energy that the plants once absorbed from the Sun was still in there. But it was now changed into a ‘fossil fuel’, the most efficient and energy-dense fuel source ever discovered. To release the energy, all you had to do was burn it.
It sat in the ground more or less untouched until around 1760, when we invented the coal powered steam engine. What followed was the greatest period of economic change in human history, as we used the energy of fossil fuels to make machines work for us.
But just like with respiration, burning fossil fuels reintroduces carbon dioxide into the air. Except that this carbon dioxide has been trapped in a time capsule.
300 million years ago it was in the Carboniferous air, where there was so much carbon dioxide blanketing the air that the Earth was a global swamp. But since the Industrial Revolution, burning fossil fuels has spread from a few European countries to the entire world and simultaneously, our population has exploded. The the amount of carbon dioxide in the atmosphere since then has increased by a whopping 45%.
The effect on global temperatures has been dramatic, and even now has permanently changed our climate. We are already seeing melting ice caps and rising water levels, as well as changes in rainfall patterns and the intensity of storms as a result of more heat being in the atmosphere.
Our actions now and in the following decades will determine how severe these effects will be.
The best visualisation that I’ve come across of the dramatic changes caused by atmospheric carbon dioxide is embedded below. If it doesn’t work, click here to go through to XKCD and see it.
Originally posted 2018-07-15 19:57:03. Republished by Blog Post Promoter