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Controls of Climate on Geological Timescales

Geologist, Alasdair Skelton, explains how climate is controlled by solar heat, albedo and the greenhouse effect on geological timescales.
In 1896, Svante Arrhenius hypothesized that by burning fossil fuels- -we would make the Earth warmer. His reasoning was that when we burn fossil fuels, we release carbon dioxide. And carbon dioxide is a greenhouse gas. So, what are fossil fuels? Well, fossil fuels come from rocks, like this one.
This is coal.
Coal comes from plants that lived at the same time as the dinosaurs. Oil and gas are also fossil fuels. They come from rocks, like this one. When we burn fossil fuels, we release carbon dioxide to the atmosphere. Because carbon dioxide is a greenhouse gas, we make the Earth warmer. We are disturbing a geological system. In less than a century, we have burned up to half of all known fossil fuel reserves.
Those fossil fuel reserves come from rocks, like this one- -which are millions and millions of years old. There’s a clear imbalance of time. For this reason, climate change caused by burning fossil fuels is a geological problem.
So why do I say that? Well, climate change is caused by the burning of fossil fuels. Such as coal, oil and gas.
This is coal, a fossil fuel. It’s a rock. We are burning geological materials.
So, climate change is a geological problem. To understand climate change, we must understand what it is that controls our climate- -on geological timescales. There are three factors we need to consider.
Heat from the sun, the albedo effect and the greenhouse effect. Let me talk about them one at a time.
When the Earth gets more heat from the Sun, it is warmer. When it gets less heat, it is cooler. That could be because the Earth is just slightly closer to the Sun- -or just slightly further away on its orbital path. If we consider the Sun, and the heat from the Sun only- -the Earth’s temperature would be 6 degrees. But it is not.
Let’s take the second factor that is called the albedo effect.
To understand albedo, it’s useful to think about a mirror. A mirror reflects light. It also reflects heat from the Sun.
The albedo effect is the ability the Earth has to reflect heat from the Sun. The darker parts of the Earth absorb heat, but the bright, light-colored parts reflect heat- -contributing to the albedo effect. So snow and ice reflect heat, but oceans absorb heat. If we also consider albedo effect, the Earth’s temperature would actually be a lot lower. Because a lot of the heat from the Sun gets reflected back into space- -the Earth’s temperature would actually be -18 degrees centigrade. It’s not, so we have to consider the third factor. That factor is called the greenhouse effect. Now, the greenhouse effect… works a bit like a blanket. If I was cold, I might wrap myself in a blanket.
Why would I do that? To trap my body’s heat. Well, the Earth also has a blanket. That blanket is Earth’s atmosphere. In the atmosphere, there are several very important greenhouse gases- -making the greenhouse effect. One of them is carbon dioxide.
If we also consider the greenhouse effect, Earth’s temperature is then increased- -from -18 by 32 degrees, taking us to 14 degrees. That is the temperature Earth should have. But today, Earth’s temperature on average is more than 15 degrees. Why? Because we are influencing the climate.

This video begins at an quarry in southern Sweden. Here, Alasdair Skelton hacks out pieces of coal from a coal seam. He explains, that coal, oil and gas (fossil fuels) come from plants that lived at the same time (or earlier than) as the dinosaurs. This makes burning fossil fuels and therefore the climate crisis a geological problem.

This underpins the importance of understanding how Earth’s climate is controlled on geological timescales. This is by 3 factors:

  • Heat from the Sun which makes the Earth warmer.

  • The albedo effect which makes the Earth cooler.

  • The greenhouse effect which makes the Earth warmer.

Heat from the Sun on its own would give the Earth an average temperature of 6 degrees. The albedo effect (a measure of how much heat is reflected back into space) would lower Earth’s average temperature to -18 degrees. The greenhouse effect (a measure of how much heat is trapped by the atmosphere) raises Earth’s average temperature to 14 degrees.

Today, Earth’s temperature on average is more than 15 degrees. The extra one degree is human-induced global warming.

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