The carbon cycle: global warming explained

It’s Blog Action Day today. This year the theme is Global Warming. Since I’ve recently been in a discussion with people who still don’t believe it’s real, I decided to share with you the main arguments why I do believe Global Warming is a real threat. Let me start out with some basic facts I’ve learned in the many classes I took about the environment when in teachers college.

There is only 0.0383% CO2 or Carbon dioxide in the earth atmosphere. The amount of carbon dioxide in the air varies with the season because plants in the northern hemisphere use it to grow in summer, and their leaves decomposing in winter brings back carbon dioxide into the air in winter. This effect is strong enough to be measurable. Plant life in all its forms is the main part of the carbon cycle. Trees convert carbon dioxide into carbohydrates (aka sugars and fibers) during photosynthesis, releasing oxygen in the process. Plants and trees decomposing bring back carbon dioxide into the atmosphere, except when they turn into fossil fuels like oil, coal and natural gas (usually containing a lot of methane which is also a greenhouse gas btw).

The main issue with fossil fuels is that they took between 350 and 50 million years to form. We’ve been using them intensively for the past hundred years or so, and every decade brings a more intensive use as developing countries like China and India become more and more industrialized. The fact is, oil is a finite resource. It is not being produced by nature nearly as fast as we’re using it up. The economic result is of course rising oil prices. In 2004 a team of experts announced to the world that oil needed to be priced very much higher than the then standard of $40,- a barrel to make sure that alternative energy got developed fast enough to be able to take over when the oil really ran out. Since then oil prices have gone up, and then down, because of the economic crisis. Here are a few other articles warning about the same: 2009, 2005. We’re now back up to $75 a barrel. One should compensate slightly for the dollar being lower than it was in 2004, but still the difference is almost 100% and that with the economy not recovered yet.

What does that have to do with global warming? It’s a sign how much of the store of oil that the earth had kept for us is already depleted. And given that this store of fossil fuels also locked in millions of years of CO2, it’s reasonable to ask: what is the effect of all that CO2 being emitted into the atmosphere within a hundred years or so?

Well, what happens is this:

About a third goes missing, probably dissolving into the oceans. This may sound like good news, but CO2 plus water gives acid. And acid is NOT good for the many species of animals and seafood that have hard shells. But recently scientists found that in Japan the heating up of the oceans due to global warming is already having a measurable effect on the amount of carbon dioxide the seas can take in. That is: warmer water, less carbon dioxide gets dissolved into it. This may be good news for crustations and molluscs, but it’s not good for our climate.

The rest goes into the atmosphere. Some of it helps plant life grow faster, which takes it out of the air again, luckily.

But now for the clincher. If you didn’t believe that CO2 was being released into the atmosphere, you had to ignore a lot of commonly available knowledge. To deny that this Carbon Dioxide is a green house gas, capable of helping to increase the earth temperature you have to deny some less easily explained chemical facts. Luckily I’m a chemistry teacher, so I’ll do my best to explain.

The earth gets warmed by the sun in the day time. At night, heat radiation cools it off. Heat radiation is actually a form of invisible light, otherwise known as infrared. One of the capacities of any chemical is which forms of radiations it absorbs. In the visible spectrum we call that ‘color’ (roughly). When it comes to invisible radiation you’ll have to take my word for it: any substance has forms of light radiation it absorbs. Carbon dioxide absorbs infrared radiation. More carbon dioxide in the atmosphere, means more heat radiation gets absorbed by the molucules in the air, and that stops the radiation from going into space. As it hasn’t left our atmosphere, it’s still available as heat, and the earth doesn’t cool off at night.

Since this nightly cooling down has only an indirect effect on day temperature, but is more directly linked to greenhouse gasses, you’d expect the night temperatures to go up faster than day temperatures. And so it is.

Summing up: the line of evidence is clear. Carbon dioxide is a greenhouse gas that keeps heat energy in the earth system when the earth ought to cool down at night. We’ve collectively been sending a lot of carbon dioxide into the air in the past century, there is no reason to think that would not effect the climate. Recent evidence includes the disappearance of the polar bear, the last few years being the hottest in recorded history, despite the fact that we’ve now entered a low sun activity period. [More on sun activity and the climate.]

2 thoughts on “The carbon cycle: global warming explained”

  1. Enjoyed the global warming recap. I already “believe in” the science behind it, but it’s helpful to get a refresher.

    Are you familiar with biochar?

  2. I wasn’t but see biochar is a form of locking carbon into the soil by smoldering biomass. In the process, somehow, carbon from the air is contained IN the resulting charcoal. According to wikipedia the process produces more energy than put in – which is certainly a first as far as I know and therefor worth investing energy into.

    However, I’d personally like the simple solution of planting trees in dry regions in say Africa, India and China. You know: that would help the local climate as well as the world wide climate as well as helping retain a reasonable ecosystem.

    The primary problem here is, after all, industrialization and intensive farming.

    I’m mentioning the second because I’ve recently read we’re running out on phosphate, which is the primary nutrient used to make poor soils rich enough for farming. Running out on that means running out on food for the growing human population. On several levels we are, or are going to be, in deep trouble with food supply. Fish are being harvested at a rate nature can’t replenish. Oil is a finite resource and now phosphate is on the list of resources we’re going to have to worry about.

    I do hope all such issues are going to come high on political agendas everywhere. This requires a global solution and one that we ALL need to get behind.

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