I’ve recently been reading several books about our environment, atmosphere, Earth system science and climate change, and I’ve been learning some new things. Things that I feel I should have known but just hadn’t bothered to educate myself enough. At least that’s changed now. One of the amazing things that I didn’t know is that the Earth has basically had an effective natural thermostat in operation for about the last 10,000 years and, if it wasn’t for this, the Earth wouldn’t be habitable for beings like us. Unfortunately, humans are now in the process of breaking this natural thermostat.
First, some information on CO2
You hear lots of things about “greenhouse gases” in the conventional media. Well the Earth has had greenhouse gases in its atmosphere for a very long time and, if it wasn’t for these greenhouse gases, the Earth would be a frozen planet. Carbon Dioxide (CO2) is one of the important greenhouse gases, but how does all this work?
Most of the heat we have on this planet comes from our Sun and most of that heat gets though to the ground and oceans and heats them up. We know this is true as we can feel the heat ourselves when we’re out in the sun. Once the soil and the oceans heat up, they radiate heat energy back into the atmosphere and all this heat would be lost back out into space if it wasn’t for greenhouse gases like CO2. These gases absorb the heat that is being radiated back from the Earth’s surface and basically hold the heat in the atmosphere. If we didn’t have greenhouse gases (like CO2) in the atmosphere, we’d lose most of the Sun’s heat back into space and the Earth would be very cold.
You might ask why the greenhouse gases in the atmosphere absorb the heat being radiated back from the Earth but not the heat as it comes from the sun. This is related to the frequency of the electromagnetic waves transmitting the energy. When the ground heats up and radiates heat, it does this with lower frequency electromagnetic waves (like infrared) than that which is transmitted from the sun (which is mostly in the visible light and ultraviolet part of the spectrum). The greenhouse gases tend to absorb this lower frequency energy radiated back from the Earth but not that transmitted from the sun.
Rather than talk about greenhouses, I prefer to think of the atmosphere acting like a blanket, the type we’d have on our bed at night. The CO2 holds the heat for us. If there’s a lot (relatively) of CO2 in the atmosphere, then it’s like having extra blankets on the bed and we’ll get very hot. If there’s not much CO2 in the atmosphere, then it’s like not having enough blankets and we’ll get cold. So how, over the recent thousands of years, has the Earth been managing these blankets (like a natural thermostat) to keep a temperature range suitable for liquid water and life?
How does the natural thermostat work?
From what has been said above, it’s quite simple that when the Earth has more greenhouse gases in the atmosphere, it will heat up. When it has less it will cool down. That’s the thermostat mechanism, but how does the concentration of greenhouse gases change in order to regulate the temperature and keep it fairly constant?
Well, as the atmosphere heats it can absorb more water vapour (warmer air can hold more water vapour) and hence create larger amounts of rainfall. This additional rainfall causes more weathering of the rocks exposed on the Earth’s surface and it just so happens that when “silicate” rocks are weathered, CO2 is absorbed in the chemical reaction that accompanies the weathering. So CO2 is naturally absorbed back into the Earth and the oceans. As the CO2 is absorbed, it’s like taking some of the blankets off the Earth and the atmosphere cools again. Now less water vapour can be held in the cooler air and we have less rainfall, less weathering, and less CO2 is absorbed.
What causes CO2 concentrations in the atmosphere to rise naturally? One of the major natural causes is volcanic eruptions which can spew large amounts of CO2 into the atmosphere. Hence the atmosphere will get hotter, causing more rainfall, more silicate rock weathering and more absorption of CO2 back into the ground and the oceans. A natural thermostat process.
What’s happening today?
Unfortunately, us humans have broken the natural thermostat because we’re putting much more CO2 into the atmosphere than can be handled by the weathering systems and, on top of that, we’ve removed much of the planet’s forests that are another way for CO2 to be removed from the atmosphere. The atmosphere is getting warmer, it’s causing more rain to fall (note the severity of floods in recent years), which is causing more silicate rock weathering which absorbs CO2, but it can’t keep up with the rate at which humans are placing additional CO2 into the atmosphere. So the atmosphere is getting warmer, and the constant addition of CO2 means it’s just continuing to get warmer and warmer. We’re adding more blankets even though we’re already too hot.
Where to now?
We’ve done a lot of things badly in the past but we know the science well know. We could argue that we’ve known the science for at least 50 years but haven’t acted on it correctly. That’s true, but that doesn’t help us much now. Today, we know the science very well and today is the only day we can act.
For whatever reason, the Earth happened to have a very effective natural thermostat in place for about the last 10,000 years (See Kolbert, 2021, Chapter 3, chart on page 196). The additional CO2 being added to the atmosphere by humanity is now overpowering this natural thermostat. Can we reduce our pollution enough to allow the natural thermostat to work again? Or can we find another way to regulate the greenhouse gases and keep the atmospheric temperature within a desirable range?
Really, the only thing we can do in the short term is to stop putting more CO2 into the atmosphere, or to find a new way to remove it from the atmosphere. We have to try everything and we have to do it fast. We have to start taking the blankets off or all of life is going to overheat, and quite soon.
From the personal point of view, every single person can ensure that they are not wasting anything, not wasting any energy and reducing their own consumption. Could we all use 10% less energy and stuff in the next year? Probably. It shouldn’t be too hard (see Use 10 Percent Less).
Some favourite books I’ve read recently
Lenton, T. 2016. Earth System Science – A Very Short Introduction. First Edition. Oxford University Press.
Kolbert, E. 2021. Under a White Sky – The Nature of the Future. London: The Bodley Head. Penguin Random House.
Maslin, M. 2013. Climate – A Very Short Introduction. First Edition. Oxford University Press.
Palmer, P.I. 2017. The Atmosphere – A Very Short Introduction. First Edition. Oxford University Press.
Smil, V. 2017. Energy – A Beginners Guide. Second Edition. Oneworld Publications.
Smil, V. 2021. Numbers Don’t Lie – 71 Things You Need to Know About the World. Penguin Books.
Wallace-Wells, D. 2019. The Uninhabitable Earth – A Story of the Future. Penguin Books.
Peter,
This is a great article! I wish I was still teaching. I would have asked to use this article as a handout for every one of my students.
Thank you for sharing information from books you have read. You are such a talented and gifted writer!