A few months ago, I was teaching a course called “Energy & Entropy” to students in their first year of university in Physics. Once a week we had this nice french setting called “colles”, where three students, with one white board each, try to solve an exercice for an hour. Because the teacher has only three students to interact with, there is a lot of room for discussions, and therefore, with motivated students it is possible to go a bit deeper and personal than in the classroom.
Sometimes I would just take nice exercices from good books, but sometimes I would feel inspired to write my owns, and that’s how it happened. I was flicking through a popular science magazine “Science & Vie” and ended up reading this article about geoengineering.
The idea laid out was quite elegant:
We observe that, because of the injection of more and more greenhouse gases in the atmosphere, Earth is warming. And several things point towards the alarming conclusion that rising temperatures are not a good thing. Therefore, we need to cool down Earth. There are two main categories of solutions:
- We stop emitting and start capturing greenhouse gases. Heat can better escape from Earth. Earth cools down.
- We reflect a part of the incoming sunlight. Less heat reaches Earth. Earth cools down.
Now the article details things a bit, focusing on one technological solution for each of those big categories of fixing global warming.
(1.) Carbon capture. We are bad a doing it, it is hard, it is expensive. Maybe we could alkalize the Oceans by pouring minerals in it, like magnesium, sodium or else. Indeed, alkaline Oceans absorb more CO2. But we do not really know what it could do to marine life. Apart from that, it is really a great solution, because there is almost no limit to how much carbon the oceans can absorb in this way, as long as we pour enough stuff in them.
So of course I start thinking: what? This is completely crazy, can’t we do anything else ?
(1.) (Carbon capture continued) Yes we can, we can plant trees! But trees mean less crops and then people cannot survive. Plus trees may actually reflect less light from the sun than crops, which means more heat. Or we could change the chemistry of soils, or use turbines to absorb CO2 but that is awfully expensive. And these solutions just pale in terms of efficiency compared with the Oceans’ alkalization.
So, literally, according to this article our best bet so far is to pour minerals in the Oceans to change their chemistry? Seriously? But wait, it gets better.
(2.) Dimming the Sun. We can put sulfates in the high atmosphere. It is not a greenhouse gas so it does not keep the heat in, but it does reflect a large part of the incoming heat from the sun. And this is very feasible. Comparatively cheap, and simulations say it could actually work. If we could reflect only one percent of the incoming light, we could stop global warming all together. A few thousands of planes per day to spread it. Compared to the daily traffic of around 100.000 planes, it sounds alright. Of course it could be a bit tricky to know how the winds will move the sulfates, and who will pay for it (which countries, or even companies?), or which countries could not want to make it happen because warm climates are better for tourism or whatnot. Couple challenges but we might figure that out right?
So I start thinking: oh well, that is not so bad a solution. What else are we gonna do anyway?
And I start writing an exercice for my students about the energy balance on Earth and how both ideas (capturing greenhouse gases or letting less sunlight arrive on Earth) make sense, from the point of view of the first law of thermodynamics.
I had a vaguely weird feeling about it. In a very unrealistic and sci-fi way I started imagining myself standing up the day the operations start. Everything is very silent, and, like everyone else in the world, I am looking up at the sky, and planes start pouring long clouds of sulfates in the air, making everything look a bit more dull, a bit more yellow, or is it grey?
But apart from that. The energy balance works, and capturing CO2 is too hard so. Maybe a grey cold world will do.
I think it took me a couple day to start thinking: WAIT WHAT?