For a few weeks I have been following the highly recommended scientific dissemination portal by geologist Andrea Moccia: Geopop. There are several videos in which he addresses the issue of global warming but one of them, of which I want to summarize the content, struck me. The ability of the planet earth to manage the quantities of carbon is explained, by way of example, with a 750ml bottle of wine. Since I like beer and I like the idea of a 750ml beer even more, I’ll bring you the same metaphor in the form of hops. Let’s imagine the earth’s atmosphere as a 750ml bottle of beer. Let’s imagine then filled with 750ml of beer (possibly an amber beer), that is the quantity that the bottle is able to manage. Then take a small glass (the one that you pours out, filled with genepì, inside beers on tap) and pour it into the bottle. Immediately there is a problem: the additional genepì overflows from the bottle.
There are still several people, Andrea explains, who see natural sources of carbon dioxide as proof that man-made CO2 is not a big problem. But let’s think about the bottle: the problem is not that the bottle contains 750ml of beer, since it is specially designed to handle that amount. The problem is that extra shot. The same concept, Andrea continues, applies to our emissions. The problem is not the 750 gigatons of carbon that the atmosphere contains and is capable of handling. Those 750 billion tons, being emitted naturally, have found an impressive natural balance and remained almost stable over time. The ocean, for example, releases about 90 gigatons of carbon into the atmosphere every year but absorbs about 92 from the atmosphere. Plants, Andrea continues with the examples, absorb about 120 gigatons through chlorophyll photosynthesis, but they release, at the same time, 59 with the respiration of plants and 58 through the decomposition of soils. You don’t need to be Einstein to notice that the amount of carbon released into the atmosphere is almost the same that the atmosphere loses. In other words, the biosphere, the lithosphere and the hydrosphere are capable of removing the same amount of carbon from the atmosphere that they release in it. An exceptional natural balance. Now, returning to the bottle of beer: it is as if this bottle exchanges the same quantity of liquid with other bottles, always letting out as much of it as it lets in, keeping the level stable. The problem is those 8 or 9 gigatons of carbon that we release into the atmosphere each year through human activities. This “small” quantity (because it is small, Andrea emphasizes, compared to the natural one) is a pain in the ass for the natural balance because the system cannot manage it. Furthermore, the consequent serious problem is that once the balance is broken it is not possible to reverse it, at least not in human times. The issues are complex, but the key message is this: “The problem is not the bottle, but the shot.”