Entropy is rapidly increasing, and the biosphere as a whole may well survive the impending dramatic climate changes, but the currently living species—not so much.
The ultimate reason is the one fundamental law that applies both to the life of each particular living being and the entire biosphere: the second law of thermodynamics.
The second law of thermodynamics is also called the law of entropy—but we are jumping too far ahead of the argument. According to the first law (of thermodynamics), energy can neither be created nor destroyed, but can only be transformed. Expressions such as “we consumed too much energy,” or “we are using up all the energy of the planet,” are improper: taken literally, they are incorrect from the point of view of modern physics. If we connect a fan to a power outlet and cause its blades to start turning, we aren’t actually “consuming” energy but transforming it: in this case, from electrical energy to mechanical energy. So, where does the problem lie?
The sticking point is found with the second law of thermodynamics, which states that with each energy transformation (such as in the example of our fan) the quantity of free energy (i.e. the energy which can be further transformed) is reduced. This second law also introduces the concept of irreversibility of all energy transformations. Let’s go back to our example: not all the electrical energy that goes through our fan is transformed into mechanical energy. A part of it is transformed into friction and heat. But the energy contained in the heat and the energy consumed in friction are no longer recoverable (i.e. degraded energy). That means we can never go back and transform the mechanical energy of the fan into the electrical energy we started with.
The second law also says that the entropy of a system will always increase. Entropy is associated with the degree of order and disorder: the natural tendency of all systems is towards disorder (a fact anyone who has ever fixed up their house knows all too well). The more we transform energy, the more entropy increases.
Entropy tends towards reaching a maximum when there is no more energy to be transformed: for example, in the case of the whole planet, this would happen when every point would have the same temperature. This condition is called heat death: there would be no more winds, no more tides, no more clouds, and so on. The world would have come to a final standstill. (With a view to the second law, Nicholas Georgescu-Roegen founded the science of bioeconomy, or the economy of living things.) The argument just presented explains why it is not, practically speaking, incorrect for us to talk about the transformation of energy as “energy consumption.” Both processes lead to the same result: an increase in entropy.
Why should we be concerned about the second law at all, since the final outcome (heat death) is a given anyway? Now we get to our true object of concern: the biosphere, the zone covering the planet and reaching from a few kilometers in height down to a few kilometers beneath the surface, where all known life is located (the core of the planet and the vacuum of space are of no interest to us). The energy from the light of the sun is captured by chlorophyll, a molecule which, with the help of a little water and some salts contained in the earth, gives rise to the (still incompletely understood) process of photosynthesis (a Greek word meaning “doing things with light”). The function of photosynthesis counteracts entropic degradation, as it tends to bring order to disorderly matter.
For millions of years, the biosphere has lived in a perfect balance. Photosynthesis ensured the survival of life in the biosphere, decreasing the entropy as solar energy reached now-fertile ground: part of it was preserved as part of the biosphere, and part of it was radiated out into space.
If we make an estimate of the entropy balance, we will find that disorder has been effectively pushed out from the planet in the form of low-temperature heat.
This delicate equilibrium was maintained until the industrial era. For millions of years, plants had worked removing excess of CO2 in the atmosphere until it reached modern levels, suitable for sustaining human life.
Where has this excess carbon (effectively a waste product) been stored? It was buried under the earth’s crust in the form of fossil fuels.
Thus, when we extract oil or other fossil fuels, it is as if we are dumping in the middle of the street all the refuse accumulated over millions of years (not exactly “black gold”!) and buried under the ground, with the ultimate result of returning the composition of the atmosphere to its original state (when there was no life).
With the advent of the industrial revolution, human beings have effectively been taking energy and matter from the bowels of the earth and transforming it. This transformation produces carbon dioxide, methane, and other gases—in a word, greenhouse gases. The solar energy retained by the greenhouse gases in the atmosphere is no longer in equilibrium with the solar energy entering the system, and the average temperature of the biosphere is changing. The average temperature in the biosphere has been stable for millions of years (14.5°C at sea level). Just a few degrees higher (2.5°C, as scientists are saying) and the polar ice caps will be melting, the sea level will be rising, and severe and abrupt climate changes (which we are already observing) will occur.