Global warming has managed to become a major socio-political issue in recent months. Given that the vast majority of people qualified to make judgements on the issue agree that average global temperatures are currently increasing and that human activity is a major cause of this change, I don’t see how any reasonable person who is not so qualified could disagree. What policies should be enacted as a result is, of course, a much stickier subject. Below is a description of my understanding of the problem, followed by a few comments and questions it engenders in me. Please excuse and correct any gross errors below; I’m depending on memory of high-school chemistry. Of course the actual cycle is much more complex, but I think (hope!) that what I describe is the most important part of it.
The primary cause of global warming is believed to be the excessive presence of certain gases in the atmosphere that trap heat, with carbon dioxide [CO2] the primary culprit. Carbon dioxide exists naturally in the air, but too much* or too little* causes the average temperature to increase or decrease. The term “carbon neutral” is currently in vogue, meaning that a person or event does not have a net effect on the amount of carbon dioxide in the atmosphere.
The number of atoms of carbon and oxygen doesn’t change of course, except in the case of nuclear reactions involving those elements. Rather, the change comes when other molecules that contain carbon dioxide react to form carbon dioxide. Primarily, this happens as a natural process in living things. The cells of living creatures are built primarily of complex organic compounds (those consisting of mostly carbon, hydrogen, and oxygen), such as glucose [C6H12O6].
Forming these organic compounds from simpler molecules is an endothermic reaction — that is, it requires energy. Certain forms of life, mostly plants, extract carbon dioxide [CO2] from the air and water [H2O] and other compounds from the soil and use energy from the sun to combine them into complex organic compounds in the process of photosynthesis. For example glucose is formed from these by the reaction 6CO2 + 6H2O + energy -> C6H12O6 + 6O2.
Breaking down these organic compounds to simpler molecules is an exothermic reaction — that is, it produces energy. Other forms of life, primarily animals, digest organic compounds with free oxygen from respiration to harvest this energy, releasing carbon dioxide and water (as well as potentially other things for different compounds) as by-products. So in a perfect world where the number of plants and animals were properly balanced and all biomass was consumed at death, the quantity of carbon dioxide free in the air would remain roughly constant.
In the actual world, this process is not perfect. Lots of plants and animals die and are not digested by each other. Instead, they very slowly are transformed into other organic compounds known as fossil fuels — coal, oil, methane, and the like. Despite their different composition and lack of usefulness to biological systems, these compounds can be combined with oxygen in much the same way that animals digest their food. In these cases, the energy is used to power a combustion engine rather than the internal processes of cells, but the byproducts are similar. Thus, the argument is made that humans must stop converting the carbon stored in fossil fuels into atmospheric carbon dioxide because this upsets the balance.
This immediately brings to mind a number of questions and comments:
- It seems there are natural processes for removing carbon from the cycle described above, by producing fossil fuels, there seems to be no natural process for freeing this carbon to re-enter the cycle. Certainly a lightning strike might cause a forest fire that reaches coal that is just below the surface, but the fact that most of these substances are far below ground would make this a rare occurrence. As far as I understand, there are no biological processes by which these substances are broken down, although it would not surprise me to find that some microorganisms feed on them. Even if so, it would seem that carbon would not naturally be freed at the same rate at which it is stored.
- If the previous statement is accurate, does this mean burning of fossil fuels is merely reversing a trend? If we did not do so, would more and more carbon be removed from the life cycle over millenia until there was no more life, or would we reach an equilibrium where biomass is scarce enough that all of it gets consumed before it can become fossilized?
- Is it possible the reduction in number of plants is more of a problem than the burning of fuels? Even if not, could an increase in the number of carbon-trapping plants be a reasonable part of a solution?
- For that matter, burning biomass (wood) itself, would seem to be a sort of carbon-neutral action, since the wood would largely be decayed by microorganisms and remain in the cycle anyway?
- Would it be viable to perform some sort of artificial photo-synthesis? If the (essentially free) energy from the sun could be used to bind carbon dioxide into other compounds, we could replenish supplies of fuel and simultaneously remove excess carbon from the atmosphere. (Of course, if would probably be more efficient to simply use the solar energy for whatever purpose for which we were burning the fuels.)
- In any case, appealing to “saving the Earth” seems silly. The Earth has been warmer, it’s been colder, and has endured countless other significant changes. If average temperatures across the planet rise by 10 degrees, species will be forced to migrate or spread into areas with the climate to which they are best suited, but I suspect life will go on without much difficulty. What will be in danger are humans. If lots of current habitats are covered in water, the old inhabitants will be replaced by aquatic life that thrives in the new environment, and I don’t see why I should care. If millions of people lose their homes and livelihoods, they will need to adapt as well. Thus, I can certainly support well-researched initiatives to protect the status quo for the sake of each other, but not for the planet.