Two letters appeared in the February 2009 issue of Physics Today. Both were written by well-regarded scientists, both questioned the definition and ethics of geoengineering. Robert Frosch, a physicist, pointed out the definition of geoengineering, which he gives as, “purposeful action intended to manipulate the environment on a very large–especially global–scale.” Frosch points out that a decline in anthropogenic carbon dioxide emissions is included in this definition. Since most people agree that our carbon dioxide emissions should decline, geoengineering in this regard is not so controversial.

Frosch goes on to argue that there might be reason for worry. The intricate feedback loops and adjustments that the climate system has already undergone in accommodating the extra CO2 probably will not follow an exact reverse path if the CO2 concentration declined. To Frosch, the uncertainty in carbon dioxide removal and potential negative side effects are enough to halt CO2 removal. I should point out that this is an opinion letter and has no scientific analysis attached to it other than basic concepts of feedback loops. Frosch’s point is that CO2 mitigation must be studied before it is launched into.

Uncertainty seems to expand every moment with geoengineering. Kevin Trenberth, an NCAR scientist, writes a letter as well which complements Frosch’s plea for caution and research, but tackles geoengineering from an ethical standpoint. Trenberth points out that there will be some regions subjected to the negative effects of climate change, while others flourish. His ethical argument against geoengineering is, “Given that climate change is not universally condemned, how can anyone justify deliberately acting to change the climate to benefit any particular group, perhaps even a majority?” I would argue that the scientific consensus falls on adverse effects outweighing the positive effects. But aside from the science, Dr. Trenberth does point out that for such a large scale change, with such unknown effects, it is unethical to force dissenters to have their climate affected. This is only true where knowledge is available. Our understanding of the chemistry and physics of the atmosphere is much greater than it was when we first started altering the climate in the industrial revolution. We know anthropogenic changes are possible, giving reason to fear any purposely implemented climate change. Of course, when I drive in a car I am actively altering the climate by pumping hydrocarbons into the atmosphere which will become CO2 and remain such for 1000 years.

The ethics of geoengineering are too complicated for me to untangle. Our everyday actions are affecting the climate. Trenberth argues that we can not ethically alter the climate through geoengineering – but our transportation system, our cattle ranches, our factories, things we do every day add up to “geoengineering” by Frosch’s definition.