Campus Journalism

A. Collective

There are a number of possible responses to these forecasts. We could do nothing in particular about them. We could decide to continue emitting carbon dioxide, but to study its effects closely, planning to take some action if effects begin to look dangerous.
We could decide that some change in the global mean state is acceptable, and limit carbon dioxide emissions to an amount that we think will prevent change in excess of the acceptable limit. We could decide that no human-caused change in the mean climate is acceptable, and aim to live our lives with zero net carbon emissions. Finally, we could attempt to manage multiple aspects of the earth’s climate system in an attempt to globally optimize climate.
Decisions, of course, are not matters of science, but of ethics. To decide, we consider the harms and benefits of our actions, understanding in this case that our actions will constrain the choices of our descendants: carbon dioxide lasts a long time in the atmosphere, climate change takes a long time to occur, and loss of species diversity is permanent on human time scales. In the particular case of climate change, the international community has committed itself, through the Framework Convention on Climate Change (signed in Rio in 1994 and ratified by 150 nations, including the United States), to “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic [human-caused] interference with the climate system.” Since “danger” in the context of the treaty includes danger to ecosystems, the climate change science community would say that we are at or above that level of greenhouse gas concentrations now. The question remaining before us is, will it be so expensive to reduce carbon dioxide emissions or concentrations that we will fail to live up to the Framework convention?
The problem is challenging because the rapid industrialization of China and India means that we must reduce emissions rapidly, even while the total number of serious emitters grows rapidly. However, there is reason to be optimistic. Some point to possible compensatory actions that would cool the earth, countering the warming effects of carbon dioxide. These solutions have appealing and unappealing aspects. Shooting sulfur dioxide into the stratosphere would be cheap and effective (volcanic eruptions cool the earth by this mechanism), but might cause unacceptable damage to the ozone layer. Orbiting mirrors could cleanly deflect sunlight away from the earth’s surface. However, such temperature-control systems would not protect the oceans from acidification by the carbon dioxide they absorb, and they would leave the earth vulnerable to a dramatic warming should some economic downturn prevent maintenance of the climate-control systems.
Fortunately, another class of solutions exists. Although the natural lifetime of carbon dioxide in the atmosphere is long, there are very plausible artificial ways to remove the gas from the atmosphere. Large structures, similar to cooling towers, could be built that would draw in air, and spray it with sodium hydroxide solution. The solution would then be processed to remove the carbon dioxide, and the carbon dioxide stored underground. This procedure would cost about $500 per metric ton of carbon, or $1.25 per gallon of gasoline burned. In combination with the development of biomass fuels, the total additional cost of driving a car without emitting any net carbon dioxide could be reduced to about $0.50 per gallon.* These prices are actually rather high: on the
European carbon trading market, established under Kyoto, prices are around $32/ton, meaning that for $32, a utility company (for example), is willing to reduce its emissions of CO2 by one metric ton. However, it is expected that prices on these exchanges would rise if controls on emissions become stricter, while the estimates for carbon drawdown listed above are made assuming a very high volume.