In early July at the Major Economies Forum in L’aquila, Italy, G8 leaders took a big step by publicly announcing a goal of limiting global warming to 2° C. Let us all acknowledge that it is a Big Deal that these countries — the ones who created climate change to begin with — are going to take steps to mitigate this impending crisis.
Now let us bang our heads against our desks in frustration because they missed the point. The 2° C goal is simply not the right metric to use. We no longer talk about “global warming” by itself because we are changing the whole climate, and that includes many other vital parameters than just global average temperature.
Our global climate problem stems from an unprecedented increase in greenhouse gases in the atmosphere that are directly traceable to human sources (like coal-fired power plants) and activities (like deforestation). It is greenhouse gases that we must concern ourselves with primarily, and that will, by extension, help to control increases in global average temperature.
I worry about the way this is framed because controlling CO2 and reducing the global temperature are not necessarily one and the same. By focusing on the temperature aspect of climate change, I fear that governments will consider drastic geo-engineering techniques to directly control their climate. Geo-engineering gets a fair amount of press these days, and for good reason: there is good evidence that certain techniques — like solar mirrors or sulfur injections into the stratosphere — can lower the global temperature in a matter of months. It’s the proverbial silver bullet — but for the wrong werewolf.
What is unfortunate about geo-engineering is that it tends to focus on one aspect of the climate system (temperature), and may have adverse effects on other parts of our climate. Several scientists, in a great Perspectives piece in *Science*, warn us that volcano-induced cooling from the explosion of Mt. Pinotubo also decreased global precipitation for the next two years. It turns out that precipitation patterns are more correlated with the amount of radiation coming in from space (which volcanic dusts block) than the temperature of the lower atmosphere (a process dominated by earth’s own heating power and greenhouse gases). In other words, the slight increase in atmospheric temperatures due to anthropogenic warming has less of an effect on precipitation than a decrease in solar insolation. We may lower the temperature of the surface by blocking sunlight just outside the atmosphere, but in exchange there would be far less solar energy to create the clouds necessary for rain.
The authors make an excellent point: most technological solutions to climate change tend to mitigate only one aspect of the climate system, but can exacerbate other, potentially dangerous parameters. As we consider various geo-engineering solutions to our problems, let’s remember that we are not just fighting “global warming,” but attempting to halt “anthropogenic climate change.” Semantics to those in the know, perhaps, but our political leaders must be held to account for the cause of our climate problem, and not the symptoms.