Could pollution be the solution to global warming? In the August issue of Climatic Change Dr. Paul Crutzen resurrected this bold proposal: create a global haze by ejecting thousands and thousands of tons of sulphuric material (SO2) into the stratosphere to produce a shaded earth that would counter the effects of global warming. If anyone else said this, they would not have gotten the idea published in a reputable journal, but Dr. Crutzen is a Nobel laureate, having earned the Nobel prize in chemistry in 1995 for helping to work out the chemistry of ozone destruction in the upper atmosphere. This idea is not new, and has been floating around climatology circles for years where it is known as an example of geoengineering (sci-fi fans, think terraforming). This idea of geoengineering was first put forth by a Soviet climatologist, Mikhail Budyko, who suggested that small reflective particles in the atmosphere could reflect enough of the sun's energy to cool the earth and negate global warming.
Nature lent credence to this radical idea through two events, the 1982 eruption of the volcano El Chichón and the more recent eruption of Mount Pinatubo in 1991. The eruption of Pinatubo left large quantities of water droplets containing sulfuric acid, each of which reflected some of the sun's energy away from the earth—enough in fact to cool the earth at a rate of about 0.5 oC/yr for almost two years after the eruption. If a human-made "volcano" could reproduce this event, it could counteract the global warming we are currently experiencing. However, this would be a huge engineering undertaking—Pinatubo's eruption released 10 million tons of sulfur into the atmosphere! More importantly, no one knows what effect this would really have.
Reported in last week's edition of Science was a collection of preliminary climate modeling simulations that attempt to quantify the effect of a man-made "volcanic" eruption. A series of simulations where sequential "eruptions" were carried out every year, every other year, and every four years were carried out. The Pinatubo eruption-associated forcing parameter that was derived from actual data and used in the simulations had a peak annual mean value of -2.97 W/m2. The simulations were done using the Model for the Assessment of Greenhouse gas-Induced Climate Change (MAGICC), which is an upwelling-diffusion energy balance model. The parameters were chosen such that a 3 oC rise in equilibrium temperature would occur for a doubling of the CO2 concentration. It was found that the bi-annual case would be capable of offsetting the anthropogenic change predicted to occur over the next century and hold global warming at bay indefinitely. It was also predicted that the climate would return to "normal" within tens of years after the "eruptions" are stopped.
While this shows the promise this idea may hold, it doesn't solve the underlying issues. This is similar to dieting and trying to lose weight, meaning if you do not change the underlying eating patterns that caused you to gain weight in the first place you will never be able to keep it off. Many climate researchers are worried because this idea is merely a band-aid as it can solve the problem in the short term, but does not solve the underlying causes of anthropogenic climate change. Another worry is that if this would be carried out and falter for some reason, the Earth could see decades or centuries of warming within the span of just a few years. The study in Science makes note of this as well, that geoengineering alone cannot be used to solve the current problems facing our world. The study also compares the effect of various policies that have been discussed by various international bodies to see the possible effect they might have on the Earth's climate. The article makes note early on that mitigation of fossil fuel consumption and current CO2 levels is needed, but this method of geoengineering could be used to buy us a little more time to find a better way to change our behavior and potentially develop more—and more importantly cheaper—alternative and renewable fuel sources.