14 DAY TRIAL // Adepts of climate engineering have proposed placing sun-reflecting gases up in the stratosphere in order to slow down or even completely stop global heating. These substances would be released by airplanes or artillery shells and they would form a mist reflecting sunlight back into space.
The idea came from the effects of volcano eruptions such as Mount Pinatubo in the Philippines. In 1991, Mount Pinatubo erupted and blasted enough sulfur in the stratosphere that it temporarily decreased the global temperature by almost half a degree.
Kate Ricke, a climate physicist at Carnegie Mellon University in Pittsburgh, Pennsylvania, and her colleagues, show in a paper published yesterday in Nature Geoscience that this method would only lead to a decrease in global rainfall and that the side effects would affect each region differently. Ricke says that this study “confirms that it is not possible to control both temperature and precipitation using stratospheric geoengineering.”
The study concluded that this method would probably help stabilize the temperature until 2080, but it would also have serious weather-related side-effects. The main concern is the decrease of rainfall, as it would change “the distribution of energy in the troposphere so that it becomes more convectively stable,” she added.
Changing precipitations would affect regions of the globe differently according to her study: as China's sulphates level maintained its baseline climate, they caused cold and humidity in India, and India's optimum sulphates level overheated China. Developing this model, researchers found that the effects get more serious in time. Ricke says that “ the compensation is imperfect. The longer you do it, the more imperfect it becomes.”
For this study, scientists used a global climate model from the Hadley Centre for Climate Prediction and Research in Exeter, UK, called HadCM3L. Their several simulations were made possible thanks to a climate-forecasting experiment, for which people signed up on climateprediction.net, and offered to have their home computers doing climate simulations. Ken Caldera, a climate scientist at the Carnegie Institution for Science's Department of Global Ecology, in Stanford, California, said that “this is something that people can sign up for on home computers that sit idle most of the day. When the computer notices it is idle for a while, it starts running climate models.”
Ricke's study “confirms that it is not possible to control both temperature and precipitation using stratospheric geoengineering,” said Alan Robock, geophysicist at Rutgers University in New Brunswick, New Jersey.
Even if the study is quite conclusive, Caldera says that Ricke only used one model for the research, and phenomena such as differences between China and India might be typical for this model only. He adds that though nobody should draw conclusions based on one experiment, the different results in various regions are likely to be something people should expect.