They found that if the right amount of uniformly distributed aerosols were put into the stratosphere, the magnitude of the temperature change could be diminished by 90% and the change in runoff by two-thirds. Under another scenario with aerosol distributions varying latitudinally as a parabola, the magnitude of temperature change was reduced by 94%, but then runoff changes were only reduced in half.
"Changes in temperature and the hydrological cycle cannot be simultaneously minimized because the hydrological cycle is more sensitive to changes in solar radiation than are surface air temperatures," explained Ban-Weiss.
"Our optimization model worked well because the complex climate models indicate that much of the climate system operates as a very linear system. This is surprising when you hear all the talk of tipping points," remarked co author Ken Caldeira. He continued, "Of course, this is just one model and it does not include all processes that are important in reality. Our results are illustrative and do not provide a sound basis for making policy decisions."
The specific climate goals and metrics used were somewhat arbitrary. "The study was primarily aimed at developing a new methodology for looking at the climate problem," said Caldeira.
"It's important to stress that geoengineering options can never reverse all of the consequences of greenhouse gas emissions. For example, it doesn't reverse ocean acidification. And it obviously has associated risk. So geoengineering is not an alternative to greenhouse gas emissions reductions." said Ban-Weiss.
|Contact: George Ban-Weiss|