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Researchers at the Carnegie Institution's Department of Global Ecology are looking to optimize climate change reduction by injecting sulfates into the stratosphere. George Ban-Weiss, lead author of the study, along with his team of Carnegie scientists, have studied how the injection of aerosols of sulfate into the stratosphere will affect Earth's chemistry and climate, and which aerosol distribution pattern will bring them closest to their climate goals.
To do this, Ban-Weiss and his team used a global climate model with different sulfate aerosol concentrations depending on latitude to run five simulations. They then determined what distribution of sulfates would bring them closest to climate goals by using the results from the simulations in an optimization model. These distributions were then tested in the global climate model to see how close they came to these goals.
"We know that sulfate can cool the Earth because we have observed global temperature decreases following volcanic eruptions," said Ban-Weiss. "Past computer model simulations have shown that injecting sulfate uniformly into the stratosphere could reduce the surface temperature of the Earth, but the equator would be over cooled and the poles under cooled. You would also make the Earth drier, and decrease surface water runoff."
But Ban-Weiss' results from his climate models showed that more sulfate over the poles rather than tropical regions would result in a low-carbon climate. But when sulfates were distributed uniformly, changes in the water cycle were "most effectively diminished." If the right amount of uniformly distributed aerosols were injected into the stratosphere, the consequence of climate change could be decreased by 90 percent and the change in runoff would be decreased by two-thirds. But when aerosols are distributed latitudinally as a parabola, temperature change decreased by 94 percent while runoff changes were only cut 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," said Ban-Weiss.
Ken Caldeira, co-author of the study, added that the study was mainly aimed to develop "a new methodology" for observing the current climate change problem, and that their model does not include all process that are essential in reality. Their results are strictly illustrative and not yet ready to provide a basis for policy decisions. But he also mentioned that the models of course worked.
"Our optimization model worked well because the complex climate models indicate that much of the climate system operates as a very linear system," said Caldeira. "This is surprising when you hear all the talk of tipping points."
This study was published in Environmental Research Letters this month.
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