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.
