Geoscience Reference
In-Depth Information
Plan B
9
GeoenGineerinG to the rescue?
The eruption of Mount Pinatubo in the
Philippines in 1991 was the second-largest
eruption of the twentieth century. Volcan-
ologists successfully warned most of the
people living near the mountain, but the
massive eruption still managed to kill over
seven hundred people, many from roofs col-
lapsing under the pileup of ash. Measure-
ments reveal that the mountain spewed
ash twenty-one miles high, spreading vast
amounts of aerosol and dust particles into
the stratosphere. Mount Pinatubo ejected
an estimated seventeen million tons of
sulfur dioxide into the stratosphere, a co-
lossal deposit of particles that reduced the
amount of sunlight reaching the earth by
about 10% (by reflecting sunlight back into
space) and resulted in an average cooling
of the Earth's surface of nearly 0.6 degree
Celsius (1 degree Fahrenheit) in the year
following the eruption. The particles from
Mount Pinatubo remained in the strato-
sphere for three years.
As previously discussed, aerosols re-
leased by anthropogenic activity can have
a cooling effect. This cooling complicates
efforts to combat global warming. If we
“clean up” pollutants to reduce green-
house gas emissions, we may experience
increased temperatures because we also
eliminate aerosols. Such particles contrib-
ute to health problems, asthma and lung
cancer, but also may cool the atmosphere
by reflecting sunlight.
In an essay published in the journal
Cli-
mate Change
in 2006, Paul Crutzen, an at-
mospheric chemist who won the Nobel
Prize in chemistry in 1995, proposed in-
jecting sulfates into the stratosphere with
balloons or artillery guns to combat “po-
tentially drastic climate heating.” Crutzen
argued that if “sizeable reductions in green-
house gas emissions will not happen and
temperatures rise rapidly, then climatic en-
gineering . . . is the only option available to
rapidly reduce temperature rises and coun-
teract other climatic effects.” Crutzen was
not the first to propose such a radical idea,
but the essay marked a shift in thinking by
some in the scientific community, who be-
lieved that the time had come to seriously
study engineering schemes as a means of
quickly counteracting catastrophic cli-
mate change. The shift was brought about
