Plan to avert global warming by cooling planet artificially 'could cause climate chaos
Proposal to inject tiny reflective
particles into the upper atmosphere to block out sunlight could lead to
droughts, warn scientists
SCIENCE EDITOR
Wednesday 08 January 2014
A controversial proposal to
cool the planet artificially by injecting tiny reflective particles into the
upper atmosphere which block out sunlight would cause droughts and climate
chaos in the poorest countries of the world, a study has found.
One of the more serious
plans to “geoengineer” the global climate would in effect create another
climate catastrophe that would result in misery for millions of people,
according to a computer model of the plan.
Some climate researchers
have suggested that mimicking the cooling effects of volcanic eruptions with
massive injections of sulphate particles into the atmosphere may be necessary
in an emergency if global temperatures and carbon dioxide levels continue to
rise unabated.
It is known that the
sulphate particles produced by volcanoes, which are relatively quickly washed
out of the atmosphere, can reduce incoming solar radiation significantly, and
so cause average global temperatures to dip.
However, a study by
scientists at Reading University has found that the effect of a massive and
continuous injection of sulphates into the air would be to alter the rainfall
patterns over vast regions of the world, notably Africa, South America and Asia
which could as a result be devastated by drought.
“We have shown that one of
the leading candidates for geo-engineering could cause a new unintended
side-effect over a large part of the planet,” said Andrew Charlton-Perez of the
University of Reading, a co-author of the study published in the journal
Environmental Research Letters.
“The risks from this kind of
geo-engineering are huge. A reduction in tropical rainfall of 30 per cent
would, for example, quickly dry out Indonesia so much that even the wettest
years after a man-made intervention would be equal to drought conditions now,”
Dr Charlton-Perez said.
“The ecosystems of the
tropics are among the most fragile on Earth. We would see changes happening so
quickly that there would be little time for people to adapt.
“Discussion of
geo-engineering often prompts heated debate, but very often there is a lack of
understanding of what putting large amounts of aerosol in the stratosphere will
do to the complex climate system. Our findings should help to fill in some of
the gaps about one of the leading candidates,” he said.
Volcanoes, such as the Mount
Pinatubo eruption in 1991, can cool average global temperatures significantly
for short periods, but to reverse the expected 4C rise in global temperatures
as a result of global warming would need large quantities of sulphate aerosols
to be injected into the upper atmosphere over the course of several years.
“To reduce global temperatures
enough to counter effects of global warming would require a massive injection
of aerosol – the small particles that reflect sunlight back into space. This
would be equivalent to a volcanic eruption five times the size of that of Mount
Pinatubo every year,” said Angus Ferraro of Exeter University.
“Previous predictions of how
stratospheric aerosol injection would affect climate were based on a number of
assumptions. By actually modelling what would happen if aerosol were to be
pumped into the atmosphere around the equator, we have revealed a new impact of
geo-engineering on tropical climate,” Dr Ferraro said.
“As well as reflecting some
of the incoming energy from the sun and cooling surface temperature, the
aerosol also absorbs some of the heat energy coming from the surface which
warms the stratosphere. We have shown for the first time that warming the
stratosphere makes the troposphere below more stable, weakening upward motion
and reducing the amount of rainfall at the surface,” he said.
Professor Ellie Highwood of
University of Reading, a co-author of the study said that there is an
understandable desire to explore alternatives to deep-cuts in carbon dioxide
emissions, which do not seem to be materialising as a result of the failure of
countries to reach a binding international agreement.
“Climate scientists agree
that cutting carbon emissions is still necessary to curb the damaging effects
of future climate change. However, since such cuts are far from certain to
materialise, proponents of geo-engineering research argue that whatever the
world decides on its carbon emissions, it would be prudent to explore
alternatives that might help us in the decades ahead,” Professor Highwood said.
“On the evidence of this
research, stratospheric aerosol geo-engineering is not providing world leaders
with any easy answers to the problem of climate change,” she said.
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