Findings The Earth Is Warming? Adjust the Thermostat Viktor Koen
By JOHN
TIERNEY<http://topics.nytimes.com/top/reference/timestopics/people/t/john_tierney/index.html?inline=nyt-per>
Published: August 10, 2009
President
Obama<http://topics.nytimes.com/top/reference/timestopics/people/o/barack_obama/index.html?inline=nyt-per>and
the rest of the Group
of
8<http://topics.nytimes.com/top/reference/timestopics/organizations/g/group_of_eight/index.html?inline=nyt-org>leaders
decreed last month that the planet’s average temperature shall not
rise more than 2 degrees Fahrenheit above today’s level. But what if Mother
Earth<http://topics.nytimes.com/top/news/science/topics/earth_planet/index.html?inline=nyt-classifier>didn’t
get the memo? How do we stay cool in the future? Two options:
Plan A. Keep talking about the weather. This has been the preferred approach
for the past two decades in Western Europe, where leaders like to promise
one another that they will keep the globe cool by drastically reducing
carbon emissions. Then, when their countries’ emissions keep rising anyway,
they convene to make new promises and swear that they really, really mean it
this time.
Plan B. Do something about the weather. Originally called geoengineering,
this approach used to be dismissed as science fiction fantasies: cooling the
planet with sun-blocking particles or shades; tinkering with clouds to make
them more reflective; removing vast quantities of carbon from the
atmosphere.
Today this approach goes by the slightly less grandiose name of climate
engineering, and it is looking more practical. Several recent reviews of
these ideas conclude that cooling the planet would be technically feasible
and economically affordable.
There are still plenty of skeptics, but even they have started calling for
more research into climate engineering. The skeptics understandably fear the
unintended consequences of tampering with the planet’s thermostat, but they
also fear the possibility — which I’d call a near certainty — that political
leaders will not seriously reduce carbon emissions anytime soon.
The National Academy of
Sciences<http://topics.nytimes.com/top/reference/timestopics/organizations/n/national_academy_of_sciences/index.html?inline=nyt-org>and
Britain’s Royal
Society <http://royalsociety.org/news.asp?id=8085> are preparing reports on
climate engineering, and the Obama administration has promised to consider
it. But so far there has been virtually no government support for research
and development — certainly nothing like the tens of billions of dollars
allotted to green energy and other programs whose effects on the climate
would not be felt for decades.
For perhaps $100 million, climate engineers could begin field tests within
five years, says Ken Caldeira of the Carnegie Institution for Science. Dr.
Caldeira is a member of a climate-engineering study group that met last year
at the Kavli Institute for Theoretical Physics under the leadership of
Steven E. Koonin, who has since become the under secretary for science at
the United States Department of
Energy<http://topics.nytimes.com/top/reference/timestopics/organizations/e/energy_department/index.html?inline=nyt-org>.
The group has just issued a report, published by the Novim research
organization, analyzing the use of aerosol
particles<http://arxiv.org/abs/0907.5140>to reflect shortwave solar
radiation back into space.
These particles could be lofted into the stratosphere to reproduce the
effects of sulfate aerosols from volcanic eruptions like that of Mount
Pinatubo in 1991, which was followed by a global cooling of nearly 1 degree
Fahrenheit. Just as occurred after that eruption, the effects would wane as
the particles fell back to Earth. Keeping the planet cooled steadily (at
least until carbon emissions declined) might cost $30 billion per year if
the particles were fired from military artillery, or $8 billion annually if
delivered by aircraft, according to the Novim report.
The idea of even testing such a system scares many people, and some
scientists argue that climate-engineering research should remain
theoretical. But Dr. Caldeira says that small-scale testing — perhaps an
experiment intended to slightly cool the Arctic — could be safer than the
alternative.
“The worst-case scenario,” he says, “is one in which you have an untested
system that you need to deploy quickly at large scale in a desperate attempt
to ward off some sort of climate crisis. It could be much better to start
testing soon at small scale and to observe what happens as the system is
deployed.” The sooner we start, he reasons, the more delicately we can
proceed.
“Because of natural variability in weather and climate, the smaller the
experiment, the longer it needs to be observed for the signal to rise out of
the noise,” Dr. Caldeira says. “With short testing periods, you would need
to hit the system with a hammer.”
Another way to cool the globe would be to spray seawater mist from ships up
toward low-lying clouds, which would become brighter and reflect more
sunlight away from Earth. (For details, see nytimes.com/tierneylab.)
This cloud-brightening technology might counteract a century’s worth of global
warming<http://topics.nytimes.com/top/news/science/topics/globalwarming/index.html?inline=nyt-classifier>for
$9 billion, according to J. Eric Bickel and Lee Lane. They identified
it
as the most promising form of climate engineering in a report published
Friday by the Copenhagen Consensus
Center<http://fixtheclimate.com/#/component-1/the-solutions-new-research/climate-engineering>,
which is sponsoring cost-benefit analyses of strategies for dealing with
climate change.
Other researchers say that it is impossible to do a cost-benefit analysis of
these engineering proposals because the potential downside is so
uncertain<http://www.geosc.psu.edu/%7Ekkeller/Goes_et_al_geoengineering_cc_2009_submitted.pdf>—
and large. Injecting aerosols into the stratosphere or brightening
clouds
would do more than just cool the planet. In a paper in the current
Science<http://www.sciencemag.org/current.dtl#twis>,
Gabriele C. Hegerl and Susan Solomon point to a drop in global precipitation
after the eruption of Mount Pinatubo, and warn that climate engineering
could lead to dangerous droughts.
A less risky form of climate engineering would be to gradually remove enough
carbon dioxide from the atmosphere to keep the planet cool. Some experts
argue that the technology already exists to make this “air-capture”
method<http://fixtheclimate.com/uploads/tx_templavoila/PP_Climate_Engineering_Pielke_v.1.0.pdf>reasonably
economical, and that its political advantages make it the most
realistic long-term strategy. What politician wants to tamper directly with
the climate and risk getting blamed for the next hurricane or drought?
But if the climate does become dangerously warm, there could be enormous
political pressure to do something quickly. And while it wouldn’t be easy
reaching international agreement on how to reset the planet’s thermostat, in
some ways it is less daunting than trying to negotiate a global carbon
treaty.
If rich European countries with strong green constituencies cannot live up
to their own promises to cut carbon, how much hope is there of permanently
enforcing tough restrictions in the United States, much less in poor
countries like India and China? If even a few nations demur or cheat, the
whole system can break down.
By contrast, climate engineering does not require unanimous agreement or
steadfast enforcement throughout the world. Instead of relying on
politicians’ promises, we might find it simpler to deal directly with Mother
Earth’s hot air.
*A version of this article appeared in print on August 11, 2009, on page D1
of the New York edition.*
___________________________________________________
Ken Caldeira
Carnegie Institution Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA
[email protected]; [email protected]
http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab
+1 650 704 7212; fax: +1 650 462 5968
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