Geoengineering schemes under scrutiny
Researchers divided over the wisdom of climate
Geoengineering, the deliberate manipulation of climate to counteract
global warming, might not be taking off just yet, but the push to fund
more research into it is increasing.
This week, Novim, a think tank based in Santa Barbara, California,
released a report that investigated the feasibility of one of the
wilder-sounding geoengineering schemes: Pumping tiny particles into the
upper atmosphere to block sunlight and trigger global cooling.
“It’s the most serious technical report to date”, says David Keith of
the University of Calgary in Alberta, Canada, who has been researching
geoengineering for two decades. Keith was an author on the report, which
was led by Steve Koonin, now chief scientist for the US Department of
Energy, and Jason Blackstock of the International Institute for Applied
Systems Analysis in Laxenburg, Austria.
Among other things, it concludes that spraying sulphate aerosols, to
mimic the cooling effects of a major volcanic eruption, is technically
But the political and ethical challenges facing such a worldwide
intervention remain virtually unknown, as do its unintentional side
Those potential side effects could include irrevocably altering
precipitation patterns, argue Gabriele Hegerl, of the Grant Institute in
Edinburgh, UK, and Susan Solomon, of the US National Oceanic and
Atmospheric Administration in Boulder, Colorado, in a paper published
online on 6 August in Science1.
They cite the instance of the 1991 eruption of Mount Pinatubo on
Luzon island in the Philippines, which injected sulphur particles high
into the stratosphere, causing global precipitation and river flow to
“Geoengineering schemes optimized to cancel greenhouse warming will
lead to a less intense global hydrological cycle and major regional
changes”, agrees Philip Duffy, a researcher at Climate Central in Palo
Duffy and Keith both spoke in Albuquerque, New Mexico, at the annual
conference of the Ecological Society of America. They participated in a
symposium on 6 August that aimed to make ecologists more aware of the
field, which, until now, has mainly been dominated by experts in
climate, the atmosphere or the ocean.
Geoengineering schemes are often notable for their sheer
outlandishness. The sulphate scheme studied in the Novim report would
require giant hoses or cannons to constantly blast particles into the
air. Other plans call for installing tens of thousands of reflective
sunshades in orbit to block incoming sunlight, or for seeding vast
swathes of the ocean with iron in an effort to trigger plankton blooms
that would suck down carbon dioxide from the atmosphere.
Keith notes that both the public and researchers often confuse the
two main approaches to geoengineering, solar radiation management, which
aims to block incoming light using techniques such as aerosols or
sunshades, and carbon cycle engineering, which uses techniques such as
ocean fertilization. Solar management is relatively cheap and fast, but
comes with unknown effects on the climate system; engineering of the
carbon cycle is slow and expensive ‘but gets the carbon out”, he says.
Keith and the other authors of the Novim report argue that research
should begin into the effects of small-scale geoengineering experiments.
“You don’t have to do it on a large scale”, he says. The report
recommends, for instance, preliminary work on determining the best way
to deliver and disperse sulphur aerosols, and on wind-field and other
modelling to work out how the particles might spread throughout the
It also lays out what sort of field tests might be needed to validate
this work, including “a non-trivial stratospheric aerosol loading to be
maintained for several years”.
It does not put numbers on the cost of such research, nor does it
identify which country should take the lead on it. It calls for
‘international processes’ to be put in place to develop guidelines for
coordinating potential responses from various countries.
In another report issued today, the Copenhagen Consensus Center, a
Denmark-based group founded by Bjørn Lomborg, author of the book The
Skeptical Environmentalist, tackles the potential costs of several
geoengineering schemes. It argues for spending US$750 million every year
for the next decade on geoengineering research, particularly on solar
radiation management and the study of its side effects.
Meanwhile, the UK Royal Society is expected to release a detailed
report on geoengineering options in September, the first major
scientific academy to do so.
The cooling aerosols pumped into the atmosphere by the 1991 eruption
of Mount Pinatubo inspire one proposed approach to fight global warming.
Courtesy Nature News