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Curbs to ship pollution would stoke global warming, study says |
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Monday, 23 November 2009 |
 Shipping is slowing climate change by spewing out sunlight-dimming pollution but a clean-up needed to safeguard human health will stoke global warming, experts said.
"So far shipping has caused a cooling effect that has slowed down
global warming," Jan Fuglestvedt, of the Center for International
Climate and Environmental Research Oslo (CICERO), told Reuters.
"After some decades the net climate effect of shipping will shift from
cooling to warming" because of cleaner fuels, he and colleagues in
Germany, Britain and Norway wrote in this week's edition of the journal
Environmental Science and Technology.
Toxic sulphur dioxide emitted by burning bunker fuel accounted for the
deaths of an estimated 60,000 people worldwide in 2001 through cancer
and heart and lung disease, according to a previous study. A clean-up
would save thousands of lives.
But sulphur pollution from the fast-growing shipping industry also
helps create clouds by providing tiny seeds around which droplets form.
Clouds have a cooling effect since sunlight bounces off their white
tops.
The scientists argued against deliberate use of pollution from ships as
part of possible schemes to shield the planet from sunlight, saying it
was too risky and outweighed by the impact on human health.
CLIMATE COOLING
"The available evidence suggests that 'climate cooling' by continued
shipping emissions of sulphur dioxide would not be advisable," they
wrote.
A clean-up of sulphur from ships will have a "double warming" effect --
there will be more sunlight with less pollution and there will be ever
more carbon dioxide, the non-toxic greenhouse gas emitted by burning
fuel.
Shipping accounts for about 3.3 percent of world carbon dioxide
emissions from human sources, emissions the U.N. Climate Panel says
will cause more droughts, floods, heatwaves, rising sea levels and
disease.
Some scientists, such as Nobel Prize winner Paul Crutzen, have
suggested dumping sulphur in the upper atmosphere to slow global
warming, one of several proposals for deliberate "geoengineering" to
alter the climate system.
A U.N. climate summit in Copenhagen next month will consider new
measures to penalize carbon dioxide emissions by both international
shipping and aviation -- both are outside the existing Kyoto Protocol
for slowing emissions until 2012.
Fuglestvedt's study estimated that it would take roughly 70 years for
shipping to become a net contributor to global warming if sulphur
dioxide emissions were quickly cut by 90 percent and all other
fuel-related emissions stayed at 2000 levels.
The International Maritime Organization is seeking cuts in the sulphur
content of bunker fuel to a maximum of 3.5 percent by 2012 and then to
0.5 percent by 2020.
Source: Reuters
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