Washington (March 8, 2010)
- A new study by scientists at the Carnegie Institution for Science
finds that over a third of carbon dioxide emissions associated with
consumption of goods and services in many developed countries are
actually emitted outside their borders. Some countries, such as
Switzerland, "outsource" over half of their carbon dioxide
emissions, primarily to developing countries.
The study finds that, per person, about 2.5
tons of carbon dioxide are consumed in the U.S. but produced
somewhere else. For Europeans, the figure can exceed four tons per
person. Most of these emissions are outsourced to developing
countries, especially China.
"Instead of looking at carbon dioxide emissions only
in terms of what is released inside our borders, we also looked at
the amount of carbon dioxide released during the production of the
things that we consume," says co-author Ken Caldeira, a researcher
in the Carnegie Institution's Department of Global Ecology.
Caldeira and lead author Steven Davis, also at
Carnegie, used published trade data from 2004 to create a global
model of the flow of products across 57 industry sectors and 113
countries or regions. By allocating carbon emissions to particular
products and sources, the researchers were able to calculate the
net emissions "imported" or "exported" by specific countries.
"Just like the electricity that you use in your
home probably causes CO2 emissions at a coal-burning
power plant somewhere else, we found that the products imported by
the developed countries of western Europe, Japan, and the United
States cause substantial emissions in other countries, especially
China," says Davis. "On the flip side, nearly a quarter of the
emissions produced in China are ultimately exported."
China is by far
the largest "exporter" of carbon dioxide emissions, as seen in this
map of the net flow of emissions embodied in trade among the major
exporting and importing countries. Arrows indicate direction and
magnitude of flow; numbers are megatons (millions of tons). Credit:
Steven Davis/Carnegie Institution for Science.
Over a third of the carbon dioxide emissions
linked to good and services consumed in many European countries
actually occurred elsewhere, the researchers found. In Switzerland
and several other small countries, outsourced emissions exceeded
the amount of carbon dioxide emitted within national borders.
The United States is both a major importer and a
major exporter of emissions embodied in trade. The net result is
that the U.S. outsources about 11% of total consumption-based
emissions, primarily to the developing world.
The researchers point out that regional climate
policy needs to take into account emissions embodied in trade, not
just domestic emissions.
"Our analysis of the carbon dioxide emissions
associated with consumption in each country just states the facts,"
says Caldeira. "This could be taken into consideration when
developing emissions targets for these countries, but that's a
decision for policy-makers.
One implication of emissions outsourcing is that
a lot of the consumer products that we think of as being relatively
carbon-free may in fact be associated with significant carbon
dioxide emissions."
"Where CO2 emissions occur doesn't
matter to the climate system," adds Davis. "Effective policy
must have global scope. To the extent that constraints on
developing countries' emissions are the major impediment to
effective international climate policy, allocating responsibility
for some portion of these emissions to final consumers elsewhere
may represent an opportunity for compromise."
The report is published online in the March 8,
2010 Proceedings of the National Academy of Sciences