Over a third of carbon dioxide (CO2) emissions associated with consumption of goods and services in many developed countries are actually emitted outside their borders, a new study by scientists at the Carnegie Institution, US, has found.
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 US 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," said 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," said Davis.
"On the flip side, nearly a quarter of the emissions produced in China are ultimately exported," he added.
The researchers found that over a third of the carbon dioxide emissions linked to good and services consumed in many European countries actually occurred elsewhere.
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 US outsources about 11 percent of total consumption-based emissions, primarily to the developing world.
According to Caldeira, "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."