Wealthy consumers in the United States and Europe need to take the lead in efforts to prevent devastating climate change because they outsource their weather breaking carbon emissions to developing nations, according a new study in PNAS.

Researchers at the Carnegie Institution's Department of Global Ecology write 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. Most of these emissions are outsourced to developing countries like China.

Since many developing countries are unwilling to enter into a global climate agreement that restricts their carbon emissions, holding developed nations accountable for a portion of these emissions may be the key to successfully implementing a Kyoto-like agreement, the authors say.

The new study relied on 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.

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).

(Photo Credit: Steven Davis/Carnegie Institution for Science)

"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 co-author Steven Davis. "On the flip side, nearly a quarter of the emissions produced in China are ultimately exported."

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 co-author Ken 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."

Citation: Steven J. Davis, Ken Caldeira 'Consumption-based accounting of CO2 Emissions', PNAS