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Consumption-based accounting of CO2 emissions

Steven J. Davis and Ken Caldeira · Proceedings of the National Academy of Sciences 107, 5687-5692 · 2010

Key finding. In 2004, 23 per cent of global CO2 emissions — 6.2 gigatonnes — were traded internationally, primarily as exports from China and other emerging markets to consumers in developed countries; in Switzerland, Sweden, Austria, the United Kingdom, and France more than 30 per cent of consumption-based emissions were imported.

Three pairs of world maps for 2004, each pair a global map with a European inset, showing consumption-based emissions minus production-based emissions — the net effect of carbon dioxide embodied in trade. The top pair is in megatonnes of carbon dioxide per year, from minus 400 in blue to plus 400 in red, with the United States and Western Europe strongly red and China and Russia strongly blue. The middle pair normalizes by GDP and the bottom pair by population; on the per-capita map most of Western Europe, the United States, and Japan are red while China, Russia, and South Africa are blue.
Where emissions are counted decides who appears responsible. Wealthy consuming regions — Western Europe, the United States, Japan — import more emissions than they export, and the manufacturing economies that supply them export more than they import; the per-capita map (bottom) shows the imbalance is not merely a matter of country size. Figure 4 from Davis and Caldeira (2010), Proceedings of the National Academy of Sciences 107, 5687-5692. Reproduced under author reuse rights. Extracted from the published PDF and resized for web display.

What question did this research address?

Emissions are conventionally attributed to the country where the fuel is burned. But goods are made in one country and consumed in another, so production-based inventories attribute the emissions of an export industry to the producing country rather than to the people who use what it makes.

This paper asked how the global picture changes when emissions are attributed instead to the consumption of goods and services.

What did we find?

The study presents a global consumption-based CO2 inventory together with the associated consumption-based energy and carbon intensities, using the then-latest available trade and emissions data.

Roughly a quarter of all global emissions cross a border before reaching the consumer who occasions them, moving predominantly from emerging markets to developed economies.

Several wealthy European countries import more than 30 per cent of their consumption-based emissions, amounting to net imports exceeding 4 tonnes of CO2 per person in 2004.

The United States is a net importer too, but less dramatically — 10.8 per cent of its consumption-based emissions, or 2.4 tonnes of CO2 per person.

Why does it matter?

The result changes who appears responsible. A country can reduce its production-based emissions by importing the goods it used to make, with no change in global emissions at all, and a production-only inventory records that as progress.

It also reframes what a wealthy country's mitigation options are. If a large share of the emissions occasioned by its consumption occur abroad, then policies confined to its own territory address only part of its footprint.

Citation

Steven J. Davis and Ken Caldeira (2010). Consumption-based accounting of CO2 emissions. Proceedings of the National Academy of Sciences 107, 5687-5692.

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