Transport emissions sizable, and rising

Science News, Jan 19, 2008 by Sid Perkins

Almost one-sixth of the carbon dioxide produced by human activity since the beginning of the Industrial Revolution has resulted from the transport of goods and people--a fraction that is increasing by the year, scientists say.

Worldwide, human-generated emissions of carbon dioxide rose about 13 percent between 1990 and 2000, says Jan Fuglestvedt, an atmospheric chemist at the Center for International Climate and Environmental Research-Oslo. During that same period, however, emissions of that greenhouse gas from road transport and aviation jumped about 25 percent.

Fuglestvedt and his colleagues used current and historical data to estimate the amounts of carbon dioxide produced by various modes of moving goods and people: railroads since 1850, shipping since 1870, road transport since 1900, and aviation since 1930. Highway emissions shot past those of railroads and ships in the 1940s, and those from aviation really took off in the 1960s, the scientists report online and in the Jan. 15 Proceedings of the National Academy of Sciences. Today, aircraft emit more than 600 million metric tons of carbon dioxide each year, while cars and trucks produce a whopping 4.2 billion metric tons.

Overall, the transport of goods and people has generated about 15 percent of the carbon dioxide emitted by human activity since preindustrial times, says Fuglestvedt. Such activities now produce about 21 percent of the world's carbon dioxide emissions, a fraction that could rise to between 30 and 50 percent by 2050.