Pity 鈥� we almost got away with believing it was OK to keep shipping bananas and flowers from Africa to Europe. But a study published this week, which suggests fuel emissions from ships cool the world and will continue to do so for centuries, has been criticised for being 鈥渕isleading鈥�.
Jan Fuglestvedt of the Center for International Climate and Environmental Research in Oslo, Norway, and colleagues calculated how emissions produced in 2000 by various forms of transport will affect the world in 20, 100 and 500 years. Shipping, they conclude, 鈥渃auses net cooling, except on future timescales of several centuries鈥� (Proceedings of the National Academy of Sciences, ).
However, a key assumption 鈥� that shipping emissions ceased after 2000 鈥� is clearly unrealistic, says Alice Bows of the Tyndall Centre in Manchester, UK. 鈥淭he conclusions may be misleading to policy-makers if they take this paper to be an assessment of the future impact of transport modes,鈥� she says.
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Shipping fuel produces ultra-fine particles which reflect solar energy back out into space, and so can cool the climate. Yet they are washed back down to the ground in a matter of days. Carbon dioxide, meanwhile, accumulates in the atmosphere.
鈥淚 guess that if we did the same thing for 2001 and 2002 and so on we should see an increasing effect of CO2 and a warming that is more difficult to get rid of,鈥� concedes Fuglestvedt.
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