Ship fumes negate carbon emissions

London: Exhaust from commercial ships negates the impact caused by the industry's release of global-warming carbon dioxide into the air, a study has discovered.

Scientists at the National Oceanic and Atmospheric Administration in Boulder, Colorado, said tiny particles in the fumes spewed from ship engines have a cooling effect five times greater than the effect from the vessels' carbon dioxide emissions.

Particulate pollution and carbon dioxide have opposite effects on global warming, the study by Daniel Lack and his colleagues showed. Particles in the atmosphere absorb radiation and heat, known as solar shading, while atmospheric carbon dioxide hinders radiation from escaping, causing the Earth to warm.

Carbon dioxide from ships makes up an estimated three per cent of the emissions caused by humans.

Along with the carbon dioxide, the vessels discharge 2.2 million pounds of particulate matter annually and almost 30 per cent of smog-forming nitrogen oxide gases.

While some of the pollution reduces the global-warming effect, it also contributes to premature deaths among people living along coasts, the authors said. About 70 per cent of shipping traffic takes place within 250 miles (402 kilometres) of shorelines.

"This is a significant health concern for coastal communities," Lack said. The researchers analysed exhaust from more than 200 vessels in the Gulf of Mexico and their pollution, which is made up of sulfates and organic pollutants such as soot.