TOUGHER regulation of shipping emissions should expose the true impact of the industry on global warming, according to new research released in the run up to the Copenhagen climate summit.
Ship emissions of sulphur dioxide are known to cause cooling through atmospheric particles and clouds, which masks the warming effects of carbon dioxide and nitrogen oxide emissions, giving the industry a net cooling effect on climate.
Scientists observing climate change argue that these cooling effects have been used by industry to justify not doing anything about carbon emissions which are now higher than those from aviation.
However, new caps on sulphur are shortly to be adopted by the International Maritime Organisation which will see sulphur content of fuel fall from 4.5% to 3.5% by 2012 and to 0.5% by 2020.
"Given these reductions, shipping will, relative to present-day impacts, impart a “double-warming” effect: one from carbon dioxide and one from the reduction of sulphur dioxide.
"Therefore, after some decades the net climate effect of shipping will shift from cooling to warming," says the study published in the journal Environmental Science & Technology.
David Lee, Director of the Centre for Aviation, Transport and the Environment at MMU and scientists from Germany and Norway modelled the impacts of emissions on atmospheric chemistry.
They found that with sulphur emissions constant the warming effect of carbon dioxide would be negated for centuries. However when sulphur was drastically reduced the net temperature effect switches to warming much earlier – after just 70 years.
Kyoto to Copenhagen
Shipping pollution is not regulated by the Kyoto Protocol and there is currently no international agreement on how carbon dioxide emissions can be controlled.
Professor Lee is an expert adviser to the UK Committee on Climate Change.
Notes on the authors: Jan S. Fuglestvedt is a research director of CICERO.
Terje Berntsen is a senior scientist at CICERO and a professor in the Department of Geosciences, University of Oslo.
Veronika Eyring is a senior scientist at the Institut fur Physik der Atmospha¨re of the Deutsches Zentrum fur Luft- and Raumfahrt (DLR) and a visiting professor at the Manchester Metropolitan University (MMU), UK.
Ivar Isaksen is a senior scientist at CICERO and a professor in the Department of Geosciences, University of Oslo.
David S. Lee is a professor of atmospheric science at MMU and Director of the Centre for Aviation, Transport and the Environment.
Robert Sausen is head of the department for Atmospheric Dynamics at the Institut fur Physik der Atmosphare of the Deutsches Zentrum fur Luft- and Raumfahrt (DLR) and a professor of meteorology at the Ludwig-Maximilians-Universitat Munchen.