Shipping emissions are responsible for more than half of the transport-induced changes in the ozone in various regions, according to a new report that estimates the impact of road, aircraft and shipping emissions on the Earth’s atmosphere.
The EU-funded research is part of the QUANTIFY project, Quantifying the climate impact of global and European transport systems, which has received EUR 8.39 million (approximately $11.9 million) in funding under the Sixth Framework Programme (FP6). The QUANTIFY researchers are evaluating the current and future climate impact of European and international transport systems.
The researchers used six different atmospheric chemistry models in order to estimate the impact of emissions from road transport, aviation and shipping on ozone levels. They also estimated the impact on the hydroxyl radical OH, which is known as the “detergent” of the troposphere because it helps remove many pollutants and greenhouse gases like carbon dioxide, said the researchers.
The report finds that emissions from ships have the largest impact on global OH levels in the lower troposphere, while aircraft emissions, which don’t play a big role in the upper troposphere, have the biggest impact on the ozone in the tropopause — the boundary between the troposphere and the stratosphere layers of the Earth’s atmosphere.
Road traffic also affects the northern upper troposphere with the biggest impact during the northern summer, said the researchers. The study finds that traffic emissions resulting in high ozone levels are worse during the summer season in the northern hemisphere, extending from eastern U.S. across the Atlantic to western Europe. The researchers also discovered that changes are around 50 percent lower in the southern hemisphere compared to the northern hemisphere.
The QUANTIFY partners also looked at the potential impact of ozone and methane on climate change by measuring the associated radiative forcing (RF), which is a measure of the imbalance between incoming radiation and outgoing radiation triggered by a change in the atmosphere’s composition.
According to the researchers, positive RF causes a warming, while negative RF brings about cooling. The data showed that positive RF is caused by road and aircraft emissions, while negative RF is triggered by shipping emissions.
The QUANTIFY project is expected to end in February 2010.