EU-funded researchers have issued a report estimating the impact of road, aircraft and shipping emissions on the Earth’s atmosphere as part of the QUANTIFY (’Quantifying the climate impact of global and European transport systems’) project.

The report explains how ozone pollution in the troposphere (the lowest atmospheric level) wreaks havoc on people’s well-being and burns large holes in farmers’ pockets. Ozone pollution also acts as a strong greenhouse gas (GHG), and while it may occur naturally, sunlight and pollutants give it a helping hand.

The QUANTIFY partners applied 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 commonly referred to as the ’detergent’ of the troposphere because it reacts with and helps remove many pollutants and greenhouse gases like carbon dioxide.

Led by the German Aerospace Center (DLR), QUANTIFY found that traffic emissions resulting in high ozone levels rear their ugly head most during the summer season in the northern hemisphere. The greatest impact extends from the eastern US - and across the Atlantic - to western Europe. The researchers also discovered that changes are around 50% lower in the southern hemisphere compared to the northern hemisphere.

The biggest culprit is shipping emissions. According to the partners, these emissions have the biggest effect on the lower troposphere and are responsible for more than half of the transport-induced changes in the ozone in various regions.
Aircraft emissions, meanwhile, may not play a huge role in the upper troposphere, but they dominate the effect of traffic on the ozone in the tropopause, which marks the boundary between the troposphere and the stratosphere (the second major layer of Earth’s atmosphere).

Another contributor is road traffic, which affects the northern upper troposphere. The impact is greatest during the northern summer. Conversely, the relative contributions from each traffic sector are more or less the same during the northern winter, the experts said.

Emissions from ships have the largest impact on global OH levels in the lower troposphere, and thus the ’largest impact on reducing methane lifetime as they are released in relatively clean regions over the sub-tropical and tropical oceans where OH is highly sensitive to traffic emissions’, the data showed.

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 brought on by road and aircraft emissions, while negative RF is triggered by shipping emissions. Shipping emissions negatively affect eutrophication (a process where water bodies receive excess nutrients that stimulate excessive plant growth), health and acidification.

The EU is determined to cut emissions. It wants carbon dioxide emissions to be reduced by 20% by 2020 compared to 1990 levels.

Participating in QUANTIFY, which is expected to end in February 2010, are Charles University, Prague (Czech Republic), the Cambridge Environmental Research Consultants (UK), the National Meteorological Administration (Romania), the University of Szeged (Hungary) and Airbus France.