Hansen, K.M., Christensen, J.H., & Brandt, J. 2014. The effect of climate change versus emission change on future atmospheric levels of POPs and Hg in the Arctic. Aarhus University, DCE – Danish Centre for Environment and Energy, 68 pp. Scientific Report from DCE – Danish Centre for Environment and Energy No. 92 http://dce2.au.dk/pub/SR92.pdf

Summary

We have performed a series of simulations using the Danish Eulerian Hemispheric Model to investigate how predicted climate changes and emissions change will affect the atmospheric transport to the Artic and the environmental fate within the Arctic of persistent organic pollutants (POPs) and mercury (Hg). We have furthermore studied the importance of the three major source areas: Europe, Asia and North America as well as the importance of re-emissions from previously deposited compounds. The simulations all apply input from one possible climate scenario, the IPCC Special Report on emissions Scenarios (SRES) A1B climate scenario, which predicts and increase in global mean temperature of 3°C by the end of the 21^st century. Under this climate scenario, the applied model predicts an 18% decrease in Hg deposition to the Arctic, an increase in mass of hexachlorocyclohexanes (HCHs) with up to 30% and a change in mass of polychlorinated biphenyls (PCBs) between -10% and +20% depending on the congener by the end of the 21^st century. The applied emission change scenarios predicts between a 6% increase (status Quo scenario) and a 37% decrease in Hg deposition to the Arctic by 2050, whereas the changes in PCBs ranges from a decrease of 88% for PCB28 to an increase of 5% for PCB180 by the end of 2100. The combined effect of changes in climate and emissions are not additive for the PCBs. Asia is the most important source area for Hg in the Arctic, whereas Europe is the most important source area for POPs. Re-emissions contribute to between 27% and 77% of the mass of POPs found in the Arctic. Overall the effect of climate change on the atmospheric transport and fate of POPs and Hg to the Arctic appears to be moderate under the studied climate scenario. Changes in emissions have a larger effect on the atmospheric transport and fate of POPs and Hg. However, changes in the climate affect the possible effect from changed emissions. For some of the studied compounds the climate change acts to increase the effect of changed emissions and for others it acts to decrease the effects of changed emissions.