Hedegaard, G.B. 2012. Future air pollution levels in the Northern Hemisphere. PhD thesis. Niels Bohr Institute, University of Copenhagen, Department of Environmental Science, Aarhus University and Danish Climate Centre, Danish Meteorological Institute. 145 pp. http://www2.dmu.dk/pub/PHD_GBH.pdf
Climate change impacts the atmospheric composition of the atmosphere, since the concentration of chemical species in the atmosphere depends on different meteorological parameters and hence is sensitive to changes in the climate. Furthermore past, present and future anthropogenic emissions of air pollutants alter the chemical composition of the atmosphere. In this thesis the sensitivity of ozone and its related precursors are investigated together with black carbon, and other particles with respect to the individual impacts from climate change and changes in future anthropogenic emissions.
A model framework has been setup based on the Danish Eulerian Hemispheric Model (DEHM), which is an Eulerian Atmospheric Chemistry Transport Model (ACTM). The DEHM model has been driven on past, present and future meteorology projected by the Atmosphere-Ocean Climate model ECHAM5/MPI-OM. The applied climate simulation covers 340 year and has been forced with the SRES A1B emission scenario in the future.
Within the climate change-air quality research community it is common to do time-slice experiments. In this thesis attention is paid on the precautions and pre-analysis of the climate data that need to be carried out before using the data for impacts studies. Specifically, four time-slices have been chosen (1890s, 1990s, 2090s and 2190s) to represent the differences between the three centuries. Empirical Orthogonal Function (EOF) analysis and other statistical tools have been used in order to verify the use of time-slices for simulations with the ACTM. It is concluded that it is scientifically sound to use the specific four time-slices. The chance of choosing an abnormal decade from the climate simulation with respect to the internal variability is only 4 out 34 within a 10 % significance level.
Several simulations have been carried out with the DEHM model forced with different combinations of meteorology and emission scenario data. The emission inventories used are the EMEP, EDGAR and GEIA databases and the newly developed RCP4.5 emission scenario. The impact of climate change on the future surface ozone concentration has thoroughly been evaluated with respect to the different sinks and sources of surface level ozone. It was found that the changes in future ozone concentrations due to climate changes lead to a general decrease in the remote and semi-remote areas. In urban areas the ozone concentration will increase due to increased production from increased biogenic emissions of VOCs.
The largest changes in surface level ozone are found to happen in the current century. However, the tendencies found will continue into the 22nd century. The fate of ozone is in general driven by two competing effects; ozone destruction due to increased water vapour in the clean areas and ozone production in the more polluted areas. The impact from climate change implies a promoting effect on production on biogenic isoprene which in the presence of NOx results in increase in the ozone concentration.
The addition of changes in the anthropogenic emissions prescribed by the RCP4.5 emission scenario, result in a different picture. The signal from the changes in anthropogenic emissions dominates for most species in most areas. However, opposing effects from impact of climate change and emission change are found for some species implying a so called “climate penalty”; to reach a certain reduction level further actions needs to be taken into account in air pollution regulation in order to counteract the impact of climate change.
