Petroleum and shipping activities at higher latitudes have increased considerably over recent years, and a significant further increase is expected. Melting of sea ice will open opportunities for new shipping routes and lengthen the navigation season of e xisting routes, as well as open new areas for oil/gas production. We will assess, in terms of radiative forcing, the climate impact of increased oil/gas and shipping activity in the Arctic. Future emissions will be estimated for scenarios of development o f global shipping and oil/gas exploration. Of particular interest are the potential region-specific effects; thus emphasis will be put on short-lived species, such as primary (BC and OC) and secondary particles (sulfate, secondary OC, and nitrate), and O3 in addition to long-lived GHGs. The timing and location of the emissions of short-lived species will be taken into account. A global 3-D chemical transport model that includes a comprehensive photochemical scheme and modules for sulfate, BC and OC aeroso ls, and secondary OC will be applied. Radiative forcing simulations will be performed for the long- and short-lived gases, as well as for the direct and indirect aerosol effects. The impact of aerosols on clouds will be based on observational studies of h ow aerosols change the cloud droplet radius and cloud cover. The climate impact of oil and gas exploration will be normalized by activity data to enable a comparison with similar production in other regions. A similar approach will be taken for shipping t o compare with other and alternative shipping routes. The overall effect including lower fuel consumption from ships taking shorter routes between Europe and Asia will be estimated. The project will provide a policy relevant assessment of the overall clim ate effect of a shift of activities from other regions to the Arctic, and particularly whether emissions occurring in the Arctic region will be more harmful for climate than emissions occurring at lower latitudes.