Projections of Future Anthropogenic Climate Change

Abstract

3.1 Introduction to Future Anthropogenic Climate Change Projections This chapter focuses on summarising projections of future anthropogenic climate change for the Baltic Sea Basin. This includes the science of climate change and how future projections are made, taking into account anthropogenic influence on greenhouse gases (GHG). Looking forward to-ward future climates requires using state-of-the-art modelling tools to represent climate processes. The chapter begins with an overview of the current understanding of global anthropogenic cli-mate change and how this is applied for projec-tions into the 21 st century. Important processes for the global climate and their representation in global climate models (GCMs) are introduced. Projected global changes are summarised and then put into specific context for the Baltic Sea Basin. This includes discussion of the performance of such models for the present climate. A range of future climate outcomes is presented, originating from using several GCMs and from using a set of differ-ent projected GHG emissions scenarios. Due to the coarse scales of GCMs, downscaling techniques are used to produce detailed results on regional to local scales. Methods for both statis-tical downscaling and dynamical downscaling us-ing regional climate models (RCMs) are described. Results for the key climate variables of precipita-tion and temperature, and others, are summarised for the Baltic Sea Basin. Projections of anthro-pogenic climate change are further coupled to hy-drological and oceanographic processes via mod-els to assess basinwide climate change impacts. Hydrological modelling shows how climate-driven changes impact on the distribution and timing of runoff into the Baltic Sea. Oceanographic mod-elling shows corresponding changes in water tem-perature, sea ice, salinity and sea levels.