This is Chapter 18 of the Arctic Climate Impact Assessment. Lead Author: Gunter Weller; Contributing Authors: Elizabeth Bush,Terry V. Callaghan, Robert Corell, Shari Fox, Christopher Furgal, Alf Håkon Hoel, Henry Huntington, Erland Källén, Vladimir M. Kattsov, David R. Klein, Harald Loeng, Marybeth Long Martello, Michael MacCracken, Mark Nuttall,Terry D. Prowse, Lars-Otto Reiersen, James D. Reist, Aapo Tanskanen, John E.Walsh, Betsy Weatherhead, Frederick J.Wrona

This chapter provides a brief summary of the main conclusions of the seventeen preceding chapters of the Arctic Climate Impact Assessment (ACIA). The chapter has three main parts. The first part contains the conclusions of the assessment discussed chapter by chapter. Observed climate and ultraviolet (UV) radiation trends (Chapters 2 and 5) are summarized, using both scientific and indigenous (Chapter 3) observations, and information from the latest assessments by the Arctic Monitoring and Assessment Programme^[1] and the Intergovernmental Panel on Climate Change^[2]. Projections of climate change over the 21st century, based on emissions scenarios and computer model simulations (Chapter 4) are described, as are the observed and projected changes in stratospheric ozone and UV radiation levels (Chapter 5). Next, the chapter summarizes arctic-wide consequences of climate change, by examining impacts on the environment (Chapters 6, 7, 8, and 9), on people’s lives (Chapters 10, 11, 12, 15, and 17), and on economic sectors of importance in the Arctic (Chapters 13, 14, and 16). These impacts cut across the entire Arctic and are generally not dependent on resolving regional details. For example, the timing, intensity, and magnitude of the melting of snow and ice in a warmer climate will have widespread implications for the entire Arctic and the global environment, even if these changes vary regionally.

Projected major large-scale environmental changes in the Arctic are illustrated in Fig. 18.1, which shows the existing and projected boundaries for summer sea-ice extent, permafrost, and the treeline. The likely changes associated with these shifts are many and dramatic, as described in the preceding chapters of this assessment. For example, the map shows that the treeline is projected to reach the Arctic Ocean in most of Asia and western North America by the end of the century. This is likely to lead to a near total loss of tundra vegetation in these areas, with important consequences for many types of wildlife. The consequences of the permafrost thawing and sea-ice reductions shown in Fig. 18.1 are equally dramatic.

The second part of the chapter is a synthesis of impacts on a local and regional basis, providing details on four different regions of the Arctic. A regional emphasis is necessary because the Arctic covers a large area and so experiences significant regional variations in the changes in climate that will lead to different impacts and responses. Different regions also have different social, economic, and political systems, which will each be influenced differently, causing vulnerability and impacts to differ to a large extent on the basis of geopolitical and cultural boundaries. The four regions for which results are presented are:

• Region 1: East Greenland, the North Atlantic, northern Scandinavia, and northwestern Russia;
• Region 2: Siberia;
• Region 3: Chukotka, the Bering Sea, Alaska, and the western Canadian Arctic; and
• Region 4: the central and eastern Canadian Arctic, the Labrador Sea, Davis Strait, and West Greenland.

The rationale for selecting these four broad regions includes climatic, social, and other factors, and is discussed in section 18.3.

The final part of the chapter addresses cross-cutting issues that are important in the Arctic. These are discussed in several chapters of the assessment, although usually in the context of the main topic of the chapter, and include the carbon cycle, biodiversity, and extreme and abrupt climate change.

Changes in climate and UV radiation in the Arctic will not only have far-reaching consequences for the arctic environment and its peoples, but will also affect the rest of the world, including the global climate. The connections include arctic sources of change affecting the globe, e.g., feedback processes affecting the global climate, sea-level rise resulting from melting of arctic glaciers and ice sheets, and arctic-triggered changes in the global thermohaline circulation of the ocean.

The Arctic is also important to the global economy. There are large oil and gas and mineral reserves in many parts of the Arctic, and arctic fisheries are among the most productive in the world, providing food for millions (see section 18.2.2.3). Climate change is likely to benefit north–south connections, including shipping, the global economy, and migratory birds, fish, and mammals that are important conservation species in the south. The Arctic plays a unique role in the global context and climate change in the Arctic has consequences that extend well beyond the Arctic.

Chapter 18: Summary and Synthesis of the ACIA
18.1. Introduction
18.2. A summary of ACIA conclusions
18.3. A synthesis of projected impacts in the four regions
 18.4. Cross-cutting issues in the Arctic 
18.5. Improving future assessments
18.6. Conclusions

References

NOTE:This chapter is a summary based on the seventeen preceding chapters of the Arctic Climate Impact Assessment and a full list of references is provided in those chapters. Only references to major publications and data sources, including integrative regional assessments, and some papers reporting the most recent developments, are listed.

1. ^ AMAP, 1998. Assessment Report: Arctic Pollution Issues. Arctic Monitoring and Assessment Programme, Oslo, 859p.
2. ^ IPCC, 2001. Climate Change 2001: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, 1032p.