Part A: Global and Sectoral Aspects: Volume 1, Global and Sectoral Aspects: Working Group II Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change

Human interference with the climate system is occurring. [WGI AR5 2.2, 6.3, 10.3-6, 10.9] Climate change poses risks for human and natural systems (Figure TS.1). The assessment of impacts, adaptation, and vulnerability in the Working Group II contribution to the IPCC’s Fifth Assessment Report (WGII AR5) evaluates how patterns of risks and potential benefits are shifting due to climate change and how risks can be reduced through mitigation and adaptation. It recognizes that risks of climate change will vary across regions and populations, through space and time, dependent on myriad factors including the extent of mitigation and adaptation. [INSERT FIGURE TS.1 HERE Figure TS.1: Climate-related hazards, exposure, and vulnerability interact to produce risk. Changes in both the climate system (left) and development processes including adaptation and mitigation (right) are drivers of hazards, exposure, and vulnerability. [19.2, Figure 19-1]] Section A of this summary characterizes observed impacts, vulnerability and exposure, and responses to date. Section B examines the range of future risks and potential benefits across sectors and regions, highlighting where choices matter for reducing risks through mitigation and adaptation. Section C considers principles for effective adaptation and the broader interactions among adaptation, mitigation, and sustainable development. Box TS.1 introduces the context of the WGII AR5, and Box TS.2 defines central concepts. To accurately convey the degree of certainty in key findings, the report relies on the consistent use of calibrated uncertainty language, introduced in Box TS.3. Chapter references in square brackets indicate support for findings, paragraphs of findings, figures, and tables in this summary.