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The effects of global warming are the environmental and social changes caused (directly or indirectly) by human emissions of greenhouse gases. There is a scientific consensus that climate change is occurring, and that human activities are the primary driver.〔 . Archived (14 July 2014 ). 〕 Many impacts of climate change have already been observed, including glacier retreat,〔Cramer, W., ''et al.'', Executive summary, in: (Chapter 18: Detection and attribution of observed impacts ) (archived (18 October 2014 )), pp.982-984, in 〕 changes in the timing of seasonal events〔 (e.g., earlier flowering of plants),〔Settele, J., ''et al.'', Section 4.3.2.1: Phenology, in: (Chapter 4: Terrestrial and inland water systems ) (archived (20 October 2014 )), p.291, in 〕 and changes in agricultural productivity.〔 Future effects of climate change will vary depending on climate change policies〔Oppenheimer, M., ''et al.'', ''Section 19.7.1: Relationship between Adaptation Efforts, Mitigation Efforts, and Residual Impacts,'' in: (Chapter 19: Emergent risks and key vulnerabilities ) (archived (20 October 2014 )), pp.1080-1085, in 〕 and social development.〔Oppenheimer, M., ''et al.'', ''Section 19.6.2.2. The Role of Adaptation and Alternative Development Pathways,'' in: (Chapter 19: Emergent risks and key vulnerabilities ) (archived (20 October 2014 )), pp.1072-1073, in 〕 The two main policies to address climate change are reducing human greenhouse gas emissions (climate change mitigation) and adapting to the impacts of climate change.〔Denton, F., ''et al.'', ''Section 20.3. Contributions to Resilience through Climate Change Responses,'' in: (Chapter Climate-resilient pathways: adaptation, mitigation, and sustainable development ) (archived (20 October 2014 )), pp.1113-1118, in 〕 Geoengineering is another policy option.〔 Near-term climate change policies could significantly affect long-term climate change impacts.〔Field, C.B., ''et al.'', Section A-3. The Decision-making Context, in: (Technical summary ) (archived (18 October 2014 )), p.55, in 〕〔 Stringent mitigation policies might be able to limit global warming (in 2100) to around 2 °C or below, relative to pre-industrial levels.〔SPM.4.1 Long‐term mitigation pathways, in: (Summary for Policymakers ), pp.11-15 (archived (2 July 2014) ), in 〕 Without mitigation, increased energy demand and extensive use of fossil fuels〔 Clarke, L., ''et al.'', Section 6.3.1.3 Baseline emissions projections from fossil fuels and industry (pp.17-18 of final draft), in: (Chapter 6: Assessing Transformation Pathways ) (archived (20 October 2014 )), in: 〕 might lead to global warming of around 4 °C.〔 Greenhouse Gas Concentrations and Climate Implications, p.14, in . The range given by Prinn and Reilly is 3.3 to 5.5 °C, with a median of 3.9 °C. 〕〔SPM.3 Trends in stocks and flows of greenhouse gases and their drivers, in: (Summary for Policymakers ), p.8 (archived (2 July 2014) ), in . The range given by the Intergovernmental Panel on Climate Change is 3.7 to 4.8 °C, relative to pre-industrial levels (2.5 to 7.8 °C including climate uncertainty). 〕 Higher magnitudes of global warming would be more difficult to adapt to,〔Field, C.B., ''et al.'', Box TS.8: Adaptation Limits and Transformation, in: (Technical summary ) (archived (18 October 2014 )), p.89, in 〕 and would increase the risk of negative impacts.〔Field, C.B., ''et al.'', Section B-1. Key Risks across Sectors and Regions, in: (Technical summary ) (archived (18 October 2014 )), p.62, in 〕 ==Definitions== In this article, "climate change" means a change in climate that persists over a sustained period of time.〔 , in 〕〔 〕 The World Meteorological Organization defines this time period as 30 years.〔 Examples of climate change include increases in global surface temperature (global warming), changes in rainfall patterns, and changes in the frequency of extreme weather events. Changes in climate may be due to natural causes, e.g., changes in the sun's output, or due to human activities, e.g., changing the composition of the atmosphere.〔 Any human-induced changes in climate will occur against a background of natural climatic variations〔 , in 〕 and of variations in human activity such as population growth on shores or in arid areas which increase or decrease climate vulnerability. Also, the term "anthropogenic forcing" refers to the influence exerted on a habitat or chemical environment by humans, as opposed to a natural process.〔 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Effects of global warming」の詳細全文を読む スポンサード リンク
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