SIO40lecture17

SIO40lecture17 - SIO 40 Life and Climate on Earth Nov. 12,...

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SIO 40 – Life and Climate on Earth Nov. 12, 2010 Lecture 17 – Climate Change Basics, Part II
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Lecture Outline - Climate modeling with and without anthropogenic forcing - The last interglacial – a test case? -Climate happenings and their relation to human-induced global warming
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From IPCC AR4 Modeling recent global mean temperature anomalies, with and without anthropogenic forcing Clearly, global climate models that only include natural forcings such as changes in solar input and volcanic eruptions (bottom left) do not replicate observed temperature trends as well as models that incorporate both human and natural forcings (top left). This is strong evidence that both natural and human forcings have impacted climate over the past century.
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Regional trends replicate global trends We see the same pattern repeated on a regional level – to accurately simulate observed temperature changes, climate models need to incorporate both natural and human climate forcings.
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Anthropogenic forcing is needed to replicate not just magnitude, but observed patterns of warming Only climate models that include both natural and human forcings replicate the observed pattern of warming surface temperatures, with greater temperature increases in the Northern Hemisphere.
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Can we trust climate models? The last interglacial as a test case Global climate models being used to project future climate change suggest that the Arctic is particularly sensitive to global warming, with projected temperature increases ranging from about 1-4 ° C, with large reductions of Arctic sea ice. The last interglacial period, 130,000 years Ago, is the most recent time period when the Arctic experienced similar conditions, due to the Northern Hemisphere receiving 10% more solar radiation than it does today because of changes in Earth’s orbit. The ability of climate models to reproduce Arctic conditions similar to those during the last interglacial under the same climate forcings should increase confidence in their projections for the future. Top right shows proxy-based temperature observations of Arctic temperature anomalies relative to today for the last interglacial. Bottom right shows model-based maps of Arctic temperature anomalies relative to today for the same time period. The agreement between proxy observations and model simulations of the Arctic for the last interglacial indicates that global climate models are likely correct in their projections of significant Arctic warming in the coming century as a result of human-induced global warming.
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SIO40lecture17 - SIO 40 Life and Climate on Earth Nov. 12,...

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