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12B. ClimateChange

12B. ClimateChange - What is Weather Earths atmosphere...

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What is Weather? Earth’s atmosphere - mixture of gases called air. Atmosphere governs physical conditions of weather - what is happening outdoors in a specific place at a given time. – Temperature, Pressure, Moisture content, Wind. – Short period of time (minutes to hours)
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What is Climate? Average weather for a particular region and time period. – 30 years e.g. Seattle has a rainy climate.
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Global Climate “Climate” - persistent weather patterns – Patterns include long-term (30 yrs) regional trends – Trends include maxima, minima, ranges, etc. • Temperature • Pressure • Humidity • Precipitation Wind conditions • Storms
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Has global warming stopped? “Global warming stopped in 1998” LOTS of Google “hits”. Here are temperatures from 1998 to 2004, from GISTEMP. No warming there, right??? (Actually, a regression on this shows warming, but not with especially high confidence.) Warmer 1998 2004 Year
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Source: Gavin Schmidt, NASA GISS Actually, global warming is clearly continuing. Be careful of cherry- picking, and weather. Climate usually a 30-year average, for good reasons! Previous slide
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What is Climate Change? 1 Any significant change in measures of climate lasting for an extended time period (decades and longer) The term can refer to both natural and human induced variability 1 http://www.epa.gov/
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What is Global Warming? Common usage - warming resulting from increased emissions of greenhouse gases Average increase in temperature of atmosphere near Earth’s surface and troposphere One of many kinds of climate change that Earth has gone through in past, and should continue into the future
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Paleoclimate Cycles During most of Earth history, global T was 8-10 o C warmer than today, but there have been a few long periods of sustained globally cold periods. ice ages: 2500 Myr, 700 Myr, 300 Myr and past 42 Myr
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Over the past 2.5 million years, we have had a serries of ice ages, the last from 20-26,000 years ago. We live in an interval of unusually warrm climate over the past 10,000 years called the Holocene
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What is Global Warming? Common usage - warming resulting from increased emissions of greenhouse gases. Average increase in temperature of atmosphere near Earth’s surface and troposphere Six warmest years all occurred since 1998, and 15 warmest years have all occurred since 1988
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IPCC February 2007 Report “unequivocal” that Earth’s climate is warming ”very likely” that emissions of heat- trapping gasses from human activities have caused “most of the observed increase in globally averaged temperatures since the mid-20th century.”
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Higher CO 2 : Anthropogenic Influence
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CO 2 is rising. We burn lots of fossil fuel (~$2000 each, each year, just to import oil), and we see CO 2 from our tail pipes in the air and the ocean. This is the Keeling Curve showing the rise since 1958. The wiggles are the “breathing” of the seasons (spring leaf growth and autumn leaf death).
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