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Chapter10(2) - Earthquake of the day Ch 10-Climate Climate...

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Earthquake of the day
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Ch. 10--Climate, Climate Change, and Weather Principles Earth’s climate history over the last 500,000 years How ancient temperatures are measured Controls on Global Climate Amount of incoming solar radiation controlled by Earth’s orbital parameters: Eccentricity, •Tilt, • Wobble Amount of heat retained controlled by: Surface reflectivity • Greenhouse effect Sources of greenhouse gases Circulation Patterns Human impacts on climate Human activities involving greenhouse gases and surface reflectivity Recent trends in global greenhouse gas abundance and global temperatures Predicted effects of global warming (increased land and ocean temperatures, precipitation changes, arctic thaw, sea level rise, changes in ocean circulation patterns) Mitigation strategies Public and scientific opinion on climate change and human influence Weather principles Heat transfer Atmospheric layers Air motion (motion controls by temperature, pressure, fronts, and other obstacles) Global air circulation patterns and the Coriolis effect The hydrologic cycle Precipitation
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Last 500,000 Years of Climate History Climate change has been dominated by a ~100,000 year cycle, with glacial periods lasting 70-100 thousand years punctuated by brief warm interglacials lasting 10-20 thousand years GLACIAL GLACIAL GLACIAL GLACIAL Interglacial Interglacial Interglacial Interglacial Antarctica Greenland
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Presently, we are in an interglacial (warm) period The glacial ice masses were at peak extent ~20,000 years ago, covering ~27% of today’s land, including all of Canada and part of the northeastern US. Sea level was 130 m lower than today
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How do we measure ancient temperatures? Instrumentation to measure temperatures have only existed in the last few hundred years. To determine long-term trends in global temperatures, scientists use “climate proxies”, estimates of temperature based on natural phenomenon. Two major types of climate proxies are used: oxygen-isotope ratios ( 18 O: 16 O) in ice or sediment cores, or in corals tree ring widths vary with changes in temperature or precipitation
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Using oxygen-isotope ratios to measure ancient air temperatures Light Heavy Water vapor (H 2 O) with 16 O condenses slower Water vapor (H 2 O) with 18 O condenses faster 8 neutrons 10 neutrons Isotope: different varieties of the same element, with different numbers of neutrons Oxygen has 8 protons and either 8 or 10 neutrons
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Oxygen-isotope ratios ( 18 O: 16 O) are preserved in: glacial ice sedimentary material (which contains marine organisms’ shells) corals Using oxygen-isotope ratios to measure ancient temperatures
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Last 500,000 Years of Climate History Climate change has been dominated by a ~100,000 year cycle, with glacial periods lasting 70-100 thousand years punctuated by brief warm interglacials lasting 10-20 thousand years GLACIAL GLACIAL GLACIAL GLACIAL Interglacial Interglacial Interglacial Interglacial Antarctica Greenland
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