Lecture 5-6 - Climate Change - Past and Present Patterns of...

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Patterns of heat transport in the atmosphere (weather) and in the oceans (surface currents and thermohaline circulation) are chaotic, variable on time scales of hours to years. Climate is the long-term average of weather in a specific location. Climate variation also occurs, but on longer time scales (decades to millennia) Evidence for climate change in the past? Climate Change - Past and Present
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Climate Change - Past and Present What are the indications that there were major global climate change events in the past? paleoclimatology methods for estimating ancient climates What are the factors that can cause global climate change? related to heat budget of the earth Four important questions
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Climate Change - Past and Present Can we relate ancient climate change events to specific causes? tests for current models of climate change What is the evidence for global climate change at the present time, and for predicting change in the future? methods and data analysis computer simulations of climate change
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Climate Change - Past and Present Paleoclimatology The study of the earth’s climate over geologic time earth is 4.5 billion years old can study last few million years at best accuracy decreases with time before present Which climate parameters can be estimated? temperature atmospheric CO 2 sea level
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Climate Change - Past and Present 10 0 10 1 10 2 10 3 10 4 10 5 10 6 10 7 10 8 Years Before Present fossils reefs plankton, isotopes glacial features isotopes pollen, shorelines tree rings documents thermometers satellites sedimentary rocks ocean sediments terrestrial deposits polar ice lakes, bogs wood historical data instrument records Evaluating Past Climates
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Climate Change - Past and Present Paleoclimatology Sea level – observation of ancient beaches above or below current sea level CO 2 – analysis of gas bubbles trapped in ice or sediments Temperature – analysis of oxygen isotope ratios in ice or sediments
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Climate Change - Past and Present Estimating the Earth’s past temperatures by measuring the ratio of oxygen isotopes in ice or sediments. Isotopes are atoms with the same chemical properties differing in their weight (atomic mass) same number of protons and electrons, different number of neutrons
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Climate Change - Past and Present What are some isotopes you may have heard of ? 12 C (the common, stable isotope of carbon) and 14 C (the less common radioactive isotope) used in radiocarbon dating techniques 235 U (the most common isotope of uranium) and 238 U (the isotope used in nuclear reactors and atomic bombs)
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Climate Change - Past and Present Oxygen isotopes: 16 O versus 18 O Past temperatures can be estimated by using measuring the ratio of 16 O to 18 O present in a sample.
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This note was uploaded on 12/16/2009 for the course BIOPL 2400 taught by Professor Silva,t. during the Fall '08 term at Cornell.

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Lecture 5-6 - Climate Change - Past and Present Patterns of...

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