Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Geologic Record of Climate Change: The past informing the near future From: The Day After Tomorrow, 20th Century Fox, 2004 http://www.ncdc.noaa.gov/paleo/paleo.html Outline: • Evidence for Natural Climate Change • Evidence for Anthropogenic Climate Change Climate Change over Geologic Time How do we know climate varied over Geologic Time? The Importance of TIME: How accurate is the climate data? • All the climate indicators we have discussed so far depend on knowing the duration of time over which they grew or were deposited • The higher the resolution of the climate archive, the more important it is to know the time frame maybe to within years • As the climate archives get older (i.e., deposited millions of years ago or more), we not only have trouble dating the archive but we are not sure we have a continuous record due to the ravages of weathering and erosion of rocks • Consequently, old climate archives give us general climate knowledge at best Cold Environments: Pleistocene Glaciation Pleistocene (15 kyr) glacial till Pre-Cambrian (>1 billion yrs) glacial tillite Humid Environments: Pennsylvanian Coal Forest Tree ‘bark’ 300 million yr. old tree Arid Environments: Wind Arid Environments: Water Sahara Desert Triassic Navaho SS – Zion NP Present-day and Permian (255 mya) salt deposits Warm, marine environments: Pleistocene coral rubble Great Barrier Reef Permian Reef, Texas Ancient Climate Records Looking for the Climate “Tape recorder”: •The concept of a climate archive: •A process that records climate directly or indirectly •Useful for time scales and time periods greater than human instrumental recording (i.e., before 1800) • How can climate be recorded in deep time? • What kinds of processes might give us a record of climate? • How long of a record might we obtain? • The basis for all this is UNIFORMITARIANISM: The Present is the Key to the Past The last millennial temperature trend: Avg. 1961-1990 = 0.0 Climate Proxies Historical Record Instr. Record Climate Proxies with High Resolution records: •Ice Cores Gas bubbles trapped in ice Result of the isotopic “fractionation” process on marine sediments and ice Terrestrial Climate indicators • Lacustrine (Lake) levels Present Lake Glacial Shore (16,000 yr BP) 200 million year old lake seds POLLEN Historical Climate Proxies with High Resolution records: • Dendochronology – Tree Rings Complacent Sensitive Cross-dating of trees Recent (Instrumental) Climate Change Grinnell Glacier, Glacier National Park, Montana 1938 1981 1998 2005 ARCTIC ICE SHEET MELTING 1953-2007 If CO2 is rising what should happen to global temperature? Hadley Centre/UEA-CRU data