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This Class: Short-term climate change • Climate – 30 year “average” weather conditions • Short-term – over the last 1000 to 12,000 years • Climate records • Causes of climatic variation • Past climate change Records of climate Records of climate • Historical (human) records – instrumental – written observations • maritime records – paintings • 12,000 paintings • 1400-1967 Records of climate, cont. • Phenological observations – agricultural records • price of rye in Germany – bird migrations Dendrochronology • dating of past events through study of tree ring growth • thickness of the tree ring indicates growing season conditions – precipitation building a chronology • overlapping rings from different trees • Bristlecone pine chronology is 9000 years long – long lives - 4,767 years old Lake and ocean sediments • Sediments record environmental conditions present when they were deposited Clues in the sediments • pollen - vegetation type • skeletons of small organisms - water chemistry, temperature • type of organisms windiness • chemistry of sediments or organisms – temperature, precipitation Elk Lake, Minnesota • http://geology.cr.usgs.gov/pub/factsheets/fs-0059-99/ Signals in Elk Lake sediments • diatoms - heavy, need wind to keep afloat = windy • quartz - blown into the lake = windy • sodium – retained in soils, not washed away = dry • pollen - vegetation type • 8,500 to 4000 years ago it was drier, prairie vegetation Coral reefs • growth bands • chemistry records sea temperature (oxygen isotopes) Coral core and X-ray with growth bands slide/ coral core and x-ray oxygen isotope Calibration curve slide/ calibration curve of 18O and SST in coral two prolonged La Niña events Oxygen isotope index -5.3 -4.9 -4.5 -4.1 -3.7 1840 1860 1880 1900 1920 1940 1960 1980 2000 Period of instrumental data Ice cores • • • • volcanic eruptions - ashes atmospheric gasses - small air bubbles temperature - oxygen isotopes windiness - dust • http://www.pages. unibe.ch/products/ overheads2/icecor es.html Greenhouse gasses in ice cores Some causes of climatic variation • • • • Ocean circulation Sunspots Volcanic eruptions Atmospheric conditions – El Nino Southern Oscillation Currents and climate • Miller 2.167 Sunspots • Dark spots (cool areas) that move across the surface of the sun* • Every 11 years there is a period called a “solar maximum” with lots of sunspots and solar flares • Today’s sunspot number http://www.sunspotcycle.com/ *But these dark areas are surrounded by hotter rings that more than make up for the difference in radiation Fewer sunspots seem to be associated with: • lower temperatures • more severe winters • glacial advances Volcanoes • blast gasses (sulfur dioxide) and ash into the lower stratosphere. • strong winds in stratosphere blow material around the world. • sulfur dioxide combines with water to for sulfuric acid aerosols (fine droplets) How does this affect climate? Volcanic eruption Volcanoes, cont. • scatters incoming radiation back to space • reduces heating of earth’s surface • last up to four years Mt Pinatubo, Philippines Pinatubo sulfur dioxide cloud June 17, 1991 June 19, 1991 Pinatubo sulfur dioxide cloud Pinatubo stratospheric aerosols 40 days before 40 days after 20 months after • Average temperatures dropped by 0.2 to 0.5 oC for 1 to 3 years El Niño – Southern Oscillation (ENSO) • Oscillation of southern high and low pressure zones – Weakening of Peruvian high pressure zone – Weakening of Indonesian low pressure zone – Weakening of southeast trade winds – Affects local climate Sea surface temperatures off South America Upwelling off South America • 9.12a 2.209 El Niño sea temperature El Niño year • 9.12b 2.207 ENSO teleconnections – affects on global climate Segar, 1998 Past periods of climate change • Medieval Warm Period • Little Ice Age Insert temperature recoreds The Medieval Warm Period • 1000 to 1300 AD • regional warming (not necessarily global) • Longer and warmer growing season – grapes in England • Higher treelines • Warmer sea surface temperatures in North Atlantic • approx. 1o C warmer than present Viking settlement on Iceland and Greenland from 800 to 1200 The Little Ice Age • Very cold climate between 1560 and 1890 • Greater frequency of storms • Glacial advances 1560-1610,1816-1890 • Wheat prices higher in Europe • Paintings darker, cloudier Iceland • Population declines in Iceland indicated by tax records • shift from grains to barley (short growing season) to no grains • fishing failed as fish migrated southward due to water temperatures. • Height declines – from 5’8” in 900s to 5’6” in 1700s in Iceland Iceland population 100000 barley no grain 0 1000 1200 1400 1600 1800 2000 Greenland • 1300 highest population (3000) • Poor harvests, fewer livestock • Increase in sea ice decreased trade • Settlements abandoned • Height decrease from 5’7” to < 5’ by 1400 Intro to activity: The Palmer Drought Severity Index Based on temperature, precipitation, and tree ring records • http://www.ngdc.noaa.gov/paleo/drought/drgh t_pdsi.html • http://www.ngdc.noaa.gov/paleo/pdsiyear.htm l Locations of tree rings •http://www.ngdc.noaa.gov/paleo/pdsiyear.html Pinatubo sulfur dioxide cloud 3 months after eruption Little ice age • glacial advances http://www.ucar.edu/learn/1_2_1.htm • for pollen, tree ring w/ fire scar slide/ drilling coral Drilling a massive coral Many pictures of paintings, wheat prices, etc. • http://www2.sunysuffolk.edu/mandias/lia /little_ice_age.html