Slide 1The famous “hockey stick”Slide 3Slide 4Slide 5Average Global TemperaturesSlide 7Slide 8First Conclusions …Slide 10Slide 11So, what did happen since 1850 ?Slide 13Slide 14And farther back in time …The famous “hockey stick”Slide 17nevertheless…Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25homework assignment…Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33“cultural” evidence…Slide 35glacial retreat…Grinnell Glacier, Glacier Natl. ParkSlide 38Slide 39some final thoughts for the week…Slide 41The Earth’s temperature over the past 2000 yearsThe famous “hockey stick”http://www.grida.no/climate/ipcc_tar/wg1/pdf/WG1_TAR-FRONT.PDFhttp://en.wikipedia.org/wiki/Image:Instrumental_Temperature_Record.pngAverage Global Temperatures•last 150 years or so based on instrumental record•how to calculate an average•how to deal with data inconsistencieshttp://alignment.hep.brandeis.edu/Hashemi/Climate/First Conclusions …•establishing an average even for an instrumental record is difficult•there should be quite a bit of variation (or error) in the data•you might want to take a long hard look at what people show youSo, what did happen since 1850 ?•general warming trend since 1900 or so•peak in temperature around WWII (1940’s)•drop in temperatures in 1950’s•general rise since then•how much change ?•error of estimate ?•cause(s) ?claim: most of the increase in temperature occurred before 1940 when industrial production was insignificant…•Jones, P.D. and Moberg, A. (2003). "Hemispheric and large-scale surface air temperature variations: An extensive revision and an update to 2001". Journal of Climate 16: 206-223.And farther back in time …The famous “hockey stick”http://www.grida.no/climate/ipcc_tar/wg1/pdf/WG1_TAR-FRONT.PDFnevertheless…•reconstructions of past temperatures are difficult, even if instrumental records are available•slightly different approach:look at effects of climate change–plant migrations–geologic features (e.g., glaciers)–societal changeWheatstacks, Claude Monet (1890)paleoclimate for the art historians…Number of reported sea floods per century in the North Sea region. (Source: Lamb, 1995)http://thames.me.uk/s00050_files/Frost%20fair%201789.jpgThe Hunters in the Snow, Pieter Brueghel (1565)The Jewish Cemetery, Jacob van Ruisdale (1657)Large Enclosure, Caspar David Friedrich, 1832Stour Valley, John Constable (1840)homework assignment…•due December 1st 5 PM (on –line)•go to course website and follow the link to the 6. homework assignment“cultural” evidence…•how reliable is it really ?•e.g., Medieval warm period and vineyards in England (as pointed out by some folks)•what stuff did these guys drink in the 1300’s ?•what are they growing in England today?glacial retreat…http://en.wikipedia.org/wiki/Retreat_of_glaciers_since_1850Grinnell Glacier, Glacier Natl. Park1935 1981 1998 2005images compiled at: http://en.wikipedia.org/wiki/Retreat_of_glaciers_since_1850some final thoughts for the week…•magnitude of absolute changes is important•rate of change is important•to put it in perspective:–yes, the earth’s climate has been warmer–yes, it also has been a lot cooler–the present warming occurs during an interglacial (already warm) period–yes, the polar bear survived previous warming events, but many other species did