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Contemporary problems in ancient climates
 

Contemporary problems in ancient climates

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    Contemporary problems in ancient climates Contemporary problems in ancient climates Presentation Transcript

    • CONTEMPORARY ISSUES IN THE STUDY OF ANCIENT CLIMATESCLIMATE SCIENCE, STATISTICS AND THE COMPUTATIONAL SCIENCES READING GROUP APRIL 2012
    • anecdote
    • “ It doesnt really seem like winter. It seems more like an unusual fall that kind of lingers on and doesnt go anywhere. ” Jessica Forster Commenting on the mild 2012 winter in Minnesota
    • observation
    • Weather data recorded by the Department of Earth Sciences h p://sokar.geo.umn.edu/weather/
    • The Central England Temperature record is the longest instrumental record of temperature in the world. Degrees celsius relative to the long-term meanSource: Parker et al., Journal of Climate, 1992
    • Source: Goddard Institute for Space Studies, NASA
    • The number of climate stations recording air temperature falls off rapidly prior to AD 1900. Number of stations in the Northern HemisphereSource: Jones et al., Journal of Geophysical Research, 2012
    • anecdote < observations <<
    • ‘Striations’ (scratches) on bedrock near Knife Lake, BWCAWSource: Blue~Canoe
    • Thickness of glacial ice 3000 m IDS Tower 241 m
    • CLIMATE HISTORY OF NORTH AMERICA Younger Demise of Laurentide Dryas Ice Sheet 20 16 12 8 4 0 THOUSANDS OF YEARS AGO Final Drainage of Lake AgassizLAST GLACIAL MODERN MAXIMUM OBSERVATIONS
    • CLIMATE PROXIES ice cores tree rings lake sediments speleothems corals
    • CLIMATE “PROXIES” natural phenomena which are climate-dependent, and which incorporate into their structure a measure of this dependency.Source: Bradley, Paleoclimatology: Reconstructing climates of the Quaternary, 1995
    • Source: Tim Shanahan, University of Texas at Austin
    • Source: Geological Survey of Canada
    • Source: LACCORE, University of Minnesota
    • Source: Stella Cousins
    • “ To anticipate future changes, we must understand how and why climates varied in the past. Dr. Ray Bradley University of Massachuse s ”
    • PALEOCLIMATOLOGYthe study of climate prior to the period of instrumental measurement
    • Global networks of climate proxies have been used to estimate past changes in hemispheric temperature.Source: Commi ee on Surface Temperature Reconstructions for the Last 2,000 Years, National Research Council, 2006
    • How did the ENSO system behave prior to the 20th century?
    • Tree-ring estimates of 1,200 years of Colorado River discharge Meko et al., GRL, 2007
    • OBSERVATIONS PROXIES MODELS
    • “ Each individual proxy provides a record of environmental change, but the process of combining these signals into a spatially averaged temperature signal requires careful statistical evaluation. Commi ee on Surface Temperature Reconstructions for the Last 2,000 Years ” National Research Council
    • ? How can we extract climatic signals froma large, diverse network of noisy proxies thatare distributed irregularly around the planet?
    • Tree-ring display at elementary schoolSource: Tom Swetnam
    • Intermountain bristlecone pine 4,844 yearsSource: Tom Harlan
    • Giant sequoia 3,266 yearsSource: Julie Jordan Sco
    • Eastern white cedar (in Minnesota) 560 yearsSource: Danny Margoles
    • Pinus spp.Source: Paul Schulte
    • Source: Baillie (1982)
    • 755 m3/s847 m 3/s809 m 3/s770 m 3/s823 m 3/s787 m 3/s901 m3/s 3
    • TEMPERATUREhigh growth frozen water low photosynthetic rate low photosynthetic rate higher evaporation shorter growing seasonlow growth cold hot
    • WATERhigh growth reduced cell division flooding reduced cell expansion anoxic conditions C02 starvationlow growth dry wet
    • Single-site reconstruction
    • rain gauges tree ringsSource: Hughes and Funkhouser, 1998
    • “ THERMOMETERS ” TREES ARE NOT OR RAIN GAUGES. Keith Briffa and colleagues
    • 3CHALLENGESIN DENDROCLIMATOLOGY
    • 3 Do climate-sensitive trees (and other proxies) transform climate signals in predictable ways?
    • 2 Is there an optimal approach for recovering low-frequency variability from climate-sensitive tree rings?
    • 1Should paleoclimatic estimates from trees be derivedfrom (a) common pa erns or (b) optimal predictors?
    • Source: Baillie (1982)
    • Network reconstruction
    • “ Continental- and hemispheric-scale networks contain robust synoptic-scale pa erns, which may o en be interpreted in terms of climatic conditions. Dr. Malcolm Hughes ” University of ArizonaSource: Hughes, Dendroclimatology, 2010
    • Tree-ring records in North America circa 1990Source: Meko et al., Journal of Climate, 1991
    • Major regional pa erns recovered from North American tree ringsSource: Meko et al., Journal of Climate, 1991
    • Tree-ring data used to estimate past drought in North America Cook et al., Journal of Quaternary Sciences, 2010
    • One thousand years of drought in western North America Cook et al., Science, 2004
    • alternative
    • ‘Optimal’ reconstruction
    • PACIFICDECADALOSCILLATION
    • Pacific Decadal Oscillation index3210-1-2-3 1900 1920 1940 1960 1980 2000
    • Are these two records more closely tuned to the North Pacific Ocean than other tree-ring data from North America?Source: MacDonald and Case, Geophysical Research Le ers, 2005
    • “ This method of selecting proxies by screening a potentially large number of candidates for positive correlations runs the danger of choosing a proxy by chance. Gerg Bürger Freie Universität-Berlin ”Source: Bürger, Science, 2007
    • Carlo Emilio Bonferroni 1892 - 1960
    • 2 Is there an optimal approach for recovering low-frequency variability from climate-sensitive tree rings?
    • 20-day weather simulation from NASA’s GEOS-5 model
    • DECADALCLIMATE VARIABILITY
    • Benoit Mandelbrot March 2007
    • “ We shall speak of “Joseph-wild” behavior when the we est decade within a century includes an extraordinary “term” of wet years. ”
    • Central Pacific Coast
    • Ault and St. George, Journal of Climate, 2010
    • Ault and St. George, Journal of Climate, 2010
    • “ The decadal time scale offers a critical bridge for informing adaptation strategies as ” climate varies and changes. Meehl et al., BAMS, 2009
    • ~10 yr~100 yr = variability low ‘n’ observations
    • “ ... the use of high-resolution paleoclimate proxy data should be expanded because the short observational record and model uncertainty are unable to simulate [Decadal Climate Variability]... ” Mehta et al. Bulletin of the American Meteorological Society 2011
    • Source: Dan Griffin
    • DIFIEDM O SINGULAR SPECTRUM ANALYSIS
    • x(t) y(t) tEOFsreconstructed sibling components components
    • really not that decadal decadalSource: St. George and Ault, Journal of Geophysical Research - Atmospheres, 2011
    • How well does this approach characterize decadal variability?Ault and St. George, Journal of Climate, 2010
    • 3 Do climate-sensitive trees (and other proxies) transform climate signals in predictable ways?
    • WATERhigh growth reduced cell division flooding reduced cell expansion anoxic conditions C02 starvationlow growth dry wet
    • ∆S
    • “ Discharge or lake records ‘‘have a tendency to exhibit more pronounced and smoother cycles’’ than precipitation because of storage. ” Vit Klemeš
    • Do proxiesPUMP UP low-frequency signals?
    • Source: Jansen Cardy Sarah Truebe University of Arizona
    • Truebe et al., IOP Conference Series : Earth and Environmental Science, 2010
    • WATERhigh growth reduced cell division flooding reduced cell expansion anoxic conditions C02 starvationlow growth dry wet
    • “ [L]inear empirical–statistical analyses alone cannot be used to prove a physical or biological mechanism for variability or ” change in the climate-tree growth relationship. Anchukaitis et al., Geophysical Research Le ers, 2007
    • Even a simple cambial model can reproduce the main features in real tree-ring data from RussiaSource: Evans et al., Journal of Geophysical Research, 2006
    • Pinus spp.Source: Paul Schulte
    • CONTEMPORARY ISSUES IN THE STUDY OF ANCIENT CLIMATESCLIMATE SCIENCE, STATISTICS AND THE COMPUTATIONAL SCIENCES READING GROUP APRIL 2012
    • “ Tree-ring analysis is one of the most powerful tools available for the study of environmental change and the identification of fundamental relationships ” between tree growth and climate. Ed Cook and Neil Pederson Lamont-Doherty Earth Observatory
    • Toby Ault National Corporation for Atmospheric Research