Using the climate of the past to predict the climate of the future

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Using the climate of the past to predict the climate of the future. Danny McCarroll Swansea. ‘ Millennium ’. European climate of the last millennium. EU 6 th Framework Integrated Project. 41 partners. January 2006 – Dec 2010. Why were we funded?. Reconstruct past climate - PowerPoint PPT Presentation

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  • Using the climate of the past to predict the climate of the futureDanny McCarrollSwansea

  • MillenniumEuropean climate of the last millenniumEU 6th Framework Integrated Project41 partnersJanuary 2006 Dec 2010

  • Why were we funded?Reconstruct past climateImprove predictions of future climate change

  • Climate Sensitivitychange in global mean equilibrium temperature after a doubling of atmospheric carbon dioxide1970s: 1.5 to 4.5C

    IPCC 2007:2.0 to 4.5C

    values substantially higher than 4.5C still cannot be excluded

  • Likely range of mean global temperature increase by the end of the 21st CenturyA1B:1.7C to 4.4CA2:2.0C to 5.4CTemperature increases over land are likely to be roughly twice the global average and even larger in the north.

  • Change in temperature after CO2 doubling. Black lines: 2579 runs. Red lines:127 30-year Hadley Centre simulationsClimateprediction.netEnsembles of model runs predict many possible futures: which are most likely?Note the uncertaintyIs not symmetrical

  • Hiro Yamazaki, Chris Huntingford, Myles Allen, Dave FrameSimple one-box energy balance model to demonstrate the methodology

    model-data mismatch in temp. likelihood of the choice of calibration scaling coefficientmodel-data mismatch for the effective heat capacity of ocean in the instrumental period.The overall likelihood of each model run is multiplication of:Millennium will use a GCM, incorporating the geography of climate changes, and better uncertainty estimates for the palaeoclimate reconstructions

    (Distributed via palaeoclimateconstraintWith palaeoclimateconstraint3 x CO2 stabilization scenario(similar to A1B until 2100)

  • Millennium test setWe do not need to fill every grid square

    Different squares can contain different climate data

    One square can contain several different climate variables

    No need to average over time or space

  • Winter temperature based on documentary evidence for dates of first and last ship to use Stockholm harbourLotta Leijonhufvud, Rob Wilson, Anders Moberg The Holocene 2008, 18, 331-341

  • Extended back to AD 1500Millennium special issue of Climatic Change

  • Documentary evidence (DE) DE sources interpreted to ordinal scale indices Indices express the temperature extremity of a given month (from -3 extremely cold to +3 extremely warm) National T index series: Germany (1500 1759) Switzerland (1500 1816) Czech Republic (1500 1854) Poland (1500 1700) Hungary (1500 1869) Low Countries (1500 2000) CEU T index series1500 - 1854used for cross- checking

  • Method of reconstructionCalibration 1771 - 1816 Verification I. 1817 - 1854Verification II. 1760 - 1770Calibration 1771 - 1816 Linear regression model

  • CEU temperature reconstructions

  • Central Europe monthly, seasonal and annual temperaturesDobrovoln P, Moberg A, Brzdil R, Pfister C, Glaser R, Wilson R, van Engelen A, Limanwka D, Kiss A, Halkov M, Mackov J, Riemann D, Luterbacher J, Bhm R (2009) Monthly and seasonal temperature reconstructions for Central Europe derived from documentary evidence and instrumental records since AD 1500

  • Northern tree line summer temperatures from tree rings: dominated by Volcanic forcing Sulphate loadings NH after Gao, and solar minima in green

  • Perturbed physics spin-up experiment. >25,000 variants of FAMOUS

  • Five solar forcing scenarios

  • Four volcanic forcing scenarios

  • 148 model variants (perturbed physics)18 forcing combinations(Same aerosol and greenhouse gas forcing)

    Simulations AD800 to AD 2200Distributed in 200-year long work units

    SRES A1B scenario until 2100 AD and held constant thereafter.

    (They are not all ready yet, and lots of gaps!)The Millennium experiment

  • 20,000 to 30,000 FAMOUS model simulations have been running simultaneously on volunteers computers

  • Web-interface of the system

  • 1 North Atlantic, May-Oct, AD 1000-2000, marine proxies2 Northern Fennoscandia, Jun-Aug, AD 1000-2004, tree-ring proxies3 Alpine region, Jun-Aug, AD 1053-2007, tree-ring and lake proxies4 Pyrenees, May-Sep, AD 1260-2005, tree-ring proxies5 Northern Fennoscandia, Apr-May, AD 1693-2010, river ice break records6 Southeastern Sweden, Jan-Apr, AD 1502-2008, harbour freezing records7 Central Europe, Dec-Feb, AD 1500-2007, documentary and early instrumental 8 Western Europe, Dec-Feb, AD 1659-2010, instrumental observations9 Northern Italy, Dec-Feb, AD 1789-2007, instrumental observations

    We have a lot more!Selected reconstructions

  • Selected reconstructions

  • Model ranking procedureD2 = quadratic distance valueD2 value is computed for each of the nine proxy sitesD2 value computed using unforced simulationsT-value tests null hypothesis forced = unforcedLocal T-values summed and normalized

    Used 30-year non-overlapping averages (33 points)Ranks plotted using colours, red (best 10) to blue.

    This is a first attempt using incomplete data- suggestions welcome!Hiro Yamazaki, Anders Moberg, Alistair Hind, Rolf Sundberg

  • Preliminary results

  • ConcernsModel data still very incomplete200-yr work units limit scope for internal variability30-yr average may be too large for volcanic forcingShould ranking exclude the Greenhouse period? Uncertainty in proxy reconstructions not yet includedEurope may be too small (internal > forced?)

    All suggestions warmly welcomed

  • ConclusionsMethod looks promising (but needs to be refined)Likely range of future temperatures is constrainedVery high sensitivity models score poorly (good news)

    Bad news: All reasonable models under A1B predict >2 degrees C rise by 2100 for mean annual T of Europe

    *created by perturbing 14 uncertain atmospheric and oceanic parameters, and executed under constant volcanic andsolar forcing scenarios for 200 years by internet volunteers. Models with little oceanictemperature drift in the second 100 years are selected and used for transient forcing experiments.

    *Figure 1: Locations ofthe regional temperaturereconstructions and theircounterparts in theFAMOUS model grid.Red /blue boxes identifywarm/cold seasons. Therespective season andfirst year of each proxyrecord is indicatedwithin each box.*Figure 4: Simulated averaged European annual-mean temperature change from the period1970-1999 to 2070-2099 for the 627 of the simulations used in Figures 2-3 that also havecomplete data in the 2070-2099 period. Ranking based on full proxy period (top) andinstrumental-only period (bottom). Horizontal axis holds the temperature change, while thevertical axis holds the normalized T-statistic (note increasing negative values upwards). AllT-values larger than zero have been set to zero. Dashed vertical lines denote the range of thedark-red coloured best-ranked (~3%) simulations. Dashed horizontal line denote the 1%level for rejecting the null hypothesis that a forced simulation is equivalent with an unforcedone.*


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