Why geologists and supercomputers need each other more than ever

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Why geologists and supercomputers need each other more than ever

High-resolution paleoclimate data:challenges and opportunitiesKim M. CobbGeorgia Tech


The**“Beer**Test”*


Tropical Pacific sea-surface temperaturesdrive climate variability in many regions of the worldEl Niño TemperatureEl Niño-Southern Oscillation(ENSO)“Pacific Decadal Oscillation”(Mantua et al., 1997)El Niño Precipitationand“North Pacific Gyre Oscillation”(Di Lorenzo et al., 2010)on decadal to interdecadaltimescalesDai and Wigley, 2000


Uncertainties in Tropical Pacific climate projectionsVariabilitynot sensitiveto forcing?Can we testthis in thereal world?IPCC AR4Consensus in model SST trendsmust be validated with data


Sparse data# monthly SST observations in central tropical Pacificover last 150 years18 19 20Bunge & Clarke, 2009


Leads to significant uncertainties in tropical Pacificinstrumental temperaturesSST trends overlast century intwo globalSST productsVecchi et al., 2008


Uncertainties largest on lower frequencies32NINO34 in 3 historical SST analysesNINO34 ( ° C)10-1-2-311850 1900 1950 2000Timeidem, 10-year lowpass filterEmile-Geay et al., submittedNINO34 ( ° C)0.50-0.5ERSSTv3, 0.44 ° C/century-1HadSST2i, 0.38 ° C/centuryKaplan, 0.18 ° C/century-1.51850 1900 1950 2000Time


Paleoclimate data to the rescue!24.324.8- monthly- to annually-resolved- continuous for decades to centuries- distributed in space ! networksEssential for:ini:al*value*31.932.41. quantifying natural variability (detection uncertainty* 33.0and attribution)2. probing relationship between forcing and response3. assessing accuracy of model dec-cen model* variabilityuncertainty*4. regional decadal-scale predictionHawkins & Sutton, 2009forcing*uncertainty*33.737.638.239.639.6FIG. 4. The relative importance of each source of uncertainty in decadal mean surface temperature projectionsis shown by the fractional uncertainty (the 90% confidence level divided by the mean prediction) for (a)the global mean, relative to the warming from the 1971–2000 mean, and (b) the British Isles mean, relative to


Paleoclimate data to the rescue!sort of…24.324.8Sources of uncertainty in proxy records:- age models (absolute vs. relative)- non-stationary and/or frequency-dependentclimate relationships- indicator is a complex function of climate-related32.4variables (e.g. oxygen isotopes)33.0- possible seasonal bias- instrument error- errors correlated to climate (pesky biology)- progressive yet heterogeneous introduction ofartifacts into older samples31.933.737.638.239.639.6


Paleoclimate data to the rescue!sort of…24.324.8Sources of uncertainty in proxy records:- age models (absolute vs. relative)- non-stationary and/or frequency-dependentclimate relationships31.9- indicator is a complex function of climate-related32.4variables (e.g. oxygen isotopes)- possible seasonal bias33.0- instrument error- errors correlated to climate (pesky biology)- progressive yet heterogeneous introduction ofartifacts into older sampless:ll*struggling*migh:ly*33.737.638.239.639.6we*have*robust*es:mate*


A*coral*example*from*the*tropical*Pacific**Records*of*past******and*** * *present** * *climate*


CORALS from the tropical Pacificrecord El Niños in the geochemistryof their skeletonscoral*δ 18 O=*a 1 SST+*a 2 δ 18 O sw +*error**where:*δ 18 O sw* α*SSS*


NINO3.4 SST (°C)a “Mickey Mouse” techniqueto compare coral to regional SST


***take*the*reconstruc:on*as*far*back*as*it’ll*go*warmer,wettercooler,drierCobb et al., 2003; in prep&&&and&then&it&gets&interes*ng&


Figure 2: Proxy database: spatio-temporal characteristics. (top) location of proxy archives. (bottom)temporal distribution of proxies. The NINO3.4 region is indicated by the black box.**aQempt*a*“mul:Rproxy”*reconstruc:on*a) Proxy Network for NINO34 reconstruction (57 records)80 o N60 o N40 o N0 o 20 o N20 o S40 o S60 o S80 o SEmile-Geay et al., submitted0 o60 o E120 o E180 o W120 o W60 o W60b) Proxy availability# proxies50403020CoralIce coreTreeSedimentSpeleothem1001000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000Time


Effect of coral detrending (20-year lowpass)+1 13*different*instrumental*targets*=*3*different*reconstruc:ons**NINO3.4 NINO34 SST Anomaly (°C)0.50-0.5-1but*there*are*common*elements…*-1.5Emile-Geay et al., submittedERSSTv3, TTLSERSSTv3, TTLS, detrended coralsHadSST2i, TTLSHadSST2i, TTLS, detrended coralsKaplan, TTLSKaplan, TTLS, detrended corals1000AD 1500AD 2000AD1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000TimeFigure 10: Influence of coral detrending. Solid lines depicts reconstructions made from nondetrendedcorals, dashed lines with coral records detrended using a 150-year spline fit (subscript


and*we*can*do*much*beQer*with*El*Nino*reconstruc:on*Coral 18 O network, 22 sites, EOF 1 - 18% variance24 o N16 o N8 o N0 o8 o S16 o S24 o SEOF > 0, size magnitudeEOF < 0, size magnitudeEmile-Geay et al., in progress-1 -0.5 0 0.5 1Contours: SST ( ° C) regressed onto PC 1nitless)0.150.10.050Principal component timeseriesrequency10 0 PC 1 MTM spectrum5020 10 6 421


assess*uncertain:es*of*reconstruc:on*by*building*a*“pseudoproxy”*network*from*climate*model*output*1a) NINO34 CCSM4 LM pseudoproxy validation, sparse network, RegEM ttls0.50NINO34 (C)-0.5-1-1.5-2Emile-Geay et al., submittedTarget NINO34SNR = , RE= +0.35; +0.74SNR = 1.0, RE= +0.37; +0.75SNR = 0.5, RE= -0.46; +0.66SNR = 0.25, RE= -0.96; +0.341000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000Time (years A.D.)Proportion10.90.80.70.60.50.4b) RE scores, 200-member ensembleSNR = SNR = 1.0SNR = 0.5SNR = 0.25AR(2) benchmarkProportion10.90.80.70.60.50.4c) Same (low-frequency)


NH*temperature*reconstruc:ons*have*a*long*and*storied*history***InstrumentaltemperatureTemperature Difference (°C)


20.421.6instrumental&climate&data&24.324.831.932.433.033.7a)individual* b)paleoclimate*records*c)APROXY&&&CLIMATE&MODEL&DATA&EVALUATION&grow*synthe:c*proxies**43.0+/B&climate&&45.2forcing&45.8histories&50.8*simulate)*past))*climate)*)53.054.557.5+/B&isotopes&58.659.361.7


Coral vs Pseudocoralestimates of 20 th century changes inmean state and ENSO-related varianceThompson&et&al.,&2011;&in&prep&CMIP-3CMIP-5


A*good*ques:on*for*Big*Data:**How*has*(tropical*Pacific)*climate*varied**in*the*past*(century?*millennium?...)**and*what*does*that*mean*for*climate**(precipita:on)*forecasts*on*regional,**decadal*scales?*


1JULY 2011 N U R H A T I E T A L .Quantifying 20 th century SST and δ 18 O sw trendsFIG. 4. Palmyra coral monthly resolved d 18 O, Sr/Ca-derived SST,and d 18 O SW records from 1886 to 1998. (a) Palmyra coral d 18 Orecord (Cobb et al. 2001), (b) Sr/Ca-derived SST (black) plottedwith ERSST (gray; Smith et al. 2008), and (c) d 18 O SW -based salinityrecord.high correlations for interannual (R 5 0.72 for 2–7-yrbandpassed) and decadal-scale (R 5 0.61 for 8-yr lowpassed)versions of the records.The Palmyra coral d 18 O SW record is dominated byModern coral contains SST trend similar to instrumental record;Reveals large negative δ 18 O sw trend ! anthropogenic fresheningFIG. 4. Palmyra coral monthly resolved d 18 O, Sr/Ca-derived SST,and decadal-scale d 18 O SW records variability from 1886 andtoa1998. relatively (a) Palmyra largecoral fresheningtrend (Cobb over et al. the 2001), late(b) twentieth Sr/Ca-derived century SST (black) (Fig. 4c). plotted Ad 18 Orecordwith visual ERSST comparison (gray; Smith of et the al. 2008), threeand coral (c) drecords 18 O SW -based plotted salinityrecord.18FIG. 5. Interannuvariability at Palmclimate indices: (a)NurhatiSST anomalieset al.,(bla2011terannual (2–7-yr(black) and the 23scale Sr/Ca-derived(gray) plotted as 5-derived SST (blacrunning averages.a 95% confidenceserial FIG. autocorrelati 5. Interannuvariability at Palm


1JULY 2011 N U R H A T I E T A L .Quantifying 20 th century SST and δ 18 O sw trendsNurhati et al.,2011FIG. 4. Palmyra coral monthly resolved d 18 O, Sr/Ca-derived SST,-and d 18 new coral Sr/Ca record highly correlated with SST,O SW records from 1886 to 1998. (a) Palmyra coral d 18 Oshows +0.53 ± 0.1 °C warming over 20record (Cobb et al. 2001), (b) Sr/Ca-derived SST th century(black) plottedwith ERSST (gray; Smith et al. 2008), and (c) d 18 O SW -based salinityrecord.Modern coral contains SST trend similar to instrumental record;Reveals large negative δ 18 O sw trend ! anthropogenic fresheningFIG. 4. Palmyra coral monthly resolved d 18 O, Sr/Ca-derived SST,and d 18 O SW records from 1886 to 1998. (a) Palmyra coral d 18 Orecordhigh correlations(Cobb et al. 2001),for interannual(b) Sr/Ca-derived(R 5SST 0.72(black)for 2–7-yrplottedwith bandpassed) ERSST (gray; andSmith decadal-scale et al. 2008), and (R(c) 5d0.61 18 O SWfor -based 8-yr salinity low-record.passed) versions of the records.FIG. 5. Interannuvariability at Palmclimate indices: (a)SST anomalies (blaterannual (2–7-yr(black)FIG. 5.andInterannuthe 23scalevariabilitySr/Ca-derivedat Palm


VEMBER 2006 H E L D A N D S O D E N 56951JULY 2011 N U R H A T I E T A L .20 th century Sr/Ca and δ 18 O sw record from PalmyraHeld & Soden, 2006Nurhati et al.,2011FIG. 4. Palmyra coral monthly resolved d 18 O, Sr/Ca-derived SST,and d 18 O SW records from 1886 to 1998. (a) Palmyra coral d 18 Orecord (Cobb et al. 2001), (b) Sr/Ca-derived SST (black) plottedwith ERSST (gray; Smith et al. 2008), and (c) d 18 O SW -based salinityrecord.Resolves large negative δ 18 O sw trend ! anthropogenic fresheningConsistent with model response to CO 2 forcingFIG. 5. Interannuvariability at Palm


FIG. 4. The relative importance of each source of uncertainty in decadal mean surface temperature projectionsis shown by the fractional uncertainty (the 90% confidence level divided by the mean prediction) for (a)the global mean, relative to the warming from the 1971–2000 mean, and (b) the British Isles mean, relative tothe warming from the 1971–2000 mean. The importance of model uncertainty is clearly visible for all policyrelevanttimescales. Internal variability grows in importance for the smaller region. Scenario uncertaintyonly becomes important at multidecadal lead times. The dashed lines in (a) indicate reductions in internalvariability, and hence total uncertainty, that may be possible through proper initialization of the predictionsthrough assimilation of ocean observations (Smith et al. 2007). The fraction of total variance in decadal meansurface air temperature predictions explained by the three components of total uncertainty is shown for (c) aglobal mean and (d) a British Isles mean. Green regions represent scenario uncertainty, blue regions representmodel uncertainty, and orange regions represent the internal variability component. As the size of the regionis reduced, the relative importance of internal variability increases.AMERICAN METEOROLOGICAL SOCIETY AUGUST 2009 |1097

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