Presentation on theme: "Scaling Laws, Scale Invariance, and Climate Prediction"— Presentation transcript:
1 Scaling Laws, Scale Invariance, and Climate Prediction Bill CollinsUC Berkeley and LBLBerkeley, California
2 Topics Application of climate models for mean climate change Application of climate models for climate extremesScaling and convergence of atmospheric dynamical fieldsChanges with resolution in mean and extreme rainfallChanges with resolution in clouds
3 Projection of regional temperatures Roughly 2/3 of warming by 2030 is from historical changes.Warming by 2030 exceeds 20th C natural variability by >2x.IPCC AR4, 2007
4 Climate impacts: precipitation intensity IPCC AR4, 2007Precipitation intensity is annual rainfall divided by the number of wet days.Precipitation intensity increases significantly at higher latitudes by 2100.
5 Climate extremes: 2003 European heat wave August 2003 temperature anomaliesNASAKey vulnerabilities of industry, settlements and society are most often related to:climate phenomena that exceed thresholds for adaptation, related to the rate and magnitude of climate change, particularly extreme weather events and/or abrupt climate changelimited access to resources (financial, human, institutional) to cope, rooted in issues of development contextWikipedia entry on 2003 heat wave
6 An “extreme” is an usual climate state Monthly average August 2003 temperaturesFaq 9.1, WG1, Figure 1IPCC AR4, 2007
7 Increasingly warmer conditions Days/decadeDays/decade–41%+29%DaysDaysAlexander et al, 2006
8 Increase in strong precipitation events Days/decade%/decade+8%Days%Alexander et al, 2006
9 Climate extreme indices for North America Change in index over 21st century for the B1 scenario (550 ppm CO2 at 2100)Stippled regions = all models agree on sign.Change in index over 21st century for the A1B scenario (720 ppm CO2 at 2100)Stippled regions = all models agree on sign.Time series of regionally averagedIndices for the three IPCC emissionsScenarios, averaged across the models.Shaded areas = the inter-model rangeChange in index over 21st century for the A2 scenario (850 ppm CO2 at 2100)Stippled regions = all models agree on sign.
14 Resolution of climate models 1990200119952005Resolution has increased by a factor of 5.Are the model(s) converging with increased resolution?IPCC AR4, 2007
15 Fidelity of atmospheric winds vs. resolution Collins et al, 2006Error in meansError in varianceError in correlationScaled Variance RatioThe resolution of Community Model has increased by a factor of ~6.The fidelity of its simulated winds has improved by a factor of ~20.
16 Spectra of winds over western Pacific Wikle et al, 1999Dynamical improvements are consistent with numerical formulation.Simulated dynamics reproduce observed scaling laws at largest scales.
17 Low confidence in impact on rainfall IPCC AR4, 2007
18 Predictive confidence vs. resolution IPCC AR4, 2007Consistency among simulated rainfall decreases at smaller scales.Internal variability in simulated rainfall increases at smaller scales.
19 Net surface water flux vs. resolution GlobalPacificAtlanticWilliamson et al, 1995Do the time-mean fluxes of water converge with increasing resolution.NO? The time-men fluxes do not converge, and can even change sign.
20 Precipitation extremes vs. resolution Williamson, 2007Do the extreme rainfall rates converge with increasing resolution?NO? The rates do not converge for higher spatio-temporal resolution.
21 Inter-model differences in climate sensitivity Kiehl et al, 2006Does climate sensitivity converge with increasing resolution?NO? The sensitivity and feedbacks do not converge for resolution.
22 Changes in cloud amount vs. resolution Williamson, 2007Do cloud properties and amounts converge with increasing resolution?NO? Cloud amounts show no sign of convergence (in at least 1 model).
23 ConclusionsClimate change prediction will increasingly focus on regional and intermittent phenomena.These predictions require models that converge with increasing spatial and temporal resolution.Simulated dynamics generally converges with resolution.However, simulated hydrological processes do not converge with spatial and temporal resolution.Climate models need physics that obeys the scale invariance of the real atmosphere.