Climate Response Across Time Scales as Inferred From the Proxy Record

Transcription

1 Climate Response Across Time Scales as Inferred From the Proxy Record Cristian Proistosescu Peter Huybers Harvard University Advanced Climate Dynamics Course Laugarvatn, Iceland Aug 24, 2015 Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

2 Motivation 1976 An understanding of the origin of climatic variability, in the entire spectral range from extreme ice age changes to seasonal anomalies, is a primary goal of climate research. Yet [...] there exists today no generally accepted, simple explanation for the observed structure of climate variance spectra. A persistent difficulty with these investigations is that the postulated input response relationships, if they exist, are not sufficiently pronounced to be immediately obvious on inspection of the appropriate time series (Hasselman 1976) 2015 Input-response relationships can be illuminated by using presently available instrumental and proxy records Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

3 Climate Variance Spectra Spectral Energy Density [ C 2 /ds] Mg/Ca 10 2 U37 K δo 18 Calcite 10 0 Faunal Counts Sr/Ca CRU Frequency [1/year] Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

4 Forcing Variance Spectra Spectral Energy Density [(W/m 2 ) 2 /ds] CO 2 - Epica Volcanic Solar 10 8 NCEP mean Cumulative Frequency [1/year] Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

5 Input Response Relations - Linear Feedback System Transfer Function Gain Ĥ(f ) F (f ) = T (f ) Time Scale Dependent Climate Sensitivity ( ) [ 1 C ] Ĥ τ W m 2 Spectral Energy Density [( C/ 2 /ds] Heat Flux Temperature Frequency [1/year] Spectral Energy Density [(W/m 2 ) 2 /ds] Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

6 Empirical Gain Estimate Gain Ĥ(f ) F (f ) = T (f ) 2.5 Empirical Gain IPCC Likely Range Frequency [cycles/year] Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

7 Hasselman Model - Surface Ocean Mixed Layer:C Heat Flux Forcing:F Feedbacks: λ Fast, Net Negative e.g. Plank,Clouds, Albedo, etc. 2.5 Empirical Gain IPCC Likely Range Hasselman (1 Ocean Box) C dt dt = λt + F Frequency [cycles/year] Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

8 Surface + Deep Ocean Mixed Layer:C Heat Flux Forcing:F Feedbacks: λ Fast, Net Negative e.g. Plank,Clouds, Albedo, etc. Diffusive Deep Ocean: χ 2.5 Empirical Gain IPCC Likely Range Hasselman (1 Ocean Box) 2 2 Ocean Boxes Frequency [cycles/year] Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

9 Surface, Deep Ocean, Slow Feedbacks Mixed Layer:C Heat Flux Forcing:F Feedbacks: λ Fast, Net Negative e.g. Plank,Clouds, Albedo, etc. Diffusive Deep Ocean: χ Slow Feedbacks: λ s, τ 2.5 Empirical Gain IPCC Likely Range Hasselman (1 Ocean Box) 2 2 Ocean Boxes 2 Ocean + Slow Feedbacks Frequency [cycles/year] Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

10 Gain to CO 2 - Background Continuum PSD [ C 2 /ds] 10 0 Temperature EPICA GHG Forcing Frequency [1/kyr] 12 Dome C Calibration 10 Glacial Bands Frequency (1/kyr) Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

11 Gain to CO 2 - Background Continuum vs Glacial PSD [ C 2 /ds] 10 0 Temperature EPICA GHG Forcing Frequency [1/kyr] 12 Dome C Calibration 10 Glacial Bands Frequency (1/kyr) Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

12 Conclusions I Palaeoclimate and instrumental data permits for estimating time-scale dependent climate sensitivity Consistent with Hasselman s paradigm after including terms for diffusivity of heat and variation of ice volume. Weather Forced vs Climate Forced Regimes. Hope for Palaeoclimate. Spectral gap at centennial time-scales, of societal interest. Spectral Energy Density [( C/ 2 /ds] Heat Flux Temperature Frequency [1/year] 2.5 Empirical Gain IPCC Likely Range Hasselman (1 Ocean Box) 2 2 Ocean Boxes 2 Ocean + Slow Feedbacks Spectral Energy Density [(W/m 2 ) 2 /ds] Frequency [cycles/year] Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

13 Conclusions II Gain in 1/100 kyr band is consistent with that estimated at higher frequencies from the background variability (a) a common set of mechanisms (b) consistent with CO 2 driving the 100kyr cycle. PSD [ C 2 /ds] 10 0 Temperature EPICA GHG Forcing 12 Dome C Calibration 10 Glacial Bands Frequency [1/kyr] Frequency (1/kyr) Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

14 Supplemental Slide: Hasselman s Foresight Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1

15 Supplemental Slide: Model Formulation C dt dt = λt + κ zt d λ s α + F T d t =χ 2 T d z 2 τ dα dt = α + α T T 2.5 Empirical Gain IPCC Likely Range Hasselman (1 Ocean Box) 2 2 Ocean Boxes 2 Ocean + Slow Feedbacks Frequency [cycles/year] Cristian Proistosescu Peter Huybers Sensitivity Time Scales Aug 24, / 1