Norwegian climsenssummarydotearth

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  • 1. CLIMSENS: Constraining totalfeedback of the climate systemby observations and models.Ragnhild Bieltvedt SkeieTerje Berntsen CICERO and University of OsloGunnar Myhre CICEROMagne Aldrin Norwegian Computer CenterMarit Holden Norwegian Computer Center
  • 2. Climate sensitivity:The equilibrium change in the annual mean global surfacetemperature following a doubling of the atmospheric CO2concentration. IPCC 2007 2
  • 3. Constraining the climatesensitivity• “Bottom-up” approach. Perturbing the representations of the climate feedbacks in GCM models.• “Observational based” approach. Using historical observations and simple climate models 3
  • 4. ΔQ = ΔF - λ ΔTΔQ: Heat flux in the systemΔF: Radiative forcingλ: Climate Feedback ParameterAt equilibrium: ΔQ = 0, λ = ΔF2xCO2 / ΔT2xCO2eq 4
  • 5. Detailed RF calculations:Tropospheric ozone and aerosols ΔF Emissions Oslo CTM2 model RF-calculations IPCC 2007 5
  • 6. A simple climate model:Energy balance model/Upwelling Diffusion Ocean ΔQ Structure of the model Parametre: Name Unit Value Mixed layer depth m 60 2 Vertical heat diffusivity cm /sec 0.634 Polar parameter - 0.4 Vertical velocity, upwelling rate m/yr 4.0 2 Air-sea heat exchange parameter W/(m K) 16.0 2 Oceanic interhemispheric heat exchange coeff. W/(m K) 3.5 2 Atmospheric interhemispheric heat exchange coeff. W/(m K) 0.0 2 Climate sensitivity K/(Wm ) 0.8 Schlesinger et al. (1992) 6
  • 7. Observations• Surface temperature ΔT• Ocean heat content Levitus, GRL 2009 IPCC 2007 7
  • 8. Statistical model:The data:Surface temperature (3 data set, NH and SH averages).Ocean heat content Additative bias/correction for baseline SOI index, Account for El Nino. 8
  • 9. Statistical modelBayesian approach and a MCMC-algorithm:1. Apriori distributions for parameters and input data.2. Update your model with observations.3. Get posteriori uncertainties for your model parametersand input data. One of them is the climate sensitivity! 9
  • 10. λIPCC 2007 10
  • 11. What’s new?• Improved representation of the radiative forcing history• Longer time period with observations 11