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Alan Robock Department of Environmental Sciences Rutgers University, New Brunswick, New Jersey USA

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Presentation on theme: "Alan Robock Department of Environmental Sciences Rutgers University, New Brunswick, New Jersey USA"— Presentation transcript:

1 Alan Robock Department of Environmental Sciences Rutgers University, New Brunswick, New Jersey USA Climate Dynamics 11:670:461 Lecture 13, 10/23/14

2 Alan Robock Department of Environmental Sciences

3 Alan Robock Department of Environmental Sciences

4 Alan Robock Department of Environmental Sciences

5 Alan Robock Department of Environmental Sciences

6 Alan Robock Department of Environmental Sciences From IPCC AR4 Technical Summary 400

7 Alan Robock Department of Environmental Sciences Box 8.1: Definition of Radiative Forcing (RF) and Effective Radiative Forcing (ERF) The two most commonly used measures of radiative forcing in this chapter are the radiative forcing (RF) and the effective radiative forcing (ERF). RF is defined, as it was in AR4, as the change in net downward radiative flux at the tropopause after allowing for stratospheric temperatures to readjust to radiative equilibrium, while holding surface and tropospheric temperatures and state variables such as water vapor and cloud cover fixed at the unperturbed values. Chapter 8, AR5, WG1

8 Alan Robock Department of Environmental Sciences Box 8.1: Definition of Radiative Forcing (RF) and Effective Radiative Forcing (ERF) (continued) ERF is the change in net top-of-the-atmosphere downward radiative flux after allowing for atmospheric temperatures, water vapour, and clouds to adjust, but with surface temperature or a portion of surface conditions unchanged. While there are multiple methods to calculate ERF, we take ERF to mean the method in which sea surface temperatures and sea ice cover are fixed at climatological values unless otherwise specified. Land-surface properties (temperature, snow and ice cover and vegetation) are allowed to adjust in this method. Hence ERF includes both the effects of the forcing agent itself and the rapid adjustments to that agent (as does RF, though stratospheric temperature is the only adjustment for the latter). Chapter 8, AR5, WG1

9 Alan Robock Department of Environmental Sciences Different calculations of radiative forcing, Fig. 8.1 IRF = Instantaneous radiative forcing, ERF = Effective Chapter 8, AR5, WG1

10 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

11 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

12 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

13 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

14 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

15 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1 Figure 8.9: Change in TOA SW flux [W m –2 ] following the change in albedo as a result of anthropogenic Land Use Change for three periods (1750, 1900 and 1992 from top to bottom). By definition, the RF is with respect to 1750, but some anthropogenic changes had already occurred in The lower right inset shows the globally averaged impact of the surface albedo change to the TOA SW flux (left scale) as well as the corresponding RF (right scale) after normalization to the 1750 value. Based on simulations by Pongratz et al. (2009).

16 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

17 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

18 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

19 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

20 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1

21 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1 Figure 8.17: RF bar chart for the period 1750–2011 based on emitted compounds (gases, aerosols or aerosol precursors) or other changes.

22 Alan Robock Department of Environmental Sciences Chapter 8, AR5, WG1 Figure 8.18: Time evolution of forcing for anthropogenic and natural forcing mechanisms. Bars with the forcing and uncertainty ranges (5–95% confidence range) at present are given in the right part of the figure. For aerosol the ERF due to aerosol-radiation interaction and total aerosol ERF are shown.

23 Alan Robock Department of Environmental Sciences Temperature Feedbacks External forcing + + – – – + Start with temperature increase, e.g., from more CO 2 – – + Robock, Alan, 1985: An updated climate feedback diagram. Bull. Amer. Met. Soc., 66,

24 Alan Robock Department of Environmental Sciences Poisson d’Avril = April Fool Of course! This is the best thing since sliced ​​ baguettes!


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