Stochastic and scaling climate sensitivities: Solar, volcanic and orbital forcings

[1] Climate sensitivity (l) is usually defined as a deterministic quantity relating climate forcings and responses. While this may be appropriate for evaluating the outputs of (deterministic) GCM’s it is problematic for estimating sensitivities from empirical data. We introduce a stochastic definition where it is only a statistical link between the forcing and response, an upper bound on the deterministic sensitivities. Over the range ≈30 yrs to 100 kyrs we estimate this l using temperature data from instruments, reanalyses, multiproxies and paleo spources; the forcings include several solar, volcanic and orbital series. With the exception of the latter we find that l is roughly a scaling function of resolution Dt: l ≈ Dtl, with exponent 0 ≈ < Hl ≈ < 0.7. Since most have Hl > 0, the implied feedbacks must generally increase with scale and this may be difficult to achieve with existing GCM’s. Citation: Lovejoy, S., and D. Schertzer (2012), Stochastic and scaling climate sensitivities: Solar, volcanic and orbital forcings, Geophys. Res. Lett., 39, L11702, doi:10.1029/ 2012GL051871.