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Stochastic and scaling climate sensitivities: Solar, volcanic and orbital forcings
Author(s) -
Lovejoy S.,
Schertzer D.
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2012gl051871
Subject(s) - climatology , scaling , volcano , climate change , forcing (mathematics) , sensitivity (control systems) , environmental science , climate model , gcm transcription factors , range (aeronautics) , statistical physics , meteorology , atmospheric sciences , general circulation model , geology , mathematics , physics , oceanography , geometry , seismology , materials science , electronic engineering , engineering , composite material
Climate sensitivity ( λ ) 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 λ 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 λ is roughly a scaling function of resolution Δ t : λ ≈ with exponent 0 ≈ < H λ ≈ < 0.7. Since most have H λ > 0, the implied feedbacks must generally increase with scale and this may be difficult to achieve with existing GCM's.