Time-variations of the climate feedback parameter ? are associated with the Pacific Decadal Oscillation
Meyssignac, Benoît ; Chenal, Jonathan ; Loeb, Norman ; Guillaume-Castel, Robin ; Ribes, Aurélien
Climate models suggest that the climate feedback parameter ?, which denotes the magnitude of the Earth radiative response to a change in global surface temperature, varies with time. This is because ? depends on the pattern of sea-surface temperature. However, the time-variability of ? and its relation to the sea-surface temperature pattern has not been evaluated in multi-decadal observations. Here, using up-to-date observations, we evaluate the global energy budget over successive 25-year windows and derive a time-series of ? over 1970-2005. We find ? varied within the range [?3.2, ?1.0]W???m?2???K?1 since 1970. These variations are linked to the sea-surface temperature pattern changes associated with the Pacific Decadal Oscillation. Climate model simulations forced with observations of historical sea-surface temperature show a 1970-2005 mean ? that is consistent with observations. However, they fail in reproducing observed ? time-variations since 1970 which are associated to the Pacific Decadal Oscillation, meaning that climate models underestimate the pattern effect at decadal time scales.</p>
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