Monday, 8 January 2018: 11:00 AM
616 AB (Hilton) (Austin, Texas)
The global-mean surface temperature has experienced a rapid warming from the 1980s to early-2000s but a nearly stalled warming since, referred to as the global warming hiatus in the literature. An examination of the decadal evolution of the global-mean surface energy budget in the ERA-Interim indicates the increase of carbon dioxide alone yields a nearly steady warming trend from the 1980s to the present, but neither accounts for the rapid warming nor the muted warming periods directly. Our analysis indicates that the fast warming period can be divided into two phases: A first phase caused by enhanced solar absorption due predominantly to a decrease of clouds, followed by a second phase caused by enhanced downward longwave absorption, mainly attributed to greater downward longwave emission due to a warmer atmosphere. The global warming hiatus period that follows is a consequence of the nearly offsetting contributions by the total downward radiative fluxes and non-radiative processes. The total downward radiative effect favors a cooling of the surface due to a decrease of solar absorption caused primarily by cloud increases, while the non-radiative effect favors a warming of the surface due to a decrease of energy flux leaving the surface layer. The non-radiative effect is slightly larger so a weak or muted surface warming is still discernible during the global warming hiatus period.
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