Earth's Energy Imbalance and Implications

Authors: James Hansen (1), Makiko Sato (1), Pushker Kharecha (1),
Karina von Schuckmann (2)

(1) NASA Goddard Institute for Space Studies and Columbia University
Earth Institute,
(2) Centre National de la Recherche Scientifique)

http://arxiv.org/abs/1105.1140

Abstract:

Improving observations of ocean heat content show that Earth is
absorbing more energy from the sun than it is radiating to space as
heat, even during the recent solar minimum. The inferred planetary
energy imbalance, 0.59 +/- 0.15 W/m^2 during the 6-year period
2005-2010, confirms the dominant role of the human-made greenhouse
effect in driving global climate change. Observed surface temperature
change and ocean heat gain together constrain the net climate forcing
and ocean mixing rates. We conclude that most climate models mix heat
too efficiently into the deep ocean and as a result underestimate the
negative forcing by human-made aerosols. Aerosol climate forcing today
is inferred to be 1.6 +/- 0.3 W/m^2, implying substantial aerosol
indirect climate forcing via cloud changes. Continued failure to
quantify the specific origins of this large forcing is untenable, as
knowledge of changing aerosol effects is needed to understand future
climate change. We conclude that recent slowdown of ocean heat uptake
was caused by a delayed rebound effect from Mount Pinatubo aerosols
and a deep prolonged solar minimum. Observed sea level rise during the
Argo float era is readily accounted for by ice melt and ocean thermal
expansion, but the ascendency of ice melt leads us to anticipate
acceleration of the rate of sea level rise this decade.