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Australia: The Land Where Time Began |
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Global Warming
Hiatus – Distinct Energy Budgets for Anthropogenic and Natural Changes
According to Xie et al. it is
now possible to close (IPCC
climate change, 2013) the energy budget of the Earth for the last 4
decades, and it supports the forcing by anthropogenic greenhouse
emissions as the cause of climate warming. The closure, however, depends
on an unrealistically large increase of aerosol cooling (Murphy, 2013)
during the so-called global warming hiatus since the late 1990s (Murphy
et al., 2009; Church et al., 2014) that was partially due to cooling of
the tropical Pacific Ocean (Meehl et al., 2011; Kosaka & Xie, 2013;
England et al., 2014). Xie et al.
say the assumption is that the same climate feedback applies to
anthropogenic warming as well as natural cooling. In this paper Xie et
al. present the results of
their analysis of climate model simulations with and without increases
of anthropogenic gas concentrations, which show that radiation at the
top of the atmosphere and mean global surface temperature are coupled
much less tightly for natural decadal variability than for response
induced by greenhouse gas, which implies a distinct climate feedback
between anthropogenic warming and natural variability. Also, Xie et
al. identified a difference
in phase between radiation at the top of the atmosphere and global mean
surface temperature such that the uptake of heat by the ocean had a
tendency to slow down during the surface warming hiatus. Xie et
al. found that this result is
broadly consistent with observations, though it deviates from existing
energy theory. Xie et al. say
their study highlights the importance of developing metrics that
distinguish between anthropogenic change and natural variations in order
to attribute climate variability and to estimate climate sensitivity of
climate from observations.
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Author: M.H.Monroe Email: admin@austhrutime.com Sources & Further reading |