While waiting to get my Insight worked on, I read
"Climate change and
trace gases", a paper authored by Jim Hansen and five other U.S.
climate scientists, published in the Philosophical Transactions of the Royal
Society. It's a pretty technical discussion on the mechanisms that cause
relatively abrupt climate changes, and not on millennial or even century-scales
of time, but decade-scales. It's a pretty sobering read, especially the
summary..
The
gravest threat we foresee starts with surface melt on West Antarctica and
interaction among positive feedbacks leading to catastrophic ice loss. Warming
in West Antarctica in recent decades has been limited by effects of stratospheric
ozone depletion (Shindell & Schmidt 2004). However, climate projections
(Hansen et al. 2006b) find surface warming in West Antarctica and warming of
nearby ocean at depths that may attack buttressing ice shelves. Loss of ice
shelves allows more rapid discharge from ice streams, in turn a lowering and
warming of the ice sheet surface, and increased surface melt. Rising sea level
helps unhinge the ice from pinning points.
The paper takes issue with the IPCC's projections,
which it says, "foresees little or no contribution to twenty-first century
sea-level rise from Greenland and Antarctica."
However,
the IPCC analyses and projections do not well account for the nonlinear physics
of wet ice sheet disintegration, ice streams and eroding ice shelves, nor are
they consistent with the palaeoclimate evidence we have presented for the
absence of discernable lag between ice sheet forcing and sea-level rise.
Translation? The UN's Intergovernmental Panel on
Climate Change, may have got it wrong, underestimating the impact of positive
feedback loops that accelerate the melting of polar ice sheets and glaciers. In
fact, the IPCC's latest report does acknowledge that it has not accounted for
the effects of such melting in its projections largely because it didn't have
enough data.
The bottom line is, we need to immediately and aggressively implement a
concerted effort to reduce greenhouse gas emissions and finding a way to pull
the carbon we've already put into the atmosphere back out of it and sequester
it deep below the ocean floor. The paper concludes by saying because of the
extreme sensitivity of the climate to forcing, even the relatively small amount
of CO2 mankind has injected into the atmosphere by our burning of fossil fuels,
is more than enough to cause the climate to flip into a very dangerous,
unstable and uncontrollable cycle of warming, accompanied by catastrophic rises
in sea level.
Present
knowledge does not permit accurate specification of the dangerous level of
human-made GHGs. However, it is much lower than has commonly been assumed. If
we have not already passed the dangerous level, the energy infrastructure in
place ensures that we will pass it within several decades.
Bill
Moore, Editor-in-Chief of EVWorld.Com
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