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
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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