Thursday, April 12, 2007
Are we underestimating the pace of climate change?
Since the last assessment report from the Intergovernmental Panel on Climate Change (IPCC '01), more recent models and measurements have led many climate scientists to the conclusion that the coming climate disruption will be greater and come faster than was the consensus even five years ago. Some recent estimates of the climate sensitivity are nearer the high end of the canonical range (1.5-4.5°C) for the equilibrium temperature response to doubled CO2 . The probable sea-level rise reported in the recent IPCC (WG I) '07 may well be far too optimistic.
Recent observations are disturbing: accelerating positive feedbacks from the terrestrial biosphere (increasing forest fires globally, rapid melting of boreal permafrost), positive ice-albedo feedback of rapidly retreating Arctic sea-ice and northern snowfields and glaciers, changes in the mid-to-high latitude atmospheric circulation, completely unpredicted and rapidly accelerating melt-water losses from both Greenland and Antarctica icecaps, the intensification of tropical cyclones in the North Atlantic, increasingly severe weather and flood/drought anomalies globally, and the documented acidification of the global ocean.
As the movement of polar ice-sheets now exceeds the present pace of the international policy responses, prominent scientists have begun to seriously consider (and reconsider) possible geo-engineering 'fixes' to address both the long-wavelength and the short-wavelength ends of the planetary radiative imbalance (carbon sequestration, stratospheric aerosol injection, a sun shade at L1?).
We will have to learn how to manage the unavoidable and try harder to avoid the unmanageable.
Richard Gammon is a Professor at the UW School of Oceanography and Department of Chemistry, and Adjunct Professor in the Department of Atmospheric Sciences.