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Workshop 5
“Anthropogenic Climate Destabilization: A Worst-case Scenario”
Participant Statement
September 12–14, 2008 | Bellevue, Washington
David Archer
What are the three critical questions you would ask pertaining to “anthropogenic climate change: a worst-case scenario” – and why?
1. How fast can ice sheets respond to changing climate? Heinrich events and the meltwater pulse 1A during the last deglaciation suggest that it could be centuries, in which case the amount of sea-level rise we could expect by looking at the paleo-record is in the neighborhood of 5 to 20 meters per degree C of temperature change. This is ultimately what we expect, given the long atmospheric lifetime of CO2, but the question is: How quickly will this happen?
2. How much soil carbon will be lost to CO2 in the atmosphere in a warming climate? Most of the high-carbon soils on Earth today are in the high latitudes. Ocean carbon-cycle feedbacks, not well understood, played a huge role in amplifying the climate forcing from the orbital variations of the Earth around the Sun. Will this happen again, and how quickly?
3. Drought seems to me one of the most serious adverse effects we can expect with a warming climate. The Medieval Warm time seemed to be a more drought-stricken world, and the forecast from the Hadley Centre model for PDSI drought severity index under doubled CO2 look apocalyptic. Are these projections right?
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