|Image from the earlier post: Accelerated Arctic Warming|
As has been described in earlier posts at this blog, the current speed of change is unprecedented in history, and this is destabilizing the Arctic and threatening to unleash huge amounts of methane from the seabed and escalate into runaway warming. Comprehensive and effective action is therefore desperately needed.
Views on this from other people follow below.
Basic premise about stability of Greenland Ice sheet is wrong. In previous interglacials summers were much hotter but winters were much colder (more extreme seasonality); this helped maintain both sea ice and Greenland ice. CO2 and CH4 stayed within narrow bands much lower than now. Now, reason for melt is completely different. GHG much higher now; temps higher year round so recovery less robust in winter. Before troposphere and stratosphere warmed; now troposphere warming like crazy and stratosphere cooling. Lapse rates did not change much before, now lapse rate is slower so more warming higher up (recall extreme melt at 3100 m on Greenland peak; in fact on entire Greenland surface; well 97%). Daily lows much higher now then before due to GHG trapping at night; not the case before. GHG concentrated more at pole since tropopause only 7 km high (compared to CH4 wetland emissions from wetlands near equator where tropopause is 17 km high). Over Greenland summit only 4km up to tropopause). Also more black carbon now to kill snow/ice albedo. Not looking too good for the home team (us).
Also, with warmer upper troposphere from reduced lapse rate colder stratosphere now (not so in previous interglacials) there is no surprise that SSWs (sudden stratospheric warming) events are occurring more frequently...
Further views will be added below. Please comment!