Part of the problem with Steve Koonin's analysis is that he concentrates too much on claims about extreme weather events and not enough on the probability of West Antarctica and
Greenland destabilizing during the 21st century. Those are 2 issues that climate scientists have been very concerned about for a long time. As Greenland melts its height diminishes
and the portions that are melting become darker. As Greenland's height diminishes the air temperature increases, causing ice melt to accelerate, which causes the height to drop
even faster in a positive feedback process. The darker color of the melting ice absorbs more solar radiation than snow, so there is another positive feedback loop accelerating ice melt.
There are other positive feedback mechanisms related to the growth of algae and melt water lubricating ice flow.
Forty-six years of Greenland Ice Sheet mass balance from 1972 to 2018 | PNAS
A 6-fold increase in ice melting into the ocean from Greenland was measured from the 1980's to the 2010-2018 period.
We reconstruct the mass balance of the Greenland Ice Sheet using a comprehensive survey of thickness, surface elevation, velocity, and surface mass balance (SMB) of 260 glaciers from 1972 to 2018. We calculate mass discharge, D, into the ocean directly for 107 glaciers (85% of D) and indirectly for 110 glaciers (15%) using velocity-scaled reference fluxes. The decadal mass balance switched from a mass gain of +47 ± 21 Gt/y in 1972–1980 to a loss of 51 ± 17 Gt/y in 1980–1990. The mass loss increased from 41 ± 17 Gt/y in 1990–2000, to 187 ± 17 Gt/y in 2000–2010, to 286 ± 20 Gt/y in 2010–2018, or sixfold since the 1980s, or 80 ± 6 Gt/y per decade, on average
From Inside Climate News
Going, Going ... Gone: Greenland’s Melting Ice Sheet Passed a Point of No Return in the Early 2000s - Inside Climate News
Other research suggests that, in previous geologic eras, nearly the entire Greenland Ice Sheet melted when global temperatures were near today’s levels, showing that even the thickest, coldest parts of Greenland are vulnerable to just a few degrees of warming.
When all Greenland’s ice melts, it will raise sea level by 20 feet. That could take 10,000 years, but jolts to the climate system like the glacier acceleration in the early 2000s, combined with the effects of the growing spread of ice-darkening algae and black carbon, the amount of meltwater saturating of the snow atop the ice or changes in ocean currents flowing near the glaciers could speed that up by thousands of years, Howat said. When a tongue of ice breaks free from its seafloor anchor, the flow of the glacier above it accelerates.
“If climate warming continues, technically the ice sheet is doomed,” said Greenland ice researcher Jason Box, with the Geological Survey of Denmark and Greenland, who was not involved in the new study.
Ice loss would accelerate even more once the top of the ice sheet, which rises to 10,000 feet above sea level, melts down to a lower and warmer level of the atmosphere. Only a long series of very cold years could stabilize the ice, Box said. “What matters more is the climate trajectory, Is there any chance of cooling in the foreseeable future?”