Discussing the potential ramifications of global warming during his May 8 broadcast, Newsradio 850 KOA host Mike Rosen stated without substantiation that former Vice President “Al Gore's worst case is a great exaggeration,” adding, “Gore's projection for rising sea levels are considerably higher than the consensus calls for.” Yet while Rosen claimed that Gore's estimates depart “even from what the [Intergovernmental Panel on Climate Change] is calling for,” the IPCC's latest findings in fact substantiate Gore's warning that sea levels could rise by 20 feet if the West Antarctic ice shelf or the Greenland ice sheet were to melt into the ocean.

From the May 8 broadcast of Newsradio 850 KOA's The Mike Rosen Show:

ROSEN: Projections about what'll happen a hundred, or two hundred, or three hundred years from now to the environment, based on all kinds of variables that we can't begin to fully understand and things that will impact us from outside that we have no knowledge of now, are far more abstract than theoretical. But even taking Al Gore's worst case -- and Al Gore's worst case is a great exaggeration, even from what the IPCC is calling for -- IPCC? Intergovernmental Panel on Climate Change -- OK -- IPCC, yes. Al Gore's projection for rising sea levels are considerably higher than the consensus calls for, and even the consensus can't possibly know; it's only projections based on computer models, and the assumptions built into those computer models are debatable. But even if you take the worst case: So we'd have rising sea levels in New York -- Manhattan would be underwater. And the, the ice caps would shrink although they'd still be there, and some parts of this planet would be less habitable than they are now. Worst case. Human life would still survive, and environmental catastrophes might result in a sharp cutback in the human population. Maybe a billion or 2 billion fewer people on this planet, but we'd still survive, there'd still be 4 billion people on this planet. And we would adjust.

As Media Matters for America has noted, in his book An Inconvenient Truth (Rodale Books, May 2006), Gore wrote of the West Antarctic ice shelf (page 190):

[I]f it melted or slipped off its island mooring into the sea, it would raise sea levels worldwide by 20 feet. Second, the ocean flows underneath large sections of this ice shelf, and as the ocean has warmed, scientists have documented significant and alarming structural changes on the underside of the ice shelf.

Regarding Greenland, Gore wrote:

Interestingly, the West Antarctic ice shelf is virtually identical in size and mass to the Greenland ice dome, which also would raise sea levels worldwide by 20 feet if it melted or broke up and slipped into the sea.

Gore advanced the same theories in his film (Paramount Classics, May 2006):

GORE: If [the West Antarctic ice shelf] were to go, sea level worldwide would go up 20 feet. They've measured disturbing changes on the underside of the ice sheet. It's considered relatively more stable, however, than another big body of ice that's roughly the same size -- Greenland would also raise sea level almost 20 feet if it went.

As Media Matters further noted, New York Times science writer William J. Broad similarly compared Gore's sea level projections with the IPCC's estimation “that the world's seas in this century would rise a maximum of 23 inches.” Unlike Rosen, Broad nevertheless acknowledged that Gore cited “no particular time frame” in which the seas could rise by 20 feet.

A more apt comparison of Gore's observations with those in the IPCC report would underscore the IPCC's summary determination that "[c]ontraction of the Greenland ice sheet is projected to continue to contribute to sea level rise after 2100," and that "[i]f a negative surface mass balance were sustained for millennia, that would lead to virtually complete elimination of the Greenland ice sheet and a resulting contribution to sea level rise of about 7 m. [about 23 feet]."

Similarly, as the full IPCC report indicates regarding the West Antarctic ice sheet:

Recent satellite and in situ observations of ice streams behind disintegrating ice shelves highlight some rapid reactions of ice sheet systems. This raises new concern about the overall stability of the West Antarctic Ice Sheet, the collapse of which would trigger another five to six metres [16.4 to 19.6 feet] of sea level rise. While these streams appear buttressed by the shelves in front of them, it is currently unknown whether a reduction or failure of this buttressing of relatively limited areas of the ice sheet could actually trigger a widespread discharge of many ice streams and hence a destabilisation of the entire West Antarctic Ice Sheet.