Projections of a large sea-level rise this century depend on rapid ice loss from Greenland and/or Antarctica. Yes, as ocean waters warm, they expand, but this expansion-induced rise is pretty well constrained and limited to being about 6 inches plus or minus a couple of inches by century’s end. And the contribution from melting glaciers/ice in other parts of the world (not counting Greenland and Antarctica) is even smaller, maybe 2-4 inches. So that adds up to about 8-12 inches of sea level rise by the year 2100—not much different than that which has already occurred over the past century. This is hardly catastrophic.
So getting a good handle on the contributions from Antarctica and Greenland is essential if you want to develop a reasonable expectation for the future. Lacking a good handle leads to unreasonable projections.
Here is an example of the latter.
A breathless passage from the book version of Al Gore’s An Inconvenient Truth:
I flew over Greenland in 2005 and saw for myself the pools of meltwater covering large expanses on top of the ice. …These pools have always been known to occur, but the difference now is that there are many more of them covering a far larger area of ice. …In Greenland, as in the Antarctic Peninsula, this meltwater is now believed to keep sinking all the way down to the bottom, cutting deep crevasses and vertical tunnels that scientists call “moulins.”
When water reaches the bottom of the ice, it lubricates the surface of the bedrock and destabilizes the ice mass, raising fears that the ice mass will slide more quickly towards the ocean.
…If Greenland melted or broke up and slipped into the sea—or if half of Greenland and half of Antarctica melted or broke up and slipped into the sea, sea levels worldwide would increase by between 18 and 20 feet.
Tony Blair’s advisor, David King, is among the scientists who have been warning about potential consequences of large changes in these ice shelves. At a 2004 conference in Berlin, he said: THE MAPS OF THE WORLD WILL HAVE TO BE REDRAWN. [all caps in original]
Gore went on to include page after page of now and then maps of the world’s major cities after a sea level rise of 20 feet (of course, assuming no adaptive measures put in place).
But Gore’s disaster mechanism has been shown to be impotent and ineffective. In fact, a collection of recent papers published in the peer-reviewed scientific literature basically dispels all myths foretelling a large sea level rise this century coming from ice loss on Greenland. Recent research on Antarctica largely does the same.