07/24/2008 05:12 am ET Updated May 25, 2011

Sea Levels Rising: What You Need To Know

Q. Dear Umbra,

I'm a bit confused about the possible rise in sea level that may be caused by global warming. I know that in general water expands when warmed, and that is one cause of sea level elevation with respect to global warming. The larger cause for alarm seems to be the melting or collapse of the polar ice caps. I recently read an article that warned that Antarctica, which stores 70 percent of the world's fresh water, could lose the Ross Ice Shelf (a block of ice the size of France) suddenly and without warning and "that its collapse would make sea levels rise by at least 5 meters, with other estimates predicting a rise of up to 17 meters." My question is how quickly would such a rise register?

Mill Valley, Calif.

A. Dearest Saor,

I got all swept up and joined your completely logical confusion. If ice shelves collapse, when can we expect the swamping wave? Happily, this is incorrect thinking. Many thanks to the good people at Environmental Defense for straightening out my confusion. My mind now runs clear as a glacial river to the sea of climate comprehension.

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