Global warming, the slosh factor

We've seen so many alarmist stories about global warming that we were delighted to see a refreshingly dispassionate report on the prosaic side of sea-level rise.

The National Oceanic and Atmospheric Administration study focused on "nuisance" flooding, what the National Weather Service calls "minor" flooding – water sloshing onto roads, into yards, or perhaps into homes that aren't elevated.

Sea levels generally have been rising for centuries, the result of melting glaciers and thermal expansion of the oceans. (The Dutch can tell you all about it.)

With an uptick in warming -- and far bigger one in development – the incidents of nuisance flooding have increased dramatically.

Philadelphia has been a particularly busy venue.

Among the 45 locations studied, Philadelphia ranked third in terms of the increase in minor flooding. Fewer than two were occurring annually in the 1957-1963 period, compared with 12 a year in the 2007-13 period, according to the report.

One feature of the study we particularly liked was the discussion of the nonlinear nature of sea-level rise.

So far it has been a bigger deal on the East and Gulf Coasts than on the West Coast, and that has to do with the slope of the continental shelves and the sinking of land.

On average, overall sea level has risen about at the rate of about an inch every 16 years, but in the Chesapeake Bay region the rate is as high as an inch every five years, and an inch every 2.5 years along the Texas coast.

In the latter regions, subsidence – or the sinking of land – is a major factor in the change of relative sea level. Along the Gulf Coast, a major contributor is the extraction of oil and subsurface freshwater.

The flooding trend is likely to persist as waters rise.

The authors point out that this could mean more trouble for storm-water systems, other infrastructure, and, of course, motorists.