The large waves, storm surge, and flooding that Hurricane Earl
will spawn as it strikes Massachusetts tonight comes with an
added dollop of trouble: sea level rise. Very gradual, and in
some cases accelerating, rises in sea level off our coast over
the last century will boost the height of Earl’s storm surge —
expected to be 1 to 4 feet — meaning the wall of water will be
able to travel that much farther inland and over higher
elevations to flood basements, streets, and other low-lying
areas. Although scientists agree that sea level rise contributes
to flooding during severe storms, exactly how much can be hard
to determine because coastal flooding depends on tides, winds,
and topography. Sea levels can also vary by several feet from
one region to another, and even from season to season, because
of ocean circulation and other factors. Sea level is rising,
scientists say, largely because of a global warming double
punch: higher ocean temperatures that expand the volume of water
and melting glaciers that add wa