Since about 1850, the U.S. coast has been hit by only three
Category 5 storms. That's hardly enough to hazard when and where
they will strike again. And yet, these destructive storms are
precisely the ones it would be most useful to predict.
Practitioners of the new science of "paleotempestology" believe
they have a solution. Written records may date back only 150 years,
but the history of older and even ancient storms remains —
buried underground, captured in ancient charcoal, hidden away in
caves. The paleotempestologists' goal: to free this history,
filling in the record of intense hurricanes and other major storms
through thousands of years ago.
Paleotempestologists plumb the depths of Western Lake near
Panama City, Fla., for "sediment cores." The layers of mud and sand
found in each core give researchers an impression of the storm
activity that washed sand ashore, indicating a likely hurricane
that can be radiocarbon-dated. Cores from this site indicated three
distinct sand layers, dating back to roughly 1,800, 1,400, and
1,300 years from today.
"It's the uncertainty that kills people, or concerns people," says
Kam-biu Liu, a leader in the field and professor of oceanography
and coastal sciences at Louisiana State University. "So
paleotempestology, by extending the period of observation, can help
us to better define and to reduce that uncertainty."
Liu made headlines early this spring when he announced that the
Gulf Coast appeared to be in a thousand-year period of few Category
4 and Category 5 storms making landfall. Four sites along the coast
from New Orleans to the Florida Panhandle had been hit only once by
Category 4 or 5 storms in the current millennium, although they
were blasted more often during the period between 3,800 and 1,000
years ago, Liu reported.
He drew his findings from perhaps the most mature of
paleotempestology's emerging tools: sediments retrieved from
coastal lake or marsh bottoms.
Captured in long tubes plunged deep into the muck, those sediments
are composed of muck interspersed with layers of sand. Liu contends
that the sand was deposited in major storms, when surge picked up
the sand from the beach and dumped it into the lake or marsh. "If
the storm surge is high enough, it would overtop the coastal sand
barrier, and it would wash the sand into the bottom," Liu
There are caveats. Some critics argue that the coast may have been
different in the past. That could mean the study lake was far away
from the ocean, and the sand deposited by, say, a river. Liu says
examination of tiny fossils reveal the old sand contained the same
organisms found near the beach today, suggesting the lake's setting
Regardless of how that argument plays out, paleotempestology is
gathering momentum. Liu notes that scientists are mining corals,
tree rings, and stalagmites for evidence of ancient hurricanes. All
appear to contain a heavy oxygen isotope that is common in rain
from large hurricanes but otherwise very rare, suggesting that the
isotope may serve as a good indicator of past major storms, he
Between Texas and Maine, Liu adds, there are perhaps a dozen
"paleoweather" stations — sites where researchers have sought
to determine ancient hurricane activity. Many more are needed
before paleotempestology becomes a useful predictive tool. "How
accurate could our normal weather forecasting be if we had only a
dozen weather stations along our entire coastline?" he asks.
— Aaron Hoover