It’s Hot But Don’t Blame Global Warming
By Cynthia Barnett – 2/1/2009
Morton D. Winsberg fell in love with Florida more than 50
years ago, but the Illinois-born geographer never quite got used to the dog days
In recent years, the Florida State University professor emeritus and author
of a book called “Florida Weather” began wondering: Is global climate change
making Florida’s hot season longer and hotter? With help from geography students
and researchers at FSU’s Population Center and Florida Climate Center, Winsberg
and co-author Melanie Simmons gathered and analyzed temperature data from 57
Florida weather stations going back six decades.
Their research showed that the hot season in Florida has gotten a lot hotter
— and longer — in some places, but not at all in others. The change, however, is
unrelated to global warming, the increase in the average temperature of the
earth’s atmosphere. Rather, they found, it’s a function of the lesser-known
phenomenon of local warming. The analysis “shows that weather can be very
local,” says Winsberg, “and also that weather can be a function of population
Winsberg found the most notable climate changes along the state’s
southeastern coast, where development and wetlands drainage have been heaviest.
In most areas he analyzed, the heat is getting more intense. Of the 57 weather
stations, 49 saw an increase in the number of days with an average temperature
of 80 degrees. When it came to the length of the hot season, the biggest
increase was in Hialeah, with a 72-day increase, followed by Miami, with a
Neither the intensity of the heat nor the increasing number of hotter days
was related to water temperatures in the Atlantic and Gulf, a fact that
surprised Winsberg. The heat trends also weren’t consistent across the state. In
fact, some areas, notably in the northeast part of the state, saw a shorter hot
season and a decrease in the number of dog days.
That evidence leads Winsberg and FSU meteorologists to blame the hot spots on
local land-use changes that accentuate the urban “heat-island” effect — the
pools of heat that large, dense concentrations of people produce in their local
climates. Cutting down trees, draining wetlands and pouring concrete all make a
place hotter, as anyone who’s walked across an asphalt parking lot on a summer
day knows, Winsberg says.
Geographer Morton Winsberg retired a decade ago,
At 78, Winsberg no longer worries about getting his
“I don’t play golf,” he explains. “I prefer
Winsberg spent his career traveling the globe and
Winsberg says he dreaded becoming the sort of
“I wanted to keep feeling useful and to be
Colleagues say he’s the only “emeritus” professor
On a regional level, state climatologist David Zierden says, historical
records show that southeastern Alabama, Georgia and north and central Florida
have not experienced steady warming, but rather relatively warm periods, such as
the 1930s through the 1950s, followed by relatively cool periods, such as the
1960s through the 1980s.
State climatologist David Zierden says Winsberg’s data bolsters his belief,
[Photo: Ray Stanyard]
Heavily drained or developed areas bucked those trends, however. The most
dramatic example in Winsberg’s study is the difference between Belle Glade, in a
part of the Everglades drained for sugar production, and undeveloped Everglades
City. Since 1950, Belle Glade has seen a 32% increase in its number of dog days,
while Everglades City has seen a 3% decrease. The transformation of swampland
around Belle Glade to farmland appears to have caused a significant rise in
temperatures. “The draining of the Everglades and the upturning of all that
black soil has really changed the local climate in that area,” says Zierden.
The idea of local climate change may seem contrarian at a time when
scientists and policy-makers focus on global warming and its causes, primarily
the release of carbon dioxide and other greenhouse gases into the atmosphere.
But Florida’s top global warming scientists, including Harold Wanless, chairman
of geological sciences at the University of Miami, agree that greenhouse gases
don’t seem to be impacting Florida’s temperatures. When it comes to global
warming, Wanless says, sea-level rise — caused by warming elsewhere,
particularly the Arctic — is the chief threat to Florida. Wanless predicts
Florida’s seas will rise three to five feet by century’s end.
As state and national policy-makers work to mitigate damages from the rising
seas, Winsberg says he hopes local officials and Floridians will use his data to
think more wisely about land-use changes and wetlands drainage.
“People just dread when the hot season begins, and they are so relieved when
it’s over,” says Winsberg. “We don’t want to extend the suffering.”