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ENVIRONMENT:
Climate Change
Only Partially to Blame
María
Amparo Lasso*
MEXICO CITY, (Tierramérica)
- This year's record-breaking
hurricane season in the North
Atlantic, with storms like
Katrina, Rita and Wilma wreaking
unprecedented destruction, can
only be partially attributed to
global warming, according to
scientists consulted by
Tierramérica.
Hurricane Wilma, which crashed
into Mexico's Yucatan peninsula
after pounding Cuba and Florida
with torrential rains and
gusting winds, was at one point
the most powerful Atlantic
hurricane on record, with an
all-time low barometric pressure
of 882 millibars and winds of up
to 270 km an hour.
Wilma destroyed hundreds of
hotels and tourism workers'
homes in the Mexican resort area
of Cancún, turned central Havana
streets into virtual rivers, and
left millions without electric
power in Miami, Florida..
Thousands of people will
continue to suffer its
devastating effects for months
to come.
But are these harrowing scenes
of destruction a direct result
of the global warming process
brought about by human activity,
as some observers and
environmental groups maintain?
The answer is no, according to
Judith Curry, a U.S. scientist
who has gained notoriety in
recent months precisely because
of her efforts to highlight the
correlation between tropical
cyclones and the warming of the
earth's atmosphere.
"We can't directly attribute the
intensity of a single storm, or
storms in a single season, to
global warming," said Curry,
chair of the School of Earth and
Atmospheric Sciences at the
Georgia Institute of Technology
in Atlanta, in an interview with
Tierramérica.
Global warming is a consequence
of the build-up of what are
known as greenhouse gases, like
carbon dioxide and methane,
which trap the Sun's heat in the
Earth's atmosphere.
The primary source of greenhouse
gas emissions is the burning of
fossil fuels (oil, natural gas
and coal). This warming process
has led to a rise in air and sea
temperatures and variations in
weather patterns collectively
known as climate change.
"This year, in the North
Atlantic and Caribbean,
hurricanes have been especially
intense since the sea surface
temperatures have been warmer
than usual and atmospheric
circulation patterns have been
favourable for hurricane
intensification," said Curry.
Hurricanes form at sea when
surface temperatures rise above
26.5 degrees Celsius, and draw
their destructive power from the
warm, moist air above the water.
The 2005 Atlantic hurricane
season, which does not
officially end until late
November, has already set a new
record for the number of storms
in a single year, with the
formation last week of Tropical
Storm Beta, this season's 23rd.
The previous record dated back
to 1933, when 21 storms were
registered.
There are numerous reasons for
this, according to Curry. "The
exceptional year can probably be
attributed to a combination of
greenhouse warming, El Niño, and
the North Atlantic Oscillation,"
she said.
The North Atlantic Oscillation (NAO)
is a large-scale pattern of
natural climate variability that
has been shown to fluctuate
across multi-decade cycles.
Another oft-cited scientist,
Kerry Emanuel of the
Massachusetts Institute of
Technology (MIT), agrees with
Curry.
In the Atlantic, where only 11
percent of the world's tropical
storms are recorded, the
intensity of hurricanes
corresponds to natural cycles.
"It's difficult to see a signal
from global warming there,"
remarked Emanuel.
"The terrific damage from these
storms (Katrina, Rita, Wilma)
depended on the fact that they
made landfall where and when
they did, and this is largely a
matter of chance," he told
Tierramérica.
Both Curry and Emanuel have been
under the spotlight in recent
months following the publication
of separate studies, based on
different methodologies, that
provide the first conclusive
evidence of an increase in the
intensity (not the number) of
tropical cyclones around the
world -- including North
Atlantic hurricanes -- in the
last 35 years, as a result of
the rise in average sea surface
temperatures.
Curry was co-author of a study
by scientist Peter Webster and
colleagues published by the
journal Science in September,
while Emanuel's study was
published by Nature magazine in
July.
Both believe that the worldwide
increase in sea surface
temperatures over the last few
decades is partially a result of
global warming, although Curry
stressed that there is no way to
determine its precise share of
the responsibility. And both
experts were cautious to avoid
blaming this man-made phenomenon
for the destructive force of any
specific hurricane.
Emanuel also emphasised that
there is no evidence of an
increase in the number of storms
around the planet.
"There are about 90 tropical
cyclones worldwide per year, and
this frequency of storms has
been rock steady," he stated.
The studies published by Emanuel
and Curry and her colleagues
served to heat up the highly
politicized debate over climate
change in the United States,
where the George W. Bush
administration has withdrawn the
U.S. signature from the Kyoto
Protocol aimed at curbing
emissions of the greenhouse
gases, despite being the world's
largest single source of these
emissions.
After Hurricane Katrina struck
the U.S. Gulf Coast on Aug. 29,
unleashing death, destruction
and 30 billion dollars in
damages on New Orleans and other
nearby towns and cities -- as
well as dealing a heavy
political blow to the Bush
administration -- the debate
over the role of global warming
and climate change in this
catastrophic storm sharply
divided the scientific
community.
Some specialists have even
refuted the claim that
hurricanes have increased in
intensity over the last 35
years, criticizing Emanuel and
Curry et al for limiting their
studies to satellite data dating
back to 1970, when there is
information gathered by aircraft
over the North Atlantic going
back to at least 1945. According
to their detractors, these data
prove that there have been
periods of storm activity in
previous decades just as intense
as what is currently being
witnessed.
A high degree of hurricane
activity was recorded between
the 1940s and 1960s, followed by
a period of relative calm from
the 1970s to the 1990s, until
the current cycle of renewed
intensity began in 1995,
according to the U.S. National
Oceanic and Atmospheric
Administration (NOAA).
Jorge Sánchez-Sesma of the
Mexican Institute of Water
Technology agrees. "The
frequency of hurricanes in the
1950s and 1960s was intense, and
we are now returning to those
conditions. There is a
significant contribution made to
global warming by
non-anthropogenic factors (not
caused by human activity) that
have not been taken into
account," he said.
Moreover, "the population and
cities have grown significantly
in the southeast coastal areas
of the United States and on the
coasts of Quintano Roo (on the
Yucatan Peninsula) in Mexico,
which makes us more exposed than
in the past," he added.
For his part, Patrick Michaels,
a professor at the University of
Virginia and researcher at the
Cato Institute, a libertarian
think tank based in Washington,
firmly maintains that global
warming had absolutely no
influence on either Hurricane
Wilma or Katrina.
Michaels is one of the most
outspoken critics of what he
calls the "media hysteria"
stirred up around global
warming, the political motives
behind climate change research,
and the millions of dollars in
taxpayers' money devoted to this
field in the United States.
The federal outlay on climate
research is now almost the same
as the amount given to the
National Cancer Institute, he
commented to Tierramérica.
If hurricanes had actually
doubled in power, the losses in
the insurance industry would be
catastrophic, and this is not
the case, he added.
(*María Amparo Lasso is
editorial director of
Tierramérica. Additional
reporting by Diego Cevallos in
Mexico. Originally published
Oct. 29 by Latin American
newspapers that are part of the
Tierramérica network.
Tierramérica is a specialised
news service produced by IPS
with the backing of the United
Nations Development Programme
and the United Nations
Environment Programme.)
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