| Dear
EarthTalk: What is the issue with the Gulf
Stream in relation to global warming? Could it really stop
or disappear altogether? If so, what are the ramifications
of this?
--
Lynn Eytel, Clark Summit, PA
Part
of the Ocean Conveyor Belt—a great river of ocean
water that traverses the saltwater sections of the globe—the
Gulf Stream stretches from the Gulf of Mexico up the eastern
seaboard of the U.S., where it splits, one stream heading
for Canada’s Atlantic coast and the other for northern
Europe and Greenland. By taking warm water from the equatorial
Pacific Ocean and carrying it into the colder North Atlantic,
the Gulf Stream warms up the eastern U.S. and northwestern
Europe by about five degrees Celsius, making those regions
much more hospitable than they would otherwise be.
Among
the greatest fears scientists have about global warming
is that it will cause the massive ice fields of Greenland
and other locales at the northern end of the Gulf Stream
to melt rapidly, sending surges of cold water into the ocean
system and interrupting the flow of the Ocean Conveyor Belt.
One doomsday scenario is that such an event would stop or
disrupt the whole Ocean Conveyor Belt system, plunging Western
Europe into a new ice age without the benefit of the warmth
delivered by the Gulf Stream. “The possibility exists
that a disruption of the Atlantic currents might have implications
far beyond a colder northwest Europe, perhaps bringing dramatic
climatic changes to the entire planet,” says Bill
McGuire, a geophysical hazards professor at University College
London’s Benfield Hazard Research Centre.
Computer
models simulating ocean-atmosphere climate dynamics indicate
that the North Atlantic region would cool between three
and five degrees Celsius if Conveyor circulation were totally
disrupted. “It would produce winters twice as cold
as the worst winters on record in the eastern United States
in the past century,” says Woods Hole Oceanographic
Institution’s Robert Gagosian.
The
slowing of the Gulf Stream has been directly linked with
dramatic regional cooling before, says McGuire. “Just
10,000 years ago, during a climatic cold snap known as the
Younger Dryas, the current was severely weakened, causing
northern European temperatures to fall by as much as 10
degrees Fahrenheit,” he says. And 10,000 years earlier—at
the height of the last ice age when most of northwestern
Europe was a frozen wasteland—the Gulf Stream had
just two-thirds of the strength it has now.
A
less dramatic prediction sees the Gulf Stream slowing down
but not stopping entirely, causing the east coast of North
America and northwestern Europe to suffer only minor winter
temperature dips. And some scientists even put forth the
optimistic hypothesis that the cooling effects of a weakened
Gulf Stream could actually help offset the higher temperatures
otherwise caused by global warming.
To McGuire, these uncertainties underscore that fact that
human-induced global warming is “nothing more nor
less than a great planetary experiment, many of the outcomes
of which we cannot predict.” Whether or not we can
trim our addiction to fossil fuels might just be the determining
factor in whether global warming wreaks havoc around the
world, or just causes us minor annoyances.
CONTACTS:
University
College London’s Benfield Hazard Research Centre;
Woods Hole
Oceanographic Institution.
Dear
EarthTalk: Is it true that anti-bacterial soaps
are no better at preventing infections than plain soaps
and that they are actually harmful to the environment?
-- Avery Bicks,
New York, NY
University of
Michigan researchers reviewed numerous studies conducted
between 1980 and 2006 and concluded that antibacterial soaps
that contain triclosan as the main active ingredient are
no better at preventing infections than plain soaps. Further,
the team argued that these antibacterial soaps could actually
pose a health risk, because they may kill beneficial bacteria
and also reduce the effectiveness of some common antibiotics,
such as amoxicillin. The study was published in the August
2007 issue of the peer-reviewed journal, Clinical Infectious
Diseases.
These findings
concur with earlier research conducted by Tufts University’s
Alliance for the Prudent Use of Antibiotics. The Tufts study
concluded that overuse of triclosan could cause new strains
of bacteria to develop, thus “changing the kind of
bacteria in our houses to those that may actually be harmful
or resistant to antibiotics…” said Tufts’
Dr. Stuart Levy.
According to
the non-profit group Beyond Pesticides, laboratory studies
have found a number of different strains of mutated bacteria
that are resistant to triclosan and to certain antibiotics.
The organization also cites reports of triclosan converting
into a carcinogenic class of chemicals known as dioxins
when exposed to water and ultraviolet radiation. Besides
cancer, dioxins have been linked to weakening of the human
immune system, decreased fertility, altered sex hormones
and birth defects.
If antibacterial
hand soap is not effective at reducing infections, consumers
may wonder about whether alcohol-based hand sanitizers may
do a better job. Combing through different studies on the
topic yields mixed conclusions. According to one study conducted
at Colorado State University, alcohol-based hand sanitizers
were as much as twice as effective as either regular soap
or antibacterial soap at reducing germs on human hands.
A Purdue University
study, however, contradicts these findings, concluding that
while alcohol-based hand sanitizers may kill more germs
than plain or triclosan-based soaps, they do not prevent
more infections that make people sick. Instead they may
kill the human body’s own beneficial bacteria by stripping
the skin of its outer layer of oil.
The best advice
might just come from a study published in the journal Dairy,
Food and Environmental Sanitation back in 1998, which concluded
that washing hands thoroughly for 20 seconds or more with
plain soap and warm water is by far the most effective way
to reduce harmful bacteria, and as such remains our best
defense against getting sick.
CONTACTS:
Clinical
Infectious Diseases; Tufts’
Alliance for the Prudent Use of Antibiotics; Beyond
Pesticides. |
