Source: The Independent/UK
[Jan 26, 2004]
“We may be approaching a threshold that would shut down [the Gulf
Stream] and cause abrupt climate changes.”
Britain is likely to be plunged into an ice age within our lifetime by
global warming, new research suggests.
A study, which is being taken seriously by top government scientists,
has uncovered a change “of remarkable amplitude” in the circulation of
the waters of the North Atlantic.
Similar events in pre-history are known to have caused sudden “flips”
of the climate, bringing ice ages to northern Europe within a few
decades. The development – described as “the largest and most dramatic
oceanic change ever measured in the era of modern instruments”, by the
US Woods Hole Oceanographic Institute, which led the research –
threatens to turn off the Gulf Stream, which keeps Europe’s weather
mild.
If that happens, Britain and northern Europe are expected to switch
abruptly to the climate of Labrador – which is on the same latitude –
bringing a nightmare scenario where farmland turns to tundra and
winter temperatures drop below -20C. The much-heralded cold snap
predicted for the coming week would seem balmy by comparison.
A report by the International Geosphere-Biosphere Programme in Sweden
– launched by Nobel prize-winner Professor Paul Crutzen and other top
scientists – warned last week that pollution threatened to “trigger
changes with catastrophic consequences” like these.
Scientists have long expected that global warming could,
paradoxically, cause a devastating cooling in Europe by disrupting the
Gulf Stream, which brings as much heat to Britain in winter as the sun
does: the US National Academy of Sciences has even described such
abrupt, dramatic changes as “likely”. But until now it has been
thought that this would be at least a century away.
The new research, by scientists at the Centre for Environment,
Fisheries and Acquaculture Science at Lowestoft and Canada’s Bedford
Institute of Oceanography, as well as Woods Hole, indicates that this
may already be beginning to happen.
Dr Ruth Curry, the study’s lead scientist, says: “This has the
potential to change the circulation of the ocean significantly in our
lifetime. Northern Europe will likely experience a significant
cooling.”
Robert Gagosian, the director of Woods Hole, considered one of the
world’s leading oceanographic institutes, said: “We may be approaching
a threshold that would shut down [the Gulf Stream] and cause abrupt
climate changes.
“Even as the earth as a whole continues to warm gradually, large
regions may experience a precipitous and disruptive shift into colder
climates.” The scientists, who studied the composition of the waters
of the Atlantic from Greenland to Tierra del Fuego, found that they
have become “very much” saltier in the tropics and subtropics and
“very much” fresher towards the poles over the past 50 years.
This is alarming because the Gulf Stream is driven by cold, very salty
water sinking in the North Atlantic. This pulls warm surface waters
northwards, forming the current.
The change is described as the “fingerprint” of global warming. As the
world heats up, more water evaporates from the tropics and falls as
rain in temperate and polar regions, making the warm waters saltier
and the cold ones fresher. Melting polar ice adds more fresh water.
Ominously, the trend has accelerated since 1990, during which time the
10 hottest years on record have occurred. Many studies have shown that
similar changes in the waters of the North Atlantic in geological time
have often plunged Europe into an ice age, sometimes bringing the
change in as little as a decade.
The National Academy of Sciences says that the jump occurs in the same
way as “the slowly increasing pressure of a finger eventually flips a
switch and turns on a light”. Once the switch has occurred the new,
hostile climate, lasts for decades at least, and possibly centuries.
When the Gulf Stream abruptly turned off about 12,700 years ago, it
brought about a 1,300-year cold period, known as the Younger Dryas.
This froze Britain in continuous permafrost, drove summer temperatures
down to 10C and winter ones to -20C, and brought icebergs as far south
as Portugal. Europe could not sustain anything like its present
population. Droughts struck across the globe, including in Asia,
Africa and the American west, as the disruption of the Gulf Stream
affected currents worldwide.
Some scientists say that this is the “worst-case scenario” and that
the cooling may be less dramatic, with the world’s climate
“flickering” between colder and warmer states for several decades. But
they add that, in practice, this would be almost as catastrophic for
agriculture and civilisation.
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