Environmental Engineering Reference
In-Depth Information
A 2002 report by the National Academy of Sciences said, “Avail-
able evidence suggests that abrupt climate changes are not only possible
but likely in the future, potentially with large impacts on ecosystems
and societies.”
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This was echoed in 2008 by James Hansen, director
of NASA's Goddard Institute of Space Studies who described the climate
as nearing dangerous tipping points.
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Examples of possible tipping
points that cause sleepless nights for climatologists include the rapid
disintegration of the Greenland and Antarctic ice sheets with an accom-
panying rise of perhaps tens of feet in sea level within a few years; a
sharp decrease in rainfall and consequent dieback of the Amazon rain
forest with loss of its absorption of carbon dioxide; rapid release of
methane from shallow-buried methane hydrates causing a major increase
in the rate of global climate change; disruption of the Indian summer
monsoon and West African monsoon with harmful effects on agricul-
ture; and an infl ux of cold glacial meltwater causing a collapse of the
Atlantic thermohaline (conveyer belt) circulation that keeps Europe
habitable.
According to most climatologists, the Gulf Stream and its extension,
the North Atlantic Drift, supply Western Europe with an amount of free
heat equal to the output of about a million power stations. It keeps
Western Europe 10ºF to 20ºF warmer than it would normally be at its
latitude (frigid Labrador is at the same latitude). Without the Gulf
Stream, the average temperature in Europe might drop by as much as
10ºF in ten years or less; it has happened in the past.
About 12,700 years ago, average temperatures in the North Atlantic
Region abruptly plummeted about 9ºF and remained that way for 1,300
years before rapidly warming again. A similar abrupt cooling occurred
8,200 years ago. An abrupt warming took place about 1,000 years ago,
allowing the Norse to establish settlements in Greenland. The climate
turned abruptly colder 700 years ago, forcing the Norse to abandon their
Greenland settlements. Between 1300 and 1850, severe winters had
profound agricultural, economic, and political impacts in Europe.
Total disruption of the Gulf Stream and North Atlantic Drift would
produce winters twice as cold as the worst winters on record in eastern
United States in the past century. Abrupt regional cooling may occur
even as the earth's average temperature continues to warm. In addition,
previous shutdowns have been linked with widespread droughts around
the globe. The new conditions would likely last for decades to centuries
until conditions reached another threshold, at which time the circulation
might revert back to the current state.
