OCEANS’ ROLE IN
GLOBAL
WARMING
Recent scientific research has reinforced and strengthened our knowledge
of the oceans’ role in global warming.
Oceans are the source of more than 80
percent of atmospheric moisture and they
moderate coastal temperatures around
the world. Every student of physical geography understands how ocean currents
influence Western Europe’s weather and
climate.
The recent research,
however, underscores the
magnitude of the oceans’
role in global warming.
Oceans serve as a heat
sink, absorbing heat from
the atmosphere and storing it in massive amounts.
By calculating the amount
of heat stored in the
oceans, oceanographers
and meteorologists have
added a critical dimension to global climate
models.
Climate models have
long predicted global
warming associated with
greenhouse gases. These
gases are mostly carbon
dioxide, methane and nitrogen oxides. Those portions of these gases that
are produced as a result of human activities are the ones that are of concern. They
trap the earth’s heat and keep it from
returning to space.
Earlier models poorly predicted the
effects, for example, of the last 250 years
of fossil fuel combustion. Fossil fuel is the
source of more than 80 percent of greenhouse gases. Something significant remained missing from the models, causing them seemingly to over-predict the
cording to Levitus. The Atlantic, Pacific
and Indian ocean basins have warmed
1.08 F. (0.6 C.) in 40 years.
As almost a footnote—although very
significant—was the recent discovery reported in Nature (June), that there has
been a substantial reduction in cold, deep
seawater flowing from the Arctic to the
Atlantic. As reported in the New York
Times (June 21), the diminished flow of
cold water seems to have also lessened
the flow of the warm Gulf Stream/North
Atlantic Drift toward Europe. The result
has been the cooling of parts of the Norwegian coast.
The world’s oceans cover 71 percent
of the earth’s surface. But unlike land
surface, which is heated and cooled to
depths of only a few feet by the sun, the
ocean is somewhat transparent, allowing
solar light and energy to penetrate to
much greater depths.
Based upon this new research, recent
warming of the world’s oceans has delayed atmospheric warming. This means,
however, that if we ceased adding more
greenhouse gas to the atmosphere today,
effects. Where was the missing heat going?
Richard A. Kerr recently described
several interlinked studies in his article,
“Greenhouse Warming Passes Test” (Science Now, 12 April).
The most significant study was by
oceanographer Sydney Levitus and colleagues at the National Oceanic and Atmospheric Administration (NOAA). They
calculated the heat gain in the top 9,840
feet (3,000 m.) of the world oceans (Science, 24 March 2000). They found that the
amount of heat absorbed by the oceans
between 1955 and 1996 was 10 times as
much as went into warming the earth’s
atmosphere. They concluded that the
oceans are almost the only variables that
matter in understanding the complexities
of global warming.
Adding the heat absorbed by the
oceans, climate modeler Tim P. Barnett at
the Scripps Institution of Oceanography
recalculated the global warming effects
of human-produced greenhouse gases.
He concluded that the warming closely
matched the strength and geographical
Water World
Arctic Ocean
Atlantic
Ocean
Pacific
Ocean
Pacific
Ocean
Indian
Ocean
S o u t h e r n
Geography in the News 7/13/01
distributions of the actual global warming. He concluded with 95 percent confidence that human-produced greenhouse
gases were behind real-world warming
(Kerr).
Furthermore, Levitus’ group was able
to gather millions of old ocean temperature records from around the world and
create a geographical inventory described
in the “Missing Warming” (Science, 24
March). “The whole-Earth system has
gone into a relatively warm state,” ac© 2001 maps.com
O c e a n
©2001 maps.com
the earth’s atmosphere would continue to
warm for years as heat is returned from
the oceans. Thus, the oceans’ role in receiving, trapping and slowly releasing
heat appears to be the key to understanding how global climate change works.
And that is Geography in the News.
July 13, 2001. #580
(The author is a Professor of Geography
at Appalachian State University, Boone, NC.)