Is
the R.E.M. song too apocalyptic? Scientists at Scripps Institution
of Oceanography bring us face to face with the bleak realities
of global warming and the consequences of our present-day energy
consumption.
Global warming is here. That is immediately clear when you talk
to climate scientists at Scripps. Denying global warming is the
scientific equivalent of denying that the earth is round, according
to Richard Somerville, meteorologist at Scripps. The average global
temperature has risen 0.6° C. in the last century. During that
time, Northern Hemisphere temperatures rose more than at any time
in the last 1,000 years. The 1990s were the warmest decade on record,
and the year 1998 was the hottest.
Switzerland is wrapping the upper Gurschen glacier with reflecting
foil to try and forestall its melting. Houses in the Arctic sink
and sag because the permafrost is melting. Arctic sea ice is breaking
up earlier in the season, harming polar bears by shortening their
hunting season. Virtually all the world’s glaciers are melting
and those in Glacier National Park will likely be gone in 30 years.
Antarctica is shrinking. Sea levels are rising and low-lying countries
are feeling the threat. The tiny country of Tuvalu in the southwest
Pacific Ocean already has a plan to evacuate to New Zealand. Any
one of these problems alone could be a scientific anomaly but these
changes, and more, are not isolated events. They are part of a
consistent pattern all in the same direction—
a warming planet.
“
This is the granddaddy of all environmental problems,” says
Charles Kennel, director of Scripps, an institute that has been
a leader in the climate-change game for the last half-century. “It
is the one environmental issue that affects every human being,
every living creature . . . on the surface of the earth.” What
will happen if global warming continues, unchecked? Tim Barnett,
marine geophysicist at Scripps, predicts serious calamities in
our near future, and thinks current debates in Washington will
seem inconsequential compared to future disasters due to global
warming. “I have to laugh talking about social security in
2042; what a joke. They (politicians) will have a lot more serious
problems on their hands between now and then.”
Despite the evidence of current warming, and the urgency felt
by scientists like Barnett, some people still see global warming
as
a controversial topic. Oklahoma Republican James Inhofe stood
on the floor of the U.S. Senate in October 2003 and called global
warming a hoax, more religious belief than science. And Michael
Crichton’s novel State of Fear, portraying global warming
as a malevolent conspiracy launched by homicidal environmentalists,
has been hailed by some as an authoritative treatise on the science.
But among the actual researchers, is the reality of global warming
a contentious topic?
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| Naomi Oreskes, History of Science professor at UCSD |
No. “I study scientific disputes, this isn’t one of
them,” says Naomi Oreskes, History of Science professor
at UCSD. To come to this conclusion she analyzed all the scientific
papers published on climate change that were listed in a bibliographic
database from 1993 to 2003. Her results were striking. Of the
700
or so papers that were relevant to current or future climate
change, all explicitly or implicitly agreed with the view that
in the last
50 years Earth warmed because of human-produced greenhouse gasses.
“
It is no more a ‘belief’ to say that Earth is heating
up than it is to say that continents move, that germs cause disease,
that DNA carries hereditary information,” Oreskes wrote in
an 2004 op-ed piece in the Washington Post. “This is not
a dispute about science,” she added in an interview with
@UCSD magazine, “this is a dispute about policy.”
The Greenhouse Effect
Not all greenhouse gasses are bad; the greenhouse effect is a natural
phenomenon that makes our planet livable. If it weren’t
for gasses like water vapor and carbon dioxide (CO2), our climate
would be like the moon—colder and with extreme differences
between brutally frigid nights and sizzling, hot days. But unlike
the moon, the earth has an atmosphere that traps heat. Cloudy
nights are warmer than clear nights because of the heat-trapping
effect of water vapor in clouds. But global warming has occurred
because humans are intensifying the greenhouse effect. Burning
fossil fuels to drive our cars, cool our homes, and run our factories
releases tons of CO2 into the atmosphere that will stay there
for a century.
Enter Scripps
In the beginning, climate-change science was all about what caused
ice ages. Not all of these dramatic changes in climate were millions
of years ago. Europe and surrounding areas were warmer around
900-1300 A.D., allowing the Vikings to settle in Greenland, and
it was colder from about 1300-1900, as is evidenced by paintings
of ice skaters and snowy scenes in English towns, which now only
rarely see temperatures below freezing. Our climate has always
been highly variable.
The role of gasses such as CO2 in climate change was first understood
in the 1800s. The first scientist to predict that industrialization
would increase atmospheric CO2, and subsequently temperature, was
Svante Arrhenius, grandfather of current Scripps faculty member
Gustaf Arrhenius. With only pencil, paper and six months of tedious
calculations, which he called the most boring six months of his
life, according to his grandson, he calculated that a doubling
of CO2 would raise the average global temperature about 5 or 6° C,
eerily similar to current predictions. But scientists assumed that
the oceans, which already contained much more carbon than the atmosphere,
would absorb any excess CO2 produced by industrial activities.
As might be expected, the oceans were how Scripps entered the global
warming game. Scripps’ Roger Revelle went to Bikini Atoll
to study the effects of nuclear tests on ocean chemistry and unexpectedly
discovered that the oceans were not limitless sinks for CO2. Revelle
was intrigued enough to hire a young upstart, Dave Keeling. Keeling
was the first to show that atmospheric CO2 was, and is, steadily
rising (see page 29). That was the beginning, and the science of
climate change, at Scripps and around the world, has never been
the same.
Ancient Bubbles
Jeff Severinghaus studies bubbles. Not just any bubbles, but bubbles
of ancient air locked deep in polar ice. Unlocking these air
samples reveals a striking fact: in the past our climate changed
very rapidly. According to Severinghaus there have been times
when the climate warmed as much as 15° C (the difference
between an ice age and a non-ice age) in only 10 years.
Severinghaus regularly travels to Greenland and Antarctica. In
such places with permanent snow and ice, the difference between
summer and winter creates annual layers that can be read like tree
rings, although ice layers are even more precise. Scientists can
also identify global events like dust storms and volcanic eruptions
that help calibrate the dating.
The longest and oldest core is two miles long and can be dated
back 900,000 years, giving us information about the planet’s
climate even before modern Homo sapiens existed. Handling a two-mile-long
piece of ice, 4 inches in diameter, is a challenge. The solution
is that they cut the core into
1-meter lengths as it is being extracted, store them in cardboard
tubes (carefully labeled), and ship them to the National Ice Core
Laboratory in Denver, “a freezer the size of a Wal-Mart,” according
to Severinghaus.
Shipping and storing ice around the globe is no small task and
there have been disasters. One American ship carrying an ice core
lost power and sat in the tropics for days. What had once been
invaluable scientific data turned into some very overpriced water.
Severinghaus uses his samples to analyze the gasses that have been
trapped in bubbles in the ice and identifies small changes in the
abundance of different isotopes, or forms, of nitrogen and argon,
which are stable, common and predictable components of air. “The
only thing that affects them is temperature in the snow and a few
other processes we can correct for,” he says. “This
makes a clean recorder of temperature.” When there is a change
in temperature, the heavier and lighter isotopes of these elements
move differently through the snow. When the snow turns to ice it
is no longer porous and the air is trapped—and Severinghaus
has a story to decipher. Luckily for Severinghaus these changes
are imposed on a calendar of sorts—the annual layers in the
ice. A change in the ratio of isotopes is evidence of climate change,
but seeing that change within a small number of layers is evidence
of abrupt climate change. Severinghaus has documented these abrupt
changes at numerous time periods, from 8,000 to 100,000 years ago.
The reason for these abrupt changes is still a great mystery, although
the most popular hypothesis has to do with ocean circulation patterns
turning off and then on again, due to the different densities of
water at different temperatures and salt concentrations. But the
important conclusion is that climate change has, at times, been
more like a switch than a dial and because the switch has been
abruptly flipped in the past, there is no reason to think it could
not flip again. Although these abrupt changes occurred long ago,
without the influence of humans, that doesn’t mean that humans
can’t also trigger such events. Severinghaus makes the point, “Forest
fires have natural causes, like lightning. But that doesn’t
mean that careless campers can’t also cause forest fires.” PAGE2
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