Published on Friday, October 7, 2005 by TomDispatch.com
by Mike Davis
The genesis of two category-five hurricanes
(Katrina and Rita) in a row over the Gulf of
Mexico is an unprecedented and troubling
occurrence. But for most tropical meteorologists
the truly astonishing "storm of the decade" took
place in March 2004. Hurricane Catarina -- so
named because it made landfall in the southern
Brazilian state of Santa Catarina -- was the
first recorded south Atlantic hurricane in
history.
Textbook orthodoxy had long excluded the
possibility of such an event; sea temperatures,
experts claimed, were too low and wind shear too
powerful to allow tropical depressions to evolve
into cyclones south of the Atlantic Equator.
Indeed, forecasters rubbed their eyes in
disbelief as weather satellites down-linked the
first images of a classical whirling disc with a
well-formed eye in these forbidden latitudes.
In a series of recent meetings and publications,
researchers have debated the origin and
significance of Catarina. A crucial question is
this: Was Catarina simply a rare event at the
outlying edge of the normal bell curve of South
Atlantic weather -- just as, for example, Joe
DiMaggio's incredible 56-game hitting streak in
1941 represented an extreme probability in
baseball (an analogy made famous by Stephen Jay
Gould) -- or was Catarina a "threshold" event,
signaling some fundamental and abrupt change of
state in the planet's climate system?
Scientific discussions of environmental change
and global warming have long been haunted by the
specter of nonlinearity. Climate models, like
econometric models, are easiest to build and
understand when they are simple linear
extrapolations of well-quantified past behavior;
when causes maintain a consistent
proportionality to their effects.
But all the major components of global climate
-- air, water, ice, and vegetation -- are
actually nonlinear: At certain thresholds they
can switch from one state of organization to
another, with catastrophic consequences for
species too finely-tuned to the old norms. Until
the early 1990s, however, it was generally
believed that these major climate transitions
took centuries, if not millennia, to accomplish.
Now, thanks to the decoding of subtle signatures
in ice cores and sea-bottom sediments, we know
that global temperatures and ocean circulation
can, under the right circumstances, change
abruptly -- in a decade or even less.
The paradigmatic example is the so-called
"Younger Dryas" event, 12,800 years ago, when an
ice dam collapsed, releasing an immense volume
of meltwater from the shrinking Laurentian
ice-sheet into the Atlantic Ocean via the
instantly-created St. Lawrence River. This
"freshening" of the North Atlantic suppressed
the northward conveyance of warm water by the
Gulf Stream and plunged Europe back into a
thousand-year ice age.
Abrupt switching mechanisms in the climate
system â*“ such as relatively small changes in
ocean salinity -- are augmented by causal loops
that act as amplifiers. Perhaps the most famous
example is sea-ice albedo: The vast expanses of
white, frozen Arctic Ocean ice reflect heat back
into space, thus providing positive feedback for
cooling trends; alternatively, shrinking sea-ice
increases heat absorption, accelerating both its
own further melting and planetary warming.
Thresholds, switches, amplifiers, chaos --
contemporary geophysics assumes that earth
history is inherently revolutionary. This is why
many prominent researchers -- especially those
who study topics like ice-sheet stability and
North Atlantic circulation -- have always had
qualms about the consensus projections of the
Intergovernmental Panel on Climate Change
(IPCC), the world authority on global warming.
In contrast to Bushite flat-Earthers and shills
for the oil industry, their skepticism has been
founded on fears that the IPCC models fail to
adequately allow for catastrophic nonlinearities
like the Younger Dryas. Where other researchers
model the late 21st-century climate that our
children will live with upon the precedents of
the Altithermal (the hottest phase of the
current Holocene period, 8000 years ago) or the
Eemian (the previous, even warmer interglacial
episode, 120,000 years ago), growing numbers of
geophysicists toy with the possibilities of
runaway warming returning the earth to the
torrid chaos of the Paleocene-Eocene Thermal
Maximum (PETM: 55 million years ago) when the
extreme and rapid heating of the oceans led to
massive extinctions.
Dramatic new evidence has emerged recently that
we may be headed, if not back to the dread,
almost inconceivable PETM, then to a much harder
landing than envisioned by the IPCC.
As I flew toward Louisiana and the carnage of
Katrina three weeks ago, I found myself reading
the August 23rd issue of EOS, the newsletter of
the American Geophysical Union. I was pole-axed
by an article entitled "Arctic System on
Trajectory to New, Seasonally Ice-Free State,"
co-authored by 21 scientists from almost as many
universities and research institutes. Even two
days later, walking among the ruins of the Lower
Ninth Ward, I found myself worrying more about
the EOS article than the disaster surrounding me.
The article begins with a recounting of trends
familiar to any reader of the Tuesday science
section of the New York Times: For almost 30
years, Arctic sea ice has been thinning and
shrinking so dramatically that "a summer
ice-free Arctic Ocean within a century is a real
possibility." The scientists, however, add a new
observation -- that this process is probably
irreversible. "Surprisingly, it is difficult to
identify a single feedback mechanism within the
Arctic that has the potency or speed to alter
the system's present course."
An ice-free Arctic Ocean has not existed for at
least one million years and the authors warn
that the Earth is inexorably headed toward a
"super-interglacial" state "outside the envelope
of glacial-interglacial fluctuations that
prevailed during recent Earth history." They
emphasize that within a century global warming
will probably exceed the Eemian temperature
maximum and thus obviate all the models that
have made this their essential scenario. They
also suggest that the total or partial collapse
of the Greenland Ice Sheet is a real possibility
-- an event that would definitely throw a
Younger Dryas wrench into the Gulf Stream.
If they are right, then we are living on the
climate equivalent of a runaway train that is
picking up speed as it passes the stations
marked "Altithermal" and "Eemian." "Outside the
envelope," moreover, means that we are not only
leaving behind the serendipitous climatic
parameters of the Holocene -- the last 10,000
years of mild, warm weather that have favored
the explosive growth of agriculture and urban
civilization -- but also those of the late
Pleistocene that fostered the evolution of Homo
sapiens in eastern Africa.
Other researchers undoubtedly will contest the
extraordinary conclusions of the EOS article and
-- we must hope -- suggest the existence of
countervailing forces to this scenario of an
Arctic albedo catastrophe. But for the time
being, at least, research on global change is
pointing toward worst-case scenarios.
All of this, of course, is a perverse tribute to
industrial capitalism and extractive imperialism
as geological forces so formidable that they
have succeeded in scarcely more than two
centuries -- indeed, mainly in the last fifty
years -- in knocking the earth off its climatic
pedestal and propelling it toward the nonlinear
unknown.
The demon in me wants to say: Party and make
merry. No need now to worry about Kyoto,
recycling your aluminum cans, or using too much
toilet paper, when, soon enough, we'll be
debating how many hunter-gathers can survive in
the scorching deserts of New England or the
tropical forests of the Yukon.
The good parent in me, however, screams: How is
it possible that we can now contemplate with
scientific seriousness whether our children's
children will themselves have children? Let
Exxon answer that in one of their sanctimonious
ads.
Mike Davis is the author of many books including
City of Quartz, Dead Cities and Other Tales, and
the just-published Monster at Our Door, The
Global Threat of Avian Flu (The New Press) as
well as the forthcoming Planet of Slums (Verso).
© 2005 Tom Engelhardt
--
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