Melting Away


Mike Davis


thenation.com
posted October 7, 2005
http://www.thenation.com/doc/20051024/davis


This essay is republished with permission from
TomDispatch.com.


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 downlinked 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 fifty-six-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--that is, 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--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 levels increase heat absorption,
accelerating both 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, these researchers base their skepticism
on fears that the IPCC models fail to adequately allow
for catastrophic nonlinearities like the Younger Dryas.
Where other researchers model the late-twenty-first-
century climate that our children will live with upon
the precedents of the Altithermal (the hottest phase of
the current Holocene period, 8,000 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 23 issue of EOS, the newsletter of
the American Geophysical Union. I was pole-axed by an
article titled "Arctic System on Trajectory to New,
Seasonally Ice-Free State," co-authored by twenty-one
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 thirty 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 1
million years; 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 maximum Eemian
temperature 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-gatherers 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 ExxonMobil answer that in
one of its 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).
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