William H. Calvin, A Brain for All Seasons: Human Evolution and Abrupt Climate Change (University of Chicago Press, 2002). See also http://WilliamCalvin.com/BrainForAllSeasons/NAcoast.htm.
ISBN 0-226-09201-1 (cloth) GN21.xxx0
Available from amazon.com or University of Chicago Press.
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William H. Calvin
University of Washington
the future is sometimes possible on the short time scales of weather
forecasting, but sensitive dependence on initial conditions makes
long-term predictions iffy. Spotting
trends, and acting to head off disasters, is one of the ways in which
human intelligence improves upon mere physics. So our stories about possible futures are not predictions so
much as scenarios.
Our attitude toward climate change has long been like that of
the driver who cannot stop when his headlights illuminate an obstacle,
because of going too fast. Science
is providing us with somewhat better headlights.
Indeed, it has just told us that global warming has an evil
twin, that there are going to be some missing bridges on that dark
road ahead, not just some bumps but some voids where the comfortable
road drops out from under us.
And it isn’t just a matter of slowing down (though that would
help). We are near the
end of a warm period in
any event; ice ages return even without human influences on climate.
The last warm period abruptly terminated 13,000 years after the
abrupt warming that initiated it 130,000 years ago, and we’ve
already gone 15,000 years from a similar warm-up starting point.
But we may be able to do something to delay an abrupt cooling.
tends to stagger the imagination, immediately conjuring up visions of
terraforming on a science-fiction scale – and so some shake their
heads and say, “Better to fight global warming by consuming less,”
and so forth.
Surprisingly, it may prove possible to prevent flip-flops in
the climate – even by means of low-tech schemes.
Keeping the present climate from falling back into the
cool-and-dry mode will in any case be a lot easier than trying to
reverse such a change after it has occurred.
Were fjord floods causing flushing to fail, because the
downwelling sites were fairly close to the fjords, it is obvious that
we could solve the problem. All
we would need to do is, using
highway-construction amounts of explosives, open a channel through the
dam – and do it before dangerous levels of fresh water build up.
This works only if floods of fresh water prove to be the
problem, because the downwelling sites turn out to be close enough to
the fjords. The jury’s
still out on that one. Timing
could be everything, given the delayed effects from inch-per-second
circulation patterns, but that, too, potentially has a low-tech
solution: build dams
across the major fjord systems and hold back the meltwater at critical
times. Or divert
eastern-Greenland meltwater to the less sensitive north and west
But relying on such simple fixes presumes that you know what
you’re doing. You get
to be an expert in this field only by knowing the data and knowing the
processes, backward and forward.
And I mean that literally:
you have to have computer models that successfully predict the
past before you’ll even think of trusting them to predict the next
fifty years. Before we
become as busy as beavers, we’ll want to try out the dam schemes on
the computer models. That’s
the way you find out the common mistakes, not by experimenting
directly on our one and only global climate.
Fortunately, big parallel computers have proved useful for both global climate modeling and detailed modeling of ocean circulation. They even show the flips. Computer models might not yet be able to predict what will happen if we tamper with downwelling sites, but this problem doesn’t seem insoluble. We need more well-trained people, bigger computers, more coring of the ocean floor and silted-up lakes, more ships to drag instrument packages through the depths, more instrumented buoys to study critical sites in detail, more satellites measuring regional variations in the sea surface, and similarly for studying the atmosphere. Eventually you’d progress to some small-scale trial runs of interventions.
It would be especially nice to see another dozen major groups
of scientists doing climate simulations, discovering the intervention
mistakes as quickly as possible and learning from them.
Medieval cathedral builders learned from their design mistakes
over the centuries, and their undertakings were a far larger drain on
the economic resources and people power of their day than anything yet
discussed for stabilizing the climate in the twenty-first century.
We may not have centuries to spare, but any economy in which
two percent of the population produces all the food, as is the case in
the United States today, has lots of resources and many options for
have learned to bracket the future with alternative scenarios,
each of which captures important features that cluster together, each
of which is compact enough to be seen as a narrative on a human scale.
Three scenarios for the next climatic phase might be called
population crash, cheap fix, and muddling through.
The population-crash scenario is surely the most appalling.
Plummeting crop yields will cause some powerful countries to
try to take over their neighbors or distant lands – if only because
their armies, unpaid and lacking food, will go marauding, both at home
and across the borders. The
better-organized countries will attempt to use their armies, before
they fall apart entirely, to take over countries with significant
remaining resources, driving out or starving their inhabitants if not
using modern weapons to accomplish the same end: eliminating
competitors for the remaining food.
This will be a worldwide problem – and could easily lead to a
Third World War – but Europe's vulnerability is particularly easy to
analyze. The last abrupt
cooling, the Younger Dryas, drastically altered Europe's climate as
far east as Ukraine. Present-day
Europe has more than 650 million people.
It has excellent soils, and largely grows its own food.
It could no longer do so if it lost the extra warming from the
There is another part of the world with the same good soil,
within the same latitudinal band, which we can use for a quick
comparison. Canada lacks
Europe's winter warmth and rainfall; it has, for example, no
equivalent of the North Atlantic Current to preheat its eastbound
weather systems. Canada's
agriculture supports about 28 million people.
If Europe had weather like Canada's, it could feed only one out
of twenty-three present-day Europeans.
Any abrupt switch in climate would also disrupt food-supply
routes. The only reason
that two percent of our population can feed the other 98 percent is
that we have a well-developed system of transportation and middlemen
– but it is not very robust. The
system allows for large urban populations in the best of times, but
not in the case of widespread disruptions.
Natural disasters such as hurricanes and earthquakes are less
troubling than abrupt coolings for two reasons: they're brief (the
recovery period starts the next day) and they're local or regional
(unaffected citizens can come to the assistance of the overwhelmed).
There is, increasingly, international cooperation in response
to catastrophe – but no country is going to be able to rely on a
stored agricultural surplus for even a year, and any country will be
reluctant to give away part of its surplus.
In an abrupt cooling the problem would get worse for decades,
and much of the earth would be affected.
A meteor strike that killed most of the population in a month
would not be as serious as an abrupt cooling that eventually killed
just as many. With the
population crash spread out over a decade, there would be ample
opportunity for civilization's institutions to be torn apart and for
hatreds to build, as armies tried to grab remaining resources simply
to feed the people in their own countries.
The effects of an abrupt cold last for centuries.
This might not be the end of Homo sapiens – written
knowledge and elementary education might well endure – but the world
after such a population crash would certainly be full of despotic
governments that hated their neighbors because of recent atrocities.
Recovery would be very slow.
cheap-fix scenario, such as building or bombing a dam, presumes
that we know enough to prevent trouble, or to nip a developing problem
in the bud. But just as
vaccines and antibiotics presume much knowledge about diseases, their
climatic equivalents presume much knowledge about oceans, atmospheres,
and past climates. Suppose
we had reports that winter salt flushing was confined to certain
areas, that abrupt shifts in the past were associated with localized
flushing failures, and that one computer model after another suggested
a solution that was likely to work even under a wide range of weather
extremes. A quick fix,
such as bombing ice dams, might then be possible.
Although I don't consider this scenario to be the most likely
one, it is possible that solutions could turn out to be cheap and
easy, and that another abrupt cooling isn't inevitable.
Fatalism, in other words, might well be foolish.
muddle-through scenario assumes, again, that we would mobilize
our scientific and technological resources well in advance of any
abrupt cooling problem, but that the solution wouldn't be simple.
Instead we would try one thing after another, creating a
patchwork of solutions that might hold for another few decades,
allowing the search for a better stabilizing mechanism to continue.
We might, for example, anchor bargeloads of
evaporation-enhancing surfactants upwind from critical downwelling
sites, letting winds spread them over the ocean surface all winter,
just to ensure later flushing. We
might try to create a rain shadow, seeding clouds so that they drop
their unsalted water well upwind of a given year's critical flushing
computer simulations will tell us that the only robust solutions are
those that re-create the ocean currents of three million years ago,
before the Isthmus of Panama closed off the express route for
excess-salt disposal. Thus
we might someday dig a wide sea-level Panama Canal in stages,
carefully managing the changeover.
Scenarios ought to capture the stage setting that
precedes the main events, not merely describe major outcomes.
So let me spin a slightly more exaggerated version of our
present know-something-do-nothing state of affairs:
Know Nothing, Do Nothing.
My scenario doesn’t require the short-sighted to be in
charge, only for them to have enough influence to create starvation
budgets for the relevant science agencies, to send recommendations
back for yet another commission report five years hence, and so forth.
In the USA, all it takes is either a know-nothing President or
a do-nothing Congress.
The short-sighted have, after all, dominated at many times
during history. Book
burning and censorship are perhaps the most obvious signs, but
countries have also withdrawn into shells, disdaining foreign
inventions and knowledge in favor of fundamentalist visions of the
good life (recall that Chinese retreat in 1433 from the route to
Europe if you can’t think of modern examples).
of the issues that vex humanity daily – ethnic conflict, arms
escalation, overpopulation, abortion, environmental destruction, and
endemic poverty, to cite several of the most persistent – can be
solved only by integrating knowledge from the natural sciences with
that from the social sciences and the humanities. Only fluency across
the boundaries will provide a clear view of the world as it really is,
not as it appears through the lens of ideology
and religious dogma, or as a myopic response solely to immediate
need. Yet the vast majority
of our political leaders are trained primarily or exclusively in
the social sciences and the humanities, and have little or no knowledge
of the natural sciences. The
same is true of public intellectuals, columnists, media interrogators,
and think-tank gurus. The best of their analyses are careful and
responsible, and sometimes correct, but
the substantive base of their wisdom is fragmented and lopsided.
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All of my books are on the web.
The six out-of-print books
are again available via Authors Guild reprint editions,