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ABRUPT CLIMATE CHANGE
A Scenario That Will Rock Your
World.
An address to Australian Taxation Office executives
Brisbane
28 June 2004
“At the moment, we are an ignorant species, flummoxed by
the puzzles of who we are, where we came from, and what we are for. It is a
gamble to bet on science for moving ahead, but it is, in my view, the only
game in town.”
-
Lewis Thomas (1979)
“The stories scientists tell us are not simply bedtime
tales. They place us in the world, and they can force us to alter the way we
think and what we do.”
-
Thomas Levenson (1989)
“One of the most shocking scientific realizations of all
time has slowly been dawning on us: the earth’s climate does great
flip-flops every few thousand years, and with breathtaking speed.”
- William Calvin (2002)
Introduction: Big History
Everything we think of as ‘world history’ has occurred in the past five
thousand years. Very few of us have anything like a clear grasp even of that
time frame. This evening, I invite you to consider a radically longer
time frame - the time frame of natural history. In particular, I
want to draw your attention to a couple of extraordinary characteristics of
natural history, which put our own history in a very different context from
how we usually think about it.
In his path-breaking
study of the origins of vision, 530 million years ago, Australian biologist
Andrew Parker remarked, in 2003: “We think of ancient history as perhaps a
couple of thousand years ago. Ten thousand years would be extremely
difficult to conceptualise, a hundred thousand, let alone a million,
inconceivable. So hundreds of millions of years of evolution are way beyond
the realms of the most vivid human imagination.” Yet it is tens and hundreds
of thousands, even many millions of years I want you to ponder: the kind of
time frame that David Christian, in his marvelous new geo-history, Maps
of Time, calls ‘big history’
These vistas of time
have only been opened up, by geologists and palaeontologists, over the past
170 years, going back to the work of Charles Lyell in the 1830s and Charles
Darwin in the 1850s. The really extended understanding of the age of the
earth and the evolution of life on it has only been done in the past half
century, however, since the general acceptance of the theory of plate
tectonics in the 1960s and punctuated equilibrium in the 1970s. But it is
very recent investigations into ancient climates on which I want to focus
your attention. The breakthroughs there have occurred only in the past ten
to twenty years; indeed, mostly in the last five.
There has, of course,
been much debate in recent years about greenhouse warming and the
possibility that our species is overheating the planet. But it is not
anthropogenic overheating that I want to talk to you about. It is the long
term patterns of climate change which antedate our kind and which have only
in very recent years started to become clear to specialists. Those patterns
take an especially significant and startling form over the past million
years and I shall, shortly, zero in even more narrowly on the last 20,000
years – the years coinciding with the historic rise of our species. But
first, let me illustrate the very long term patterns.
The Earth’s Climate: From the
Hadean to the Holocene.
Here is a graph of the
earth’s climate since the planet was formed 4.6 billion years ago. It is a
slightly modified version of a graph in David Christian's Big History
(p. 132), as are the next few graphs. The long period from the planet’s
formation through the Pre-Cambrian was hot, but cooling. It is not to scale.
The part to note most specifically is the last billion years, in which there
is a roller-coaster of cooling and warming, with average global temperatures
oscillating between about 26 degrees and 12 degrees Celsius. Below 14
degrees, you get glaciation. You will observe that there have been long
periods of glaciation and long eras of warmth – greenhouse eras.
Now, look at a much
shorter time period – the last 600 million years. Here are all the great
geological epochs during which there have been complex life forms on earth,
punctuated by a series of mass extinctions. The best known of these, indeed
the only one that could be said to have penetrated popular culture, is the
end Cretaceous mass extinction, in which the dinosaurs disappeared from the
face of the earth. The thing to observe here, however, is the wavy line
graphing average global temperatures. You can see that it rises to
greenhouse levels three times and drops below the glaciation line twice.
What you cannot see in
detail in either of these graphs is the trend during the Tertiary and
Quaternary epochs, the last sixty five million years, during which apes and
hominids evolved. Here it is:
What is plainly observable here is
the general downward trend in average global temperatures from 24 to 15
degrees, – that is to say, a marked cooling of the world’s climate, since
the end of the Cretaceous. This is the epoch of the mammals. Hominids, of
which we are the only remaining kind, appear only in the Pliocene, which is
to say the last ten million years and especially in its last phase, the
Pleistocene, starting two million years ago. But looking at this graph, you
cannot discern what has been happening in that period in any detail.
Let’s look, therefore,
at the Pleistocene:
Now we start to cut to the chase.
You will see, at a glance, that what looked before to be a smooth curve is
actually a very bumpy one, when viewed in detail. Indeed, the closer you get
to the present, the bumpier it gets. With the mean temperature hovering
around 15 degrees, but the glaciation point being 14 degrees, the planet has
been slipping into and out of ice ages for over a million years, with more
and sharper fluctuations in the most recent half million.
These fluctuations were
unknown until a few decades ago, but it has been ascertained that they
coincide with and are likely caused by variations in the earth’s orbital
cycle around the sun and perturbations in the axis of its rotation. Over a
period of 100,000 years, the earth’s orbit around the sun shifts from
roughly round to markedly elliptical. Every 41,000 years, the tilt of the
earth’s rotational axis shifts through an arc of perhaps 2 degrees and every
19,000 to 23,000 years there is a wobbling of the earth on it axis, which
causes the time when the earth is closest to the sun to shift from northern
summer to southern summer.
These are known as
Milankovitch Cycles, after a Yugoslavian mathematician who predicted them,
based on his knowledge of the solar system, decades before they were
actually detected. So, the bumpy line in the Pleistocene registers the
Milankovitch Cycles, as they impacted earth while the climate was slowly
cooling for other reasons. This is the epoch of the ice ages and it has
played a profound role in the biological evolution of our species. What it
shows is that long ice ages, lasting around 90,000 years, have been
interspersed with relatively short inter-glacial ages, lasting around 10,000
years.
So, against this deep
background, I invite you to consider a fundamental reality, which had
entirely escaped our species until very, very recently. Everything we
think of as world history, from the beginnings of agriculture to the
beginnings of space exploration, has taken place in an inter-glacial age,
which has already lasted about 15,000 years; far longer than inter-glacials
normally last. The ice ages are not over and when the ice returns, many of
those zones in which our huge populations and intensive agricultures exist
will be frozen over, as they have been again and again over the past two and
a half million years.
The Dansgaard-Oeschger Cycle.
That, surely, is food
for thought. It is not the end of the matter, though. For during the last
couple of decades, oceanographers and geochemists have been investigating
yet another pattern of climate fluctuations, which takes place alongside
the larger pattern of glacials and inter-glacials. This is a pattern called
the Dansgaard-Oeschger or D-O Cycle, named after Willi Dansgaard and Hans
Oeschger, who did much of the pioneering work on it, in the 1980s. It
consists of frequent, very rapid climate flips, centering in the North
Atlantic, which have drastically altered global climate every few thousand
years, on average, throughout the Pleistocene.
Here is a graph of the
D-O Cycle over the past million years.
You will notice that this graph
starts from the right hand side, not the left, so that the far left
represents the present. The line is extremely jagged and every spike in it
represents a D-O event, that is to say, a climate flip of varying degrees of
severity, in which the climate of Europe changes suddenly, from warm and wet
to cool and dry, with corresponding changes elsewhere; for example, massive
droughts in Africa and eastern Eurasia.
The high points on the
chart, of which there are ten or a dozen, are the inter-glacials. Each is
followed, as you can see, by a sharp cooling and a long descent into
glaciation. The relatively extended inter-glacial labeled on the graph is
the one before our own, known to climate scientists in Europe as the Eemian.
It lasted for around 13,000 years. Let me pause, at this point, to remark
that it is, surely, completely extraordinary that human scientific endeavor
has been able to reconstruct this climate record. It is one of the countless
wonders of modern science and it should fill us with awe. I invite you, just
for a moment, to reflect on the staggering achievement that all these graphs
represent.
Now we come to the graph
that I want to imprint most firmly in your memories and imaginations:
This graph moves
from left to right, unlike the preceding one. It covers just the last 20,000
years. This is our time. I began by stating that all of what we
usually think of as ‘world history’ has occurred in the last five thousand
years – the millennia since writing was invented. Those five thousand years
are covered by the extreme right hand column in the graph. It is, for the
moment, the columns to its left that I want you to look at closely.
The leftmost column
shows the last millennia of the most recent ice age. Around 14,000 years
ago, there is a very sharp upturn, followed by a jagged descent and then a
deep, cold trough, from about 12,700 years ago until about 11,400 years ago.
This cold trough is known as the Younger Dryas. It was a climate
flip that tossed a Europe which had begun to emerge from glaciation, back
into the freezer for some 1,300 years. Then, with equally startling
suddenness, the climate flipped again and things warmed up dramatically.
What had happened? A standard D-O event. It changed Europe’s climate from
something like its current condition to Siberian conditions within a decade;
then, 1,300 years later, it flipped back again.
Think about that.
There has been nothing remotely like this in historic time. If the same
thing was to happen now, the consequences for human civilization would be
all but unimaginable. And here’s the thing: the fact that more than 11,000
years have passed since this last major D-O is anomalous, in the
context of what we can see in the longer term patterns throughout the
Pleistocene. We do not know why things have remained warm for so long and
we have no reason to believe that the long term pattern has changed in any
fundamental way.
As a measure of how
disastrous a major climate flip would be, consider that, 8,200 years ago,
there was a much smaller and briefer cooling. It is marked on the chart.
This downturn lasted about a century, but it caused major perturbations and
would have a catastrophic impact were something like it to recur in the 21st
century. You can gain some dim appreciation of the scale of impacts I am
talking about here, simply by looking at the even smaller bumps in the
rightward half of the graph and considering that the little peak labeled
‘Medieval Warm Period’ made it possible for the Vikings to settle Greenland,
but, when it passed, they were driven out by the cold.
How Credible is the Abrupt
Climate Change Hypothesis?.
If you’re like me, you
will be pretty stunned by all this. I want, therefore, to show you that this
is not some crazy or irresponsible fantasy, invented by some crackpot. It is
credible and we should take it seriously. I came across the concept of
abrupt climate change for the first time in a book called A Brain For All
Seasons, by William Calvin, which I’d bought because of my interest in
the evolution of the human mind. In that book, Calvin advanced the thesis
that our brains, our mental abilities, evolved as they did, over the past
two million years or so, largely in order to cope with the challenges posed
by climate flips.
Calvin is a
neurophysiologist, not a climate scientist, but his account of the case was
so compelling that it quickened my interest in climate change in a way that
public debates about greenhouse gas emissions and global warming had never
done. I began, therefore, to look into the science of climate change, if
only to see whether his account of the matter could be relied upon. What I
discovered was so fascinating, not to say unsettling, that it quite
transformed the way I think about the natural world. That is why I was so
keen to share the matter with you this evening.
Here is Calvin’s own
account of how he first learned of the matter of abrupt climate change, from
Swiss geophysicist Hans Oeschger, twenty years ago:
“…it
was long suspected that orbital factors weren’t the whole story, as the
southern hemisphere ice sheets melted back at the same time as the northern
ones. Why should ice sheets in the Andes and New Zealand melt when the
closest approach bonus was in their winter time? They should have been out
of phase with the northern one, but they were in phase, synchronized by
something.
The
other thing that made climate scientists suspect that it wasn’t so simple
was a wild flower, white with a yellow centre, of the rose family, called
Dryas octopetala. It is cold adapted and is
found on the tundra – not among shrubs and pine trees. Well, a
century ago, Dryas pollen turned up in cores of a lake bed in
Denmark, above a layer of trees, at a depth now
dated back to about 12,000 years. A return to cold made no sense then,
according to the Milankovitch orbital view…There should have been pine seeds
in those cores, not the pollen of a tundra flower…
…But
the pros knew about such anomalies as the Younger Dryas and…the Greenland
[ice] cores were starting to show some puzzling results, as the Danish
researcher Willi Dansgaard and his colleagues reported, in 1982. I first
heard of the abruptness, per se, in 1984, when the Swiss geophysicist Hans
Oeschger gave a talk in Seattle. The time calibration on one of his slides
prompted me to ask him afterward about just how quickly temperature had
changed.
Oh,
he said, the big drop took just a few years. The enormity of such a whiplash
caused me to assume that we were having some language difficulties and so I
persisted, asking ‘Just a few decades?’ No,
no, he replied, merely a few years..” (Calvin, 2002, pp. 215-17)
In short, Calvin has not made up any
of the story about abrupt climate change. He has learned it from those most
closely engaged in doing the research. Twenty years on from that encounter
with Oeschger, Calvin himself gave a talk at Westminster College, Salt Lake
City, in March this year, called ‘When Climate Staggers: Civilization’s
Vulnerability to Sudden Change’.
In those intervening two
decades, the work on abrupt climate change has been carried forward by
scientists at numerous research institutes across the world. Prominent among
them have been the Lamont-Doherty Earth Observatory and the Woods Hole
Oceanographic Institution, both at Columbia University. The doyen of the
Lamont-Doherty team, which numbers some 200 scientists, is Wallace Smith
Broecker. He was awarded the National Medal of Science in 1996 for his work
and the Tyler Prize for Environmental Science Achievement in 2002, along
with Liu Tungsheng of the Chinese Academy of Sciences, a fellow pioneer in
the study of palaeoclimate.
Broecker’s articles and
those of many other specialists on the subject of abrupt climate change,
have appeared in the major scientific journals, Science, Nature,
Scientific American, Paleooceanography, Quaternary Research, Earth Sciences
Review and Oceanography. But until just a very few years ago, the
message was simply not reaching the general educated public, or even the
wider scientific community. It was Calvin who broke the ice, as it were,
with an essay in The Atlantic Monthly, in 1997, called ‘The Great
Climate Flip-Flop’.
He wrote that piece, he says,
because “it was a scandal that it had gone largely unreported for ten years,
despite all the news-feature stories in Science and Nature.”
(Calvin 2002, p. 299).
The
appearance of Calvin’s essay in The Atlantic Monthly in 1997,
coincided with the publication in Science (Vol. 278, No. 5343, pp.
1582-87) of a major paper by Wallace Broecker, titled ‘Thermohaline
Circulation, the Achilles Heel of Our Climate System: Will Man-Made CO2
Upset the Current Balance?’ I shall come back to that essay, because it
bears on a central bone of contention in current discussions of climate
change scenarios – to wit, will anthropogenic global warming
actually trigger a D-O event?
As some
of you will be aware, this specific scenario is the subject of the Hollywood
disaster movie, The Day After Tomorrow, currently screening in
cinemas around the world. Hollywood, unfortunately, has made an egregious
mess of the matter. The movie makers just could not resist making absurd
claims and constructing a melodramatic, politically correct plot. Taken
together, these make for a film that is annoyingly bad. But I’ll come back
to that. Let me, first, finish what I was saying about the scientific
credibility of the basic picture.
While Broecker’s
articles kept appearing in the serious journals, Richard B. Alley, Evan Pugh
Professor of Geosciences at Pennsylvania State University, followed William
Calvin’s lead, by writing a full length book about abrupt climate change,
for a general readership. It is called The Two Mile Time Machine: Ice
Cores, Abrupt Climate Change and Our Future and was published by
Princeton University Press in 2000. It won the 2001 Phi Beta Kappa Award in
Science and I recommend it to any of you who would like to read more deeply
into the subject.
Alley went on to chair a
committee under the auspices of the National Academy of Science, in the
United States, which produced a full length report in 2002, called Abrupt
Climate Change: Inevitable Surprises. Based on this report, Bob
Gagosian, director of the Woods Hole Oceanographic Institution,
delivered a presentation to the
Davos Forum, in January 2003, under the title ‘Abrupt Climate Change: Should
We Be Worried?’ I want to quote his opening remarks to you, because they
underscore the seriousness with which this matter is viewed at the highest
levels of the scientific research community.
Gagosian told the Davos
Forum:
“Most of the studies and debates
on potential climate change, along with its ecological and economic impacts,
have focused on the ongoing buildup of industrial greenhouse gases in the
atmosphere and a gradual increase in global
temperatures. This line of thinking, however, fails to consider another
potentially disruptive climate scenario. It ignores recent and rapidly
advancing evidence that Earth’s climate repeatedly has shifted abruptly
and dramatically, in the past and is capable of doing so in the
future…
…This new paradigm of abrupt
climate change has been well established over the last decade by research of
ocean, earth and atmosphere scientists at many institutions worldwide. But
the concept remains little known and scarcely appreciated in the wider
community of scientists, economists, policy makers and business leaders.
Thus, world leaders may be planning for climate scenarios of global warming
that are opposite to what might actually occur.”
He added:
“It is important to clarify that
we are not contemplating a situation of
either abrupt cooling or warming. Rather, abrupt regional cooling and
gradual global warming can unfold simultaneously. Indeed, greenhouse warming
is a destabilizing factor that makes abrupt climate change more probable.”
As he explained and as is set out in
greater detail in the NAS report, the interaction could occur because abrupt
climate change is a non-linear event, which occurs when the climate system
crosses a certain threshold – and global warming could force it across the
best documented such threshold in the climate system.
That threshold operates
in what Broecker, in the 1997 article I referred to earlier, described as
the Achilles Heel of the climate system. As he explained, the world’s oceans
run on a sort of conveyor belt, which carries warm waters from the tropics
to cooler regions and cooler waters back. In the unique case of the Atlantic
Ocean, the warm current, known as the Gulf Stream, carries an enormous
amount of tropical warmth to higher latitudes, greatly moderating the
otherwise cold climate of northern Europe. He went on to write:
“The record contained in ice and
sediment indicates that this current has not run steadily [throughout the
Pleistocene] but [has] jumped from one mode of operation to another. The
changes in climate associated with these jumps have now been shown to be
large, abrupt and global. Although the exact linkages that promote such
climate changes have yet to be discovered, a case can be made that their
roots must lie in the ocean’s large-scale thermohaline
circulation…Variations in the conditions governing the density of high
latitude surface waters can lead to abrupt reorganizations of the ocean’s
circulation. The surprise revealed to us by the climatic record is the
extent, rapidity and magnitude of these atmospheric changes.”
Broecker believed that the most
common trigger for one of these non-linear switches was the sudden release
into the North Atlantic of large quantities of fresh water, coincident with
what is called a Heinrich event – the bursting of a huge natural lake or dam
or the breaking off of a massive ice sheet from Greenland or the Hudson Bay
area. His concern, as you will probably have guessed, is that global warming
could bring about a Heinrich event and thereby force the thermohaline system
across the threshold to a D-O event.
What drives this vast conveyor that Broecker is talking about? The answer,
interestingly, is salt. Bob Gagosian explained the mechanism in very clear
and simple terms at Davos. This is what he said:
“For
a variety of reasons, North Atlantic waters are relatively salty compared
with other parts of the world ocean. Salty water is denser than fresh water.
Cold water is denser than warm water. When the warm, salty waters of the
North Atlantic release heat to the atmosphere, they become colder and begin
to sink.
In
the seas that ring the northern fringe of the Atlantic – the Labrador,
Irminger and Greenland Seas – the ocean releases large amounts of heat to
the atmosphere and then a great volume of cold, salty water sinks to the
abyss. This water flows slowly, at great depths, into the South Atlantic and
eventually throughout the world’s oceans.
Thus,
the North Atlantic is the source of the deep limb of the Ocean Conveyor. The
plunge of this great mass of cold, salty water propels the global ocean’s
conveyor-like circulation system. It also helps draw warm, salty tropical
surface waters northward to replace the sinking waters. This process is
called ‘thermohaline circulation’, from the Greek words ‘thermos’ (heat) and
‘halos’ (salt).
If
cold, salty North Atlantic waters did not sink, a primary force driving
ocean circulation could slacken and cease. Existing currents could weaken or
be redirected. The resulting reorganization of the ocean’s circulation would
reconfigure Earth’s climate patterns.”
As Gagosian already knew, when he
delivered this speech, a leading article in Nature, in April 2002,
had pointed out that the subpolar seas bordering on the North Atlantic have,
in fact, become noticeably less salty over the past forty years and
especially in the past decade.
In other words, the available
evidence suggests that we could be somewhere in the vicinity of the
threshold for a non-linear climate flip. We simply don’t know enough to
be sure. Nor do we know how close you can get to such a threshold and still
be able to do anything to pull back.
Hollywood and the Nature of the
Danger.
Having written an essay
on abrupt climate change last August, before I was even aware Roland
Emmerich’s Hollywood film about the matter was in the works, I was intrigued
when it was released. I went to see it with an old school friend. We were
profoundly disappointed with it. It seemed designed to entertain or scare
children, but was wholly lacking in both scientific and social realism.
The film opens by
drawing attention to ocean monitoring in the North Atlantic Seas. Good, I
thought, they’ve done their basic homework. Unhappily, it is pretty much all
down hill from there. The film has things happen on a scale and at a speed
which are totally unrealistic. Whether this makes good cinema is moot, but
it is such bad science that it can only confuse a general audience which
needs to be soberly enlightened.
The film has almost the
whole northern hemisphere freeze over within days or weeks. This is flatly
impossible. The process takes many years to reach a threshold of the kind I
have described and, once the threshold has been crossed, a few years to a
decade to radically change the climate. Isn’t this dramatic enough for
Hollywood? Why make things ridiculous?
The film
has temperatures in the continental United States dropping by tens of
degrees in seconds, as a huge hurricane sweeps in from the Arctic at minus
150 degrees Fahrenheit. But hurricanes cannot develop in the cold. They are
tropical phenomena. And the coldest temperature ever recorded on earth, at
Vostok, in Antarctica, is minus 128.6 degrees Fahrenheit. One could go on,
but there is little point.
The social
implausibility of the film is equally egregious. Once the full impact of the
catastrophe has hit, the film has the United States government evacuate tens
of millions of people in a safe and orderly fashion within days, to what Tom
Lehrer once called ‘that magic and romantic land south of the border, sunny
Mexico.’ Inexplicably, they all wind up in well constructed refugee camps
and everyone seems to be behaving at their best, as the US president goes on
global television – itself somehow undisturbed by the icing over of most of
the northern hemisphere – and confesses that we were wrong to think we could
go on releasing greenhouse gases into the atmosphere without upsetting
nature’s delicate equilibrium.
As they say in that part
of the States the film ices, “Puh-leez!” Such abuses of both science and
common sense made the film a tempting target for climate change skeptics.
One of the best known of these is Bjorn Lomborg:
director of Copenhagen Consensus and
of Denmark’s national Environmental Assessment Institute. Lomborg became a
global figure in 2001, with the publication by Cambridge University Press of
his best selling book, The Skeptical Environmentalist. On 27 May this
year, as the Emmerich film opened in cinemas here, he had an opinion piece
in The Australian headed ‘Entertaining discredited ideas of a
climatic catastrophe’.
Lomborg wrote in
response not only to the film, but to a report prepared late last year for
the Pentagon’s Office of Net Estimates, in which abrupt climate change
within the next two decades was described as a scenario for which the
American government needed to be prepared. He wrote that the scenario
outlined in the Pentagon study had been “thoroughly debunked” by reviewers
in Science and Nature and that halting the Gulf Stream would
be impossible, so that “it is safe to say that global warming will not lead
to a new ice age.”
I was fascinated by
these claims, since it is precisely Science and Nature that
have published most of the scientific research showing that abrupt climate
change could occur and that the pattern of such changes in the past
is linked to recurrent halting of the Gulf Stream. Have the
specialists abruptly changed their minds? I wondered. I went looking for the
reviews Lomborg alludes to, eager to learn what had happened. To my
amazement, I could not find any such thing in either magazine.
I emailed Lomborg and
his colleagues in Copenagen, asking could they point me to the reviews in
question, since I had been unable to find them. I got no response. I
emailed Bob Gagosian, in New York, asking had he come across anything
matching this description and showing that the work of Wally Broecker and so
many others had been “thoroughly debunked”. He informed me that he has not,
as of last week, come across any such thing.
Now, I don’t want to
give you the impression that I think Lomborg is as unreliable as Roland
Emmerich. Lomborg and his colleagues have done a lot of work to rethink the
state of the global environment and have challenged quite a number of
widespread fears and assumptions about environmental deterioration or
man-made environmental damage. I respect that work.
I went
looking for the reviews and the debunking he referred to just because I do
take him seriously and am open to the possibility that somehow Wally
Broecker and his many colleagues have gotten the matter wrong. I have gone
to considerable lengths this evening to show you the nature of their
reasoning, because I fear that too many people will pick up on remarks such
as Lomborg’s and dismiss the science of abrupt climate change, along with
the Hollywood film. That, I believe, would be a serious error.
Lomborg had a perfectly rational aim in writing what he did, though he
may have unintentionally misread what scientists are saying on the subject.
He wrote, “The problem is that if we overestimate the risk that
climate change poses, then we will pay less attention to the other
challenges facing humanity…Because we cannot do everything, we need sound
reasoning and high quality information to defeat the hysteria of Hollywood.”
He is
certainly correct in saying that we should rationally seek to determine
where to allocate our priorities and resources, given the range of
challenges we face. He is also correct to call for sound reasoning and high
quality information, as against the hysteria of Hollywood. Where he seems to
me to miss the boat is in asserting that the abrupt climate change scenario
has been “thoroughly debunked”, i.e. that it is based on hysteria and not
on sound reasoning, or high quality information.
There is
nothing hysterical about Wally Broecker or Bob Gagosian or Richard Alley or
William Calvin. Nor is there any reason that I am aware of for seeing their
reasoning abilities or published work as being inferior to those of Bjorn
Lomborg. In ridiculing the Emmerich film, Lomborg was knocking down a straw
man. By not naming the authors of the articles in Science or
Nature that supposedly “thoroughly debunked” the Pentagon scenario, or
supplying their dates, he made it frustratingly difficult to check his
claims.
By not
acknowledging the enormous amount of reputable scientific work that has gone
into developing our understanding of abrupt climate change, he left himself
open to the counter claim that he is merely ignorant of the matter. Had he
wanted to tackle the case at a serious level, he would have done better to
have critically evaluated the claims made by William Calvin, in his March
2004 Adamson Lecture at Westminster College, or Bob Gagosian’s January 2003
address to the Davos Forum. Let me, at least, indicate how this might be
done, before concluding my remarks.
Circumspection and Critical
Analysis.
In his Adamson Lecture, Calvin was at pains to make clear
that we have only in the past decade or so learned that abrupt climate
change occurs at all. His use of the pronoun ‘we’ is generous, for of course
the overwhelming majority of human beings have not the foggiest idea about
all this. What he poses is the question, how do we come to terms with
what we have been learning in this regard?
What has been pieced
together about climate history indicates that the Earth’s climate is
bimodal. It oscillates between ice ages and inter-glacials on a long
sinusoidal curve (the Milankovitch Cycles), but along that same curve it
oscillates at much higher frequency and with abrupt switches between
warm/wet and cool/dry modes (the Dansgaard/Oeschger Cycle), which appear to
be causally linked to periodic irruptions of fresh water into the sub-arctic
seas of the North Atlantic (Heinrich events).
These abrupt shifts
are such that they would allow almost no reaction time for a complex system
such as human civilization. This is the real thrust of Calvin’s lecture,
as it was of the Pentagon’s scenario paper. When the last D-O, the Younger
Dryas, occurred, human beings were few, non-agricultural and relatively
mobile. That had been the case all the way back through such shifts across
the Pleistocene. Now, however, we number billions, overwhelmingly dependent
on complex farming, energy, transport and governance systems.
Calvin points out that,
under Younger Dryas conditions, Europe would become, within a few years to a
decade, like Canada or Siberia. Canada supports 28 million people, Siberia
about 8 million. Europe currently supports 650 million, overwhelmingly
because of the temperate climate it enjoys. His challenge to his audience
was to consider the possibility that, in Europe alone, the onset of a D-O
flip could cause the death of at least 600 million people, by cold,
starvation, disease and chaotic violence, within a decade. And there would
be no recovery, for the climate would remain cool and dry, in all
probability, for centuries.
Why this was not
dramatic enough for Roland Emmerich and the Hollywood movie moguls is
completely beyond me. But what is it rational to think, or say, or do, in
response to such a dire scenario? To reject it out of hand? I suggest not.
To panic and throw up our hands? I think not. To assume it to be a sure
prediction and call for revolutionary changes to our civilization? I suggest
not. What, then? To summon the mental discipline required to examine it
closely, test the assumptions and the reasoning involved, identify where we
need to know more, then model various possible ways of heading off, or
preparing for variations on the scenario.
It is surely worth
recalling, in this context, that we have seen at least two comparable
long term scenarios over the past 150 years, in which initial data sets and
projections turned out to be erroneous or inadequate in a number of ways.
The first was the left-wing analysis of industrial capitalism, most
famously that by Karl Marx:
which described it as bound to
produce growing immiseration of the working classes and consequent radical
revolution, following which a command economy would provide freedom and
plenty for all people. I do not need to remind this audience, I am sure, how
thoroughly debunked this scenario now stands.
The second was the
over-population model, most famously developed by Paul Erhlich, at Stanford
University, according to which an exploding human population would cause a
breakdown of industrial and technological civilization in the late twentieth
century, with resources being used up, agriculture failing and hundreds of
millions of people dying in gigantic famines. The Club of Rome took up the
cry, as did many others. Just a generation on, never having seen the
collapse predicted by Erhlich, we are seeing very different demographic
trends emerging globally, even the possibility, in mid-century, of a kind of
population implosion. This is the context in which Bjorn Lomborg and
others have been urging that we rethink how we think about environmental
challenges.
If, therefore, we were
to respond to the abrupt climate change scenario with uncritical alarm or
calls for poorly thought through social and economic upheavals, we would
quite possibly be turning ourselves into latter day Leninists or population
bombers, if you’ll pardon the expression in present geopolitical
circumstances. This would ill serve us. Rather, we need to remain, if I may
put it thus, very cool headed. We need, as it were, to chill out
and make as certain as possible that we are both understanding the past
correctly and weighing the variables in future scenarios scrupulously.
Concluding Remarks: Consilience
and Resilence.
The changes in the human
world over the past century or two have been breathtaking, by any measure.
The advances in our knowledge of natural phenomena and of our own past, the
developments in our technologies and methods of inquiry have been truly
staggering. What we have just learned about long term patterns of climate
change belongs in this context. So, I suggest, does the fact that most of us
suffer from a chronic inability to take it all in, to make integrated sense
of the world.
More than most things
you might read about, though, I think the possibility of abrupt climate
change ought to rock your world. We occasionally talk about thinking outside
the box, or outside the square. Well, this scenario really is outside
the square, as far as most of our comfortable and long-settled assumptions
are concerned. That, more than the calamitous possibilities Calvin points
to, are what make it so thought-provoking, in my opinion.
I want,
therefore, to conclude with just a few remarks about thinking outside the
square and the kind of thinking that the abrupt climate change
hypothesis entails. For, you see, all of us, as professionals and as
inference-drawing, meaning-making human beings, are faced daily by having to
assimilate information of various kinds. For the most part, we do so by
screening out what does not compute and interpreting the rest in terms of
what we already take to be the case. How else could we operate? Yet,
every so often, we encounter information that does not compute in terms of
our existing assumptions, but is not easily screened out. That’s when there
is an opportunity for deeper thinking.
Such
deeper thinking occurs when we recognize the incompatibility of what we have
encountered with what we already believe and set about making explicit what
is at stake, and why and then determining whether we should alter our
beliefs. In simple, everyday ways, you might say, we do this all the time.
What I’m talking about here, though, is the sort of case in which something
quite fundamental confronts us; something which we cannot deal with easily,
or on the run.
This
requires taking quite deliberate steps to re-examine the way we are thinking
about the issue in question. That is strenuous work and does not come
naturally. Nor are we equipped to do it just any day of the week, as it
were. We don’t know how to do it, for the most part. We cannot
readily see what specific things it would be best to rethink. We encounter
resistance, not only in ourselves and our own habits of thought, but in the
prejudices of those around us and in institutionalized practices rooted in
the very assumptions that we might seek to challenge.
Peter
Senge made the term ‘learning organization’ current, but what challenges
of the most fundamental kind require is pro-active thinking organizations
– organizations that do not simply learn rapidly when they encounter
challenges, but seek actively to anticipate challenges and to build
resilience into their systems and practices, awareness and flexibility into
their most fundamental, governing assumptions. You only have to
contemplate the world of religion and politics to realize that these things
are devilishly difficult to achieve, much less maintain. Yet they are what
the world we have created for ourselves increasingly demands.
William
Calvin concluded his address, in March, by observing that we would do well
to begin pro-actively exploring how we can build much greater resilience
into the physical and infrastructural underpinnings of our civilization,
with a view to surviving future climate shifts; even abrupt and massive
ones. Such an ambitious technological and social project could only
proceed on the basis of cognitive habits and practices of critical thinking
and rational dispute resolution which are decidedly lacking at present.
Yet the idea is bracing and I, for one, would much sooner embrace that
challenge than settle for either complacency or hysteria.
We live
in extraordinary times. Both for better and for worse, the possibilities
that loom before us are awesome. We have looked this evening at a
possibility of catastrophe on a scale that beggars both belief and
imagination. But simultaneously, we can see possibilities of technological
breakthroughs and even social renovation of quite stunning kinds. How can we
reconcile all these things? Keep our balance? Avoid both panic and
irrational exuberance?
Your
responses to those questions will vary. Let me, however, offer a single
word as a kind of Ariadne’s thread that might guide you through the
labyrinth. The word is consilience. The biologist Edward
O. Wilson uses it to describe a new inter-disciplinary integration of what
we know and how we think. He called for the development of “fluency across
the boundaries” between the humanities and natural sciences that would
“provide a clear view of the world as it really is.” There is a task for a
whole new generation of Renaissance scholars!
I see
the history of climate and the scientific analyses of climate change as
a way into this integrated view of the world and our place in it. For
this history - big history, in David Christian’s terminology – puts us and
our pretensions in deep perspective and shows us our world natural and
whole. It shows us how very narrow all human myths and ideologies have
been up until now and draws us into a future with a vast horizon.
The
possibility of abrupt climate change should wonderfully concentrate our
minds. For it tells us that our future is anything but assured and that our
modern assumptions about endless material progress and boundless growth may
rest on more fragile foundations than anyone had ever realized. That, I
suggest, is salutary, since we are all too prone to complacency and
arrogance. It challenges us to rethink our worldviews and beliefs about the
future, starting from a whole new level of awareness about the deep past. It
challenges us to think and think again and keep thinking about the day
after tomorrow.
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