Q.&A. with: Richard Alley
by ED HUNT
I've been reading Dr. Richard Alley's book The Two Mile Time Machine for
the past few days now and must admit that this area of research is
something I've been telling folks about for the past few years. I
interviewed Ed Brook at Washington State University in 1998 on the
subject of ice cores and rapid climate change. Ever since, I've been
plaguing discussions of global warming with talk of rapid climate change,
ocean conveyor belts and a possible return to climate instability. Thus,
I was glad to have the opportunity to pose a few questions to Dr. Alley
this week by email.
TIDEPOOL: People are finally starting to get worried about the effects of
a gradual, linear increase in global temperatures over the next century.
What kind of reaction do you get when you talk about possible ice ages,
or climate variability within the period of just a few years?
ALLEY: Rapid changes are harder for ecosystems and societies to deal with
than are gradual changes, as you well know. If we continue to force the
climate to change, the slow, gradual changes that most people think about
would be the easiest for us to handle.
I'd love to get inside the heads of people and learn how they respond to
the possibility of big, weird, perhaps scary changes. (I'd love to learn
how the respond to lots of other things, too!) My guess is that people
range from worry, to considering the scientists to be weirdos.
TIDEPOOL: In bringing these ideas of complex climate machines and rapid
climate "flips" to the public's attention, have you found a receptive
audience? Or have people had trouble wrapping them minds around what you
ALLEY: The whole spectrum. The "science" press usually is quite
interested, and does a generally good job of reporting a difficult topic.
The most usual response of "real" people seems to be to lump us with
other climate-change studies, and then either worry or ignore it,
depending on previous ideas.
TIDEPOOL: Politically, I've heard people argue that because the climate
is constantly changing, there is no way we can prove that humans are to
blame for the current warming trend. Thus the rationalization that we
need do nothing to curb the emission of greenhouse gasses. Have you heard
this argument? How do you find yourself responding?
ALLEY: I have to agree that we cannot prove humans are to blame. But, the
odds are pretty high. I sometimes ask people to imagine playing a game
with me. We take a die, with two sides labeled "warm", two "normal", and
two "cold". We roll it, and if it comes up "warm", they pay me; if
"cold", I pay them. After playing for a while, with me winning, they
discover that I have three sides labeled "warm" and only one "cold".
1) Can they prove that my cheating by labeling an extra side "warm"
caused me to win? Of course not; maybe I would have won anyway.
2) Was it fair; or, did I increase my chances of getting warmth? Of
course I did.
Humans are making changes in the atmosphere, that should cause
temperatures to rise when averaged over large areas and long times, but
with wiggles and wobbles, some places warming more, some perhaps cooling.
The earth is on average warming. It is highly likely that we are
responsible, although one can never prove it unequivocally because the
climate system does still play dice.
TIDEPOOL: Underlying this research is an understanding that the earth's
climate is not just a "gas" problem. Rather climate is a complex machine
with biological, water (temp, current and density) solar and atmospheric
components -- all interacting. Even the geology of moving continents
comes into play. Do our current computer models of climate take these
interactions into account?
ALLEY: There are many wonderful efforts to include more of the important
processes in the models, but there clearly are processes that are still
missing or are not fully represented in the "state of the art" models. In
general, the models don't do especially well at simulating all of the
size, speed, and extent of the abrupt changes of the past, so there must
still be at least something missing from the models.
TIDEPOOL: Is this larger sort of understanding of climate on the radar
screens of most policymakers? What about scientists in other fields?
ALLEY: I believe that the scientific community is now recognizing the new
results. Usually, the recognition in policy circles follows after the
recognition in science, and I don't think that everyone making policy is
"up to date" on this issue. I devoted a lot of time to the recent
National Research Council report on abrupt climate change ("Inevitable
Surprises") in the hope that it would help the new scientific results to
get a broader hearing.
TIDEPOOL: Monitoring our current climate indicators, what observable
phenomenon would really get you worried that a rapid change in climate
was on its way? What is the canary in the coal mine? The North Atlantic
Current shutting down?
ALLEY: The currents of the north Atlantic are important. The other things
that worry me (but about which I don't know a lot) are droughts at lower
latitudes. So, soil moisture in places where people grow lots of grain.
TIDEPOOL: How do we know the "boring" climatic period we're now in won't
last another 11,000 years.
ALLEY: It might. But whether with or without loaded dice, I personally
wouldn't want to bet on it.
The Two-Mile Time Machine
Ice Cores, Abrupt Climate Change and Our Future, by Richard B. Alley
reviewed by ED HUNT
What if global warming sparked a new Ice Age?
What if, instead of a slow linear increase in global temperatures, our
climate changed so quickly, it was as if someone had flipped a switch?
What if I told you that predictions of a gradual global warming over the
coming decades are really conservative, best case scenarios for human
civilization -- that in truth we might not have the luxury of taking
years to address greenhouse gas emissions or to adapt to changes in
In fact, we now know that climate throughout the Earth's history is
incredibly variable -- big changes come suddenly.
As Pennsylvania State University geophysicist Richard Alley explains in
his book The Two-Mile Time Machine Earth's climate is in a relatively
boring period right now. Climate wise, these last millennia have been the
best of times for human kind. But that could all change, very, very
Conditions have been just right for us to develop agriculture,
civilization and even industrial globalization. We've known for some time
now that the climate of the Earth used to be different, but it is only
recently that we've come to understand the history of our planet in a way
that gives us a glimpse of our future.
"Interpretation of ice cores, and of many other climate records has
recently revolutionized our view of Earth," Alley writes. "We once
believed that the climate is well-behaved -- a little change in the
brightness of the sun or the positions of the continents, or the
composition of the air causes a little change in the climate. The ice
cores tell a more complicated story."
"Sometimes, a small "push" has caused the climate to change a little, but
other times, a small push has knocked the Earth's climate system into a
different mode of operation, bringing new weather patterns to much of the
Earth in only a few years or decades. To scientists accustomed to changes
over geological time, it is almost as if someone had flipped a switch to
change the climate. Sometimes the climate jumped back and forth a few
times before settling into one pattern, almost as if the person flipping
the switch were an impish three-year-old. The climate jumps have been
much larger, quicker and more widespread than those that chased the
Greenland Vikings and the Oklahoma farmers from their homes -- or those
experienced by any other agricultural or industrial humans. Were such
changes to occur today, the consequences could be severe."
The Time Machine referred to in the title of Alley's book -- and the
source of much of this disturbing insight about our past climate -- are
ice core samples removed from glaciers in Greenland and Antarctica. All
glaciers are made up of annual snowfalls that don't melt off in the
summer. However, the best glaciers for recording past climate may lie in
Greenland -- where the cores are drilled two miles down -- and thousands
of years into our past.
"In Central Greenland, snow falls frequently throughout the year. The sun
never sets in the summer and never rises in the winter. Winter's snow is
buried without experiencing sunshine, but summer snow is "cooked" by the
intense summer sun. This solar heating changes the snow, making visible
So like the rings measuring a tree's growth, the annual layers of a
Greenland glacier can be examined to tell us much about the ancient
Two-Mile Time Machine is more than a fascinating scientific revelation,
however, it is also a excellent bit of science writing. It is easy to see
why Alley has won awards for his teaching as well as his research. Alley
packs information into your brain almost effortlessly. The voice --
occasionally slipping from the explanatory to the experiential -- can be
evocative, like when he describes the site of the ice pits dug during the
1990s to view the layers of ancient ice in Greenland.
"I have stood in such snow pits with dozens of people -- drillers,
journalists and others -- and so far, every visitor has been impressed.
The snow is blue, something like the blue seen by deep-sea divers, an
indescribable, almost achingly beautiful blue. Water, whether liquid or
ice, absorbs red light a bit more than blue. Let the light penetrate tens
of feet into the ocean and the red is filtered out, so only the blue
reaches your eyes. In snow, a ray of light passes through a tiny crystal,
is bent, goes through another, bounces off another and so staggers its
way to the viewer, going much farther than the straight line distance to
the eye. On the way, the red is lost and the result is a beautiful blue."
Just how much scientists can divine from these ice cores in astonishing.
Tiny pockets of air locked into the layers of the ice reveal the gaseous
mixture of the ancient atmosphere. They can tell how much methane and CO2
built up before the climate flipped. The thickness and composition of the
ice gives clues to weather and temperature. They can even see evidence of
human activity -- the burning of leaded gasoline during the middle part
of the 20th century for example.
Alley's ice core time travelers corroborate their findings with other
indicators -- samples of sediments from the bottoms of undisturbed
ancient lakes for example. The result has been startling even to the
scientists conducting the research. Armed with a year by year history of
our climate over the past 110,000 years, many of our assumptions about
the climate of the earth wind up shattered.
Alley and his team made headlines recently by revealing that the last ice
age ended very abruptly -- within a year or two. Yet that finding only
hints how variable the climate of our planet really is.
We tend to think of climate changes as happening on almost a geological
time scale -- too drawn out for humankind to notice. Global warming of
perhaps only one degree average change over 100 years has been so slow,
that some still refuse to believe it is occurring.
It turns out, the reason we have this perception is that over the last
11,000 years our climate has been very stable. The machinery of global
ocean and air currents, biology and geology have been acting like an
efficient thermostat, regulating the temperature of the planet to keep
things optimized for humans to develop agriculture -- and civilization.
Yet in the mind of the planet, this short 11,000 year period is the
exception, not the rule. Prior to the stability that set in, climate
varied into Ice Ages and warming periods. In fact we've actually been in
a long warming period for thousands of years now.
However, prior to 11,000 years ago, climate patterns swung like a
pendulum between warm and cold periods. On the edge of these shifts, the
change could be sudden and abrupt. An ice age could move down upon the
land in as little as a year or two -- and disappear just as quickly.
Try to wrap your mind around what such a variability would mean today. As
Alley notes in his opening chapter, imagine "if you went to bed in slushy
Chicago, but woke up with Atlanta's mild weather. Or worse, what if your
weather jumped back and forth between that of Chicago and Atlanta?"
"Large, rapid and widespread climate changes were common on Earth for
most of the time for which we have good records, but were absent during
the few critical millennia when humans developed agriculture and
industry. While our ancestors were spearing woolly mammoths and painting
cave walls, the climate was wobbling wildly. A few centuries of warm,
wet, calm climate alternated with a few centuries of cold, dry windy
weather. The climate jumped between cold and warm not over centuries but
in as little as a single year. Often conditions "flickered" back and
forth between cold and warm for a few decades before settling down."
How can this be?
"The jumps have occurred in Earth's wildly complex, linked,
feedback-dominated climate system in which atmosphere, oceans, ice and
land surface and living things interact with each other and with the
solar system to drive weather forecasters and climate scientists to
distraction," according to Alley.
Using the crystallized timeline of Greenland ice cores as a back drop,
Alley explains that the climate of the Earth is controlled by a number of
"dials and switches" that can be turned and flipped by various actors.
These dials and switches control the energy the Earth receives from space
and the heat transfer system that moves warm air from the equator to the
northern and southern parts of the globe.
One important such switch is the North Atlantic conveyor -- an ocean
current system that allows people in England "to grow roses as far north
as Canadians find polar bears." The conveyor of ocean currents actually
circulates around the globe through the Pacific and Atlantic oceans. In
the North Atlantic it brings warm water from the tropics very far North
-- thus allowing Northern Europe to grow crops.
As the conveyor warms the coasts of England and Ireland, however, the
water loses some heat. It becomes colder -- and through evaporation --
saltier. This now cold, salty water is dense and it sinks deep into the
depths of the ocean before it can freeze, thus turning the wheel at the
end of the conveyor belt and sending a deeper flow of cold water back
What happens if the conveyor belt shuts down? Well, it gets a lot harder
to grow roses -- and "groceries" -- in Europe that's for sure. Indeed,
"polar bears might just replace roses in the north of Great Britain,"
How do you shut down the global conveyor belt? The best place to disrupt
the belt is by "sticking a fork" into where the dense salty water falls
-- the North Atlantic. If you make the water less salty -- it becomes
less dense and therefore, cannot get cold enough to sink. If it doesn't
sink, the conveyor belt slows or stops. No more warm water from the
equator distributed into the Northern climes. No more roses or groceries
in Northern Europe.
Once the conveyor is stopped, it can be very hard to get it going again.
For those concerned about global warming, this is where things get
seriously scary. Add a little more fresh water to the north Atlantic --
say in the form of melting ice, rainfall or river runoff -- and computer
models show that this is enough to jam the conveyor -- slowing it or
Ice cores, tree rings and sediments indicate that the balance of
conditions keeping the conveyor going is delicate. In the past the
conveyor has been slowed and stopped, and when this happens, the climate
in the North suddenly gets very cold very quickly.
So if global warming puts enough freshwater into the North Atlantic a
switch could be flipped and we may suddenly find ourselves in an Ice Age
-- possibly struggling through a period of variability as the climate
staggers back and forth along the way.
As Alley writes, "...climate may be like a drunk -- when left alone; it
sits, when forced to move, it staggers."
For all of human history, the Earth's climate has been somewhat stable,
sitting, but as greenhouse gasses collect in the atmosphere and the
Earth's global temperature rises, we may be closing the bar, forcing the
drunk to get up and move along in his unpredictable, sudden and lurching
READ A BRIEF Q&A WITH RI
WSU Vancouver Scientists Studying Frozen Chunks of Ancient Atmosphere
By ED HUNT [posted.8.15.98]
VANCOUVER, WA--In the new labs of Washington State University's Vancouver
Campus, paleoclimatologists are analyzing frozen chunks of ancient
atmosphere in ice core samples from Greenland and Antarctica to tell us
how the earth's climate has changed in the past, so we can gain better
understanding what may lie ahead.
Environmental Sciences Prof. Ed Brook brings two graphs over to the
table, each one representing the most recent 400,000 years of the earth's
climate. Ironically the climate on earth 400,000 years ago was much like
it is today, but between the two ends of the graph are huge spikes and
drops in temperature, ice ages and a period of dynamic climate
variability the likes of which written human civilization has never seen,
Brook's first graph plots temperature over time. The temperature data is
supported by other samples from oceans sediments around the world. He
points to a half-inch smudge of tight data points representing the last
11,000 years. This represents all of human history, he explains--a time
in which the earth's climate has been pretty stable.
Right after the this period, the temperature line takes a steep six inch
dive--ice age, glaciers. But instead of stabilizing there, the line
climbs and dives steeply for thousands of years--quickly growing warmer,
rapidly cooling off, all of this happening before humans had much
opportunity to have any affect on greenhouse gasses. Brook explains that
these periods represent rapid fluctuations in the temperature and
climate--the kind of rapid heating and cooling we've never seen before,
but the kind of dramatic shifts we now know are possible--a part of
"Compared to this the ENSO (El Ni�o Southern Oscillation) is tame," Brook
said. "In some cases we see a 5 to 10 degree jump in average air
temperature in a decade... that's 5 to 10 degrees Celsius."
For comparison, most of the dire predictions surrounding current global
warming problems focus on a global increase in temperature of only one to
five degrees in fifty years. Without our help, the earth is capable of a
The second graph is a transparency that fits over the first. It shows the
concentration of methane in the atmosphere. Scientists like Brook can
actually get samples of the ancient atmosphere trapped in the undisturbed
ice of Greenland and Antarctica. Brook explains that as snow falls, it
traps air pockets between the flakes. As more snow falls on top of it, it
gets compressed--eventually enough compression produces ice with the
atmospheric gasses still trapped inside. Drill down far enough and you
can sample the atmosphere back as far as 400,000 years.
In turn, the atmosphere can tell us what the planet was doing. It can
tell us whether there were more swamps and tundra than deserts and
prairies. Since the atmosphere mixes almost completely in a relatively
short period of time, our north and south poles have acted like ice
boxes, preserving samples of the air for thousands of years.
Brook and his team of researchers are more concerned with the period of
rapid variability that occurred after the last big drop in temperature.
They are interested in a famous cold period called the Younger Dryas. At
the end of this period--about 11.8 thousand years ago, methane took a
huge jump--from 400 parts per billion to 750 parts per billion in the
short span of 200 years. Things warmed up quickly too.
Samples of methane show that there is a strong relationship between the
amount of methane in the atmosphere and the spikes in
temperature-increases in methane seem to follow the same rhythm as
increases in temperature throughout the variable period. Carbon dioxide
shows a similar relationship. The correlation is strong enough that
scientists are sure they are somehow connected.
What Brook is trying to figure out is did the increase in methane cause
the temperature change, or did the temperature change cause the increase
"We think the temperature changed first, then the methane responded,"
Brook says. "Decomposition in wetlands increases the warmer and wetter it
is, and more methane would be made. The methane jump we see is not
forcing but tracing the climate change for us."
More research and ice cores will help definitively prove of disprove
their theory. Brook will study methane while a fellow researcher studies
nitrogen concentrations that can actually mark the time of the
temperature changes themselves. Brook said he thinks the methane lags
behind warmer temperatures. Other things can heat or cool things here on
earth including the proximity to the sun, the angle of the earth's axis
(both of which vary) and the complex cycles of interaction between
tropical currents and up-welling, trade winds and ocean temperatures.
Some other factor may have warmed the earth first, creating more wetlands
and swamps, and thus producing more methane.
There's good reason to want to know the answer to the question of what
came first. There's also a good reason why research like Brook's has been
making headlines for the past month.
Methane and CO2 are greenhouse gasses that we humans have been producing
in a abundance for the last century and things are heating up. This
century, most of the warmest average global temperatures have been
recorded in this decade. We're changing our climate, and to better
understand what kind of impact we're going to have in the long run, we
first have to know how the earth's climate varied before we started
monkeying around with things.
"You can argue about the human impact on current changes in climate but
the fact that there is change is unmistakable," Brook says. And the
record shows, we're influencing a system capable of incredible
variability. "Now we know the climate is capable of having more than one
mode of operation. We've had equitable climate for the last 11,000 years.
Can we do something to kick it into the variable mode or some other mode
we don't know about? Understanding the sequence of events should help us
better understand what our impact could be."
I ask Brook to show me where current methane and CO2 levels are in our
atmosphere compared with the climate record. Brook points to a place
about six inches above the page---literally off the chart.
"In the last 400,000 years at least, it has never been this way," Brook
says. "Methane is at a lot higher levels now than ever before."
So is CO2, the greenhouse gas most people talk about. It's the stuff that
comes out of exhaust pipes and smoke stacks. Current measurements show
about 360 parts per million in the atmosphere. In the last 400,000 years
it has never been higher than 280 parts per million.
We've only been directly measuring the CO2 in our atmosphere for the last
47 years and we've only been measuring methane since 1980. More
importantly, in the last 100 years, the climate hasn't changed all that
much. That's another reason why ice core sampling of climate variability
is important. It can show how sensitive the atmosphere is and can also be
used to help calibrate computer models of what will happen given the most
recent increases in gasses such as methane and CO2, Brook explains.
"If you want to find out what happens when you double the CO2 in the
earth's atmosphere, there's no way to test that. We can't do experiments
like other types of science," Brook said. "That's why climate models are
so important. But the earth's atmosphere is so complicated it is hard to
know if they represent reality. The more long term information on climate
and atmosphere we can gather, the better those models will be."
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