Climate Change: The Evidence and Our Options
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The Behavior Analyst 2010, 33, 153–170 No. 2 (Fall)
Climate Change: The Evidence and Our Options
Lonnie G. Thompson
The Ohio State University
Glaciers serve as early indicators of climate change. Over the last 35 years, our research team has
recovered ice-core records of climatic and environmental variations from the polar regions and
from low-latitude high-elevation ice fields from 16 countries. The ongoing widespread melting of
high-elevation glaciers and ice caps, particularly in low to middle latitudes, provides some of the
strongest evidence to date that a large-scale, pervasive, and, in some cases, rapid change in
Earth’s climate system is underway. This paper highlights observations of 20th and 21st century
glacier shrinkage in the Andes, the Himalayas, and on Mount Kilimanjaro. Ice cores retrieved
from shrinking glaciers around the world confirm their continuous existence for periods ranging
from hundreds of years to multiple millennia, suggesting that climatological conditions that
dominate those regions today are different from those under which these ice fields originally
accumulated and have been sustained. The current warming is therefore unusual when viewed
from the millennial perspective provided by multiple lines of proxy evidence and the 160-year
record of direct temperature measurements. Despite all this evidence, plus the well-documented
continual increase in atmospheric greenhouse gas concentrations, societies have taken little
action to address this global-scale problem. Hence, the rate of global carbon dioxide emissions
continues to accelerate. As a result of our inaction, we have three options: mitigation,
adaptation, and suffering.
Key words: climate, global warming
Climatologists, like other scientists, speaking before Congressional com-
tend to be a stolid group. We are not mittees. Why then are climatologists
given to theatrical rantings about speaking out about the dangers of
falling skies. Most of us are far more global warming? The answer is that
comfortable in our laboratories or virtually all of us are now convinced
gathering data in the field than we that global warming poses a clear and
are giving interviews to journalists or present danger to civilization (‘‘Cli-
mate Change,’’ 2010).
That bold statement may seem like
This paper is based on the Presidential
Scholar’s Address given at the 35th annual hyperbole, but there is now a very
meeting of the Association for Behavior clear pattern in the scientific evidence
Analysis International, Phoenix, Arizona. I documenting that the earth is warm-
am grateful to Bill Heward for inviting me to ing, that warming is due largely to
give the address. I thank Mary Davis for her
help editing the text and figures. I wish to human activity, that warming is
thank all the field and laboratory team causing important changes in climate,
members from the Byrd Polar Research and that rapid and potentially cata-
Center who have worked so diligently over strophic changes in the near future
the years. I am especially indebted to the hard
work of our current research team: Ellen
are very possible. This pattern emerg-
Mosley-Thompson, Henry Brecher, Mary es not, as is so often suggested,
Davis, Paolo Gabrielli, Ping-Nan Lin, Matt simply from computer simulations,
Makou, Victor Zagorodnov, and all of our but from the weight and balance of
graduate students. Funding for our research
over the years has been provided by the
the empirical evidence as well.
National Science Foundation’s Paleoclimate
Program, the National Oceanic and Atmo- THE EVIDENCE
spheric Administration’s Paleoclimatology
and Polar Programs, the National Aeronautic Figure 1 shows northern hemi-
and Space Administration, Gary Comer sphere temperature profiles for the
Foundation, and The Ohio State University’s last 1,000 years from a variety of high-
Climate, Water and Carbon Program. This is
Byrd Polar Research Center Publication 1402.
resolution climate recorders such as
Address correspondence to Lonnie G. glacier lengths (Oerlemans, 2005), tree
Thompson (e-mail: thompson.3@osu.edu). rings (Briffa, Jones, Schwerngruber,
153
The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:27:38 153 Cust # 10-02154 LONNIE G. THOMPSON Figure 1. A variety of temperature records over the last 1,000 years, based on a variety of proxy recorders such as tree rings, ice cores, historical records, instrumental data, etc., shows the extent of the recent warming. The range of temperature projected by Meehl et al. (2007) to 2100 AD is shown by the shaded region, and the average of the range is depicted by the filled circle. Shiyatov, & Cook, 2002; Esper, Cook, (see National Research Council, 2006, & Schweingruber, 2002), and com- for a review of surface temperature bined sources that include some or all reconstructions). Although the vari- of the following: tree rings, sediment ous curves differ from one another, cores, ice cores, corals, and historical their general shapes are similar. Each records (Crowley & Lowery, 2000; data source shows that average north- Jones, Briffa, Barnett, & Tett, 1998; ern hemisphere temperatures re- Mann, Bradley, & Hughes, 1999; mained relatively stable until the late Moberg, Sonechkin, Holmgrem, Dat- 20th century. It is the agreement of senko, & Karlen, 2005). The heavy these diverse data sets and the pattern gray line is a composite of all these that make climatologists confident temperatures (Mann & Jones, 2003), that the warming trend is real. and the heavy black line depicts actual Because these temperature num- thermometer readings back to 1850 bers are based on northern hemi- The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:27:38 154 Cust # 10-02
CLIMATE CHANGE 155
sphere averages, they do not reflect in the center of Kibo crater, taken
regional, seasonal, and altitudinal between 2000 and 2007, when the
variations. For example, the average glacier split into two sections. As
temperature in the western United Furtwängler recedes, it is also thin-
States is rising more rapidly than in ning rapidly, from 9.5 m in 2000 to
the eastern part of the country, and 4.7 m in 2009 (for more images of
on average winters are warming Furtwängler’s retreat, see http://www.
faster than summers (Meehl, Arbla- examiner.com/examiner/x-10722-
ster, & Tebaldi, 2007). The most Orlando-Science-Policy-Examiner,-
severe temperature increases appear y2009m11d2-Mt-Kilimanjaros-Furt-
to be concentrated in the Arctic and wängler-Glacier-in-retreat). If you
over the Antarctic Peninsula as well connect the dots on the changes seen
as within the interior of the large to date and assume the same rate of
continents. This variability compli- loss in the future, within the next dec-
cates matters, and adds to the diffi- ade many of the glaciers of Kiliman-
culty of convincing the public, and jaro, a Swahili word meaning ‘‘shining
even scientists in other fields, that mountain,’’ will have disappeared.
global warming is occurring. Because The Quelccaya ice cap, which is
of this, it may be useful to examine located in southern Peru adjacent to
another kind of evidence: melting ice. the Amazon Basin, is the largest
tropical ice field on Earth. Quelccaya
Retreat of Mountain Glaciers has several outlet glaciers, glaciers
that extend from the edges of an ice
The world’s mountain glaciers and cap like fingers from a hand. The
ice caps contain less than 4% of the retreat of one of these, Qori Kalis,
world’s ice cover, but they provide has been studied and photographed
invaluable information about chang- since 1963. At the beginning of this
es in climate. Because glaciers are study, Qori Kalis extended 1,200 m
smaller and thinner than the polar ice out from the ice cap, and there was
sheets, their ratio of surface area to no melt water at the end (Figure 4,
volume is much greater; thus, they map top left). By the summer of
respond more quickly to temperature 2008, Qori Kalis had retreated to the
changes. In addition, warming trends very edge of Quelccaya, leaving
are amplified at higher altitudes behind an 84-acre lake, 60 m deep.
where most glaciers are located Over the years, a boulder near the
(Bradley, Keimig, Diaz, & Hardy, base camp has served as a benchmark
2009; Bradley, Vuille, Diaz, & Ver- against which to record the changes
gara, 2006). Thus, glaciers provide an in the position of the edge of the ice.
early warning system of climate In 1977 the ice was actually pushing
change; they are our ‘‘canaries in against the boulder (Figure 5, top),
the coal mine.’’ but by 2006 a substantial gap had
Consider the glaciers of Africa’s appeared and been filled by a lake
Mount Kilimanjaro (Figure 2). Us- (Figure 5, bottom). Thus, the loss of
ing a combination of terrestrial pho- Quelccaya’s ice is not only on the
togrammetric maps, satellite images, Qori Kalis glacier but also on the
and aerial photographs, we have margin of the ice cap itself. Since
determined that the ice fields on 1978, about 25% of this tropical ice
Kibo, the highest crater on Kiliman- cap has disappeared.
jaro, have lost 85% of their cover- The Himalayan Mountains are
age since 1912 (Thompson, Brecher, home to more than 15,000 glaciers.
Mosley-Thompson, Hardy, & Mark, Unfortunately, only a few of these
2009). glaciers have been monitored over an
Figure 3 shows a series of aerial extended period, so reliable ground
photographs of Furtwängler glacier, observations that are crucial for
The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:27:46 155 Cust # 10-02156 LONNIE G. THOMPSON Figure 2. The retreat of glaciers on Mount Kilimanjaro can be seen in the photographs from 1912, 1970, 2000, and 2006; from 1912 to 2006, 85% of the ice has disappeared. The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:27:46 156 Cust # 10-02
CLIMATE CHANGE 157 Figure 3. Deterioration of the Furtwängler glacier in the center of Kibo crater on Mount Kilimanjaro. Since 2000 the ice field has decreased in size and thickness and has divided in two. The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:27:55 157 Cust # 10-02
158 LONNIE G. THOMPSON Figure 4. Retreat of the Qori Kalis outlet glacier on the Quelccaya ice cap. Each line shows the extent of the ice. The photos along the bottom provide a pictorial history of the melting of the Qori Kalis outlet glacier and the formation of a lake. The retreat of Qori Kalis is similar to the loss of several Peruvian glaciers, as shown in the graph insert. determining regional retreat rates do A study of 67 glaciers in Alaska not yet exist. However, a recent study from the mid-1950s to the mid-1990s of an ice core from the Naimona’nyi shows that all are thinning (Arendt, glacier in the southwestern Hima- Echelmeyer, Harrison, Lingle, & Val- layas (Kehrwald et al., 2008) shows entine, 2002). In northern Alaska’s that ice is disappearing from the top Brooks Range, 100% of the glaciers of the glacier, as shown by the lack of are in retreat, and in southeastern the radioactive bomb layers from the Alaska 98% are shrinking (Molnia, 1950s and early 1960s that appear in 2007). Glacier National Park in Mon- all Tibetan and Himalayan ice core tana contained more than 100 glaciers records (Thompson, 2000; Thomp- when it was established in 1910. son et al., 1990, 1997, 2006). Today, just 26 remain, and at the Glaciologists at the Institute of current rate of decrease it is estimated Tibetan Plateau Research in Beijing that by 2030 there will be no glaciers have been monitoring 612 glaciers in Glacier National Park (Hall & across the High Asian region since Fagre, 2003). The oldest glacier pho- 1980. These scientists found that tos come from the Alps. Ninety-nine from 1980 to 1990, 90% of these percent of the glaciers in the Alps are glaciers were retreating; from 1990 to retreating, and 92% of Chile’s Andean 2005, the proportion of retreating glaciers are retreating (Vince, 2010). glaciers increased to 95% (Yao, Pu, The pattern described here is re- Lu, Wang, & Yu, 2007). peated around the world. Mountain The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:07 158 Cust # 10-02
CLIMATE CHANGE 159 Figure 5. Top: photo taken in 1978 shows a margin of the Quelccaya ice cap pushing against a boulder. Bottom: the same margin is shown in a 2005 photo. The ice has receded and has been replaced by a small lake. The boulder shown in the top photo is located in the center of the white circle to the right. The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:13 159 Cust # 10-02
160 LONNIE G. THOMPSON
glaciers nearly everywhere are re- cube does not raise the water level in
treating. a glass when it melts, so a melting ice
shelf leaves sea levels unchanged.
Loss of Polar Ice But ice shelves serve as buttresses to
glaciers on land, and when those ice
Satellite documentation of the area
shelves collapse it speeds the flow of
covered by sea ice in the Arctic Ocean
the glaciers they were holding back
extends back three decades. This area,
into the ocean, which causes sea
measured each September, decreased
level to rise rapidly.
at a rate of about 8.6% per decade
from 1979 to 2007. In 2007 alone, Just days before this paper went to
24% of the ice disappeared. In 2006 press, a giant ice island four times the
the Northwest Passage was ice free size of Manhattan broke off the
for the first time in recorded history. Petermann glacier in Greenland. This
event alone does not prove global
As noted earlier, polar ice sheets
climate change, because half of the
are slower to respond to temperature
ice loss from Greenland each year
rise than the smaller mountain gla-
comes from icebergs calving from the
ciers, but they, too, are melting. The
margins. It is the fact that this event
Greenland ice sheet has also experi-
is part of a long-term trend of
enced dramatic ice melt in recent
increasing rates of ice loss, coupled
years. There has been an increase in
with the fact that temperature is
both the number and the size of lakes
increasing in this region at the rate
in the southern part of the ice sheet,
of 2u C (3.6u F) per decade, that
and crevices can serve as conduits
indicates that larger scale global
(called moulins) that transport melt-
climate change is underway.
water rapidly into the glacier. Water
has been observed flowing through The loss of ice in the Arctic and
these moulins down to the bottom of Antarctic regions is especially trou-
the ice sheet where it acts as a bling because these are the locations
of the largest ice sheets in the world.
lubricant that speeds the flow of ice
Of the land ice on the planet, 96% is
to the sea (Das et al., 2008; Zwally et
found on Greenland and Antarctica.
al., 2002).
Should all this ice melt, sea level
The ice in Antarctica is also
would rise over 64 m (Church et al.,
melting. The late John Mercer, a
2001; Lemke et al., 2007), and of
glacial geologist at The Ohio State
course the actual sea level would be
University, long ago concluded that
much higher due to thermal expan-
the first evidence of global warming
sion of the world’s oceans as they
due to increasing carbon dioxide
warm.
(CO2) would be the breakup of the
Although research shows some
Antarctic ice shelves (Mercer, 1978).
variability in the rate of ice loss, it is
Mean temperatures on the Antarctic
clear that mountain glaciers and
Peninsula have risen 2.5u C (4.5u F) in
polar ice sheets are melting, and there
the last 50 years, resulting in the
is no plausible explanation for this
breakup of the ice shelves in just the
but global warming. Add to this the
way Mercer predicted. One of the
laboratory evidence and the meteo-
most rapid of these shelf deteriora-
rological measurements, and the case
tions occurred in 2002, when the
for global warming cannot be denied.
Larsen B, a body of ice over 200 m
So what causes global temperatures
deep that covered an area the size of
to rise?
Rhode Island, collapsed in just 31 days
(see images http://earthobservatory.
CAUSES OF GLOBAL WARMING
nasa.gov/IOTD/view.php?id52351).
An ice shelf is essentially an iceberg Climatologists strive to reconstruct
attached to land ice. Just as an ice past climate variations on regional
The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:24 160 Cust # 10-02CLIMATE CHANGE 161
and global scales, but they also try to the 16th to 19th centuries. These
determine the mechanisms, called changes in climate, which are often
forcers, that drive climate change. cited by those who dismiss global
Climatologists recognize two basic warming as a normal, cyclical event,
categories of forcers. Natural forcers affected large areas, but not the Earth
are recurring processes that have as a whole. The medieval climate
been around for millions of years; anomaly showed warmth that match-
anthropogenic forcers are more re- es or exceeds that of the past decade
cent processes caused by human in some regions, but it fell well below
activity. recent levels globally (Mann et al.,
One familiar natural forcer is the 2009).
earth’s orbit around the sun, which The most powerful natural forcers
gives us our seasons. In the northern are variations in the orbit of the
hemisphere, June is warm because the Earth around the Sun, which last
sun’s rays fall more directly on it, and from 22,000 to 100,000 years. These
the sun appears high in the sky; in the ‘‘orbital forcings’’ are partly respon-
southern hemisphere, June is cool sible for both the ice ages (the glacial
because the sun’s rays hit the earth at periods during which large regions at
a deep angle, and the sun appears low high and midddle latitudes are cov-
in the sky. ered by thick ice sheets), and for the
Less obvious natural forcers in- warm interglacial periods such as the
clude short- and long-term changes in present Holocene epoch which began
the atmosphere and ocean. For ex- about 10,000 years ago.
ample, when Mount Pinatubo erupt- There is consensus among clima-
ed in the Philippines in 1991, it tologists that the warming trend we
spewed millions of tons of sulfuric have been experiencing for the past
gases and ash particles high into the 100 years or so cannot be accounted
atmosphere, blocking the sun’s rays. for by any of the known natural
This lowered global temperatures for forcers. Sunspot cycles, for example,
the next few years. Another natural can increase the sun’s output, raising
forcer is the linked oceanic and temperatures in our atmosphere. We
atmospheric system in the equatorial are seeing a temperature increase in
Pacific Ocean known as the El Niño- the troposphere, the lower level of our
Southern Oscillation (ENSO). ENSO atmosphere, and a temperature de-
occurs every 3 to 7 years in the crease in the stratosphere, the upper
tropical Pacific and brings warm, level. But this is the exact opposite of
wet weather to some regions and what we would get if increased solar
cool, dry weather to other areas. energy were responsible. Similarly,
Other natural forcers include peri- global temperatures have increased
odic changes in energy from the sun. more at night than during the day,
These include the 11- to 12-year again the opposite of what would
sunspot cycle and the 70- to 90-year occur if the sun were driving global
Wolf-Gleissberg cycle, a modulation warming. In addition, temperatures
of the amplitude of the 11-year solar have risen more in winter than in
cycle. These changes in solar energy summer. This, too, is the opposite of
can affect atmospheric temperature what would be expected if the sun
across large regions for hundreds of were responsible for the planet’s
years and may have caused the warming. High latitudes have warm-
‘‘medieval climate anomaly’’ in the ed more than low latitudes, and
northern hemisphere that lasted from because we get more radiation from
about 1100 AD to 1300 AD. Solar the sun at low latitudes, we again
cycles may also have played a role in would expect the opposite if the sun
the cause of the ‘‘little ice age’’ in were driving these changes. Thus,
North America and Europe during changes in solar output cannot ac-
The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:25 161 Cust # 10-02162 LONNIE G. THOMPSON count for the current period of global land, Boden, & Andres, 2006). As of warming (Meehl et al., 2007). ENSO this writing, the CO2 concentration in and other natural forcers also fail to the atmosphere is 391 ppmv (Mauna explain the steady, rapid rise in the Loa CO2 annual mean data from the earth’s temperature. The inescapable National Oceanic and Atmospheric conclusion is that the rise in temper- Administration, 2010), a level not ature is due to anthropogenic forces, seen at any time in 800,000 years. that is, human behavior. Climatologists have identified no The relatively mild temperatures of natural forcers that could account the past 10,000 years have been for this rapid and previously unseen maintained by the greenhouse effect, rise in CO2. a natural phenomenon. As orbital Methane raises temperature even forcing brought the last ice age to an more than CO2, and the amount of end, the oceans warmed, releasing methane in the atmosphere, like that CO2 into the atmosphere, where it of CO2, is also at a level not seen in trapped infrared energy reflected 800 millennia. Two thirds of current from the earth’s surface. This warmed emissions of methane are by-products the planet. The greenhouse effect is a of human activity, things like the natural, self-regulating process that is production of oil and natural gas, absolutely essential to sustain life on deforestation, decomposition of gar- the planet. However, it is not immu- bage and sewage, and raising farm table. Change the level of greenhouse animals. gases in the atmosphere, and the Many people find it difficult to planet heats up or cools down. believe that human activity can affect Greenhouse gases are captured in a system as large as Earth’s climate. ice, so ice cores allow us to see the After all, we are so tiny compared to levels of greenhouse gases in ages the planet. But every day we tiny past. The longest ice core ever human beings drive cars; watch recovered (from the European Proj- television; turn on lamps; heat or ect for Ice Coring in Antarctica) cool our houses and offices; eat food takes us 800,000 years back in time, transported to us by planes, ships, and includes a history of CO2 and and trucks; clear or burn forests; and methane levels preserved in bubbles behave in countless other ways that in the ice (Loulergue et al., 2008; directly or indirectly release green- Lüthi et al., 2008). The CO2 and house gases into the air. Together, we methane curves illustrated in Fig- humans emitted eight billion metric ure 6 show that the modern levels of tons of carbon to our planet’s atmo- these gases are unprecedented in the sphere in 2007 alone (Boden, Mar- last 800 millennia. land, & Andres, 2009). (CO2 weighs Globally, CO2 concentrations have 3.66 times more than carbon; that varied between 180 and 190 parts per means we released 29.3 billion metric million per volume (ppmv) during tons of CO2.) The evidence is over- glacial (cold) periods and between whelming that human activity is 270 and 290 ppmv during interglacial responsible for the rise in CO2, (warm) periods. However, since the methane, and other greenhouse gas onset of the Industrial Revolution, levels, and that the increase in these when fossil fuel use (chiefly coal and gases is fueling the rise in mean oil) began to burgeon, CO2 concen- global temperature. tration has increased about 38% over A global temperature rise of a few the natural interglacial levels (Forster degrees may not seem such a bad et al., 2007). Between 1975 and 2005, thing, especially to people living in CO2 emissions increased 70%, and harsh, cold climates. But global between 1999 and 2005 global emis- warming does not mean merely that sions increased 3% per year (Mar- we will trade parkas for T-shirts or The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:25 162 Cust # 10-02
CLIMATE CHANGE 163
Figure 6. Concentrations of carbon dioxide (CO2) and methane (CH4) over the last
800,000 years (eight glacial cycles) from East Antarctic ice cores. Data from Loulergue et al.
(2008) and Lüthi et al. (2008). The current concentrations of CO2 and CH4 are also shown
(Forster et al., 2007).
turn up the air conditioning. A sea levels. About half of this rise is due
warming planet is a changing planet, to thermal expansion: Ocean temper-
and the changes will have profound atures are rising, and as water warms
consequences for all species that live it expands. Put a nearly full cup of
on it, including humans. Those water in a microwave and heat it, and
changes are not just something our the water will spill over the cup.
children and grandchildren will have In addition to thermal expansion,
to deal with in the future; they are the oceans are rising because ice is
taking place now, and are affecting melting, and most of that water
millions of people. inevitably finds its way to the sea.
So far, most of that water has come
from mountain glaciers and ice caps
EFFECTS OF (Meier et al., 2007). As global tem-
GLOBAL WARMING peratures increase, sea level rise will
One effect of global warming that mainly reflect polar ice melt. So far,
everyone has heard about is a rise in ocean rise has been measured in
The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:25 163 Cust # 10-02164 LONNIE G. THOMPSON millimeters, but there is enough water In addition to the danger of in the Greenland ice sheet alone to inundation, rising sea levels bring salt raise sea levels by about 7 m, West water into rivers, spoil drinking wells, Antarctica over 5 m, and East and turn fertile farmland into useless Antarctica about 50 m (Lemke et fields of salty soil. These effects of al., 2007). If the Earth were to lose global warming are occurring now in just 8% of its ice, the consequences places like the lowlands of Bangla- for some coastal regions would be desh (Church et al., 2001). dramatic. The lower part of the People on dry land need the fresh Florida peninsula and much of water that is running into the sea. In Louisiana, including New Orleans, the spring, melting ice from moun- would be submerged, and low-lying tain glaciers, ice caps, and snow- cities, including London, New York, fields furnish wells and rivers that and Shanghai, would be endangered provide fresh water for drinking, (to see the effects of various magni- agriculture, and hydroelectric pow- tudes of sea level rise in the San er. For example, in the dry season, Francisco Bay area, go to http:// people in large areas of India, Nepal, cascade.wr.usgs.gov/data/Task2b-SFBay/ and southern China depend on rivers data.shtm). fed by Himalayan glaciers. The Low-lying continental countries retreat of these glaciers threatens such as the Netherlands and much the water supply of millions of of Bangladesh already find them- people in this part of the world. selves battling flooding more than Peru relies on hydroelectric power ever before. Many small island na- for 80% of its energy (Vergara et al., tions in the western Pacific (e.g., 2007), a significant portion of which Vanuatu) are facing imminent de- comes from mountain streams that struction as they are gradually over- are fed by mountain glaciers and ice run by the rising ocean. Indonesia is fields. In Tanzania, the loss of an island nation, and many of its Mount Kilimanjaro’s fabled ice cov- 17,000 islands are just above sea er would likely have a negative level. At the 2007 United Nations impact on tourism, which is the Climate Change Conference in Bali, country’s primary source of foreign Indonesian environmental minister currency. The glaciers and snow Rachmat Witoelar stated that 2,000 packs in the Rocky Mountains are of his country’s islands could be lost essential for farming in California, to sea level rise by 2030. At current one of the world’s most productive rates of sea level rise, another island agricultural areas. nation, the Republic of Maldives, will Global warming is expanding arid become uninhabitable by the end of areas of the Earth. Warming at the the century (http://unfcc.int/resource/ equator drives a climate system called docs/napa/mdv01.pdf). In 2008, the the Hadley Cell. Warm, moist air president of that country, Mohamed rises from the equator, loses its Nasheed, announced that he was moisture through rainfall, moves contemplating moving his people to north and south, and then falls to India, Sri Lanka, and Australia the Earth at 30u north and south (Schmidle, 2009). One of the major latitude, creating deserts and arid effects of continued sea level rise will regions. There is evidence that over be the displacement of millions of the last 20 years the Hadley Cell has people. Where millions of climate expanded north and south by about refugees will find welcome is unclear. 2u latitude, which may broaden the The migration of large numbers of desert zones (Seidel, Fu, Randel, & people to new territories with differ- Reichler, 2008; Seidel & Randel, ent languages and cultures will be 2007). If so, droughts may become disruptive, to say the least. more persistent in the American The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:33 164 Cust # 10-02
CLIMATE CHANGE 165
Southwest, the Mediterranean, Aus- Asian ice fields, as measured by the
tralia, South America, and Africa. Gravity Recovery and Climate Ex-
Global warming can also have periment satellite observations be-
effects that seem paradoxical. Con- tween 2003 and 2009. Ice retreat in
tinued warming may change ocean the Himalayas slowed slightly during
currents that now bring warm water this period, and loss in the mountains
to the North Atlantic region, giving it to the northwest increased markedly
a temperate climate. If this happens, over the last few years. Nevertheless,
Europe could experience a cooling the average rate of ice melt in the
even as other areas of the world region was twice the rate of four
become warmer. decades before. In the last decade,
many of the glaciers that drain
Accelerating Change Greenland and Antarctica have ac-
celerated their discharge into the
It is difficult to assess the full
world’s oceans from 20% to 100%
effects of global warming, and harder
(Lemke et al., 2007).
still to predict future effects. Climate
Increasing rates of ice melt should
predictions are made with computer
mean an increasing rate of sea level
models, but these models have as-
rise, and this is in fact the case. Over
sumed a slow, steady rate of change.
most of the 20th century, sea level
Our best models predict a tempera-
rose about 2 mm per year. Since
ture rise in this century of between
1990, the rate has been about 3 mm
2.4u and 4.5u C (4.3u and 8.1u F), with
per year.
an average of about 3u C (5.4u F;
So, not only is Earth’s temperature
Meehl et al., 2007; Figure 1). But
rising, but the rate of this change is
these models assume a linear rise in
accelerating. This means that our
temperature. Increasingly, computer
future may not be a steady, gradual
models have underestimated the
change in the world’s climate, but an
trends because, in fact, the rate of
abrupt and devastating deterioration
global temperature rise is accelerat-
from which we cannot recover.
ing. The average rise in global
temperature was 0.11u F per decade
over the last century (National Oce- Abrupt Climate Change Possible
anic and Atmospheric Administra- We know that very rapid change in
tion, 2009). Since the late 1970s, climate is possible because it has
however, this rate has increased to occurred in the past. One of the most
0.29u F per decade, and 11 of the remarkable examples was a sudden
warmest years on record have oc- cold, wet event that occurred about
curred in the last 12 years. May, 5,200 years ago, and left its mark in
2010, was the 303rd consecutive many paleoclimate records around
month with a global temperature the world.
warmer than its 20th-century average The most famous evidence of this
(National Oceanic and Atmospheric abrupt weather change comes from
Administration, 2010). Otzi, the ‘‘Tyrolean ice man’’ whose
The acceleration of global temper- remarkably preserved body was dis-
ature is reflected in increases in the covered in the Eastern Alps in 1991
rate of ice melt. From 1963 to 1978, after it was exposed by a melting
the rate of ice loss on Quelccaya was glacier. Forensic evidence suggests
about 6 m per year. From 1991 to that Otzi was shot in the back with
2006, it averaged 60 m per year, 10 an arrow, escaped his enemies, then
times faster than the initial rate sat down behind a boulder and bled
(Thompson et al., 2006). A recent to death. We know that within days
paper by Matsuo and Heki (2010) of Otzi’s dying there must have been
reports uneven ice loss from the high a climate event large enough to
The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:33 165 Cust # 10-02166 LONNIE G. THOMPSON entomb him in snow; otherwise, his more of the initial event. The best body would have decayed or been way to understand this phenomenon eaten by scavengers. Radiocarbon as it relates to climate change is dating of Otzi’s remains revealed that through some very plausible exam- he died around 5,200 years ago ples: (Baroni & Orombelli, 1996). Higher global temperatures mean The event that preserved Otzi dryer forests in some areas, which could have been local, but other means more forest fires, which means evidence points to a global event of more CO2 and ash in the air, which abrupt cooling. Around the world raises global temperature, which organic material is being exposed for means more forest fires, which means the first time in 5,200 years as glaciers … recede. In 2002, when we studied the Higher global temperatures mean Quelccaya ice cap in southern Peru, melting ice, which exposes darker we found a perfectly preserved wet- areas (dirt, rock, water) that reflect land plant. It was identified as Dis- less solar energy than ice, which tichia muscoides, which today grows means higher global temperatures, in the valleys below the ice cap. Our which means more melting ice, which specimen was radiocarbon dated at means … 5,200 years before present (Thomp- Higher global temperatures mean son et al., 2006). As the glacier tundra permafrost melts, releasing continues to retreat, more plants CO2 and methane from rotted organ- have been collected and radiocarbon ic material, which means higher dated, almost all of which confirm global temperature, which means the original findings (Buffen, Thomp- more permafrost melting, which son, Mosley-Thompson, & Huh, means … 2009). Positive feedback increases the rate Another record of this event comes of change. Eventually a tipping point from the ice fields on Mount Kiliman- may be reached, after which it could jaro. The ice dating back 5,200 years be impossible to restore normal shows a very intense, very sudden conditions. Think of a very large decrease in the concentration of heavy boulder rolling down a hill: When it oxygen atoms, or isotopes, in the first starts to move, we might stop it water molecules that compose the by pushing against it or wedging ice (Thompson et al., 2002). Such a chocks under it or building a barrier, decrease is indicative of colder tem- but once it has reached a certain peratures, more intense snowfall, or velocity, there is no stopping it. We both. do not know if there is a tipping The Soreq Cave in Israel contains point for global warming, but the speleothems that have produced con- possibility cannot be dismissed, and it tinuous climate records spanning tens has ominous implications. Global of thousands of years. The record warming is a very, very large boulder. shows that an abrupt cooling also Even if there is no tipping point occurred in the Middle East about (or we manage to avoid it), the ac- 5,200 years ago, and that it was the celeration of warming means seri- most extreme climatic event in the ous trouble. In fact, if we stopped last 13,000 years (Bar-Matthews, emitting greenhouse gases into the Ayalon, Kaufman, & Wasserburg, atmosphere tomorrow, temperatures 1999). would continue to rise for 20 to One way that rapid climate change 30 years because of what is already can occur is through positive feed- in the atmosphere. Once methane is back. In the physical sciences, posi- injected into the troposphere, it tive feedback means that an event has remains for about 8 to 12 years an effect which, in turn, produces (Prinn et al., 1987). Carbon dioxide The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:33 166 Cust # 10-02
CLIMATE CHANGE 167
has a much longer residence: 70 to cedures (e.g., Govindasamy & Calde-
120 years. Twenty percent of the CO2 ira, 2000; Wigley, 2006). One exam-
being emitted today will still affect ple is burying carbon in the ocean or
the earth’s climate 1,000 years from under land surfaces (Brewer, Fried-
now (Archer & Brovkin, 2008). erich, Peltzer, & Orr, 1999). Geo-
If, as predicted, global temperature engineering ideas are intriguing, but
rises another 3u C (5.4u F) by the end some are considered radical and may
of the century, the earth will be lead to unintended negative conse-
warmer than it has been in about 3 quences (Parkinson, 2010).
million years (Dowsett et al., 1994; Adaptation is reactive. It involves
Rahmstorf, 2007). Oceans were then reducing the potential adverse im-
about 25 m higher than they are pacts resulting from the by-products
today. We are already seeing impor- of climate change. This might include
tant effects from global warming; constructing sea barriers such as
the effects of another 3u C (5.4u F) dikes and tidal barriers (similar to
increase are hard to predict. Howev- those on the Thames River in Lon-
er, such a drastic change would, at don and in New Orleans), relocating
the very least, put severe pressure on coastal towns and cities inland,
civilization as we know it. changing agricultural practices to
counteract shifting weather patterns,
OUR OPTIONS and strengthening human and animal
immunity to climate-related diseases.
Global warming is here and is Our third option, suffering, means
already affecting our climate, so enduring the adverse impacts that
prevention is no longer an option. cannot be staved off by mitigation or
Three options remain for dealing adaptation. Everyone will be affected
with the crisis: mitigate, adapt, and by global warming, but those with
suffer. the fewest resources for adapting will
Mitigation is proactive, and in the suffer most. It is a cruel irony that so
case of anthropogenic climate change many of these people live in or near
it involves doing things to reduce the ecologically sensitive areas, such as
pace and magnitude of the changes grasslands (Outer Mongolia), dry
by altering the underlying causes. lands (Sudan and Ethiopia), moun-
The obvious, and most hotly debat- tain glaciers (the Quechua of the
ed, remedies include those that re- Peruvian Andes), and coastal low-
duce the volume of greenhouse gas lands (Bangledesh and the South Sea
emissions, especially CO2 and meth- island region). Humans will not be
ane. Examples include not only using the only species to suffer.
compact fluorescent lightbulbs, add- Clearly mitigation is our best
ing insulation to our homes, and option, but so far most societies
driving less, but societal changes such around the world, including the
as shutting down coal-fired power United States and the other largest
plants, establishing a federal carbon emitters of greenhouse gases, have
tax (as was recently recommended by done little more than talk about the
the National Academy of Sciences), importance of mitigation. Many
and substantially raising minimum Americans do not even accept the
mileage standards on cars (National reality of global warming. The fossil
Research Council, 2010). Another fuel industry has spent millions of
approach to mitigation that has dollars on a disinformation campaign
received widespread attention recent- to delude the public about the threat,
ly is to enhance the natural carbon and the campaign has been amazing-
sinks (storage systems) through ex- ly successful. (This effort is reminis-
pansion of forests. Some have sug- cent of the tobacco industry’s effort
gested various geo-engineering pro- to convince Americans that smoking
The Behavior Analyst bhan-33-02-02.3d 29/10/10 11:28:33 167 Cust # 10-02168 LONNIE G. THOMPSON
poses no serious health hazards.) As implications for the deglacierization of high
the evidence for human-caused cli- mountain regions. Geophysical Research
Letters, 36, L17701.
mate change has increased, the num- Bradley, R. S., Vuille, M., Diaz, H. F., &
ber of Americans who believe it has Vergara, W. (2006). Threats to water
decreased. The latest Pew Research supplies in the tropical Andes. Science,
Center (2010) poll in October, 2009, 312, 1755–1756.
Brewer, P. G., Friederich, G., Peltzer, E. T., &
shows that only 57% of Americans Orr, F. M., Jr. (1999). Direct experiments
believe global warming is real, down on the ocean disposal of fossil fuel CO2.
from 71% in April, 2008. Science, 284, 943–945.
There are currently no technolog- Briffa, K. R., Jones, P. D., Schweingruber, F.
ical quick fixes for global warming. H., Shiyatov, S. G., & Cook, E. R. (2002).
Unusual twentieth-century summer warmth
Our only hope is to change our in a 1,000-year temperature record from
behavior in ways that significantly Siberia. Nature, 376, 156–159.
slow the rate of global warming, Buffen, A. M., Thompson, L. G., Mosley-
thereby giving the engineers time to Thompson, E., & Huh, K.-I. (2009). Re-
devise, develop, and deploy techno- cently exposed vegetation reveals Holocene
changes in the extent of the Quelccaya ice
logical solutions where possible. Un- cap, Peru. Quaternary Research, 72, 157–
less large numbers of people take 163.
appropriate steps, including support- Chappellaz, J., Blunier, T., Kints, S., Dällen-
ing governmental regulations aimed bach, A., Barnola, J-M., Schwander, J., et
al. (1997). Changes in the atmospheric CH4
at reducing greenhouse gas emissions, gradient between Greenland and Antarctica
our only options will be adaptation during the Holocene. Journal of Geophysical
and suffering. And the longer we Research, 102, 15,987–15,997.
delay, the more unpleasant the adap- Church, J. A., Gregory, J. M., Huybrechts, P.,
tations and the greater the suffering Kuhn, M., Lambeck, K., Nhuan, M. T., et
al. (2001). Changes in sea level. In Climate
will be. change 2001. The scientific basis. Contribu-
Sooner or later, we will all deal tions of Working Group I to the 3rd
with global warming. The only ques- assessment of the IPCC. Cambridge, UK:
tion is how much we will mitigate, Cambridge University Press.
Climate change and the integrity of science.
adapt, and suffer. (2010). Retreived from http://www.pacinst.
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