by Peter Schwartz and Doug
The purpose of this report is to imagine the unthinkable – to push
the boundaries of current research on climate change so we may
better understand the potential implications on United States
We have interviewed leading climate change scientists, conducted
additional research, and reviewed several iterations of the scenario
with these experts. The scientists support this project, but caution
that the scenario depicted is extreme in two fundamental ways.
suggest the occurrences we outline would most likely
happen in a few regions, rather than on globally.
say the magnitude of the event may be considerably
We have created a climate change
scenario that although not the most likely, is plausible, and would
challenge United States national security in ways that should be
There is substantial evidence to indicate that significant global
warming will occur during the 21st century. Because changes have
been gradual so far, and are projected to be similarly gradual in
the future, the effects of global warming have the potential to be
manageable for most nations.
Recent research, however, suggests that
there is a possibility that this gradual global warming could lead
to a relatively abrupt slowing of the ocean’s thermohaline
conveyor, which could lead to harsher winter weather conditions,
sharply reduced soil moisture, and more intense winds in certain
regions that currently provide a significant fraction of the world’s
food production. With inadequate preparation, the result could be a
significant drop in the human carrying capacity of the Earth’s
The research suggests that once temperature rises above some
threshold, adverse weather conditions could develop relatively
abruptly, with persistent changes in the atmospheric circulation
causing drops in some regions of 5-10 degrees Fahrenheit in a single
decade. Paleoclimatic evidence suggests that altered climatic
patterns could last for as much as a century, as they did when the
ocean conveyor collapsed 8,200 years ago, or, at the extreme, could
last as long as 1,000 years as they did during the Younger Dryas,
which began about 12,700 years ago.
In this report, as an alternative to the
scenarios of gradual climatic warming that are so common, we outline
an abrupt climate change scenario patterned after the 100-year event
that occurred about 8,200 years ago. This abrupt change scenario is
characterized by the following conditions:
• Annual average temperatures drop
by up to 5 degrees Fahrenheit (3 degrees Celsius) over Asia and North America and 6
degrees Fahrenheit in northern Europe
• Annual average temperatures increase by up to 4 degrees
Fahrenheit (2.4 degrees Celsius) in key areas throughout Australia, South America, and
• Drought persists for most of the decade in critical
agricultural regions and in the water resource regions for major
population centers in Europe and eastern North America.
• Winter storms and winds intensify, amplifying the impacts of
Western Europe and the North Pacific
experience enhanced winds. The report explores how such an abrupt
climate change scenario could potentially de-stabilize the
geo-political environment, leading to skirmishes, battles, and even
war due to resource constraints such as:
1) Food shortages due to
decreases in net global agricultural production
2) Decreased availability and quality of fresh water in
key regions due to shifted precipitation patters, causing more
frequent floods and droughts
3) Disrupted access to energy supplies due to extensive
sea ice and storminess
As global and local carrying capacities
are reduced, tensions could mount around the world, leading to two
fundamental strategies: defensive and offensive. Nations with the
resources to do so may build virtual fortresses around their
countries, preserving resources for themselves. Less fortunate
nations especially those with ancient enmities with their neighbors,
may initiate in struggles for access to food, clean water, or
energy. Unlikely alliances could be formed as defense priorities
shift and the goal is resources for survival rather than religion,
ideology, or national honor.
This scenario poses new challenges for
the United States, and suggests several steps to be taken:
• Improve predictive climate models
to allow investigation of a wider range of scenarios and to
anticipate how and where changes could occur
• Assemble comprehensive predictive models of the potential
impacts of abrupt climate change to improve projections of how
climate could influence food, water, and energy
• Create vulnerability metrics to anticipate which countries are
most vulnerable to climate change and therefore, could
contribute materially to an increasingly disorderly and
potentially violent world.
• Identify no-regrets strategies such as enhancing capabilities
for water management
• Rehearse adaptive responses
• Explore local implications
• Explore geo-engineering options that control the climate.
There are some indications today that
global warming has reached the threshold where the thermohaline
circulation could start to be significantly impacted. These
indications include observations documenting that the North Atlantic
is increasingly being freshened by melting glaciers, increased
precipitation, and fresh water runoff making it substantially less
salty over the past 40 years.
This report suggests that, because of the potentially dire
consequences, the risk of abrupt climate change, although uncertain
and quite possibly small, should be elevated beyond a scientific
debate to a U.S. national security concern.
An Abrupt Climate Change Scenario
and Its Implications for United
States National Security
When most people think about climate change, they imagine gradual
increases in temperature and only marginal changes in other climatic
conditions, continuing indefinitely or even leveling off at some
time in the future. The conventional wisdom is that modern
civilization will either adapt to whatever weather conditions we
face and that the pace of climate change will not overwhelm the
adaptive capacity of society, or that our efforts such as those
embodied in the Kyoto protocol will be sufficient to mitigate the
The IPCC documents the threat of gradual
climate change and its impact to food supplies and other resources
of importance to humans will not be so severe as to create security
threats. Optimists assert that the benefits from technological
innovation will be able to outpace the negative effects of climate
Climatically, the gradual change view of the future assumes that
agriculture will continue to thrive and growing seasons will
lengthen. Northern Europe, Russia, and North America will prosper
agriculturally while southern Europe, Africa, and Central and South
America will suffer from increased dryness, heat, water shortages,
and reduced production. Overall, global food production under many
typical climate scenarios increases.
This view of climate change may be a
dangerous act of self-deception, as increasingly we are facing
weather related disasters—more hurricanes, monsoons, floods, and
dry-spells – in regions around the world. Weather-related events
have an enormous impact on society, as they influence food supply,
conditions in cities and communities, as well as access to clean
water and energy. For example, a recent report by the Climate Action
Network of Australia projects that climate change is likely to
reduce rainfall in the rangelands, which could lead to a 15 per cent
drop in grass productivity. This, in turn, could lead to reductions
in the average weight of cattle by 12 per cent, significantly
reducing beef supply.
Under such conditions, dairy cows are
projected to produce 30% less milk, and new pests are likely to
spread in fruit-growing areas. Additionally, such conditions are
projected to lead to 10% less water for drinking. Based on model
projections of coming change conditions such as these could occur in
several food producing regions around the world at the same time
within the next 15-30 years, challenging the notion that society’s
ability to adapt will make climate change manageable.
With over 400 million people living in drier, subtropical, often
over-populated and economically poor regions today, climate change
and its follow-on effects pose a severe risk to political, economic,
and social stability. In less prosperous regions, where countries
lack the resources and capabilities required to adapt quickly to
more severe conditions, the problem is very likely to be
For some countries, climate change could
become such a challenge that mass emigration results as the
desperate peoples seek better lives in regions such as the United
States that have the resources to adaptation.
Because the prevailing scenarios of gradual global warming could
cause effects like the ones described above, an increasing number of
business leaders, economists, policy makers, and politicians are
concerned about the projections for further change and are working
to limit human influences on the climate. But, these efforts may not
be sufficient or be implemented soon enough.
Rather than decades or even centuries of gradual warming, recent
evidence suggests the possibility that a more dire climate scenario
may actually be unfolding. This is why GBN is working with OSD to
develop a plausible scenario for abrupt climate change that can be
used to explore implications for food supply, health and disease,
commerce and trade, and their consequences for national security.
While future weather patterns and the
specific details of abrupt climate change cannot be predicted
accurately or with great assurance, the actual history of climate
change provides some useful guides. Our goal is merely to portray a
plausible scenario, similar to one which has already occurred in
human experience, for which there is reasonable evidence so that we
may further explore potential implications for United States
Creating the Scenario: Reviewing
graphic, derived from sampling of an ice core in Greenland,
shows a historical
tendency for particular regions to experience periods
of abrupt cooling
within periods of general warming.1
R.B. Alley, from The Two Mile Time Machine, 2000.
The Cooling Event 8,200 Years Ago
The climate change
scenario outlined in this report is modeled on a century-long
climate event that records from an ice core in Greenland
indicate occurred 8,200 years ago. Immediately following an
extended period of warming, much like the phase we appear to be
in today, there was a sudden cooling . Average annual
temperatures in Greenland dropped by roughly 5 degrees
Fahrenheit, and temperature decreases nearly this large are
likely to have occurred throughout the North Atlantic region.
During the 8,200 event severe
winters in Europe and some other areas caused glaciers to
advance, rivers to freeze, and agricultural lands to be less
productive. Scientific evidence suggests that this event was
associated with, and perhaps caused by, a collapse of the
ocean’s conveyor following a period of gradual warming.
Longer ice core and oceanic records suggest that there may have
been as many as eight rapid cooling episodes in the past 730,000
years, and sharp reductions in the ocean conveyer—a phenomenon
that may well be on the horizon – are a likely suspect in
causing such shifts in climate.
The Younger Dryas
About 12,700 years ago, also associated with an apparent
collapse of the thermohaline circulation, there was a cooling of
at least 27 degrees Fahrenheit in Greenland, and substantial
change throughout the North Atlantic region as well, this time
lasting 1,300 years. The remarkable feature of the Younger Dryas
event was that it happened in a series of decadal drops of
around 5 degrees, and then the cold, dry weather persisted for
over 1,000 years.
While this event had an enormous
effect on the ocean and land surrounding Europe (causing
icebergs to be found as far south as the coast of Portugal), its
impact would be more severe today – in our densely populated
society. It is the more recent periods of cooling that appear to
be intimately connected with changes to civilization, unrest,
inhabitability of once desirable land, and even the demise of
The Little Ice Age
Beginning in the 14th century, the North Atlantic region
experienced a cooling that lasted until the mid-19th century.
This cooling may have been caused by a significant slowing of
the ocean conveyor, although it is more generally thought that
reduced solar output and/or volcanic eruptions may have prompted
the oceanic changes. This period, often referred to as the
Little Ice Age, which lasted from 1300 to 1850, brought severe
winters, sudden climatic shifts, and profound agricultural,
economic, and political impacts to Europe.
The period was marked by persistent crop failures, famine,
disease, and population migration, perhaps most dramatically
felt by the Norse, also known as the Vikings, who inhabited
Iceland and later Greenland. Ice formations along the coast of
Greenland prevented merchants from getting their boats to
Greenland and fisherman from getting fish for entire winters. As
a result, farmers were forced to slaughter their poorly fed
livestock—because of a lack of food both for the animals and
themselves—but without fish, vegetables, and grains, there was
not enough food to feed the population.
Famine, caused in part by the more severe climatic conditions,
is reported to have caused tens of thousands of deaths between
1315 and 1319 alone. The general cooling also apparently drove
the Vikings out of Greenland—and some say was a contributing
cause for that society’s demise.
While climate crises like the Little Ice Age aren’t solely
responsible for the death of civilizations, it’s undeniable that
they have a large impact on society. It has been less than 175
years since 1 million people died due to the Irish Potato
famine, which also was induced in part by climate change.
A Climate Change
Scenario For the Future
The past examples of abrupt climate change suggest that it is
prudent to consider an abrupt climate change scenario for the future
as plausible, especially because some recent scientific findings
suggest that we could be on the cusp of such an event. The future
scenario that we have constructed is based on the 8,200 years before
present event, which was much warmer and far briefer than the
Younger Dryas, but more severe than the Little Ice Age.
This scenario makes plausible
assumptions about which parts of the globe are likely to be colder,
drier, and windier. Although intensified research could help to
refine the assumptions, there is no way to confirm the assumptions
on the basis of present models.
Rather than predicting how climate change will happen, our intent is
to dramatize the impact climate change could have on society if we
are unprepared for it. Where we describe concrete weather conditions
and implications, our aim is to further the strategic conversation
rather than to accurately forecast what is likely to happen with a
high degree of certainty. Even the most sophisticated models cannot
predict the details of how the climate change will unfold, which
regions will be impacted in which ways, and how governments and
society might respond.
However, there appears to be general
agreement in the scientific community that an extreme case like the
one depicted below is not implausible. Many scientists would regard
this scenario as extreme both in how soon it develops, how large,
rapid and ubiquitous the climate changes are. But history tells us
that sometimes the extreme cases do Abrupt Climate Change 8 occur,
there is evidence that it might be and it is DOD’s job to consider
Keep in mind that the duration of this event could be decades,
centuries, or millennia and it could begin this year or many years
in the future. In the climate change disruption scenario proposed
here, we consider a period of gradual warming leading to 2010 and
then outline the following ten years, when like in the 8,200 event,
an abrupt change toward cooling in the pattern of weather conditions
change is assumed to occur.
Warming Up to 2010
Following the most rapid century of
warming experienced by modern civilization, the first ten years
of the 21st century see an acceleration of atmospheric warming,
as average temperatures worldwide rise by 0.5 degrees Fahrenheit
per decade and by as much as 2 degrees Fahrenheit per decade in
the harder hit regions. Such temperature changes would vary both
by region and by season over the globe, with these finer scale
variations being larger or smaller than the average change. What
would be very clear is that the planet is continuing the warming
trend of the late 20th century.
Most of North America, Europe, and
parts of South America experience 30% more days with peak
temperatures over 90 degrees Fahrenheit (32.2 degrees Celsius) than they did a century
ago, with far fewer days below freezing. In addition to the
warming, there are erratic weather patterns: more floods,
particularly in mountainous regions, and prolonged droughts in
grain-producing and coastal-agricultural areas. In general, the
climate shift is an economic nuisance, generally affecting local
areas as storms, droughts, and hot spells impact agriculture and
other climate-dependent activities. (More French doctors remain
on duty in August, for example.)
The weather pattern, though, is not
yet severe enough or widespread enough to threaten the
interconnected global society or United States national
Warming Feedback Loops
As temperatures rise throughout the
20th century and into the early 2000s potent positive feedback
loops kick-in, accelerating the warming from 0.2 degrees
Fahrenheit, to 0.4 and eventually 0.5 degrees Fahrenheit per year
in some locations. As the surface warms, the hydrologic cycle
(evaporation, precipitation, and runoff) accelerates causing
temperatures to rise even higher. Water vapor, the most powerful
natural greenhouse gas, traps additional heat and brings average
surface air temperatures up.
As evaporation increases, higher
surface air temperatures cause drying in forests and grasslands,
where animals graze and farmers grow grain. As trees die and
burn, forests absorb less carbon dioxide, again leading to
higher surface air temperatures as well as fierce and
uncontrollable forest fires Further, warmer temperatures melt
snow cover in mountains, open fields, high-latitude tundra
areas, and permafrost throughout forests in cold-weather areas.
With the ground absorbing more and reflecting less of the sun’s
rays, temperatures increase even higher.
By 2005 the climatic impact of the
shift is felt more intensely in certain regions around the
world. More severe storms and typhoons bring about higher storm
surges and floods in low-lying islands such as Tarawa and Tuvalu
(near New Zealand).
In 2007, a particularly severe storm causes
the ocean to break through levees in the Netherlands making a
few key coastal cities such as The Hague unlivable.
Failures of the delta island levees
in the Sacramento River region in the Central Valley of
California creates an inland sea and disrupts the aqueduct
system transporting water from northern to southern California
because salt water can no longer be kept out of the area during
the dry season. Melting along the Himalayan glaciers
accelerates, causing some Tibetan people to relocate. Floating
ice in the northern polar seas, which had already lost 40% of
its mass from 1970 to 2003, is mostly gone during summer by
As glacial ice melts, sea levels
rise and as wintertime sea extent decreases, ocean waves
increase in intensity, damaging coastal cities. Additionally
millions of people are put at risk of flooding around the globe
(roughly 4 times 2003 levels), and fisheries are disrupted as
water temperature changes cause fish to migrate to new locations
and habitats, increasing tensions over fishing rights.
Each of these local disasters caused by severe weather impacts
surrounding areas whose natural, human, and economic resources
are tapped to aid in recovery. The positive feedback loops and
acceleration of the warming pattern begin to trigger responses
that weren’t previously imagined, as natural disasters and
stormy weather occur in both developed and lesser-developed
nations. Their impacts are greatest in less-resilient developing
nations, which do not have the capacity built into their social,
economic, and agricultural systems to absorb change.
As melting of the Greenland ice
sheet exceeds the annual snowfall, and there is increasing
freshwater runoff from high latitude precipitation, the
freshening of waters in the North Atlantic Ocean and the seas
between Greenland and Europe increases. The lower densities of
these freshened waters in turn pave the way for a sharp slowing
of the thermohaline circulation system.
The Period from 2010 to 2020
After roughly 60 years of slow freshening, the thermohaline
collapse begins in 2010, disrupting the temperate climate of
Europe, which is made possible by the warm flows of the Gulf
Stream (the North Atlantic arm of the global thermohaline
conveyor). Ocean circulation patterns change, bringing less warm
water north and causing an immediate shift in the weather in
Northern Europe and eastern North America.
The North Atlantic Ocean continues
to be affected by fresh water coming from melting glaciers,
Greenland’s ice sheet, and perhaps most importantly increased
rainfall and runoff. Decades of high-latitude warming cause
increased precipitation Abrupt Climate Change 10 and bring
additional fresh water to the salty, dense water in the North,
which is normally affected mainly by warmer and saltier water
from the Gulf Stream.
That massive current of warm water
no longer reaches far into the North Atlantic. The immediate
climatic effect is cooler temperatures in Europe and throughout
much of the Northern Hemisphere and a dramatic drop in rainfall
in many key agricultural and populated areas. However, the
effects of the collapse will be felt in fits and starts, as the
traditional weather patterns re-emerge only to be disrupted
again—for a full decade.
The dramatic slowing of the thermohaline circulation is
anticipated by some ocean researchers, but the United States is
not sufficiently prepared for its effects, timing, or intensity.
Computer models of the climate and ocean systems, though
improved, were unable to produce sufficiently consistent and
accurate information for policymakers. As weather patterns shift
in the years following the collapse, it is not clear what type
of weather future years will bring.
While some forecasters believe the
cooling and dryness is about to end, others predict a new ice
age or a global drought, leaving policy makers and the public
highly uncertain about the future climate and what to do, if
anything. Is this merely a “blip” of little importance or a
fundamental change in the Earth’s climate, requiring an urgent
massive human response?
Cooler, Drier, Windier Conditions for Continental Areas of
the Northern Hemisphere
The Weather Report:
• Drought persists for the entire decade in critical
agricultural regions and in the areas around major
population centers in Europe and eastern North
• Average annual temperatures drop by up to 5
degrees Fahrenheit (3 degrees Celsius) over Asia and North America and
up to 6 degrees Fahrenheit (3.6 degrees Celsius) in Europe.
• Temperatures increase by up to 4 degrees
Fahrenheit in key areas throughout Australia, South
America, and southern Africa.
• Winter storms and winds intensify, amplifying the
impact of the changes. Western Europe and the North
Pacific face enhanced westerly winds.
Each of the years from 2010-2020 sees average temperature drops
throughout Northern Europe, leading to as much as a 6 degree
Fahrenheit drop in ten years. Average annual rainfall in this
region decreases by nearly 30%; and winds are up to 15% stronger
on average. The climatic conditions are more severe in the
continental interior regions of northern Asia and North America.
The effects of the drought are more devastating than the
unpleasantness of temperature decreases in the agricultural and
populated areas. With the persistent reduction of precipitation
in these areas, lakes dry-up, river flow decreases, and fresh
water supply is squeezed, overwhelming available conservation
options and depleting fresh water reserves.
begin in key regions in Southern China and Northern Europe
around 2010 and last throughout the full decade. At the same
time, areas that were relatively dry over the past few decades
receive persistent years of torrential rainfall, flooding
rivers, and regions that traditionally relied on dryland
In the North Atlantic region and across northern Asia, cooling
is most pronounced in the heart of winter—December, January, and
February—although its effects linger through the seasons, the
cooling becomes increasingly intense and less predictable. As
snow accumulates in mountain regions, the cooling spreads to
summertime. In addition to cooling and summertime dryness, wind
pattern velocity strengthens as the atmospheric circulation
becomes more zonal.
While weather patterns are disrupted
during the onset of the climatic change around the globe, the
effects are far more pronounced in Northern Europe for the first
five years after the thermohaline circulation collapse. By the
second half of this decade, the chill and harsher conditions
spread deeper into Southern Europe, North America, and beyond.
Northern Europe cools as a pattern of colder weather lengthens
the time that sea ice is present over the northern North
Atlantic Ocean, creating a further cooling influence and
extending the period of wintertime surface air temperatures.
Winds pick up as the atmosphere
tries to deal with the stronger pole-to-equator temperature
gradient. Cold air blowing across the European continent causes
especially harsh conditions for agriculture. The combination of
wind and dryness causes widespread dust storms and soil loss.
Signs of incremental warming appear in the southern most areas
along the Atlantic Ocean, but the dryness doesn’t let up. By the
end of the decade, Europe’s climate is more like Siberia’s.
An Alternative Scenario for the Southern Hemisphere
There is considerable uncertainty about the climate dynamics of
the Southern Hemisphere, mainly due to less paleoclimatic data
being available than for the Northern Hemisphere. Weather
patterns in key regions in the Southern Hemisphere could mimic
those of the Northern Hemisphere, becoming colder, drier, and
more severe as heat flows from the tropics to the Northern
Hemisphere, trying to thermodynamically balance the climatic
Alternatively, the cooling of the
Northern Hemisphere may lead to increased warmth, precipitation,
and storms in the south, as the heat normally transported away
from equatorial regions by the ocean currents becomes trapped
and as greenhouse gas warming continues to Abrupt Climate Change
12 accelerate. Either way, it is not implausible that abrupt
climate change will bring extreme weather conditions to many of
the world’s key population and growing regions at the same time
– stressing global food, water, and energy supply.
The Regions: 2010 to 2020
The above graphic
shows a simplified view of the weather patterns portrayed in this
Europe. Hit hardest by the
climatic change, average annual temperatures drop by 6 degrees
Fahrenheit in under a decade, with more dramatic shifts along
the Northwest coast. The climate in northwestern Europe is
colder, drier, and windier, making it more like Siberia.
Southern Europe experiences less of a change but still suffers
from sharp intermittent cooling and rapid temperature shifts.
Reduced precipitation causes soil loss to become a problem
throughout Europe, contributing to food supply shortages. Europe
struggles to stem emigration out of Scandinavian and northern
European nations in search of warmth as well as immigration from
hard-hit countries in Africa and elsewhere.
United States. Colder, windier, and drier weather makes
growing seasons shorter and less productive throughout the
northeastern United States, and longer and drier in the
southwest. Desert areas face increasing windstorms, while
agricultural areas suffer from soil loss due to higher wind
speeds and reduced soil moisture. The change toward a drier
climate is especially pronounced in the southern states.
Coastal areas that were at risk during the warming period remain
at risk, as rising ocean levels continues along the shores. The
United States turns inward, committing its resources to feeding
its own population, shoring-up its borders, and managing the
increasing global tension.
China. China, with its high need for food supply given
its vast population, is hit hard by a decreased reliability of
the monsoon rains. Occasional monsoons during the summer season
are welcomed for their precipitation, but have devastating
effects as they flood generally denuded land. Longer, colder
winters and hotter summers caused by decreased evaporative
cooling because of reduced precipitation stress already tight
energy and water supplies. Widespread famine causes chaos and
internal struggles as a cold and hungry China peers jealously
across the Russian and western borders at energy resources.
Bangladesh. Persistent typhoons and a higher sea level
create storm surges that cause significant coastal erosion,
making much of Bangladesh nearly uninhabitable. Further, the
rising sea level contaminates fresh water supplies inland,
creating a drinking water and humanitarian crisis. Massive
emigration occurs, causing tension in China and India, which are
struggling to manage the crisis inside their own boundaries.
East Africa. Kenya, Tanzania, and Mozambique face
slightly warmer weather, but are challenged by persistent
drought. Accustomed to dry conditions, these countries were the
least influenced by the changing weather conditions, but their
food supply is challenged as major grain producing regions
Australia. A major food exporter, Australia struggles to
supply food around the globe, as its agriculture is not severely
impacted by more subtle changes in its climate. But the large
uncertainties about Southern Hemisphere climate change make this
benign conclusion suspect.
Impact on Natural
The changing weather patterns and ocean temperatures affect
agriculture, fish and wildlife, water and energy. Crop yields,
affected by temperature and water stress as well as length of
growing season fall by 10-25% and are less predictable as key
regions shift from a warming to a cooling trend.
As some agricultural pests die due to
temperature changes, other species spread more readily due to the
dryness and windiness – requiring alternative pesticides or
treatment regiments. Commercial fishermen that typically have rights
to fish in specific areas will be ill equipped for the massive
migration of their prey.
With only five or six key grain-growing
regions in the world (US, Australia, Argentina, Russia, China, and
India), there is insufficient surplus in global food supplies to
offset severe weather conditions in a few regions at the same time –
let alone four or five. The world’s economic interdependence make
the United States increasingly vulnerable to the economic disruption
created by local weather shifts in key agricultural and high
population areas around the world.
Catastrophic shortages of water and
energy supply – both which are stressed around the globe today
–cannot be quickly overcome.
Human civilization began with the stabilization and warming of the
Earth’s climate. A colder unstable climate meant that humans could
neither develop agriculture or permanent settlements. With the end
of the Younger Dryas and the warming and stabilization that
followed, humans could learn the rhythms of agriculture and settle
in places whose climate was reliably productive.
Modern civilization has never
experienced weather conditions as persistently disruptive as the
ones outlined in this scenario. As a result, the implications for
national security outlined in this report are only hypothetical. The
actual impacts would vary greatly depending on the nuances of the
weather conditions, the adaptability of humanity, and decisions by
Violence and disruption stemming from the stresses created by abrupt
changes in the climate pose a different type of threat to national
security than we are accustomed to today. Military confrontation may
be triggered by a desperate need for natural resources such as
energy, food and water rather than by conflicts over ideology,
religion, or national honor. The shifting motivation for
confrontation would alter which countries are most vulnerable and
the existing warning signs for security threats.
There is a long-standing academic debate over the extent to which
resource constraints and environmental challenges lead to
inter-state conflict. While some believe they alone can lead nations
to attack one another, others argue that their primary effect is to
act as a trigger of conflict among countries that face pre-existing
social, economic, and political tension. Regardless, it seems
undeniable that severe environmental problems are likely to escalate
the degree of global conflict.
Co-founder and President of the Pacific
Institute for Studies in Development, Environment, and Security,
Peter Gleick outlines the three most fundamental challenges abrupt
climate change poses for national security:
1. Food shortages due to
decreases in agricultural production
2. Decreased availability and quality of fresh water
due to flooding and droughts
3. Disrupted access to strategic minerals due to ice
In the event of abrupt climate change,
it’s likely that food, water, and energy resource constraints will
first be managed through economic, political, and diplomatic means
such as treaties and trade embargoes. Over time though, conflicts
over land and water use are likely to become more severe – and more
violent. As states become increasingly desperate, the pressure for
action will grow.
Decreasing Carrying Capacity
The graphic shows
how abrupt climate change may cause human carrying capacity
to fall below
usage of the eco-system, suggesting insufficient resources
leading to a
contraction of the population through war, disease, and famine.
Today, carrying capacity, which is
the ability for the Earth and its natural ecosystems including
social, economic, and cultural systems to support the finite
number of people on the planet, is being challenged around the
world. According to the International Energy Agency, global
demand for oil will grow by 66% in the next 30 years, but it’s
unclear where the supply will come from. Clean water is
similarly constrained in many areas around the world. With 815
million people receiving insufficient sustenance worldwide, some
would say that as a globe, we’re living well above our carrying
capacity, meaning there are not sufficient natural resources to
sustain our behavior.
Many point to technological innovation and adaptive behavior as
a means for managing the global ecosystem. Indeed it has been
technological progress that has increased carrying capacity over
time. Over centuries we have learned how to produce more food,
energy and access more water. But will the potential of new
technologies be sufficient when a crisis like the one outlined
in this scenario hits?
Abrupt climate change is likely to
stretch carrying capacity well beyond its already precarious
limits. And there’s a natural tendency or need for carrying
capacity to become realigned. As abrupt climate change lowers
the world’s carrying capacity aggressive wars are likely to be
fought over food, water, and energy. Deaths from war as well as
starvation and disease will decrease population size, which
overtime, will re-balance with carrying capacity.
When you look at carrying capacity on a regional or state level
it is apparent that those nations with a high carrying capacity,
such as the United States and Western Europe, are likely to
adapt most effectively to abrupt changes in climate, because,
relative to their population size, they have more resources to
call on. This may give rise to a more severe have, have-not
mentality, causing resentment toward those nations with a higher
It may lead to finger-pointing and
blame, as the wealthier nations tend to use more energy and emit
more greenhouse gasses such as CO2 into the
atmosphere. Less important than the scientifically proven
relationship between CO2 emissions and climate change
is the perception that impacted nations have – and the actions
The Link Between Carrying Capacity
Steven LeBlanc, Harvard
archaeologist and author of a new book called Carrying Capacity,
describes the relationship between carrying capacity and
warfare. Drawing on abundant archaeological and ethnological
data, LeBlanc argues that historically humans conducted
organized warfare for a variety of reasons, including warfare
over resources and the environment. Humans fight when they
outstrip the carrying capacity of their natural environment.
Every time there is a choice between
starving and raiding, humans raid. From hunter/gatherers through
agricultural tribes, chiefdoms, and early complex societies, 25%
of a population’s adult males die when war breaks out.
Peace occurs when carrying capacity goes up, as with the
invention of agriculture, newly effective bureaucracy, remote
trade and technological breakthroughs. Also a large scale
die-back such as from plague can make for peaceful
times---Europe after its major plagues, North American natives
after European diseases decimated their populations (that’s the
difference between the Jamestown colony failure and Plymouth
But such peaceful periods are
short-lived because population quickly rises to once again push
against carrying capacity, and warfare resumes. Indeed, over the
millennia most societies define themselves according to their
ability to conduct war, and warrior culture becomes deeply
ingrained. The most combative societies are the ones that
However in the last three centuries, LeBlanc points out,
advanced states have steadily lowered the body count even though
individual wars and genocides have grown larger in scale.
Instead of slaughtering all their enemies in the traditional
way, for example, states merely kill enough to get a victory and
then put the survivors to work in their newly expanded economy.
States also use their own
bureaucracies, advanced technology, and international rules of
behavior to raise carrying capacity and bear a more careful
relationship to it. All of that progressive behavior could
collapse if carrying capacities everywhere were suddenly lowered
drastically by abrupt climate change. Humanity would revert to
its norm of constant battles for diminishing resources, which
the battles Abrupt Climate Change 17 themselves would further
reduce even beyond the climatic effects. Once again warfare
would define human life.
Conflict Scenario Due to Climate
The chart above outlines some
potential military implications of climate change The two most
likely reactions to a sudden drop in carrying capacity due to
climate change are defensive and offensive.
The United States and Australia are likely to build defensive
fortresses around their countries because they have the
resources and reserves to achieve self-sufficiency. With diverse
growing climates, wealth, technology, and abundant resources,
the United States could likely survive shortened growing cycles
and harsh weather conditions without catastrophic losses.
Borders will be strengthened around
the country to hold back unwanted starving immigrants from the
Caribbean islands (an especially severe problem), Mexico, and
South America. Energy supply will be shored up through expensive
(economically, politically, and morally) alternatives such as
nuclear, renewables, hydrogen, and Middle Eastern contracts.
Pesky skirmishes over fishing
rights, agricultural support, and disaster relief will be
commonplace. Tension between the U.S. and Mexico rise as the
U.S. reneges on the 1944 treaty that guarantees water flow from
the Colorado River. Relief workers will be commissioned to
respond to flooding along the southern part of the east coast
and much drier conditions inland. Yet, even in this continuous
state of emergency the U.S. will be positioned well compared to
others. The intractable problem facing the nation will be
calming the mounting military tension around the world.
As famine, disease, and
weather-related disasters strike due to the abrupt climate
change, many countries’ needs will exceed their carrying
capacity. This will create a sense of desperation, which is
likely to lead to offensive aggression in order to reclaim
balance. Imagine eastern European countries, struggling to feed
their populations with a falling supply of food, water, and
energy, eyeing Russia, whose population is already in decline,
for access to its grain, minerals, and energy supply. Or,
picture Japan, suffering from flooding along its coastal cities
and contamination of its fresh water supply, eying Russia’s
Sakhalin Island oil and gas reserves as an energy source to
power desalination plants and energy-intensive agricultural
Envision Pakistan, India, and China
– all armed with nuclear weapons –skirmishing at their borders
over refugees, access to shared rivers, and arable land. Spanish
and Portuguese fishermen might fight over fishing rights –
leading to conflicts at sea. And, countries including the United
States would be likely to better secure their borders. With over
200 river basins touching multiple nations, we can expect
conflict over access to water for drinking, irrigation, and
transportation. The Danube touches twelve nations, the Nile runs
though nine, and the Amazon runs through seven.
In this scenario, we can expect
alliances of convenience. The United States and Canada may
become one, simplifying border controls. Or, Canada might keep
its hydropower—causing energy problems in the US. North and
South Korea may align to create one technically savvy and
nuclear-armed entity. Europe may act as a unified block –
curbing immigration problems between European nations – and
allowing for protection against aggressors. Russia, with its
abundant minerals, oil, and natural gas may join Europe.
In this world of warring states, nuclear arms proliferation is
inevitable. As cooling drives up demand, existing hydrocarbon
supplies are stretched thin. With a scarcity of energy supply –
and a growing need for access—nuclear energy will become a
critical source of power, and this will accelerate nuclear
proliferation as countries develop enrichment and reprocessing
capabilities to ensure their national security.
China, India, Pakistan, Japan, South
Korea, Great Britain, France, and Germany will all have nuclear
weapons capability, as will Israel, Iran, Egypt, and North
Korea. Managing the military and political tension, occasional
skirmishes, and threat of war will be a challenge. Countries
such as Japan, that have a great deal of social cohesion
(meaning the government is able to effectively engage its
population in changing behavior) are most likely to fair well.
Countries whose diversity already
produces conflict, such as India, South Africa and Indonesia,
will have trouble maintaining order. Adaptability and access to
resources will be key. Perhaps the most frustrating challenge
abrupt climate change will pose is that we’ll never know how far
we are into the climate change scenario and how many more years
– 10, 100, 1000 --- remain before some kind of return to warmer
conditions as the thermohaline circulation starts up again. When
carrying capacity drops suddenly, civilization is faced with new
challenges that today seem unimaginable.
Could This Really
Ocean, land, and atmosphere scientists at some of the world’s most
prestigious organizations have uncovered new evidence over the past
decade suggesting that the plausibility of severe and rapid climate
change is higher than most of the scientific community and perhaps
all of the political community is prepared for. If it occurs, this
phenomenon will disrupt current gradual global warming trends,
adding to climate complexity and lack of predictability.
And paleoclimatic evidence suggests that
such an abrupt climate change could begin in the near future. The
Woods Hole Oceanographic Institute reports that seas surrounding the
North Atlantic have become less salty in the past 40 years, which in
turn freshens the deep ocean in the North Atlantic. This trend could
pave the way for ocean conveyor collapse or slowing and abrupt
The above graphic shows early evidence
that a thermohaline circulation collapse may be imminent, as
the North Atlantic is increasingly being freshened by surrounding
seas that have become less salty over the past 40 years.2
from I Yashayaev, Bedford Institute of Oceanography as seen
in Abrupt Climate Change, Inevitable Surprises, National Research
The above two headlines appeared in
Nature Magazine in 2001 and 2002, respectively. They suggest that
the North Atlantic salinity level may lower, increasing the
likelihood of a thermohaline circulation collapse.
With at least eight abrupt climate change events documented in the
geological record, it seems that the questions to ask are:
Are we prepared for
history to repeat itself again?
There is a debate in newspapers around the globe today on the impact
of human activity on climate change. Because economic prosperity is
correlated with energy use and greenhouse gas emissions, it is often
argued that economic progress leads to climate change. Competing
evidence suggests that climate change can occur, regardless of human
activity as seen in climate events that happened prior to modern
It’s important to understand human impacts on the environment – both
what’s done to accelerate and decelerate (or perhaps even reverse)
the tendency toward climate change. Alternative fuels, greenhouse
gas emission controls, and conservation efforts are worthwhile
endeavors. In addition, we should prepare for the inevitable effects
of abrupt climate change – which will likely come regardless of
Here are some preliminary
recommendations to prepare the United States for abrupt climate
1) Improve predictive climate
Further research should be conducted
so more confidence can be placed in predictions about climate
change. There needs to be a deeper understanding of the
relationship between ocean patterns and climate change. This
research should focus on historical, current, and predictive
forces, and aim to further our understanding of abrupt climate
change, how it may happen, and how we’ll know it’s occurring.
2) Assemble comprehensive predictive models of climate change
Substantial research should be done on the potential
ecological, economic, social, and political impact of abrupt
climate change. Sophisticated models and scenarios should be
developed to anticipate possible local conditions. A system
should be created to identify how climate change may impact the
global distribution of social, economic, and political power.
These analyses can be used to mitigate potential sources of
conflict before they happen.
3) Create vulnerability metrics.
Metrics should be created to
understand a country’s vulnerability to the impacts of climate
change. Metrics may include climatic impact on existing
agricultural, water, and mineral resources; technical
capability; social cohesion and adaptability.
4) Identify no-regrets strategies.
No-regrets strategies should be
identified and implemented to ensure reliable access to food
supply and water, and to ensure national security.
5) Rehearse adaptive responses.
Adaptive response teams should be
established to address and prepare for inevitable climate driven
events such as massive migration, disease and epidemics, and
food and water supply shortages.
6) Explore local implications. The first-order effects of
climate change are local.
While we can anticipate changes in pest prevalence and
severity and changes in agricultural productivity, one has to
look at very specific locations and conditions to know which
pests are of concern, which crops and regions are vulnerable,
and how severe impacts will be. Such studies should be
undertaken, particularly in strategically important food
7) Explore geo-engineering options that control the climate.
Today, it is easier to warm than to
cool the climate, so it might be possible to add various gases,
such as hydrofluorocarbons, to the atmosphere to offset the
affects of cooling. Such actions, of course, would be studied
carefully, as they have the potential to exacerbate conflicts
It is quite plausible that within a decade the evidence of an
imminent abrupt climate shift may become clear and reliable. It is
also possible that our models will better enable us to predict the
consequences. In that event the United States will need to take
urgent action to prevent and mitigate some of the most significant
Diplomatic action will be needed to
minimize the likelihood of conflict in the most impacted areas,
especially in the Caribbean and Asia. However, large population
movements in this scenario are inevitable. Learning how to manage
those populations, border tensions that arise and the resulting
refugees will be critical. New forms of security agreements dealing
specifically with energy, food and water will also be needed.
In short, while the US itself will be
relatively better off and with more adaptive capacity, it will find
itself in a world where Europe will be struggling internally, large
number so refugees washing up on its shores and Asia in serious
crisis over food and water. Disruption and conflict will be endemic
features of life.