Implications for US National Security of 

Anticipated Climate Change

This memorandum was prepared by the

National Intelligence Council and was coordinated

with the US Intelligence Community.

21 September 2016

NIC WP 2016-01

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In the Intelligence Community’s (IC) analysis of the possible impacts of climate change on national 

security over the next 20 years, the IC takes as a scientific baseline the reports produced by the 

Intergovernmental Panel on Climate Change (IPCC), the international body responsible for assessing the 

science related to climate change. This memorandum does not assess effects on the homeland, nor does 

it evaluate the science of the IPCC reports.

Implications for US National Security of Anticipated Climate Change

Key Points

Long-term changes in climate will produce more extreme weather events and put greater stress on 

critical Earth systems like oceans, freshwater, and biodiversity. These in turn will almost certainly have 

significant effects, both direct and indirect, across social, economic, political, and security realms during 

the next 20 years. These effects will be all the more pronounced as people continue to concentrate in 

climate-vulnerable locations, such as coastal areas, water-stressed regions, and ever-growing cities.

Effects of Climate Change on National Security: Possible Pathways

Climate change and its resulting effects are likely to pose wide-ranging national security challenges for 

the United States and other countries over the next 20 years through the following pathways: 

 Threats to the stability of countries.

 Heightened social and political tensions.

 Adverse effects on food prices and availability.

 Increased risks to human health.

 Negative impacts on investments and economic competitiveness.

 Potential climate discontinuities and secondary surprises.

Effects of Climate Change on National Security: Possible Timeframes

The complexity of the climate, the uncertainties of modeling, and human choices make it difficult to 

project when and where specific severe weather events and other effects will affect national security 

most significantly. However, climate models do not diverge significantly on their estimates of future 

surface temperatures or on changes in other climate variables during the next 20 years, particularly 

when fluctuations in the climate system are considered (see chart on page 12).

 Now, the effects resulting from changing trends in extreme weather events suggest that 

climate-related disruptions are under way.

 Over the next five years, the security risks for the United States linked to climate change will 

arise primarily from distinct extreme weather events and from the exacerbation of currently 

strained conditions, like water shortages.

 Over the next 20 years, in addition to increasingly disruptive extreme weather events, the 

projected effects of climate change will play out in the combination of multiple weather 

disturbances with broader, systemic changes, including the effects of sea level rise.

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Climate change is projected to produce more intense and frequent extreme weather events, 

multiple weather disturbances, along with broader climatological effects, such as sea level rise. 

These are almost certain to have significant direct and indirect social, economic, political, and 

security implications during the next 20 years. These effects will be especially pronounced as 

populations continue to concentrate in climate-vulnerable locales such as coastal areas, waterstressed regions, and ever-growing cities. These effects are likely to pose significant national 

security challenges for the United States over the next two decades, though models forecast the 

most dramatic effects further into the future. While specific extreme weather events remain difficult to 

attribute entirely to climate change, unusual patterns of extreme and record-breaking weather events are 

likely to become more common, according to the Intergovernmental Panel on Climate Change (IPCC). 

 Extreme weather events, such as heavy rainfalls, floods, droughts, cyclones, and heatwaves, will 

disrupt critical human and natural systems. They could trigger crop failures, wildfires, energy 

blackouts, infrastructure breakdown, or infectious disease outbreaks. The frequency and magnitude 

of such events are increasing as the climate changes, according to the IPCC.

 Moreover, multiple weather disturbances—when several extreme weather events occur within a small 

region or short time—compound their impact while undercutting efforts by people and governments 

to cope. Clusters or rapid sequences of relatively modest weather events may cause more damage 

than very powerful single events.

 Global climatological stresses—such as sea-level rise, ocean acidification, permafrost and glacial melt, 

air quality degradation, changes in cloud cover, and sustained shifts in temperature and 

precipitation—could substantially alter broader natural and manmade systems involving where and 

how humans live and patterns of infectious disease outbreaks, as well as critical ecosystems.

The following table lays out the IPCC baseline for likely increases in extreme weather events in the 

decades ahead. Such events may occur at different rates of frequency, intensity, and location compared 

to historical patterns, and lack of preparedness for those changes—such as weather-related disasters, 

drought, famine, supply chain breakdown, or damage to infrastructure—may prove a primary cause of 

disruption.

According to the National Oceanic and Atmospheric Administration, weather reflects short-term 

conditions of the atmosphere in a particular region while climate encompasses the averages, variability, 

and other statistics of weather over longer periods of time. Weather includes very hot or cold or rainy 

days, while extreme weather events include extended droughts, floods, heatwaves, coldwaves, and 

intense tropical storms. Climate change reflects nonrandom change in climate measured over several 

decades or longer. Climate variability reflects the way that climate fluctuates above or below long-term 

average values.

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Effects of Climate Change on National Security: Possible Pathways

Climate and weather have long affected the national security of countries worldwide, although most often 

as a contributing factor that might be recognized only in retrospect. Sometimes the effects are 

dramatic—such as the brutal Russian winter that contributed to Hitler’s failed invasion in World War II—

but more often weather and climate exert indirect effects that shape underlying social, political, and 

economic conditions. Academic research on the impacts of climate on political and security outcomes is 

still sparse, but we judge that climate will affect US national security interests over the next 20 years 

through the following pathways.

Threats to the Stability of Countries

Many countries will encounter climate-induced disruptions—such as weather-related disasters, 

drought, famine, or damage to infrastructure—that stress their capacity to respond, cope with, or 

adapt. Climate-related impacts will also contribute to increased migration, which can be particularly 

disruptive if, for example, demand for food and shelter outstrips the resources available to assist those in 

need. 

When climate-related effects overwhelm a state’s capacity to respond or recover, its authority can be so 

undermined as to lead to large-scale political instability. Countries with weak political institutions, poor 

economic conditions, or where other risk factors for political strife are already present will be the most 

vulnerable to climate-linked instability. In the most dramatic cases, state authority may collapse partially 

or entirely. Climate-related instability is likely to create strong pressure for foreign aid, disaster assistance, 

or military responses. Even if climate-related disruptions do not undermine stability, however, some 

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governments could be so preoccupied with managing the effects that they have little time or energy left 

to engage on broader foreign policy issues.

 Fueled by unusually warm Arabian Sea waters, two separate tropical cyclones hit Yemen in 2015 in the 

span of just 10 days, including the first hurricane-strength storm to hit the country in recorded 

history. Already suffering a humanitarian crisis from war and water shortages, Yemen was unable to 

provide adequate relief for its citizenry. Heavy rains have since fueled the breeding of an unusually 

large population of desert locusts that threaten to devastate Yemen’s agriculture, and efforts to 

eradicate the locusts have been stymied both by the difficult security situation and by fear of killing 

bees, a crucial pollinator for the region’s honey and crop production.

Heightened Social and Political Tensions

Decreases in water and disputes over access to arable land will increase the risk of conflict between 

people who share river basins, aquifers, or land areas. Although historically water disputes between 

states have led to more water-sharing agreements than violent conflicts, according to academic studies, 

we judge that this trend could change over the next 20 years as water scarcity and variability intensify, 

possibly leading to disputes that pose greater challenges to security. Although environmental stress is 

rarely the sole cause, disputes between groups within countries over land and water resources are 

increasingly common as triggers for social violence and internal conflict, particularly when social and 

political tensions already exist.

 In 2014, citizens in a village on the outskirts of Mexico City, already water-stressed by drought, battled 

antiriot police during a protest over the diversion of spring water to a new development nearby. 

More than 100 police were injured, many seriously.

 In 2014, farmers and herdsmen in Nigeria clashed over access to grazing land and dwindling well 

water. Then President Goodluck Jonathan ordered military operations to reduce the violence.

 In 2012, mass protests and violence erupted over water shortages in Nouakchott, Mauritania. More 

than 70,000 refugees had migrated to Mauritania by July that year because of deteriorating 

conditions in neighboring Mali, putting additional pressure on Mauritania’s water and soil resources, 

already strained by drought and desertification.

Even if climate-induced environmental stresses do not lead to conflict, they are likely to contribute 

to migrations that exacerbate social and political tensions, some of which could overwhelm host 

governments and populations. Sudden extreme weather—such as from floods, droughts, and severe 

tropical storms—almost certainly will increase the number of displaced people, particularly in regions that 

are unaccustomed to or unprepared for such events. Rising sea levels and unexpectedly large storm 

surges could threaten small island states and low-lying coastal regions—including many megacities—with

flooding and saltwater contamination of freshwater. Over 20 years, the net effects of climate change on 

the patterns of global human movement and statelessness could be dramatic, perhaps unprecedented. If 

unanticipated, they could overwhelm government infrastructure and resources, and threaten the social 

fabric of communities.

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The Arctic region is warming twice as fast as the rest of the planet, transforming rapidly , according 

to the National Oceanic and Atmospheric Administration. The resulting retreat of sea ice is creating new 

possibilities for resource extraction, tourism, fishing, and shipping routes between the Atlantic and Pacific. 

Unpredictable ice floes, remoteness, and harsh conditions will limit operations in the Arctic over the 

coming decade, but disputes over unresolved maritime boundary claims, military posturing, and economic 

activity could increase as the Arctic opens.

 Contention over Russia’s claim to 1.2 million square kilometers of Arctic shelf, which Moscow 

submitted to the UN in August 2015, could increase friction with rival claimants, including Denmark 

and Canada.

 Opening waterways have encouraged a Western cruise line to plan the first month-long cruise 

through the Northwest Passage this summer, carrying more than 1,000 passengers. Maritime 

authorities have cautioned that the voyage is high-risk in terms of navigational security and because 

of limited search and rescue capabilities.

 Significant thawing of Arctic and sub-Arctic permafrost could rupture the China–Russia crude oil 

pipeline—an important shared resource between the two countries—and could threaten the integrity 

of other Russian pipelines, according to recent scientific studies.

Political disputes could arise over climate change responses and policies. Some adversely affected

countries may seek relief through international judicial mechanisms. Countries not meeting their pledges 

to reduce carbon emissions may face heightened political pressure and eventually punitive actions—such 

as sanctions or pricing carbon into trade—even though the pledges now are voluntary, with no current 

enforcement mechanism.

Unilateral efforts by countries or groups to test or deploy geoengineering—a largely theoretical field 

exploring how the climate might be modified intentionally through methods such as injecting aerosols 

into the stratosphere or chemically changing the reflectivity of clouds—would almost certainly heighten 

regional or international tensions, especially in the absence of multilateral frameworks or institutions to 

govern such activities. Some forms of geoengineering experimentation are probably within the financial 

and technical capacity of some major powers and individuals, although there are fundamental scientific 

uncertainties about the efficacy and possible unintended consequences of such methods.

 If, for example, geoengineering methods suppressed global temperatures below the point assumed to 

bring dangerous climate change, such efforts would almost certainly need to be sustained and 

probably would alter global weather patterns, benefitting some regions at the expense of others, 

according to the National Academies of Science.

Adverse Effects on Food Prices or Availability

More frequent extreme weather events, ranging from droughts to extreme rainfall, would significantly 

threaten agricultural production. Moreover, long-term climate trends—such as more very hot days, 

changing precipitation patterns, and poleward shifts of tropical clouds—along with constraints on land, 

water, and energy also put upward pressure on food prices. We judge that in countries with weak political

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institutions, climate-induced threats to food security sharpen the risk of social disruption, migration, or 

large-scale political instability.

 The terrorist group Al-Shabaab exploited the 2011-13 famine in Somalia to coerce and tax 

international aid agencies, and it withheld food from those it deemed uncooperative, according to

Human Rights Watch.

 In 2015, insurgent groups in northern Mali exploited deepening desertification, worsened by 

persistent drought, to enlist locals in a “food for jihad” arrangement.

Heatwaves threaten livestock directly and also reduce fertility, decrease milk production, and make them 

more vulnerable to disease. Droughts, wildfires, and extended periods of reduced precipitation threaten 

pasture and food supplies, indirectly threatening livestock.

 In Australia, the world’s third-largest beef exporter, the direct and indirect impacts of heatwaves have 

contributed heavily to a decline in cattle stocks to the lowest levels in 20 years.

Increased ocean temperatures and more frequent and more intense storms will increasingly threaten 

fisheries, many of which are already under stress from overfishing and pollution, according to the UN 

Food and Agriculture Organization. As oceans become more acidic as they absorb atmospheric carbon 

dioxide, ecosystems on which fish and other sea life depend are further jeopardized.

 Warm ocean temperatures have helped fuel an unprecedented, ongoing bloom of toxic red algae 

along the southern coastline of Chile since early May 2016. The damage to Chile’s important 

aquaculture industry has sparked protests from fishermen, who have blocked access to ports over

what they view as inadequate governmental compensation for their losses.

Increased Risks to Human Health

Extreme heat increasingly will contribute directly to deaths from cardiovascular and respiratory disease

across the globe, particularly among the elderly, according to the US National Institutes of Health. High 

temperatures also raise the level of ozone and other air pollutants that exacerbate cardiovascular and 

respiratory disease. Rising sea levels and severe weather events will increasingly threaten medical 

infrastructure and other essential services, according to the UN World Health Organization.

 The 2003 heatwave in Europe fueled their hottest summer on record since at least 1540, and 

contributed to more than 70,000 deaths, according to a peer-reviewed study by the French Institute 

of Health and Medical Research. Western Russia’s most extreme heatwave in recorded history was in 

2010, causing more than 11,000 deaths in Moscow alone, according to scientists.

 Heatwave-related deaths in South Asia in 2015 numbered 2,500 in India and more than 100 in 

Pakistan. Another intense heatwave beginning in April 2016 produced India’s highest temperature

ever recorded (124°F) and has caused more than 400 deaths so far. 

Higher temperature and, in some regions, more rainfall and flooding are likely to increase the frequency 

of water-borne diseases and diseases transmitted by insects, snails, and other cold-blooded animals in 

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those areas. Extended transmission seasons of important vector-borne diseases are expected across a

potentially larger geographic range, according to the National Institutes of Health.

 For instance, the mosquito Aedes albopictus, which is capable of transmitting a broad range of viruses 

to humans, is likely to live longer in Western and Central Europe in the next few decades because of 

increasing temperatures, according to academic research. In contrast, projected changes on the 

Mediterranean coast of Spain are likely to diminish mosquito survival in that region.

 The Vibrio cholerae bacterium, which causes cholera, thrives in warm, salty waters. Higher surfacewater temperatures and rising sea levels could introduce cholera to previously unaffected areas.

Stress on Military Operations and Basing

Globally, more frequent and intense natural disasters will strain the capacity of US and allied armed forces 

to deliver humanitarian assistance and disaster relief. The US military may be called upon more frequently 

to respond to foreign crises if its counterparts in affected countries are overstretched, unable to handle 

their own crises or those in their neighborhood.

We also judge that rising sea levels, flooding, droughts, higher temperatures, and more frequent extreme 

weather events will increasingly threaten military capabilities and facilities on both US and foreign 

territory, including military bases and training ranges.

 Continued reduction of sea ice will increase the importance of the Arctic as a domain for military 

access and operations, although the environment there will remain challenging and unpredictable.

Implications for Investments and Economic Competitiveness

Past and anticipated extreme weather events may discourage investment in regions deemed particularly 

vulnerable. Infrastructure will be increasingly threatened by more extreme conditions in the near future,

and freshwater from aquifers will be increasingly jeopardized by saltwater intrusion. Expectations of 

future losses will almost certainly increase insurance premiums and payouts, and insurance rates may 

increase well before real effects are felt in regions deemed vulnerable.

 The chairman of Lloyd’s of London, one of the world’s largest and most influential insurance markets, 

has stated that climate change is its primary concern. Allianz, Europe’s largest insurer, has said that 

climate-change-driven losses from extreme events could increase by 37 percent within a decade.

The financial burden of responding to emergent climate trends and severe weather events, including the 

cost of efforts to mitigate greenhouse gas emissions, will reduce financing available for other investments, 

except in cases where those climate investments lead to green-growth opportunities. Increasing heat 

stress is likely to adversely affect agriculture, manufacturing, and other sectors requiring physical labor 

and could significantly contribute to GDP loss.

 Low-income countries are less equipped to rebound from the economic setbacks caused by extreme 

weather events, and an increase in the frequency of these events could contribute to or even push 

some people into poverty.

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Potential Climate Discontinuities and Secondary Surprises

While current climate models project long-term increases in global average surface temperatures, climate 

scientists warn that more sudden, dramatic shifts could be possible, given the complexity of the system 

and analogs in the climate record. Looking back over the past 100,000 years, the earth’s climate 

periodically has undergone extreme shifts, sometimes in as little as a decade. Such abrupt swings can 

occur in complex systems when seemingly small shifts in the forces in play suddenly trigger dramatic 

nonlinear change, such as when a slight drop in temperature can suddenly turn water into ice. A body of 

scientific research indicates that the current rate of increase of carbon dioxide in the atmosphere is the 

highest in perhaps as long as 66 million years, sea levels are rising faster than in the past 2,700 years, and 

the oceans are acidifying more rapidly than in the past 56 million years.

Many climate scientists warn that the risk of abrupt climate change—currently low—will increase over the 

next several decades and beyond. We judge that the possibility of abrupt climate change cannot be 

discounted over any timeframe because research has not identified indicators to forecast potential 

tipping points and other thresholds. Even if sudden shifts in the climate do not materialize, gradual 

shifts in climate could nonetheless spark surprising secondary effects—such as a massive release of gases 

from melting permafrost, persistent megadroughts, extreme shifts in critical ecosystems, emerging 

reservoirs of new pathogens, or the sudden breakup of immense ice sheets. The national security 

implications of such changes could be severe.

(continued next page)

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Effects of Climate Change on US National Security: Possible Timeframes

The major forces driving climate are understood well enough for models to forecast climate trends for 

general regions, but complex interactions in the climate system, modeling uncertainties, and human 

choices make it difficult to project when and where specific weather and climate effects will most 

significantly affect national security. Most scientists expect that climate change generally will exacerbate 

current conditions—for example, making hot, dry places hotter and drier.

Future climate conditions could be altered significantly by government policies, industrial practices, or

consumer behavior regarding greenhouse gas emissions. That said, IPCC scenario modeling suggests that 

aggressive environmental policies would not begin to slow the growth of global average surface 

temperatures for another 15-20 years because of the lag time for complex global climate systems to 

respond to changes in human behavior (see chart below).

The long time horizon for climate change makes for different assessments of the national security 

implications for different periods. We make these assessments based on the IPCC’s findings of projected 

climate change and our understanding of the possible pathways by which climate change affects national 

security.

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At present, the growing implications for humans of extreme weather events suggest that climate-change 

related disruptions are well underway (see following map for illustrative examples of recent extreme 

weather events). Individual weather occurrences remain difficult to attribute entirely to climate change, 

however.

Looking forward, we assess that during the next five years national security risks linked to climate 

change will arise mostly from distinct extreme weather events, especially in regions with weak 

governance, poor living conditions, or persistent conflict that limit the capacity of governments and 

societies to cope with additional stress. When extreme events occur where they have not before, that too 

will be disruptive, even for advanced industrial countries.

We assess that during the next 20 years—in addition to increasingly disruptive extreme weather 

events—climate change effects will play out in broader, systemic ways, such as more acidic oceans, 

degraded soil and air-quality, and rising sea levels, resulting in sustained direct and indirect effects on US 

national security. Weather events of modest severity will be disruptive when their impacts are 

compounded as part of a rapid sequence or in clusters.

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