National Intelligence Council

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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 governments could be so preoccupied with managing the effects that they have little time or energy left to engage on broader foreign policy issues. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”