Overall, the links between climate and national security are indirect, involving a complicated web of social and political factors. Climate effects discussed earlier in this report, including food and water security, have the potential to drive national security concerns. Although international cooperation is more typical than conflict in confronting water security issues, conflicts over water issues may become more numerous as droughts become more frequent. In addition, famine and food scarcity have the potential to cause international humanitarian issues and even conflicts, as do health security issues from epidemics and pandemics (also see previous section). These impacts from climate change may present national security challenges through humanitarian crises, disruptive migration events, political instability, and interstate or internal conflict. The impacts on national security are likely to be presented abruptly, in the sense that the eruption of any crisis represents an abrupt change.
An example of an abrupt change that affects the national infrastructure of a number of countries is the opening of shipping lanes in the Arctic as a result of the retreating sea ice. There are geopolitical ramifications related to possible shipping routes and territorial claims, including potential oil, mineral, and fishing rights. The Arctic Council, which was formerly a relatively unknown international body, has become the center of vigorous negotiations over some of these issues. This is a change that is occurring over the course of a couple of decades, well within a generation.
It is important to recognize that abrupt climate change as it affects national security presents opportunities as well as challenges. For example, the United States is still heavily dependent on foreign oil, despite the recent increase in fossil fuel supplies made available by hydrologic fracturing of source rocks. Also, greenhouse gases enter a shared and well-mixed atmosphere, and thus solutions will afford an opportunity to enhance international cooperation and build transparency and trust among nations.
While it may not be possible to predict the exact timing of abrupt climate events and impacts, it is prudent to expect that they will occur at some point. The NRC report on Climate and Social Stresses (NRC, 2012b) recommends a scenario approach for preparing for abrupt climate impacts that may have ramifications for national security. The report recommends the use of stress testing, where “a stress test is an exercise to assess the likely effects on particular countries, populations, or systems of potentially disruptive climate events.” The material presented in this report could inform these types of stress tests by presenting the types of abrupt climate impacts that are possible (see Chapter 2 and Table 4.1).