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.