The concept of climate change as a “threat multiplier” emerged in 2007, primarily through the work of the CNA Military Advisory Board, which highlighted how climate change exacerbates existing security threats, such as poverty, environmental degradation, and political instability. This term gained traction in U.S. legislation, notably in the Global Climate Change and Security Oversight Act and the Lieberman-Warner Climate Security Act, both of which emphasized the implications of changing precipitation patterns on global stability.

The 2014 Quadrennial Defense Review marked a significant turning point, explicitly characterizing climate effects as threat multipliers and detailing various global dynamics aggravated by climate change. This framing was subsequently adopted in Department of Defense (DOD) documents, including the DOD Climate Change Adaptation Roadmap and the National Security Implications of Climate-Related Risks report. The U.S. National Security Strategy of 2015 also recognized climate change as an urgent threat to national security.

The concept has evolved, with practitioners and scholars now viewing climate security and resilience at the intersection of defense, development, and diplomacy—often referred to as the “3 Ds,” with Disaster as a potential fourth D. This framework aims to inform better strategies for addressing climate-related risks.

Internationally, the term has been embraced by various organizations and countries, leading to a broader community of practice focused on climate security. The U.S. government has increasingly integrated climate considerations into its foreign policy and national security strategies, as evidenced by Executive Order 14008, which emphasizes the climate crisis’s centrality to U.S. foreign policy.

In conclusion, the “threat multiplier” concept has become a key phrase in characterizing climate security risks, facilitating a bipartisan coalition of policymakers and practitioners dedicated to addressing the implications of climate change on security. The ongoing dialogue around this concept continues to shape perspectives within the defense community and beyond, highlighting the urgent need for collective action in response to climate-related challenges.