There are several important linkages among environmental hazards and crises caused (at least in part) by human-caused global warming, and both homeland security and national security risk analysis and practice. Increasingly robust research has demonstrated (1) anthropogenic climate change and its interaction with other human environmental pressures (population, pollution, and resource consumption growth); (2) worsening climate disruption patterns and disaster projections, showing long-range risk to the very survival of human civilization; and (3) links among environmental hazards, human economic and political instability, and development of political violence. This paper discusses how and why environmental security (ES) and homeland security (HS) are linked, including the threat-multiplying aspect of climate disruption risk factors; briefly contextualizes their growing interconnectedness in both theory and policy practice; and reviews some of what is most recently known about the science of climate disruption. It reviews disaster mitigation and resilient adaptation policy implications of climate variables such as extreme heat and drought, extreme storms, sea level rise, ocean ecosystem damage, and food and water crises. Most U.S. government security-related organizations now incorporate HS-ES mission statements, but current environmental security risk management and planning investment is insufficient, and burdened by political obstruction and costly scientific uncertainties.