It is expensive, heavily subsidized (a hidden tax), unreliable, causes negative health impacts, kills large birds of prey and bats and can be maddening to people who live nearby. They're bad for the military too.
Hypothetical vulnerability analyses are in no sense realistic threat assessments.
Any assertion that global warming is putting our national security at risk is ill-informed and contradicted by clear scientific evidence.
President Obama has issued an executive order directing the Department of Defense (and all other federal government agencies) to make preparing for global warming impacts a top priority, and treat climate change as our most serious national security threat.