Historically, climate change does impact the military
Before we get too distracted, let's remember the chain of events that eventually led to the fall of the Roman Empire. A lot of things were involved, of course, but the various hordes moving west out of Central Asia into Roman territory was a significant factor by any assessment or interpretation.
The tribes were migrating west because of a change in the ability of the land in Central Asia to support crops, which in turn supported the horses and nomads.
This change in the carrying capacity of the land was due to a 2-3 degree change in year-round average temps.
If climate change was a significant factor in the fall of the Roman empire, shouldn't the guardians of the U.S. pay attention to climate change?
Climate change around the Aral sea in the past 20-30 years provide a great case study in impact of humans on the environment. The secondary and tertiary effects are of special interest, particularly the issues surrounding potable water.