This statement is vague and unconvincing. The armed forces are among the most conservative government agencies since most federal employees self-select into agencies whose mission they support. Also, the office of Secretary of Defense has historically been dominated by conservatives. What would be the political motivation for the largely conservative Department of Defense to declare climate change a threat to our national security?
This statement is even more vague and unconvincing. Every multinational oil and gas company has an enormous incentive to disavow climate change. Their trade associations do, and their investors consistently vote down climate-related measures. Yet all of the world's largest producers are on record declaring climate change is a critical imperative. None of the American companies retracted their statements when Trump -- a climate change denier -- took office. This is to say nothing of the foreign companies who aren't subject to the whims of elected officials. Instead, these companies have continued to invest billions of dollars in research and development of renewable energy sources.
Politicians are the biggest hypocrites on earth. As you've mentioned, they play by an entirely different set of rules from the rest of us. They're probably the last people I would look to for guidance on this issue.
In my estimation, the easiest way to tell if these policies are good and necessary is to look at those who truly understand the underlying science. The people who subscribe to the rigor of the scientific method behind the findings. The subject matter experts: climatologists, meteorologists, geologists, oceanographers, etc. Roughly 90% of them are telling us that climate change is real. JMHO, but I'm always a bit shocked to see how easily people reject that number because of their personal political beliefs. You demand critical thinking, but then discount the professional judgment of those best equipped to provide it.
The only scientist I know personally -- an oceanographer -- shares a single hybrid vehicle with his wife. I never knew about the so-called "Pacific Garbage Patch" until he told me about it. He advocates for the standard reduce/reuse/recycle lifestyle. Fortunately, he's not pushy about it, so I haven't had to punch him in the face. Anyway, take that for what it's worth.
As I suggested in the OP, it wasn't my intention to turn this into a political debate. I'd prefer to step away from that. I was more fascinated with the idea of what climate change could possibly mean for us, our lifestyles, and our future.