Politico had an article yesterday talking about the groups of veterans, named Operation Free, who are taking a bus tour around the country and making a case for action on climate change. Here is an article about the bus tour coming to Lincoln, Nebraska (at 6:15 am? will that really bring out the crowds?).
In some ways, I'm strongly in favor of this. Climate action is necessary, and whatever argument you need to make in order to pass it through the Senate should be made. However, nuance doesn't come through in political debates. By groups and politicians saying that climate change will cause wars, we risk overstating the argument.
It is demonstrable that climate change is a national security threat. Both the CNA and the National Intelligence Council have convincingly made that case. However, I am also slightly afraid that you could make that argument about any number of intractable global problems: poverty as a threat to national security, disease as a threat, inequality as a danger, even just general unhappiness. I've talked about the need to be prudent before.
That's why the IISS is working hard to more closely quantify the global security threats of cliamte change. The problem is that nothing is perfectly linear in this world. Climate change may cause water shortages, which may cause food shortages, which may cause famine, which may cause resource wars. This is a plausible and convincing chain of events, and there are other possible linkages. However, its very difficult to say that prudent action couldn't stop that chain at some point along the way.
I'm convinced, however, that addressing climate change is one of the most important challenges of our generation. Unmitigated, its effects over the long-term could be genuinely catastrophic. That should be reason enough to address this threat. If, politically, you have to invoke the military and call it a threat to 'national security', then I guess that's a stronger argument to make to Americans than calling it a threat to Polar Bears.