One of my favorite quotations is usually attributed to Ambrose Bierce or Mark Twain, and it'd be appropriate for either of them, though it's probable neither said it. I'll pass it along, though: "War is God's way of teaching American geography" — and suggest a variation: «Planning for war is a pressing invitation to learn some history.»
Unlike many in their civilian leadership — Donald J. Trump for one — U.S. war planners and others represented in the figure of speech "the Pentagon" are looking very seriously at climate change as "a national security threat," and some quick history lessons can help drive home the point that they have good reason to do so.
The major history lesson is in a book like The Great Warming (2008), which has as its subtitle Climate Change and the Rise and Fall of Civilizations. But Brian Fagan's book was researched and written recently, and he relates "The Great Warming" — the Medieval Climate Anomaly of ca. 800-1300 C.E. — very specifically to global warming nowadays, and stresses its threat of extended droughts. What might be more persuasive is some historical work done a good while before our time and therefore innocent of our current political debates — and on a topic very directly relevant for one national security issue.
So here is an excerpt from James W. Thomson and Edgar N. Johnson's An Introduction to Medieval Europe: 300-1500 (New York: Norton, 1937) — again 1937 — from Chapter 7, "The Empire of the Arabs" (I have marked but left unchanged locutions neutral in 1937 but probably discourteous today). The topic is the Muslim conquests of what Christians call the 7th century and a bit thereafter, usually explained by both Muslims and historians from Christendom in religious terms. Thompson and Johnson have a different take.
From these small beginnings at Medina the Arab church-state [sic] spread with prodigious rapidity. Within fifty years after Mohammed's death [in 632 C.E., 11 A.H.] it had conquered Persia, Egypt, Syria, and Palestine. Within one hundred years it had spread to the frontiers of India to the east, and to the west had swept across North Africa through Spain and beyond the Pyrenees. [Usual explanation for such success (an act of God for the faithful; for secular historians) political cohesion combined with, and mutually reinforcing, religious fanaticism. …]
The facts are quite otherwise. In the first place, it is impossible at this early date to speak of Mohammedan [sic] fanaticism, except possibly in isolated instances. Mohammed himself in his conquest of Mecca displayed a fierce enough zeal; but in general no such militant intolerance as, for example, characterized the struggle of Christianity against paganism characterized Mohammedan expansion. The fanaticism of Islam is that of much later converts, and even so Mohammedanism has normally been marked in practice by its tolerance. […]
In the second place, it is impossible to speak of Mohammed's creating any such thing as Arab unity, nor can it be supposed that in any substantial way the nomadic Arab tribes suddenly consolidated into a unified state after his death. […] [163-64]
The expansion of the Arabs is best understood in the light of previous movements out of the desert into the neighboring Fertile Crescent. These were constant phenomena, to be explained by the vicissitudes of climactic conditions, which always drove nomadic peoples onwards. It is now known that for a long time previous to Mohammed there had been a gradual movement of Arabs into the adjoining Byzantine and Persian empires. […] The [Arabian] peninsula itself was experiencing a periodic desiccation, which made life within it ever more unbearable and drove its inhabitants to seek relief elsewhere. It seems, accordingly, highly probably that what occurred would have happened [given the weakness of Persia and Byzantium after prolonged war (and plague)] even without Mohammed and Islam. (166).
A couple things here. First, when you hear people talk about "Islam vs. the West," tell them that to say nothing of geography — Islam has been or remains the dominant religion in regions clearly in the western part of the Old World — there is the commonplace in European history that Islam joins the Greco-Roman, Judeo-Christian, and Germanic streams in the making of Medieval Europe. Second, whether you accept the theory in Thompson and Johnson or not, note that in 1937 historians could find plausible that at least local long-term weather — "a periodic desiccation" — was a key factor in one of the most important political/military events in world history: the Islamic conquests and expansion leading to "The Empire of the Arabs" and, arguably, the final push taking western Europe from Late Antiquity into the early Medieval.
Two common figures of speech for the countries on and around the Arabian Peninsula are "the Middle East" — how you'd see things if you're looking out from the British Isles toward your "Far East" — and "tinderbox": from a literal "box containing tinder, flint, a steel, and other items for kindling fires," and having as its tenor, "a potentially explosive place or situation."
"Tinder" refers to dry slips of wood that you use for starting fires; "desiccation" means a drying out; in the Middle East and large areas in Africa, desiccation could get to desertification: taking dry areas to outright desert.
And people will yet again move out, and there are few places to go nearby that (1) can support them and (2) do not have a lot of people already. Now add to that a large number of small-arms in the world and a fair number of people willing and able to sell not-so-small arms or teach how to make IEDs, and add to that the fairly recent and still vigorous development of Fundamentalism in Christianity and Islam, and fanatical varieties of the big three monotheisms and even in such fanaticism-resistant traditions as Hinduism and Buddhism.
Take a tinderbox, add heat, wait for a spark. Or, change the figure of speech and let ISIS evolve into something more sophisticated, add a charismatic leader (a modern Saladin), oppose it to a Christendom relearning fanaticism, tell them all "God wills it!" (Deus vult!), and be prepared to learn geography.
If very unlucky, you'll become and expert in geography and in the history of downright fascinating times parallel to the transition from Late Antiquity to early Medieval, known some places in Europe as "the Dark Ages."