Global Crisis: War, Climate Change and Catastrophe in the Seventeenth Century by Geoffrey Parker is a very ambitious attempt to summarize and contextualize the various inter-related famines, epidemics and wars that plagued most parts of the world in the middle decades of the 17th century. It's not easy to give a brief summary of 700 pages covering such a broad range of issues but I'ii try.
I guess the starting point has to be the state of the world as the 17th century began. With exceptions, the 16th century had been a period of benign climate, long periods of peace and stability and hence population growth with a great deal of marginal land being brought into cultivation. Given pre-industrial technology some kind of correction was probably inevitable but maybe not one that might have reduced world population by a third and affected all parts of the globe with the exception of New England and Japan.
So what happened? First, there was a dramatic cycle of global cooling that devastated crop yields directly in the temperate zone and led to severe drought in the tropics. A reduction in sunspot activity, and hence solar energy reaching earth had a direct effect but also dramatically increased the incidence of El Nino years causing widespread drought and flooding but also leading to a major shift in the weight distribution of the Pacific Ocean, which in turned seems to have led to increased volvanic activity, which reinforced the cooling effect.
Human agency seems to have directly reinforced the climactic impacts. In Europe, the 80 Years War, The 30 Years War, The War of the Three kingdoms, the disintegration of the Polish-Lithuanian Commonwealth and major revolts in Naples, Portugal and Catalonia all contributed to a cycle of rapacious soldiery being billeted on starving populations with a good chunk of religious hatred thrown in. In China the 60 year struggle between Ming and Qing had similar effects as did religious turmoil in the Ottoman Empire and dynastic revolts in India. In Africa the desertification of the Sahel caused population migration that drove the wars that provided the raw material for both the Mediterranean and Atlantic slave trades. No one cause explains all these events of course but Parker posits the rise in "composite states"; where one monarch ruled multiple people of different customs, as one factor. The monarchical impulse to impose uniformity leading to trouble and an inability to compromise. Charles I's attempt to impose Laud's Prayer Book on Scotland would be but one example. A general tendency for such monarchs to tax their subjects in polity A so that those in polity B could be brought to book seems to have been a general source of discontent made intolerable by prevailing economic conditions.
The evidence Parker marshal's is impressive both in relation to the human record and the natural record. Rarely can so much tree ring data have been correlated with so many primary sources!
The bottom line is that governments coped very badly except in Tokugawa Japan, where the government seems to have learned from the catastrophes of the previous century and invested in famine amelioration rather than foreign war and New England where a sparse European population largely avoided the epidemic diseases that hit most of the Americas and was able to expand very rapidly.
The question it raises of course is that if 17th century governments dealt so badly with climate change can we expect 21st century ones to be more prescient? The answer to that of course is obvious. The ray of hope is that if the world can recover once from a combination of natural factors and gross governmental ineptitude perhaps it can do so again. Even if it takes half a century of Hell to do so.