Climate collapse and pandemics: the fall of Rome

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From the Princeton University Press description:

"Interweaving a grand historical narrative with cutting-edge climate science and genetic discoveries, Kyle Harper traces how the fate of Rome was decided not just by emperors, soldiers, and barbarians but also by volcanic eruptions, solar cycles, climate instability, and devastating viruses and bacteria.

He takes readers from Rome’s pinnacle in the second century, when the empire seemed an invincible superpower, to its unraveling by the seventh century, when Rome was politically fragmented and materially depleted.

Harper describes how the Romans were resilient in the face of enormous environmental stress, until the besieged empire could no longer withstand the combined challenges of a “little ice age” and recurrent outbreaks of bubonic plague."

This is a highly readable, even exciting narrative which situates the Roman Empire within the climate cycle of the:

• Roman Climate Optimum (200 BC - 150 AD)
• Late Roman Transitional Period (150 - 450)
• Late Antique Little Ice Age (450 - 700).

Agrarian societies are highly susceptible to climate deterioration and its attendant woes of famine, plague and attack from similarly-stressed 'barbarians'. Consequent depopulation subverts both the economy and the military. The later Empire was, as Harper demonstrates, constituted as a sequence of structural-political responses to increasingly debilitating challenges. In the end it was all too much.

This is by far the best, and most compelling account I have read of the dynamics underlying the fall of the Roman Empire (and also the rise of Islam, which brought the final coup de grace). Another case where climate science and paleogenetics are revolutionising history and archaeology.

One small criticism: Harper uses anachronistically the categories of capital and wage labour. But Rome was not capitalist, it was mercantilist, dominated by a mode of production based on ubiquitous slavery as Harper explains in great detail.

Holocene nostalgia

Who cares what a non-sentient iceberg thinks?

Matt Ridley has an opinion piece in The Times today:

"Let’s go back a little further, to the Middle Ages. It used to be argued by some that the “medieval warm period” of about a thousand years ago, when mountain glaciers retreated, vines grew further north and Iceland was widely cultivated, was confined to Europe. We now know from multiple sources of evidence that it was global. Tree lines were higher than today in many mountain ranges, for example. Both North Pacific and Antarctic Ocean water temperatures were 0.65C warmer than today.

"Go back yet further, still within the current interglacial period, to the so-called Holocene Optimum of 6,000-9,000 years ago. Ocean temperatures were up to two degrees warmer than today, the Arctic Ocean was nearly or completely ice-free at the end of summer in many years, and the boreal forest in Siberia extended 150 miles further north than today. July temperatures were up to six degrees warmer than today in the Siberian Arctic.

"Was this Holocene Optimum a horrible time of droughts, storms, disease and famine? Not especially. It was the period in which agriculture spread rapidly across the globe from five or seven centres of invention. Abundant rainfall in Africa led to lakes in the Sahara with crocodiles and hippos in them, surrounded by green vegetation in the monsoon season."

As far as I can make out, global warming works to some countries' advantages and not to others. Zones susceptible to weather-related economic activity (agriculture, tourism) move around as do many areas where people today have ended up living.  The losers make more noise than the winners. North-West Europe (cold, damp) seems a likely winner. Shame our liberal hand-wringing prevents us from enjoying it.

Still, something must be done. I'm in the realpolitik camp: developing countries will carry on burning fossil fuels; greenhouse gas ratios will continue to rise. There are loads of things which can be done to mitigate the results and to develop alternative, cleaner and cost-effective power supplies - it's called R&D.

The point Matt Ridley elides is that the cost of moving our global infrastructure to accommodate the Holocene Optimum, nice as it sounds, would be enormous - both in economic transformation and population migration.

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PS. Did you like the picture above, drawn with my Kids Paint Free app? (Similar). I can also recommend Twilight for those dark evenings when you welcome sleepiness, and Electric Sheep for awesome inspiration (you got the Philip K. Dick reference, right?).