December 07, 2008
Roman Empire Felled By Declining Rains?

Did declining precipitation bring down the Roman and Byzantine Empires?

MADISON The decline of the Roman and Byzantine Empires in the Eastern Mediterranean more than 1,400 years ago may have been driven by unfavorable climate changes.

Based on chemical signatures in a piece of calcite from a cave near Jerusalem, a team of American and Israeli geologists pieced together a detailed record of the area's climate from roughly 200 B.C. to 1100 A.D. Their analysis, to be reported in an upcoming issue of the journal Quaternary Research, reveals increasingly dry weather from 100 A.D. to 700 A.D. that coincided with the fall of both Roman and Byzantine rule in the region.

The researchers, led by University of Wisconsin-Madison geology graduate student Ian Orland and professor John Valley, reconstructed the high-resolution climate record based on geochemical analysis of a stalagmite from Soreq Cave, located in the Stalactite Cave Nature Reserve near Jerusalem.

They didn't have diesel fuel to power irrigation pumps. They didn't have diesel bulldozers, trucks, steel, and concrete to construct massive water reservoirs and dams. They didn't have weather satellites or drought resistant crop strains. We have all those things and more. So we are more insulated (though not entirely so) from climate changes.

Regardless of whether humans are causing huge climate changes the climate will change. Look back over the last five hundred years and we see pretty big changes in climate. We will see more big changes. The Roman Empire and the Byzantine Empire went through big climate changes.

Their detailed climate record shows that the Eastern Mediterranean became drier between 100 A.D. and 700 A.D., a time when Roman and Byzantine power in the region waned, including steep drops in precipitation around 100 A.D. and 400 A.D. "Whether this is what weakened the Byzantines or not isn't known, but it is an interesting correlation," Valley says. "These things were certainly going on at the time that those historic changes occurred."

Today we are less dependent on the weather. Our biggest vulnerability is in energy supply. With enough energy we can desalinate and pump water long distances. If (or, rather, when) we develop the technologies needed to produce non-fossil fuels energy sources at low cost then I think we will be able to insulate ourselves (at least in most developed countries) from most climate changes.

Granted, a new ice age would require evacuation of some regions and countries. The melting of the polar ice caps would require other evacuations. But the richer we get the more easily we can adapt to climate changes. Given sufficient capital and energy we can handle anything short of a severe ice age and still maintain an industrial civilization.

Melting ice caps are avoidable with climate engineering. But food production could be maintained with sufficiently large amounts of cheap energy. We can desalinate water and pump it great distances. We can genetically engineer crops to handle different climates.

If we build enough nuclear reactors we can stop using coal for baseline electric power and also have plenty of energy to use to keep food production up in case of climate change. Also, if we go into a cooling period some day we could add coal electric to supplement the nuclear for heating and for crop production.

Share |      Randall Parker, 2008 December 07 07:57 PM  Climate Trends

Fat Man said at December 7, 2008 10:37 PM:

The collapse of the Roman empire of the is one of the mightiest events ever, but we need to appreciate that the phrase encompasses a span of more than a thousand years.

The cited time frame of 100 A.D. and 700 A.D. or 2nd through 7th Centuries CE (Christian Era) does not show a pattern of monotonic decline, or even the inevitability of collapse.

Of the beginning of this period Gibbon famously writes: "In the second century of the Christian era, the empire of Rome comprehended the fairest part of the earth, and the most civilized portion of mankind." The political chaos that began with the reign of Commodious was resolved after a century by Diocletian.

At the beginning of the the fourth century Constantine, one of Diocletian's successors, attempted to resolve the administrative problems of the enormous empire by founding Constantinople (modern Istanbul), to be the capital of the eastern, Greek, half of the empire and legitimizing and co-opting the Christian church. Unfortunately, the empire was plunged into incessant civil wars by disputes among his heirs and would be usurpers.

In the fifth century Germanic invaders dismembered the western, Latin, half of the empire [remember we are talking about the climate of the eastern half]. Most Europeans and Americans think of that as the fall of the Roman Empire, but that is far from the truth. The eastern half continued on for almost a thousand years thereafter. By the middle of the next century, Justinian reconquered much of the lost territory in Italy and North Africa. He also built Hagia Sophia in Constantinople, which still stands, and codified the Roman Law. Most European countries legal codes are based on Justinian's.

The Eastern Roman [a/k/a Byzantine] Empire warred with the Sassanian Persian Empire which ruled what is now Iraq and Iran, for most of the fifth and sixth centuries. Evidence of human stupidity, but not climatic disaster.

In the seventh century, the Arabs erupted under the flag of Islam. They were able to conquer the Byzantine possessions in the Levant and North Africa as well as Spain and the Persian Empire. These conquests assembled an empire as large as or larger than the Roman. Again hardly proof of climatic disaster. Nor is the fact that the uncivilized Arabs were able to best Byzantine and Persian armies proof of climatic disaster. Until European countries developed armies based on gunpowder weapons, this sort of thing happened fairly regularly. The Mongols are an even more spectacular example.

The Arabs were not able to penetrate the core Byzantine territory of Anatolia and the Balkan peninsula. By the ninth century the Byzantine empire solidified its grip on those territories and the Black Sea littoral and had its peak years over the next few centuries. Not until the late in the eleventh Century did the combined pressures of the Crusaders from the west and the Turks from the east cause the Byzantine Empire to assume a downward course. Even then, it was not finally destroyed until 1453.

There is a lot about politics, religion and social organization to contemplate in the history of the Roman Empire. I just do not see much to think about climate.

cancer_man said at December 8, 2008 6:11 AM:

"These conquests assembled an empire as large as or larger than the Roman."

Many miles wide but ony several inches deep. The climate angle is interesting but were unfortunately going to start to hear about how climate change brought down the Roman Empire. And people will say this with straight faces.

Fat Man said at December 8, 2008 8:49 AM:

"Many miles wide but ony several inches deep."

The almost immediate collapse of the Caliphate into civil war is interesting, but the time frame is 1) beyond 700 A.D. cited above, 2) more a commentary on the fragility of Islamic political institutions -- something we can see in or own time, and 3) happened far more quickly than any climate change.

Bob Hawkins said at December 8, 2008 9:30 AM:

The most immediate advantage we have is the ocean freighter. That allows food to be shipped from the regions where the climate improves to regions where it gets worse. That adjustment takes only months.

Transportation in general is key to preventing famine. Which is why disruption of transportation, by war, civil unrest or government policy, almost always accompanies major famines.

kurt9 said at December 8, 2008 9:54 AM:

The barbarian hordes (Germanic tribes) that knocked off Rome were driven into the Empire from Central Asia because of climate change. It got colder and the ancestral homeland of the Germanic people was no longer hospitable. So, they had to leave and the only warm land available was the Empire. Also, the Sahara changed from grasslands into a desert during this time as well.

CM Collins said at December 8, 2008 10:27 AM:

"Melting ice caps are avoidable with climate engineering."
On that note, how about this idea:
"Glacial advances and retreats started about a million years ago, pretty much when the Isthmus of Panama came up out of the water. After the Isthmus closed, the trade winds continued to evaporate water off the Atlantic and dump it as rain on the Pacific... The water vapor transport across Panama is roughly the size of the Mississippi River; Atlantic water gets saltier and Pacific water becomes more dilute. As salty Atlantic water gets to the Arctic, and especially to the Antarctic, it becomes the densest ocean water and sinks to the bottom. Eventually the cold, salty, dense water fills the bottom 90 percent of the world ocean. Only the uppermost 10 percent of the ocean is available for transporting heat from the equator toward the poles. So how could we prevent further glacial advances? You got it. Move seawater across Panama.
"We dig two sea-level canals across the isthmus. Panama has twenty-foot tides on the Pacific side, almost no tides on the Atlantic side. We put flap gates on the Pacific ends of the canals to make one canal flow from Pacific to Atlantic when the tide is high and the other canal flow from Atlantic to Pacific at low tide. In a few hundred years, we wipe out the Atlantic-Pacific salinity difference. The tropics are not as hot, the poles are not as cold, it is San Diego everywhere...."
Deffeyes, at 171-2,

Dave said at December 8, 2008 12:13 PM:

Thats not exactly right Kurt, the Hun came from central Asia but many Germanic tribes existed in the region that is now Germany before the arrival of the Hun. The Romans never took all of northern Europe.

I thought the Roman empire collapsed largely because they had started using lead pipes for their water supply which damaged fertility of the noble classes while at the same time the number of slaves and none Romans in the exmpire was rapidly increasing?

Fat Man said at December 8, 2008 9:42 PM:

"The barbarian hordes (Germanic tribes) that knocked off Rome were driven into the Empire from Central Asia because of climate change."

Yes but they conquered the Western Empire, not the Eastern (Byzantine) half, which was supposedly climate stressed. The story really does not hold. The reasons must be sought inside the Empire.

"I thought the Roman empire collapsed largely because they had started using lead pipes for their water supply which damaged fertility of the noble classes while at the same time the number of slaves and non Romans in the empire was rapidly increasing?"

Twaddle and repentantly racist too. The empire caused a great movement of peoples and populations. Undoubtedly it was better off for that. The plumbing was a big plus for the Romans. Their cities were much healthier than European cities for the next 15 centuries. The lead content of the pipes is far less important than the fact that they gave the cities clean water supplies. What damaged the noble classes was not good plumbing, but incessant civil wars and political persecutions. By the the time of Constantine it is hard to imagine that any member of the Senate was related to anyone who was a Senator in Julius Caesars time. But, you must remember that the same factors were at work in both the east and the west, but the east lasted a thousand years longer.

Russ said at December 9, 2008 8:49 AM:

Civil wars, political persecutions, and ruinously high taxation. Still haven't seen any of that refuted. (full disclosure, I remain an adherent of the Pirenne Thesis)

The romans, btw, had concrete. Or something so close to it that it makes no difference -- the idea that the Romans, with their still-standing acqueduct ruins (which could have been maintained) couldn't have built massive reservoirs is simply untenable. Stress from climate change? Certainly. As one straw on the camel... but one might as well posit that the Danubian plagues were what did it... we're looking at causes that are far too small compared to the Roman Empire's internal problems.

Dave said at December 9, 2008 10:28 AM:

Racist, Fat man? what do you mean?
I said nothing about race, slavery was never exclusively a black thing, the Romans weren't that fussy, and 'non-Romans' can refer to a lot of people even those from Northern Italy, its not racial.. zzzz

Its not twaddles either its a perfectly legitimate hypothesis that over many generations the elite class of Romans were weakened by it, at least a lot more plausible than global warming.
I don't remember the exact documentary I saw it reported on but a quick google search brought up a lot of links.

Randall Parker said at December 9, 2008 7:44 PM:


The Grand Coolee and similar dams use a lot of rebar in the concrete. The Romans therefore couldn't have built something that big.

Fat Man said at December 9, 2008 10:16 PM:

Yes, racist. The idea that anyone group of human beings has some essence, some quality, whether denominated as genetics, or blood, or terroir, which suits it to govern over lesser breeds is the epitome of racism. It is a particularly American delusion to think that racism is only implicated in relations between Europeans and Africans. The statement that lead "damaged fertility of the noble classes while at the same time the number of slaves and none Romans in the empire was rapidly increasing" is precisely that type of statement.

Yes, twaddle. The Romans used lead pipe for hundreds of years before the empire could be said to have declined. The writings of Vitruvius and archeology attest to it long before the peak of the Empire in the second century C.E. Something that was not a problem for the centuries of Roman history that preceded the peak, cannot be the cause of a decline. Further, "Secrets of Lost Empires: Roman Bath.":

Peter Aicher is an Associate Professor of Classics at the University of Southern Maine and one of the Roman experts who assisted NOVA in the making of the documentary, "Secrets of Lost Empires: Roman Bath." We asked Aicher, author of "Guide to the Aqueducts of Ancient Rome," about the Romans' sophisticated water distribution system, including its elegant aqueducts. Here's what he told us:

AICHER: We don't know much about the system of piping itself, at least in Rome. We do know that most of the pipes were made of lead in that city. This varied, however, depending on the locale. In Germany, for instance, where there was a lot of wood, pipes were made out of wood. Elsewhere they might be terra-cotta.

NOVA: Did they have no sense, then, for the dangers of lead?

AICHER: Actually, they did. At least Vitruvius did. He makes his point by saying, "Hey, look at the people who make these lead pipes!" Apparently, these workers weren't in the best of health.

NOVA: What do you think of the theory that the Roman Empire collapsed because the Romans suffered from lead poisoning?

AICHER: Not much. The Romans did use lead in their pipes. However, two things about the Roman water supply mitigated the unhealthy effects of lead. The first is that the water in the Roman aqueducts rarely stopped running. They had shut-off valves, but they didn't use them much. The water was meant to move. It would flow into a fountain or a basin. Overflow would pour into the gutter and then flush the city.

Today, if you have lead pipes, they tell you to let the water run for awhile before you drink it. That prevents water from sitting in the lead pipes and becoming contaminated. That flushing out happened naturally in the Roman system.

Secondly, a lot of the water, especially in Rome, was hard water. It had lots of minerals in it that would coat their pipes. We often use filtration systems to take some of the minerals out. The Romans didn't have that, so these minerals would encrust and coat the inside of the pipe. That layer of minerals served as a buffer. In fact, the aqueduct channels would gradually accumulate these deposits. Periodically, they would have to chip out all the encrustations.

Randall Parker said at December 9, 2008 10:35 PM:

Fat Man,

The idea that all groups are equally able to maintain complex civilizations is easily disproven by looking around the world. Whether they differ in their abilities due to cultures, religions, genetics, or other causes the fact is that peoples differ in how they run societies. Replace one ethnic group with another ethnic group at the top of a society and that society will change in important ways that either increase or decrease its level of success.

TH said at December 10, 2008 5:12 AM:

Homes built in the US before the forties probably have a fair chance their service line from the main is pure lead. Lead over a short time forms an inert coating where it is exposed, this coating greatly lessens the leaching of lead into the water to the point it is probably insignificant.

Randall Parker said at December 10, 2008 7:14 PM:

CM Collins,

There was a proposal to build a canal at sea level. I forget where. Nicaragua? The goal was to eliminate the need for canals and let ships move more quickly.

Mirco said at December 21, 2008 4:09 AM:

An important point about slaves and romans is that the mortality of the slaves was high and fertility low.
So I think it is improbable that the number of slaves could raise.
There were many slaves in Italy (maybe 1/3 of the population) but the romans enslaved the war prisoners, bought slave abroad, enslaved the abandoned children and a few people sold them selves in slavery to cover their debts.
And, mainly, the romans had no problems to kill slaves rebelling their owners.

The fall of the western roman empire is multi factorial and social-economic problems were more important than climatic ones.

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