Researchers show changing climate caused an ancient civilization’s collapse

Fox News serves up the occasional surprise in its generally unbalanced coverage of climate change, and I’m not talking about its recent giggle about flatulent dinosaurs as an engine of ancient global warming.

Only yesterday, Fox carried a provocative, serious summary of new research tracing collapse of the Indus civilization to a climate shift that occurred about 4,000 years ago.

Changes in the monsoon cycle are now thought to have been the main factor driving abandonment of cities that held perhaps one-tenth of the world’s population, and erasure of a civilization that now ranks among antiquity’s most advanced and least understood.

The monsoon cycle’s role is worth keeping in mind as we think about the fate of the Indus, because similar changes are among the likeliest results of contemporary global warming. Also, they’re high on the list of risks posed by “geoengineering” responses that would reverse today’s greenhouse effects by artificially cooling the planet under a blanket of sun-reflecting aerosols.

Vanishing of the Indus

The cities of the Indus culture, also known as the Harappan civilization, began to take shape some 5,000 years ago and flourished for the better part of two millenia. And then, rather suddenly, the cities emptied and the culture essentially disappeared for reasons that have remained mysterious.

Civil war and foreign invasion have been the leading theories – with unspecified environmental factors trailing behind – but evidence was scant.

Indeed, as one of the lead investigators told Fox, even the existence of the Indus cities was essentially forgotten until a series of archeological discoveries early in the last century.

“Antiquity knew about Egypt and Mesopotamia, but the Indus civilization, which was bigger than these two, was completely forgotten until the 1920s,” said researcher Liviu Giosan, a geologist at Woods Hole Oceanographic Institution in Massachusetts. “There are still many things we don’t know about them.”

The new findings are based on a multidisciplinary team’s analysis of topographical, geological and archeological data, along with photography from the space shuttle Endeavor, pulled together with the aid of satellite mapping and then laid alongside information from  the climate record.

A New York Times account of the new findings, slightly condensed, summarizes the civilization’s rise and fall this way:

Wild, untamed rivers once slashed through the heart of the Indus plains. They were so unpredictable and dangerous that no city could take root on their banks. As the centuries passed, however, the monsoons became less frequent and the floods less intense, creating stable conditions for agriculture and settlement.

Sprawling across what is now Pakistan, northwestern India and eastern Afghanistan, the Indus civilization encompassed more than 625,000 square miles, rivaling ancient Egypt and Mesopotamia in its accomplishments.

Unlike the Egyptians and Mesopotamians, who used irrigation systems to support crops, the Harappans relied on a gentle, dependable cycle of monsoons that fed local rivers and keyed seasonal floods.

As time passed, the monsoons continued to weaken until the rivers no longer flooded, and the crops failed. People began abandoning the cities and moved eastward toward the Ganges basin, where rains were more dependable (though not dependable enough to sustain urban metropolises). The civilization dispersed, fracturing into small villages and towns.

Urban grids, exquisite plumbing

Although far less is known even today about the Indus culture than the civilizations of ancient Egypt and Mesopotamia, it appears at least equally developed. In addition to extensive agriculture, the Indus engaged in seagoing trade, written (and still undeciphered) language — and, Giosan told Fox, they built

cities ordered into grids, with exquisite plumbing, which was not encountered again until the Romans. They seem to have been a more democratic society than Mesopotamia and Egypt — no large structures were built for important personalitiess like kings or pharaohs.

Giosan also explained that the Indus cities flourished during a brief but golden moment in the Earth’s climate history and the region’s monsoon pattern:

The insolation — the solar energy received by the Earth from the sun — varies in cycles, which can impact monsoons. In the last 10,000 years, the Northern Hemisphere had the highest insolation from 7,000 to 5,000 years ago, and since then insolation there decreased.

All climate on Earth is driven by the sun, and so the monsoons were affected by the lower insolation, decreasing in force. This meant less rain got into continental regions affected by monsoons over time.

And when that happened, the Indus became climate refugees, abandoning their great settlements and streaming toward the Ganges.

Any lessons for today? Well, Giosan puts it this way:

If we take the devastating floods that caused the largest humanitarian disaster in Pakistan’s history [two years ago] as a sign of increased monsoon activity, than this doesn’t bode well for the region. The region has the largest irrigation scheme in the world, and all those dams and channels would become obsolete in the face of the large floods an increased monsoon would bring.

And in his comments to the Times, Giosan drew a second parallel, this one for today’s most advanced economies. Like the Indus, we’ve built a complex system dependent on a single resource that can come and go — in our case, oil.

(The research was published in the Proceedings of the National Academy of Sciences, which requires a subscription. Other good coverage appeared in the Los Angeles Times and Discovery News.)

You can also learn about all our free newsletter options.

Comments (6)

  1. Submitted by Gary Doan on 05/30/2012 - 10:20 am.

    Climate changes, are well documented throughout history

    Do you believe significantly higher global energy taxes will have any effect on climate change? Al Gore and the liberal media certainly does. Fox is not the problem with the way climate change is presented in the media. The problem is not people believing that climate changes, but that climate change is an excuse to tax people and redistribute wealth. No one fully understands climate change, they are all guessing, but liberals think that government control and taxes are the solution. That is the real problem.

    • Submitted by Rachel Kahler on 05/31/2012 - 02:17 pm.

      Intentional miss

      Taxes aren’t responsible for global warming. But they might have an effect on the speed by which global warming occurs. I imagine, though, you’re not interested.

      Still, you’re right that no one fully understands climate change. That doesn’t mean it doesn’t exist. And now we have pretty good evidence (though not the first) that global climate change, whether man made or not, can have a very real (and probably deadly) impact on civilization.

      Maybe I can give you an analogy that you’ll accept. Let’s say, for example, that politicians are responsible for stealing most of the money from taxpayers. As a taxpayer, does that make it ok for you to steal money, too (for example by using services while committing tax evasion)? No. That is, even if bad things happen that are out of our control, when we have the power to limit our contribution, it is only moral to do so.

      To analogize, even if we are not the ONLY cause of global warming, we at least have the ability to contribute less to it. And the only moral thing to do is to take steps that reduce our contribution. After all, believe it or not, we can all live without money, but not a one of us (yet) can live without a functioning planet.

  2. Submitted by Randall Wilkinson on 05/30/2012 - 10:41 am.

    A little more intelluctual rigor please

    If this civilization disappeared 4000 years ago where were the cars and diesel trucks, and coal fired power plants to admit CO2 into the environment to cause the climate change? OR…..GASP could it be that this climate change occurred naturally? Is that even possible? The point that Fox news makes time and time again is that the climate change is indeed occurring naturally and is not caused by Man. The global warming hoax is just an attempt by certain groups to obtain political power by fomenting a lie. Just as the Nazis did in Germany by fomenting the lie that the Jews were to blame for the condition of the country when in fact they were not.

    If natural climate change occurred 4000 to 5000 years ago or even as recent as 500 years ago (little ice age) then why is it only possible that Man is causing the global warming now.

    • Submitted by RB Holbrook on 05/30/2012 - 02:00 pm.

      A little more reading comprehension, please

      I’ve looked in vain for the scientists who believe that ONLY human causes are responsible for global warming. I’ve also re-read the above post, looking for such an assertion. I found nothing.

      Why? Because no one thinks that human activity is the only cause, ever, of climate change. The point that 97% of the climate scientists in the world make time and time again is that human activity is the likely cause of the current rapid rate of warming. It is the speed at which it is happening that can be traced to huimans.

      Incidentally, using the Nazis as an analogy to the tree huggin’ libruls just insults the memories of the real victims of the Nazis.

      • Submitted by Randall Wilkinson on 05/31/2012 - 07:03 am.

        Please review the climatic history of the Earth

        A short web search will reveal that the earth has enjoyed about a dozen ice ages in the last million years. Each one of them ended ‘abruptly” with rapid global warming. Since there were very few humanoids around back then please tell me how they managed to impact the environment enough to cause this rapid change.

        As for insulting the memory of the victims of Naziism, I am more than a little aware of consequences of their actions. If you have not read “The Rise and Fall of the Third Reich” then please read it and you will understand the parallels between the tactics of the Nazi party in carrying out their ideological agenda and that of radical leftists.

  3. Submitted by Lance Groth on 05/30/2012 - 02:59 pm.

    Less Hysteria, please, Mr. Wilkinson

    “Just as the Nazis did in Germany by fomenting the lie…”

    Wow. Were you trying to be as offensive as possible, or are you just completely clueless about the Holocaust? When you start flinging around comparisons to Nazis, no one is going to get past that and take you seriously, and really, you ought to be ashamed.

    The rest of your post is so silly as to warrant no further comment.

Leave a Reply