Did Columbus Cause Climate Change?

This story is irresistible for a world historian interested in climate change. Richard Nevle, a geochemist at Stanford, argues that the European advent in the New World, which killed 90% of the 80 million native Americans, caused the Little Ice Age.

The native peoples of the New World burned a lot of wood. When they largely didn’t exist anymore, because they suffered high mortality from a host of European diseases to which they had no immunity, they stopped putting carbon dioxide in the atmosphere. Instead, forests grew rapidly since they weren’t being chopped down anymore, and land wasn’t being cleared for agriculture. Forests take in carbon dioxide and exhale oxygen, plus they fix some carbon dioxide in the soil. They are what is called a “carbon sink,” though not a really efficient one, since much of the carbon they take out of the atmosphere eventually finds its way back there. I suspect the dramatic fall-off in the burning of fossil fuels was the much more important cause here.

Less carbon dioxide in the atmosphere reduces the ‘greenhouse effect’ whereby the atmosphere traps heat generated by sunlight and interferes with it radiating back out into space. Mars is so cold because it has a very thin atmosphere and almost no greenhouse effect. But if you get too much carbon dioxide in the atmosphere, it traps quite a lot of heat, and you get Venus, where lead runs in molten streams on the surface. The current dumping of massive amounts of carbon dioxide into the atmosphere by industrial nations is taking us toward the Venus scenario if it remains unchecked.

An alternative theory is that reduced solar activity contributed to the cooling in the 1600s and 1700s. And the warming period of 900-1300 may have already been reversed in part by the Black Death in Europe and the Middle East, which wiped out one third of the population and would have reduced carbon emissions. Of course all these causes could have operated together.

During the Little Ice age in Britain, people used to go ice skating on the Thames in the winter. Agriculture was badly hurt by shorter growing seasons, causing famines and violent competition over resources– i.e. wars and revolutions. Scandinavia, which had been a major player in world affairs during the warm centuries 900-1300– ruling Ireland and Sicily (where Vikings fought Arabs) and discovering North America– rapidly declined in significance as it froze over. The Ottoman Empire, which threatened Central Europe in the late 1500s and early 1600s, began being drained by the need to put down the peasant Celali revolts in the early 1600s in Anatolia, which may have been climate-related. Famously, there were bread famines in France in the 1780s that likely contributed to the outbreak of the French Revolution.

Since the Nile Valley was warmer than Europe (even if less warm in general in this period) and the river inundated its banks annually, providing natural fertilizer, Egypt was a breadbasket of the Ottoman Empire and 15% of its grain probably went to Marseilles in the 1780s and 1790s; the French under Bonaparte may have decided to conquer it in 1798 in part in order to monopolize its grain and so solve the problem of repeated famine in France. In general, the Little Ice Age overlapped with the age of European maritime empires. The impetus for the Portuguese to take the Indian Ocean, for the British to venture to India, for the Dutch to go into what is now Indonesia, may well have been in part to seek new resources at a time of shrinking European crop yields.

I want to underline that climate change was only one of multiple causes in modern history, and sometimes perhaps a minor one. But given that most societies in the early modern period were agricultural, climate has to be taken into account.

The Nevle theory also underlines that human carbon dioxide-spewing activity has already for some time been important in shaping our climate. That organisms have changed the earth’s climate is nothing new. Life forms 2.7 billion years ago began giving us the oxygen in our atmosphere and life has been one reason the earth did not meet Venus’s torrid fate. Ironically, the modern human romance with hydrocarbon fuels now threatens this 2 and a half billion year old success story and is setting us on a slippery slope toward, ultimately, a Venusian hell.

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30 Responses

  1. I read this elsewhere and it makes perfect sense. The mortality in North and South America exceeded 90%. Civilizations just vanished, contributing decisively to the collapse of carbon levels in the atmosphere. Given the time frame, it happened far quicker than even the industrial revolution.

    This theory also further reinforces the large scale presence of human populations in the Americas pre-1492.

  2. Everything’s useful here, except for the “Venusian hell”. Global warming in the future will cause serious societal problems; it will not lead to a planet without life, and runaway greenhouse is just fear-mongering.

    The “equilibrium” pCO2 right now is about 200 ppmv. That’s the level at which weathering removes CO2 at the same rate that volcanism adds it to the surface CO2 cycle. Changes in that “equilibrium” occur over millions to tens of millions of years, as the rate of volcanic outgassing or the weathering efficiency change. It is possible that human activity can alter this long timescale “equilibrium”, but it’s not likely we can alter it much: there is no reason to think that in 1 to 3 million years climate won’t be back to the glacial-interglacial cycles typical of the last million years. I would guess sooner than 1 million years.

    All of that’s irrelevant to the next 100-1000 years. The point is that global warming is a societal problem. A major societal problem. But not something that has any huge meaning based in some age-old natural process that we’re interrupting. We, along with the global warming we’re causing, are just part of the natural process, and as much power as we have to alter evolutionary trajectories and temporarily change climate, in the long run it will all just be a blip in the geologic record. A high amplitude blip, but still just a blip.

    • I wasn’t saying we would get to Venus or shortly. I said dumping massive amounts of C02 into the atmosphere was a step in that direction. You are saying a small step. OK. But there is no guarantee of the sort of equilibrium you envision. chaos theory has taught us about catastrophic change not being so unusual.

      • Ther are still gaps in our understanding of the carbon cycle, but the gaps aren’t big enough to allow for a chaotic process that would drive a runaway greenhouse effect. The equilibrium isn’t something I “envision” – it’s the standard carbon cycle model for greater-than-million year timescales.

      • A small step (in comparison to the massive VENUS step) may nevertheless be an enormous step in comparison to where we are today, if flooding, far more extreme storms (hurricanes already doing small amounts of damage), changes in growing seasons and precipitation and VERY IMPORTANT changes in where and how plants and insects grow and in the uniform-versus-non-uniform provision of water in rivers to cities (as snowfall and glaciers change and more water falls as rain or quick-melt snow than as long-melt snow. People whose agricultural adn industrial and city water supplies dry up for most of the year (due to quick-melt snow as their local climate warms up) might well “have” enough water but “have” it all of a sudden and not for the rest of the year.

        Don’t need VENUSIAN temperatures to make life even more uncomfortable than it already is in many places.

    • Okay, not total extinction, but what about the biggest mass extinction events of the past, which eliminated 90% of all species? What we know about them is that CO2 levels got so high that it must have gotten very hot and it had to be due to some greenhouse source not currently in play. We have large amounts of CO2 and methane locked in the permafrost in Siberia, which is melting. That gets us to a higher level. Then there’s the methane clathrate deposits in the polar oceans, which if evaporated would give us all the explanation we need. If the Siberian thaw gets us up high enough to melt the methane, then it becomes much bigger than a human problem.

  3. No doubt we too will be a blip in a few million years. But if the current warm trend continues its asymptotic rise we may achieve blipness within the next century or so. As glaciers melt and the great rivers they feed run dry, as coastal nations are inundated by rising seas and their peoples forced to seek shelter inland, desperate populations will fight wars for resources and territory — wars which will inevitably employ every weapon of mass destruction.
    The scars we leave will take a few millennia to heal but life forms old and new will move to occupy the ecological niches we have briefly monopolized.

    So no need to worry: if we commit negligent suicide, the earth will survive just fine.

    • I emphasize that global warming is a serious, maybe eve catastrophic, problem for society. It is possible it will be catastrophic for the species homo sapiens. But calling up scenarios that are apocalyptic on an even grander scale than just us – i.e. putting Earth on a trajectory to become Venus – has absolutely no support in the geologic record or climate science, and I believe it feeds a cynicism that undermines the political need to do something about global warming and its effects.

      What is said about global warming needs to be based in science, and since climate science already points to scenarios devastating to modern society, why should we try to exaggerate the situation into something that lacks any basis in climate science?

      • I have figured out that you are reading my Venusian imagery literally. It was a literary device.

      • Feeding cynicism that undermines the political need to do something…

        Perhaps I don’t understand – saying that some actions could have an apocalyptic effect causes people to JUST WANT TO KEEP ON doing those things? Makes no sense to me.

        That would be like saying that, since detonating many hundreds of nuclear weapons could wipe out all human life (and other life) on the planet, this would be viewed as an incentive to keep building MORE of them, instead of working for arms control.

        If my memory serves, nations really did work to control nuclear weapons, and still are.

        • Although I don’t think that’s what BSC meant, you may actually have a point that people are looking for excuses to say that we’re already past the point of no return, so why not whoop it up for our remaining years?

          My belief has been that one day the heads of America’s corporations will call a press conference in which they finally explain how they fooled us and what we Americans will have to do to survive the world’s wrath:

          “Yes, we deliberately withheld information and produced false counterinformation so you would keep consuming so as to prop up our paper economy. Our computers told us the worst consequences would be elsewhere; that the drying of the rivers that come from the Himalayas to India and China would cause far greater misery than the decline of the Colorado, that the swamping of coastal towns would most ruin the lives of those with the least money. The world would be weakened more than America and we would exploit this and you would profit from it too much to give it up. So we lied to you to make you pass up every chance at a solution that would involve taxing us and ruining the most successful civilization the world has ever seen, merely out of guilt for inferior weaklings.

          So now the blood is on your hands, and the world of subhuman communists will demand reparations and mitigation from us, which are now so severe that you will never agree to them. You and we together have declared war on the rest of the world, and you have no choice but to obey us, your new commanders, and give us all you have to keep up a military that will draft all your children. We will turn the world into a forced labor camp to maintain just compensation for our genius and entrepreneurship, and you will become our henchmen, our soldiers and prison guards, to hold on to power for as long as we can or face utter extermination at the hands of 6 billion victims. You will use up the oil and then convert back to slave labor, but still all the money will go to us and we will give some of it back to you, and you will be happy that you are not one of the slaves. You will prod the slaves with tasers as they build the dikes that protect your homes from encroaching waves, scan their barcodes as they plow over the wheat fields that no longer have fertilizer to make them viable, machine-gun their riots in the streets of whatever countries we can expand our dominion to, and tell yourself that they deserve it because they would all be dead without our munificence.

          If you work hard and obey, your children may eat. If not, you still ended up living better than you would under SOCIALISM-ism-ism-ism…”

      • Most people spreading the propaganda that current climate change is a natural process and not worthy of concern, point to the accurate fact that humans can’t permanently harm the biosphere and that greater disasters have happened in the past and the earth recovered just fine.

        While I don’t dispute this, I quickly remind people who promote this argument that this isn’t a debate about the survival of life on earth, this is all about survival of modern society which is in a highly precarious place when it comes to weather as recent meteorological events have proven over and over again. It is about the severity of problems our kids and grand kids will have to face.

        And so we must be careful to constantly direct the conversation to climate change being a threat to “us” and not the planet at large. I think this is the point that BSC is trying to make.

      • “I believe it feeds a cynicism that undermines the political need to do something about global warming and its effects.

        What is said about global warming needs to be based in science, and since climate science already points to scenarios devastating to modern society, why should we try to exaggerate the situation into something that lacks any basis in climate science?”

        Absolutely – you’re so right, like 200% right

        That said, many of those claiming to be climate scientists are just as guilty of using a rhetorical style more often heard from the pulpit than from the lectern e.g. “we’ll all go to hell in handbaskets if we keep eating toast for breakfast”. I refer to all such people as “The Green Fundamentalists” – scientists or otherwise.

  4. We create and distribute our philosophies, our explanations of the world we find around us, we create and distribute the explanations of science and religion we use to create our cultural worlds. If we create an ideology of “we die, but so what, it’s fated to be so,” it helps us take a big step in that direction, it helps us be passive in the teeth of the crisis.

    Yet we also create and distribute our systems of what we value, and we create the systems of goods and services we manufacture and provide to fulfill those economic values we have created. And further, we also create and distribute the systems of social honor, status and rank we use to prefer one set of persons over another; although the connection is fairly tenuous in modern post-industrial society, this is the root of the systems of state power and governance we have invented to rule “the politics” of our social order.

    We could, if we wished, totally re-invent ourselves and our mental and physical cultures over the next twenty years, and perhaps somehow evade the foreseeable crisis.

    By definition, if we remain stuck in our present explanations, our present systems of status and rank, our present set of economic values, we can’t change. And thus we and all our children, all our marvelous (and our not-so-marvelous) culture and entertainments and feelings will die, forever.

    What a deal. Which side are you on?

  5. From memory Ian Morris’ Why the West Rules : For Now offers some support for these arguments.

    Ice cores should confirm whether changes CO2 levels coincide with rapid population loss in Western Hemisphere in the 16th century.

    Aus & NZ have just installed desalination plants in a couple of Pacific Island states, Tokalau & Tuvalu. They’ve run out of fresh water, not due to rising sea levels but lack of rain. I think they’re diesel – don’t know if they can be converted to solar, wind or tide, if not I guess Aus & NZ will keep supplying the diesel – so more CO2. The small Pac island states depend on aid, many are expected to get swamped at some time – might be better to relocate the people sooner rather than later. Most will go to NZ or Aus eventually.

  6. Frankly I think the explanation is a little farfetched, and seems to be relying on the very hotly-contested “90% population decline” figure. Many historians and anthropologists put the figure significantly lower. In addition, the demographic collapse was not instantaneous or simultaneous throughout the Americas. It wasn’t just European landing on the coasts of the Caribbean that led to the spread of disease: it was active European penetration into the wilderness of the continent that continuously pushed disease further inland, a process taking decades and centuries.

    The explanation I had always heard for the Little Ice Age was that of a large volcanic eruption taking place in the Pacific, which reduced the light passing through the atmosphere and lowering temperatures. Seems quite a bit more probable to me.

    • David, I haven’t heard any population loss estimates that were LESS than 90%. And I’ve gotten my numbers from (right-wing) PBS.

      As far as “instantaneous” goes, if the die-off took decades, that would be essentially “instantaneous” as far as the climate and geological processes are involved. And disease spread would not require large-scale European penetration into the “wilderness”; given the large degree of commerce among the Native American tribes, both within the interior and from islands along the coast, diseases would spread horrifically fast.

      By the time the Pilgrims settled in North America, they frequently remarked on all the deserted “Indian” villages everywhere. Most of the deaths across the continent seem to have taken place within a century.

      • Actually the Pilgrims reported “deserted” settlements because they were anticipating densely-populated, politically-sophisticated states like the Spanish had found in Mexico and Peru, not because there had been significant depopulation.

        The “90% population loss” description is indeed very hotly disputed, as is the cause of the decline. Some have argued rather convincingly that these estimates place too much emphasis on disease, reducing the importance of European violence over the course of many decades, in dwindling populations. Others argue that the figure is based on exaggerated and unreliable claims by contemporary European colonists.

        The point is not to minimize the catastrophic impact of European expansion into the New World: quite the contrary, it reinforces the degree to which Europeans deliberately, intentionally, and violently expanded in the face of still-significant populations of Native Americans as they moved inland.

        I recommend reading Suzanne Alchon’s book “A Pest in the Land” for a good critique of modern scholarship on the issue.

    • Nevle, being a geochemist, ruled out volcanoes as the main cause.

      It wouldn’t matter to the argument if 40 million people disappeared over 75 years, and I’m surprised you think it does. It would be important that they were tree-burning people analogous to the Senegalese in Casamance today.

      • But Juan, lots of climatologists and geochemists explicitly support the idea that volcanic reactions could have contributed to or caused the Little Ice Age. Nevle’s position as a geochemist doesn’t automatically mean her dismissal of previous findings or hypotheses is any more valid than their endorsement of them. Indeed, it’s not as though Nevle’s ideas are terribly new, either: population decline and reduced wood burning have been argued for to some degree for quite a while. I just don’t think it’s necessarily wise to hop on the latest piece of scholarship when it conveniently dismisses the work of past scientists.

  7. In addition, it seems quite clear from reading up on the Little Ice Age that there’s a serious consensus that it began centuries before Columbus sailed to America.

    • That is irrelevant. 1300-1850 is a long period & had phases, and each phase could have had its own mix of causes

      Cheers. Juan

      • But in your link to the article, you explicitly say “Richard Nevle, a geochemist at Stanford, argues that the European advent in the New World, which killed 90% of the 80 million native Americans, caused the Little Ice Age.”

        Your own title for this entry is much less misleading: did Columbus Cause Climate Change? Entirely possible. Did Columbus Cause the Little Ice Age? Almost certainly not.

  8. Juan,
    It is fascinating when you get away from the Middle East. Fascinating hypothesis, and I am relieved that Columbus had nothing personally to do with the climate change any more than he himself infected so many local inhabitants.

  9. Let us keep in mind other palpable causes: an extended solar minimum and some very powerful volcanic eruptions. Wikipedia is not a bad place to start discovering the LIA. Still, this hypothesis is also a reasonable partial explanation. Here is some science (note the tropical emphasis): Faust, Franz X., Cristóbal Gnecco, Hermann Mannstein, Jörg Stamm, 2006: Evidence for the Postconquest Demographic Collapse of the Americas in Historical CO2 Levels. Earth Interact., 10, 1–14.
    doi: 10.1175/EI157.1 – online at
    link to journals.ametsoc.org

  10. i might buy in to this theory, except for one detail seemingly ignored: while the natives were being killed off, their carbon emissions were being replaced by the european colonists. they burned wood for heating & cooking, and stripped land bare for both building and planting, in far greater acreage than the natives ever did. when cotton and tobacco became the primary cash crops in the southern colonies, 1,000’s of acres were denuded for planting. since both those crops leached the soil of nutrients, new acreage had to constantly be cleared to replace the dead fields.

    clearly, the natives never cleared the volume of land in amounts anywhere close to that of the european settlers, so i am a tad skeptical of this theory.

    • The Europeans did not replace the natives with regard to population for a very long time. At the time when the Anglos and the Californios were fighting over whether California would become part of the US or stay in Mexico, there were roughly 300 guys on each side in most of the major battles.

  11. I would be skeptical that the change in land use CAUSED the little ice age — or even contributed greatly. The biggest problem with this hypothesis is that the observed changes in CO2 in the atmosphere are really small during this period. We have an observed record of the CO2 in the atmosphere from air bubbles in ice cores and they show a decline of about 8 ppm out of 280 ppm between 1500 and 1600. Compare this to the -100 ppm changes to the previous ice age, and the +120 ppm change we have already seen. While this 8ppm decline may be the result of depopulating the Americas, from the standpoint of changing the climate this is negligible. If I had to put a ballpark number on this I would say a 3% change in CO2 -> -0.1 Watts per square meter -> .075 Kelvin (about 0.1 degrees F) cooling. I have no idea how a Stanford geochemist gets around these basic facts.

  12. There is a telling report on what happened to streams in southeastern Pennsylvania during European colonization. Prior to Penn’s colony, streams had “anabranching” flow, flowing in sheets across expansive beaver meadows, which were mostly peat–there was very little sediment coming off the uplands. As soon as the Europeans showed up, the beavers were killed, land was cleared, heavy erosion followed, and the old beaver meadows were replaced by what amounted to gullies.

  13. another reduction in the burning of the fossil fuels worldwide may have been the result of the deaths and devastation caused by the Mongol invasions, which killed millions of people throughout Asia.

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