"Little Ice Age" possibly caused by reforestation

Discussion in 'Environmental Discussion' started by MontyTheEngineer, Oct 13, 2011.

  1. MontyTheEngineer

    MontyTheEngineer New Member

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    Columbus Blamed For Little Ice Age - Science News

    The initial explorations of the New World brought diseases that wiped out the majority of the people living here, causing cleared lands adding up to the size of California to be reclaimed by the jungle. The rapid, massive reforestation was enough to account for most of the CO2 changes in ice cores from the time and for most of the resulting drop in global temperatures.
     
  2. austingreen

    austingreen Senior Member

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    Now the theory that it helped has been around since 2008, and seems to explain CO2 in the ice cores, but not total blame or credit for the LIA. I would say "most" of the drop is over reaching conclusion. I liked their previous analysis better.
    http://news.stanford.edu/news/2009/january7/manvleaf-010709.html

    Now if you believe columbus caused the LIA, then it is obvous that the deforestation would be responsable for most of the RTM in global temperatures and not burning of fossil fuel.
     
  3. mojo

    mojo Senior Member

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    Ice core records show that throughout the past 800,000 years CO2 levels have been a response to temp levels.CO2 levels respond roughly 800 years lagging temperature levels.
    800 years prior to the LIA,temps were crashing after the Roman warming period.
    CO2 levels in 1500 were the result of temp declines 800 years prior.
    But because the CO2 decline in 1500 coincides with Columbus ,now its Anthropogenic.
    6-10 Parts Per 1,000,000,000 causes a Little Ice Age.
    Really?
    This is the dumbest "science" Ive read yet today.
    But par for the AGW course.
     
  4. tochatihu

    tochatihu Senior Member

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    "Now if you believe columbus caused the LIA, then it is obvous that the deforestation would be responsable for most of the RTM in global temperatures and not burning of fossil fuel."

    Sorry, the meaning here is not quite clear to me - is it something you'd like to discuss Austin?

    There have been several attempts to estimate changes in forest cover after the last deglaciation, responding to the extension of clearing land for agriculture, and responding to epidemic-caused human population declines. None have seemed slam bang detailed certainty to me, but there have certainly been ups and downs of forest cover. Large ones.

    This is followed by loss of carbon from soil organic matter, because croplands don't feed that as well as forests do. We are still limited by not knowing how much forest mass there was, at paleo-date of your choice YYYY. But there is no doubt that big changes in forest cause big changes in net CO2 flux to the atmosphere. Right now forests hold about the same amount of carbon as the atmosphere, and soils 4 times as much. To imagine that substantial changes in 4+1 (soil+tree) could not affect the 1 (atmosphere), well I just cannot think of a polite way to characterize that.

    The uncertainty means there is still room for the reforestation guys and the temperature driven ocean guys to both proclaim the contributions of their emchanisms. The latter group, interestingly enough, includes both our mojo and Michael Mann. Title of the thread is fair enough though - "possibly".

    What Nevle offers here that 'has legs' is the biochar record. Can read about it

    Volume 264, Issues 1-2, 7 July 2008, Pages 25-38
    doi:10.1016/j.palaeo.2008.03.008
    Effects of syn-pandemic fire reduction and reforestation in the tropical Americas on atmospheric CO2 during European conquest
    Richard J. Nevle, Dennis K. Bird

    I am a big fan of exploring carbon history with biochar. It is super-stable in soil, 14C isotope is a great clock, and 13C/12C ratio is a great 'mix recorder' that also gives some hints about plant physiology. Drawback to Nevle and Bird is that very limited regional coverage.

    Hard to get around that though. Digging holes is easy, but the char analyses are whacking expensive. I happen to have bags of it from a nearby forest site awaiting analyses. Can't afford it yet. But the char is happy sitting in bags. It ain't going nowhere. It is pretty much the only form of carbon that microbes refuse to eat.
     
  5. tochatihu

    tochatihu Senior Member

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    Well, youse guys did it again, stimulated me to go looking for more on the subject. Now, I like
    Boyle et al 2011 "Modelling prehistoric land use and carbon budgets: A critical review"The Holocene 21:715-722


    Had not picked that one up before. It does span the range of estimates for cumulative prehistoric forest C -> atmosphere C, namely 20 to 160 Petagrams of carbon. But it is handy to have all the numbers together on one chart. Also included are 2 inverse models based on ice-core isotopes. One is right in the mix, and the other is rock bottom. Interpreting differences between those 2 (as I feel free to do, here at least) goes like this: The high ice-core line means that ocean uptake did not buffer the deforestation release. The low-ice-core line means that it did. Take you r pick...



    What Boyle's group thinks should be done to narrow the range is to somehow come up with a sharper timeline for human population since 8000 years ago. They further suggest that it maybe cannot be done. So if anybody has a great idea how to do that, step right up.


    So, thanks for the push. There is too much stuff to read so usually I focus on a few topics. PC wild-eyed threads make me read more widely.


    Well, this one is not a wild-eyed thread, but some of them surely have been. Maybe we should do a retrospective some day.


    It has calmed down a lot since poptech stopped channeling stuff from the website of the same name. That guy was a hoot.
     
  6. austingreen

    austingreen Senior Member

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    Just that the pop science headlines don't really follow the science well, but they make people read.

    Normally we think of reforestation as a good thing, and deforestation as a bad thing, but this turns that kind of reasoning on its head. Finally, there has been a great deal more deforestation compared to before columbus. If you are going to blaim the cold on him, you need to apply causation to those destroying the forests at a great rate. Finally the idea of most is caused by a series of events, when there is great uncertainty is not provable or likely. Definitely their was some RTM (return to mean) temperatures after the little ice age, and full blame or credit for this should not be given to burning of fossil fuels.

    Then again mann and mojo are arguing against this explanation, which makes me think there must be some contribution to the temperature and co2 record:D
     
  7. mojo

    mojo Senior Member

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    6 PPM?
    So the Earth responds to Homeopathy?
     
  8. cyclopathic

    cyclopathic Senior Member

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    It is still far cry to what oceans hold; the elephant in the room is the phytoplankton. Changes in phytoplankton blooming may have more impact the re-forestation. In many cases blooming is limited by iron/phosphorous concentration.. which are seeded in oceans by aeolian dust, volcanic ash, etc. One Icelandic eruption may have had more impact then Columbus. Most likely the 1600 Huaynaputina and perhaps 1580 Billy Mitchell had more impact on phytoplankton and global climate.

    However the re-forestation caused by Columbus and Black Death in Europe and Middle East may/should have had impact, question is to what extend?

    Also LIA coincides with Maunder Minimum/least solar activity and Bond/1500 event caused by cyclic Thermohaline circulation slowdown you cannot ignore that.

    Fact is that w/o looking into real numbers and running simulations it is all speculations.. Not a real science just something mojo is good at. .
     
  9. cyclopathic

    cyclopathic Senior Member

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    unfortunately your stupidity doesn't
     
  10. tochatihu

    tochatihu Senior Member

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    AustinG, if you read Yude Pan's newest in Science (maybe still in Science Express), you will have a good handle on current deforestation and afforestation carbon fluxes. Both are happening, but the latter appear to prevail now.

    CycloP, Ocean C is big but most of it is in deep water. Slow to communicate with the surface, unless the large scale water circulation patterns change. They could - at least some oceanographers have concerns.

    To add perspective and perhaps clear up misconceptions (hi mojo), here are several pools, expressed at petagrams of carbon

    Shallow ocean inorganic 1000
    Deep ocean inorganic 38,000 (I'd put the dividing line between these at the maximum seasonal thermocline depth, but can't confirm that the wikipedia graphic does so)
    Deep ocean organic 700
    Atmosphere 800 (concentration in ppm times 2. Actually times 2 point small fraction)
    Forests 800 (tree stems, foliage and roots. All the living stuff)
    Soil organic matter 3300
    Soil inorganic carbonate 800 (that estimate is quite squishy because soils derived from limestone rocks are not well surveyed globally. Sorry about that.)
    Dead wood 70 to 110 (my personal "burden")

    These numbers do not all agree with the wiki, but I can tell you where they come from if you want to audit me :)

    This may also help to interpret the 20 to 160 Pg C range I mentioned earlier, thought to encompass all the forest clearing of 8000 years. The total fossil fuel release since 1750 is about 500 Pg C. I think I did that calc. right, if you see a much different number, speak up.

    So if the (abstract) room includes the atmosphere and other pools that can directly communicate with it, the pools are mostly about the same size. Soil organic matter is 'big dog' but does not reach 'elephant' status. The elephant (deep ocean water) is not in the room, at least not now.

    I'd like to know just how much thermohaline circulation has varied in the last 8000, or 500 years. You'll probably make me go look for that.

    The Beryllium-10 isotope, considered a good proxy for solar activity (and thus, inverse for galactic cosmic rays) dropped low during the Maunder minimum. But curiously, only late in it. Couddn't tell you why..

    If solar activity lags (not leads), is it then caused by earthly temperatures? Solar physicists ain't gonna go for that. But it is stated as analogous to CO2 lagging temperature. My red herring for the day. No PC rule says I can't toss out my own red herrings (primarily for amusement). At least I describe them as such.
     
  11. cyclopathic

    cyclopathic Senior Member

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    So what amount of CO2 is sequenced by ocean annually? It was my understanding that oceans are the biggest CO2 sink and let's say 25% increase in phytoplankton blooming due to stratovulcano iron/phosphorus seeding would have had impact similar if not bigger then reforestation
     
  12. tochatihu

    tochatihu Senior Member

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    The oceans and forests each net consume about 2 petagrams of carbon per year. They are now equals, near as can be determined.

    There have certainly been proposals to add iron and/or phosphorus and/or silica to the oceans. Big volcanoes do that naturally, although I would not bet on much P. So yes, it would increase sequestration. But call up that volcano sooner rather than later, because a few more 0.1 pH unit declines in surface water pH might limit the payoff.

    How much C seq you'd get from reforestation (of course) depends on the scale of the project. There the payoff starts slow and increases, because little trees don't fatten up much the first few years. Some do much better than other of course. Most of the payoff comes decades later.

    The ocean fertilization would be different, you get all the boost at the beginning. If it works, the stuff you want sequestered sinks, taking a lot of those nutrients with it. A few years later the surface waters are hungry again. So, call up another volcano.

    Those things are actually two-fers, in regards to climate. You get the prompt cooling from atmospheric sulfate aerosol, and ocean fertilization to the extent that nutrients are delivered to the appropriate ocean surface areas.

    Any other sort of dust delivered to the ocean may also fertilize, and Sahara and Asian dust clouds both do. This may be one of those Gaia-thingeys. Climate heats up (some way or another), continents (at least somewhere) dry out, more dust to ocean, more C-sequestration. Climate cools a bit, plant cover returns to the dust source areas.

    Bam. and there's your thermostat.
     
  13. tochatihu

    tochatihu Senior Member

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    By the way, I see that a volcano ocean iron fertilization paper just popped up in Global Biogeochemical Cycles (1 Oct 2011). You aren't tracking the literature, are you? I mean dang.
     
  14. robbyr2

    robbyr2 New Member

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    Did the pre-Columbus New World population of up to 30 million have that kind of impact on the planet prior to the Little Ice Age?
     
  15. mojo

    mojo Senior Member

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    Buffalo farts probably had more effect.
     
  16. cyclopathic

    cyclopathic Senior Member

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    No I don't. just happen to read IPCC paper on South Atlantic fertilization experiment a while back.

    Speaking of that if we are serious about removing anthropogenic GHG we should move forward with geo-engineering, tree planting, ocean fertilization, etc. While the industrial/transportation CO2 reduction is a hot topic, they are not the only sources. And in other places it may be easier to reduce GHG. For example in agriculture, using different rice variety, adding sulfur to fertilizers, alternative cattle feed mix, etc.

    Problem is that New World pre-europian soils were very fragile and could not sustain intensive agriculture. It forced natives to keep large amounts of land cleared. Of cause the easiest way to clear brush is to burn it; and to put it in prospective present pit fires put Indonesia /surprising/ as the world 3rd largest polluter.

    EPA proposes new tax on cow and pig flatulence
    http://www.iisc.ernet.in/currsci/jan102005/119.pdf
    Where buffalo roamed
    Unfortunately the author jumps to conclusion that Indian water buffalo and American wild buffaloes produce the same amount of methane. Questionable at least, taking into consideration they are different species and have very different diet.

    PS hope you are not gonna turn this into another Vostok ice core mantra
     
  17. tochatihu

    tochatihu Senior Member

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    robbyr2, human population of 'the Americas' pre-1492 has been estimated as you say, but also quite a bit higher. I guess we really can't pin that down now.

    I'm not backing any particular number (not that it would matter if I were to do so). Your further reading will indicate that Cahokia mounds, among many others, seem to have took a lot of people to construct. Would look like an interesting topic to dig into, especially as the paleo-human populations appear to be so poorly known in general.

    Ruminant methane emissions are not insignificant globally

    Belching Ruminants, a minor player in atmospheric methane, Animal Production and Health (APH), Joint FAO/IAEA Programme

    But this is another one of those things: As we are not likely to reduce the global demand for beef any time soon, we are just going to have to accept the trajectory. Diet changes probably help, so let those researchers keep a goin'. Fortunately one can now measure the whole 'barnyard' from an eddy covariance tower. Saves the trouble of bagging cows.

    Wetland rice methane is also getting a real close look. Options exist, but we should not suppose that reducing rice production is among them.
     
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