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Comments 51 to 74 out of 74:

51. AHuntington1 at 13:49 PM on 20 September, 2012
    John Hartz, essentially, yes I do believe that the spread of the Sahara has been largely the result of mismanagement of land. Increasing rates of desertification across the globe are the result of the same mismanagement.
    
    When I say ecological perspective, I mean a perspective that takes into account the ability of bio-diverse ecosystems (or lack thereof) to influence local climate and desertification in general (water cycles, decomposition cycles, solar cycles, mineral cycles, carbon cycles).
    
    Ecological systems have evolved for millions of years in order to withstand and thrive in conditions with extreme variations in local rainfall over time. As humans learn to work with and exploit these natural systems, the "negative" aspects of more sporadic rain will be reduced and the positive aspects enhanced.
52. AHuntington1 at 14:06 PM on 20 September, 2012
    DSL, that is fascinating! This completely makes sense, as wetter regions can handle a high level of mismanagement (such as overgrazing) in comparison to drier regions with more sporadic temporal fluctuations in rainfall.
    
    As the planet warms regional rainfall patterns would change (horse latitudes begin drying), this makes the local environment have higher fluctuations in rainfall (and drier) and more susceptible to mismanagement (such as overgrazing) and subsequent desertification.
    
    For this reason anthropogenic desertification will always be faster in environments with higher seasonal fluctuation in rainfall over places with a less seasonal fluctuation in rainfall.
53. AHuntington1 at 14:13 PM on 20 September, 2012
    whoops...please excuse the grammar. i forgot the old adage, "post once, edit twice"..
54. Bernard J. at 14:33 PM on 20 September, 2012

    Bacteria within arid environments (which are usually grasslands) primarily survive the dry season's "bacterial holocaust" by living in the rumen of a grazer.

    
    
    No, rumen-adapted bacteria primarily survive by living in the rumen of a grazer. Bacteria that live in arid environments have other adaptations to survive, including sporulation and simple dispersal by wind, water, and/or on fomites.
    
    Internal bacterial communities are remarkably resistant things, and don't much allow externally-adapted species to board the ark whenever the rains don't come.
    
    Apart from this, there is a gaping logical fallacy in your overall argument about climate change and land use. The form is:
    
    

    If A, then B.
    
    B, therefore A.

    
    
    I wonder if you realise what it is?
55. John Hartz at 14:40 PM on 20 September, 2012
    @AHuntington1 #51:
    
    You have conveniently ignored my request to provide documentation for your assertions. Personal opinion and sweeping generalizations have virtually no value in a discussion of scientific evidence and findings.
56. AHuntington1 at 15:30 PM on 20 September, 2012
    John Hartz, well here is one piece of documentation implicating overgrazing (a complete land management issue) as a causative factor in desertification. http://www.academicjournals.org/ajb/PDF/pdf2011/17Oct/Saad%20et%20al.pdf
    
    There are many more- just google overgrazing and desertification if you wish to access them (or I will post more).
    
    Bernard J., Of course rumen-adapted bacteria primarily survive by living in the rumen of a grazer- I didn't mean to imply that they survive outside the animal for long.- lol
    
    I am talking about the bacterial carcasses, water, fiber, nitrogen etc. that the fecal matter and urine of massive herds of ruminants provide to decomposers on the drier soil surface- extending their lifespan a little further through the hot bacterial winter. Ruminants fertilize, chop grass, and till the earth's surface simultaneously.
    
    Lay out my non sequitur for me please, I am having trouble seeing it.
57. gws at 17:08 PM on 20 September, 2012
    AHuntingdon1
    A: "Overgrazing can cause desertification" (not detested)
    BTW, this does not jibe with your comment @51, last paragraph
    B: "Desertification is observed, therefore overgrazing must have been happening" (incorrect conclusion, aka logical fallacy)
    Correct: Desertification can be caused by other factors aside from overgrazing, or any grazing. For instance, a change in climate, particularly increasing T alongside reduced rainfall, can cause desertification.
    
    When posting at SkS, try making cohesize statements as you would in a written text for students, not blurbs that can be misinterpreted. You maybe perceived as a troll.
58. DSL at 00:24 AM on 21 September, 2012
    AHuntington, thank you for the clarification from "desertification" to "anthropogenic desertification." For a minute there, I thought you were trying to blame the general process of desertification on humans. Humans can obviously cause desertification, but circulation-based desertification is the primary mechanism and has been for the duration.
59. John Hartz at 01:11 AM on 21 September, 2012
    @AHuntington1#56:
    
    Thanks for the providing the link to the peer-reviewed paper, "Nature and causes of land degradation and desertification in Libya: Need for sustainable land management."
    
    In the paper's Abstract, the authors state:
    
    "Among others, overexploitation of natural resources, inappropriate land use planning, insufficient water resources etc. are the main factors escalating the process of desertification and deteriorating environmental quality."
    
    Some of the factors cited are caused by human activity and others are not even identified.
    
    My position is that the natural environment existing at any location on Earth has been and will continue to be affected by changes in the planet's global climate system.
    
    From my perspective, your sweeping assertion that desertification is primarily caused by human activity at the local and regional scale may hold true in the short-run, but will not hold true in the long-run. In the long-run, desertification has been and will continue to be driven by changes in the Earth's global climate system caused primarily by the burning of fossil fuels and deforestation.
    
    Note: When I refer to the "global climate system" I mean the standard definition used by climate scientists. The entire system includes the atmosphere, the aquasphere, the cyrosphere, the biosphere, and the lithosphere.
60. John Hartz at 01:20 AM on 21 September, 2012
    @AHuntington1 #56:
    
    As they say, "What's good for the goose is good for the gander"
    
    Please Google "Climate change and desertification" and read some of materials listed. You just might learn something new.
61. AHuntington1 at 03:53 AM on 21 September, 2012
    John Hartz, I am not disputing the fact that climate change is a driving factor in desertification. The ecosystem's ability to cope with a change in local climate is a bigger causal factor in desertification.
    
    When the horse latitudes heat up (whether from anthropogenic emissions sooner, or the sun slowly enveloping the earth later [ http://physicsworld.com/cws/article/news/2008/feb/26/earth-is-doomed-in-5-billion-years ]) rainfall will become more sparse and sporadic. There are certain ecological mechanisms that have evolved to cope with such sporadic moisture. If humans properly exploited these mechanisms- changed our behavior to fit the changing climate- desertification as we know it (climate change characterized by increasing erosion, destruction of biodiversity, and breakdown of ecosystems) could be avoided to a high extent.
    
    You mention burning fossil fuels, and deforestation as potential causal candidates for desertification. I don't disagree, although overgrazing, deforestation, and local ecosystem destruction are also major players.
    
    Co2 driven climate change would cause rainfall patterns to change. Whether human management of bio-diverse ecosystems (or lack thereof) can cope with these changes determines desertification.
    
    
    DSL, if you believe that human emissions of fossil fuels, and human errors such as overgrazing, deforestation, etc are causing desertification, you believe that all desertification is anthropogenic. Isn't this correct? What aspects of desertification are not anthropogenic?
    
    So the only issue on which we seem to disagree (so far as I can tell) is my contention that higher atmospheric Co2 is not as big a driving force of desertification as human promotion or demotion of bio-diversity. Ecosystem management is really the issue here.
    If humans stopped burning all fossil fuels, the rate of deforestation would probably skyrocket (as deforestation is already primarily a fuel issue in developing countries). Mismanaged cattle would still be roaming around. Biodiversity would likely decrease. Desertification will likely continue, regardless of human Co2 emissions, unless land management is addressed.
    
    Ecosystem destruction is at the root of desertification.
    
    
    gws, my argument is more like this:
    
    1. Land management errors cause desertification (undisputed).
    
    2. Therefore, without changing these specific land management issues (eg. overgrazing, deforestation, species extinction, burning the grasslands too much, etc.), desertification will continue to occur, regardless of human emissions of Co2.
    
    Human emissions might be a factor in causing the initial climate change, but human land management practices are the primary reason for subsequent desertification.
62. DSL at 03:57 AM on 21 September, 2012
    AHuntington: "DSL, if you believe that human emissions of fossil fuels, and human errors such as overgrazing, deforestation, etc are causing desertification, you believe that all desertification is anthropogenic. Isn't this correct? What aspects of desertification are not anthropogenic?"
    
    Hadley-type circulation existed before significant human modification of the atmosphere. Hadley-type circulation can be modified by other major forcings (solar, volcanic aerosols, etc.). Desertification has occurred as large-scale circulation patterns have shifted in response to major forcings over the course of Earth's history.
63. Sphaerica at 04:13 AM on 21 September, 2012
    AHuntington,
    
    The main cause of deserts is the Hadley Cells (and in a few special cases altitude). This is readily apparent by noting that the latitudes at which deserts occur are the same (above and below the equator) and is readily explained by the mechanics of the Hadley Cells.
    
    You may argue all you want to otherwise, and certainly some of those arguments will be valid in some cases, but this does not change the fact that one major, unavoidable and already observed effect of global warming will be the expansion of the Hadley Cells, which will in turn necessarily and proportionally expand the existing deserts poleward.
    
    Texas, the American Southwest, Mediterranean Europe and others are in for a very rough ride.
64. AHuntington1 at 10:34 AM on 21 September, 2012
    DSL, Hadley-type circulation did exist prior to anthropogenic CO2 emissions increasing, this results in deserts with sporadic fluctuations in rainfall over time.
    
    As to why Hadley cells are widening, I was under the impression that you thought anthropogenic CO2 emissions were responsible. Thus the spreading of deserts or desertification would be anthropogenic.
    
    you said, " Desertification has occurred as large-scale circulation patterns have shifted in response to major forcings over the course of Earth's history. "
    
    I agree completely, and add that since humans have existed on earth, we have become a factor that can either rapidly intensify natural desertification and ecosystem breakdown, or promote biodiversity, and ecosystem growth.
    
    
    Sphaerica, you said, "The main cause of deserts is the Hadley Cells (and in a few special cases altitude). This is readily apparent by noting that the latitudes at which deserts occur are the same (above and below the equator) and is readily explained by the mechanics of the Hadley Cells."
    
    1. I never said that the Hadley cells weren't an important factor. They are not the only factor however, this is apparent when looking at this graph: http://www.ciesin.columbia.edu/docs/002-193/fig5.gif
    Notice the northern arid regions that are experiencing desertification.
    
    2. I feel like you are missing my argument, but because I have tried to explain myself (and you seemingly ignore my points) and you haven't posed any specific questions re the information I have presented, I will not elaborate further (unless you have specific questions or criticisms of the points I am making, of course).
    
    you said, "some of those arguments will be valid in some cases, but this does not change the fact that one major, unavoidable and already observed effect of global warming will be the expansion of the Hadley Cells, which will in turn necessarily and proportionally expand the existing deserts poleward."
    
    Well good, we are in complete agreement on this point.
65. DSL at 12:35 PM on 21 September, 2012
    Pardon my confusion, AHuntington. I was responding to this claim of yours @ 47:
    
    "From an ecological perspective, desertification is almost strictly a land management problem."
    
    and then especially this:
    
    "DSL, if you believe that human emissions of fossil fuels, and human errors such as overgrazing, deforestation, etc are causing desertification, you believe that all desertification is anthropogenic. Isn't this correct? What aspects of desertification are not anthropogenic?"
    
    and now you give me this:
    
    "I agree completely, and add that since humans have existed on earth, we have become a factor that can either rapidly intensify natural desertification and ecosystem breakdown, or promote biodiversity, and ecosystem growth."
    
    which I agree with. The second quote suggests that you were not aware of any natural mechanisms for desertification. I'm suggesting that you be a little more precise in your presentation. Your first quote could be excused because you did say "anthropogenic desertification" in the preceding paragraph. The second quote is an inexcusable non sequitur: it does not follow that if I believe the enhanced greenhouse effect can cause desertification that I then must believe that all desertification is human caused.
66. AHuntington1 at 05:32 AM on 22 September, 2012
    DSL, the second quote doesn't suggest that I am unaware of such mechanisms (which I already acknowledged, and explained how Hadley cell widening fits into my understanding of desertification). My point is that desertification as we know it is primarily dependent on the biodiversity of a given region, and the extent that humans choose to degrade or enhance the local ecology.
    
    Widening Hadley cells are responsible for some changing rainfall patterns, but any environment on earth that already experiences extreme temporal variations in moisture are at risk of desertification via human mismanagement of land (thus desertification spreads far beyond the Horse latitudes).
    
    Land management is at the root of desertification.
67. DSL at 05:40 AM on 22 September, 2012
    No, AH. It's best to be precise. Small-scale desertification can occur through land mismanagement. Large-scale desertification can occur through climate-scale changes in atmospheric and oceanic circulation. Land mismanagement is at the root of some types of desertification, but not desertification in general.
68. AHuntington1 at 06:32 AM on 22 September, 2012
    DSL, you said, " Land mismanagement is at the root of some types of desertification, but not desertification in general. "
    
    But it is (especially if you believe that human CO2 emissions cause Hadley cell widening)- changing rainfall patters or widening Hadley cells do not always cause desertification, ecosystems can and do adapt to changing rainfall patterns (a grassland, which can be much more tolerant of drought, can replace a rainforest and vice versa). The human element which directly reduces the efficiency of the water, mineral, solar, and decomposition cycles create desertification.
    
    So to be more precise, the vast majority of desertification is the result of mismanagement of land, as opposed to humans burning fossil fuels (burning trees and grass are land management issues).
69. DSL at 12:33 PM on 22 September, 2012
    AH, are you suggesting that humans are at the root of most of the desertification in the 4.5 billion years of Earth's existence? Perhaps you're thinking of desertification that has occurred only within the last couple of hundred years. Humans are not responsible for those big dry belts at the horse latitudes. Those dwarf any desertification caused by humans. Why am I counting standing deserts as desertification? Because those big circulation cells aren't permanent. Their development and shifting created deserts. Isn't this all a little obvious?
70. JasonB at 15:58 PM on 17 January, 2013
    Response to Clyde:
    
    Why do you think we need to be able to say AGW caused a particular extreme weather event?
    
    That's like saying we shouldn't warn people of the dangers of smoking until science can prove that a particular lung cancer sufferer developed lung cancer because they smoked and not because of any other reason.
    
    As your own link states, "the emerging ability, arising from improvements in climate models, to calculate how anthropogenic global warming will change, or has changed" is being watched with interest by "lawyers, insurers and climate negotiators" because "nations, communities and individual citizens may begin to seek compensation for losses and damage arising from global warming", but:
    
    

    It is more difficult to make the case for ‘usefulness’. None of the industry and government experts at the workshop could think of any concrete example in which an attribution might inform business or political decision-making.

    Response: [DB] Added hyperlink to referenced link.
71. snafu at 00:30 AM on 12 March, 2013

    I hope I have put this in the right place.

     

    At the risk of being accused of 'cherry-picking' single events, I ask everyone to take note of these dates;

    Typoon Tip -1979
    Marble Bar - 1923-24
    Furnace Creek Ranch (formerly Greenland Ranch) - 1913
    Oodnadatta, South Australia - 1960

    ...actually, instead of listing them, please go here;
    http://en.wikipedia.org/wiki/List_of_weather_records

    Now open the SkS trend calculator, HADCRUT4, 1850-2013, moving average - 1 month.

    I'm not interested in temps or trends as such, this is not a 'it's getting hotter or colder' question. I'd like you to take note of the 'extreme' weather events from the link above and see which period(s) the bulk of them occur in.

    Have weather events become more 'extreme'? Yes...............and it's not because of Global Warming.... ;) .

    Response: [JH] Please note that posting comments here at SkS is a privilege, not a right. This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum. Moderating this site is a tiresome chore, particularly when commentators repeatedly submit offensive or off-topic posts. We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site. Finally, please understand that moderation policies are not open for discussion. If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing. Please take the time to review the policy and ensure future comments are in full compliance with it. Thanks for your understanding and compliance in this matter.
72. Rob Honeycutt at 02:30 AM on 12 March, 2013

    snafu...   You know that you're not making a lot of sense here.  How do you come to the conclusion that weather events are getting more extreme but not because of global warming?

    Response: [JH] Snafu is also skating on the thin ice of sloganeering.]
73. Composer99 at 03:03 AM on 12 March, 2013

    snafu:

    At the risk of being accused of 'cherry-picking' single events [...]

    Got it in one.

    A handful of individual weather events is not the equivalent of a global aggregate of extreme weather events over long time frames.

74. scaddenp at 06:52 AM on 12 March, 2013

    Snafu - lets get this clear. Science works like this - you build hypotheses into models from which you make predictions. You test these predictions against the real data. Now you think you doing this. "Look AGW says xyz, and he is abc which shows its wrong". However, what you are really doing is constructing a straw man agument because climate models predict no such thing and all the handwaving in the world doesnt change that. So instead of constructing your own wild ideas on what the science predicts you could instead see what is actually predicted and compare that with systematic analysis of global records.

    So far you are sloganeering. Before we waste further time, perhaps we should ask whether data would change your mind or are you only looking for something to sure up an opinion that wasnt based on data in the first place?

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