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Positives and negatives of global warming

What the science says...

Select a level... Basic Intermediate Advanced

Negative impacts of global warming on agriculture, health & environment far outweigh any positives.

Climate Myth...

It's not bad

"By the way, if you’re going to vote for something, vote for warming. Less deaths due to cold, regions more habitable, larger crops, longer growing season. That’s good. Warming helps the poor." (John MacArthur)

Here’s a list of cause and effect relationships, showing that most climate change impacts will confer few or no benefits, but may do great harm at considerable cost.

Agriculture

While CO2 is essential for plant growth, all agriculture depends also on steady water supplies, and climate change is likely to disrupt those supplies through floods and droughts. It has been suggested that higher latitudes – Siberia, for example – may become productive due to global warming, but the soil in Arctic and bordering territories is very poor, and the amount of sunlight reaching the ground in summer will not change because it is governed by the tilt of the earth. Agriculture can also be disrupted by wildfires and changes in seasonal periodicity, which is already taking place, and changes to grasslands and water supplies could impact grazing and welfare of domestic livestock. Increased warming may also have a greater effect on countries whose climate is already near or at a temperature limit over which yields reduce or crops fail – in the tropics or sub-Sahara, for example.

Health

Warmer winters would mean fewer deaths, particularly among vulnerable groups like the aged. However, the same groups are also vulnerable to additional heat, and deaths attributable to heatwaves are expected to be approximately five times as great as winter deaths prevented. It is widely believed that warmer climes will encourage migration of disease-bearing insects like mosquitoes and malaria is already appearing in places it hasn’t been seen before.

Polar Melting

While the opening of a year-round ice free Arctic passage between the Atlantic and Pacific oceans would confer some commercial benefits, these are considerably outweighed by the negatives. Detrimental effects include loss of polar bear habitat and increased mobile ice hazards to shipping. The loss of ice albedo (the reflection of heat), causing the ocean to absorb more heat, is also a positive feedback; the warming waters increase glacier and Greenland ice cap melt, as well as raising the temperature of Arctic tundra, which then releases methane, a very potent greenhouse gas (methane is also released from the sea-bed, where it is trapped in ice-crystals called clathrates). Melting of the Antarctic ice shelves is predicted to add further to sea-level rise with no benefits accruing.

Ocean Acidification

A cause for considerable concern, there appear to be no benefits to the change in pH of the oceans. This process is caused by additional CO2 being absorbed in the water, and may have severe destabilising effects on the entire oceanic food-chain.

Melting Glaciers

The effects of glaciers melting are largely detrimental, the principle impact being that many millions of people (one-sixth of the world’s population) depend on fresh water supplied each year by natural spring melt and regrowth cycles and those water supplies – drinking water, agriculture – may fail.

Sea Level Rise

Many parts of the world are low-lying and will be severely affected by modest sea rises. Rice paddies are being inundated with salt water, which destroys the crops. Seawater is contaminating rivers as it mixes with fresh water further upstream, and aquifers are becoming polluted. Given that the IPCC did not include melt-water from the Greenland and Antarctic ice-caps due to uncertainties at that time, estimates of sea-level rise are feared to considerably underestimate the scale of the problem. There are no proposed benefits to sea-level rise.

Environmental

Positive effects of climate change may include greener rainforests and enhanced plant growth in the Amazon, increased vegitation in northern latitudes and possible increases in plankton biomass in some parts of the ocean. Negative responses may include further growth of oxygen poor ocean zones, contamination or exhaustion of fresh water, increased incidence of natural fires, extensive vegetation die-off due to droughts, increased risk of coral extinction, decline in global photoplankton, changes in migration patterns of birds and animals, changes in seasonal periodicity, disruption to food chains and species loss.

Economic

The economic impacts of climate change may be catastrophic, while there have been very few benefits projected at all. The Stern report made clear the overall pattern of economic distress, and while the specific numbers may be contested, the costs of climate change were far in excess of the costs of preventing it. Certain scenarios projected in the IPCC AR4 report would witness massive migration as low-lying countries were flooded. Disruptions to global trade, transport, energy supplies and labour markets, banking and finance, investment and insurance, would all wreak havoc on the stability of both developed and developing nations. Markets would endure increased volatility and institutional investors such as pension funds and insurance companies would experience considerable difficulty.

Developing countries, some of which are already embroiled in military conflict, may be drawn into larger and more protracted disputes over water, energy supplies or food, all of which may disrupt economic growth at a time when developing countries are beset by more egregious manifestations of climate change. It is widely accepted that the detrimental effects of climate change will be visited largely on the countries least equipped to adapt, socially or economically.

Basic rebuttal written by GPWayne


Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

 

Last updated on 5 July 2015 by pattimer. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

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Related Arguments

Further reading

National Geographic have an informative article listing the various positives and negatives of global warming for Greenland.

Climate Wizard is an interactive tool that lets you examine projected temperature and precipitation changes for any part of the world.

A good overview of the impacts of ocean acidification is found in Ken Caldeira's What Corals are Dying to Tell Us About CO2 and Ocean Acidification

Comments

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Comments 276 to 300 out of 404:

  1. Stephen Baines, I might have slightly misunderstood your question. Co2's ability to dilate the blood vessels allows for more blood (with less O2) to flow, equalizing the loss of O2 per hemoglobin. Contrast this with more O2 (in relation to Co2), which causes blood vessels to constrict and hemoglobin to horde O2.
  2. AHuntington1 wrote: "Fact 3 is true, but also irrelevant as I did say all else being equal (I have been repeating this to no avail)" Yes... because it is observed reality that all else is not equal. Ergo, your entire line of argument is a meaningless diversion into fiction. Yes, if gravity did not exist then people could 'fly' about with ease... but why exactly do you want to talk about things which are not true? So yes, truth and reality are "irrelevant" to your position. Which is rather the problem.
  3. AHuntington1, I have no intention of re-reading your posts, because they weren't worth reading the first time. Your high opinion of yourself does nothing to raise my opinion of you. Fact 1 is not opinion, it is something you need to disprove if you want to advance your pet theory. Your complete dismissal of facts 2 through 4 demonstrate that you are living in a fantasy world of denial, which explains how you can present the amazing Gish Gallop that has taken you to this point and still expect to be taken seriously.
    ..then we basically agree, and you will stop posting strawmen, yes?
    Thanks for that closing comment, because it perfectly illustrates my point that your posts are full of debate tricks. You are playing games with words and any reader that cares to step back and look at what you've written can easily recognize this. Thanks for making it so obvious. Given this, please spell out the strawman argument that you claim I have created. Fact: The influences of climate change on crops, temperature and water availability, and hence the dangers to the human food supply, far, far, far outweigh any tangential and as yet ill-defined (by you) supposed benefits of improved respiration. Hence, your entire argument falls flat. You've spent hundreds and hundreds of words arguing about what amounts to an inconsequential detail.
  4. AHuntington1,
    If you think that mitochondrial efficiency is not beneficial, I don't have much to say.
    I have no idea if it's beneficial or not because you haven't presented any actual evidence one way or the other. If my cells are getting all the oxygen they need, making it easier to get more probably isn't going to make a difference. If you're trying to convince others of something, saying "I don't have much to say" is an odd tactic to use when you haven't yet provided any evidence to convince them.
    Do you really think that less ATP is better than more?
    I don't know, but I suspect there is probably a point where more ATP provides no additional benefit, in the same way that providing more water to an organism beyond a certain point provides no additional benefit. What I don't know is whether we are ATP-starved and there is additional benefit to be had, and what that benefit might be.
    Look at the higher metabolic rates of people living at high altitudes and the epidemiological data regarding these people.
    Gladly. Where is it?
    One positive example is the generally lower mortality rates among them. This is good evidence to support the hypothesis that a higher metabolic rate is beneficial.
    I look forward to seeing that evidence. I was under the impression that higher metabolic rates led to more oxidative stress and shorter lifespans, and that this was why animals that were slightly starving all the time lived notably longer than animals that were well fed (without being overweight).
    He attacked a big straw-man, and then painted a picture of me literally mocking a starving and dehydrated human being crawling through the desert. If Sphaerica wasn't displaying an irrelevant appeal to petty emotionalism, I have never seen one- and that behavior is not appropriate in any discussion, let alone a scientific one.
    Note that Spaerica was making the very valid point that all else is not equal, and that given the other effects of higher CO2 levels include drought and heat, it's a bit pointless telling an organism suffering from those other known effects that they should be glad of the possibly slight beneficial effect they are also experiencing. It wasn't an appeal to emotionalism, it was putting your claims into context so the net effect of higher CO2 levels is more apparent.
  5. AHuntington1 Sorry this is getting tiresome. I asked for evidence that the mechanism you mention actually has a significant benefit in vivo and you still have provided precisely nill. Epidemiology of those living at altitude is not evidence that the differences between population are due to differences in CO2, so it is a non-sequitur. I am willing to accept your point about increased metabolic activity, but you are still expecting me to take your word for it that (i) the observed increase in atmospheric CO2 has even a measurable effect on metabolism and (ii) that increase matabolism is purely beneficial. If there were a measurable effect from the sort of changes in CO2 that are likely to ocurr due to anthropogenic emissions then it should be a cause for some skepticism for you that you don't seem to be able to point to a study that directly proposes this mechanism or demonstrates evidence to suggest it is significant.
  6. I note that AHuntington1 continues to fail providing scientific references to his assertions. His argument seems to consist of associating a supposed higher efficiency of mitochondria when exposed to higher levels of CO2 with overall benefit for animal and human health, together with increased oxygen delivery due to the vasodilatory effect of CO2. It seems a little self contradictory, is beyond a stretch and is not supported by the litterature as far as I could tell. In fact, the whole argument is rather confused and conflates different reactions as well as apparent assumptions. AH1 asserts that people living at high altitude experience an increase CO2 to O2 ratio in their blood compared to low altitude dwellers. I could not find articles supporting that assertion. All known adaptations to high altitude, whether short or long term, are responses to hypoxia and physiological solutions to hypoxemia. I searched "lactate paradox" and found rather a lack of knowledge than anything allowing to make sweeping statements on whole body response, let alone mitochondrial metabolism. Interestingly, one study found increased mitochondrial efficiency, but associated with low levels of carbon monoxide. http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0041836 As I could recall, vasodilation/constriction regulation is quite complex and involves both O2 and CO2, but also NO, and effects are different at the central and peripheral levels. If regulation is normal, there is no reason to believe that the range of O2 and CO2 will vary from what we need, since regulatory response will keep the levels where they need to be. People with COPD, who live with high levels of CO2, are not known to derive benefits from the higher CO2. This treats of O2 mediated vasoregulation: http://ajpheart.physiology.org/content/295/3/H928.full I have so far not found articles treating of mitochondrial metabolism's response to increased CO2. Other chemicals, however, are the subject of intense study. Studies of high altitude functional adaptation do not make much mention of mitochondrial metabolism either. However, it is worth noting that prolonged stays at high altitude lead to decreased density of mitochondrial populations, as well as reduced muscle mass (references below). The possibility of increased mitochondrial efficiency has been proposed but, to my knowledge, not investigated, and in any case would be associated with a decreased mitochondial population density, so the overall benefit is highly dubious. It has more signs of being an adaptation to the intense stress of hypoxia. Here are a few references on the subject, and about the so-called "lactate paradox", which does not appear to show in all situations. http://jap.physiology.org/content/83/2/661.abstract http://www.bio.davidson.edu/Courses/anphys/1999/Dickens/Dickens.htm http://www.ncbi.nlm.nih.gov/pubmed/19139048 http://www.ncbi.nlm.nih.gov/pubmed/1623889 It also appears that ventilatory response to CO2 is not significantly different among altitude acclimated subjects, although it is slower. Some hypotheses as to why that may be are briefly discussed at the end of this paper: http://jap.physiology.org/content/94/3/1279.full.pdf
  7. Philipe Chantreau, talking past me and scoffing at my claims, without refuting them (or even addressing the evidence I present), does not prove anything. What specific assertion have I made that is “confused” or “conflates different reactions as well as apparent assumptions”. If you don’t tell me what you are referring to, I will not know what it is (nor will any other reader). Of course adaptations to higher altitudes are responses to hypoxia of varying degrees (adapting to mild hypoxia provides the benefits that athletes who train at high altitudes exploit). Mild hypoxia would be the result of increased internal Co2 to O2 concentrations (but the Co2 would protect from severe hypoxia to an extent). I have read the Everest study on mitochondrial density, how do you square that with studies like this? http://www.sciencedirect.com/science/article/pii/0034568770900113 To quote, “Hearts of domestic cattle from two groups, one born and raised at sea level and the other born and raised at an altitude of 4250 m, were studied to determine whether any mitochondrial adaptations to high altitude could be demonstrated. Direct counts of mitochondrial number revealed a 40 % increase in the high altitude hearts [..]” Here is some information on altitude training published by San Diego State University. http://coachsci.sdsu.edu/csa/vol24/table.htm To list some information presented in the link: “ALTITUDE USES MORE GLUCOSE THAN SEA-LEVEL Brooks, B. A., Roberts, A. C., Butterfield, G. E., Wolfel, E. E., & Reeves, J. T. (1994). Altitude exposure increases reliance on glucose. Medicine and Science in Sports and Exercise, 26(5), Supplement abstract 120.” This implies increased Kreb’s Cycle activity at high altitudes. “ALTITUDE DECREASES RELIANCE ON FREE FATTY ACIDS AND INCREASES DEPENDENCY ON BLOOD GLUCOSE Brooks, B. A., Roberts, A. C., Butterfield, G. E., Wolfel, E. E., & Reeves, J. T. (1994). Acclimatization to 4,300 m altitude decreases reliance on fat as a substrate and increases dependency on blood glucose. Medicine and Science in Sports and Exercise, 26(5), S21, Supplement abstract 121.” This implies increased Kreb’s Cycle activity at high altitudes. The lactate paradox not showing up in every instance does not disprove my claim that adaptation to high altitudes (therefore exposure to lower internal O2 to Co2 ratios, capable of inducing mild hypoxia) increases krebs cycle activity. You said, “This treats of O2 mediated vasoregulation: [..]” -I don’t quite see what your point is here, would you mind elaborating a bit? You also said, “It also appears that ventilatory response to CO2 is not significantly different among altitude acclimated subjects, although it is slower.” -Well, yea (and what do you mean by “it is slower”?). Why would the ventilatory response differ among people already acclimated to high altitudes? The study you posted did find a difference between high altitude natives and people living at sea level. To quote your study, “The major findings of this study were as follows. First, under conditions of euoxia (PETO2 _ 100 Torr), total ventilatory sensitivity to CO2 in HA natives is around double that of SL natives at SL.” So, would you mind elaborating a bit more on your point here? You need to be more specific in your criticism for me to be able to address your concerns. Dikran Marsupial, I have provided evidence for Co2’s antioxidant effects (in vivo) and Co2’s ability to increase oxygenation of tissues in vivo via the Bohr effect. Here are in vivo studies supporting Co2’s role as a fat soluble antioxidant. http://www.ncbi.nlm.nih.gov/pubmed/7770796 http://www.ncbi.nlm.nih.gov/pubmed/7581542 And here are some in vitro studies. http://www.ncbi.nlm.nih.gov/pubmed/9190222 http://www.ncbi.nlm.nih.gov/pubmed/9139450 Also consider therapeutic hypercapnia- boosting internal CO2 levels- to avoid lung injury. http://ajrccm.atsjournals.org/content/168/11/1383.full Interestingly (to quote the above link), “Acidosis, notably hypercapnic acidosis, is protective against organ injury in multiple experimental models”. This might explain the lower mortality rates in people at high altitudes. On question (i), adaptation to hypoxia does affect metabolism (see above links), and increasing internal CO2 to O2 ratios will induce this adaptation (via mild hypoxia). High altitudes are one perfect example of this. That leaves (ii); I cited the higher metabolic rates of people living at high altitudes, and the fact that they experience lower mortality rates. (see the wiki link I posted earlier and http://circ.ahajournals.org/content/120/6/495.full ) These at least correlate increased metabolism with lower mortality rates. Do you have any evidence suggesting higher metabolic rates to be harmful? Or which suggest less ATP produced per glucose being beneficial in comparison to more? JasonB, you said, “I was under the impression that higher metabolic rates led to more oxidative stress and shorter lifespans” -Oxidative stress is dependent on many environmental factors, luckily Co2 is an antioxidant; supporting oxidative metabolism on the one hand and reducing oxidative damage on the other. Even if that theory is correct, Co2 would be protective. Look at the Wikipedia link I posted earlier, and the above link for evidence of reduced mortality rates among those at high altitudes. I will re-post the link I cited earlier regarding the higher metabolic rates of people at high altitudes here: http://jap.physiology.org/content/16/3/431 You said, “Note that Spaerica was making the very valid point that all else is not equal,” -It is actually a completely invalid and irrelevant strawman that Spaerica built up against me, which you have now started attacking. To repeat myself (again), I am not making a judgment on the overall cost-benefit analysis, I am making a specific biological argument, in a specific context. I am only asking for this point to be included in the analysis (just like other ceterus paribus arguments which have already been included). The amount of resistance I am encountering when making this point is quite odd for the comments section of a website called skepticalscience.com; the inability to recognize my argument, as I have laid it out, characterizes dogmatism. CBDunkerson, See above strawman. Spaerica, See above strawman. Also, I am getting tired of reading attacks against my writing style, and accusations of “gish gallop” and various logical fallacies without making any attempt to specify what part of my argument you are actually attacking. My writing style is practically meaningless compared with the content of my argument (which you have consistently ignored) and attacking it borderlines on ad hominem. I will not reply to any more or your posts, unless you actually specify what you are talking about- unless you have something to say about the information I present. ..Geez, sorry for the long post. thx
  8. Taking the conversation back to square one on "C02 is a metabolic benefit," leaving aside whether that's true or not is it your assertion ahuntington1 that metabolic benefits of C02 are worth wholesale modification of Earth's atmosphere with attendant knock-on effects? Can you describe specifically how my day might be so much better breathing an atmosphere with a higher C02 concentration that the disadvantages are outweighed? Once you've shown in concrete terms how I'd stand to benefit from increased C02 respiration, next you need to show how confident you are in your predictions. Guaranteed? Maybe? A long shot? What's the risk/benefit equation here, in other words?
  9. doug_bostrom, you asked, "is it your assertion ahuntington1 that metabolic benefits of C02 are worth wholesale modification of Earth's atmosphere with attendant knock-on effects?" No, that is not my assertion. Where did you read that; can you quote me saying that? I am not making predictions on net effects. In fact, the more you make predictions on net, potential, future effects the higher propensity you have to be wrong. As to how increasing Co2 might help you in your daily life (whether through higher atmospheric levels or "therapeutic hypercabia") is up for you to decide for yourself, based on the available information and your specific health status. The same is true for Vitamin C, D, retinol and calcium. You asked, "What's the risk/benefit equation here, in other words? " I don't know (nor have I claimed to know), but the beneficial aspects of higher atmospheric Co2 should at least be part of the cost-benefit analysis.
  10. *edit, post 284. "I don't know (nor have I claimed to know), but the beneficial aspects of higher atmospheric Co2 should at least be part of the cost-benefit analysis." should read, "I don't know (nor have I claimed to know), but the beneficial aspects which higher atmospheric Co2 would exhibit on mitochondrial respiration should at least be part of the cost-benefit analysis." -thanks
  11. Well, emulating your level of justification for claiming that metabolic benefits of C02 should be considered w/regard to climate change--namely none-- then I claim we should consider the thermal expansion of the dry land on Earth in response to climate change as a possible benefit. Work it out; it's a surprising number. On the other hand, just as with speculation on how we might enjoy breathing more C02, there are downsides to all the thermally gifted "free land." For every km2 we get in handily expanded dry land we lose way more in freshly drowned land. Which leads to the further benefit of increased marine habitat, I suppose. Doubtless somebody's pushing that idea, too.
  12. ...edit 284. should read "therapeutic hypercapnia" ...my bad
  13. doug_bostrom, that is an interesting theory. Not to get too off topic but, I must ask, what do you mean by "For every km2 we get in handily expanded dry land we lose way more in freshly drowned land."? Would this be the result of increased evaporation and H2O in the atmosphere? Are you saying that total rainfall would increase on the planet during heating due to the greenhouse effect? (i vaguely remember reading something about Co2 causing the greenhouse effect which would cause increases in water vapor, which would wildly exasperate the greenhouse effect) Is this essentially the theory you refer to?
  14. doug_bostrom, you said, "emulating your level of justification for claiming that metabolic benefits of C02 should be considered w/regard to climate change--namely none--" This is ridiculous. Just saying that I have no justification, after I repeatedly provide it is willful ignorance (or just poor communication). What aspect of my argument is flawed? What are you talking about, specifically? If you can not be specific, you probably are dealing with an emotional attachment to a belief.
  15. Honestly, the metabolic benefits of Co2 to plants already is considered here. Why should the metabolic benefits of Co2 in relation to animals/bacteria not be considered? This is the question you must answer. Or you could dispute the information I present.
  16. Why should the metabolic benefits of Co2 in relation to animals/bacteria not be considered? What, with no actual claims attached? You've just said upthread that you make no conjectures on what might specifically happen in the way of metabolic benefits. How does one evaluate "it might be good?" W/regard to my "free land is good" argument vs. the "drowning land is bad" negative aspect, I'm sure you're aware of the sea level issue? Another thermal expansion problem, unfortunately, coupled w/ice loss.
  17. Doug_bostrom, If I did make such a concession, it was a typo. My claim is that elevating Co2 within a certain range increases kreb's cycle efficiency (metabolic rate), thru its antioxidant activity and its role in increasing the efficiency of oxygen distribution to the tissues via Bohr principle (as I have said many times).
  18. Ahuntington1: I am not making predictions on net effects That's a remarkable typo. Reminds me of the epic crash of the ski jumper that was shown as part of the program intro for ABC Sports events. Just seemed to go on forever!
  19. doug_bostrom, let me clarify my meaning here, I am not making predictions on net effects regarding the overall cost benefit analysis of anthropogenic Co2 emissions. I am making a claim on the specific effects that elevated Co2 has on the organism, which should be included in any cost benefit analysis. I am not claiming that anthropogenic Co2 emissions are either good or bad- overall. A missing factor in any cost benefit analysis can skew the result one way or the other. Does that help clear up the issue?
  20. when I say overall, I mean including every other potential factor (eg. maybe the analysis would add points for increased rates of mitochondrial respiration and take points off for old people dying of heat stroke).
  21. No, it doesn't help anything. You refuse to specify the benefits you anticipate from additional C02 in the atmosphere.
  22. AHuntington1 I offer this as helpful advice. SkS is interested in a fair portrayal of the science. We would also wish these metabolic benefits to be considered if there is good evidence to suggest they actually exist. So far you have pointed to a mechanism that suggest that there may be an effect, but have not provided any evidence that unequivocally suggests there is a measurable effect in vivo all things being otherwise equal. Evidence of a change in glucose metabolism at altitude is not evidence of this as there all things are not equal as the reduction in atmospheric pressure means there is less oxygen, rather than just higher CO2. It doesn't surprise me that respiration is less efficient at altitude (as we are not evolutionarily highly adapted to life at altitude) and therefore requires more energy. As a result, we are skeptical of you claims, but are willing to be persuaded. Is there anyone other than yourself that is currently proposing this hypothesis?
  23. My understanding of AHuntington1's position so far: 1. CO2 will improve mitochondrial respiration, which he presents with evidence of small scale, controlled and very focused laboratory experiments. 2. His statement is presented without any evidence of an actually realized positive benefit in at least some living creatures, and certainly not all. 3. He self-admittedly makes no statement of the ultimate value of this benefit in the real world because he has not/will not put it into the context of all of the real world negative impacts that will accompany such a "benefit." 4. He has not (presumably because he agrees it does not exist) presented any evidence that such a benefit would mean that increased CO2 levels will ultimately be more beneficial than harmful to human civilization (which, in the end, is the whole point, isn't it?).
  24. On another thread AHuntington1 and DSL were debating the potential of Hadley cell expansion to cause drying in the horse latitudes which would be considered a negative consequence. While Hadley cells are expanding, the expansion is seasonal and it is unclear what will happen in the future, see http://journals.ametsoc.org/doi/pdf/10.1175/2009JCLI2794.1. The effects of measured expansion in the Hadley cells depends greatly upon geography. The result over the ocean is fairly certain, there has been expansion. The result over land is very uncertain, see for example http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2538841/ in which they state that the greening of the Sahel is a potential (and rare) example of a beneficial tipping point. See section starting with "Sahara/Sahel and West African Monsoon (WAM)" and note that there are large uncertainties. Reading these two references I'm not even sure that Hadley expansion has any relevance at all in the Sahara and Sahel.
  25. No, Eric. I was objecting to AHuntington's apparent claim that desertification was a primarily human-caused phenomenon.

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