1  2  Next

Comments 1 to 50 out of 87:

1. Camburn at 19:28 PM on 7 March, 2011
   Without knowing the underlying data used to make this little program, the results are pretty much worthless.
   0 0
   Moderator Response: [Daniel Bailey] Do you have something constructive to offer besides the obligatory drive-by handwaving? As it stands, your comment contributes nothing to the dialogue on this thread.
2. Camburn at 19:30 PM on 7 March, 2011
   The supposed underlying data ref IPCC is based on models which is based on more models. That is what I meant by underlying data. Models are not data but only assumptions.
   0 0
3. Dikran Marsupial at 19:38 PM on 7 March, 2011
   As we have no data for future climate (as it hasn't happened yet), please explain how we can forecast the effects of climate change on agriculture without a model? Nobody thinks that model output is data. Models exist to demonstrate the consequences of a set of assumptions regarding climate physics; they also allow our understanding of climate physics to be falsified, by making testable predictions. Disregarding any argument just because it involves the use of models is deeply unscientific.
   0 0
4. Paul D at 19:53 PM on 7 March, 2011
   Maybe my eye sight is worse than I thought. But the variable is temperature, in fact the text says: Mean Local Temperature Change. Which suggests to me that the interactive educational tool is designed to show what would happen with a temperature change. Indeed, I can reduce the temperature to zero. Possibly the only fault is that it doesn't go into negative temperatures. Given that the vast majority of scientists understand the physics of temperature change and the effects. I would think the results are obvious. After all is it not skeptics that attach great meaning to the ability of growing grapes in different climates? Or are comments 1, 2 and 3 suggesting skeptics are using a poor metric for judging climate?
   0 0
5. Dan Olner at 19:58 PM on 7 March, 2011
   DIkran: "Nobody thinks that model output is data. Models exist to demonstrate the consequences of a set of assumptions." I'm stealing that sentence for my thesis! Seriously, no-one *should* mistake model output for data but you'd be amazed (or maybe you wouldn't) how muddled people's thinking is on this.
   0 0
   Moderator Response: [Dikran Marsupial] Glad to hear I have done something useful this morning! ;o)
6. Paul D at 20:53 PM on 7 March, 2011
   I should have said in 4 that the temperature can be set to zero temperature change, rather then zero temperature.
   0 0
7. Byron Smith at 22:29 PM on 7 March, 2011
   What surprised me was how well crops did, especially at higher latitudes. I was under the impression that almost any temperature rise was bad for agricultural output in the tropics and almost anything much above 1ºC was bad in temperate regions. It would be useful to know the percentage of global production found in each of the two regions, in order to be able to calculate the global effect of different temperature changes. Also, is this only for the Northern Hemisphere? Or is the graphic simply misleading?
   0 0
8. Byron Smith at 22:30 PM on 7 March, 2011
   (When I speak of crops going well, I meant in comparison to my impression from having read a bit on this topic previously. Obviously, after a certain point things are grim no matter how well we adapt. It was just that that point was a little higher than I had previously thought.)
   0 0
9. Byron Smith at 22:36 PM on 7 March, 2011
   Of course, it is also critical to notice that the temperature change in the thermometer is *local*, which means that my earlier reading was not actually so misleading after all! A *global* temperature rise of 1ºC is probably sufficient in most areas to push *local* land-based temperature rises above the point of where crop effects are positive or neutrality and into deficit, since (a) local temperatures over land increase faster than over oceans and (b) local temp rises generally increase relative to the global average for higher latitudes (especially in the Northern Hemisphere). So in terms of the big picture, going much beyond a 1ºC global rise would likely mean net crop losses, even with adaptation.
   0 0
10. Camburn at 01:41 AM on 8 March, 2011
    Yes, I have something to add Daniel. The timeing of any heat units is critical to how plants respond. Without knowning the underlying metrics that this model is based on, the model us quit useless. The IPCC model is not temperature specific. I will use one crop as an example: Wheat. Wheat likes cool weather when it is tillering. Once tillering has completed, it likes warm weather. Flowering wheat, which is the reproductive period, likes dry weather as any moisture contributes to leaf disease and fusarium. Once wheat has finished flowering, a shot of rain is good and warmer temps once again are desired. It is about timing of heat units. I was not surprised to see a rise in production from more warmth. That is pretty much a given. The added co2 also contributes to a rise in production. Without more information on how this program was constructed it is impossible to see if the results are credible. As a side note, I am a farmer. Hence, I recognize what is required.
    0 0
    Moderator Response: For some scientific studies of the effects of CO2 and heat, see the summary by the U.S. Dept. of Agriculture, and other studies, linked in the comments of the thread "CO2 is not a pollutant."
11. Philippe Chantreau at 01:50 AM on 8 March, 2011
    "The added co2 also contributes to a rise in production." There is little to no evidence showing this to be true in the fields. Commercial greenhouses using enhanced CO2 to increase yields have to use 800 to 1200 ppm concentrations to see any results, with all other factors being optimized.
    0 0
12. michael sweet at 02:53 AM on 8 March, 2011
    We need to keep in mind that this is a simple model. As Camburn pointed out, CO2 fertilization might further increase production while lack of rain, or floods, would lower prduction. On the other hand, this model gives a starting point so we know what we need to deal with. Perhaps more irrigation would be enough to adapt if water is the main limiting factor. If no irrigation water is available we might need to move. If heat alone is the limiting factor we need new cultivars that are heat resistant or we must switch to other crops. This model is not the final word, it is a learning exercise.
    0 0
13. stevee3906 at 03:09 AM on 8 March, 2011
    It is a very simple model. Yet it provides answers to a tenth of a percent. Soil types, soil status, diseases, fertilizers, timing of moisture and weather, seed types, temperate zones all play a role. As I side note, I plant 1,000 trees every spring. In Northern Minnesota the limiting factors are summers to short and too cool, and winters too long and too cold.
    0 0
14. RickG at 03:11 AM on 8 March, 2011
    Camburn: I was not surprised to see a rise in production from more warmth. That is pretty much a given. The added co2 also contributes to a rise in production. One thing to consider is that a number of fruit trees require a minimum number of days below a certain temperature during winter or they will not produce in the spring/summer. As for annual crops, are you familiar with the Keeling curve? See graph below: peaks in the curve are winter while valleys are summer. Crops and other vegetation take up CO2 during the summer but release it during the winter through decay. Any extra CO2 intake by plants will be released after the growing season.
    0 0
15. Camburn at 04:05 AM on 8 March, 2011
    Rick: Grains crops benifit from higher levels of co2 during the growing season. As you can see from your chart the level of co2 is now higher than in the recent past. If you were to look at world vegitation maps/health you would see that there is a trend to increased health worldwide of plants. This is in reponse to higher levels of co2. I don't have the studies at hand, but there have been field studies done in the US as to what happens to corn growth and grass growth with higher levels of co2, everything else remaining constant. The response is quit good. My main point is to the usefullnes of the application presented. There are so many variables that affect plant health that using temperature as the metric does not produce a meaningful result. If everything else is constant, then one could surmise that the results of the graph show that more heat is good for ag output.
    0 0
16. RickG at 04:21 AM on 8 March, 2011
    Camburn, I would think the model is based on normal agricultural conditions with temperature being the primary variable. In that respect it would be useful. However, I think the danger with a warming and changing climate is that agricultural zones will also change; therefore, migrate. With growing global population and urbanization, there is are few places left where they can migrate were agriculture is possible.
    0 0
17. Bob Lacatena at 04:57 AM on 8 March, 2011
    I think one major failing in the model, one which can make climate change seem good by increasing crop yields, is the question of appropriate precipitation ("appropriate" as in how much, how often, and at what time of year from the crop's perspective). That is probably part of the difference in the low/mid/high latitude setting, but since precipitation changes aren't entirely governed by latitude, I'd rather see something just a little more elaborate... either a "precipitation gauge" which responds in concert to altering temperature (i.e. not a control itself -- you change temperature, and that changes precipitation) with a range of changed values, and therefore a range of expected crop yield due to the precipitation range, or else perhaps more simply 3 or 4 separate "crop yield" boxes (zones), to represent various general climate zones ("wet", "arid", etc.), perhaps each with a percentage to show how much of the world will fall into that category in various scenarios. I guess my main point is that I think that changes in precipitation are a far more important and damaging factor in the long run, and it's the intersection of the two (temperature and precipitation changes) that are going to really hurt crop yields... you have to get better temperatures and better precipitation to increase crop yields, while only one of those two needs to drop to greatly reduce crop yields. And in fact, in some circumstances what would otherwise be a productive increase in temperature but combined with a reduction in precipitation, even if only for a several week span during an important part of the growing season, could exacerbate the precipitation problem and make things worse. That is, the effects of changes in temperature and moisture aren't simply additive, but interact in a complex way.
    0 0
18. Chris G at 06:14 AM on 8 March, 2011
    Camburn, "I was not surprised to see a rise in production from more warmth. That is pretty much a given." Yes, because we've all seen how the increased warmth in Russia lead to higher yields last year. On a more serious note, I'm curious to know if the model accounts for precipitation shifts. I'm guessing not really, but I would expect that changes in the pattern of precip would have a more dramatic affect that changes in mean temperature. For instance, this year China is having a drought that will affect their wheat production. There are good indications from the field lately that rain bands are on the move in response to higher temperatures.
    0 0
19. Paul D at 09:27 AM on 8 March, 2011
    Generally, agriculture is an 'artificial' system that can be manipulated to a certain extent by humanity to mitigate climate change, largely by planting different crops as climate changes, or 'engineering' new varieties. A bigger problem is crop migration to the point where some areas may not be suitable any more for any agriculture. SO it isn't a case of less productivity from a crop, but elimination of some land from the agriculture 'bank'. This has nothing to do with traditional agriculture cycles and seasons, posed by Camburn. It is more to do with a complete break down of such cycles in certain areas of the world. Another big problem is the capacity of wild/natural species to adapt. People do not depend solely on agriculture, we are dependent on a wide bio-diverse environment. As that bio-diversity reduces, as one species is lost, it knocks out a whole chain of other species. Alternatively, you can get a massive destructive increase in a species if it's 'predator' is eliminated. Effectively warming is one massive hard to predict experiment, with many risks.
    0 0
20. Glenn Tamblyn at 10:29 AM on 8 March, 2011
    Sphaerica's comment about precipitation is critical, and it is unclear wheter this model includes that. It is relevent that the crop that does best at high temps is rice, which is the highest water user.
    0 0
21. adrian smits at 12:13 PM on 8 March, 2011
    The problem with this graph is that it models local temperatures.However the models indicate almost no warming at lower latitudes with increased warming at higher latitudes where millions of acres of land will suddenly become arable because of increases in temperature.A careful study of the graph would seem to indicate a huge net gain in food production for the planet in a warming world.As a farmer I know that you need heat units to grow crops and the corn belt in north America has been moving north for years.We consider this a blessing that allows us to grow crops with higher yield and it gives us a greater choice as to what we can grow.
    0 0
22. adrian smits at 12:30 PM on 8 March, 2011
    My understanding about rising c02 levels and precipitation is that the two will largely mitigate each other.If there is a reduction in rainfall that should be compensated for somewhat by crops that are more drought resistant because of higher c02 levels.
    0 0
23. Camburn at 13:19 PM on 8 March, 2011
    adrian: That is what current research shows. The higher levels of co2 result in fewer stoma which results in less transpiration. There are wild wheat grasses that have this gene that show this effect presently. Wheat and corn breeders have been trying to incorporate this gene for some years now into new hybrids. The thinking is that there should be an impressive yield response to this.
    0 0
24. muoncounter at 13:20 PM on 8 March, 2011
    adrian s, "My understanding about rising c02 levels and precipitation ... the two will largely mitigate each other" Your understanding appears to be incomplete. See the thread Water vapor is the most powerful greenhouse gas, where you will find that water vapor amplifies CO2-driven warming in a process known as 'feedback.' This is the water vapor that is the precursor to what you hope for in terms of relief from rainfall.
    0 0
25. Camburn at 13:20 PM on 8 March, 2011
    But now we have drifted into agonomy rather than this application.
    0 0
26. Camburn at 13:23 PM on 8 March, 2011
    muoncounter: I agree, water vapor is by far the most powerful greenhouse gas. Everything else pales against it. What research has shown is that the plants require substantially less moisture with higher co2 levels to produce the same yield. The hope is that if moisture stays somewhat constant that yields will increase by 18-22% if memory serves me.
    0 0
    Moderator Response: [DB] Actually, CO₂ is the Star Actor (the principal control knob) on the planetary thermostat stage; water vapor plays a supporting role in warming the atmosphere. If one removes the CO₂ from the atmosphere, global temperatures plunge by more than 30°C in the first 10 years alone (and the resulting increase in global ice turns the planetary albedo a whiter shade of pale):

    Lacis et al 2010

27. michael sweet at 13:56 PM on 8 March, 2011
    Camburn: "If memory serves me" is not a reference. Please give a link that supports your unusual claim. Peer reviewed papers are convincing. "memory" is not.
    0 0
28. Camburn at 14:05 PM on 8 March, 2011
    Ok....I was too low. This from an article in a farm magazine. I will have to dig to find the experiments done. "•Cereal grains including rice, wheat, barley, oats and rye average between 25 and 64 percent higher yields under elevated CO2 levels."
    0 0
29. Camburn at 14:10 PM on 8 March, 2011
    I did a quick google. Here is one result. As you can see, this is complicated. Unless you are a farmer and want to stay abreast of this, most won't care. There have been numerous studies done by universities in the US concerning co2 and growth/health/yeild etc. http://news.illinois.edu/news/09/0209co2.html
    0 0
30. Camburn at 14:14 PM on 8 March, 2011
    I will state this and then have to head to bed: Each study I have read concerning co2 and plants results in a higher level of co2 being benifical for plant growth. It appears that plants must have evolved during a time when co2 levels were substantially higher than present. Their growth response to co2 is almost like a growth response to nirtrogen/phosphorous etc. People who grow food in greenhouses have known this for years and elevate the level of co2 to compensate. It is not yet practical on a commercial farm scale to do so. If it was, it would have been done.
    0 0
31. adrian smits at 14:18 PM on 8 March, 2011
    Camburn is right Michael I have read similar articles.In fact adding c02 to greenhouse air is standard practice because it increases yields dramatically.
    0 0
32. johnd at 14:26 PM on 8 March, 2011
    With at least two contributors to this thread known to be real world farmers, this allows some balance to be bought to the subject which is otherwise only about theoretical models based on a few assumptions, some perhaps not even the most relevant. Theories and formulas founded on laboratory experiments ultimately have to be validated against the knowledge accumulated by such real world farmers who operate in a infinitely more variable environment than any lab can recreate. That knowledge is very often supported by reliable data going back generations covering a wide range of variable conditions in an otherwise constant environment, one that is generally very well measured for all the relevant parameters required. As has already been pointed out, there are many more important variables that have to be taken into account, if not for the projections being made, then certainly to allow the models to be calibrated against past data. Numerous free air carbon enrichment field trials are providing some such data, IIRC, the existing models generally failing to reliably forecast the increased yields many such trials produce. Most of the debate about climate change revolve around statistics, theories and formulas, and peer reviewed papers. But there is a real place in the debate for those people, those with dirt under their fingernails, who are in the unique position to be able see whether the way the climate performs in theory is how it actually manifests itself on the ground. Talking of ground, whilst agriculture depends on conditions that exist at ground level and below, virtually none of the measurements, such as temperatures, CO2 are taken from inside the growing zone. With temperatures, especially the extremes, there is generally a great difference between what is measured 1.2m above the surface and what it actually is right in the growing zone. This in understood by the scientists who work in agriculture, but I don't see anywhere where climate scientists use this different set of data.
    0 0
    Moderator Response: For some scientific studies of the effects of CO2 and heat, see the summary by the U.S. Dept. of Agriculture, and other studies, linked in the comments of the thread "CO2 is not a pollutant."
33. muoncounter at 14:28 PM on 8 March, 2011
    adrian s, "adding c02 to greenhouse air is standard practice" Ironic: Greenhouse gases are good for plants in greenhouses. But we're not necessarily talking about plants in greenhouses here. Here's one of those peer-reviewed thingies everybody talks about. Long et al 2008: Free-air concentration enrichment (FACE) technology has now facilitated large-scale trials of the major grain crops at elevated [CO2] under fully open-air field conditions. In those trials, elevated [CO2] enhanced yield by ~50% less than in enclosure studies. This casts serious doubt on projections that rising [CO2] will fully offset losses due to climate change. Apparently there's a big difference between conditions inside the greenhouse and the outside world.
    0 0
34. johnd at 15:11 PM on 8 March, 2011
    adrian smits at 14:18 PM, I agree also. Within agriculture, as with most fields, there is a huge pool of knowledge that has been accumulated along the way. Much of it is considered self evident amongst those who carry it. In many cases, techniques are developed without any formal scientific input, the scientists often left to produce a paper trail long after the practice had become standard procedure.
    0 0
35. johnd at 15:40 PM on 8 March, 2011
    muoncounter at 14:28 PM, you are putting the wrong emphasis on the results. The lower yield claim is comparing the FACE trials to those expected by modeling which was based on enclosure trials. It is basically supporting this which I had posted earlier- "Numerous free air carbon enrichment field trials are providing some such data, IIRC, the existing models generally failing to reliably forecast the increased yields many such trials produce." The FACE trials all showed positive responses to the CO2 enrichment for all 3 parameters across all 3 grains. The failure is with the modeling assumptions. Those who actually read the paper will see as much indicated near the end. One of the objectives of the FACE trials was to provide real data that would allow the models to be calibrated rather than just using assumptions. I don't think you'll find the big difference between the greenhouse and the real world, that is fairly well understood by those in the industry. As you have shown, the big difference is between the assumptions being made in the modeler's office and the real world.
    0 0
36. muoncounter at 15:42 PM on 8 March, 2011
    From Ainsworth 2008 reports on findings with the all-important rice crop (which is not grown in greenhouse gas-enriched closed environments): The rise in atmospheric [CO2] will be accompanied by increases in tropospheric O3 and temperature. When compared with rice grown in charcoal-filtered air, rice exposed to 62 ppb O3 showed a 14% decrease in yield. Many determinants of yield, including photosynthesis, biomass, leaf area index, grain number and grain mass, were reduced by elevated [O3]. While there have been too few studies of the interaction of CO2 and O3 for meta-analysis, the interaction of temperature and CO2 has been studied more widely. Elevated temperature treatments negated any enhancement in rice yield at elevated CO2 ...
    0 0
37. muoncounter at 15:53 PM on 8 March, 2011
    johnd, Here's how Long describes the source of what you're dismissing as 'models': ... most information about crop responses to elevated CO2 is obtained from studies in greenhouses, laboratory controlled-environment chambers, and transparent field chambers, where released CO2 may be retained and easily controlled. He then compares these artificial hot-house conditions (which are actual results, not models) to long-term real-world outdoor trials. Which result do you think will better match farm experience - for people who don't grow their crops under glass?
    0 0
38. johnd at 20:32 PM on 8 March, 2011
    muoncounter at 15:53 PM, the objective of the study you introduced, can first be deduced from this second sentence in Longs introduction,- "The CO2 fertilization factors used in models to project future yields were derived from enclosure studies conducted approximately 20 years ago." note the word models. This is then elaborated on in the paragraph headed- "How have CO2 fertilization factors been derived?" Which begins with "Most models used to predict future crop yields, including those within the IPCC (5), are from two families: ............" The final paragraph notes- "The FACE experiments clearly show that much lower CO2 fertilization factors should be used in model projections of future yields;....." It seems patently clear to me that the "food for thought" is really all about the adequacy or otherwise of the models being used as benchmarks.
    0 0
39. Paul D at 21:04 PM on 8 March, 2011
    adrian smits: "As a farmer I know that you need heat units to grow crops and the corn belt in north America has been moving north for years.We consider this a blessing that allows us to grow crops with higher yield and it gives us a greater choice as to what we can grow." God bless America and screw everyone else! What sort of choices are there in deserts? As I said, humanity needs biodiversity, just as much as corn and wheat.
    0 0
40. Paul D at 21:08 PM on 8 March, 2011
    Camburn: "Each study I have read concerning co2 and plants results in a higher level of co2 being benifical for plant growth." Then your reading is biased. Read wider. Do trees grow to infinity by continually adding CO2? http://www.uoguelph.ca/news/2010/10/forests_arent_t.html "Studying archived tree-ring measurements held by the National Oceanic and Atmospheric Administration in the United States, they found CO2 fertilization spurred faster tree growth at only about 20 per cent of sites worldwide, despite the fact that the gas typically accelerates growth in plants."
    0 0
41. johnd at 21:29 PM on 8 March, 2011
    The Ville at 21:08 PM, the claimed low rate of correlation of growth versus CO2 is very much reminiscent of trying to find trees whose tree-ring measurements reflected temperature driven growth. What percentage of trees in what percentage of sites worldwide have been able to provide suitable trees? Would it be that the same problem affects those trees as that which Briffa found with his trees and his divergence problem.
    0 0
42. Arkadiusz Semczyszak at 22:34 PM on 8 March, 2011
    This comment is ... But first, arguments - later opinion. Once again, the drought in Eastern and Central Europe is linked to the sharp change in ENSO from LN to LN - rapid drop (June - July) in temperature of the oceans (typical for the past two decades). This phenomenon causes changes in atmospheric circulation - effects ? - such as droughts in China. Just as in 2003 and 2006 - violent La Nina (need not be a big change - as the 2007 / 8, but it must be quick - rapid change) = drought in many areas of NH. Warming = warm winters. 1. I am eng. agro-meteorologist. 2. Generally, both the higher concentration of CO2 and temperatures favor most crops. It is textbook knowledge. Any cause of climate change in some areas of decline in the growth of other cereal production. The most visible example of this in Africa. “Projected impacts relative to current production levels range from −100% to +168% in econometric, from −84% to +62% in process-based, and from −57% to +30% in statistical assessments.” (Climate change risks for African agriculture, Müller et al., 2011.) Model Mann & Babb is too simple, would be real ...
    0 0
43. Arkadiusz Semczyszak at 22:36 PM on 8 March, 2011
    Sorry, The beginning of my post should be something like the following: @Chris G “... increased warmth in Russia lead to higher yields last year.” This comment is ...
    0 0
44. muoncounter at 02:02 AM on 9 March, 2011
    johnd "were derived from enclosure studies conducted approximately 20 years ago." Note the word 'studies.' "the "food for thought" is really all about the adequacy or otherwise of the models being used as benchmarks." You are picking out the word 'models' and objecting to it without noting that there are data from long-term studies behind those models. I'm neither a farmer nor a botanist (and the squirrels got most of last summer's tomatoes), but I quickly found 2 papers (refs above) casting doubt on the accuracy of greenhouse-based yield projections against actual performance in the open fields. The Ville came up with another. Thus it cannot be conclusively said that increased CO2 is a good thing; perhaps the simplest statement on the question of CO2 means higher plant yield is: 'the science isn't settled.'
    0 0
45. Paul D at 19:09 PM on 9 March, 2011
    johnd: "What percentage of trees in what percentage of sites worldwide have been able to provide suitable trees?" Please refer back to an earlier comment, where I suggested wider reading. It is a suggestion to broaden the reading material. The original commenter that I responded to suggested that all research pointed to only positive outcomes as a result of increased CO2. That is incorrect. Skeptics spend plenty of time saying the climate system is to complicated to understand. Yet instantly put forward statements that contradict that philosophy.
    0 0
46. Craig Cogger at 11:23 AM on 10 March, 2011
    The Penn State model is a useful educational tool for visualizing projected big picture impacts of climate change on agricultural production. Stockle et al. at Washington State University (USA) recently published the results of a similar modeling project focused on climate impacts on rainfed wheat, irrigated potatoes, and irrigated apples, three major crops eastern Washington, which has a cool semi-arid to sub-humid climate. They compared four climate models over using the IPCC A1B scenario (middle of the road CO2 emissions), linking them to a well-tested crop growth model. For each crop they ran 4 scenarios, 1) climate effect alone, 2) climate + adaptation (variety and planting date shifts), 3) climate and CO2 effect, and 4) climate + CO2 + adaptation. Modeled temperature increases by late century were around 3 C (compared with 1975-2005 baseline) and precipitation increases were projected. Only winter wheat showed yield increases from climate alone (at some locations), while spring wheat, apples and potatoes declined. Including CO2 effects and adaptation resulted in projected yield increases for apples and potatoes, but decline in quality could be an issue. In some ways this study approaches a best case scenario. The simulations assumed adequate nutrients (likely to be true) and sufficient irrigation water (more problematic given that snowpack is a major local irrigation source), and did not account for extreme weather events, or changes in weed, insect or disease pressure. The authors also noted uncertainty of the extent beneficial effects of CO2 as another caveat.
    0 0
47. Marcus at 13:01 PM on 10 March, 2011
    "•Cereal grains including rice, wheat, barley, oats and rye average between 25 and 64 percent higher yields under elevated CO2 levels." Well perhaps-*if* the plants in question are getting sufficient nitrogen, water & trace elements, & are not also being subjected to abnormally warm weather. Also, recent FACE trial results (from Horsham in Victoria) suggest that-even in ideal conditions-any such gains are short-term only, as the plants quickly become acclimatized to the higher CO2 levels.
    0 0
48. Marcus at 13:06 PM on 10 March, 2011
    "But there is a real place in the debate for those people, those with dirt under their fingernails, who are in the unique position to be able see whether the way the climate performs in theory is how it actually manifests itself on the ground." Yep, like the people I & my fellow employees talk to on a pretty regular basis-& you want to guess what their feeling is about Global Warming John? They're even more nervous about it than the scientists are-because they're seeing first hand the negative impacts that warming temperatures & more extreme hydrological cycles are having on their crop yields.
    0 0
49. johnd at 21:21 PM on 10 March, 2011
    Marcus at 13:06 PM, I have no doubt that you associate and talk to others who share similar views as yourself. Whether or not they are representative or not is another matter. Are you also sure they are not concerned more about short term weather events such as droughts? For representative views we should look perhaps to organisations such as the "National Farmers Federation", who represent all Australian farmers, in all fields, in all states. Five or six years ago they generally subscribed to the view that climate change was possibly the biggest risk facing Australian farmers over the coming century. This is easily found on the record. I'm not sure that they still hold that view. Recently I witnessed Jock Lawrie, the new President of the NFF, talk on climate related matters, and his general position was that they, the NFF, need to see more evidence before any major initiatives are undertaken relating to climate change. It is difficult to find any transcripts or recent statements on just what the NFF policy is at present to provide as a reference, the best I can do at the moment is the farewell address given by the outgoing President, David Crombie just four months ago. What is conspicuous by it's absence is any reference at all to climate change being the biggest risk of the coming century, or even a risk at all. In fact the only reference to climate at all talks about "adapting to our variable climate". Our variable climate. Don't you think that is a bit perplexing? Even when he speaks of the significant challenges and change that he had to face during his term, climate change does not rate a mention. Nor does it rate a mention when he speaks of future issues that will have to be faced. So what do you think is the current NFF feeling about AGW, they being the official representative of Australian farmers? David Crombie's Farewell Address
    0 0
50. Albatross at 03:41 AM on 11 March, 2011
    Folks, how about we defer to the experts on this? Here is what Dr. Peter Reich had to say in response to Monckton's misinformation (similar to what is being perpetuated by "skeptics" on this thread) on this issue (from here): "The best evidence from state-of-the-art free-air carbon dioxide enrichment experiments is inconsistent with the notion of major sustained increases in crop yield in a world of doubled atmospheric CO2. Quantitative analyses and syntheses of those experiments indicate that the direct effects of elevated CO2 will increase crop yields by 13% (on average for those with the C3 photosynthetic pathway, such as wheat, soybeans, rice) or 0% (on average for those with the C4 photosynthetic pathway, such as corn, sugar cane, and sorghum); not the 40% Lord Monc[k]ton suggests. Moreover, these estimates ignore (1) indirect effects of CO2 as a greenhouse gas on future temperatures, precipitation, and their variability, and hence on future crop yields and (2) other consequences of fossil fuel burning such as rising ozone pollution that will reduce crop yields. The bottom line for crop yields: combined effects of fossil-fuel burning (rising CO2, rising O3, climate change) are uncertain but at least as likely to be negative as positive, and shifting increasingly towards the negative the higher that CO2 concentrations rise." Dr. Peter Reich: Regents Professor and Distinguished McKnight University Professor, University of Minnesota’s Department of Forest Resources. His teaching and research focus on ecology, global change, and the sustainability of managed and unmanaged terrestrial ecosystems. Regionally, his interests lie in the forests and grasslands of mid-North America and globally on terrestrial ecosystems in aggregate. I'm going with the science and Dr. Reich on this one.
    0 0

1  2  Next

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.