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Comments 51 to 87 out of 87:

51. Albatross at 04:23 AM on 11 March, 2011
    And for those who claim that plants do better in CO2 "enriched" environments under water stressed conditions, the observations (from a global network of flux towers) show otherwise. From Jung et al. (2010, Nature): "Hence, increasing soil-moisture limitations on evapotranspiration largely explain the recent decline of the global land-evapotranspiration trend. Whether the changing behaviour of evapotranspiration is representative of natural climate variability or reflects a more permanent reorganization of the land water cycle is a key question for earth system science." More here. This research is corroborated by independent research (using satellite data) conducted by Zhao and Running (2010, Science) who found that: "The past decade (2000 to 2009) has been the warmest since instrumental measurements began, which could imply continued increases in NPP; however, our estimates suggest a reduction in the global NPP of 0.55 petagrams of carbon. Large-scale droughts have reduced regional NPP, and a drying trend in the Southern Hemisphere has decreased NPP in that area, counteracting the increased NPP over the Northern Hemisphere. A continued decline in NPP would not only weaken the terrestrial carbon sink, but it would also intensify future competition between food demand and proposed biofuel production." NPP= Net Primary Production, a measure of "the amount of atmospheric carbon fixed by plants and accumulated as biomass". That is, photosynthetic activity.
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52. Marcus at 09:11 AM on 11 March, 2011
    John D "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?" First of all, my work doesn't allow me to *choose* who I associate or talk to-any more than it does my colleagues-yet still the majority of the farmers we come in contact with express a deep level of concern about global warming-not short term weather effects, as you suggest, but explicit mention of global warming (though they do mention its impacts on things like droughts, which most of them have noticed getting worse over the last 30 years). Second of all, do you *honestly* think that an organization like the NFF genuinely represents the view of the majority of ordinary farmers? That's like saying the ACTU represents the view of the majority of blue-collar workers. Indeed, the view I get from the farmers themselves is that the NFF really only represents the views of the so-called "agri-businesses", or "factory farms", not the views of multi-generational family farms.
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53. johnd at 11:08 AM on 11 March, 2011
    Marcus at 09:11 AM, who the NFF represents comes both directly, and indirectly through the various state bodies, and in turn the various industry bodies that do closely represent individual farmers. It would be interesting to find out if ordinary farmers consider that the Federal Government or the IPCC more closely represents their views. With regards to your mention of multi-generational family farms, because of the post WW2 soldier settlement scheme, in many areas of Australia, multi-generational means that a large number of family farms are only second generation. When they compare the conditions the present generation are facing, with that their parents faced, then obviously they are confined to a 50 -60 year period, but more importantly a period that their parents enjoyed that was not the normal when compared to what is known about Australia's longer term variable climate. It is interesting that some of those present day farmers whose family holdings extends beyond two generations, are finding that some of the conditions they have experienced were similar instead to what confronted their grandparents. With regards to the 30 year period you mentioned, which is generally taken to be the length of time that will represent a climate cycle rather than weather cycles. I think it is about time that this is re-evaluated as to whether it is still appropriate or not. When it was adopted about 100 years ago, the knowledge of weather and climate, both of then and past, was somewhat limited compared to today, as was the ability to measure and quantify all the relevant parameters. Like the concept of a flat earth, it came about reflecting the level of scientific understanding of the day. Obviously our understanding of both has progressed somewhat since those early days, and perhaps we should look to adopting a more appropriate time frame to define climate.
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54. Camburn at 13:53 PM on 11 March, 2011
    Albatross: I would caution you to use a grain of salt on relying on articles by Dr. Reich. I will stand with real world research from fields showing that additional co2 results in higher bio mass and crop yields. Also, Dr. Reich is wrong on higher co2 effects on corn. The root structure of co2 enhanced corn in unbelievable compared to normal levels of co2. I can only suggest that if you are going to comment on articles such as this that you do a lot more reading and stay abreast of the current research being done. The resutls that you are alluding to are not the results of real world experiments.
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55. Marcus at 13:54 PM on 11 March, 2011
    "It is interesting that some of those present day farmers whose family holdings extends beyond two generations, are finding that some of the conditions they have experienced were similar instead to what confronted their grandparents." You want to back that up with some *evidence* John? Man, your ability to keep repeating the same falsehoods as though they're indisputable facts is getting somewhat tiresome. Your claims of some magic 30-year cycle is simply not backed up by the wealth of scientific data, nor is your claim that the NFF genuinely reflects the opinions of ordinary farmers backed up by the evidence I've seen & heard with my own senses. So unless you want to start backing up your claims with something approaching *real* evidence, then I simply don't see any point in arguing the case with you. According to PIRSA, btw, the science behind AGW is supported by both the SA Farmers Federation & the National Farmers Federation-so seems like your earlier claim isn't backed by the facts either.
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56. Marcus at 14:02 PM on 11 March, 2011
    What you keep forgetting Camburn, is several key things: (1) warmer weather increases the rate of senescence (aging) in plants, meaning that seed ripening tends to occur *before* they have a chance to reach maximum size. (2) most plants tend to be biased towards increasing vegetative biomass over seed biomass. (3) plants exposed to higher CO2, prior to acclimation, require much more nitrogen as they need to produce more of the enzymes needed to utilize the extra CO2 in their bio-synthetic pathways. (4) these plants also require greater energy to build & maintain the enzymes necessary to utilize the extra CO2. (5) over time, these plants become acclimatized, & actually switch off the production of the extra enzyme, meaning biomass increases from extra CO2 usually only last about 2-3 years at most-shorter if the plants lack access to sufficient quantities of nitrogen, water & trace elements-the *real* rate-limiting factors in determining long-term plant growth. (6) several plant types (rice in particular) actually reduce their take up of certain trace elements (such as Zinc) when exposed to above normal levels of CO2.
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57. Marcus at 14:05 PM on 11 March, 2011
    "I will stand with real world research from fields showing that additional co2 results in higher bio mass and crop yields." ....and which field trials are you referring to? All the FACE trials I've read about suggest that the benefits of extra CO2 have been massively overstated, & usually come at significant cost (as I've highlighted above)-& are ultimately short lived anyway. Still, you go on clinging to that meme if it makes you feel better.
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58. johnd at 14:21 PM on 11 March, 2011
    Marcus at 13:54 PM, these rainfall trend maps illustrate how conditions, for the present generation of farmers, in this example rainfall, are closer to that experienced by their grandparents, and quite different to that experienced by their parents. As for the present day policy of the NFF, please provide some evidence.
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59. Camburn at 14:51 PM on 11 March, 2011
    Marcus: I will continue to cling to that meme. Also, as far as acclimateing to higher co2, ahhhh.......forget it. ( -snip- )
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    Moderator Response: [DB] Please refrain from being insulting to others if you want your comments to not be deleted. Posting on this site is a privilege, not a right.
60. Tom Curtis at 14:53 PM on 11 March, 2011
    johnd @ 58, I cannot help but notice that half the difference in trends between those two maps is just a consequence of the different time periods. If the trend over 80 years is -10.00 per decade, and over 40 years it is -20.00 per decade, then the starting rainfalls are effectively identical, and the greatest similarity is between 1930 and 1970, rather than between either and 2010. Looking at the time series shows that the 1970's was an extrordinarilly wet decade, and that the period since the 1970s is unusual compared to that before the 1970s. Of course, that hides large regional differences. Comparing trends originating with the 1950s and 1910s shows a much smaller difference than does your choice of comparators, with a large portion of the difference arising solely from the longer period since 1910. Your claim that current conditions are more like those of our grand parents than those of our parents appears to be on very shaky ground.
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61. Camburn at 14:54 PM on 11 March, 2011
    johnd: Go back further in time for your continent. The climate extremes are extreme, and ever changing. North America also has extremes in paloe climate. A little longer timescale than Australia tho it seems.
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62. Tom Curtis at 14:59 PM on 11 March, 2011

    Climate change threat must be tackled ‘head on’ 5 February 2007 “THE threat of global climate change is potentially the biggest issue Australian agriculture has ever faced with reports of increasing seasonal variability and more extreme weather events,” National Farmers’ Federation (NFF) President David Crombie declared today in the wake of the Intergovernmental Panel on Climate Change (IPCC) Report, released over the weekend. “The Australian farming sector is utterly dependent on weather conditions and any prolonged change in climatic patterns has the potential to plunge farmers, and the majority of Australia, into the realm of the unknown. Rather than throw our hands up in despair, the NFF is advocating direct and deliberate national engagement on the issue to dispel the myths, measure the realities and identify solutions. “What is already apparent is the need to better position agriculture to manage resources in the context of a changing climate. On this, we cannot, and must not, wait. A vastly increased research effort is needed – sooner, rather than later – to enable all primary industries to plan, adapt and respond to greenhouse and climate change challenges… those of today and those predicted.

    From the National Farmer's Federations
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63. Albatross at 15:27 PM on 11 March, 2011
    Tom @62, You continue to impress :) The maps that johnd showed are really quite meaningless for the point he is trying to make, although his point is not that clear either.
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64. johnd at 15:53 PM on 11 March, 2011
    Tom Curtis at 14:59 PM, as you apparently have not been following this discussion, go back and read my post-johnd at 21:21 PM and subsequent ones. Most recently, the deliberate usage of the phrase "variable climate" by the outgoing President, and the general thrust of the new President in wanting to see more evidence is a definite shift from their earlier stated position of climate change being the greatest challenge facing farmers over the next century. Perhaps they might revert if sufficient evidence is forthcoming, but apparently what there is so far is not considered clear cut enough. My impression from listening to Jock Laurie is that they should stop and look carefully at all the evidence before rushing in and implementing any new measures as the government is want to do in various ways. It is not unknown for people or organisations to reconsider earlier positions as knowledge and events evolve.
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65. Albatross at 15:54 PM on 11 March, 2011
    Camburn, In contrast to my previous statement to Tom Curtis, you (like your fellow "skeptics") do not impress. Why? Tom presents facts, links and data...you on the other hand present unsubstantiated opinions. Even though plant physiology is not my field of expertise, my latest research has required that I read quite a bit about it, and the two papers that I cited @51 were from 2010, and were based on real-world data (surface-based and satellite based). Now, if you are willing to make the effort to provide some credible peer-reviewed literature to back up your assertions we can go from there. And Marcus @56 makes some very valid points which you apparently choose to ignore.
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66. johnd at 15:55 PM on 11 March, 2011
    Tom Curtis at 14:53 PM, again go back and read the exchange between Marcus and myself. Clearly the trend maps are totally relevant for the point being made.
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67. johnd at 16:31 PM on 11 March, 2011
    Camburn at 14:54 PM, most people with any understanding of the Australian climate will agree with you entirely. Whilst official records only go back to the late 1800's making it difficult to appreciate longer term variations, there has been a wealth of unofficial records and anecdotal accounts they go back to first settlement. A project has been underway for the last couple of years that is compiling all such relevant information from journals, newspapers etc that will be used to reconstruct the conditions between first settlement, and even further back, and the beginning of official records. It is called the SEARCH project and all information is being fed into the OzDocs volunteer database. Most kids did early Australian history at school and should generally be well aware of the conditions that prevailed in those early days through what was taught of the early explorers and pioneers who opened up the country. This SEARCH project will help legitimise such anecdotal evidence and has already revealed much that had previously lay hidden, only known through stories.
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68. JMurphy at 20:04 PM on 11 March, 2011
    johnd wrote : "With regards to the 30 year period you mentioned, which is generally taken to be the length of time that will represent a climate cycle rather than weather cycles. I think it is about time that this is re-evaluated as to whether it is still appropriate or not. When it was adopted about 100 years ago, the knowledge of weather and climate, both of then and past, was somewhat limited compared to today, as was the ability to measure and quantify all the relevant parameters." Ah, do we have the next tactic from the so-called skeptics ? Previously, with regard to temperature, the claim was that the satellite readings were better than those on the ground....until the satellites became inconvenient - now, satellite readings are suspect too. So, because those in denial can't rationally argue against the Weather/Climate difference, they now have to try to undermine the 30 year definition of climate. Why ? Because they need longer time-periods to try to argue their 'What if/Maybe' beliefs - time periods measured in hundreds, thousands, even millions of years if necessary. And the 30 years concept was adopted in 1935. To anyone who deals in generalities, that is indeed "about 100 years ago".
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69. Marcus at 22:06 PM on 11 March, 2011
    "It is easy to see that you don't understand agriculture as it is presently practiced." That's quite a hilarious accusation, Camburn, given that I've been working as an Agricultural Scientists for around the last 11 years-dealing with everything from molecular biology & physiology, right up to & including full-scale field trials (which is where I've met with *real* farmers-across Southern & Eastern Australia). So in spite of your snarky claims, I'm guessing I probably understand present-& future-agriculture a lot better than you do. As to acclimation, it has a very basic, physiological basis-namely that the plant won't continue to expend the extra energy needed to fix the additional carbon dioxide unless there is some long-term benefit to the plant-which is especially the case when plants are grown in soils relatively low in moisture, nitrogen, phosphorous or trace elements. This acclimation is exactly what is being seen in long-term FACE trials across the world. Here's another thing to consider, though-at higher temperature, the amount of CO2 dissolved in the moisture of the leaf tissue is decreased, meaning less CO2 to enter the Calvin Cycle & be fixed as carbohydrate. So CO2 induced warming-all by itself-can actually undermine even the short-term benefits of higher CO2, by making less CO2 available to the plant in the first place. So, when coupled with the climate change impacts on water & senescence, this represents yet another nail in the coffin of the "CO2 is plant food meme".
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    Moderator Response: How about asking John Cook if you could put some of those great details into either the It's Not Bad or CO2 is Not a Pollutant arguments?
70. Marcus at 22:09 PM on 11 March, 2011
    Oh, & lets not forget the impacts of CO2 & related climate change on soil-borne pathogens, insect pathogens & weeds-all of which can significantly offset any marginal benefits of CO2-induced biomass increases.
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71. johnd at 23:44 PM on 11 March, 2011
    Marcus at 22:06 PM, all very interesting. As someone who demands of others that they provide something tangible to support their assertions, perhaps you can do the same. Have you had anything published, the results of those field trials for example, that illustrate the work you have been involved in? Generally the results of such work, even small trials end up published in one form or another to allow the information to be disseminated to interested parties such as those in the industry, either in trade journals, newspapers or newsletters. As you should know much information transfers informally with the only "peer review process" being the number of people who adopt the practice and recommend it to others. The use of CO2 fertilisation in the tomato and other hot house enterprises being a prime example. Even now, decades later, there are experts doubting the effectiveness of the practice. IIRC you are one such person, am I right? Given that your meetings with real farmers has apparently only come about through your work, that more or less confirms the impression left that you are not from an agricultural background. If you had been then it would also not have been necessary for me to illustrate just how different the conditions have been between the present generation of farmers and their grandparents. It's things like this that are taken for granted as being understood by anyone involved in agriculture at a practical level.
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72. johnd at 00:23 AM on 12 March, 2011
    JMurphy at 20:04 PM, I was hoping for some genuine comments on whether 30 years was still relevant or not, not a paranoid search for hidden agendas. As for the remark about, "about 100 years", rather than being a generalities, "about 100 years" rather precisely dates the time frame in which "after much international discussion in the late 19th and early 20th centuries, 30 years was settled on as a suitable averaging period."
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73. RickG at 00:46 AM on 12 March, 2011
    johnd: "I was hoping for some genuine comments on whether 30 years was still relevant or not...... I think the important thing to understand about the 30 year period is that it is a minimum period of time needed in order to establish a recognizable trend which filters out the noise, especially those of oscillations which are known not to be drivers of overall trends.
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74. JMurphy at 01:40 AM on 12 March, 2011
    True enough, RickG, but the so-called skeptics would like to extend that to hundreds, thousands, etc. so that they can then say that we won't know, until that amount of time is over, whether AGW is happening or not. However, from the WMO link I gave previously, they do state that less than 30 years can be used to determine certain trends, but that is even worse news for the so-called skeptics : first, because it means we know now how AGW is affecting the globe, and secondly, because they will get very confused from year to year to decade - proclaiming global cooling one year/decade; 'flattening' temperatures the next year/decade; uncertaintly the next year/decade, etc. as they try to use whatever time-period they can to try to make different claims depending on what they think they can get away with. Oh, they already do that... Anyway, perhaps we should leave it to the particular experts in that particular field (i.e. those at the 'coal-face', so to speak, who know what they are talking about) to determine what they consider the best time period to use. It won't please the minority in other fields, who like to claim some sort of right or self-proclaimed expertise but who are on the outside looking in, but such is life.
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75. KR at 01:49 AM on 12 March, 2011
    johnd - The 30 year period was chosen based on the data; a period long enough to cover several cycles of variations such the ENSO, in order to filter out observed variability and look for long term trends. Since the inherent variability time-scale of the climate appears not to have changed much in the last century (although there is some evidence that the amplitude of weather extremes may be increasing, variation times have not), 30 years is still an entirely reasonable trend averaging. It's just simple statistics. What justification do you have for proposing changing that averaging length? I don't see that it could be shortened (after all, you want to average a couple of ENSO events to see trends outside the variation) - do you have any evidence showing that it should be longer?
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76. johnd at 07:18 AM on 12 March, 2011
    KR at 01:49 AM, it was with such as the ENSO in mind that has long had me considering this question. Our understanding of weather and climate has undoubtedly expanded somewhat since this "standard" was adopted, tracking our ability to measure all the parameters. Identifying ENSO, let alone understanding it was still yet to come, so ENSO could not have been in their minds at the time of the adoption. The various indexes that track the phases of the atmosphere/ocean systems are all recent advances, the IOD only about a decade ago. They all have become most relevant to our understanding, yet we still are yet to understand how they interact fully. Identifying the IOD was of particular relevance to Australia allowing some order to be bought to the cycles of drought and flooding rains. Therefore confining ourselves to averaging over a couple of ENSO events is akin to averaging the weather over a couple of day night cycles as opposed to averaging it over a couple of annual cycles. My thoughts are that whatever period is used should as a minimum cover a couple of complete cycles of those oscillations that have so far been identified and thus able to be measured, because ultimately it is not about simply measuring temperature fluctuations, but about accurately tracking heat in and out of the oceans which is where the length and frequency of such cycles becomes most relevant. Some paranoia seems to exist about making any changes, as it always has done so. In this case it seems the fear is that by extending such periods the graphs will have to extend from paper edge to paper edge which could lead to one falling off the edge of the paper whilst trying to explore the extremities. sigh-- some things never change.
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77. johnd at 07:32 AM on 12 March, 2011
    JMurphy at 01:40 AM, given your anxiety about this matter and subsequent urging that "perhaps we should leave it to the particular experts in that particular field", let me assure you that it is unlikely that such changes will be implemented in this thread, at least not today, and certainly not without your consent. Perhaps the moderators can suggest a more suitable thread where it can be implemented.
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78. KR at 07:41 AM on 12 March, 2011
    johnd - You're quite correct, our understanding of things like the ENSO have improved tremendously over the last century. That means we can now account for them in normalizing temperature records, as Tamino has done. And that therefore there is justification for using shorter time periods to detect trends with such variations removed. Not justification for longer periods. The Indian Ocean Dipole (IOD, which you had not clarified) cycles about four times every thirty years, similar in period to the ENSO. And hence the 30 year averaging should encompass the IOD as well. The initial 30 year average came out of looking at long term temperature records, variation and noise, and numerically looking at how long a period was required to detect a statistically significant trend against that variation. The statistics haven't changed - 30 years is still the right time period, although if we back the ENSO and other detectable variances out we have a chance to identify trends with shorter periods. Unless you have identified a 15-40 year or greater cycle that isn't being accounted for? You might then want to look at Tamino's recent post on identifying unknown cycles and relationships. I'm still not hearing a justification for a longer time period for climate estimation - but rather a shorter one if properly calculated.
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79. johnd at 08:19 AM on 12 March, 2011
    KR at 07:41 AM, you are looking at it more from a weather perspective by ignoring how ocean heat content becomes a function of these longer term cycles. With regards to the IOD, you've also overlooked the most recent history where it remained in a positive or neutral phase from 1992 until it's present negative phase, which was the longest period of it's kind since records began in the late 1800's. However, from an Australian perspective, and by extension all other regions on the ocean's rim, it's the fact that it oscillates differently to adjoining systems. This current situation of a -ve IOD coinciding with a La-Nina last occurred in 1975 bring a similar extended wet period to Australia and no doubt having a similar effect on the ocean heat flux. Other years where they have also coincided could include 1942, 1933, 1917, 1916, 1909 and 1906, however that depends on how different agencies classify the occurrence. Apart from the most recent coincidence, 1975 is the only other year that is common to all.
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80. KR at 09:26 AM on 12 March, 2011
    johnd - I spent some time looking into the IOD; it's not something I was familiar with. You're quite right, the IOD has been mostly positive for years now, and may be exiting the "quasi-periodic oscillation" category for a more persistent pattern. But quite frankly, the IOD is regional weather, not global climate. Wind patterns move warm water to the west, with resulting colder upwelling near Sumatra. The overall effect is a redistribution of warmth, but not a global trend - an increase or decrease in energy retained. The shift to a more persistent pattern appears to be an example of regional climate change, like the northern movement of the equatorial rain belt, which will probably begin to raise coffee prices in coming years as Central American (among others) precipitation shifts and the southern US dries out. The IOD appears to be more persistent due to climate driven wind changes. The IOD is a huge influence on Australian weather - but does it affect long term global temperature averages??? Perhaps it will result in a 'step change' if it stops varying, although I can only see that if the long term shift changes absorption of solar energy, rather than redistribution. But if it stops varying due to long term wind shifts, it's certainly will affect temperature variance even less than it does now. The 30 year running average may have a change like the one around 1945 or 1975. But the time required to extract a statistically significant trend from varying data will actually reduce if the IOD ceases to vary.
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81. johnd at 10:23 AM on 12 March, 2011
    KR at 09:26 AM, collectively, regional weather is our both our means of being able to quantify global climate, and being able understand how it manifests itself at any point in time, past, present or future. Ocean heat content is central to global climate and thus anything that plays into that by altering the conditions that drive the heat flux at the surface is most relevant. Systems such as the IOD have both a "front" and a "back" and given the physical world is neither uniform nor symmetrical across it's surfaces, the frequency of the oscillations and the time spent in each phase does not necessarily mean that everything balances out once a complete cycle has occurred. As you noted the IOD is very relevant to Australia, and it is only since being identified that it has become realised that some of what had previously been attributed to ENSO was in fact due to the IOD. I believe that some studies have, or are being carried out, taking the IOD into account may mean the influence of ENSO is not as great as presently thought. Even without such studies we now know that to be the case for Australia, especially where droughts are concerned, and perhaps floods as well. Time will tell.
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82. Marcus at 12:20 PM on 12 March, 2011
    John D, if you *honestly* think that I'm going to risk exposing myself to abuse & intimidation by your "skeptic" friends, by revealing more about myself than I already have, then you're sadly mistaken-especially as you still remain unwilling to do so yourself.. The only reason I said as much as I did was to disabuse Camburn of any illusions that I don't have working knowledge of current day agricultural practices (heck, my Mum & Step-Dad own a farm, for Pete's sake). Still, the fact that you've chosen to cast aspersions on my credentials reveals how weak the arguments you & Camburn have presented *really* are. Though its not my actual field of expertise, I have taken the time to read up on the literature regarding enhanced CO2 levels on crop plants, & they simply do *not* paint the incredibly rosy picture that you & Camburn try to do-even when the studies ignore all the other negative impacts that will be associated with CO2 induced climate change. I also have to love how you place so much *faith* in untested hypotheses, when you think they might support your AGW skepticism, yet you still show an unwillingness to accept more than 100 years of accepted science regarding the impacts of increased CO2 in our atmosphere. I guess your "skepticism" is very selective.
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83. KR at 12:30 PM on 12 March, 2011
    johnd - I agree that local and regional weather and longer term climate will be vital to the impact and response of climate change on everyone. But you have not, as we were discussing, made the case that the 30 year averaging of variability to identify statistically significant trends is invalid.
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84. Camburn at 02:59 AM on 13 March, 2011
    Back to co2. This research confirms that soybeans respond very positively to higher levels of co2. http://farmtalknewspaper.com/crops/x1327129664/Research-looks-at-crop-response-to-CO2
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85. Camburn at 03:17 AM on 13 March, 2011
    I don't know what in the world I am doing wrong, but I can't seem to get the fancy direct link working. Anyways, here is another link concerning soybeans and elevated levels of co2: http://www.eurekalert.org/pub_releases/2009-02/uoia-hcb020609.php
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86. johnd at 04:34 AM on 13 March, 2011
    KR at 12:30 PM, we know from research that the climate in various regions has regularly alternated between wet phases and dry phases, with the corresponding effects on temperature, for periods up to double the 30 year standard. Please demonstrate how the 30 year standard would provide usable data in such circumstances. The projections made whilst in the midst of such periods are going to yield different results. This can be a problem for forecasts produced by statistically modeling. Most of this identification of such longer term cycles has only come about through recent research, thus is unlikely to have been taken into account when discussions on this subject were taking place a century ago.
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87. KR at 05:22 AM on 13 March, 2011
    johnd - You handle long term changes such as that the same way we handle the aerosols in the 1950s-1970s: you note the active factors and look at long term trends in light of them. Long term shifts do not introduce noise, they introduce long term slope changes. And the 30-year averaging is intended to average out noise, variability that we don't have a handle on due to chaotic factors and details of local interactions. I'll note that I have yet to see a 60-year cycle actually extractable from the data; many have tried, but it just doesn't hold up under numeric analysis as periodic events.
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