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What we can learn from studying the last millennium (or so)

Filed under: — mike @ 15 May 2010 - (Español)

With all of the emphasis that is often placed on hemispheric or global mean temperature trends during the past millennium, and the context they provide for interpreting modern warming trends, one thing is often lost in the discussion: space matters as much as time. Indeed, it is likely that the regional patterns of past climate changes, rather than simple hemispheric or global mean temperature trends, will best inform our understanding of the dynamical mechanisms involved. Since much of the uncertainty in future projections relates to regional climate change impacts, it makes particular sense to focus on those changes in the past that involve regional changes and the underlying mechanisms behind them.

For instance, melting of the cryosphere (and consequent rises in sea level), subtle shifts in drought and rainfall patterns, and extreme events, are all regional effects that could be important threats to ecosystems and our environment. Such changes are often associated with phenomena like ENSO or the North Atlantic Oscillation. Yet there remain large uncertainties about how such mechanisms will respond to anthropogenic climate change.

There are a number of potential ways forward to improve our understanding. A first step is to look directly at the time-series of specific systems (like the ENSO index or the ocean temperatures in the North Atlantic) and try to extend them as far back as possible using proxy data. This gives more information on what the natural variations in these phenomena look like, and thus a better idea of how big a forced response would need to be before it could be reliably detected. Secondly, we can look to see if there is a relationship between various natural drivers of climate change (volcanic eruptions, solar variability or orbital forcing say) and any characteristics of these phenomena – amplitude, frequency or duration. Do volcanic eruptions appear to affect El Niño for instance?

For phenomena that need annual or decadal resolution data to be resolved, the last millennium or so is an obvious (and only) time period to be looking at for it is only for that period that there is sufficient paleo-data coverage of high enough temporal resolution. Other periods – such as the mid-Holocene 6000 years ago – are also useful, but the results are more long-term in nature (there is also a discussion of the value of different periods for reducing future projection uncertainty in this recent paper).

There are a number of different approaches to looking at reconstructions in recent centuries – some rely on high density regional networks (as seen in this recent paper by Guiot et al concerning European temperature trends for which they mostly used pollen data) and some rely on wider networks of more diverse proxies which aim to capture longer-range correlations to specific phenomena (such as the recent Mann et al (2009) paper).

When this is done, people usually find that while it was relatively cool in global mean temperatures from the 1400s to the 1800s known as the “Little Ice Age” and relatively mild in the 900s to 1300s interval ( sometimes termed the “Medieval Warm Period”). But the spatial reconstructions reveal, however, why such global terms can be quite misleading, and why alternative phrases such as the “Medieval Climate Anomaly” are being increasingly favored by the community. This latter terminology recognizes that while the interval displayed significant climate anomalies, they varied greatly, even in sign, from region to region. Many of the more profound climate anomalies, moreover, involve variables other than temperature, such as drought, rainfall, and atmospheric circulation. Though the medieval period is seen to be modestly warmer globally in comparison with the later centuries of the Little Ice Age (the peak global mean warmth is likely comparable to mid, but not late, 20th century warmth), some key regions appear to have in fact been colder, while other regions appear to have been warmer. Southern Greenland, for example, appears within uncertainties to have been as warm as today. However, much of the tropical Pacific was unusually cold, suggestive of the La Niña phase of the ENSO phenomenon (a similar conclusion was reached by Trouet et al (2009)). Thus even though some locations may have been as warm or warmer than today, the hemispheric mean appears not to have been.

Why does this matter? It matters because there are plenty of factors that can affect the overall mean temperature (solar variability, volcanoes, greenhouse gases, internal variability etc.) and so it is hard, given the uncertainties in the solar or volcanic reconstructions to precisely attribute the paleo changes in the global or hemispheric mean to these factors. But if we can look at more complex fingerprints of the changes, it might be possible to be more quantitative in those attributions since the spatial fingerprints of the different factors are easier to distinguish. Furthermore, if we can clearly tie the regional patterns to the different forcings, we might be able to use that information to inform regional projections under future conditions.

Thus we can basically say that the warmer conditions of the Medieval era were tied to higher solar output and few volcanic eruptions and the cooler conditions of the Little Ice Age resulted from lower solar output and more frequent volcanic eruptions. But these drivers appear to have had an equally important, though more subtle, influence on regional temperature patterns through their impact on climate phenomena such as ENSO and the North Atlantic Oscillation. The modest increase in solar output during Medieval times appears to have favored the tendency for the positive phase of the NAO, associated with a more northerly jet stream over the North Atlantic. This brought relatively greater warmth in winter to the North Atlantic and Eurasia. A tendency toward the opposite negative NAO phase helps to explain the enhanced winter cooling over a large part of Eurasia during the later Little Ice Age period.

There is some model support for these patterns (see also instance Shindell et al, 2001) when the models include interactive ozone photochemistry to produce this dynamical response to solar forcing, but it is not captured in a simulation of the NCAR CSM coupled model which lacks those processes. Neither model simulation reproduces the apparent La Niña pattern seen in the Medieval temperature reconstructions:

Figure 1: Spatial pattern of mean temperature difference between the MCA and LIA periods (defined at the intervals AD 950-1250 CE and 1400-1700 CE respectively) compared with simulations of two different climate models forced with estimated differences in natural (volcanic and solar) radiative forcing between the two periods (Mann et al, 2009).

Other model simulations, however, using a climate model that exhibits a particular tropical Pacific mechanism, do reproduce such a response. In such models, the tropical Pacific counter-intuitively tends to the cold La Niña phase during periods of increased heating, such as provided by the increase in solar output and low volcanism of the Medieval era. If this response holds for the future, something that is still vigorously debated, it could imply a more La Niña-like response in the future. Most of the state-of-the-art climate models, e.g. those used in the IPCC Fourth Assessment, by contrast, suggest the opposite–a more El Niño-like future climate. The credibility of the models with regard to this phenomenon is not high, however, and lots more work is going to be needed (both on paleo-reconstructions and model improvements) before we can be confident in the future projections of changes in ENSO-like dynamics and mean state.

690 Responses to “What we can learn from studying the last millennium (or so)”

  1. 501
    Ray Ladbury says:

    Septic Matthew, the theory is of Earth’s climate. Anthropogenic causation of warming is a prediction of that theory–a confirmed prediction. In order to make this prediction go away from the theory, you would have to come up with a theory that explains ALL OF EARTH’S CLIMATE as well as the current theory without a significant sensitivity to CO2. If you do that, I’ll start to have doubts about anthropogenic causation.

  2. 502
    Completely Fed Up says:

    Kevin: “CFU: …Specifically, every drought event must logically be worsened.”

    Where did I say that?

    I didn’t.

    Why are you attributing that to me and then argue against it being true?

    Specifically, every drought event *** absent any causation that undoes the warming and drying effect *** must logically be worsened.

    I’ve given examples of what you could do to show that in one event that AGW had an effect of easing the drought.

    Why then are people attributing an absolute to me I have given examples that refute its absolutism????

  3. 503
    John Mashey says:

    re: #471
    It isn’t a question of “natural vs anthropogenic”, it’s a question of “how much” of each, i.e., it’s an attribution problem (and I see Gavin just started a new thread on that.) There is zero “excluded middle” issue.

    As for references, one of the later ones on (several) of Ruiddiman’s various hypotheses is:
    The early anthropogenic hypothesis: Challenges and responses, Reviews of Geophysics, October 2007.
    Section 10 is “Did pandemics contribute to drops in atmospheric CO2?”, but other sections a lot of relevant discussion on forestration issues vs acreage used.
    However, this is a little old, as much has happpened since.
    There have been a bunch of papers (in various combinations) by RJ Nevle, DK Bird, RA Dull and others, such as:
    Effects of syn-pandemic fire reduction and reforestation in the tropical Americas on atmospheric CO2 during European conquest, Palaeogeography, Palaeoclimatology, Palaeoecology
    Volume 264, Issues 1-2, 7 July 2008, Pages 25-38.

    I think I mentioned this one:
    Kauffman, J.B., Hughes, R.F. and Heider, C. 2009: Carbon pool and biomass dynamics associated with deforestation, land use, and agricultural abandonment in the neotropics. Ecological Applications 19, 1211-1222.

    Frank, D.C., Esper, J., Raible, C.C., Buntgen, U., Trouet, V., Stocker, B. and Joos, F. 2010: Ensemble reconstruction constraints on the global carbon cycle sensitivity to climate. Nature 463, 527-530. [that’;s for context, but the quote, p.529, is interesting:
    “Although occurring around the coldest period
    of the past millennium (Fig. 2a), the LIA CO2 decline is unique in the context of the past two millennia, both in magnitude and in its rate of change.”

    But in any case, keep an eye out for that forthcoming issue of The Holocene.

    The way I’d summarize all this is that archaeologists & geographers have been beavering away for years, and finding there were a lot more people in the pre-Columbian Americas than thought (several) decades ago, and that they farmed a lot more land than was thought. There is of course, a lot of anthropological literature on climate vs civilizations (of popular books, Brian Fagan’s come to mind).

    Ruddiman generated several hypotheses of possible anthropogenic influences on climate (early CO2, early CH4, inhibition of reglaciation, plague influence on CO2 via reforestration). Of the latter, one can identify 3 separate sets, i.e., post-Roman, 1400s, and ~1600, of which the ~1600 CO2 dip is particularly sharp.

    Although related, these are individual hypotheses and each needs quantification, bounding of uncertainty, attribution studies that compare versus alternate hypotheses, the usual back-and-forth arguments, etc. All that has been going on for at least 5 years, but the publications are spread out over a bunch of authors and journals, as is typical of seriously-interdisciplinary problems.

  4. 504
    Completely Fed Up says:

    “It isn’t a question of “natural vs anthropogenic”, it’s a question of “how much” of each, i.e., it’s an attribution problem ”

    I wonder since attribution often gets used as an absolute (X is attributed to Y, therefore X was caused solely by Y), could we use “apportioned” instead?

    It’s pretty hard to turn that into an absolute.

  5. 505
    CM says:

    Kevin #499,

    Thanks for the summary. IIRC, the statements that “over-attributing” hurts credibility should be, uh, attributed to Frank, rather than to me. Not that I disagree. As for the partial of attribution single events,, that was a possibility I recalled a while back, and I referenced the Stott paper then.

  6. 506


    Kevin: “CFU: …Specifically, every drought event must logically be worsened.”

    Where did I say that?

    I didn’t.

    Why are you attributing that to me and then argue against it being true?

    I was summarizing in order to try to create some clarity in this discussion. I had the feeling that none of us were quite sure any more who said what–I guess, given your response & CM’s, that that was true for me, at least!

    So now both you & I know that I missed part of your point. I’ll have to go back and check your example(s), if I get a chance. (So hard to keep up, sometimes!)

  7. 507
    Completely Fed Up says:

    re 505, apart from the made up bit, you mean. If you summarise you’re not supposed to make stuff up.

  8. 508
    Hank Roberts says:

    > archaeologists & geographers have been beavering away for years,
    > and finding there were a lot more people in the pre-Columbian Americas

    And similarly, the marine biologists have found that there were a whole lot more top predators in the oceans, because science didn’t get invented until well after the changes in populations started. The time span during which human effects first showed up needs more attention.

    Here’s one assessment of where primary productivity (photosynthesis) happens, and so where changes will show up in the atmosphere:

    Compare that to this:

  9. 509
    Frank Giger says:

    Mr. Roberts, it gets even more interesting in the SW USA, where deforestation (what little was there) helped turn it into a place unsustainable for cities.

    CFU, open invitation for a beer if you get to Alabama. Oddly enough, we’ve spent a huge amount of time talking past each other.

    I had a conversation last week with a very liberal friend who was confused about climate change and was relieved when I pointed out that 1) yes, it’s a real problem that requires action, and that 2) climate is driven by nature, but that the change in that climate is largely being driven by us. It transcends political affiliation as a problem; the conflict arises in solutions.

    We’re the second job on the weekends in the budget. Did the extra cash pay for the cable bill this month, or was that covered by the main fulltime job? Hard to say as the money is all put together in one account and we had cable before (with tight and flush months as well), but one knows the cash available has increased spending ability. Turn it backwards and stop working on the weekends and it’ll have a negative effect.

    This assumes that one is a normal American and isn’t putting the extra cash in the bank and is spending it instead.


  10. 510

    CFU, I didn’t “make anything up”–and sorry if I got you wrong. But, as I said,the whole point was to provide info to you and to me about what I was “receiving,” compared to what you (thought you) were sending.

    Mission accomplished–I guess.

  11. 511
    Septic Matthew says:

    501, Ray Ladbury, I think that you are using the word theory in an idiosyncratically narrow fashion. However, I will try to write AGW in place of “the theory of AGW” or some such.

    When a “theory” becomes a “fact” is much disputed. We accept as fact the originally posed theory that molecules and atoms absorb light, and in particular that CO2 absorbs and emits IR.

    Articles of Belief:

    Whatever might have been caused by AGW was caused by AGW.

    What clearly was not caused by AGW is a red herring.

    Any testable hypothesis other than AGW is a lie.

    Any mechanism not now known does not exist.

    [Response: What nonsense. No scientist subscribes to any of those ‘articles’. Do try to be a little serious and not resort to such blatant strawman tactics. – gavin]

  12. 512
    Doug Bostrom says:

    Septic Matthew says: 26 May 2010 at 3:52 PM

    [list of lazy canards]

    And Darwin embarked on his course of research specifically intending to overturn orthodoxy regarding Creation, right? Subsequent inquiries into natural selection and evolution were guided and shaped by what would most piss off the pious, is that the idea?

    No. Darwin was following his curiosity. The subsequent controversy was (and tiresomely still is, 150 years later) a consequence of the discovery, which began with absolutely no relationship to theology. As a matter of happenstance the conclusions collided with what made people feel happy and comfortable.

    Come on, surely you can do better?

    As to your waffling about the transition between theory and fact, here’s what the National Academy of Sciences said about the matter of anthropogenic climate change, a few days ago.

    Some scientific conclusions or theories have been so thoroughly examined and tested, and supported by so many independent observations and results, that their likelihood of subsequently being found to be wrong is vanishingly small. Such conclusions and theories are then regarded as settled facts. This is the case for the conclusions that the Earth system is warming and that much of this warming is very likely due to human activities.

    You know better? Don’t be ridiculous.

  13. 513
    Ray Ladbury says:

    SM, First, anthropogenic warming is an inevitable consequence of the current theory of climate. This climate has proven to have tremendous explanatory and predictive power–not just wrt Earth but even for other planets–e.g. Mars and Venus.

    Second, a 30 year warming trend has been observed with characteristics that are easily understood in terms of climate theory.

    Third, there is no credible alternative theory. At most there are a patchwork of suggestions that attempt to account for a tiny portion of the evidence (and mostly fail).

    You are either doing science or you’re pudknocking. If you aren’t trying to deal with all the evidence, you ain’t doing science.

  14. 514
    Phil Scadden says:

    Septic Matthew: “Articles of Belief:” I have seen some unbelievably odd things written about science before but is too far. Please justify this incredible statement by examples where climate scientists (or any scientist) are shown to subscribe to this fantasy.

  15. 515
    Jacob Mack says:

    Bottom line:

    AGW is real and full of detriments.

    AGW is probably not good for many drought prone areas and

    certainly going to worsen some droughgts.

    AGW will lead to some crop destruction and lower crop quality.

    Localized weather patterns cannot in and of themselves individually be

    directly attributed to AGW, but some are very likely to be influenced and

    when the signal and noise are better separated it is clear that not only

    internal variability is responsible. The trends make it more clear that

    AGW is at work. The laws of physics and inputs from the environment make the

    analysis more robust and with a higher degree of certainty.

  16. 516
    Hank Roberts says:

    > Please justify this incredible statement
    You realize this is equivalent to “please, pull the other one”?

  17. 517
    Jacob Mack says:

    The philosophy of science is a great pursuit but it can easily go down a dark road where everyone except the scientists “seem” to know what science is.

  18. 518
    Completely Fed Up says:

    Kevin: “CFU, I didn’t “make anything up”–and sorry if I got you wrong.”

    Uh, if you said something that I didn’t say and attribute it to me, that’s called making it up

    “But, as I said,the whole point was to provide info to you and to me about what I was “receiving,” compared to what you (thought you) were sending.”

    OK, but how did you miss the 18 other times when I told people I wasn’t saying that?

    THIS is why 8 pages have been spent on this: people aren’t reading.

    Do you get me now?

    (PS what mission accomplished? You certainly didn’t understand me)

  19. 519
    Completely Fed Up says:

    “certainly going to worsen some droughgts.”

    I would put it “almost all droughts” by reason that to undo that worsening you need a rather specific confluence of events, and that “almost” is only there because out of thousands of events, even really unlikely events are liable to turn up.

    The worsening may be unimportant, because a drought is already pretty rotten to experience, so it has to be quite a bit worse to be noticed as worse, but worse it still is.

    Heck, athletes don’t drink alcohol the day before a match because, though they won’t be affected MUCH by it after 24+ hours, the effect could lose them the match.

  20. 520
    Doug Bostrom says:

    Speaking of studying the last millennium (or more), Don Easterbrook should just stop. This is becoming really embarrassing, it’s quite awful to see somebody go down this path, whatever the reason may be.

    Easterbrook’s been casting aspersions but he’s developed a bad case of blowback:

    Cooling-gate: the 100 years of warming Easterbrook wants you to ignore

  21. 521
    manacker says:

    Jacob Mack makes a valid point:

    The philosophy of science is a great pursuit but it can easily go down a dark road where everyone except the scientists “seem” to know what science is.

    But an even “darker road” is that where “the scientists claim to know all there is to know about what climate science really is”.

    The “unknown” in climate science today remains far greater than the “known”.

    For “scientists” to claim otherwise is both ignorant and arrogant, and we all know what Einstein had to say about the two.


    [Response: Strawman. -gavin]

  22. 522
    Anonymous Coward says:

    John Mashey (#503),
    Thank you for the references.
    The “excluded middle” I referred to is the notion that carbon cycle sensitivity does not subsume all “natural” processes, especially when the temperature variations are more regional than global. I think that was an “exluded middle” in Bill Ruddiman’s short posts in this thread but I’m of course not assuming he was so cavalier in his publications. There can of course be no “excluded middle” between “natural” and “anthropogenic” as such because, strictly speaking, “anthropogenic” is a subset of “natural”.

    [Response: No it isn’t. In this context natural is exactly equal to non-anthropogenic. No more semantics please. – gavin]

  23. 523

    Ray @ 513:

    Third, there is no credible alternative theory. At most there are a patchwork of suggestions that attempt to account for a tiny portion of the evidence (and mostly fail).

    Well … there =are= credible alternatives for enough of the variation that it seems to be making a mess of the upward trend since 1998, but the only credible alternatives should end in the next 15 to 30 years, after which we’re royally screwed.

    A more complete response might be “The only alternatives are related to cyclical phenomena that are currently operating towards a cooling bias. However, as can be seen from the data, even with a strong cooling bias caused by the current Grand Solar Minimum, the data show that at best the temperature is holding stable at close to record levels. The upward trend will resume when the Grand Solar Minimum ends, at which time it may be too late.”

    Lots of spotless days in May. Total irradiation here on the ground is 80% or so of what it should be. Not a mystery to those of us who watch the sun all the time …

  24. 524
    Completely Fed Up says:

    FCH, I think Ray’s point is that those alternatives are part of the Theory Of The Climate that has the inevitable consequence of AGW when A’s are burning hydrocarbons.

    The climate models are a memplex consisting of lots and lots of things.

    SOME of those things are those things you’re pointing out as “credible alternatives”, but they are not alternatives because

    a) they don’t explain the climate on their own
    b) they are part of the Climate theory

    The alternatives are “Urban Heat Island”, “The Sun Did It”, “GCRs From A Weaker Sun” et al. They are purporting to explain the climate changes in the past and the present.

  25. 525

    FCH (#543)–not exactly heartening, is it?

    Sometimes I can really appreciate the psychological attraction of denialism: it would be so much more fun to just relax and play music, drink a beer and go hang out with some friends.

    Unfortunately, false comfort tends to cost dearly in the long run. And I resent that I may have to pay for the false comfort certain others foolishly allow themselves to indulge in.

  26. 526
    Marco says:

    @Doug Bostrom #520:
    DON Easterbrook, not Greg. Greg(g) can plead ignorance, not being a scientist himself. Don can only blame himself being a bad scientist.

  27. 527
    Doug Bostrom says:

    Marco says: 27 May 2010 at 11:40 AM

    AAGGGH! Thank you! I plead the late hour of the post. Moderators, please, can you correct that? Pretty please?

    I should know better; I’ve personally faced Dr. Easterbrook’s grim countenance as he ordered me to bicycle through a blizzard to retrieve a forgotten paper “within this half hour.”

  28. 528

    CFU @ 524:

    Thanks for the response. You misrepresented what I wrote, as usual.

  29. 529
    Anonymous Coward says:

    This is not semantics. Anthropogenic seems good enough as a category when it comes to emissions from the exploitation of fossil fuels because they were sequestered long ago, the amount burned recently is so huge, tracers such as isotopes have been studied extensively and so on.
    But, with your definition of natural, how would one go about determining the natural amount of carbon in the biosphere? Most of the biosphere interacts massively with human activity. Homo is ancient enough that we have no basline.
    The invasion of the Americas might have increased the amount of carbon in the biosphere through forest regrowth. You might call that change anthropogenic. But the carbon would presumably have stayed in the biosphere to begin with if the indigenous civilizations hadn’t cut down the forests, right? So which carbon flow is anthropogenic and which one is natural? How much of the carbon in the geologically recent sediments is anthropogenic? And so on… the concept does not strike me as being very useful when looking at early modern and pre-modern history, never mind prehistory. Thinking and communicating tends to be easier when one uses coherent concepts.

  30. 530

    Kevin @ 525:

    Yes, it’s completely depressing. The reasons for accepting “CO2 done it” are pretty well-founded in the Science. Likewise, if “Solar Minimum” is at all the cause (and I believe it is), pretty soon “Solar Minimum” ends, no? I =do= disagree with IPCC projections, but only because getting off of fossil fuels is the only way to survive economically.

    So, if we stick with fossil fuels, we’ll destroy both the environment =and= the economy. We also risk being unable to make the transition from fossil fuels to renewables because it becomes increasingly more expensive to make the switch with each passing day.

  31. 531
    Jacob Mack says:

    All quotes directly from articles from Science Direct:

    The vulnerability of ecosystem services to land use change
    M.J. Metzgera, c, , , M.D.A. Rounsevellb, L. Acosta-Michlikb, R. Leemansc and D. Schröterd

    aDepartment of Plant Sciences, Plant Production Systems Group, Wageningen University, P.O. Box 430, 6700 AK Wageningen, The Netherlands

    bDepartment of Geography, Université Catholique de Louvain, Place Pasteur, 3, B-1348 Louvain-la-Neuve, Belgium

    cDepartment of Environmental Sciences, Environmental Systems Analysis Group, Wageningen University, P.O. Box 47, 6700 AA Wageningen, The Netherlands

    dScience, Environment and Development Group, Center for International Development, Kennedy School of Government, Harvard University, 79 J.F.K. Street, Cambridge, MA 02138, USA

    Available online 18 January 2006.

    Terrestrial ecosystems provide a number of vital services for people and society, such as biodiversity, food, fibre, water resources, carbon sequestration, and recreation. The future capability of ecosystems to provide these services is determined by changes in socio-economic characteristics, land use, biodiversity, atmospheric composition and climate. Most published impact assessments do not address the vulnerability of the human–environment system under such environmental change. They cannot answer important multidisciplinary policy relevant questions such as: which are the main regions or sectors that are vulnerable to global change? How do the vulnerabilities of two regions compare? Which scenario is the least, or most, harmful for a given region or sector?

    The ATEAM project (Advanced Terrestrial Ecosystem Analysis and Modelling) uses a new approach to ecosystem assessment by integrating the potential impacts in a vulnerability assessment, which can help answer multidisciplinary questions, such as those listed above. This paper presents the vulnerability assessment of the ATEAM land use scenarios. The 14 land use types, discussed in detail by Rounsevell et al. (this volume), can be related to a range of ecosystem services. For instance, forest area is associated with wood production and designated land with outdoor recreation. Directly applying the vulnerability methodology to the land use change scenarios helps in understanding land use change impacts across the European environment. Scatter plots summarising impacts per principal European Environmental Zone (EnZ) help in interpreting how the impacts of the scenarios differ between ecosystem services and the European environments.

    While there is considerable heterogeneity in both the potential impacts of global changes, and the adaptive capacity to cope with these impacts, this assessment shows that southern Europe in particular will be vulnerable to land use change. Projected economic growth increases adaptive capacity, but is also associated with the most negative potential impacts. The potential impacts of more environmentally oriented developments are smaller, indicating an important role for both policy and society in determining eventual residual impacts.

    1. Introduction
    Many aspects of our planet are changing rapidly due to human activities and these changes are expected to accelerate during the next decades (IPCC, 2001a, IPCC, 2001b and IPCC, 2001c). For example, forest area in the tropics is declining (Geist and Lambin, 2002), many species are threatened with extinction (Thomas et al., 2004), and rising atmospheric carbon dioxide results in global warming (IPCC, 2001a, IPCC, 2001b and IPCC, 2001c). Many of these changes will have an immediate and strong effect on agriculture, forestry, biodiversity, human health and well-being, and on amenities such as traditional landscapes (Watson et al., 2000 and UNEP, 2002). Furthermore, a growing global population, with increasing per capita consumption of food and energy, are expected to continue emitting pollutants to the atmosphere, resulting in continued nitrogen deposition and eutrophication of environments (Galloway, 2001 and Alcamo, 2002). In the face of these changes, it is important to integrate and extend current operational systems for monitoring and reporting on environmental and social conditions (cf. Kates et al., 2001). Over the last decades many people have become increasingly aware of these environmental changes, such that they are now commonly recognised as ‘global change’ (Steffen et al., 2001). Many research projects and several environmental assessments are currently addressing these concerns at all relevant scales, frequently in multidisciplinary collaborations. However, integrating this wealth of information across disciplines remains a considerable challenge (Millenium Ecosystem Assessment, 2003).

    This paper aims to quantify global-change concerns, focusing specifically on changes associated with scenarios of land use change, by defining and estimating vulnerabilities. Both the vulnerability concept (Metzger et al., 2004 and Metzger, 2005) and the land use change scenarios (Rounsevell et al., 2005, Ewert et al., 2005 and Kankaanpaa and Carter, 2004 S. Kankaanpaa and T.R. Carter, Construction of European Forest Land Use Scenarios for the 21st Century. The Finnish Environment 707, Finnish Environment Institute, Helsinki (2004).Kankaanpaa and Carter, 2004; Rounsevell et al., this volume) described in this paper were developed as part of the ATEAM project (Advanced Terrestrial Ecosystem Analysis and Modelling). Detailed information about the project can be found on its website (

    Assessment on vulnerability of sorghum to climate change in India
    Aditi Srivastavaa, S. Naresh Kumar, a, and P.K. Aggarwala

    a Division of Environmental Sciences, Indian Agricultural Research Institute, New Delhi 110012, India

    Received 4 December 2009; revised 17 April 2010; accepted 21 April 2010. Available online 15 May 2010.

    It is important to analyse the impacts of climate change on target production system. However, it is more important to deduce possible adaptation strategies so that the research and developmental policies can be guided to meet the challenges of climate change. Impacts of climate change on the sorghum production system in India are analysed using InfoCrop-SORGHUM simulation model. In general, impact of climate change is projected to be more on winter crop in central (CZ) and south-central zones (SCZ), while in south-west zone (SWZ) the impacts are likely to be higher on monsoon crop. Climate change is projected to reduce monsoon sorghum grain yield to the tune of 14% in CZ and SWZ and by 2% in SCZ by 2020. Yields are likely to be affected even more in 2050 and 2080 scenarios. Climate change impacts on winter crop are projected to reduce yields up to 7% by 2020, up to 11% by 2050 and up to 32% by 2080. Impacts are projected to be more in SWZ region than in SCZ and CZ. But, the yield loss due to rise in temperature is likely to be offset by projected increase in rainfall. However, complete amelioration of yield loss beyond 2 °C rise may not be attained even after doubling of rainfall in south-central zone (SCZ) and in central zone (CZ). Results indicate that adaptation strategies like changing variety and sowing date can reduce the vulnerability of monsoon sorghum to about 10%, 2% and 3% in CZ, SCZ and SWZ regions in 2020 scenario. Adaptation strategies reduced the climate change impacts and vulnerability of winter crop to 1–2% in 2020, 3–8% in 2050 and 4–9% in 2080. This indicates that more low-cost adaptation strategies should be explored to further reduce the net vulnerability of sorghum production system in India.

    Keywords: Sorghum; Climate change; Impacts; Adaptation; VulnerabilityClimate change, water availability and future cereal production in China
    Wei Xionga, b, , , Ian Holmanc, Erda Lina, b, Declan Conwayd, Jinhe Jiange, Yinlong Xua, b and Yan Lif

    aInstitute of Environment and Sustainable Development in Agriculture, Chinese Academy of Agricultural Sciences, Beijing 100081, China

    bThe Key Laboratory for Agro-environment & Climate Change, Ministry of Agriculture, Beijing 100081, China

    cNatural Resources Department, Cranfield University, Bedfordshire MK43 0AL, United Kingdom

    dUniversity of East Anglia, Norwich NR4 7TJ, United Kingdom

    eInstitute of Quantitative and Technical Economics, Chinese Academy of Social Sciences, Beijing 100732, China

    fWater Resources Information Center, The Ministry of Water Resources of The People’s Republic of China, Beijing 100053, China

    Received 25 September 2008; revised 17 August 2009; accepted 21 August 2009. Available online 10 September 2009.

    Climate scenarios from a regional climate model are used to drive crop and water simulation models underpinned by the IPCC A2 and B2 socio-economic development pathways to explore water availability for agriculture in China in the 2020s and 2040s. Various measures of water availability are examined at river basin and provincial scale in relation to agricultural and non-agricultural water demand and current and planned expansions to the area under irrigation. The objectives are to understand the influences of different drivers on future water availability to support China’s food production. Hydrological simulations produce moderate to large increases in total water availability in response to increases in future precipitation. Total water demand increases nationally and in most basins, but with a decreasing share for agriculture due primarily to competition from industrial, domestic and municipal sectors. Crop simulations exhibit moderate to large increases in irrigation water demand which is found to be highly sensitive to the characteristics of daily precipitation in the climate scenarios. The impacts of climate change on water availability for agriculture are small compared to the role of socio-economic development.

    The study identifies significant spatial differences in impacts at the river basin and provincial level. In broad terms water availability for agriculture declines in southern China and remains stable in northern China. The combined impacts of climate change and socio-economic development produce decreases in future irrigation areas, especially the area of irrigated paddy rice. Overall, the results suggest that there will be insufficient water for agriculture in China in the coming decades, due primarily to increases in water demand for non-agricultural uses, which will have significant implications for adaptation strategies and policies for agricultural production and water management.

    1. Introduction
    Irrigated agriculture is the primary consumer of water and accounts for over 70% of total water use. More than 75% of China’s grain production is from irrigated land. Irrigation plays an important role in food security and poverty alleviation in China. Water stress is already affecting China’s grain production, particularly in the northern parts of the country (Li, 2006). Climate change, population growth, and economic development will affect the future availability of water resources for agriculture, with differing impacts in different regions. The demand for and supply of water for irrigation will not only be influenced by changing hydrological regimes (through changes in precipitation, potential and actual evaporation, and runoff at the watershed and river basin scales), but also by concomitant increases in future competition for water with non-agricultural users (Rosenzweig et al., 2004).

    There has been limited research on the coupled impacts of climate change and socio-economic development on agricultural production and water availability in China (Tao et al., 2003 F.L. Tao, M. Yokozawa, Y. Hayashi and E.D. Lin, Future climate change, the agricultural water cycle, and agricultural production in China, Agric. Ecosyst. Environ. 95 (2003), pp. 203–215. Abstract | Article | PDF (525 K) | View Record in Scopus | Cited By in Scopus (27)[Tao et al., 2003], [Rosenzweig et al., 2004], [Yuan et al., 2005] and [Xiong et al., 2009]). This paper aims to improve the understanding of how changes in crop water demand and water availability due to climate change will interact with other socio-economic pressures out to 2050. Results are presented for two periods, 2011–2030 (the 2020s) and 2031–2050 (the 2040s). We use the framework introduced in Xiong et al. (2009) which integrates several of the important challenges by linking socio-economic scenarios (SES), climate change scenarios, detailed simulation of impacts on cereal irrigation demand (for wheat, maize, and rice, China’s main staple cereals) and water availability. We explore in detail the spatial variation in water availability and demand by river basin and province. The objectives are to understand the influences of different drivers on future water availability to support China’s food production and to identify key vulnerabilities in the system and potential adaptation strategies

  32. 532
    Jacob Mack says:

    I want to add that no one should rely upon just one or two papers or just the IPCC report alone. When one has a general science and math background the IPCC report and many journals complement specialized field textbooks and manuals.

    Regional variation predictions based upon models and of course empirical data are different for each aforementioned demographics.

    AGW is past the point of being dismissed as a hypothesis or a theory in the lay person’s sense. AGW really is a fact like evolution is a fact.

    Water availability is a real issue as the planet approaches a population of 7 billion AND global climate change is further affected by green house gas emissions.

    Food productivity is a real issue too as crop yields are affected by under and over irrigation, floods, droughts AND these aspects are affected by anthropgenic means:humankinds actions.

    The birth of agriculture is a mixed blessing as it enabled more permanent settlements to be established, by living off the land and with the added nutritional value agriculture provided humans were able to produce more offspring. “To be fruiful and multiply,” was a very good idea thousands of years ago. Similarly the birth of corporations (not defending early Mercantilism or Imperialism under an oligarchy) and the subsequent development of mass production was also not an inherent “evil.” However, the globe, and more specifically, vulnerable regions faces issues of over population, rules of a wealthy few or outright dictatiors, and as in China an oppressive regime where the common workers do not have access to the goods and services they need. When one considers the older, but still relevant Hierarchy of Needs By Abraham Maslow along with more modern works, one can cleasrly see that AGW reduction/ minimizing policies need not victimize the indigent in the third world and in other developing countries. Rather, it is the worsening effects of AGW in combination with: population booms, air, water and terrestial pollution, and enhanced regional weather extremes that truly threatens them.

    No one who regularly posts here that I have seen nor any of the moderators is calling for an overnight stop to GHG emissions as that is impossible. No one is sugegsting to shut down such a percentage of GHG emitting technologies without some forms of replacement and supplementation.

    Some of us disagree on whether to use nuclear energy or not, or on how much and when GHG emissions should be lowered and how much conservation fits into the equation, but those of us who know the science behind AGW is sound are not making unreasonable requests.

    Some exnvironemtalists and conservationsists who are not scientifically literate make a bad name for the rest of us. Sometimes they do more harm than good; they may be well meaning, but they are the ones that think we should use wind power for the world alone, or they hug every tree hooked up to a chain, but do not really make an impact on the problem.

  33. 533
    Jacob Mack says:

    Finally I will end with this today, as this is not my blog:

    Consequences of climate change for European agricultural productivity, land use and policy

    This article is not included in your organization’s subscription. However, you may be able to access this article under your organization’s agreement with Elsevier.

    Jørgen E. Olesen, , a and Marco Bindib

    a Department of Crop Physiology and Soil Science, Danish Institute of Agricultural Sciences, P.O. Box 50, DK-8830 Tjele, Denmark

    b Department of Agronomy and Land Management, University of Florence, P. le delle Cascine 18, 50144 Firenze, Italy

    Received 1 August 2001; revised 8 January 2002; accepted 20 January 2002. Available online 19 February 2002.

    This paper reviews the knowledge on effects of climate change on agricultural productivity in Europe and the consequences for policy and research. Warming is expected to lead to a northward expansion of suitable cropping areas and a reduction of the growing period of determinate crops (e.g. cereals), but an increase for indeterminate crops (e.g. root crops). Increasing atmospheric CO2 concentrations will directly enhance plant productivity and also increase resource use efficiencies.

    In northern areas climate change may produce positive effects on agriculture through introduction of new crop species and varieties, higher crop production and expansion of suitable areas for crop cultivation. Disadvantages may be an increase in the need for plant protection, the risk of nutrient leaching and the turnover of soil organic matter. In southern areas the disadvantages will predominate. The possible increase in water shortage and extreme weather events may cause lower harvestable yields, higher yield variability and a reduction in suitable areas for traditional crops. These effects may reinforce the current trends of intensification of agriculture in northern and western Europe and extensification in the Mediterranean and southeastern parts of Europe.

    Policy will have to support the adaptation of European agriculture to climate change by encouraging the flexibility of land use, crop production, farming systems etc. In doing so, it is necessary to consider the multifunctional role of agriculture, and to strike a variable balance between economic, environmental and social functions in different European regions. Policy will also need to be concerned with agricultural strategies to mitigate climate change through a reduction in emissions of methane and nitrous oxide, an increase in carbon sequestration in agricultural soils and the growing of energy crops to substitute fossil energy use. The policies to support adaptation and mitigation to climate change will need to be linked closely to the development of agri-environmental schemes in the European Union Common Agricultural Policy.

    Research will have further to deal with the effect on secondary factors of agricultural production, on the quality of crop and animal production, of changes in frequency of isolated and extreme weather events on agricultural production, and the interaction with the surrounding natural ecosystems. There is also a need to study combined effects of adaptation and mitigation strategies, and include assessments of the consequences on current efforts in agricultural policy to develop a sustainable agriculture that also preserves environmental and social values in the rural society.

    Author Keywords: Global warming; Climate change; Crops; Livestock; Policy; Impact assessment; Adaptation; Mitigation; European agriculture.”

    Look at the date; not very new, but similar to recent publications on this subject.

    Cover cropping affects soil N2O and CO2 emissions differently depending on type of irrigation
    Cynthia M. Kallenbach, a, , , Dennis E. Rolstona and William R. Horwath1, a,

    a Dept. of Land, Air, and Water Resources, University of California, Davis, CA 95616, United States

    Received 27 July 2009; revised 18 February 2010; accepted 23 February 2010. Available online 23 March 2010.

    Agricultural management practices such as subsurface drip irrigation (SDI) and winter legume cover cropping (WLCC) influence soil water dynamics as well as carbon and nitrogen cycling, potentially changing emission rates of soil CO2 and N2O, principal greenhouse gases. A split plot tomato field trial in California’s Central Valley was used to evaluate the use of SDI and WLCC on event-based CO2 and N2O emissions. SDI and WLCC were compared to the region’s more conventional practices: furrow irrigation (FI) and no cover crop (NCC). Our results indicate that SDI offers the potential to manage cover crops without the significant increases in greenhouse gas production during the growing season as seen under FI cover-cropped systems. The highest N2O emissions occurred during the beginning of the rainy season in November in the FI–WLCC treatment (5 mg m−2 h−1) and the lowest in August in the SDI–NCC treatments (4.87 μg m−2 h−1). CO2 emissions ranged from 200 mg m−2 h−1 during the rainy season (winter) and >500 m−2 h−1 during the growing season. Though no differences were detected in CO2 emissions between irrigation practices, mean CO2 emissions under WLCC were 40% and 15% greater compared to NCC under FI and SDI, respectively. The treatment with the greatest effect on CO2 and N2O emissions was WLCC, which increased average growing season N2O and CO2 emissions under FI by 60 μg N2O m−2 h−1 and 425 mg CO2 m−2 h−1 compared to NCC. In SDI there was no effect of a cover crop on growing season CO2 and N2O emissions. In the rainy season, however, SDI N2O and CO2 emissions were not different from FI. In the rainy season, the cover crop increased N2O emissions in SDI only and increased CO2 emissions only under FI. Subsurface drip shows promise in reducing overall N2O emissions in crop rotations with legume cover crops.

    Keywords: N2O; CO2; Greenhouse gas; Irrigation management; Cover crop; Tomato; Nitrogen fertilizer management

    1. Introduction
    Greenhouse gas (GHG) production in cultivated soils is highly dependent on the type of agricultural practice, such as fertilizer additions and irrigation and cover crop management (Mosier et al., 1998). In Mediterranean climates, such as in California, intensive irrigation and N fertilization can lead to conditions that promote elevated CO2 and N2O emissions (Linn and Doran, 1984). This is particularly true for flood irrigation practices such as furrow irrigation (FI) that inundate the soil profile during irrigation events. However, little information exists to contrast GHG emissions from furrow versus defined irrigation delivery systems such as subsurface drip irrigation (SDI). SDI could potentially mitigate GHG production from agricultural systems by delivering water directly to crop roots in small quantities but higher frequencies compared to the inundate/dry cycle of FI. The restricted soil-wetting pattern of SDI leaves much of the soil profile and soil surface dry in comparison to FI (Hanson et al., 2000), while keeping a water-filled pore space (WFPS) of around 20–30% in the area immediately surrounding the drip line (Hanson and May, 2007). Maintaining a lower WFPS in SDI compared to FI may limit denitrification which is tightly coupled with a WFPS > 60% (Ruser et al., 2006). Furthermore, though FI delivers water less frequently than SDI, the flooding characteristics of FI lead to severe wet–dry stresses in the soil. Wet–dry cycles in the soil profile have been shown to elevate the amplitude of CO2 pulses as well as increase nitrification and N2O losses ([Rudaz et al., 1991], [Appel, 1998] and [Fierer and Schimel, 2002]).

    The use of winter legume cover crops (WLCCs) can add a substantial amount of C to the soil, mitigating a portion of agricultural soil CO2 emissions (Jarecki and Lal, 2003). However, this benefit can be offset by subsequent increases in N2O production. Cover crops, particularly N-rich legumes, increase the amount of available C and N in the soil and thus, the microbial activity that drives CO2 and N2O emissions may no longer be substrate limited ([Varco et al., 1987], [Aulakh et al., 1991], [Watson et al., 2002] and [Sainju et al., 2007]). The use of hairy vetch as a winter cover, for example, can supply between 60 and 150 kg ha−1 of N (Christopher and Lal, 2007) and, if not synchronized well with the following crop’s needs, could lead to an abundance of available C and an excess in soil-N, potentially enhancing denitrifier activity or nitrate leaching (Follet, 2001). The push to include winter cover crops to address winter runoff, water quality and soil sustainability issues requires further information on the interaction of cover crops with different irrigation practices and subsequent influence on seasonal GHG emissions ([Rosecrance et al., 2000] and Poudel et al., 2001 D.D. Poudel, W.R. Horwath, J.P. Mitchell and S.R. Temple, Impacts of cropping systems on soil nitrogen storage and loss, Agric. Syst. 68 (2001), pp. 253–268. Abstract | View Record in Scopus | Cited By in Scopus (18)[Poudel et al., 2001).”

    We do have adpatation options which can actually lower some GHG emissions within the agricultural sciences. We can modify irrigation practices along with protection of soil nutrients. There are of course various trade offs, which we already knew:)

  34. 534
    Septic Matthew says:

    511, Gavin: Do try to be a little serious and not resort to such blatant strawman tactics. – gavin]


    But that was “a little serious”, just not “very serious”.

  35. 535
    John Mashey says:

    re: #529
    This is the sort of semantic quibbling that just wastes time, because the *context* of the discussion was the specific drop in CO2 ~1600AD.

    It’s not a question of some “natural” level of CO2, assuming no one had ever cut down trees, or “natural” level of CH4, assuming no one ever did rice paddies or had cows. Those are *separate* questions, whose extent of anthropogenic influence are two of Ruddiman’s hypotheses, starting thousands of years earlier, and involving fairly long-term feedbacks.

    The plague hypotheses, especially the one involving the America’s die-off, are somewhat different, as they involve much shorter-term interactions and boundaries (like: die-offs in some places induce serious reforestration, and in others, they do not, like: the hectares/person varies by region adn over time). Sometimes, a short-term perturbation (like Pinataubo) offers good opportunities for analysis, because you at least you can ignore longer-term effects. As noted elsewhere, such effects don’t have to be unique to be useful.

    So, without getting tangled in semantic quibbling, I observe one fact, and a few interesting real questions:

    FACT: the CO2 drop ~1600 was unusual, even allowing for the usual error bars in measurements and timing.

    The questions have been mentioned earlier, but in this case they come down to:

    A: (natural drop): some combination of solar irradiance changes, volcanoes + usual CO2 feedbacks and maybe oceanic jiggles accounts for the entire drop. All that is a delta off the ongoing temperature/CO2 state (which Bill would argue was already different from equivalent timing in past interglacials, but that doesn’t matter to this argument). it is slightly awkward for the soalr part that the Maunder Minimum timing follows teh CO2 drop, but maybe timing is off.

    B: The (anthropogenic) i.e.die-off and reforestration contributed some noticeable part of the CO2 drop, which fed into the (natural) processes in A.

    People are crunching away trying to bound the various uncertainties. I still harbor some hope that if it runs out that B is plausible, there will be more work on regional fingerprint differences, and just possibly, that will shed light on differences among reconstructions. (Rutherford, et al certainly does some of that, but to end as usual “more research is required.”)

  36. 536
    Completely Fed Up says:

    Kevin, when you attribute something to someone else that wasn’t theirs, “this is making it up”.

    In what way is this misrepresenting YOU?

    You misrepresented what I said, but when I point it out, *you’re* the one being maligned????

  37. 537
    Hank Roberts says:

    Costello: … Because. Why? I don’t know! He’s on third and I don’t give a darn!

    Abbott: What?

    Costello: I said I don’t give a darn!

    Abbott: Oh, that’s our shortstop.

  38. 538
    Jacob Mack says:

    You deniars do see al the independent references we are putting up yes? Septic, FCH et al.

    I have plenty more independent lines of epxeriments, observations, proxy data, GCM results, sattelite data, crop yield analysis references available.

    Forget Google scholar and Google books, there is Science Direct and Springer Link:)

    There is lots of data on both atribution and prediction too. Granted prediction can be more difficult to resolve, but no one in the fields analyzing this stuff denies that AGW is real and poses real detriments.

  39. 539
    David Horton says:

    There is an attempt here at talking about the implication of climate change in the past for climate change in the future. Aimed at the general public. Might be useful for others to do something similar?

  40. 540
    manacker says:

    Jacob Mack

    Let me comment on your very thoughtful 532/533 posts.

    Leaving the validity of the IPCC reports aside, I believe it is valid to say that the rise of agriculture has changed our planet, as the many links you cite confirm.

    It is also beyond doubt that AGW per se is “more than a hypothesis or a theory”, and should be considered a “fact” (just like “evolution”).

    But I believe that the argument is one of degree.

    Here are the “facts”: CO2 is a greenhouse gas. GHGs absorb and re-radiate LW energy emitted from our planet’s surface, thereby contributing to warming. Without this effect our planet would probably be 33C colder than it is today, and CO2 alone is probably responsible for 5 to 8C of this natural GH effect. Atmospheric CO2 has increased since measurements at Mauna Loa started in 1958, and probably before this time, as estimated by ice core data. Humans (especially those in the industrially developed societies) emit CO2 from fossil fuel combustion. This has probably been the primary cause for the 0.4% compounded annual growth rate in atmospheric CO2 for the past 5 (or 50) years.

    Now we come to “theories and hypotheses”: a doubling of CO2 would theoretically cause GH warming of around 1C according to GH theory. Yet, if one assumes strongly net positive feedbacks with warming, primarily from water (as vapor, liquid droplets in low clouds or ice crystals in high clouds) as estimated by model simulations, one can arrive at a theoretical 2xCO2 climate sensitivity of 2.0 to 4.5C.

    So we have both “facts” and “hypotheses” at work here.

    But back to agriculture. It certainly did change our planet. It may have been a “mixed blessing” for all of the prior flora and fauna on our planet (many of which subsequently became extinct), but for mankind it was 100% positive, in that it was the key to the start of human civilization, as we know it.

    It also opened the door (much later) to increased human literacy, the Renaissance, the Age of Reason, the many discoveries of science, the Industrial Revolution, discoveries in medicine and hygiene, the age of computers, rapid communication and “instant information”, etc., all of which we take for granted today.

    You mentioned “water availability” as a limiting item for a “world population exceeding 7 billion”, which may be exacerbated by AGW. This may be so.

    You also mention food productivity as “a real issue too as crop yields are affected by under and over irrigation, floods, droughts AND these aspects are affected by anthropogenic means”. This is undoubtedly true. Will slightly warmer global temperatures and higher CO2 levels increase global crop yields, as some studies show or will the net result be negative?

    You also mention China and its oppressive regime. Having lived in China I can tell you that, despite the great amount of poverty that still exists, most Chinese are better off today than they were before the current economic upswing. This includes the young female garment workers from impoverished provinces in the north who work 40+ hour weeks in the Pearl River delta to send money back home, producing garments that are then sold in North America and Europe. The Chinese population is unlikely to “explode” under the new “one-child” rule (even if this rule is “oppressive”); it may even eventually stagnate and decline as the shortage of female children and the average age increase.

    India, which has a less oppressive regime (and no enforced “one-child” policy), may soon overtake China as the most populous nation. Is the average Indian better or worse off today than 10 years ago?

    You wrote:

    By Abraham Maslow along with more modern works, one can clearly see that AGW reduction/ minimizing policies need not victimize the indigent in the third world and in other developing countries. Rather, it is the worsening effects of AGW in combination with: population booms, air, water and terrestrial pollution, and enhanced regional weather extremes that truly threatens them.

    Opinions vary on this, Jacob. Two of the most urgent needs of the poorest individuals of this world as recognized by WHO and others, are a clean water supply and a reliable and cost-effective energy infrastructure, the lack of which together cause some 4 million deaths annually. Many of these nations have local fossil fuel deposits, which could act as the basis for building up a viable energy infrastructure. If we restrict the poorest nations to higher-cost “green” energy solutions, they will, by definition, be denied these most urgent needs for a longer period of time (and the 4 million per year will die a few years longer).

    I would agree wholeheartedly with your point that it is unreasonable to call “for an overnight stop to GHG emissions as that is impossible”, nor that one should suggest shutting down “GHG emitting technologies without some forms of replacement and supplementation”.

    You added:

    Some of us disagree on whether to use nuclear energy or not, or on how much and when GHG emissions should be lowered and how much conservation fits into the equation, but those of us who know the science behind AGW is sound are not making unreasonable requests.

    Unfortunately, nuclear energy has (rightly or wrongly) developed “political baggage” of its own (at least in the “industrialized Western nations”), which may be hard to overcome even with new thorium-based fast breeder technology or even with future nuclear fusion reactors.

    I agree fully with your point:

    Some environmentalists and conservationists who are not scientifically literate make a bad name for the rest of us. Sometimes they do more harm than good; they may be well meaning, but they are the ones that think we should use wind power for the world alone, or they hug every tree hooked up to a chain, but do not really make an impact on the problem.

    These may, in fact, have been some of those who promulgated the general fear of nuclear power, which now presents us with the political dilemma mentioned above.

    As to the studies you cited which call for policies to “support the adaptation of European agriculture to climate change”, these may well make sense, if we really know how climate is going to change. As the report states, I would see these mostly as “adaptation” measures, whereby we adapt to what is actually happening, rather than try to anticipate what might (or might not) really happen.

    I still am convinced that the weak link here is our knowledge of what the future will actually bring. If we “plan” for a future that is 3C warmer than today on average and it then turns out to be 1 or 2C cooler than today, we have “shot ourselves in the foot”.

    The most recent record has shown us that AGW has slowed down (or actually stopped) for a few years. Is this the start of a new “trend”? No one knows for sure, although the GH premise tells us that this is unlikely unless natural variability plays a greater role in our planet’s climate than we have previously assumed.

    Thanks for a very thought-provoking summary. I will check your cited references out more closely.


  41. 541

    CFU, I was feeding back to you what I was getting from what you were saying.

    Last word. Deal with it or don’t.

  42. 542

    manaker @ 540:

    The most recent record has shown us that AGW has slowed down (or actually stopped) for a few years. Is this the start of a new “trend”? No one knows for sure, although the GH premise tells us that this is unlikely unless natural variability plays a greater role in our planet’s climate than we have previously assumed.

    No, the recent record has shown us no such thing. Nor is “GH” a “premise”.

    There are natural cycles, many of which have had a downward bias according to the folks who think they actually control climate. They are cyclical, they will return to a neutral or warming bias sooner or later. When that happens, the warming trend caused by growing CO2 concentrations will be there, except the warming that will result will be greater.

    Keep this in mind — the last time the sun was as quiet as it has been, the planet cooled. That we’re holding steady — more or less — at record high temperatures should completely disabuse any legitimate skeptics.

  43. 543

    #540, manacker–

    Note that the Charney sensitivity is more than merely “hypothetical,” as you describe it. Paleo data do help constrain the possible values to the range you mention, so this is not merely “assumed” (as you also describe it.)

  44. 544
    Completely Fed Up says:

    “Yet, if one assumes strongly net positive feedbacks with warming … one can arrive at a theoretical 2xCO2 climate sensitivity of 2.0 to 4.5C.”

    Nope, not just theory.

    Actual measurement shows this to be the case.

    “So we have both “facts” and “hypotheses” at work here.”

    Not yet, unless you count the errant hypothesis that your summation is true.

  45. 545
    Ray Ladbury says:

    Wow, Max@540, what happened? That was almost reasonable. However, I think you miss on a few points. First, the detailed interplay of feedbacks is not the only hold we have on CO2 sensitivity. We have a dozen or so independent lines of evidence telling us that CO2 sensitivity is around 3 degrees per doubling, that it is almost certainly not less than 2 or more than 4.5 degrees per doubling. The level of agreement is truly remarkable. It is a mistake to ignore that evidence.

    Second, I know of no studies that predict a significant overall increase in calories or grams of protein as a result of climate change. Most show a negative impact on most critical food crops.

    Third, your contention about warming having slowed is not borne out by this year’s data. The past 12 months have been the warmest on record, and 2010 is a good candidate to break the previous record.

    I would also contend that we are screwed and tatooed if we plan for 1 degree of warming and we get 3 degrees or 4.5 if we plan on 3 degrees. Can you think of a better guide than the best science available? The consensus of experts?

    On a personal note: when were you in China? I haven’t been there since 1985, so I’m sure it is unrecognizable. It’s also been 14 years since my last trip to India–although I did make it to the subcontinent last year.

    I would say that the question of welfare depends critically on who you ask in both India and in China. There are certainly winners and losers in their development.

  46. 546

    Let me reconsider my “last word” to CFU, for something hopefully more informative.

    CFU, when somebody tells you, “Here is what I understand you to be saying,” a helpful response is “No, what I am trying to say is—.”

    “You made that up” is a good deal less so.

    Hope that helps.

  47. 547
    Completely Fed Up says:

    “CFU, when somebody tells you, “Here is what I understand you to be saying,””

    Except you didn’t.

    You said:

    “CFU: every weather event must logically be affected by AGW. Specifically, every drought event must logically be worsened

    (My thought, FWIW: This can’t be refuted as possibly true, …”

    Nothing about “Here is what I understood”.

    As to No, what I am trying to say, please check posts

    #131 #147 #148 #157 #160 #173 #175
    #176 #223 #224 #237 #238
    #239 (a poll that you haven’t answered, and CM answered a different one…)
    #240 #241
    #246 (which includes a “how this could be shown false”
    #247 #255 #262
    #263 (note, he couldn’t manage that)
    #266 #278 #300 #301 #306 #318 #328
    #336 #337 #338 #383 #385 #414 #416
    #417 #419 #427 #428 #437 #440 #449
    #450 #466 #467 #497 #498 #502

    How many times do I have to explain?

  48. 548
    Completely Fed Up says:

    #131 #147 #148 #157 #160 #173 #175
    #176 #223 #224 #237 #238
    #239 (a poll that you haven’t answered, and CM answered a different one…)
    #240 #241
    #246 (which includes a “how this could be shown false”
    #247 #255 #262
    #263 (note, he couldn’t manage that)
    #266 #278 #300 #301 #306 #318 #328
    #336 #337 #338 #383 #385 #414 #416
    #417 #419 #427 #428 #437 #440 #449
    #450 #466 #467 #497 #498 #502

    That’s 47 attempts to explain what I mean.

    And you’re still making things up, Kev. cf “when someone tries to say…” when you didn’t.

  49. 549
    manacker says:

    Ray Ladbury

    I am sure that you will agree that the empirical evidence for a GH effect and for CO2 being a GH gas is much stronger than that for the specific premise that the 2xCO2 climate sensitivity is between 2.0 and 4.5C, due to positive feedbacks.

    The actually observed warming since 1850 does not correlate that well with the actually observed increase in atmospheric CO2 and a CS of 2.0 to 4.5C. Paleo-climate evidence is much less robust that recent physical observations, due to the many uncertainties involved.

    I was last in China in late 2003, but spent quite a bit of time there between 2000 and then.


  50. 550

    #547, #548–

    Whatever, dude.