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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. 301
    Completely Fed Up says:

    “# 278: No, not always, and not in the context of regional climate changes. Droughts worsened by warming probably will happen”

    They already have happened.

    Here, look at the graph of temperatures:

    http://data.giss.nasa.gov/gistemp/graphs/

    Warmer temperatures.

    When you already HAVE a drought, is it true or not that making it warmer makes the drought more severe.

    Answer that question.

    Seems nobody reads anymore.

  2. 302
    John says:

    174
    Completely Fed Up says:
    19 May 2010 at 11:46 AM

    Namjd, AGW is climate change. If there’s no climate change, there’s no AGW. Therefore to prove AGW you have to prove climate change.

    Therefore evidence for AGW is evidence of climate change.
    —————————–

    Of course there can be massive climate change without AGW, and you don’t need to prove that at all.

  3. 303
    CM says:

    Since I’ve been less than clear about this above: I don’t claim that precipitation and evaporation are the only factors determining drought, or that warming will not bring drought if only there’s enough rain. I’m aware of the issues with the Palmer index (Brian Dodge #265). I’m also aware that precipitation increases and floods can very well go hand in hand with more or worse drought (for reasons pointed out by Ray Ladbury #281, John Mashey #273, and CFU #246).

    In the context of the recent Southeast drought and the Seager paper we were discussing, these points militate against complacency about the region’s future. (The cited projections of increased P and a “modest” reduction in P – E need not be understood as implying merely modest increases in drought risk).

    But do these points make a difference to the argument we were having over attribution?

  4. 304

    More “overt cheating” by climate change deniers: Easterbrook fakes his figures, hides the incline – http://bit.ly/a8Y6PZ

    Scott A. Mandia, Professor of Physical Sciences
    Selden, NY
    Global Warming: Man or Myth?
    My Global Warming Blog
    Twitter: AGW_Prof
    “Global Warming Fact of the Day” Facebook Group

  5. 305

    “Awhile back on Watts’s site some people had the audacity to state that since C02 is heavier than air it does not rise. Some really strange ones indeed.”

    I’ve run into this one a couple of times–I think it’s been discussed here in the past. (Not that there’s all that much to say!) Seems it’s a minor recurrent (nutso) meme.

  6. 306
    Completely Fed Up says:

    “But do these points make a difference to the argument we were having over attribution?”

    Not really, CM, because we are still talking past each other.

    I’m saying you can attribute AGW as having made the drought worse than it would otherwise have been.

    Others seem to be obsessing over attribution of the CAUSE of the drought. Dry weather CAUSED the drought. AGW made the weather hotter.

    Again, I’ll pass you back to the 1999 cooler temperatures.

    If I were to state that 1999 was affected by increasing effects of AGW, this would not twitch an eyebrow.

    There would be only a few denier-types saying “wrong”.

    But it WAS cooler than 1998. Or 2003, etc.

    The effect of AGW on that years’ temperature is evidenced by still being warmer than the warmest year before 1985.

    Yet we don’t have Jacob saying AGW has had no effect on the temperature in 1999 because that year was within normal variation seen before, do we?

    Why here?

    Because (this is my intimation) people are asserting that somehow I’m saying that AGW caused this drought. And that I’m attributing the entire drought to AGW’s effects.

    I’m only attributing some of the dryness of the drought to AGW.

    That our models are not accurate enough in detail to attribute X drop in precipitation to weather events and Y drop in precipitation to climate change doesn’t mean that there was no effect from climate change.

    You see, I don’t disagree with those who say that AGW is not proven by one drought. I disagree with people saying I’m wrong in attributing some of the depth of the drought to AGW because the drought doesn’t prove AGW.

  7. 307
    Completely Fed Up says:

    “Of course there can be massive climate change without AGW, and you don’t need to prove that at all.”

    for Namij we do.

    How about you?

    What do YOU think has caused this climate change?

  8. 308
    Completely Fed Up says:

    “I got to wondering: Was that an appeal to authority?”

    No.

    It was an appeal to logic: if someone keeps saying stuff that means AGW is not a problem, and spouts lies about how temperatures have possibly paused (it hasn’t, as shown by actual evidence), then this logically means that the person continuing to avoid facing a problem does not WANT there to be a problem.

    Hiding their head in the sand.

    An appeal to logic.

  9. 309
    Gilles says:

    CFU “What do YOU think has caused this climate change?”

    Very honestly, if I didn’t read newspaper, I would have never thought there is a climate change at all. I have travelled all around the world, I’ve seen very different climates, and I do not know any place where the climate has changed following the usual taxonomy ( arctic, oceanic, continental, tropical, and so on…, or more precisely for instance the Köppen climate classification http://en.wikipedia.org/wiki/Köppen_climate_classification ).

    And this simply because I do not know any place in the world where “changes” have exceeded significantly ( statistically speaking ) the known natural, preanthropogenic, local variability. This is of course not incompatible with the fact that the global average has significantly changed, but this doesn’t imply that the LOCAL climates have changed. So your question is a kind of non sequitur.

  10. 310
    Completely Fed Up says:

    Again, Gullible doesn’t answer the question and takes paragraphs to do so.

  11. 311
    Completely Fed Up says:

    John (#302) You were saying..?

  12. 312
    Doug Bostrom says:

    Scott A. Mandia says: 21 May 2010 at 6:14 AM

    Easterbrook fakes his figures, hides the incline – http://bit.ly/a8Y6PZ

    And misspells “Younger Dryas”, which I was perversely delighted to see highlighted in the deconstruction.

    Definitely worth a look-see, though I have to say I’m beginning to feel pretty degraded by following some of this stuff and witnessing my own responses. Dr. Easterbrook was a prof of mine, way back when, and though I did not particularly bond to him I’m still kind of sorry to see what happens when emerititus gets a full grip on a formerly productive scientist.

  13. 313
    flxible says:

    Gilles produces the true “non sequitur”:
    “Q: What has caused climate change?
    A: News stories.”
    How can the average change significantly without any of the individual points changing??

  14. 314
    Gilles says:

    “How can the average change significantly without any of the individual points changing??”
    Think about it … (it’s not “without any of the individual points changing”, it is “without any of the individual points changing significantly”)
    Another thing is that “climate” is not a mere function of average temperature, but also of the amplitude of temperature variability, precipitations (both in amount and in repartition) , etc … Changes in the average temperature are far from catching the possible “climate change” and as far as I know, the changes observed in any of these parameters anywhere in the world are still far from producing a “different climate”.

  15. 315
    CM says:

    Ah, more word games, from Gilles (#309) this time. Gilles, you may want to familiarize yourself with the distinction between climate change and climate shift or climate regime shift as used by the IPCC.

  16. 316
    dhogaza says:

    And this simply because I do not know any place in the world where “changes” have exceeded significantly ( statistically speaking ) the known natural, preanthropogenic, local variability. This is of course not incompatible with the fact that the global average has significantly changed, but this doesn’t imply that the LOCAL climates have changed. So your question is a kind of non sequitur.

    This just means that you’re out of touch with nature. Perhaps if you spent more time birding or gardening or the like, you’d be more perceptive of the local and regional changes people who are in touch with the world have seen over the past decades.

  17. 317
    Ray Ladbury says:

    Gilles says: “Very honestly, if I didn’t read newspaper, I would have never thought there is a climate change at all.”

    Are you sure you’re not channeling Nixon? Maybe if we all just close our eyes and wish with all our might, it will go away, huh?

    Actually, we can tell a lot about Gilles from this statement:
    1)He doesn’t garden.
    2)He’s not very observant
    3)He loves word games.

  18. 318
    Completely Fed Up says:

    CM et al, Gilles has shown why Jacob’s statement is wrong and why I argued it that way.

    “it’s not “without any of the individual points changing”, it is “without any of the individual points changing significantly””

    That’s exactly what Jacob said.

    And Gilles is wrong as Jacob is wrong: if you increase the effect on ANY event (e.g. you’re God) by 4% then the chance of getting an event weaker than the previous average is ~48%. Therefore you’d need ~400 events to note the change and ascertain it was a 4% increase.

    EVEN THOUGH you have not, by the time 20 events have occurred been likely to see anything outside the normal range of events.

    Yet there HAS been an effect.

  19. 319
    RichardC says:

    314 Gilles said, “it is “without any of the individual points changing significantly”)” and ““climate” is not a mere function of average temperature”

    Most points have to change significantly for the average to change significantly.

    Raise the temperature a bit and the arctic sea ice melts, creating an ocean where effectively land used to exist. The gross functioning of climate systems will change.

  20. 320
    John E. Pearson says:

    317: Ray said Gilles is not very observant. etc.

    I’ll tell you what I saw recently that blew me away. Rain. Hard driving rain. An hour after sunset. At 10,000′ in the Rocky Mountains. In February. Over the last two decades I’ve watched the winter rain. Twenty years ago we didn’t get winter rain at all. Then, we started seeing the occasional rain shower at 5,500′, but much above that we’d get only snow. Then eventually we started seeing gully washers at 5,500′. Then we started getting rain showers at 7,200′. Then gully washers at 7,200′. This year was the first time I ever saw winter rain at 10,000′. That rain did turn to snow later on that evening, but jimminy, it was pouring rain at 10,000′ in the Rocky Mountains in the dead of winter an hour after sunset. I know. I know. I can’t attribute the weather trend I’ve observed to global warming.

  21. 321
    John Mashey says:

    re: #296
    OT, but in the interests in peace in CA…
    jacob:
    I’m a 27-year CA resident who’s given talks at UCBerkeley, UCDavis, UCLA, UCSD, UCSB, at least, and grew up on a farm, and attended Penn State, which has a not-bad ag school. I’ve been at UCB more often, and UCB is a great school, with a fine Ag Econ department (not the same thing), BUT if you actually visit places, great ag schools tend not to be located in dense urban areas…

    UC Davis includes one of the *top* ag engineering schools:

    US News&World Report, tied for #4 (and I’ve visited 10 of the top 12 schools). Compare:
    Davis:
    Among the top five in the nation, according to The Chronicle of Higher Education’s “Top Research Universities Faculty Scholarly Productivity Index 2007,” these doctoral programs:

    * Soil Science: #1
    * Entomology: #1
    * Plant Pathology: #2
    * Evolutionary Biology: #2
    * Agricultural and Resource Economics: #2
    * Animal Biology: #3
    * Horticulture and Agronomy: #3
    * Biological Sciences: #4″

    UCD is especially famous for its oenology, but really, it is one of the very top schools in the world in agricultural research.

  22. 322
    dhogaza says:

    UCD is especially famous for its oenology

    I’ll drink to that!

  23. 323

    dhoganza @ 316:

    This just means that you’re out of touch with nature. Perhaps if you spent more time birding or gardening or the like, you’d be more perceptive of the local and regional changes people who are in touch with the world have seen over the past decades.

    It’s also possible this is the result of a psychological process known as the “least perceptible change”. It’s why you don’t notice gradual changes in people until they’ve reached some point of changing.

    If he’s traveling as much as he indicates, it’s possible that he’s confusing seasonal variations with climate variations. It took me three or four winters of not wearing heavy coats to realize that it had been three or four winters.

    Even with birding and other nature activities, it’s easy to miss a major change unless you take notes and compare what you saw one season to what you see this season.

  24. 324
    John E. Pearson says:

    BY the way, if anyone knows where to get monthly rainfall data at specific places in the Rocky Mountains I’d love to see it. I’ve made a few half-hearted attempts to find rain-fall data but have found only monthly precipitation data in which no distinction is made between rainfall and snowfall. My belief is that high alititude winter rain in the southern rockies was exceedingly rare until recently and that it is now growing in frequency but I have nothing to support that assertion other than my own observations.

  25. 325
    Jeffrey Davis says:

    If it’s raining, there’s not a lot of drought going on.

    Drought is insufficient rain.

  26. 326
    Edward Greisch says:

    Watch the farm report “Ag Day” on TV. Right now we are having both regions of drought and regions of crops washed away by too much rain. They showed drought regions on a map. There are many regions of each. The regions are not all concentrated in one corner of the map. Regions alternate between too much and too little rain. Of course the regions will be different at another time.
    Theorists: Please watch Ag Day. You need the ground truth.

  27. 327
    jacob mack says:

    jim, i have friends born and raised in california who graduated Berkeley. There are also plenty of publications out of Berkeley. Iam not sure why you insist on being cofrontational and sarcastic over a well established fact. I have been to Berkeley many times and they are not just an econ school.

    [Response:Well, because you don’t know what you’re talking about, but think and talk like you do, and I don’t much care for that type thing. Davis has been the ag school from its earliest inception as the university farm, producing huge volumes of peer-reviewed, applied research results for decades, particularly with respect to plant agriculture. Most people know this. There’s absolutely no comparison to the gray papers and committee reports and other whatnot that you linked to from Berkeley, which focuses mainly on policy and economics and has NO agricultural departments. But believe whatever you want. And all further comments on this topic are OT–Jim]

  28. 328
    Completely Fed Up says:

    “325
    Jeffrey Davis says:
    21 May 2010 at 12:20 PM

    If it’s raining, there’s not a lot of drought going on.

    Drought is insufficient rain.”

    That is right, captain obvious.

    Now, look again: that was said to someone who said that rain was important to forming a drought.

    Not when the drought is already there: the rain situation is already set: not enough.

    PS I note that you didn’t actually find where someone talked about how the drought was caused by AGW.

    Epic Fail.

  29. 329
    dhogaza says:

    Even with birding and other nature activities, it’s easy to miss a major change unless you take notes and compare what you saw one season to what you see this season.

    Gardeners and birders tend to be record keepers, which is one reason I mentioned both of those. Or, if one doesn’t keep one’s own records, one tends to depend on those kept by others, such as those that lead to the delineation of horticultural zones and recommended plantings and times to plant here in the US, bird guides with seasonal range maps, etc.

  30. 330
    Doug Bostrom says:

    FurryCatHerder says: 21 May 2010 at 12:11 PM

    If he’s traveling as much as he indicates, it’s possible that he’s confusing seasonal variations with climate variations. It took me three or four winters of not wearing heavy coats to realize that it had been three or four winters.

    It’s a creeping sort of thing, on a time scale we’re not good at working with and besides that highly susceptible to our malleable memories.

    I finally (thank you, flying spaghetti monster or whatever) returned to the Seattle area after a multi-decade excursion through parts East. Seattle of course is notorious for rain, but in my early memory it’s fixed as mostly continuous drizzle during the fall and winter months.

    I could -swear- now that I’m back I’m seeing a lot more drenching rain, episodic showers that remind me of what I see upslope on the windward side of the Big Island out in Hawaii though not of course as intense. Our house here had its bottom floor inundated in a storm in December of 2007 before we’d managed to move in, the most recent of several 25, 50 or 100 year events packed into a relatively brief period.

    Is this climate? Is my memory correct? All I can really do is rely on statistics, big collections of events carefully recorded. So looking to my own experience although Gilles is terribly annoying in many ways I think his personal observations are entirely plausible.

    Fortunately we don’t have to rely on our own anecdotes, our flexible and suggestible memories. There’s a mass of statistics telling us our intuitive noses are probably smelling something real. But if mental comfort is what we want, we can train ourselves to find it, make our memory work for what we want.

  31. 331
    Jacob Mack says:

    http://enviro.berkeley.edu/researchcent

    http://bwc.berkeley.edu/home/

    I love RC and I do not want to continue in a conversation that is fruitless,
    but again all the relevant links to UC Berkeley research, and I am done.

    [Response: Not relevant and OT]

  32. 332
    Hank Roberts says:

    John, have you looked for streamflow data? That would change dramatically with a change from snowfall to rainfall. Here for example (just an example, you can find much more):
    http://journals.ametsoc.org/doi/full/10.1175/JCLI3321.1
    Journal of Climate 2005; 18: 1136-1155
    Changes toward Earlier Streamflow Timing across Western North America
    “The highly variable timing of streamflow in snowmelt-dominated basins across western North America is an important consequence, and indicator, of climate fluctuations. Changes in the timing of snowmelt-derived streamflow from 1948 to 2002 were investigated in a network of 302 western North America gauges by examining the center of mass for flow, spring pulse onset dates, and seasonal fractional flows ….”

  33. 333
    CRS says:

    Regarding Ag Engineering….I notice that University of Illinois in Urbana is ranked Number 1! Glad I have all three of my degrees from UI.

    http://www.universityportal.net/2008/03/top-university-of-agricultural.html

    That is where I started research in manure biomethane mitigation back in 1979. They are doing some outstanding work in practical applications of climate change mitigation, it’s a fun place to hang out. Unfortunately, the state of Illinois is flat broke, and the UI is in turmoil lately. Biomass happens I guess.

  34. 334

    #309 Gilles

    Your supposition is based on your opinion, not the measured (statistically significant) changes that are actually occurring. You see, it does not matter what you think, it matters what is actually happening.

    Here are only ‘some’ things that are happening that is measured by observation indicating climate shift:

    – Altitudinal shift
    – Latitudinal shift
    – Seasonal shift
    -Migration times
    – Fire seasons
    – Planting times
    – Soil moisture content
    – Humidity factors: global, latitudinal and regional
    – Arctic ice loss
    – Global deglaciation
    – Antarctic ice extent increase vs. Antarctic ice mass loss
    – Drought trends based on trend and forcing
    – Changes in radiative forcing

    Well, this is just the short list. Back in reality, your opinion or perspective means nothing when weighed against actual changes around the world.

    All you have really proven is that your perspective is inadequate to the task at hand. I hope you are not in a position of serious importance. Incompetence in capacity of understanding is not a desired trait in a position of responsibility, especially if it has to do with the well being of the public.

    By the way, why don’t you post your full name again?

    #314 Gilles

    The political term Gilles is waving here is “as far as I know”. Goodness, could we get a little more wiggle room in here. . . oh never mind, there’s enough.

    John Coleman has begun using that phrase as well. . . how convenient. Kind of an attorney General Gonzales moment.

    Back in reality, you obviously know very little on this subject.


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  35. 335
    CM says:

    CFU #306, let’s try again.

    > I’m saying you can attribute AGW as having made the drought worse than
    > it would otherwise have been.

    I’ll nearly agree with you: You can attribute AGW as having made a drought more likely to happen or to be worse than it would otherwise have been.

    To the extent one cannot say of a specific weather event that it was caused by anthropogenic climate change/global warming, I think one also cannot say that the event was made worse by AGW. Both the event happening, and its intensity, could always be “just weather”. What one can say, if the models so suggest, is that climate change increased the risk of the event occurring, or increased the risk of the event being worse. If by warming the planet we made an unlikely extreme event hugely more likely to happen, then there is at least a statistical sense in which we can reasonably attribute the event at least in part to AGW without worrying about the philosophical niceties of whether it was “caused” by AGW. (Cf. <a href="http://www.nature.com/nature/journal/v432/n7017/abs/nature03089.html"Stott et al. 2004, discussed by Gavin on an earlier thread).

    From what I’ve read here, though, it seems the Southeast drought was not all that unlikely an event. and that the models do not project a very strongly AGW-increased risk of drought in the Southeast. Don’t ask me to quantify but I’d doubt you could make such an attribution significant.

    I also don’t follow your argument upthread that “there already was a drought, warming made it worse” (or words to that effect). AGW does not only affect temperatures and leave other things the same. It also tends to influence such things as how much rain falls where. So if a heatwave is not just weather, but weather that has been made more likely to happen by AGW, by the same token a lack of rain has also been made more or less likely by AGW. And if the models say AGW makes the precipitation extreme that caused a drought less likely, the drought will be harder to attribute to AGW.

    Can we end it about here?

  36. 336
    Completely Fed Up says:

    “You can attribute AGW as having made a drought more likely to happen or to be worse than it would otherwise have been.”

    I’ll go along with that.

    I would add that, absent any detail of how it didn’t make it worse, the default would be it did make it worse.

    Note: Frank would call you completely and utterly wrong in your statement.

    The reasoning for that proviso I added is the same that would be the basic nullity that AGW uses: CO2 is a greenhouse gas, we’re adding CO2 to the atmosphere, we’re warming the atmosphere, we’re warming the planet.

    The arguments against the conclusion there are the same ones you need for my proviso: it’s possible that it is false, but the burden is on you to show it false.

  37. 337
    Completely Fed Up says:

    “I think one also cannot say that the event was made worse by AGW. Both the event happening, and its intensity, could always be “just weather”.”

    I still say you have this wrong and you should prove it. All you’ve managed is to state it. And again I would pass this on to an analogy that you must deal with:

    Is the 1999 temperature NOT affected upward by the excess of CO2 humans have placed in the atmosphere over the preceeding 12 decades?

    I say yes.

    What do YOU say?

  38. 338
    Completely Fed Up says:

    “AGW does not only affect temperatures and leave other things the same. It also tends to influence such things as how much rain falls where”

    So show that AGW shifted rain into SE US and made drought there less.

    That would be proof.

    What RodB produced in #116 was not.

    (yes that’s really the same thing said three times, but maybe one of them will make my position click)

  39. 339
    flxible says:

    Doug Bostrum: “So looking to my own experience although Gilles is terribly annoying in many ways I think his personal observations are entirely plausible.”

    Of course his ‘personal observations’ are “plausible”, the problem is they are those of a short term flyby, simply noting that the nominal “regional climatic classification” still holds, like the arctic is colder than the tropics, which in turn are hotter than the temperate zone …. well la-te-da.

    Had he spent 5 or 10 continuous years in any of the places he’s traveled to, he might have a bit more perspective on what global climate change means to any single regional climate.

    Being a bit north of you, for the last 35+ years straight, I’ll confirm your observation that the PNW rain patterns are different than they have been historically, but Gilles on his holiday would observe that the regional climate is as it has always been “Köppen climate classified”, dry-summer subtropical or Oceanic. Meaningless regarding global climate change.

  40. 340
    Ibrahim says:

    Maybe OT :-)

    Do recent study’s in past climate still confirm that the MWP was rather regional then global?

    Are there new study’s wich give more clarity in the forcings wich lead to the strong warming from about 1910 till about 1945?

    How is the devolepment in the “bucket-question” (stark cooling about 1945).

    If Pinabo wouldn’t have happenened would temperatures be much higher?

    Same question for the of polution wich caused the temperatures to be flat from about 1948 untill 1978?

    Regards

  41. 341
    Doug Bostrom says:

    flxible says: 21 May 2010 at 3:50 PM

    True enough, stand in any one spot and one’s effective latitude still appears to be shifting, these days.

    Interesting what you say about rain. The point I was thinking about but failed to properly express was that having grown up here and become accustomed to typical weather and then left for a long time, when I returned it seemed like there was a distinct difference and this was perhaps easier to see because I was familiar with the old yet was not continuously exposed to a slow change which thus might fade into imperceptibility. Which of course feeds into remarks about Gilles being itinerant and thus not really well equipped to judge his surroundings.

    But I may be a particularly oblivious person so I’m happy that longitudinal data is available to test my perceptions against.

  42. 342
    Hank Roberts says:

    Gilles: http://www.shiftingbaselines.org/videos/index.html
    Of course you don’t notice change. It takes reading and recordkeeping to notice change.

  43. 343
    jacob mack says:

    CFU try reading the IPCC report

  44. 344
    Anand says:

    Mr David Benson

    William Happer says:
    “Additional increments of CO2 will cause relatively
    less direct warming because we already have so much CO2 in the atmosphere that it has blocked most of the infrared radiation that it can. The technical jargon for this is that the CO2 absorption band is nearly “saturated” at current CO2 levels. Adding more CO2 is like putting an additional ski hat on your head when you already have a nice warm one below it, but you are only wearing a windbreaker.”

    Which is like what I posted some time back., to which you replied – “read the IPCC AR4”.

    I will read it thoroughly (I have mainly read and tried to understand paleo chap 6). But you should be able to answer this simple query, in the light of such proclamations which repeatedly do pop up:

    If all these bigshot scientists are saying this about the CO2 GHG effect yield, there must be some truth to it.

    [Response: A touching thought, but unfortunately one that is not borne out by the facts. Happer is just wrong. The forcing from increasing CO2 is roughly 5.3*log(CO2/CO2_o) which is not zero, and indeed is roughly equivalent to the increase of forcing of just under 2% in solar irradiance. Or is that negligible as well? – gavin]

    Does it not, then follow, that an MWP-LIA CO2 dip (whatever the cause be), have a greater contribution to temperatures, than increases in CO2 have on warming today?

  45. 345
    John Mashey says:

    Anand: do you know that Will Happer is the Chairman of the George C. Marshall Institute, and this is rather more relevant to his testimony than his work at Princeton? The CEO of GMI is William O’Keefe, a 25+-year veteran of the American Petroleum Institute. If this is unknown to you, but you actually want to understand, try PDF here.

    Happer also stated that polar bears will be just fine, so will corals, and any concern over global warming is like Prohibition.

  46. 346
    Jason Miller says:

    #334 – John P. Reisman

    I don’t understand what you mean by “Antarctic ice extent increase”. I’ve had a subscription of National Geographic’s Desk Diary since 1998. In the back are maps, one of which is of Antarctica. I placed the 1998 and 2010 page sized maps side by side and did a comparison. The changes over the last dozen years are quite dramatic:

    West Ice Shelf – Narrowed by around 1/4 to 1/3 from its 1998 size.

    Shackelton Ice Shelf – There was an ice peninsula in 1998 which is now a nub and the other end has narrowed.

    Cape Poinsett to Porpoise Bay – The widest part is gone, and the once continuous ice shelf is now two separate ice shelves.

    Glacier West of the Magnetic South Pole – In 1998 there was a small glacier in a small bay, in 2010 there is now an ice peninsula extruding from Wilkes Land. This is the only growth I noticed and it is a calving glacier….

    Ross Ice Shelf – It has receded to Roosevelt Island.

    Larsen Ice Shelf – The northern most section has narrowed and the already narrow part around Mt. Jackson is gone.

    Ronne Ice Shelf – It has recede, but less than the other large ice shelves.

    Coats Land to American Highland – This part of the coast line appears to be holding its own with regard to the ice shelves.

    #309 Gilles – “And this simply because I do not know any place in the world where “changes” have exceeded significantly ( statistically speaking ) the known natural, preanthropogenic, local variability.”

    The above is a lot of change in only 12 years.

  47. 347
    jacob mack says:

    Googling global warming and the hydrologic cycle is also helpful. The water encyclopedia discusses most of the issues we have in terms of precipitation,droughts.crop yields,and thelike. UC Davis has some great research published on how some plants temporarily grow larger and then stagnate and sometimes die due to the C02 inhibiting nitrate formation of proteins. UC Berkeley has excellent research published in Bio engineering and Bio meteorology regarding preserving crop yields, predicting future yields and weather patterns. The IPCC report is clear on probable worsening of both floods and droughts. Also discussed are areas in upper latitudes where crops will more likely grow due to a warmer climate. An article from1985 published in Nature asserted that AGW was outpacing plant life evolutionary adaptations. In some current research this does not completely hold. Two possible explanations are punctuated equilibrium and more mild adverse regional weather changes in select locations.Africaispronetofloodsanddrou

  48. 348
    Hank Roberts says:

    > Jason Miller
    > Antarctic sea ice

    Distinguish sea ice from ice shelves.

    This explains the observed change in Antarctic sea ice, as predicted:
    http://moregrumbinescience.blogspot.com/2010/03/wuwt-trumpets-result-supporting-climate.html
    This charts the trend:
    http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.anomaly.antarctic.png

  49. 349
    Ray Ladbury says:

    Anand says, “If all these bigshot scientists are saying this about the CO2 GHG effect yield, there must be some truth to it.”

    Interesting.

    So why do you choose to believe the few “bigshot scientists”–most of them ad libbing well outside their expertise–rather than the thousands of scientists who actually publish in climate science?

    Why do you choose to believe a tiny minority of “bigshot scientists” rather than every profesional organization of scientists that has taken a position on the subject?

    Why do you choose to believe a few “bigshot scientists” rather than the National Academy of Sciences, which reiterated its concern–and much more forcefully than ever before–just the other day?

    And most of all, why do you choose to believe a handful of “bigshot scientists” instead of the evidence?

    Interesting, don’t you think?

  50. 350
    Anand says:

    Ray:
    I think like you too.

    You have thousands on one side. Among them, not all are experts on the CO2 radiative forcing property. That is only a handful. Happer’s credentials are in the same area of research.

    He makes this statement to the Congress. This same statement was made by Lindzen.

    That is why I ask.

    Gavin: Are you saying that all you need is that one formula to warm up the climate? I always thought the sensitivity of the climate to CO2 is an inferred value.

    [Response: No. But you quoted a statement about saturation – which goes to the issue of forcing, not response. If co2 was saturated, the forcing would be negligible. It isn’t. What the response might be is a wholly different question, and which neither you nor Happer got to. – gavin]

    Trenberth has argued that some heat has gone ‘missing’ Is it possible that some heat went missing in the LIA and then turned up again into the account during the late 20th century?