NASA Study Finds 1934 Had Worst Drought of Last Thousand Years

A new study using a reconstruction of North American drought history over the last 1,000 years found that the drought of 1934 was the driest and most widespread of the last millennium.

Using a tree-ring-based drought record from the years 1000 to 2005 and modern records, scientists from NASA and Lamont-Doherty Earth Observatory found the 1934 drought was 30 percent more severe than the runner-up drought (in 1580) and extended across 71.6 percent of western North America. For comparison, the average extent of the 2012 drought was 59.7 percent.

farmer and sons during a dust storm in Cimarron County, Oklahoma, 1936

This photo shows a farmer and his two sons during a dust storm in Cimarron County, Oklahoma, 1936. The 1930s Dust Bowl drought had four drought events with no time to recover in between: 1930-31, 1934, 1936 and 1939-40.Image Credit: Arthur Rothstein, Farm Security Administration

“It was the worst by a large margin, falling pretty far outside the normal range of variability that we see in the record,” said climate scientist Ben Cook at NASA’s Goddard Institute for Space Studies in New York. Cook is lead author of the study, which will publish in the Oct. 17 edition of Geophysical Research Letters.

Two sets of conditions led to the severity and extent of the 1934 drought. First, a high-pressure system in winter sat over the west coast of the United States and turned away wet weather – a pattern similar to that which occurred in the winter of 2013-14. Second, the spring of 1934 saw dust storms, caused by poor land management practices, suppress rainfall.

“In combination then, these two different phenomena managed to bring almost the entire nation into a drought at that time,” said co-author Richard Seager, professor at the Lamont-Doherty Earth Observatory of Columbia University in New York. “The fact that it was the worst of the millennium was probably in part because of the human role.”

Brown colors of the PDSI indicate strong drought conditions across the U.S., in summer of 1934.

Brown colors of the Palmer Drought Severity Index, or PDSI, indicate strong drought conditions across the United States in the summer of 1934. PDSI was calculated from monthly averages of precipitation, temperature and other factors from 1934, available from the Climate Research Unit.

According to the recent Fifth Assessment Report of the Intergovernmental Panel on Climate Change, or IPCC, climate change is likely to make droughts in North America worse, and the southwest in particular is expected to become significantly drier as are summers in the central plains. Looking back one thousand years in time is one way to get a handle on the natural variability of droughts so that scientists can tease out anthropogenic effects – such as the dust storms of 1934.“We want to understand droughts of the past to understand to what extent climate change might make it more or less likely that those events occur in the future,” Cook said.

The abnormal high-pressure system is one lesson from the past that informs scientists’ understanding of the current severe drought in California and the western United States.

“What you saw during this last winter and during 1934, because of this high pressure in the atmosphere, is that all the wintertime storms that would normally come into places like California instead got steered much, much farther north,” Cook said. “It’s these wintertime storms that provide most of the moisture in California. So without getting that rainfall it led to a pretty severe drought.”

This type of high-pressure system is part of normal variation in the atmosphere, and whether or not it will appear in a given year is difficult to predict in computer models of the climate. Models are more attuned to droughts caused by La Niña’s colder sea surface temperatures in the Pacific Ocean, which likely triggered the multi-year Dust Bowl drought throughout the 1930s. In a normal La Niña year, the Pacific Northwest receives more rain than usual and the southwestern states typically dry out.

But a comparison of weather data to models looking at La Niña effects showed that the rain-blocking high-pressure system in the winter of 1933-34 overrode the effects of La Niña for the western states. This dried out areas from northern California to the Rockies that otherwise might have been wetter.

As winter ended, the high-pressure system shifted eastward, interfering with spring and summer rains that typically fall on the central plains. The dry conditions were exacerbated and spread even farther east by dust storms.

“We found that a lot of the drying that occurred in the spring time occurred downwind from where the dust storms originated,” Cook said, “suggesting that it’s actually the dust in the atmosphere that’s driving at least some of the drying in the spring and really allowing this drought event to spread upwards into the central plains.”

A "black blizzard" dust storm in South Dakota, 1934.

A “black blizzard” dust storm in South Dakota, 1934.Image Credit: National Archives FDR Library Public Domain Photographs

Dust clouds reflect sunlight and block solar energy from reaching the surface. That prevents evaporation that would otherwise help form rain clouds, meaning that the presence of the dust clouds themselves leads to less rain, Cook said.

“Previous work and this work offers some evidence that you need this dust feedback to explain the real anomalous nature of the Dust Bowl drought in 1934,” Cook said.

Dust storms like the ones in the 1930s aren’t a problem in North America today. The agricultural practices that gave rise to the Dust Bowl were replaced by those that minimize erosion. Still, agricultural producers need to pay attention to the changing climate and adapt accordingly, not forgetting the lessons of the past, said Seager. “The risk of severe mid-continental droughts is expected to go up over time, not down,” he said.

Read the paper at Geophysical Research Letters

The Worst North American Drought Year of the Last Millennium: 1934

Benjamin I Cook, Richard Seager and Jason E Smerdon

Abstract

During the summer of 1934, over 70% of Western North America experienced extreme drought, placing this summer far outside the normal range of drought variability and making 1934 the single worst drought year of the last millennium. Strong atmospheric ridging along the West Coast suppressed cold season precipitation across the Northwest, Southwest, and California, a circulation pattern similar to the winters of 1976–1977 and 2013–2014. In the spring and summer, the drying spread tothe Midwest and Central Plains, driven by severe precipitation deficits downwind from regions of major dust storm activity, consistent with previous work linking drying during the Dust Bowl to anthropogenic dust aerosol forcing. Despite a moderate La Niña, contributions from sea surface temperature forcing were small, suggesting that the anomalous 1934 drought was primarily a consequence of atmospheric variability, possibly amplified by dust forcing that intensified and spread the drought across nearly all of Western North America.

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96 thoughts on “NASA Study Finds 1934 Had Worst Drought of Last Thousand Years

  1. just imagine the Wailing And Gnashing Of Teeth that we would hear from the government and scientists alike if the 1934 drought happened today.
    So please tell us Learned Scientists, if the 1934 drought was ” far outside the normal range of variability”, then what caused it? It certainly wasn’t CO2 then, so why assume it must be CO2 now?
    It is just possible that Science doesn’t actually know what the “normal range of variability” is? And thus continues to see everything caused by nature as “abnormal”?

  2. If they keep shipping the water from the mountians to the cities in California it will have the same effect as bad agricultural practices in the 1930s. Let the central valley have all the water for irrigation and the drought will disappear.

    • Agreed! The government of California is doing the same thing to the central valley that the Soviets did to the Aral Sea. They are diverting the water for other uses.

    • How much water actually goes to the cities? I’d like to have actual data.
      I once interviewed for a contract job at a government water agency. I learned that much of the water used by households is recycled, reprocessed (decontaminated, sanitized and made safe for drinking) and reused. But almost all water used outdoors went in the storm sewers and was lost. Of course municipal water systems have leaks and I can’t tell you what percent of household water gets reprocessed. It’s always nice to know the facts before attributing blame.

      • I don’t have a lot of (or any) scholarly references, but I will tell you that there are I am sure authoritative sources that will tell you that every drop of water in the Owens Valley belongs to the Metropolitan Water District in Los Angeles.
        The Colorado and the California Aqueducts are sort of self documenting.
        My private opinion is that the southern San Joaquin was returned to the salty barrenness that I remember as a child there, not to support cities, but to support some invasive fish.
        http://wsoweb.ladwp.com/Aqueduct/historyoflaa/

    • Ugh, the Central Valley is Man-Made…
      IN some respects… spreading the water across California for Human Use allows for more rain, more moisture to be in the Air all across the USA… rather than letting it all flow through rivers into the ocean..

      • That was my thought. Without human interference don’t most of those sources simply flow on though to some exit point like the ocean? Agriculture in central Arizona depends in large part on capturing river water that would otherwise just flow on through. Rivers are drier and surrounding land is wetter. Much of the river water would end up flowing through Mexico and into the ocean. I’m assuming pretty much the same thing is happening on a larger scale in California.

  3. Meanwhile, speaking of breaking a bad drought, the Winter 2014-15 hoped for El Nino is going, going, going….
    Monday’s (Oct 13, 2014) NOAA CPC ENSO Weekly reduced the El Nino 2014-15 probability from 65%-60% (last week) to merely “favored”.
    This week’s wording: “El Niño is favored to begin in the next 1-2 months and last into the Northern
    Hemisphere spring 2015.”
    I assume “favored is something slightly over 50%?
    Hopefully Cal can get some desperately needed rain anyway from the warmer fingers of water from the failing El Nino-wannabe

  4. Does it seem to anyone else that conventional, mainstream sources of work like NASA are producing patchwork studies that contradict locally – without GLOBALLY contradicting, the CAGW narrative that today is the worst it has been since 1850, and nothing has any parallels worth considering ….
    Next year, a list of peer-reviewed, establishment counter-Gore-Oreskes-Conway-Hansen papers is going to be considerable …. perhaps enough to get the MSM`s attention.

    • Doug,
      Don’t you know the science is settled? That is why climate research is not being funded because we know everything we need to know.
      Hold, on wait a sec……

  5. driven by severe precipitation deficits downwind from regions of major dust storm activity
    OK, I’m confused. Don’t you need severe precipitation deficits FIRST in order to CREATE the regions of major dust storm activity?

    • Yeah, I’m with you in that… This explanation  just does not sound logical.
      Dust clouds reflect sunlight and block solar energy from reaching the surface. That prevents evaporation that would otherwise help form rain clouds, meaning that the presence of the dust clouds themselves leads to less rain, Cook said.

    • I am no expert in this area, either, but I think they are talking about the acceleration in a downward spiral–lack of enough rain causes dust in the dry part of the year that carries over into what should be the rainy season which causes less rain which causes more dust which causes less rain which….
      Think positive feedback in an auditorium sound system.

      • The water that forms the rains that fall mainly on the plains does not first evaporate from the plains to form those rains.
        H2O vapor in the air “goes with the flow”, …… the flow of the winds that is. And very little to none of it forms raindrops that fall back upon the same ground from which it evaporated from. Except in the case of an extremely large Low Pressure area with a “circular” wind pattern.

    • Actually, dust storms were caused by the plowing up of millions of acres of thousands of years old buffalo grass roots which held the soil down. This was due to the price of wheat being high , and later on in this period, supported by the government. Also, prior and initial years of above average rainfall encouraged the wheat farming when there was a dirth of that commodity and then the dryer years came. Whether the duststorms exacerbated the drought, I do not know. That part of the US was then, and is now, windy and loose soil will blow. As the price of wheat fell more and more acres were needed to make the same money so more and more were plowed. Less rain meant less yield and more and more acres were plowed. The wind kept blowing. Read “The Worst Hard Time”.

      • I realize that your comment is a favorite by CAGW people. I also think that this article put out by the government is a red herring. Spain had colonized some islands off the coast of Africa. On one these a house had been built on top of a hill looking west. Columbus was there and much to his surprise, he saw dust coming from the wrong direction. It wasn’t blowing off the Sahara. That’s why he was certain that if he sailed west, he’d find land. I disagree with their findings. For dust to blow that far, there had to be a lot of it. It may matter somewhat whether the land is plowed or not, but 10 years of drought vegetation becomes non existent

      • In a nutshell, land was cultivated too far west and thus unsuitable for cultivation because of the dryness and tendency to drought. Native grasses could endure drought but these were plowed under and so there was nothing to hold the soil.

    • I have experienced dust storms in Aussie droughts and I can assure you that the dust doesn’t hang around to supress rainfall. What evaporation would you get from a bone dry environment? Our droughts are always caused by large weather cycles that build up over many months and have to resolve naturally. Farming practises may exacerbate the local physical conditions of a drought but they have little influence on the rainfall deficiencies.

      • Some sort of similar objection crossed my mind as well. The idea of dust having a “cooling effect” and “suppressing rainfall” doesn’t jive with the reports of 110 degree heat, from the people suffering in Oklahoma and Nebraska.
        On the other hand, the settlers were uneducated about how to farm under dry conditions. When I wandered out west I myself was amazed how deeply the Navajo and Hopi planted their corn. The corn in my small Arizona garden withered because I planted my kernels at a depth that suited New England. If the Hopi planted corn as deeply as they do in Arizona in New England, the seed surely would rot.
        One quaint idea those settlers had was that “farms bring rain.” It was as if they felt they could not only “civilize” the landscape, but even the weather. They learned the hard way this wasn’t the case.

    • Exactly what I was thinking. I’m sure that data will immediately start to be homogenized just like temp data. It’s only a matter of time that anything that happened in the 30’s doesn’t come close to “how bad it is now”!!!

      • Fortunately an effort was made to interview the old farmers who lived through the Dust Bowl, before they passed away. One thing that comes across is how terrible the heat was. Over 110 degrees was common.
        One old Kansas farmer told me the dust created static electricity that was so bad that farmers drove with a chain dragging behind their cars, to ground the car, for otherwise the static electricity caused the spark-plugs to malfunction.
        In this one case the old-timers were not telling one of those walked-both-ways-uphill tales, when they described how bad it was. Hansen, on the other hand, was stretching things when he said 1998 was worse.

  6. I can see the severe dust storms of 1934 having an anthropogenic component due to poor soil management, but the blocking high that initiated the drought was caused by …. ?

    • I’ll say it… Cthulhu.
      Because that makes more sense than 1 additional part per 10,000 of a trace gas.

  7. Still, agricultural producers need to pay attention to the changing climate and adapt accordingly, not forgetting the lessons of the past, said Seager. “The risk of severe mid-continental droughts is expected to go up over time, not down,” he said.
    Do tell…. Why? Why is it expected to go up over time?

  8. According to the recent Fifth Assessment Report of the Intergovernmental Panel on Climate Change, or IPCC, climate change is likely to make droughts in North America worse, and the southwest in particular is expected to become significantly drier as are summers in the central plains.

    Yet in AR4 the IPCC report it saw reality and referenced studies indicating that mega-droughts / severe drought in the US west was likely to remain a feature of the climate for the rest of this century.

    IPCC AR4
    IPCC Fourth Assessment Report: Climate Change 2007
    Multiple proxies, including tree rings, sediments, historical documents and lake sediment records make it clear that the past 2 kyr included periods with more frequent, longer and/or geographically more extensive droughts in North America than during the 20th century (Stahle and Cleaveland, 1992; Stahle et al., 1998; Woodhouse and Overpeck, 1998; Forman et al., 2001; Cook et al., 2004b; Hodell et al., 2005; MacDonald and Case, 2005). Past droughts, including decadal-length ‘megadroughts’ (Woodhouse and Overpeck, 1998), are most likely due to extended periods of anomalous SST (Hoerling and Kumar, 2003; Schubert et al., 2004; MacDonald and Case, 2005; Seager et al., 2005), but remain difficult to simulate with coupled ocean-atmosphere models. Thus, the palaeoclimatic record suggests that multi-year, decadal and even centennial-scale drier periods are likely to remain a feature of future North American climate, particularly in the area west of the Mississippi River.

    Here is something more recent.

    Abstract – 2011
    David W. Stahle et al
    Tree-ring data document 16th century megadrought over North America
    …….Droughts during the 1750s, 1820s, and 1850s–1860s estimated from tree rings were similar to the 1950s drought in terms of magnitude, persistence, and spatial coverage, but these earlier episodes do not appear to have surpassed the severity or extent of the Dust Bowl drought. However, longer tree-ring reconstructions of PDSI for the United States and precipitation for northwestern Mexico and western Canada indicate that the “megadrought” of the 16th century far exceeded any drought of the 20th century (Figure 1) [also see Wood-house and Overpeck, 1998], and is considered to be the most severe prolonged drought over much of North America for at least the last 500 years [Meko et al., 1995].
    http://onlinelibrary.wiley.com/doi/10.1029/00EO00076/abstract

    Since we have come out of the ‘hottest decade ever’ with unprecedented global warming you have to wonder why globally there has been……….

    Letter To Nature – 11 September 2012
    Justin Sheffield et al
    Little change in global drought over the past 60 years
    …….Previous assessments of historic changes in drought over the late twentieth and early twenty-first centuries indicate that this may already be happening globally. In particular, calculations of the Palmer Drought Severity Index (PDSI) show a decrease in moisture globally since the 1970s with a commensurate increase in the area in drought that is attributed, in part, to global warming4, 5……..Here we show that the previously reported increase in global drought is overestimated because the PDSI uses a simplified model of potential evaporation7 that responds only to changes in temperature and thus responds incorrectly to global warming in recent decades. More realistic calculations, based on the underlying physical principles8 that take into account changes in available energy, humidity and wind speed, suggest that there has been little change in drought over the past 60 years. The results have implications for how we interpret the impact of global warming on the hydrological cycle and its extremes, and may help to explain why palaeoclimate drought reconstructions based on tree-ring data diverge from the PDSI-based drought record in recent years9, 10.
    http://www.nature.com/nature/journal/v491/n7424/full/nature11575.html

  9. Good to see a sane scientific paper putting it all into sensible proportion. Have just read the latest (October) issue of “National Geographic”. They have been quite “alarmist” over the years (remember water lapping half way up the Liberty Statue). But here we read a very interesting, informative article on the present Californian drought – and never a word about CO2 or human evil-doing. All it says is that this drought approaches “historical levels”. Have they seen the light at “National Geographic” ?? Are the wheels finally beginning to fall off the climate panic wagon?

  10. I may have missed something so my advanced apologies.
    The NASA abstract says nothing about man-made climate change. The press release includes the IPCC’s speculation about FUTURE US droughts ‘likely’ to be worse in future due to GHGs. The rest of the press release does not say anything about man-made greenhouse gases. Why did NASA include the IPCCs assertion?

  11. Ya know, when the California drought is over, will they blame man for the fact that it’s over? See Great Lakes temperature and water levels, see also Australia’s past ‘permanent drought’!!!
    It’s just the weather and not the climate.

  12. EUREKA! 1934
    The introduction of the V8 automobile AND Michael Mann’s Birthday – coincidence? You be the judge…

  13. No, it’s worse than we thought! :

    Extreme” is the word for the weather Australia has experienced recently: droughts fires and even floods so big the world’s oceans lowered. Climate models tell us all this will get worse, especially if we fail to take strong action now.

    Dang, who new climate models could tell us anything!!
    http://view.e.newscientist.com/?j=fea115707064007c76&m=fe9b12717165057877&ls=fe2a1775716c077c751178&l=febf15797c6d0479&s=fe561171766d02757216&jb=ff941679&ju=fe5617707c65037b721c&&r=0

    • “Who knew climate models could tell us anything”
      What? They tell us everything! You just have to know how to interpret the results…

  14. It may be time to remind our erstwhile NASA academics that The USA is only 6.6% of the world land area. 1.9% of the total surface of the Globe and that 71.9% of the western half of that area is about the equivalent of a single footprint in Times Square. The continent of Australia is as big as continental USA. It is WEATHER not climate.

  15. Where ever Prairie grass grew i would imagine is ripe for potential of a drought. When this grass can flower during one you know that it has specially adapted to its environment.

  16. The dust carried the effects of drought farther than it would otherwise have gone. As a farmer I call this basic logic. Good solid article, in my opinion

  17. Where did they get trees going back a 1000 years on a prairie? I thought the Central Plains were prairie for more than 1000 years.

      • “Yamal?”
        That’s kinda what I was thinking, Paul :o)
        Of course there are some serious answers to my question – trees along the drainage creeks, e.g. – but did they get broadly spaced representative samples or did they sample the only stump they could find for miles around?

    • Maybe from cottonwoods or other riverine species along watercourses. But then, they have access to water even in drought years.
      Or ponderosa pine, Black Hills spruce, quaking aspen, paper birch, bur oak & green ash in the Black Hills or Rockies.

      • I was not here then and don’t know anybody that was, but I have heard rumors that there were lots of trees until the sod-busters starting building houses, and the rail roads started using trees for sleepers and for fuel.
        I can see how that might be, but it seems like (as mentioned) they would grow along water-ways where between the flows and the aquifer they would have water in the dry years.

  18. Droughts and extreme weather in 1929-
    http://trove.nla.gov.au/ndp/del/article/138537700?searchTerm=world%20droughts&searchLimits=
    ‘The world’s weather has been
    specialising in droughts,’ . says Dr.
    E; E. Free in the New York ‘Times.’
    ‘Over the eastern two-thirds of the
    United States damage is estimated….
    ‘Great Britain has been similarly
    parched. Not only has agriculture-.
    : been damaged ‘ severely, but the
    water supplies of many towns and
    , villages: .have failed
    From the other side of
    the world, in South China, come re–
    ports of droughts, with.
    famine threatened and suffering al
    ready acute.
    Early in July tor
    rential floods swept Eastern India,
    and Coehii*4/hiiia, : with stories of
    hundreds of elephants floating help.
    lessly to drown.
    ‘Droughts, crop failures and for
    est fires are reported from Europe,
    from the West Indies, from Australia
    and elsewhere in the Southern Hemis-
    sphere. India and South Africa re
    port the severest hailstorms there on
    record. In yugoslavia, in the early
    months of the year oyer 100 people^
    were killed by lightning.’
    ‘During ‘ January and February of ,
    last – winter : Europe – experienced the
    greatest cold’ ill’ over two centuries.
    Trains were snowbound for two
    weeks in the Balkans; Rome was.
    snow-covered,. and ice-crusts formed
    on Venetian canals. wolves
    appeared in villages -in yugoslavia, ,
    Hungary and Spain. ‘The Flame of.
    Remembrance in’ Paris,’ intended to
    be eternal, went out because the gas
    frose up
    The registrar-general
    ascribed more than 60,000 ? extra
    deaths in England to the weather, i
    India and South Africa re
    port the severest hailstorms there on
    record”

  19. “Dust clouds reflect sunlight and block solar energy from reaching the surface. That prevents evaporation that would otherwise help form rain clouds, meaning that the presence of the dust clouds themselves leads to less rain”, Cook said.
    Of Course: the lack of solar energy is the reason for all the record high temperatures in 1934. Sarc

  20. The global warmist alarmists are like the BORG ( Star trek). Every climate scenario gets assimilated into AGW .
    As the climate cools over the next 20 years or so – the new story line-
    “Frosts like the ones that caused so much damage to crops this season could be more common for the next 20 years, according to scientists.
    They say greenhouse gases in the atmosphere were changing the way high pressure systems formed and moved, causing severe frost problems for farmers”

  21. Still, agricultural producers need to pay attention to the changing climate and adapt accordingly, not forgetting the lessons of the past, said Seager. “The risk of severe mid-continental droughts is expected to go up over time, not down,” he said.

    What “changing climate” is he nattering about? And why exactly would the risk of severe droughts be expected to increase? These “scientists” remind me of so many clucking hens, mindlessly warning about the future, with no solid scientific basis whatsoever.

  22. Acknowledged that 1934 was bad, but how do they maintain that it was the worst “in 1,000 years”? What about the tree ring evidence that shows a 50-60 year drought in the late 12th century across most of the southwest, the one that wiped out the Anasazi civilization which was thriving up to that point? How could one bad year be worse than that one?
    (an event like that today would completely wipe out 5 or 6 states, at least)

    • Echoed!
      I’m on your side questioning the claims for the 30’s being the worst western drought in a thousand years.
      Their claimed findings seem a little too pat which makes me suspect this is a softening up preliminary for a follow-on paper claiming anthropogenic causes.

    • Same goes for California, which suffered a 200-year megadrought from the 9th to 12th centuries. In the Sierra Nevadas near Tahoe lies Fallen Leaf Lake, where Stanford’s Sierra Camp is located. During the Medieval megadrought, trees grew on the newly exposed shoreline of the lake. Then, as Fallen Leaf expanded once again, the trees were preserved under cold water.

  23. reality of physics also means that was the hottest year because water in the air/ground modifies the temperature extremes(see deserts if you disagree)…….a very dry year would also be a hot year in summer because the dry air both heats and cools much easier than wet air…………IF another made this point i am sorry i didnt read the thread before posting.

  24. @ferdberple 10/14at 9:06 pm
    It is just possible that Science doesn’t actually know what the “normal range of variability” is? And thus continues to see everything caused by nature as “abnormal”?
    Yes. It is the crux of the “Black Swan”. Nature does not have a Normal Distribution when it comes to events, yet so many people try to fit it to one. Log-Normal may be closer to the mark, but I suspect insufficient sampling and claims of outliers is a strong hint that whatever distribution is chosen, its kurtosis (4th moment) of the chosen distribution is habitually lower than the sample leading to the real possibility that the chosen distribution is narrower than it ought to be. But tests of kurtosis may (of necessity) be unable to reject a non-normal kurtosis without raising red flags.
    Rather than stating that the sample doesn’t fail non-normal-kurtosis tests at 95% confidence (assuming kurtosis was tested at all), one should be up front and say the sampled kurtosis std error is at the 77th percentile expected for that distribution, giving the reader the hint that kurtosis is an unresolved issue when it comes to confidence limits.

  25. I find this claim to be a highly questionable claim. By saying this they are claiming that they have the same resolution for determining the PDSI 1,000 ago than they did in 1934. That’s absurd. What is the error of their PDSI value for the year 1200 based on tree rings? Ask Mikey Mann, these tree rings could just be showing changes in temperature instead (sarc).
    Furthermore, drought in an individual year is not important for climate interpretations. Consecutive years of moderate drought are much more impactful than a single year with extreme drought.
    Long-term aridity changes in the western United States
    ER Cook, CA Woodhouse, CM Eakin, DM Meko… – Science, 2004 – sciencemag.org
    http://www.kgs.ku.edu/Publications/PIC/pic35.html

  26. I was extant during the 39-40 edition (4 droughts in succession from 1931) and I’m amazed that that history has been largely ignored when they talk about temperatures and droughts today. There was also a black snot and shirt collar drought in the early 50s, too which I know from memory.
    Something that doesn’t compute is, what has California got to do with it. Didn’t those whose topsoil blew away in West Central US and prairies in Canada head for California to pick fruit?

  27. Hello, we need to keep on spreading the word that the effects of CO2 are logerithmic. Therefore the more there is the less the effect.
    Hence CO2 cannot be a factor in the usual nonsence said about the climate come weather.
    The warmers keep on trotting out the same lies, and the politicians who are either stupid, or see votes in it, or both, appear to go along with it.
    President Obama is a good example of this, is he stupid, I don’t think so, then he is in it for what he can get out of it, whatever that is ?
    Dr. Goebbels said it all way back in the 1930’s. Tell a lie often enough and it will become the truth.
    Michael Elliott.

  28. The study’s conclusion appears to conflict with NOAA’s assessment that the most severe North American drought of the past 500 years occurred in the late 16th century:
    “Longer records show strong evidence for a drought that appears to have been more severe in some areas of central North America than anything we have experienced in the 20th century, including the 1930s drought. Tree-ring records from around North America document episodes of severe drought during the last half of the 16th century. Drought is reconstructed as far east as Jamestown, Virginia, where tree rings reflect several extended periods of drought that coincided with the disappearance of the Roanoke Colonists, and difficult times for the Jamestown colony. These droughts were extremely severe and lasted for three to six years, a long time for such severe drought conditions to persist in this region of North America. Coincident droughts, or the same droughts, are apparent in tree-ring records from Mexico to British Columbia, and from California to the East Coast.”
    Here’s the link: http://www.ncdc.noaa.gov/paleo/drought/drght_500years.html
    NOAA also contends that “When records of drought for the last two millennia are examined, the major 20th century droughts appear to be relatively mild in comparison with other droughts that occurred within this time frame. Even the 16th century drought appears to be fairly modest, when compared to some early periods of drought.” Link: http://www.ncdc.noaa.gov/paleo/drought/drght_2000years.html
    Has anyone read the Cook, Seager, Smeardon study? Do they discuss NOAA’s assessments?

  29. 1934 may have been the driest year for the central plains but it is widely acknowledged that the worst drought year for the northern plains that extend into Canada was 1937. That year there was little rain and complete crop failure was common across the Canadian Prairie. At the 1000 acre University of Saskatchewan Research farm the total feed harvested consisted of 200 tons of Russian Thistles.

  30. I can hear you asking, so how dry was it?
    Canadian Prairie wheat yields in 1934 averaged 11.3 bu/acre. In 1937 they were 6.4 bu/acre.
    In 1934 the Prairie provinces produced 172 million bushels of wheat or 4.68 million tonnes.
    In 1937 142.5 million bushels of wheat were grown or 3.86 million tonnes.
    Wheat exports of 95.5 million bushels for the 37/38 marketing year were half of the 36/37 marketing year.

  31. milodonharlani
    October 15, 2014 at 10:21 am (replying to bonanzapilot above)

    Same goes for California, which suffered a 200-year megadrought from the 9th to 12th centuries. In the Sierra Nevadas near Tahoe lies Fallen Leaf Lake, where Stanford’s Sierra Camp is located. During the Medieval megadrought, trees grew on the newly exposed shoreline of the lake. Then, as Fallen Leaf expanded once again, the trees were preserved under cold water.

    The greater “devil behind the details” lies within the curves in the “too wet” years shown in the graph above.
    The Colorado River flow that was used to “regulate”” the water going to California, Los Angeles, NV and AZ from the Hoover Dam was measured between 1915 (the maximum wettest point of a record-setting wet period!) through 1919 (a year almost as “wet” as 1915!).
    So, when the Hoover Dam was approved and the water rights signed off by everybody concerned in the 1928-1932 time frame negotiations, TOO MUCH WATER was being predicted for every year in the future. And, of course, now they are not able to meet the contracts for water and power that are “per regulation” because the regulations are too optimistic about water available.
    And no politician can admit now that CA or LA or NV or CO or AZ or anybody else must give up “their” water to somebody else’s state or city. $$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$$$$$$$$ $$$$$$$$$$$$$$$$$

  32. I’m afraid we can’t control the weather, climate nor other natural cycles. All these AGW’s should have learned that by now. Pollution yes, something can be done about that. But it costs, particularly in the case of coal surface fires.

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