Wednesday, January 22, 2014

Wednesday Search Challenge (1/22/14): How common are droughts in California?

Aerial photo of California hillside.  Winter vs. summer.
A composite aerial view of a California hillside contrasting a normal
winter view (green) and a normal summer view (blonde).  

We know California is in a drought now.  And yes, it’s pretty bad and looks like it's going to get worse for the foreseeable future.  

But can we find out the larger historical context?  How often does a drought happen, really?  We know that weather records have been kept (relatively accurately) since the mid-1800s.  What about before then?  How common (or rare) are droughts in California in the long-run?  

Today's Search Challenge is an interesting one, because it asks a question you might not think was possible to answer via web searches.  
1.  Can you find a record of the rainfall in California for the past two thousand years? And what does that tell us about the relative frequency of drought?    
In other words, if you CAN find some way to track that rain back into deep history, how often do droughts take place?  And how long do they last?

Should we really be worried?   Is this just a temporary thing that will be gone soon?  Or is this a vision of a future to come? 

Search on, dryly!  

A photo taken on the ground near the site pictured above (on Jan 19, 2014).
All this should be green. It shouldn't look like summertime yet!


  1. Good one Dan I thought of this immediately and it worked producing dozens of hits SEARCH |dendrochronology california drought|
    Californians should be worried, very worried. There have real droughts in the past lasting 150 to 200+ years. From the NYT article "the vast majority of years during the past 3,500 years have been much drier than what we've come to expect to be normal in California."
    Prediction is difficult especially the future but it seems CA might be entering a mega drought



  2. I used the “Black Menu for Google”- searched Trends and Google Public Data Explorer.
    Query [weather OR meterology OR drought] - no results.
    So my searching focused around finding sites that could provide links. Keeping in mind I’m not looking for direct hits but rather looking for keywords related to historical weather and historical databases.

    Query [california drought history]
    Dr Jeff Master’s Wunderground history to 1895

    Results provided a link to Weather Historian Christopher Burt who wrote Extreme Weather A Guide and Record Book. No preview but gave me the idea to use following query-

    Query [Extreme Weather "california " drought OR historical]

    First Result U.S. Geological Water Survey Department of Water Resources gave me a lead to search U.S. Geological Survey Water.
    Query [U.S. Geological Survey Water]
    Result Water Resources of the United States: U.S. Geological Survey

    This provided a link to the 2001 Newsletter discussing historical climate.A newsletter good insight into how data was collected and a summary of findings going back thousands of years.
    “Interagency Ecological Program for the San Francisco Estuary”

    “used new precipitation-sensitive tree-ring reconstructions, each over 1,000 years long, from around the West to show long-term droughts in exquisite detail…

    Ominously, several of the climate reconstructions presented showed that the 20th century has yielded fewer droughts in California than in previous centuries…

    Overall, the intercomparisons of paleoclimate reconstructions presented at the workshop suggest epic droughts (decades and centuries long) did afflict central California during the last several millennia, including, in particular, the medieval droughts. The drought periods
    were vastly longer than we have experienced, but not necessarily more severe than historical.” droughts….

    As a result, our ability to predict the recurrence of such disasters is minimal. We can, however, advise that such events have happened before and thus may happen again.”

    1. I'll get it right - here's the link to the Newsletter.

    2. RM - that's a very interesting source, thought the summary was good - also thanks for the point - looks like a handy tool.
      hydro forests Tahoe,Tenaya, Mono, Fallen Leaf Lakes, Walker River
      NSF, bristlecone slideshow
      Malcolm Hughes, Lab of Tree-Ring Research, UofAZ
      Tahoe drying trends more than 2000+
      20' below current levels…
      the CO/4 Corners mention is intriguing too:
      "For example, Larry Benson (USGS, Boulder, Colo.)

      reported that major oscillations in the water balance of

      Pyramid Lake have occurred irregularly but, on average,

      about every 150 years during the last 8,000 years. Among

      the paleodroughts that affected the lake were the medieval

      epic droughts inferred elsewhere in the Sierra Nevada. A

      major relocation of Anasazi populations in the Four

      Corners region occurred in the middle of the second of

      these prolonged droughty periods, which took place in the


  3. Just as an after thought regarding the newsletter that mentions the "Bristolcone Pine" tree which was used to collect data from its tree rings and than later they used other more precipitation sensitive trees. I looked into the Bristolcone years ago because we have a few on our property. They were planted by the previous owners as were several other unusual trees. The Bristolcone Pine is considered the oldest tree on the planet with references back 5000 years ago. I like to think ours is a species related.

    1. If you didn't know the term dendrochronology which I'm guessing most did not, you could have gone to and searched 'tree rings for aging' and first hit is dendrochronology then define = "the science or technique of dating events, environmental change, and archaeological artifacts by using the characteristic patterns of annual growth rings in timber and tree trunks."

  4. Good Morning, Dr. Russell, fellow SearchResearchers

    I haven't found an answer yet. However, maybe some of the searches that I did can help others to find the answer.


    [California rainfall 2000 year to date]

    [California rainfall since before Christ]

    [weather science foundation]

    [California rainfall since year 0]
    2013 was the driest year since the state started measuring rainfall in 1849.


    [California rainfall first records]

    [California rainfall precipitation deep history]

    [California rainfall first century] Tried to go from that date to the data searched.

    [California drought first century]

    [California drought first millennium database]


    1. Can you find a record of the rainfall in California for the past two thousand years? And what does that tell us about the relative frequency of drought?
    A: Not yet an answer

  5. [ california historical rainfall data ]
    [ california historical rainfall data filtetype:xls ]
    My brain jumped to the fact that we already had a challenge once about weather data so I used the Search the SearchResearch Blog box [ rainfall ]
    Answer: How much does it rain in Northern California?
    Datasets from that answer just don't go back far enough.
    Brain jump to [ california drought data trees ] knowing that we teach students about what information can be gleaned from tree rings and that California has really old trees (petrified even).
    Tree-Ring Data Show History, Pattern to Droughts
    There I learned about [ Palmer drought severity index ] to Palmer Drought Index
    [ California Palmer drought index data ]
    [california "2000 years" drought data ] I used the quotes to see if something was published with 2000 years of data and filter things only published in the 2000 or with the year 2000 as a data point.
    North American Drought: A Paleo Perspective to The Last 2,000 Years Tried following links to several data sets and visualizations but got to many things I couldn't make sense of and dead links.
    This paper keeps coming up in the SERP and citations 2000
    Years of Drought Variability in the Central United States
    like here A 1,200-year perspective of 21st century drought in southwestern North America
    This page showed up in the SERP California
    governor proclaims state in a drought
    matching 2000 years of data but after looking at the the links mentioned by commenter CY I move on.
    [ california tree-ring precipitation data ] to Tree-Ring Chronologies and try a few searches in the International Tree-Ring Data Bank (ITRDB) on NOAA but realize I'm over my head. Follow a link to Paleoclimatology Datasets
    Looked at Lake Datasets but then headed back to Google with the new term I'd learned to see if I couldn't have better luck [ paleoclimatology california precipitation data ] with the top hit going back to NOAA. Climate Reconstruction I explored the expanded sections for North America but still didn't find anything that made sense to me to be California.
    Google Scholar search [ "california precipitation" "2000 years" data ] to lots of hits but now my browser is just crawling along with so many tabs.

    Figure I would document my path so far, close my tabs and take a break. No answer yet. I feel like I'm dancing around it just not making a breakthrough.

    1. Hi RoseMary, Fred and everyone.

      I was just thinking about the SearchResearch Challenge. Maybe I understand it wrong and Dr. Russell is looking for other "data". So, I tried looking for stuff like you (Fred) and Rosemary did.

      Archaeological perspectives on the effects of medieval drought in
      prehistoric California
      "...prehistoric agriculturalists would have
      been highly susceptible to prolonged decreases in rainfall
      owing to their heavy reliance on crops. Absent tree-ring
      dating..." Droughts during

      [California Millenium-scale rainfall | precipitation]
      Blue Oaks Shine New Light on California’s Past Climate

      NCAR: How much rain fell on the Front Range, and how historic was it?

      [California prehistoric drought milleniums data intext:rainfall]
      [California Rainfall dendrochronology] Precipitation records in California tree rings

      [paleoclimatology california precipitation]
      Climate reconstruction

      I'll try to find answer again later.

  6. thought this was a good source site, although I didn't find the specific answer yet -
    The Encyclopedia of Earth

    as cited by others, Cook: Medieval Megadroughts in the Western United States goes back to ~ 800 AD with tree ring studies
    (⌘-F () for illustrations & maps - ctrl-F (pc))
    turns up here: eoearth
    "The timing of the A.D. 900-1300 period of elevated aridity is especially worrisome because it occurred during what has historically been referred to as the ‘Medieval Warm Period’ (MWP; Lamb, 1965), a time of persistently above-average warmth over large parts of the Northern Hemisphere (Esper et al., 2002), including the Western United States (LaMarche, 1974). Stine (1994) also noted the association of his prolonged Sierra Nevada droughts with the MWP."
    found the search filters on the site interesting: on site search filters

    found eoearth when I saw a mention of the "Callendar effect" and eoe was on the serp page. GSC

    like Fred, had run across the term [paleoclimatology] and used it along with [north american continent] in a number of combinations to look for info… since
    CA, as a state, only runs back a 164 years (as of 9/9, this year)… maybe it is a state of mind thing and the defined terra is just trying to match the Governor — Brown…
    "ba-dum-DUM" or "ba-dum-TSH" rim shot

    NOAA data 2000
    1500 years
    Columbia University
    long term changes graph
    perhaps there will be another "March Miracle"… but I'm probably all wet…

  7. Good points Ramon. Fred and Ramon have done a good search and your steps are very helpful for us. Went back Query [california paleoclimatic data "drought"]

    Result - and links to NOAA Paleoclimatology -

    I have found another document that includes data going back. "2000 Years of Drought Variability

    in the Central United States" Refer to Fig 10 chart that covers Paleoclimatic Records of the Great Plains and western USA back 2000 years.

    Here's the shared link -

  8. I started working on this later in the evening so a little too tired to concentrate. I started by searching historical rainfall data california but results didn't go back far enough. Realized that 2000 years ago but us at around the time of christ so add that term into the search query. That was a huge mistake! Way too many religious interpretations of global warming and why it wasn't happening. I should have realized I would get too many religious connotations using the word Christ. So then realizing that this put me at around 1 AD I used that in the query and it actually yielded a very interesting result. A link to an article entitled "Archaeological perspectives on the effects of medieval drought in prehistoric California" Lots of very interesting information regarding the climate of California over thousands of years. My actual search query that yielded this was california climate year "1 ad" I had planned on using the term prehistoric instead of 1 AD but then added in the year instead. Too tired to do anymore. I have been shoveling 14" of snow!

  9. Not sure if I put things here or on the next post as a continuation. I'm picking here just for a smoother follow-through.
    Failed searches today included
    ["california" paleoclimate droughts chart ]
    [ Dr. Scott Stine, a paleoclimatologist at California State University ] and [ Dr. Scott Stine, a paleoclimatologist at California State University data ]
    Explored more of TreeFlow
    Besides searching for articles by Dr. Stine [ Swetnam, T.W. 1993. Fire history and climate change in giant sequoia groves. Science 262: 885-889 ]
    [filetype:pdf "Fire History and Climate Change in Giant Sequoia Groves" ]
    Clicked on almst every link here Paleoclimatology
    [ dendroclimatology california drought chart OR table ] took me to a KQED article Decoding California’s Drought History
    Following links once again to the NOAA website I found myself here North American Drought Atlas PDSI Reconstructions, Cook et al.(2004)- Time Series Plots. Trying that tool didn't seem to work. I clicked on the link for Drought Atlas

    Click Select Grid-Point ( I clicked on a dot that looked to be near San Francisco). I at least get chart for the past 2000 years.

    I did notice that remmij had links to the same lab at Columbia.

    1. This comment has been removed by the author.

    2. This comment has been removed by the author.

    3. I noticed I needed to finish somethings up for the answer. Using the Drought Atlas I was able to get this PDF Image. I wanted a clarification of what it was showing me so did [ pdsi scale ] to Climate of 2013 - April U.S. Palmer Drought Indices that has a brief explanation of the indices at the bottom.

      Based on the -8 being EXTREME drought periods and seeing that in the last 2000 years there have been a couple times that were near -8 on the scale and even some periods in the last few hundred years around -6, but then as we get toward the year 2000 the lines don't drop down nearly that far, I think that western coast has and will see much worse drought periods.

    4. Fred, followed some of your terminology and found these - more short term than 2000 years, but may ease some anxiety a bit… a voice from a desert…
      may be some chickenlittleitis
      Dan's area - lacking data
      UN - Lincoln, not East side
      AMS Palmer
      Palmer Drought Index

  10. I started like others with the general CA Rainfall, which led to the term Paleoclimate and more searching which uncovered a link to the paper "Extreme Late Holocene Climate Change in Coastal Southern California" -
    That document referenced Stine's Sierran droughts. A search for Stine's work led to a summary published in Sierra Nature Notes -
    of work by Scott Stine, Ph.D, CA State University, Hayward, and this rather long excerpt :
    “Evidence too detailed to discuss here indicates that the Medieval droughts of the Sierra were the most severe of the past 4000 to 7000 years. This is not to say, however, that other dry spells are absent from the record. Persistent droughts, moderate by Medieval standards but strident relative to our "normal" conditions of the past 150 years, drew lakes and rivers well below their modern levels on numerous occasions during the past two millennia, most recently during the late 18th and early 19th centuries. Indeed, increasing evidence indicates that there is little that is climatically "normal" about the past century - and- a-half; it appears, in fact, to be California’s third- or fourth-wettest century-scale period of the past four or more millennia.
    Since statehood, Californians have been living in the best of climatic times. And we’ve taken advantage of these best of times by building the most colossal urban and agricultural infrastructure in the entire world, all dependent on huge amounts of water, and all based on the assumption that runoff from the Sierra Nevada will continue as it has during the past 150 years. Yet even in these best of times we have run out of surplus water, and we fight over allocation.
    Drier times undoubtedly lie ahead. These may be anthropogenically induced, as we turn our atmosphere into an artifact. But with or without human inducement, episodic droughts, severe and persistent, will return, just as they have in the past. Such drought will take a severe toll on our infrastructures and institutions.”

    Still looking for actual charts!

  11. Sorry I deleted 2 posts. I made some changes because chrome extension showed that some Url can be not safe.

    ["severe drought" california millenium-scale chart ]

    California’s drought situation in pictures – what a difference one year makes

    Same query in Images.

    Mega droughts

    Skeptical Science Page so big that I can not use Ctrl F to find data

    [rainfall california site:]

    Finally a chart :

    Searched the source of the chart.

    [North American Drought: A Paleo Perspective] Site was already posted by Fred and RoseMary and in this part of site comes the chart.

    Reading charts and for what pages and site mentions: Situation is serious and maybe if everything goes normal, then 2014 or 2015 will be better.

    I think that our planet needs to be helped and make better use of the resources. In the challenge found new ways to produce rain but we all need to do more not just in California.

    I already want to see how Dr. Russell found the answer.

    1. Ramón, using your NOAA link, found a couple other other methods of trying to construct a drought record…
      from work done in North Dakota and Belize, but the applicability to a specific region like coastal California is unclear.
      Still, finding things like speleothems is interesting.
      radiometric dating
      PALEO Journal links

      "We believe that the diatom-inferred salinity record from
      Moon Lake is a good proxy for drought intensity, duration,
      and frequency over the past 2,300 years because
      of the highly significant correlation between salinity and
      drought occurrence over the past 100 years"

      an alternative measure to the tree rings -
      Moon Lake, ND
      NOAA - Moon
      NOAA datasets
      NOAA data
      Tree Ring Search Engine
      paleo simple search: Yok Balum Cave, Belize 2000 Year Stalagmite Stable Isotope Data

  12. After searching for more than an hour yesterday I ended stuck on the NOAA site on the paleoclimatology page ( following many links and not finding. (the PAGE 2k site raised high hopes…)

    I started today with another angle : drought rather than rainfall.

    I did [paleoclimatology drought data] ('data' seem vague enough not to assert a certain type of result, let's see)

    The first scholar result gives North American droughts of the last millennium from a …, followed the link to a pdf and started to peruse "North American Droughts of the Last Millennium from a Gridded Network of Tree-Ring Data".

    On page 2 it says "In this paper, using the recent “North American Drought Atlas” of Cook and Krusic (2004)…", so : [North American Drought Atlas] gives as first result on the SERP : TREE-RING RECONSTRUCTED PDSI DROUGHT, it looks promising. And indeed the site ( gives an historical reconstructed value of the "Palmer Drought Severity Index" for the last 2000 years in North America.
    You can even see an animation of the evolution of the index.

    Data are available for download and one can imagine averaging the data corresponding to California, leading to a global time serie for the pdsi in that state, covering the last 2000 years. But that's far beyond the time I've got!

    That's where I am as for today and I'm not sure I could do a better job.

    (Learning that the PDSI is based on temperature and precipitation I thought that the data for these variables must be available in some way to compute the PDSI over 2000 years, but this was a mistake, the past PDSI is infered via dendrochronolgy from the recent calculated PDSI, without using a reconstructed serie of the values of the precipitation. I'm not even sure this time serie is available somewhere.)

    Mr Russel, this was a tough one!