Thursday, January 23, 2014

Thursday comment: How common are droughts in California?

Another view of the drought in the Santa Cruz mountains, above Silicon Valley

Good news:  You're all on the right track!  

This Challenge, like last week's a some others we've done, is very "key term" sensitive.  That is, you have to figure out what the right words are to use in searching.  

As you've seen, queries like

     [ 2000 years rainfall data California ] 

are too general.  The search results are fine, but not specific enough for what we seek.  

In cases like this, you have to know / learn / discover the terms that are more closely allied with your task.  

You've already got a couple of them:  


And you already have some clues that there were long-lasting droughts in California's past.  This suggests that searching with terms like "severe drought" or "persistent drought" might be useful.  

As always, this has been a great discussion.  I'm looking forward to the rest of the comments today! 

It might also be worth considering "what would the perfect kind of result be for this question?"  Are you looking for a scholarly paper, a data table, a chart?  How would that affect your search strategy?  

Keep searching! 


  1. I almost miss this post, because the new after this.

    I have been thinking about that question Dr. Russell. "What would the perfect kind of result be for this question?" And I can not find the answer. At the beginning, was looking for database. Later, when thought about trees, started looking for papers or books that could mention approximate how was the climate then.

    Looking for those answers, my queries changed. I removed search terms like database, data, years. And, added new, like tree-ring, millennium-scale and dendrochronology.

    I'll try with your tips and also with the data that my peers have found in the SearchResearch Challenge

  2. After my post last night I began thinking that I have found sources of information but I have made no attempt to interpret the data obtained. Therefore was my search actually complete. Can I make an informed analysis without trying to influence? As well, this subject is such a controversial issue.
    I don’t wish to sway anyone’s opinion rather just share my results and how I got there. Then each person can decide for themselves. I tend to lean towards government agencies and research sites only because I want to stick to credible facts. However, that in itself restricts my search. I do like to find within my search sources differing opinions. Here’s an example Paleoclimates outlines several methods of determining historical weather patterns besides using drendochronology with a chart showing two different interpretations over a decade apart. I suppose we could compare this to other charts to find similarites to help validate the data.

    For this challenge presenting charts gives a snapshot which can be obtained via Image Search.They are easy to read and visual. Scholarly type journals/studies by researchers and universities involve will appeal to the intellect. Government agencies provides a wide range of results which perhaps are best looked at over a span of time because of political influence. Perfect sources, I don’t know what that would look like. I think it depends.

    1. That's a great insight. I'll have to write about it. (It's a trick I use all the time, but never thought about writing it up.)

  3. Hi Dan -- How about Fig. 11 in this 2006 paper in Quaternary Science Reviews:

    "Holocene paleoclimate records from a large California estuarine system
    and its watershed region: linking watershed climate and bay conditions"
    Frances P. Malamud-Roama, , B. Lynn Ingrama,b, Malcolm Hughesc, Joan L. Florsheimd
    aDepartment of Geography, UC Berkeley, Berkeley, CA 94720, USA
    bDepartment of Earth and Planetary Science, UC Berkeley, Berkeley, CA 94720, USA
    cLaboratory of Tree-Ring Research, UA Tuscon, Tuscon, AZ, 95721, USA
    dGeology Department, UC Davis, Davis, CA 95616, USA

    (Quaternary Science Reviews 25 (2006) 1570–1598)

    Fig. 11 shows "Extreme climate events in California over the last 2000 years. Shaded areas indicate periods of drought and symbols indicate evidence of excess moisture from selected paleoclimate studies."

    Excerpt from this paper's summary: "Climate over California during the last century has been relatively stable when examined in the context of the past 2000 years, even with the severe droughts of the, 1930s and the mid-1970s. ... Longer term records, including tree rings, and sediments from lakes and from in and around the San Francisco Bay, provide a means of extending records to cover paleoclimate for much of the Holocene. When these longer paleoclimate records are considered, current drought conditions experienced in the US Southwest do not appear out of the range of
    natural variability."

    Another paper by the same first author (Frances P. Malamud-Roam):

    Both of these were on the first page of search results from the terms: ["2000 years" paleoclimate paleoclimatology dendrochronology megadrought "droughts in California"]
    Searching on this first author's name turns up a host of detailed papers, and this U.C. Berkeley PR Q&A with Lynn Ingram (second author on the first paper above) that was issued just on Tuesday:

    "If you go back thousands of years, you see that droughts can go on for years if not decades, and there were some dry periods that lasted over a century, like during the Medieval period and the middle Holocene. The 20th century was unusually mild here, in the sense that the droughts weren’t as severe as in the past. It was a wetter century, and a lot of our development has been based on that."

    That Q&A mentioned this book written by Ingram & Malamud-Roam: "The West without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us about Tomorrow" (

    Best wishes,

    -- Mike Ross

    1. Hi Mike! Glad to see you're reading the blog!

      If you look at my answer, it's remarkably similar to yours. Great minds think alike. I used a somewhat different search to get the same results.

      VERY well done.

  4. Inform or Influence.
    Earth Fever Chart from HotWhopper Blog.
    In the end like the posting I made above and this posting I found Image Search a great way to not only find charts but links to some excellent sites.