Dessler: “Paying the price for climate change” or a case of flawed statistical analysis?

Guest post by David Middleton

My State is currently in the grip of a very severe drought…

Drought conditions in the South-Central US (Source: US Drought Monitor)

Professor Andrew Dessler, an atmospheric sciences professor at our nation’s greatest university, recently authored a column about our drought in the Bryan-College Station Eagle

Published Tuesday, August 30, 2011 12:05 AM


Paying the price for climate change

By ANDREW DESSLER

Special to The Eagle

Texas Gov. Rick Perry stirred up controversy on the campaign trail recently when he dismissed the problem of climate change and accused scientists of basically making up the problem.

As a born-and-bred Texan, it’s especially disturbing to hear this now, when our state is getting absolutely hammered by heat and drought. I’ve got to wonder how any resident of Texas — and particularly the governor who not so long ago was asking us to pray for rain — can be so cavalier about climate change…

[...]

I know that climate change does not cause any specific weather event. But I also know that humans have warmed the climate over the past century, and that this warming has almost certainly made the heat wave and drought more extreme than it would otherwise have been.

[...]

LINK

Dr. Roy Spencer had an interesting take on Dr. Dessler’s column in his blog…

Dessler vs. Rick Perry: Is the 2011 Texas Drought Evidence of Human-Caused Climate Change?

September 5th, 2011 by Roy W. Spencer, Ph. D.

One of the most annoying things about the climate change debate is that any regional weather event is blamed on humans, if even only partly. Such unscientific claims cannot be supported by data — they are little more than ambiguous statements of faith.

[...]

Andy Dessler recently made what I’m sure he thought was a safe claim when faulting Texas Gov. Rick Perry for being “cavalier about climate change” (as if we could stop climate from changing by being concerned about it).

Dessler said, “..warming has almost certainly made the (Texas) heat wave and drought more extreme than it would otherwise have been.”

This clever tactic of claiming near-certainty of at least SOME effect of humans on weather events was originally invented by NASA’s James Hansen in his 1988 Senate testimony for Al Gore, an event that became the turning point for raising public awareness of “global warming” (oops, I’m sorry, I mean climate change).

The trouble is that climate change theory predicts changes, up and down, in just about anything you can imagine. So, anything unusual that happens anywhere, anytime, is deemed “consistent” with global warming.

[...]

LINK

According to Dr. Spencer the current national drought conditions are not exceptional; nor is there any statistically significant trend…

And, while Texas is experiencing a record-setting drought; the “record” is just over a century-long and there is no trend at all…

The lack of a trend in the precipitation data made me wonder… Just how often should we be setting precipitation records if the annual variation is random?

The record only goes back to 1895. Does anyone know how often record highs and record lows should be broken in such a short time series?

At a record length of 117 years, there was a 1% chance of setting a new record high in the 117th year…

The probability, pn(1), that the nth observation of a series xm= x1, x2, … xn has a higher value than the previous observations [pn(1) = Pr(xn > xi |i < n)] can be expressed as:

pn(1)= 1/n (1)

provided the values in series are iid random variables.

(Benestad, 2003)

The cumulative probability says that 5 records should have been set between 1895 and 2011.

So, let’s have a look at the data. I downloaded the summer precipitation data for Texas from NCDC’s “U.S. Climate at a Glance” page…

Texas Summer Precipitation (Source: NCDC)

In order to analyze the frequency of record excursions, I plotted the absolute value of the annual summer precipitation anomaly along with an “expected records” curve…

Precipitation Anomaly and Expected Records

There have been 5 record excursions from the average annual summer precipitation – Exactly what there should have been in a random series of numbers. And the records have occurred with the expected frequency of a random series of numbers. The fifth record excursion should have occurred between 1945 and 2030 – It occurred in 2007.

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100 thoughts on “Dessler: “Paying the price for climate change” or a case of flawed statistical analysis?

  1. This is a great posting David on a personal note to Anthony this site has made it so that I can intelligently discuss AGW you have helped a lowly high school grad to understand some very complex things and I thank you for that.

  2. “Warming has almost certainly made the (Texas) heat wave and drought more extreme than it would otherwise have been.”

    Almost Certainly. And how do you know this, Dr. Dessler? I have a general question concerning the general heat problem: How does a fraction of a degree of warming over a century translate into many tens of degrees in a heat wave? I never quite understood the non-answer to this question lurking in that CC-causes-extremes camp. And what fraction of that degree is “normal”? Who determines “normal”? (I know it’s not a “what” but a “who”). The idea that there is stasis in the climate from which we can then derive an “alarming change”, is flawed at the root. To paraphrase Dessler, “climate change is almost certainly caused by man, because otherwise it would be normal”

  3. Dessler would know all this if he were either curious or a scientist. But if he has to read it here, so be it.

    /snark

  4. As the climate is chaotic, any database of any aspect (e.g. rainfall) will see more extremes in both directions, the further out you go in time.
    Rainfall is NOT normally distributed.

  5. As I’ve repeatedly lectured Steve Goddard about this on his blog, this simply isn’t the way to do science.

    Your fundamental mistakes were (in order):
    1. You posed a question
    2. You constructed a hypothesis
    3. You created an experiment to test this hypothesis
    4. You specified the parameters of whay would validate your hypothesis
    5. You carried out the experiment.

    You see, this just isn’t science. Science is:
    1. Determine the outcome required to secure funding
    2. Construct a model to generate the required outcome
    3. Locate data that supports the model
    4. Announce the predictive power of your model and make a prediction fo far enough into the future so that you’ll be retired by the time it will be falsified.

  6. @ David Middleton,

    Excellent post. One small quibble, the best University in the state is in Austin… (hook ‘em!!)

    However, you are correct in the data and analysis. I also looked recently at the trend in Texas’ total yearly precipitation, also from NCDC data and came to the same conclusion. There has been no great trend, only a very slight increase of 0.77 inches per century.

    From the data at NCDC, this current Texas drought is nothing compared to the drought from the late 1940s into the late 1950s. That drought saw 9 out of 10 years with well-below average total annual precipitation. Average for Texas is 28 inches per year, data for the decade 1948 – 1957 was

    Year .. inches
    1948…22.65
    1949…23.18
    1950…31.90 <==== only year higher than average
    1951…24.38
    1952…20.65
    1953…22.22
    1954…24.03
    1955…18.54
    1956…22.41
    1957…15.23

    link: http://www.ncdc.noaa.gov/temp-and-precip/time-series/index.php?parameter=pcp&month=1&year=2011&filter=12&state=41&div=0

  7. This type of careful, rational analysis is exactly what provides the underpinning or a rational discussion of how to deal with inevitable climate change, up, down and sideways.

    I thank you on behalf of myself and those who are yet enthralled by the banner-waving provocateurs intent on overthrowing their select dominant paradigms. They sleep. I prefer the paradigm where the moral scientist seeks discovery and whose ethically impeccable behaviour should be that revered at every lab bench and in every honest heart beating within a white coat.

    CAGW is a moral problem ruled at the moment by disingenuity and deflection. It is a failing paradigm. We cope with nature, not conquer it.

  8. The 1950s dought was a real tear jerker in Texas that produced one of the greatest works of Texana Literature.

    The old timers say 1917 was real bad. And 1998, 2006, and 2007 were also very bad.

    And the Indians said that sometime in the late 1700s or early 1800s there were three years when it did not rain at all.

    In NE Texas on the unplowed prairies you can find grasses that usually are present in West Texas where rainfall is half of that. And then there are the small colonies of desert like succulents that are usually found in areas that get 5-10 inches of rain. Texas used to be far drier than it is now.

    And before that the bones of herbivores from 1500 AD to 10000 BC show a climate seesawing from cold to hot and from dry to wet constantly.

    The fire history of Texas is another subject, but most of the big fires this year have been fueled by juniper and loblolly pine that has not been controlled in any meaningful way.

    Austin, TX W of I-35 is now mostly a solid stand of Juniper and its just a matter of time until it all goes up like Oakland did in 1991.

  9. @ AusieDan, re

    “Rainfall is NOT normally distributed.”

    What is your basis for that statement? I just now ran a histogram of annual precipitation in Texas, using the same data as my comment above, from NCDC since 1895 and obtained a curve that is very nearly bell-shaped. It is not a perfect Gaussian curve, but it’s not far off, either.

    see http://tinypic.com/r/olog7/7

  10. “at our nation’s greatest university” That brought a big grin to this Texian not affiliated with either school. I see a T-sipper has already posted a weak rebuttal.

    It just proves there is no such thing as an ex or former Aggie.

  11. Heavy stands of juniper and loblolly pine! My god! how long has your state been infested by ” Smokey the Bear”. And you probably have large numbers of city people that have moved into this fire trap to “live out in the country”. And to think California is supposed to be the state populated by stupid people. OH well, a good fire will solve one of the problems. I don’t how to cure stupidity. pg

  12. Roger Sowell says: September 13, 2011 at 9:19 pm
    @ AusieDan, re
    “Rainfall is NOT normally distributed.”

    What is your basis for that statement?

    For one thing, Negative rainfall is impossible by definition, yet must be possible if it is a Noral Distribution. — You asked.

  13. Mike Bromley the Canucklehead (September 13, 2011 at 8:32 pm) “I have a general question concerning the general heat problem: How does a fraction of a degree of warming over a century translate into many tens of degrees in a heat wave?”

    Nailed it for me, Mike; and one can expand that question into how a fraction of a degree of warming over a century can even raise a pulse, let alone catastrophic panic and billions of dollars.

    Were too many of us just bored on the day?

  14. I have spent some time statistically analyzing daily precipitation and daily mean temperatures for some nearby individual stations (available via KNMI Climate Explorer). If the “jumpiness” of those was increasing as claimed, their standard deviation should go up. Alas, it is not the case at all. That’s why we NEVER see those hard data, just wild and unfounded claims.

  15. You have to really admire the premise of the environmentalist wackos.

    If you question anthropogenic climate change, or if you’re asked about it and you say you don’t agree with it, it’s controversial.

    But someone who comes out and says they agree with climate change, somehow, they aren’t taking a controversial position.

    Am I missing something here? Isn’t public opinion on this matter pretty much 50/50 in most polls on the subject of man-made climate change itself; and much lower if polled in the form of “What issue is most important to you?” out of a list of say 15 items of ‘importance’.

  16. I think it odd that Andy Dessler the Aggie would stick his foot in it at this point. He must not get out of his house; otherwise he would have noticed the record rainfall in 2007 and the extra rainfall in 2010. He would also have noticed that North Texas, at the beginning of this summer, had full reservoirs because of the winter and spring rains.

    But leave it to a political hack to think otherwise.

  17. I love articles like this one, just the kind of “just the facts” article that we need a few hours before Gore et al start their mass delusion machinery!

    One remark, though: Why the comments about normal distribution? The condition in this statistical exercise says nothing about normality, it is that the variables should be “iid” (independent identically distributed) random variables. However, independence is not assured here, because of the ENSO-influence on Texas rainfall. My statistics is getting a little rusty, so I wouldn’t be the best judge here, but OTOH I think the argument presented is reasonable despite this caution.

  18. Texas weather is driven by external pressures such as La Nina/El Nino the cool phase of which produces dry Texan years. This particular La Nina has been prolonged and seems to be destined to last longer. Texas also lies within the desert latitude of climate planetary banding so should be used to dry weather. The problem in Texas is a rising population and increasing water demand which will make things far worse as water tables are forced ever lower.

    Gov. Perry is right. Vote Perry for President.

  19. Roger Carr says:
    September 13, 2011 at 10:41 pm
    Nailed it for me, Mike; and one can expand that question into how a fraction of a degree of warming over a century can even raise a pulse, let alone catastrophic panic and billions of dollars.

    ———-

    The reason is it’s an average increase of a fraction of a degree over the whole globe over a whole year. That doesn’t mean that every day will be half a degree hotter everywhere.

    Read up on some basic maths of averages if you still have trouble with this.

  20. As I understand it, the Earth is roughly divided into five climatic zones and within each zone there are variations because climate is determined by altitude as well as latitude.
    And a long standing fact I’ve understood about climate is that, Climate is the usual WEATHER of a place over a long period of time. The weather can change from day to day but the climate stays the same. Is this NOT true?

    Looking geographically at Texas, it is positioned in a Desert (Dry) climatic zone, and to the north of Texas there is a Temperate (mild winters) climatic Zone, and to the south of Texas there is a Tropical Rainy (warm, moist) climatic zone.

    Out of these five climatic zones, Polar (Cold), Cold Forest (Cold Winters), Temperate (Mild Winters), Desert (Dry) Tropical Rainy (Warm, Moist), Where would the place be that we would be more likely to expect a drought and heatwave? My guess would be in a Desert (Dry) climatic zone.

    Why then is a so called ‘climate scientist’ spouting of remarks such as this?
    “…But I also know that humans have warmed the climate over the past century, and that this warming has almost certainly made the heat wave and drought more extreme than it would otherwise have been.”

    So, this is a ‘scientist’ that has proclaimed that humans have warmed the planet without any empirical evidence and secondly and most bizarrely in the same sentence, he enforces the belief of the first part of his statement by attributing the cause of the heat wave and drought to known natural variations of an understood climatic zone namely a Desert (Dry) climatic zone, and that these known natural variations must be more extreme due to the first part of his statement.
    Tho if you think about it a heat wave and drought is not considered as being an extreme condition in a Desert (Dry) climatic zone in the first place, so these kind of comments are all fluff and lack the basic grounding of reality that you would expect from someone claiming to be a scientist.

    What’s to stop anyone from proclaiming that in light of the past four winters;
    “…But I also know that humans have cooled the climate over the past century, and that this cooling has almost certainly made the winters and freezing conditions more extreme than it would otherwise have been.”

    It certainly is a weak scientific argument for Anthropogenic climate change in my view.

  21. Tom C says:
    September 13, 2011 at 11:32 pm

    I don’t think public opinion is a good measure on the truth of something though. A good measure might be the percentage of experts who have researched the subject in question.

  22. If a person with general background in topography, prevailing wind direction, and orientation with respect to the tropics, but no knowledge of local climate history, were to look at a map of the US mainland, he would likely guess something like this:

    From its location, east of the Rockies, northwest of the Gulf, south of almost all of the rest of the states, Texas can expect very warm to hot summers, mostly dry since moisture would have a hard time vaulting the Rockies and southeast winds don’t usually penetrate far from the coast. Winters can get chilly, since there are no major natural barriers between the north Texas plains and Canada; but the southern location should mitigate that to some extent.

    I’d say those general expectations have been met this year, as during many past years. The wet years the state has enjoyed could be regarded as exceptional; and in some of those years, it was tropical cyclones that swelled the wetness of the statistics. This year has been unusually dry, in many places calamitously so; but given the expectations from the map, it would seem obvious that even a mild “blocking high” or similar event could produce a summer such as that now happening in Texas. It is sad; I wish I could send some of our Virginia moisture there (9.2″ last week); but it is well within the realm of possibility.

  23. Those graphs really tell the story! In US overall, the trend is toward less extremes of precip, which is of course contrary to what the Holy Carbon Models tell us. In Texas, the trend is toward more extremes of precip, which would indicate that the jet stream is getting “locked in” more often. The latter seems to be a worldwide tendency, esp in last 30 years or so.

  24. Having had the misfortune to spend much of the Summer and Fall of 1980 — also a drought year — in Texas, I’ve viewed the current situation with a mixture of amusement, sympathy, and thankfulness that I don’t live there.

    AFAICS, the current situation is little different than 1980 except that Texas finally got a little rain in September 1980 when Hurricane Gilbert came ashore in the Western Gulf. Is there a case for climate change making the temperatures a little (not much) higher than they were in 1980? Probably. Drier? You’re kidding, right? No rain is no rain. Is there any reason to believe that Climate Change has made any significant difference? Not that I can see.

    Dessler? Not impressed. Comes across as every bit as faith based as Perry. Just worships at a different alter. Surely “Climate Science” must include a few actual scientists. Might be time to dust a few off and let THEM talk to the public.

  25. Indeed a great post and totally debunks the claim that the extreme dry weather is a result of MGW. How would we explain the extreme wet weather of 2007 … and as you point out there is no trend.

    The only possible argument might be that there is increased chaos in the system leading to greater extremes at both ends of the spectrum. Can you also analyse for increased variability or chaos in the system ? Is there any trend there ?

  26. SteveE says:
    September 14, 2011 at 1:54 am
    Roger Carr says:
    September 13, 2011 at 10:41 pm
    Nailed it for me, Mike; and one can expand that question into how a fraction of a degree of warming over a century can even raise a pulse, let alone catastrophic panic and billions of dollars.

    ———-

    The reason is it’s an average increase of a fraction of a degree over the whole globe over a whole year. That doesn’t mean that every day will be half a degree hotter everywhere.

    Read up on some basic maths of averages if you still have trouble with this.
    ——————————————————————-
    Hi Steve. You know that axe cuts both ways? The normals that anomalies are compared to are averages, and so it’s normal to have highs and lows in the meteorological record.

  27. SteveE tells me to: “Read up on some basic maths of averages if you still have trouble with this.”

    No trouble with averages, Steve — but some trouble with you missing the point I made; or perhaps choosing to misrepresent what I said for your own (or for AWGers in general) reasons.

    Who is denying this general rise in temperatures of a fraction of a degree? Certainly not me; and that being said I repeat: “…how (can) a fraction of a degree of warming over a century even raise a pulse, let alone catastrophic panic and billions of dollars.”

    We have to have been bored, or asleep, on the day…

  28. Seriously, though, Dessler really is an embarrassment. Dr. Spencer has been exceptionally nice to him despite his undeserving stance as of late.

    Gary Turner says:
    September 13, 2011 at 9:32 pm

    Gary, cut Roger some slack…he’s one of the good guys :). I’ve read some of his writings on the internet and I’d take him any day over Dessler by a country mile.

  29. There has always been “Climate Change”. There will always be “Climate Change”. The problem is that the “warmest s” have taken the high ground by a clever technique of automatic association. In the general public’s mind, the words “Climate Change” are now linked to man made actions!

    “But I also know that humans have warmed the climate over the past century, and that this warming has almost certainly made the heat wave and drought more extreme than it would otherwise have been.” [Dessler]

    This is the statement that we (via GOOD [non-biased] Scientific Research) must adamantly oppose. How does HE “know that humans have warmed the climate”????? Faith in the money stream??

  30. @Stephen Rasey,

    “For one thing, Negative rainfall is impossible by definition, yet must be possible if it is a Noral Distribution. — You asked.”

    Well, you got one thing correct. Negative rainfall is rather scarce. However, it is quite possible to run a statistical analysis (a simple one) for data distribution on the total annual precipitation. I suspect that any introductory statistics class will teach this.

    I provided a tinypic above for the distribution curve for annual precipitation in Texas. Again, the data is almost normally distributed around the mean of 28 inches per year.

  31. Excellent post. Sent link to friends and relatives, with this subject and comment:

    Faith-based vs. real science in Texas

    Faith:

    Dessler: “I know that climate change does not cause any specific weather event. But I also know that humans have warmed the climate over the past century, and that this warming has almost certainly made the heat wave and drought more extreme than it would otherwise have been.”

    Science:

    Spencer: “The trouble is that climate change theory predicts changes, up and down, in just about anything you can imagine. So, anything unusual that happens anywhere, anytime, is deemed “consistent” with global warming.”

    Middleton: “And, while Texas is experiencing a record-setting drought; the “record” is just over a century-long and there is no trend at all…

    “There have been 5 record excursions from the average annual summer precipitation – Exactly what there should have been in a random series of numbers. And the records have occurred with the expected frequency of a random series of numbers. The fifth record excursion should have occurred between 1945 and 2030 – It occurred in 2007.”

    Me: Faith is based on ideology. Science is based on evidence.

    /Mr Lynn

  32. Couple comments and questions:

    Since the warmists claim an increase in extreme events, does the texas data show a divergence between max and min? Is it statistically significant on such a short record?

    Isn’t Texas always a dry, hot state?

    It seems clear to me that human industrialization has destroyed the natural environment of Texas. The lush tropical rainforests of Texas are no more, and the Texas gorillas are extinct. Weep for the Earth. /sarc Seriously… I’m pretty sure the natural vegitation in Texas are types that can withstand severe drought. That’s probably because this happens there a lot. Just sayin’

  33. @polistra,

    “In Texas, the trend is toward more extremes of precip,. . .”

    Actually, no, the NCDC data for Texas’ annual precipitation shows fewer extremes since 1959.

    I chose 1960 as the boundary in the data because an eye-ball analysis indicates that’s about where the data quit bouncing around as much. The smoothed trend line also

    One measure of variability is standard deviation. Using that metric, pre-1960 annual precipitation for Texas has a standard deviation of 5.7 inches. For 1960 and later, the standard deviation is lower at 4.2 inches.

    The annual average also increased by almost one inch per year, comparing the period pre-1960 to the period of 1960 to 2011. In Texas, at least, it is not getting drier nor is the rain/drought cycle getting “wilder” or more extreme. Quite the opposite. Meanwhile atmospheric CO2 level continues to increase.

    This would make quite an interesting study to use the available data for other regions / states and confirm or debunk the warmists’ claim of wilder and more extreme rain / drought.

  34. I’ve come to understand that the habit of comparing a day’s, month’s or season’s weather to the “average” leads to misconceptions about the weather and climate. Often this mistake is compounded by using the term “normal” instead.

    When we compare weather to the “average” it makes our daily highs and lows appear more extreme. But by looking at the record highs and record lows, we see that our weather usually sits comfortably within that range.

  35. Dear Dr. Dessler,

    You seem to a glutton for punishment, a mouth awaiting a foot. You might want to act more like a scientist and check the data BEFORE you come to a conclusion.

    Since you are so enthused about the Texas Drought situation, here is the data for the history of drought in Texas. The long term (100+ years) shows drought is improving in Texas and the current drought is moderate at best.

    http://tinyurl.com/3f53gr6.

    We’ll await you apology letter.

  36. “Does anyone know how often record highs and record lows should be broken in such a short time series?”
    As temp increases, both should be broken more often. Variability increases. Deeper and more prolonged droughts as well as more precipitation when it rains.

    Netherlands were typical this year. Record dry spring. Record wet summer. Records set as of 1901.

  37. Dessler said, “..warming has almost certainly made the (Texas) heat wave and drought more extreme than it would otherwise have been.”
    ===============================================
    Yep, that 1/10th of a degree pushed it over the top…………………/snark

  38. Sorry Roger Sowell, AusieDan & Stephen Rasey are right. Rainfall does not have a normal distribution. I have found that the distribution of my area of Australia is close to a Poisson distribution where the standard deviation is close to the average. The peak or record rainfall (monthly values from 1893) is five to seven standard deviations (eg January av 235mm SD 205 record 1384mm, August av 59 SD 52 record 375mm, December av 173mm SD 121mm record 668 mm latter in 2010 when there were floods in January with normal rainfall for that month- the wettest month is actually February)
    Mentioned the Poisson distribution for rainfall in a post by Willis E sometime ago and he suggested it was actually a Chi square distribution.

  39. Love Governor Perry or hate him, he is still the only politician smart enough or with courage enough to speak the truth: AGW is a hoax and Social Security is a Ponzi scheme!

    Me, I’m sort of lukewarm on the Gov. Still I have to respect him for saying that the “Emperor has no clothes”.

    By the way, the Gov is not the first Texan to speak up about Social Security. Watch these and weep for our children:

    Regards,
    Steamboat Jack (Jon Jewett’s evil twin)

    Full disclosure:
    I went to a six day marine firefighting school at Texas A&M College Station. A friend says that makes me an Aggie. I even graduated!

  40. Methinks the goddess of climate change, the beloved CO2, is lazy and only works to raise temperatures in some areas some of the time. Perhaps her motto should be “I can heat some of the air all of the time, and all of the air some of the time, but I cannot heat all of the air all of the time”. (My apologies to P.T. Barnum)

  41. @ Roger Sowell and Stephen Rasey

    Stephen is certainly correct that the distribution is not (and cannot be) a normal distribution; on the other hand, Roger is correct that an eyeball look at the data distribution looks like a rough approximation of a normal distribution.

    I admire the approach that David Middleton has come up with, but the question is, how close to ND is close enough?

  42. SteveE says:
    September 14, 2011 at 2:48 am

    ===========================================
    Steve, are you intentionally missing the points of the comments or do you need an interpreter?

    Roger didn’t imply the average was uniformly distributed. Why would you infer that he did? And Tom wasn’t stating that public opinion was a measure of truth, he was talking about the word “controversial” and how Dessler attached the word to Perry’s position.

    Did you take a class from Dessler in interpretive reading skills? You seem to share the same characteristics

    Now, could you direct me to one of the “experts” of the subject? I’m anxious to hear the thoughts of a person so well versed in physics, astrophysics, molecular chemistry, meteorology, geology, archeology, hydrology, statistics, history, botany, biology, etc…..

  43. SteveE says:
    September 14, 2011 at 2:48 am

    Tom C says:
    September 13, 2011 at 11:32 pm

    I don’t think public opinion is a good measure on the truth of something though. A good measure might be the percentage of experts who have researched the subject in question.
    True, public opinion by itself doesn’t tell you much about the truth. However, in the case of CAGW what we’re seeing is that despite a massive onslaught of Warmist propaganda for a number of years, plus a famous Nobel-prize-winning slideshow supposedly based on truth, public opinion is actually moving away from the Warmist ideology. Now, for a rational person, if the more and louder a “truth” is told, the less people believe it, then it would be logical to assume that there is something fundamentally wrong with said “truth”. Only those who are irrational, or have motives other than truth-telling would say that the failure lies with “the communication”, yet, amazingly enough, that is the general stance of the CAGW community.
    Regarding “the percentage of experts who have researched the subject”, i.e. “the consensus” being a “good measure of the truth”, that is a logical fallacy trap that Alarmists fall into quite often. You might want to read up on logical fallacies, if you still have trouble with that.

  44. >> SteveE says:
    September 14, 2011 at 2:48 am
    I don’t think public opinion is a good measure on the truth of something though. A good measure might be the percentage of experts who have researched the subject in question. <<

    Therefore, since the percentage of Catholic Priests (experts on religion) who say that God exists is well over 90%, there is no question that it's true.

  45. Gary Turner says:
    September 13, 2011 at 9:32 pm
    “at our nation’s greatest university” That brought a big grin to this Texian not affiliated with either school. I see a T-sipper has already posted a weak rebuttal.

    It just proves there is no such thing as an ex or former Aggie.

    In my case… I’m an Aggie by marriage.

  46. SteveE says:
    September 14, 2011 at 1:54 am
    Roger Carr says:
    September 13, 2011 at 10:41 pm
    Nailed it for me, Mike; and one can expand that question into how a fraction of a degree of warming over a century can even raise a pulse, let alone catastrophic panic and billions of dollars.

    ———-

    The reason is it’s an average increase of a fraction of a degree over the whole globe over a whole year. That doesn’t mean that every day will be half a degree hotter everywhere.

    Read up on some basic maths of averages if you still have trouble with this.

    Texas didn’t participate in that fraction of a degree of global warming…

    Texas Annual, Year-to-Date & Summer Temperatures (1885-2011)

    2011, particularly our summer, is a random outlier.

  47. so if not for “humans” a 105 degree day would have been 104.3 degrees … I don’t know about you but I can’t tell the difference between 105 and 104.3 … maybe Dr. D can … and this man is considered a scientist ? Really ???

  48. David,

    Straight shootin’ and on target statistics there, Tex! You’ve given us another timely and relevant analysis to refute the misguided statements of Dessler et.al.

    Thank You!

  49. “P.G. Sharrow says:
    September 13, 2011 at 9:42 pm
    Heavy stands of juniper and loblolly pine! My god! how long has your state been infested by ” Smokey the Bear”. And you probably have large numbers of city people that have moved into this fire trap to “live out in the country”.”

    The fires are everywhere not just in the trees but the tree areas around here in central Texas have finally had some of the dreaded massive outbreaks that plague the southern left coast. At last count a record 1,554 houses completely lost in one fire complex of around 34,000 acres. Numerous other fires of record number and acreage this year and a double-dip La Nina to look forward too.

    Just another routine year in Texas as far as weather and climate go. Nothing to see here, move along.

  50. Not wishing to be pedantic, but the closing paragraph states:
    “There have been 5 record excursions from the average annual summer precipitation – Exactly what there should have been in a random series of numbers.”

    I wiould haev thought that it was impossible to say what a random series ‘should’ produce, more accurate would be:
    “There have been 5 record excursions from the average annual summer precipitation – Exactly what one would expect in a random series of numbers.”

    Pedantic I’ll accept, but working for years in patents does that to you.

  51. Some one above commented on whether rainfall follows a normal distribution: I believe that for daily totals, it has been generally found that a Gamma distribution is better. But that doesn’t mean that seasonal/annual totals aren’t approximated quite well by a normal distribution.

  52. I make 6 figures at an oil company and have thousands invested so I don’t believe any of the global warming science. I also wouldn’t believe the world is round if it threatened my livelihood. So keep undermining the science–I’ve got to make payments on my Lexus! Lol

  53. David,

    I appreciate the approach you took to evaluating if the current rainfall (and temperatures) amounts in Texas fall within what the climate process has historically been. As you pointed out the variation around the average value has to be considered to answer the question.

    As you have worked in the oil and gas industry for a few years you have likely already seen the “Dr. Hansen’s 1981 Projections Compared to Observations”- graph showing us how bad things will be if we don’t stop using fossil fuels. http://images.sodahead.com/profiles/0/0/2/1/6/9/7/0/5/1981cfobs-46485264070.jpeg

    I came across the graph in a post by Icarus says:September 10, 2011 at 11:26 am of interest-
    “I would ask this:Hansen’s 1981 projections are matching reality pretty well so far that lead me to – Dr. Hansen’s 1981 Projections compared to Observations.

    I hadn’t seen the Hansen graph before. As it’s been a bit over 30 years since it was first published, maybe Al Gore will be presenting an updated version of the graph at his upcoming event.
    I assume Dr. Hansen’s estimates (projections/scenarios/etc.) of the growth of fossil fuel usage was a little low compared to what has happened in the last thirty years. It seems to me that if we want to evaluate the 1981 projections we need to look into the implied CO2 sensitivity value used to generate the graph for each of the fossil fuel usage time points by scenario. Maybe Dr. Hansen would be willing to update the fossil fuel usage values from his original estimates ( we have 30 years data now) to the real thing without modifying the original CO2 sensitivity value. Then we could tell if the projections are matching reality well or not.

  54. Dessler said, “..warming has almost certainly made the (Texas) heat wave and drought more extreme than it would otherwise have been.”

    It’s called La Nina…nuff said

  55. SteveW says:
    September 14, 2011 at 7:34 am
    Not wishing to be pedantic…

    That’s OK. I wasn’t wishing to be deserving of pedantic criticism… You are correct. I should have better worded that last paragraph.

  56. So if I were to say “Warming has almost certainly not made the Texas heat wave and drought more extreme than it would otherwise have been.” can I not say that this is just as true a statement as “Warming has almost certainly made the (Texas) heat wave and drought more extreme than it would otherwise have been.”

    Weasel words make me so mad!

  57. Andy ‘toes touching tonsils’ Dessler says:

    “But I also know that humans have warmed the climate over the past century, and that this warming has almost certainly made the heat wave and drought more extreme than it would otherwise have been.”

    He knows these things? Knows? Really?

    It was undoubtedly that sort of self-deceptiveTexan conceit that prompted the most famous son of neighboring Oklahoma to observe:

    “It isn’t what we don’t know that gives us trouble, it’s what we know that ain’t so.”
    Will Rogers

    Confusing faith for knowledge is the sort of thing that the likes of Dessler falsely (and fallaciously)use to ad hom Spencer… the pot calling the driven snow ‘black’.

  58. This guy walks into a bar and orders a drink. As the bartender serves the drink, the guy asks, “Hey, I heard a good Aggie joke the other day. Do you want to hear it?” The bartender says, “Well before you tell it, I should warn you that I’m an Aggie. See those two guys at the end of the bar? They’re Aggies. And see those guys over at that table. They’re Aggies too. Are you sure you want to tell that joke?” The guy replied, “Hell no! I don’t want to explain it five times…”

  59. Something I’ve noticed over the years of watching this debate is warmists usually have a definition of what a “normal climate” is. Usually a “normal climate” is better defined as good, or temperate, weather. I recently got a good dose of that when I was in the Galapagos Islands in August.

    The naturalists who were leading out our trip to these AMAZING islands, were very clear that El Niño was a negative scenario in the Galapagos. Essentially, when El Niño roars the water warms up around there, becomes less fertile and the sea life, and other life that depend upon productive seas, suffer greatly. Never mind that this is what spurs natural selection and speciation. Also never mind that during El Niño seasons, it is very wet and the land animals do quite well in Galapagos. Also never mind that in Texas we are typically enjoying cool, wet, and productive weather. El Niño is BAD and caused by AGW according to all of the Galapagos naturalists.

    La Niña, on the other hand, is a blessed paradise down there and represents the natural order of things. The Humboldt current runs strong from South America and brings in cold, abundant waters to the seas around Galapagos. The marine mammals, birds and iguanas thrive in these conditions. Never mind that it doesn’t rain and the land animals are put under severe pressure. Never mind that in Texas it doesn’t rain and we fry under a relentless sun, as we have been under the latest La Niña conditions. To them, this is the natural state of things and anything that upsets it is global warming caused by human burning of fossil fuels.

    I finally told our naturalist, “it sure saddens me that all of the lesser animals in Texas have to fry in a drought in order for the special ones in Galapagos to thrive.”

    She declined to respond, but I think it may have shorted a few circuits in her brain.

  60. Y’all might want to read what one of Anthony’s co-authors has to say on this topic.

    REPLY: Well, unlike the team, co-authors don’t form a wagon circle consensus for the sake of it. We have sometimes divergent opinions, which is always a plus in science. This is why we invited him to be part of the paper. – Anthony

  61. SteveE says:
    September 14, 2011 at 2:48 am

    I don’t think public opinion is a good measure on the truth of something though. A good measure might be the percentage of experts who have researched the subject in question.

    Snap out of it, Steve! How’s about “the truth of something” being manifested by its production of correct empirical predictions? Since you don’t refer to this standard and seem to intentionally avoid it, the “something” being allegedly professed by you and your “experts” is therefore not saying anything relevant to the empirical reality which it only appears to be talking about. It’s words and symbols instead constitute nonsense as compared to empirically meaningful factual claims, no matter how many of the “experts” which you yourself have merely annointed as experts say and write the noises and appearances which you and they like to hear and see.

    Don’t be fooled by making a simple mistake! Just because people put symbols together in the form of factual statements, it does not follow that their symbols are indeed factual claims. Their symbols must relate to empirical reality via real scientific method and principle science. So far, “CO2=CAGW” doesn’t, and it’s therefore not even intended to relate to reality, at least as used by your ipcc Climate Science, enc., “experts”!

  62. Roy treating records as a set of incremental numbers that have been randomized and assuming the first number in the randomized set is a record,the number of records to be expected is equal to: ln n where n= the number in the set or number of years in this case. Your graph certainly shows the log function and ln 120 does equal 4.8 (your 5 records). The nature of the beast is revealed when you explore how long we can expect to wait for the next record, wait for it! Ln 420=6 so we should expect to wait over a couple of centuries for the next record. Of course we are talking random so it could happen next year, but not likely.

    Of even greater interest and a wonderful check on this randomness of weather records, and dare I say essentially a powerful proof of the skeptic’s position on CAGW, is the fact that all weather records would therefore be 5 – floods on the Red River of the NOrth which I found to be 5 as well and reported this result in a comment on the subject in WUWT, etc. I think it would be a fun exercise to check out snowfall,rainfall, hurricane, etc records in particular regions and see if they, too number 5.

  63. For completeness, you should repeat your statistics for droughts. Are there 5 records as well over the last 117 years?

    Please update the blog post so I can see your debunk go all the way!

  64. Mark says:
    September 14, 2011 at 7:52 am

    Mark, the observations plotted on that graph do not appear to match any of the four major compilations of global temperature anomaly. The plot shows no 1998 peak, and it shows a significant increase in the last decade, which has not been the case.

  65. Bill says:
    September 14, 2011 at 8:54 am

    For completeness, you should repeat your statistics for droughts. Are there 5 records as well over the last 117 years?

    Please update the blog post so I can see your debunk go all the way!

    I calculated the absolute value of the anomaly… The records were for maximum excursions from average. So the five “records” were for extremes in both directions.

    If you parse it by maxima and minima, there have been five records in each direction… Which is exactly what you would expect from a 117 year long record of random numbers.

  66. Rattus Norvegicus says:
    September 14, 2011 at 8:38 am

    Y’all might want to read what one of Anthony’s co-authors has to say on this topic.”

    “Precipitation: The balance of evidence does not support the assertion that the rainfall deficit since October 2010 was made larger or more likely by global warming.”

  67. David Middleton:

    Thankyou for your excellent, concise and useful article.

    Dessler’s comment seems to be an example of a recent meme because there have been warmists recently making similar comments (e.g. with respect to hurricanes) on WUWT. Their assertions have been countered by pointing out that statistics do not support their claims, but they have failed to understand the point. Warmists (especially warmist trolls) have little knowledge and understanding of science and mathematics – especially statistical analyses – so it is difficult to point them to a clear explanation they can comprehend. Your article povides an example of such a clear explanation.

    Again, thankyou.

    Richard

  68. Gary Turner says:
    September 13, 2011 at 9:32 pm
    “at our nation’s greatest university” That brought a big grin to this Texian not affiliated with either school. I see a T-sipper has already posted a weak rebuttal.

    It just proves there is no such thing as an ex or former Aggie

    How do you define gross ignorance? 144 Aggies in the same room! :-D

  69. And a long standing fact I’ve understood about climate is that, Climate is the usual WEATHER of a place over a long period of time. The weather can change from day to day but the climate stays the same. Is this NOT true?

    I don’t think that is true. For instance, if you’re in Scotland – go outside, right now. It’s raining.
    Having lived in Scotland I know I stand a pretty good chance of being right, no matter when I say that. Does that make the statement “It’s always raining in Scotland” accurate? I think not.

  70. What is the difference between the Aggies and Rice Crispies? Rice Crispies know what to do in a bowl.

    Why do Aggies like smart women? Opposites attract.

    Why did the Aggie get fired from the M&M plant as a quality control inspector? He kept throwing out all the W&W’s!

    CAGW has not a thing to do with this. 1930′s level volcanic activity…

  71. Returning to “normal” rainfall will never break a drought….
    ….floods break droughts

    …you just can’t win

  72. Mike Bromley the Canucklehead says:
    September 13, 2011 at 8:32 pm
    “Warming has almost certainly made the (Texas) heat wave and drought more extreme than it would otherwise have been.”

    Almost Certainly. And how do you know this, Dr. Dessler? I have a general question concerning the general heat problem: How does a fraction of a degree of warming over a century translate into many tens of degrees in a heat wave? I never quite understood the non-answer to this question lurking in that CC-causes-extremes camp. And what fraction of that degree is “normal”?

    ##################################

    Pos feedback. One is the main one which is water vapor. If it concentrates more infrared is reraditated back to the earth increasing the local temperature.

    Texas had a pos feedback from drying out its land. A little higher temperature evaporates all the more water vapor sooner. A high is created around the really dry area of land and it becomes self perpetuating. This would of happened with AGW, but adding more temperature doesn’t help.

  73. You can have negative rainfall. Its called pan evaporation rate.

    Rainfall – sum( evaporation rate)

    Pan evaporation rates are interesting in and of themselves from a climatological perspective. It takes ALOT of energy flow to evaporate water and this is indicative of solar flux and surface temps.

    And the evaporation rate has been going down for some time. Now there may be lots of “surface station” like problems with the measuring sites.

    http://en.wikipedia.org/wiki/Pan_evaporation

    “Over the last 50 or so years, pan evaporation has been carefully monitored. For decades, nobody took much notice of the pan evaporation measurements. But in the 1990s scientists spotted something that at the time was considered very strange; the rate of evaporation was falling. This trend has been observed all over the world except in a few places where it has increased.

    As the global climate warms, all other things being equal, evaporation will increase and as a result, the hydrological cycle will accelerate.The downward trend of pan evaporation has been linked to a phenomenon called global dimming. In 2005 Wild et al. and Pinker et al. found that the “dimming” trend had reversed since about 1990 ”

    In fact, and in corroboration, a number of pluvial lakes that dried up 8000 years ago would be reborn if not for human use of the surface waters.

    http://en.wikipedia.org/wiki/Lake_Lahontan

    “Surprisingly, the watershed feeding Lake Lahontan is not thought to have been significantly wetter during its highstand than it is currently. Rather, its desiccation is thought to be mostly due to increase in the evaporation rate as the climate warmed. Recent computer simulations (using the DSSAM Model and other techniques) indicate that if precipitation and evaporation rates within the watershed were maintained at their historical yearly maximum and minimum, respectively and if diversions of the Truckee River ceased, the Ice Age extent of Lake Lahontan could return.”

  74. TomB says:
    I believe you are correct that Scotland will have a different local climate than other places.
    #############
    Climate

    http://en.wikipedia.org/wiki/Climate

    Climate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods. Climate can be contrasted to weather, which is the present condition of these elements and their variations over shorter periods.

  75. Rattus says:

    “Y’all might want to read what one of Anthony’s co-authors has to say on this topic.” (http://blog.chron.com/climateabyss/2011/09/texas-drought-and-global-warming/)

    Yes, we all might want to do exactly that. You probably wouldnt want to read it, which perhaps explains why you apparently did not. It contains the following conclusions, which clash dramatically with your alarmist world view:

    Precipitation: The balance of evidence does not support the assertion that the rainfall deficit since October 2010 was made larger or more likely by global warming.

    So, 0% the Texas drought was caused by ‘global warming’, from any source.

    Temperature: Compared to long-term averages of summer temperature, the rainfall deficit accounted for about 4 F of excess heat and global warming accounted for about 1 F of excess heat. Warmer temperatures lead to greater water demand, faster evaporation, and greater drying-out of potential fuels for fire. Thus, the impacts of the drought were enhanced by global warming, much of which has been caused by man.

    So, 80% of the increased Texas temperature during the drought was not caused by ‘global warming’ from any source. Only 20%, less than 1 degree F, of the Texas summer heat was caused by ‘global warming’ from all sources. This means that only some fraction of one degree F of the Texas summer heat, if any at all, could possibly be attributed to ‘global warming’ from anthropogenic sources. Thus, the magnitude of the obligatory claim of possible ”enhancement” of the Texas drought by anthropogenic greenhouse gases is certainly very small, likely very very small, and may in fact be zero.

    Thanks for directing us’all to that. It is nice to have corroberation for our view that anthropogenic ‘global warming’ doesn’t warrant a rats ass of genuine concern, even regarding extreme weather events.

  76. @Richard S Courtney
    No, not a meme but a deliberate strategy. Get the lie out first – by the time it’s rebutted, the LSM has broadcast it world-wide, and moved on to other things.
    ‘A Lie Can Be Halfway Round the World Before the Truth Has Got Its Boots On’.

  77. The CAGW spinmeisters strike me as being on the same level as ambulance-chasing lawyers when they go off linking natural disasters to their hobgoblin. There are real people dealing with real world problems and all these creeps can do is take advantage of their distress to try and scare them more. Pawns in their game to score political points. Since the lawsuit against companies for causing hurricane Katrina failed maybe the shyster scientists will encourage one for drought & wildfires. And a hockey stick will descend from the heavens proving this is the worst in 2000 years!

  78. Bill says:
    September 14, 2011 at 11:33 am
    Interesting, David. Thank-you for the response. So 2011 wasn’t a record for precipitation in Texas?

    2011 set the record low for summer precipitation in Texas.
    2007 was the record high for summer precipitation in Texas.
    2007 was the record maximum excursion (absolute value) from the average summer precipitation in Texas.

    All three records were the fifth records set for their respective time series.

  79. Roger Sowell says:
    September 13, 2011 at 9:19 pm
    @ AusieDan, re

    “Rainfall is NOT normally distributed.”

    What is your basis for that statement? I just now ran a histogram of annual precipitation in Texas, using the same data as my comment above, from NCDC since 1895 and obtained a curve that is very nearly bell-shaped. It is not a perfect Gaussian curve, but it’s not far off, either.

    see http://tinypic.com/r/olog7/7

    I looked at the histogram, and while it does bear resemblance to a normal distribution, my opinion is that the tails look a little fat to be truly normal. In other words, extreme events occur more frequently than one might expect from a gaussian PDF. However, to settle the argument for this particular series of data, perhaps you should test the normality of this histogram. There are not many geophysical records of any sort that display a normal distribution. We encounter lognormal or hyperbolic distributions often.

  80. Interestingly, using the same technique and same data source, there have been 8 new record highs for temperature and only 3 new record low temperatures in this same period. This would seem to be rather clear evidence SUPPORTING climate change.

    Not only was this year a record high, it was “off-the-charts” high. 86.6 F is 3.8 standard deviations above the mean, which is beyond 0.001 chance for a normal distribution. (Yes, I know this will not necessarily be a normal distribution, but there is no way to consider this anything but an extreme event)

  81. Gary Pearse says:
    September 14, 2011 at 8:53 am

    Roy treating records as a set of incremental numbers that have been randomized and assuming the first number in the randomized set is a record,the number of records to be expected is equal to: ln n where n= the number in the set or number of years in this case. Your graph certainly shows the log function and ln 120 does equal 4.8 (your 5 records).

    No, i believe it is a summation of the harmonic series, not a logarithm.
    1 + 1/2 + 1/3 + 1/4 …..

    That said, I disagree with David’s numbers a bit (although I like them better than the ln approximation). I think the numbers David gives are for the first year when a new record might be expected, not the typical year when a record might be expected. The mostly likely year should be the year the line on the graph crosses the various integers, not the year the line is at least 1/2 way to the next integer.

    Here are the first, typical, and last years to expect a new record

    1895-1895-1895
    1896-1898-1900
    1901-1905-1912
    1913-1924-1944
    1945-1977-2030
    2031-2120-2266

  82. David Middleton says:
    September 14, 2011 at 12:33 pm

    2011 set the record low for summer precipitation in Texas.

    All three records were the fifth records set for their respective time series.

    Actually, 2011 was the 6th record low for rainfall.
    1895 10.12
    1896 4.65
    1910 4.29
    1934 3.73
    1956 3.48
    2011 2.44

    Not only that but it was an unusually large change. As more records get set, the change should be getting smaller (if nothing else, eventually the record will be close to zero and the next record can only be slightly closer to zero. Other than the very first change, this is the largest change in the record. This would suggest that 2011 was indeed an unusually bad summer drought.

  83. @Tim Folkerts,

    Even if this was the 6th record low, the 4th record low missed its expected year by an even wider margin.

    Year of Record vs Expected Year

    1895 10.12 1895 – On time.
    1896 4.65. 1896 – On time.
    1910 4.29. 1901 – 9 years late.
    1934 3.73. 1913 – 23 years late.
    1956 3.48. 1945 – 11 years late.
    2011 2.44. 2031 – 20 years early.

    There is no expectation for a pattern of diminishing variability in an iid random series… Or even in a short stochastic series of such a short record length.

  84. @Kevin Kilty, re test for normality for histogram onTexas annual precipitation since 1896.

    I’m using the standard statistics from Microsoft Excel (TM) so have the kurtosis and skewness. Kurtosis for this histogram at 0.298, rounded to 0.3, and skewness is 0.188, rounded to 0.2. Therefore, the data set is very close to a Normal Distribution, with the positive skewness indicating a slight emphasis to the right, compared to a Normal Distribution.

    I looked in detail at the data, and found that the data points less than the median were as close to a Normal Distribution as one could expect with such a low population (116 data points).

    Compared to a perfect distribution (Normal Distribution), the number of data points below the mean are as follows:
    Perfect . . . . . .Actual
    Minus 1 Sigma . . . . . 39.5 . . . . . . .39
    Minus 2 Sigma . . . . . 15.8 . . . . . . .17
    Minus 3 Sigma . . . . . 2.4 . . . . . . . 2

    And, the number of data points above the mean:

    Perfect . . . . . .Actual
    Minus 1 Sigma . . . . . 39.5 . . . . . . .44
    Minus 2 Sigma . . . . . 15.8 . . . . . . .10
    Minus 3 Sigma . . . . . 2.4 . . . . . . . 4

    What is interesting to me, since this thread is about drought in Texas, is the 3-sigma value on the low end, the drought side. 3-Sigma is 12.8 inches of rain, compared to the lowest measured rainfall in the data set of 14.8 inches. There have been only 2 years out of the 116 years on record where rainfall fell between 2-Sigma and 3-Sigma on the drought side; a totally normal occurrence. For any alarm to be sounded legitimately, there must be either more years of 3-Sigma rainfall (less than 17.9 inches), or a year in the 4-Sigma (less than 7.75 inches), or both.

    I do have some doubts about this data, though, and pose a question to the WUWT audience if anyone knows the answer. The first is how accurate is this data, since there is a prolonged and severe drought in Texas, yet the data from NCDC shows only one year below average since 2004? The second is, how can the data already show a value for 2011, with 3 -1/2 months yet to go in the year? NCDC has the annual rainfall for Texas at 27.95 inches for 2011. I suspect the answer to the second question is that the data shows the 12-month period starting in February and ending in January. Thus, the 2011 data actually is ending in January 2011

  85. David Middleton says: “September 14, 2011 at 7:17 pm There is no expectation for a pattern of diminishing variability in an iid random series… Or even in a short stochastic series of such a short record length.”

    Sure there is such an expectation in many data sets – although the size of the effect depends on the distribution. This effect is strongly obvious in a uniform distribution (which is indeed iid). For data that could fall between 0-1, the first change will on average be fairly large — around 1/3. After a few records, the record will be above 0.9 and it will be impossible to get change of 1/3. The change HAS TO get smaller and smaller.

    For a normal distribution, there is no upper bound, so the expectation of diminishing returns is not so clear. But a check of 8 series of 10,000 random normal data (typically including ~ 8 new records) that shows:
    * 1 set had a slight trend toward larger changes, while 7 had stronger trends toward larger values
    * all sets had the smallest change in the second half of the records.
    * all but 1 set had the largest change in the first 2 records.

    Those all sound like trend to have the large changes early and the small changes later.

  86. Austin quotes from wikipedia computer model simulations of historical precipitation and evaporation levels, etc. that “…the Ice Age extent of Lake Lahontan could return.” If those computer models incorporated a return of another Ice Age and its following interglacial, then they would definitely show Lake Lahontan returning; but, no one needs a computer model to predict that, as a general knowledge of climate change will suffice. Also, the memories left by my great, great grandfather indicate that Lake Lahontan was nowhere to be found during his time, which was well before the waters of the Truckee River were diverted, and Indians freely roamed the land.

  87. Thanks, David, for this lucid and informative post. I’m sure you’re aware, but some readers here may not be, that the source you quote for the probability distribution equation (Benestad, 2003) is now a member of the Real Climate team. Some (although maybe not all) members of that team seem to have been quite capable of doing worthwhile and objective science. It’s sad that they are now devoting so much effort to the intolerant advocacy campaign centred round the demonstrably corrupt IPCC. What a waste of talent!

  88. oops … In the last post I meant

    * 1 set had a slight trend toward larger changes, while 7 had stronger trends toward larger values smaller changes.

    The one trend toward larger values was not statistically significant. A couple of the trends toward smller values were statistically significant.

    The point is that after you have already set a number of records, it becomes harder to break the record, so the change will tend to get smaller. (There is one statistical distribution where I suspect this might not be true, but it is a distribution that is mostly of academic interest – http://itl.nist.gov/div898/handbook/eda/section3/eda3663.htm)

    Of course, if the distribution changes, then this will no longer be true. So, for example, if climate truly is getting warmer, then the new records might not show this diminishing trend.

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