Australia's Relatively Stable Rainfall

The “State of the Climate” report from two of Australia’s lead agencies, the Bureau of Meteorology (BoM) and CSIRO, states that total rainfall has been “relatively stable” last century, but omitted their own data that clearly shows total rainfall increasing.

rranom.aus.0112.20873

The fine print at the bottom of BoM graph says rainfall has increased at the “relatively stable” rate of 6.3mm per decade. On downloading the data and fitting a linear regression, the upwards slope is significantly greater than zero as follows.

Slope=0.63 S.E.=0.23 P=0.003

When autocorrelation is taken into account the values are

Slope=0.63 S.E.=0.29 P=0.014

The Chow break-test shows a significant break in 1971-72, when annual rainfall increased by 60mm. This is a 13% increase in “relatively stable” rainfall (from 432±9mm to 492±15mm per annum).

fig10

How many ways this BoM statement not match observations?

A slight increase in Australian annual mean rainfall is evident during the 20th Century although this is largely due to several wet years during the 1970s. The five year mean rainfall also shows a weak upward trend. However, the high year-to-year variability of Australian rainfall dominates any background trends.

How Much More Rain Will Global Warming Bring? This is the question asked by Frank J. Wentz. The fundamental physical relation of evaporation and temperature called the Clausius-Clapeyron relation suggests a 6% increase in evaporation per K of temperature increase, also by Wentz’s analysis. If the ocean is not to migrate into the sky, evaporation has to equal precipitation globally (although not locally) and also increase by a “relatively stable” 6% globally.

But Wentz found the climate simulation models predict an “absolutely stable” increase in precipitation of only 1-3%, although a comment on the paper says the precipitation across all models is “relatively unstable” anyway, and so can’t really be trusted.

CSIRO and BoM experts, computer simulation models, the laws of physics, and observational data — two of these belong together, two of these don’t. Can you guess which ones?

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0 thoughts on “Australia's Relatively Stable Rainfall

  1. Interestingly, the shift circa 1972 is close to a shift that occurred about 1968 in thunderstorm days in SE Australia:

    Davis, S and K.J.E. Walsh. 2008. Southeast Australian thunderstorms: Are they increasing in frequency? Australian Meteorological Magazine, 57, 1-11.

  2. Interestingly, the shift circa 1972 is close to a shift that occurred about 1968 in thunderstorm days in SE Australia:Davis, S and K.J.E. Walsh. 2008. Southeast Australian thunderstorms: Are they increasing in frequency? Australian Meteorological Magazine, 57, 1-11.

  3. David, you persistently mis-state things. They didn’t say
    total rainfall has been “relatively stable” last century
    They said:
    While total rainfall on the Australian continent has been relatively stable, the geographic distribution of rainfall has changed significantly over the past 50 years.
    The only time period mentioned is the last 50 years. And “relatively stable” means stable relative to the changes in distribution.

    • The break occurred after 1960, where rainfall increased 13% after 1972.

      Even allowing for your generous interpretation, its still misleading.

    • Again, Nick, they have about a hundred years worth of data. Why would they only use half of it?

      One can only conclude that it was self serving to avoid putting the last 50 years in context.

    • Nick, you offer two possible interpretations:

      1. “While total rainfall on the Australian continent has been relatively stable [over the past 50 years], the geographic distribution of rainfall has changed significantly over the past 50 years.”

      2. “The total rainfall over Australian continent has been stable relative to the geographic distribution of rainfall that has changed significantly over the past 50 years.”

      The first is incorrect as shown above, the second is meaningless as total rainfall is not directly comparable with the distribution. Even BoM wouldn’t say that.

      • I didn’t offer two interpretations. The first is the obvious one.

        The parsing that goes on here is ridiculous. The paper simply remarked that over the last fifty years there have been divergent trends in N and S, while the total hasn’t changed so much. It’s a perfectly reasonable observation which they can make without any obligation to provide a ream of graphs covering every possible time period that you might prefer to think about. And they don’t have to anticipate your eccentric breakpoint theories.

      • Nick, all I want is for changes to be put in the fullest possible context. There is no justification for talking about the last fifty years when you have a hundred or so worth of data. Unless you want to give a misleading impression in the report about the nature of long term changes. In the US, our CCSP reports tried this same BS of focusing on recent decades. They showed trends since the 1970’s. Surprise, surprise! We can “hide the decline” in temperatures in the Southeast. We can show precipitation decreases in places-but if we use the full dataset, precip is going up almost everywhere.

        You can get certain impressions about the changes that have been going on. But the global warming that this might get blamed on happened over a full century-and using all the data can completely change the conclusion you reach. the conclusion that parts of Australia are getting wetter and parts drier is largely wrong over the long term. But this report evades telling the whole truth in favor of half truths.

      • Nick, I am trying to understand what you are saying, and you seem to agree with the confused and subjective interpretation by saying: “The paper simply remarked that over the last fifty years there have been divergent trends in N and S, while the total hasn’t changed so much [as the distribution].”

        Is it too much to ask BoM to be objective? Acknowledging that rainfall is increasing would support their argument that climate is changing. But it makes them look afraid to contradict Flannery, the Climate Adaptation Flagship and statements by other prominent researchers.

  4. David, you persistently mis-state things. They didn't saytotal rainfall has been “relatively stable” last centuryThey said:While total rainfall on the Australian continent has been relatively stable, the geographic distribution of rainfall has changed significantly over the past 50 years.The only time period mentioned is the last 50 years. And “relatively stable” means stable relative to the changes in distribution.

  5. The break occurred after 1960, where rainfall increased 13% after 1972.Even allowing for your generous interpretation, its still misleading.

  6. Around 1970 – 71 roughly coincides with the onset of the great 'Transmigrasi' programs which have resulted in the massive settlement of much of the outlying areas of Indonesia (and a vastly increased level of human waste pollution of the shallow, warm, coastal shelf waters of the Indonesian Archipelago).Around 1970 – 71 is also when the practice of setting major forest and peat fires which burn for long periods in East Kalimantan and (later) West Papua got under way.

  7. Again, Nick, they have about a hundred years worth of data. Why would they only use half of it?One can only conclude that it was self serving to avoid putting the last 50 years in context.

  8. Nick, you offer two possible interpretations: “While total rainfall on the Australian continent has been relatively stable [over the past 50 years], the geographic distribution of rainfall has changed significantly over the past 50 years.””The total rainfall over Australian continent has been stable relative to the geographic distribution of rainfall that has changed significantly over the past 50 years.”The first is incorrect as shown above, the second is meaningless as total rainfall is not directly comparable with the distribution.

  9. I didn't offer two interpretations. The first is the obvious one.The parsing that goes on here is ridiculous. The paper simply remarked that over the last fifty years there have been divergent trends in N and S, while the total hasn't changed so much. It's a perfectly reasonable observation which they can make without any obligation to provide a ream of graphs covering every possible time period that you might prefer to think about. And they don't have to anticipate your eccentric breakpoint theories.

  10. Nick, all I want is for changes to be put in the fullest possible context. There is no justification for talking about the last fifty years when you have a hundred or so worth of data. Unless you want to give a misleading impression in the report about the nature of long term changes. In the US, our CCSP reports tried this same BS of focusing on recent decades. They showed trends since the 1970's. Surprise, surprise! We can “hide the decline” in temperatures in the Southeast. We can show precipitation decreases in places-but if we use the full dataset, precip is going up almost everywhere.You can get certain impressions about the changes that have been going on. But the global warming that this might get blamed on happened over a full century-and using all the data can completely change the conclusion you reach. the conclusion that parts of Australia are getting wetter and parts drier is largely wrong over the long term. But this report evades telling the whole truth in favor of half truths.

  11. Nick, I am trying to understand what you are saying, and you seem to agree with the confused and subjective interpretation by saying: “The paper simply remarked that over the last fifty years there have been divergent trends in N and S, while the total hasn't changed so much [as the distribution].”Is it too much to ask BoM to be objective? They seem to be trying to bolster the Flannery, Rudd, etc Australia getting drier lobby by not bringing themselves to state the facts.

  12. Regarding eccentric break point theories:Trends in warm season thunderday incidence are examinedover southeastern Australia. There has been a significantincrease in the number of thunderdays from 1941-2004, but much of this increase may have been a result of changes in observing practices in the mid 1950s. When data earlier than this are removed, some significant trends remain. There have also been smaller increases since 1970, mostly in the early part of the warm season (October-December). These increases mayhave been caused by changes in the atmospheric processes that affect this region. Examination of temporal trends in surface and 500 hPa temperatures and several instability indices since 1970 showed an increase in temperature and an increase in the number of days that instability is present in the atmosphere, asmeasured by the Total Totals index. It is unclear whether these increases are caused by localised phenomena or changes in some larger scale meteorological processes caused by climate change or other large-scale processes. Significant issues remain regarding the homogeneity of the thunderday record.Davis, S and K.J.E. Walsh. 2008. Southeast Australian thunderstorms: Are they increasing in frequency? Australian Meteorological Magazine, 57, 1-11.http://www.bom.gov.au/amm/papers.php?year=2008http://reg.bom.gov.au/announcements/media_relea

    • “2. In six of the ten cases examined the best fitting
      models were not a simple linear fit but involved break-
      points. Two of the four cases in which linear models were
      chosen were for the troposphere during 1979 – 2001, a
      period in which we identified no potential breakpoints.

      [34] 3. The frequent choice of the sloped steps and flat
      steps models highlights the importance of abrupt changes.
      The choice of the sloped steps model for the tropospheric
      data suggests it is reasonable to consider most of the
      warming during 1958 – 2001 to have occurred at the time
      of the climate ‘‘regime shift,’’ modeled here at the start of
      1977.”

      Nick must be using a definition of eccentric that means selected by objective statistical criteria, the opposite of which is denial.

    • Well, the concensus is that Lindzen is eccentric 🙂 And Swanson is a mathematician! And Seidel & L also say:
      [38] Although we have combined several statistical techniques to select models in an objective fashion, the reader should be aware that our approach involves some underlying assumptions and is based on some subjective decisions.

      So not so objective. It’s OK to play with this stuff, but you can’t expect that CSIRO etc will modify their wording to accommodate anyone who might find a breakpoint somewhere.

  13. A picture is worth a thousand words
    Rainfall

    The decade ending 2009 was the second wettest on record for the whole of Australia, with the decade ending 1979 the wettest, unless the official figures are revised.

    • “…..unless the official figures are revised.”

      Yes, you are right. Technically it more difficult to estimate (or fiddle) regional rainfalls than regional (min/max) temperatures.

      No doubt someone is working on the problem (;-).

      • Steve, I want to put rainfall on the table. From my biodiversity background its just as important as temperature, economically the extremes are more costly than temperature, but its ignored or exploited. But the story is actually full of conundrums and illustrates how little is understood by the ‘experts’.

  14. “2. In six of the ten cases examined the best fitting models were not a simple linear fit but involved break- points. Two of the four cases in which linear models were chosen were for the troposphere during 1979 – 2001, a period in which we identified no potential breakpoints. [34] 3. The frequent choice of the sloped steps and flat steps models highlights the importance of abrupt changes. The choice of the sloped steps model for the tropospheric data suggests it is reasonable to consider most of the warming during 1958 – 2001 to have occurred at the time of the climate ‘‘regime shift,’’ modeled here at the start of 1977.”Nick must be using a definition of eccentric that means selected by objective statistical criteria. The opposite of eccentric being vested interest in green energy and carbon trading.

  15. “…..unless the official figures are revised.”Yes, you are right. Technically it more difficult to estimate (or fiddle) regional rainfalls than regional (min/max) temperatures.No doubt someone is working on the problem (;-).

  16. Steve, I want to put rainfall on the table. From my biodiversity background its just as important as temperature, economically the extremes are more costly than temperature, but its ignored or exploited. But the story is actually full of conundrums and illustrates how little is understood by the 'experts'.

  17. David, I’d like to put rainfall into more prominence too, but there were significuant problems with evaporimeters (birds splashed in them) and there is a lack of data about water table depths IIRC. So the balance is hard to reconstruct.

    In an early way, I wonder if there is also value in global atmospheric pressure distribution with time. The total weight of air should stay quite constant in 100 years, with changes due mainly to the water content carried and turbulence. Re the 10 year drought in SE Australia, maybe there has been a 10 year reduction in atmospheric pressure because the air has become less moist. If not, why not? Then it feeds back into Dick Lindzen’s global work. I am unsure if this is treading on old ground, so please tell me so.

  18. David, I'd like to put rainfall into more prominence too, but there were significuant problems with evaporimeters (birds splashed in them) and there is a lack of data about water table depths IIRC. So the balance is hard to reconstruct.In an early way, I wonder if there is also value in global atmospheric pressure distribution with time. The total weight of air should stay quite constant in 100 years, with changes due mainly to the water content carried and turbulence. Re the 10 year drought in SE Australia, maybe there has been a 10 year reduction in atmospheric pressure because the air has become less moist. If not, why not? Then it feeds back into Dick Lindzen's global work. I am unsure if this is treading on old ground, so please tell me so.

  19. Well, the concensus is that Lindzen is eccentric 🙂 And Swanson is a mathematician! And Seidel & L also say:[38] Although we have combined several statistical techniques to select models in an objective fashion, the reader should be aware that our approach involves some underlying assumptions and is based on some subjective decisions.So not so objective. It's OK to play with this stuff, but you can't expect that CSIRO etc will modify their wording to accommodate anyone who might find a breakpoint somewhere.

    • Tom Quirk, who is a nice guy
      Indeed. He was my physics tutor once.
      Are you really saying there was not a climate shift in 1976
      I didn’t say that. But I don’t think anything useful follows from such a belief. You can apply Chow tests to all sorts of data, and find many breakpoints. DS likes doing that, but how does it help?

      • Nick

        “You can apply Chow tests to all sorts of data, and find many breakpoints. DS likes doing that, but how does it help?”

        That is a good question but the fact remains that there certainly appears to have been (some sort of) marked climate shift evident in the Northern Territory in the 1970s as evidenced by:

        Annual Rainfall Anomaly
        Annual Percentage Area in Decile 10 Rainfall
        Annual Sea Surface Temperature Anomaly

        (all BOM data).

        The fact that this shift seems to bear little relationship to the intensity of EITHER the East Asian Monsoon or of the El Nino/La Nina cycles (although the latter is clearly imposed on the shift) of the last 30-odd years has always struck me a rather curious.

        The facts that this did coincide with the explosive growth in the Indonesian ‘Transmigrasi’ program of the 1970s – 1990s (with its consequences for primary productivity of coastal waters) AND the onset (from ~1970) of frequent, major, persistent forest and peat fires in East Kalimantan and (later) West Papua (with its consequences for aerosol effects) have also always struck me as rather curious.

        The orthodoxy generally seems overly keen to ascribe anthropogenic climate effects to CO2 but reluctant to ascribe them to any other significant anthropogenic phenomena (temporary or long lived) – other than black carbon aerosols of course.

  20. David,
    I would much appreciate you putting rainfall on the table.
    Will not ‘missing data’ (both open and hidden) be a bigger issue with rainfall than it is with temperature?

    I have no idea how good the modern day rainfall reports are. But as for historical records I have no doubt that rainfall has been higher than what BOM reports. How much is the question.

  21. David,I would much appreciate you putting rainfall on the table.Will not 'missing data' (both open and hidden) be a bigger issue with rainfall than it is with temperature? I have no idea how good the modern day rainfall reports are. But as for historical records I have no doubt that rainfall has been higher than what BOM reports. How much is the question.

  22. Tom Quirk, who is a nice guyIndeed. He was my physics tutor once.Are you really saying there was not a climate shift in 1976I didn't say that. But I don't think anything useful follows from such a belief. You can apply Chow tests to all sorts of data, and find many breakpoints. DS likes doing that, but how does it help?

  23. Of course, rainfall has the advantage over temperature that if you lose a few days of observations the rain remains in the gauge and can be reconstructed a lower resolution, while for Hg temperatures the thermometer would stay set at extrememe max/min over those days, so more data would be lost.

    • Geoff,
      The missing months may be an issue. When months of data can disappear one can only speculate about days.

    • Geoff,
      As an example have a look at Duaringa (Qld).
      October, November, December 1889.
      The first half of the wet season for that region.
      Other stations in the region (Marlborough, Rolleston, Emerald, Springsure, Banana) are running 60-70% above average for the 3 months. Putting rainfall in/near the top quartile for that period.
      Duaringa has not just its lowest rain for the period- it has no rain.
      BOM has given it a tick.
      How often is this type of error repeated in the BOM data?
      What other types of error might there be?

  24. Of course, rainfall has the advantage over temperature that if you lose a few days of observations the rain remains in the gauge and can be reconstructed a lower resolution, while for Hg temperatures the thermometer would stay set at extrememe max/min over those days, so more data would be lost.

  25. Glassman is good value.

    Nick; the 1976 date tallies with PDO phase shift and a host of oceanographic factors; temperature rose rapidly over the transition period; how is it not reasonable to show that the temperature history is stepped rather than incremental per linear regression when the incremental depiction falsely supports a gradualist AGW effect; or are you saying that AGW can have a step effect on temperature. If not the step or break approach to temperature is a valid rebuttal of AGW; if temperature trend is not consistent with AGW then AGW is moot.

    • It isn’t a rebuttal of AGW; it’s just saying (if true) that something happened that had a stepped effect.

      Yes, I agree that there’s a place for looking for steps when you have reasonable belief in a mechanism that would cause them. But these things feed on each other. An ocean oscillation like PDO doesn’t normally imply steps. A change of sign of a phase isn’t a step, but people see that and go looking regardless.

      • “It isn’t a rebuttal of AGW; it’s just saying (if true) that something happened that had a stepped effect.”

        Do any climate models produce similar behavior? If not it seems that these step like changes have great relevance for the “attribution” argument.

  26. Glassman is good value.Nick; the 1976 date tallies with PDO phase shift and a host of oceanographic factors; temperature rose rapidly over the transition period; how is it not reasonable to show that the temperature history is stepped rather than incremental per linear regression when the incremental depiction falsely supports a gradualist AGW effect; or are you saying that AGW can have a step effect on temperature. If not the step or break approach to temperature is a valid rebuttal of AGW; if temperature trend is not consistent with AGW then AGW is moot.

  27. Nick”You can apply Chow tests to all sorts of data, and find many breakpoints. DS likes doing that, but how does it help?”That is a good question but the fact remains that there certainly appears to have been (some sort of) marked climate shift evident in the Northern Territory in the 1970s as evidenced by:Annual Rainfall AnomalyAnnual Percentage Area in Decile 10 RainfallAnnual Sea Surface Temperature Anomaly(all BOM data).The fact that this shift seems to bear little relationship to the intensity of EITHER the East Asian Monsoon or of the El Nino/La Nina cycles (although the latter is clearly imposed on the shift) of the last 30-odd years has always struck me a rather curious.The facts that this did coincide with the explosive growth in the Indonesian 'Transmigrasi' program of the 1970s – 1990s (with its consequences for primary productivity of coastal waters) AND the onset (from ~1970) of frequent, major, persistent forest and peat fires in East Kalimantan and (later) West Papua (with its consequences for aerosol effects) have also always struck me as rather curious.The orthodoxy generally seems overly keen to ascribe anthropogenic climate effects to CO2 but reluctant to ascribe them to any other significant anthropogenic phenomena (temporary or long lived) – other than black carbon aerosols of course.

  28. Glassman is good value.

    Nick; the 1976 date tallies with PDO phase shift and a host of oceanographic factors; temperature rose rapidly over the transition period; how is it not reasonable to show that the temperature history is stepped rather than incremental per linear regression when the incremental depiction falsely supports a gradualist AGW effect; or are you saying that AGW can have a step effect on temperature. If not the step or break approach to temperature is a valid rebuttal of AGW; if temperature trend is not consistent with AGW then AGW is moot.

  29. Glassman is good value.Nick; the 1976 date tallies with PDO phase shift and a host of oceanographic factors; temperature rose rapidly over the transition period; how is it not reasonable to show that the temperature history is stepped rather than incremental per linear regression when the incremental depiction falsely supports a gradualist AGW effect; or are you saying that AGW can have a step effect on temperature. If not the step or break approach to temperature is a valid rebuttal of AGW; if temperature trend is not consistent with AGW then AGW is moot.

  30. Geoff,The missing months may be an issue. When months of data can disappear one can only speculate about days.

  31. It isn't a rebuttal of AGW; it's just saying (if true) that something happened that had a stepped effect.Yes, I agree that there's a place for looking for steps when you have reasonable belief in a mechanism that would cause them. But these things feed on each other. An ocean oscillation like PDO doesn't normally imply steps. A change of sign of a phase isn't a step, but people see that and go looking regardless.

  32. “It isn't a rebuttal of AGW; it's just saying (if true) that something happened that had a stepped effect.”Do any climate models produce similar behavior? If not it seems that these step like changes have great relevance for the “attribution” argument.

  33. Geoff, As an example have a look at Duaringa (Qld).October, November, December 1889.The first half of the wet season for that region.Other stations in the region (Marlborough, Rolleston, Emerald, Springsure, Banana) are running 60-70% above average for the 3 months. Putting rainfall in/near the top quartile for that period.Duaringa has not just its lowest rain for the period- it has no rain.BOM has given it a tick.How often is this type of error repeated in the BOM data?What other types of error might there be?

  34. Since I last downloaded the rainfall data for Springsure (Qld – Station number 035065) in November 2008 there have been 16 new additions to the dataset.
    1971 -Jan, Feb
    1972 – Dec
    1973 – Jan
    1975 – Mar, Apr
    1985 – Dec
    1986 – Aug, Sep, Oct, Nov
    1987 – Oct, Nov
    1991 – Mar, Apr
    1995 – Dec

    There have also been two minor corrections to June 2005 and January 2008. Both of which previously had the BoM quality tick.
    Good to see BoM is working on the historical datasets.

  35. Since I last downloaded the rainfall data for Springsure (Qld – Station number 035065) in November 2008 there have been 16 new additions to the dataset.1971 -Jan, Feb1972 – Dec1973 – Jan1975 – Mar, Apr1985 – Dec1986 – Aug, Sep, Oct, Nov1987 – Oct, Nov1991 – Mar, Apr1995 – DecThere have also been two minor corrections to June 2005 and January 2008. Both of which previously had the BoM quality tick.Good to see BoM is working on the historical datasets.

  36. Since I last downloaded the rainfall data for Springsure (Qld – Station number 035065) in November 2008 there have been 16 new additions to the dataset.1971 -Jan, Feb1972 – Dec1973 – Jan1975 – Mar, Apr1985 – Dec1986 – Aug, Sep, Oct, Nov1987 – Oct, Nov1991 – Mar, Apr1995 – DecThere have also been two minor corrections to June 2005 and January 2008. Both of which previously had the BoM quality tick.Good to see BoM is working on the historical datasets.

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