Jen,
I’ve noticed your recent thread on the long-term hydrological drought affecting eastern Australia. I’ve whipped off a few charts for you which put this into an historical context based on rainfall data going back to 1900 (some limited earlier data is available).
In terms of eastern Australia, the current meteorological drought started in early 2002 with the emergence of an El Nino event and continues to the present. The first figure below shows essentially drought “deciles” for this period.
As you can see a significant part of SE Queensland has experience its driest 55 month period on record. The data are not spatially dense enough to resolve structures at the catchments scales (though Warwick’s graphs suggest ~5 yearly rainfalls which are lowest on record).
Note that the analysis only shows those areas which are experiencing severe or serious meteorological drought (almost all of eastern Australia has experienced below average rainfall through this period).
Rainfall is only part of the drought story (drought is a function of both water supply and water demand), but it does support the general conclusion that it has been abnormally dry and probably the driest period in “of order” 100 years.
This is just one of three protracted drought periods which Australia is experiencing. Probably the most important from a water management perspective is that which started in early 1997/late 1996 in southern Australia. This is shown in the second figure.
This has seen the Perth, Canberra and Melbourne catchments all experience their lowest (or nearly so) rainfall on record. The third protracted drought event is that which commenced in SW Western Australia in the 1970s and which has been linked to a combination of greenhouse gas increases, ozone depletion and natural variability by the Indian Ocean Climate Initiative (see http://www.ioci.org.au/).
An aspect which is not covered in these analyses is the high temperatures. The third figures shows the mean temperature deciles for the period starting in 2002.
This analysis is based on the post 1950 period only (though temperatures before this time were generally considerably cooler) and uses only the high quality national temperature network discussed at http://www.bom.gov.au/climate/change/reference.shtml .
These stations have minimal or no urban heat island effects. There are a number of papers published on the increasingly warm temperatures which we now experience with droughts (as a result of global warming interacting with climate variability). As you can see almost everywhere has been warmer than average and most of Queensland has experienced its warmest 55 month period on record.
Regards,
David
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
All fine and dandy David, except it has no context. What percentage worse than previous worst is it? The claim is that we couldn’t have planned for what we are experiencing. These figures add little to the debate.
In my previous line of business as a property developer we allowed for once in one hundred year floods. Are you telling me that the Met Bureau and the State Government are behind the property development industry in terms of risk analysis?
David, are you able to get these maps freely off the Bureau of Meteorology website?
I know you can get all sorts of maps, but they usually have a max duration of 36 months for rainfall, and 12 for temp.
do you need to buy the CD or something to generate those custom maps?
Thanks,
Steve
Graham – oh it’s a bit worse. Of course you could have planned for it if you were a thoughtful proactive government. But I bet this hallowed blog would have been up those planners for the rent as Chicken Littles if you had raised this issue 5 years ago ! We usually get the politicians we deserve don’t we?
Why blame poll driven politicians about drought preparedness when Australia’s famers cannot manage climate variability unhindered. And there are opportunity costs for the money like hospitals and the power grid. For various reasons dam building has become unpopular with the urban electorates in the 90s and 00s – people don’t like change until they realise the jig is up and it’s crisis time. Drought is classic for this sort of logic. Most people hate reduced flow shower heads and want to hose the driveway ! Don’t bring logic into it.
By golly even more reason on your argument then to get proactive on climate change !
And if property developers are so high and mighty on flood management why are developers promoting massive development of housing in Brisbane and Ipswich flood plains e.g. south of Centenerary road bridge in Brisbane – Bundamba flood plain at Ipswich. I assume all the landholders have signed writs to never seek government assistance if ever flooded (not!). In terms of 1 in 100 – well bad choice of statistical concepts again – biggest event 1841 only 50 odd years to the 1893 sequence. Then two as big as 1974 a fortnight apart.
Wivenhoe’s flood compartment will save the current home-builders will be the answer – maybe – maybe not – we really know little our the true long-term flood statistics of the catchment.
http://en.wikipedia.org/wiki/Brisbane_River
http://www.bom.gov.au/hydro/flood/qld/fld_history/brisbane_history.shtml
If we want our governments to get proactive on planning for the future – let’s start the full list and tell them ! Most of the time they’re just attending to our poll driven whims.
Steve,
the tools which allow the user to develop maps such as these are not currently avaliable on the Bureau’s external website. They will be ported to the external web in the coming year all things going to plan.
Graham, you are entirely wrong about the lack of context. There analyses are referenced to the historical record and show without any ambiguity that certain aspects of this drought fall outside of our conventional observations. Whether it could be better planned for is entirely an issue of ones risk adversion and willingness to pay.
Regards
David
d.jones@bom.gov.au
Hi David, thanks, and thanks for the post – exactly the information that was needed to support the ‘evidence based’ discussion on this blog.
Looking forward to the inclusion of the additional tools for generating maps on the BOM website.
Steve
Wouldn’t it be more appropriate to suggest that these small portions of the country are taking their turn to go through their worst five year drought?
Forgive me, but didn’t I see a map with most of the country in white for being well within the historical range of variation? And doesn’t this imply that some other similar sized portion will be experiencing their worst five years in five years time?
Is it not a statistical certainty that 5% of the country will be experiencing a 5 percentile event?
Well be a little cautious in your assertion. David’s notes say “Note that the analysis only shows those areas which are experiencing severe or serious meteorological drought (almost all of eastern Australia has experienced below average rainfall through this period). ” Certainly looking at the BoM’s 12, 24 and 36 month decile maps shows a somewhat more extended drier than median area with those red areas above as epicentres.
BUT with no changes in underlying climate patterns – yes everywhere in Australia should experience low percentile rainfalls at some time. But are there underlying climate patterns? – and do we have enough rainfall records in just 120 odd years to sample the full distribution of extreme events (e.g. the north Qld coral cores and rainfall). Perhaps both may be true??
David also notes that there is some extensive science on some areas like SW WA .. .. ..”The third protracted drought event is that which commenced in SW Western Australia in the 1970s and which has been linked to a combination of greenhouse gas increases, ozone depletion and natural variability by the Indian Ocean Climate Initiative (see http://www.ioci.org.au/).”
Perhaps climate changes (natural and /or anthropogenic) are in motion with the whole southern hemisphere circulation and affecting eastern Australia too. What would you need to be convinced. Do you want the climate scientists to investigate?
Does anyone know how South Africa and South America are faring?
Ian, the discussion is about whether the conditions in SE Queensland are highly unusual. That argument is settled by the observational facts. Similarly, characteristics of the meteorological drought being experienced across almost all of eastern Australia are without precedent in our records.
There are well established techniques for determining the significance of spatial patterns which have been used in climate for around 25 years. If you wish to do the analysis, suggest you look at Robert E. Livezey and W.Y. Chen. 1983: Statistical Field Significance and its Determination by Monte Carlo Techniques. Monthly Weather Review: Vol. 111, No. 1, pp. 46–59.
David
d.jones@bom.gov.au
The maps suggest an astonishing level of misfortune regarding this drought. The area of serious deficiency (since 1997) seems to cover no more than 4% of the continent, yet this area includes maybe 60-70% of the nation’s population, if you count the Sydney catchment, which is either in serious deficiency or on the fringes of it. There are “direct hits” on Brisbane, Melbourne, Hobart, Canberra and Perth, with Sydney on the edge – six out of eight capitals. The probability of this happening (binomial), when 96% of the continenet is doing ok, is around 0.00001%. Is there something weird going on here?
I see your point Charles D, it does seem weird.
Just wanted to note though that white on the map doesn’t mean “ok”. It just means not in the bottom 10% on record.
For example, currently over 90% of NSW is drought declared, and much of NSW has been drought declared each month since the start of 2002.
See here:
http://www.agric.nsw.gov.au/reader/drt-area?picQuant=100
My only problem with that methodology, David, is that there are at least two weather stations, Logan and Strathpine, within the area mapped as severe deficiency that have managed to record a recent 12 month period of almost 20% above average rainfall.
And this can only mean that a set of more numerous data records have been added that counteract the positive records. There is clearly more recording stations in urban areas and this biases the outcomes in favour of those records.
The only way to produce an accurate map is to place weather stations at the centre of each grid square and only record those data sets. Obviously, the grid squares (pixels?) must be small enough to capture the variances.
And the question of drought should also be resolved in respect of soil moisture deficit rather than annual rainfall totals. For it is the extent of a soil moisture deficit that determines the food value of native vegetation and therefore the survival of dependent species.
Annual records can look impressive or very ordinary but both can mask contradictory outcomes. For example, the annual rainfall records for Eudlo on the Sunshine Coast show a fairly normal distribution of good and bad years between 1991 and 1997 but the compiled soil moisture data shows a completely different story.
Annual average over the 20 years from 1984 to 2004 was 1781mm while evaporation is 1950mm.
The annual totals for;
1991 was 1393mm (78.2%) of average
1992 was 2201mm (123.6%)
1993 was 1343mm (75.4%)
1994 was 1519mm (85.3%)
1995 was 1647mm (92.5%)
1996 was 1293mm (72.6%)
1997 was 1397mm (78.4%)
1998 was 1449mm (81.4%)
1999 was 3287mm (184.6%)
Only 1996 was in the second lowest decile so most observers would conclude that the wildlife have done reasonably well over that period.
But the data was then examined for soil moisure deficits. Each month with a surplus is deemed to provide a full profile to the following month from which that monthly rainfall is added and the monthly evaporation is deducted. So only the month after a low rainfall month actually experiences a significant deficit and is recorded as a soil deficit month.
In most cases one or two low rainfall months are not suffient to have a serious impact on habitat values and species survival. But longer periods certainly do.
This analysis revealed that the entire period from 1991 to 1997 had serious soil moisture deficits that lasted for a continuous six months each year. And in fact, 1992, the year of 123.6% of annual average rainfall actually had the worst season for wildlife with 7 continuous months of soil moisture deficit. The annual total was distorted by February and March totals of 812mm and 476mm respectively which masked a very bad season in a sequence that would have decimated populations of forest dependent fauna.
Interestingly, this soil moisture drought did not have to wait for the 1999 total of 3287mm to be broken. This had already been done by the 1998 total at only 81.4% of average but with each low rainfall month being followed by a compensating higher rainfall month that enabled transpiration and leaf moisture and nutrient levels to be maintained.
Which all goes to show that if you really want to know what sort of year it is, ask a farmer.
Yep – which is why crop and pasture models get used for serious analysis. Percentile yield or pasture growth distribution.
I have just added some comments on the BoM maps David posted plus three more rainfall graphics.
All at;
http://www.warwickhughes.com/drought/bom2006.htm
enjoy.
A timely story for you Warwick. this farmer says his rainfall records show the lowest level of rainfall in Penola since 1861.
http://www.abc.net.au/news/newsitems/200608/s1728004.htm
Warick,
Your analysis is does no take into account the seasonality of rainfall. What matters is have there been drier 115 month periods in the historical record starting in January which are drier than the present.
Penola and Yan Yean are not relevent to this discussion as they both appear to lie outside of the lowest on record.
Regarding the interpretation of deciles and gridded data suggest you look at http://www.bom.gov.au/climate/austmaps/mapinfo.shtml for a description of how the analyses are produced. The maps uses all avaliable monthly station data which has met a suitable level of quality control.
Regards,
David
d.jones@bom.gov.au
I must also add to the above post on soil moisture deficits that monthly data are not close enough to the problem for my liking. That is because there are many months like this current August in SEQ where there has been nothing for 28 days and then a dump of more than the mean in the last few days.
This would mean this month would be wrongly recorded as a non-deficit month with no carryover of soil moisture into September. True, it would all average out in a longer data set but that is no use to the little fuzzies.
Daily data would be a pain but weekly stuff would have to be compiled anyway so not much less work.
The other problem is with the assumption that evapotranspiration still takes place when there is no soil moisture to transpire, especially if combined with reduced tree or pasture leaf area at end of season due to grazing etc.
By the way, David, I noticed when looking up data for specific locations that the actual annual rainfall totals in 5th decile monthly data sets are often quite different to the annual mean. Is this because it is the sum of monthly 5th deciles not the annual 5th decile?
David, in my opinion you have introduced a red herring by claiming that there is some issue of “seasonality” which gets you off the hook that the Casterton data shoots a hole in the BoM “lowest on record” dark red zone of your Jan 1997 to Jul 2006 drought map in western Vic.
You selected this 115 month period, which incidentally includes 38 seasons !!
In any case, there are many 115 month periods ending in July that have lower rain than your Jan 1997-July 2006 period. For example, the 115 month periods ending Jul 1989, Jul 1988, Jul 1987, Jul 86 and Jul 1985, just to pull out a few recent cases.
I have known for years that BoM drought maps are often not congruent with the BoM HQ rainfall dataset and this instance of Casterton proves my point.
Steve, I have seen many examples of this style of “news” item and it is so rare for the data to back up the assertions. Putting aside for the moment that we have no idea about the quality of the Penola data being referred to. Lets assume the farmer is talking about January to August of this year.
The Penola Post Office BoM HQ data shows to date, 332.2 mm rain Jan to August for 2006. Now running a rolling average back we find there were lower Jan to Aug totals for the following years, 2005 304, 1997 309, 1982, 320.8, 1967 254.5, 1959 326.6, 1949 328, 1934 268.4, thats far enough.
Motty – argh – which is why you need a bloody daily time step runoff model mate. Cripes – we only have to punch data into a computer once but Ian ….
And argh II – means (meaning arithmetic means or averages) or medians mate !! Medians pls ! Oils ain’t oils – and means and medians.
Golly Warwick – we can tie ourselves up in knots with this rainfall stats. There is a point to the seasonality from a plant growth perspective. For example a dump of rainfall on a summer grwoing grass during a cold winter won’t do much. So it is appropriate that one adopts some window (unless it’s just front bar at the pub bragging rights type stuff).
If it’s streamflow and dam fill – well may be different to growth but we have vastly different evaporation rates at different times of the year which will effect runoff. Which is why you need to get to runoff if that’s what’s concerning you as the real issue.
There may be real reasons to exclude data or issues with data updating schedules.
You can tie yourself in too many knots with rainfall graphs and maps and miss the real issues.
The groan I make everytime I see a whole of Australia trend line. Are we providing useful statistics or just statistics.
Real issues for Queensland at least being
(a) what are we doing about dry dams
(b) what’s appropriate and responsible risk management for the future
(c) what does future climate variability (do we have enough background e.g. coral cores with more variability than now maybe), greenhouse and ozone depletion and maybe inter-decadal oscillations) imply for responsible future management
But of course this requires less ragging and a more positive forward research program !
I recall, some years back, the report on some coral cores suggested, periods of up to 25 years, where runoff each year, was less than any single year, experienced since settlement.
If this is the case, when it occurs again, apart from a huge furor of blame to global warming, just how long do you think it would take to decide to move the capital 1000Km to the north.
If industry can move to take advantage of resources, why can’t public servants.
But imagine Suncorp if cyclone Larry had ploughed through the middle of a new metropolis of Capricornia situated at around Innisfail level.
Don’t worry about the public servants Has-babes – many cut their teeth in these northern environments and are scheming how to return ! But to escape Bris-vegas – not rediscover it.
Anyway why muck around – let’s all relocate to Kununurra and have the Ord Dam.
So Luke, wouldn’t it be great to have the full career path to SES without having to come to babylon to get there? Wouldn’t it be great to deal with people who already know what is going on on the ground and who have not been transferred every 7 months? A small Capital, short commute, cheaper housing, the olds nearby, long weekends where you actually want to spend them, and a department where your efforts actually get noticed by those who count?
So when can I sign your whole work unit up for the new states campaign?
Actually Luke, the best thing anyone could do for QLD, would be to relocate the entire public service to East Timor, & then cut all communicination with the place.
Warwick,
once again I refer you to the webpage http://www.bom.gov.au/climate/austmaps/mapinfo.shtml . The rainfall analyses define the rainfall averaged into 25km grid cells. With such a cell there will be both higher a lower individual reports, but it is the average which counts.
This grid cell effect cuts both ways (for example Melbourne RO has had a record low rainfall which is not shown on the analysis).
Kind Regards,
David
d.jones@bom.gov.au
Sounds like Logan public servants have done you wrong Haso !
Ian – your logic is strangely compelling. I want to believe. Where do we sign. SES is a bit drastic though if you want to do something useful. Not necessary – just service to a grateful nation is enough.
Any thoughts on the very short span of time we are talking about here? I have read a few books about the first colonists to Australia and they all talk about drought. I know it may be drier than what we are used to but compared to what? 200 years of records at most?
Australia’s position under the high pressure zone of Hadley Cells makes drought the norm, not the exception.
I also note the spin placed on this drought by the green groups. Anyone remember when the first global warming scare was put out by environmentalists? They warned that Europe would heat up and told us that Australia was in for wetter weather due to increased evaporation. Well the Europeans thought warmer weather was Ok, and we welcomed rain. Then it changed to Australia getting drier and Europe getting colder as the planet warmed. It was designed to get a negative reaction.
In reality, Europe is warmer, and Australia is experiencing yet another drought, but Europe has records dating back to the Little Ice Age when the Thames River froze over allowing people to ice skate on it – anything warmer than that is therefore “record” warming, and Australia has it’s same old system of droughts and flooding rains.
Interestingly SEQ has just had its wettest August on record.
I think there are so many variables, including the sun which Greedpeace famously declared had nothing to do with global warming, and we could be experiencing a culmination of many cycles. I know the pre-industrial revolution levels of CO2 were not optimum because plants had to evolve to exist in an atmosphere that was carbon poor. There have been times in the past that had far higher concentrations of CO2 yet were wetter and more abundant in plant life.
I think all we can do is to source water from as many places as possible and use what we have sparingly.
Mike – I’m sure you don’t mean “wettest” for SEQ. It’s been dry as a chip.
Jeez Mike – you have done a cook’s tour of 12 months blog discussions on climate change in a couple of paras.
“Greenpeace famously declaring not the sun” – NO – it’s the IPCC and most enlightened climate scientists who have not found an increase in solar output over the last 30 years to explain the current warming.
CO2 enhancement only works if you have the soil water to go with it.
Warming is NOT the major driver of evaporation – try radiation, wind and vapour pressure deficit first. Many long term Australian evaporation instruments are showing declining trends in evaporation – thought be wind as the driver, global dimming elsewhere.
And in Australia it is not the “same old” system of droughts and flooding rains. We have had very few La Ninas since 1976 and many more El Ninos.
Read this blog’s climate archive !
Luke, I recall the CSIRO workshop on the impact of climate change on temperate forests was advised that the CO2 fertilisation effect was also associated with improve water use efficiency. That is why saplings growing on the exposed rock on road culverts seem to grow better than similar aged saplings in soil with moisture reserves but further from the exhaust emissions.
I continue to be surprised by the persistent belief that CO2 is a pollutant which needs to be regulated.
The plant and animal kingdoms are a symbiotic pair and if humanity, by oxidising carbon into CO2, increases CO2 levels in the air, then that itself is a trigger for accelerated growth in the plant kingdom which then consumes it. Burning oil and coal does not necessarily mean that the non-human biosphere remains inactive!
I spent Saturday night (2 Sept) with friends who, with all seriousness, informed me that Western Australia had the driest winter ever in 2006. In 2005 we had the wettest winter with Broomehill recording its highest winter rainfall ever!
Now we have the driest! Source of their information? Your ABC!
Finally I have but one quibble with David’s, and hence the BOM’s, use of grid cells to
4-Corners seems to be the source of choice for authoritative exposition of received knowledge. (I must advise that I do not watch ABC television, preferring instead to source the internet for news).
That said I have a serious issue with David’s, and by association the BOM, use of grid cells to aggregrate climate measurements, here rainfall.
While the use of gridcells is appropriate as an aid in understanding climate data, they have no physical basis. So any conclusions derived from a statistical analysis of the gridcell aggregates are appropriate for those grid-cells, which physically do not exist. The same criticism could be directed to the Hadley Centre and its use of “grid-cells” as the basis for the aggregation of temperature readings.
Being an invention of the human mind, gridcells can warm or cool at a determined policy.
But it is not science.
Yes it’s not a pollutant in the sense that carbon monoxide is. CO2 IS a natural part of the atmosphere at some level, is a product of respiration, death & decay, and combustion, but ALSO is a greenhouse gas. Pity the biosphere doesn’t absorb CO2 as fast as we’re emitting it into the atmosphere.
The usual moaning about gridcells with no explanation nor alternative suggested.
Louis,
climate fields are generally continuous and representing such data using statical averaging onto grids is scientific robust and supported by thousands of scientific papers in peer reviewed journals. I suggest you consult Atmospheric Data Analyis by Roger Daley (Cambridge Atmospheric and Space Science Series), 457pp to better understand the process.
Very similar methods are used across all the geosciences (geology, oceanography, for example). If you have any published science which contradicts this universally accepted practice, I would very much like to see it.
Kind Regards,
David
d.jones@bom.gov.au
Aren’t we due for another La Nina?????