We interrupt the series on the PDO (but only briefly), to mention a topic which arose in recent discussion on RealClimate. Some comments suggested that Australia is not experiencing unusual drought — that it gets drought regularly and what’s happening today is just par for the course. It even suggested that over the long term, Australia is getting increased rainfall, and refers to a post on a website titled gustofhotair as supporting evidence. The website claims to present the author’s “statistical analysis of Australian Weather,” but I don’t see evidence of very much statistical analysis on the site. The author claims to be expert in statistics, but I don’t see any evidence of that at all.
One of the problems with water resources in Australia is that some regions are indeed getting more rainfall over the last several decades, while others are getting less:
The western part has received increased rainfall since 1970 while the east has received less. This is especially damaging to Australia’s agricultural industry, as most of it is concentrated in the east, especially in the Murray-Darling basin. Australia has indeed suffered droughts in the past, and is the world’s driest inhabited continent, but the drought currently plaguing the Murray-Darling basin is the worst in Australia’s history. In fact, the national legislature has recently created the Murray-Darling Basin Authority to take over management of water resources there, since effective management could not be undertaken by competing state governments.
The Australian Bureau of Meteorology provides climate data for Australia throughout the 20th and 21st centuries, from which we can see some of the changes in rainfall over the last 100 years. Overall, Australia has has increased rainfall over the last century, but the recent trend in the Murray-Darling basin is drier than the rest of the country:
Let’s take a closer look at what’s happened in the Murray-Darling basin. Here’s the monthly rainfall, averaged throughout the year:
Evidently there’s been a decline recently. We can see this more clearly by examining the smoothed values:
The recent decline has been severe. However, similar conditions prevailed early in the 20th century, so can the current drought in the Murray-Darling basin really be called the most severe ever observed? It’s important to realize that rainfall isn’t the only factor in creating a drought. Precipitation puts water into the system, evaporation takes it out, and the rate of evaporation depends largely on temperature: increased temperature means more evaporation, hence more severe drought. Here’s the annual average daily mean temperature in the Murray-Darling basin:
Temperature in the Murray-Darling basin has increased nearly 1.5 deg.C since about 1950, and the better part of a full deg.C since 1993. Mean temperature is a good indicator of evaporation rates, but a better indicator is the daily high temperature:
Daily highs in the Murray-Darling basin have increased about 1.3 deg.C since 1993. The combination of reduced rainfall and increased temperature has indeed made the present drought the worst in the history of the Murray-Darling basin.
While rainfall trends have been both up and down throughout the last century, temperature trends have been consistently increasing. And although rainfall trends over the last several decades are increasing in the west and decreasing in the east, the temperature trend has been increasing all over the continent:
The trend is strongest in the east, and the trend of daily high temperature is strongest in the southeast, hitting the Murray-Darling basin very hard:
One of the most dramatic signs of the recent drought is the level of lakes in the region. The level for lake Alexandrina is at a remarkable all-time low, presently half a meter below sea level:
Hence a number of factors have combined to make the present drought dangerous: reduced rainfall, increased temperatures, and increased population. So while demand is high, supply has dwindled to shockingly low values. This has dealt a crushing blow to Australia’s agricultural industry, robbing the nation of food resources and income. The prospect for improvement soon isn’t very good, as inflow to the Murray-Darling system for 2007-2008 has been close to the record lows observed in 2006/2007:
As stated in the River Murray System Drought Update for May 2008:
Analysis of 116 years of inflow data shows a very strong correlation between dry autumns and continuing dry conditions for the following year. If inflows remain low through May, there is an increased likelihood of dry conditions persisting through winter and spring. The protracted nature of this current drought and the consistent above average temperatures have dried out catchments and reduced base flows from groundwater systems to rivers. It can be expected, therefore, that even with average rainfall in 2008-09, inflows could remain well below average. Full recovery of the system would take several years of above average rainfall.There is also growing evidence that lower rainfall and reduced runoff in south-eastern Australia is linked to global warming.
Are the rainfall changes due to global warming? Perhaps — I don’t know. Are the temperature increases due to global warming? Unequivocally yes. The drought which would have been severe even in cooler times has been made far worse by higher temperatures. There’s strong evidence that Australia, and especially its agriculture, has become one of the first victims of global warming in the industrialized world.
I hope Americans are paying attention to the climate changes taking place in Australia. And I hope that the American midwest, in many ways the breadbasket of the world, doesn’t suffer the same fate now happening to Australia’s Murray-Darling basin.
As for the so-called “statistical analysis” from the “gustofhotair” blog — hot air indeed.
UPDATE UPDATE UPDATE
The question arose in commentary, is evaporation really related to the daily high temperature? It turns out that the Australian Bureau of Meteorology provides pan evaporation data for the Murray-Darling basin, but only since 1975. This doesn’t make it possible to estimate trends with accuracy, but it does make it possible to compare evaporation rates to the daily high temperature TX:
The correlation is clear, and is both statistically significant and strong:
Evidently the combination of reduced rainfall and higher dialy maximum temperature really has been a double-whammy for the water supply in the Murray-Darling basin.
UPDATE: a few graphs
Well … there it is.
79 responses so far ↓
JCH // May 30, 2008 at 5:41 pm |
It was my post on RC that started this one.
The rainfall anomaly information was just a click or so away from the BOM link the Australian skeptic provided. He kept going with annual rainfall.
I debated responding to him. Anybody who cites annual rainfall has never been involved in dry-land farming, at least not successfully. When you farm in those circumstances, it’s when it rains that is crucial. If you look at Australian wheat, the rainfall needed in planting season, as a for instance, appears to be trending down significantly. This years moisture started out looking good for planting. Estimates for the 2008 crop were robust. But just recently they downgraded harvest estimates because they have not had a enough rain to justify planting many fields.
Hank Roberts // May 30, 2008 at 6:30 pm |
> Western part has received increased rainfall
Here’s a photo shot looking up that boundary line that you can see on the rainfall map:
http://graphics8.nytimes.com/images/2007/08/14/science/fence_1_190.jpg
“The rabbit-proof fence — or bunny fence — in Western Australia was completed in 1907 and stretches about 2,000 miles. It acts as a boundary separating native vegetation from farmland. Within the fence area, scientists have observed a strange phenomenon: above the native vegetation, the sky is rich in rain-producing clouds. But the sky on the farmland side is clear.”
http://environmental-economics.blogspot.com/2007/08/rabbit-proof-fence-has-unintended.html
I’m very curious whether these observations have been looked at by statisticians.
steven mosher // May 30, 2008 at 7:18 pm |
Tamino. perhaps you could do a post on Hurst.
Just a thought.
Harold Brooks // May 30, 2008 at 8:09 pm |
RE: Rabbit-proof fence.
Just to be clear, the fence runs pretty close to the western gradient region near the west coast, not the stronger gradient in the middle of the continent. It’s dried on the west side of the fence and moistened on the east side.
Hank Roberts // May 30, 2008 at 8:46 pm |
> western gradient
Yep, look at the second image in the second link I posted above for an overview:
http://bp0.blogger.com/_vY3Y–Awsbo/RsKUOi7GpjI/AAAAAAAAAP0/gzglUHuBYo/s1600/fence_600.2.jpg
[Response: The link doesn't work for me.]
JCH // May 30, 2008 at 9:54 pm |
I relectant to post this as they do everthing “backwards” down under.
I believe this covers the planting season for winter wheat:
http://www.bom.gov.au/web01/ncc/www/cli_chg/timeseries/rranom/0305/mdb/latest.gif
A recent article on winter wheat planting and harvest forecasts:
http://www.bloomberg.com/apps/news?pid=20601082&sid=aqOPI3gTI9ak&refer=canada
chrisl // May 30, 2008 at 11:47 pm |
One of the most famous Australian poems by Dorothea McKellar was written in 1908 and is still apt today
I love a sunburnt country,
A land of sweeping plains,
Of ragged mountain ranges,
Of drought and flooding rains.
Nick Stokes // May 31, 2008 at 1:40 am |
Are the rainfall changes due to AGW? In the East, it’s ambiguous. But in the West, I have some personal experience. In about 1976, I was a junior mathematician, working for CSIRO in Perth. At about that time, a shift in the economics of wheat farming led to a push to open up new marginal areas. This required WA State government infrastructure, and they asked CSIRO whether this investment was wise in the long term. We checked out what was known, and a clear story emerged. The wheat belt (in the SW) gets all its rain from the belt of westerly winds (roaring forties) which come north in the winter. The westerlies are a product of the Hadley cells, which come down in those latitudes (the wind is a Coriolis effect). Global warming would increase the size of the cells, pushing the winds South. This is bad news, especially for the northern areas of the belt.
So we said no, not a good idea. The government seemed to accept this advice. And sure enough, that’s pretty much how it worked out.
Incidentally, the northern part of WA which is getting more rain includes a lot of arid land, where the rain is largely from tropical storms coming further south.
isaac held // May 31, 2008 at 2:54 am |
Tamino,
Following up on Nick Stokes’ comment, turn your analysis talents on the Southwestern Australia winter precipitation time series
Hank Roberts // May 31, 2008 at 3:42 am |
Sorry, Tamino, I guess you have to look at the image via the blog page, this link should work:
http://environmental-economics.blogspot.com/2007/08/rabbit-proof-fence-has-unintended.html
page down once to see the picture
Nathan // May 31, 2008 at 1:14 pm |
It’s also important to note that the large increases in central Western Australia don’t actually amount to that much rain. The interior is arid or semi arid and receives between 200 and 400mm per year, a 20% increase doesn’t amount to much. This rain normally arrives from decaying tropical cyclones and is sporadic, areas may go years with almost no rain, the get a deluge. I think this year was (actually the period from November 2007 to April 2008) particularly wet due to cyclonic activity.
Richard // June 1, 2008 at 3:38 am |
Nathan,
So that would be “the wrong sort of rain” then, like the “wrong sort of snow” on british rail lines?
georgedarroch // June 1, 2008 at 8:15 am |
I would also add that due to the extremely low level of geological activity, much of Australia has relatively unproductive soils. I couldn’t tell you what these changed rainfall patterns mean for Australian agriculture, but I do know that you need more than just rain to grow crops and feed livestock.
I was interested to see this morning, on the ABC, the conservative senator Bill Heffernan talking about the need to move Australia’s agriculture in response to long term shifts in rainfall patterns. He explicitly acknowledged climate change and future predictions. He’s regarded as somewhat of a dinosaur, so it’s an indication of how mainstream the acknowledgement of climate change is in Australia. The drought that has dominated most of this decade is most likely responsible in large part.
Luke // June 1, 2008 at 11:14 am |
To make a pronouncement on rainfall trends in Australia based on national time series or even a Murray- Darling Basin (MDB) average if quite disingenuous given the areas involved. There is wide spatial variation in national rainfall patterns and far from uniform land use.
Figure 2 here http://adl.brs.gov.au/mapserv/landuse/docs/Land_use_in_Australia_at_a_glance.pdf shows that the rainfall decline is very important as the areas affected are the capital cities and cropping zones. Much of western Australia is desert.
http://environment.gov.au/water/publications/mdb/pubs/mdb-map.pdf also shows the size of the MDB and the very different catchment area of the upper Murray River compared to the Darling River.
There has been record or near record drought conditions in the Murray River headwaters, south-east Queensland (SEQ) water catchments (for city of Brisbane), and ongoing rainfall decline in south-west Western Australia (WA) (the WA wheat belt).
One can define drought as rainfall or stream inflows which would now be at record lows in Murray system – see slide 4 here http://www.greenhouse2007.com/downloads/keynotes/071004_Cai.pdf
SEQ catchments have also had record low inflows despite the city area itself having enough rainfall. So sharp deficiencies can occur in small areas.
The Murray Darling Basin Commission has regular updates on the state of the Murray Darling Basin water supplies and the situation is indeed dire. http://www.mdbc.gov.au/
The inevitable comparison in Australian drought is to make a comparison of the current “Millennium” drought years with the turn of the 20th century “Federation” drought in the early 1900s. Other major droughts occurred in the the 1940s.
But is true that Australia is the “land of droughts and flooding rains” due to strong El Nino impact. And paleo evidence from coral cores would indicate that in some parts of Australia (e.g. north Queensland) perhaps even bigger droughts have occurred in the last few hundred years. So many people will be dismissive and remark “oh there has always been droughts”.
However, CSIRO and the Australian Bureau of Meteorology (ABoM) have now undertaken considerable work on the meteorology of Australian droughts and rainfall trends.
The impact of El Nino – Southern Oscillation effects (ENSO) is obvious, especially in eastern Australia. But further work has revealed the impact of changes in Antarctic circulation via changes in the Southern Annular Mode (SAM) on rainfall patterns in Australia. Southern hemisphere changes as documented by various papers in Science by Solomon, Thompson and Schmidt possibly relating both to changes in tropospheric greenhouse forcing and stratospheric ozone depletion.
Recent work by CSIRO (Wenju Cai and Tim Cowan) published in various Geophysical Research Letters papers from 2005 – two new papers in 2008 – show SAM affecting SW Western Australia and south-eastern Australia. The MDBC web site shows recent work by ABoM (Bertrand Trimball) documenting changes in the location of high pressure belts. Other ABoM and CSIRO research – Scott Power and CSIRO’s Ian Smith has shown a progressive weakening of the Southern Oscillation – Walker circulation. Indeed El Nino events have been more numerous than La Nina events since the mid 1970s. Neville Nicholls (ABoM) documented higher evaporative demand through higher temperatures in the Millenium drought compared to the Federation drought.
Other work has shown interaction of ENSO with the PDO and IPO.
But there are other factors changing too such as changes in ocean gyres, a warming Tasman Sea, and changes in the Indian Ocean Dipole (IOD). (presentations and papers by Cai again)
So the recent Murray Darling drought is both a combination of more frequent El Nino events and neutral years affected by SAM and other influences. Equally problematic is the issue of antecedent conditions – once catchments dry out it takes a lot of rain to wet them up enough to get major runoff. SW WA rainfall decline seems to be both natural and anthropogenic related to SAM – ENSO not being as much of an influence in WA.
Any effect on rainfall is amplified to more extremes runoff and on to stream and river inflows.
So the situation is most complex – but although Australia does suffer ongoing episodic droughts and floods – there does seem to be an anthropogenic influence on the frequency and severity of recent droughts.
IMO the southern hemisphere and rainfall trends don’t get enough attention on AGW issues. Not sure how southern Africa and South America are faring either.
If Tamino wishes I can table the references for the above research.
P.S. And how optimum was the Medieval Optimum for rainfall – massive droughts in America, Asia and Africa says Brian Fagan in his recent book “The Great Warming”.
Luke // June 1, 2008 at 11:25 am |
Conversely the increase in rainfall in northern Australia has been linked to the Asian aerosol haze affecting circulation patterns. Not all anthropogenic impacts have be CO2.
http://www.sciencedaily.com/releases/2006/12/061212213709.htm
Chris O'Neill // June 1, 2008 at 3:20 pm |
The graph of Lake Alexandrina level shows what a serious situation it’s in and how low the Murray river flow has been. On a closely related issue, the inflow to the city of Melbourne’s (Australia’s second largest city) reservoirs has also been and continues to be seriously low, i.e. 2006 had about 30% of previous long term inflow, 2007 had about 70% and so far 2008 has about 50% of normal inflow, although the wet season is yet to start. These years follow 8 years with an average 10-20% below normal.
Nathan // June 2, 2008 at 3:36 am |
Richard, I never said it was the “wrong sort or rain” was just putting it in context.
Selma // June 2, 2008 at 11:38 am |
I live in Sydney, Australia and I’m not as knowledgeable re. statistics as all your readers are but last year I worked with a journalist on a story re. the increase in suicide among Australian farmers as a direct result of income lost due to the drought. The stories are heart-breaking. I can’t tell you if it’s the most severe drought we’ve ever had but I can tell you that it is severe enough to cause many decent, good men to take their own lives. It is incredibly upsetting. The drought has crippled many farms and families.
chrisl // June 2, 2008 at 12:27 pm |
Right on cue: Floods in South – east Queensland.
Plenty of drought in other areas though.
Andy // June 2, 2008 at 7:06 pm |
Two comments: first, the rabbit proof fence and demarcation of native vegetation and cropland appears to support the hypothesis that reforestation in the subtropics will provide a decrease in average annual temperature due to the greater formation of clouds from increased transpiration. Enough to overcome the effect of a darker surface.
Second: I thought that work in Australia showed that global dimming, the blocking of sunlight from increased atmospheric aerosols, had greatly reduced evaporation. Wouldn’t this more than counteract increased evaporation from increased annual temperatures? I thought the science showed decreased pan evaporation rates in Australia?
CobblyWorlds // June 2, 2008 at 9:11 pm |
Tamino and Luke,
Thank you. Very much appreciated.
Cobbly.
Andy
http://www.cosis.net/abstracts/EGU2008/02257/EGU2008-A-02257.pdf?PHPSESSID=
If you’ve had the same sort of pollution legislation as in the US and Europe (No former Soviet Union in your hemisphere) you may see that effect locally to Australia.
Nexus 6 // June 2, 2008 at 11:11 pm |
Andy, dimming concerned northern Australia and was a result of fires from forest clearing in PNG and Indonesia. Northern Australia (the affected part) is tropical and very wet. No water shortage there. Virtually no people either.
Southern Australia, where nearly all the people live and agricultural production is centred is/was unaffected by the smoke – evaporation rates are most certainly higher down here.
I live just down the road (in an Australian sense) from Lake Alexandrina – the whole Coorong is in a terrible state. Ultra-saline and nothing much living there any more. Interesting to hear what the local indigenous people have to say on the topic.
Personally, we aren’t on town water and rely on rain water that hits the house roof for our drinking supply, so our little household is pretty damn concerned about whether we have enough water each summer. Everyone is putting in more tanks to collect all of what little water does come our way.
Hansen's Bulldog // June 2, 2008 at 11:35 pm |
I’ve updated the post to show the relationship (since 1975, for which data are available for the Murray-Darling basin) between daily high temperature TX and pan evaporation measurements.
Luke // June 3, 2008 at 12:15 am |
Some Australian work on temperature during drought and evaporation.
Evidence of impacts from rising temperature on inflows to the Murray-Darling Basin
GEOPHYSICAL RESEARCH LETTERS, VOL. 35, L07701, doi:10.1029/2008GL033390, 2008
Wenju Cai CSIRO Marine and Atmospheric Research, Aspendale, Victoria, Australia
Tim Cowan CSIRO Marine and Atmospheric Research, Aspendale, Victoria, Australia
The 2001–2007 Australian drought was the hottest on record with inflows to Australia’s longest river system, the Murray-Darling, reaching an historical low. Here we examine the relative importance of rising temperature and decreasing rainfall over its catchment, the Murray Darling Basin (MDB). Although annual-total inflow is more sensitive to rainfall over the southern MDB, where rainfall since 2001, has been the lowest on record, this alone can not explain the observed inflow decline. A relationship exists between inflow variations and fluctuations of temperature not associated with rainfall in the austral winter and spring: a rise of 1°C leads to an approximate 15% reduction in the climatological annual inflow. Our results provide strong evidence that rising temperatures due to the enhanced greenhouse effect have a strong impact on southern Australia’s water resources, in addition to any reduction in rainfall, and project a long-term decline in inflows to this river system as the greenhouse effect continues.
http://www.greenhouse2005.com/downloads/program/GH2005_Presentation_200511161440_1.ppt see slides 11 and 13 particularly on evaporation and temperature effects
Science 15 November 2002:
Vol. 298. no. 5597, pp. 1410 – 1411
DOI: 10.1126/science.1075390
The Cause of Decreased Pan Evaporation over the Past 50 Years
Michael L. Roderick, Graham D. Farquhar*
Changes in the global water cycle can cause major environmental and socioeconomic impacts. As the average global temperature increases, it is generally expected that the air will become drier and that evaporation from terrestrial water bodies will increase. Paradoxically, terrestrial observations over the past 50 years show the reverse. Here, we show that the decrease in evaporation is consistent with what one would expect from the observed large and widespread decreases in sunlight resulting from increasing cloud coverage and aerosol concentration.
Cooperative Research Centre for Greenhouse Accounting, Research School of Biological Sciences, Institute of Advanced Studies, Australian National University, Canberra ACT 0200, Australia.
Roderick ML, Rotstayn LD, Farquhar GD and Hobbins MT. (2007) On the attribution of changing pan evaporation. Geophysical Research Letters VOL. 34, L17403, doi:10.1029/2007GL031166
On the attribution of changing pan evaporation
Michael L. Roderick,1 Leon D. Rotstayn,2 Graham D. Farquhar,1 and Michael T. Hobbins1
Received 17 July 2007; revised 17 July 2007; accepted 8 August 2007; published 13 September 2007.
[1] Evaporative demand, measured by pan evaporation,
has declined in many regions over the last several decades.
It is important to understand why. Here we use a generic
physical model based on mass and energy balances to
attribute pan evaporation changes to changes in radiation,
temperature, humidity and wind speed. We tested the
approach at 41 Australian sites for the period 1975–2004.
Changes in temperature and humidity regimes were
generally too small to impact pan evaporation rates. The
observed decreases in pan evaporation were mostly due to
decreasing wind speed with some regional contributions
from decreasing solar irradiance. Decreasing wind speeds of
similar magnitude has been reported in the United States,
China, the Tibetan Plateau and elsewhere. The pan
evaporation record is invaluable in unraveling the
aerodynamic and radiative drivers of the hydrologic cycle,
and the attribution approach described here can be used for
that purpose.
Gifford RM, Roderick M and Farquhar GD. (2007) Evaporative demand: Does it increase with global warming? Global Change Newsletter 69, 21-23
http://www.rsbs.anu.edu.au/Profiles/Graham_Farquhar/documents/255GiffordetalEvapDemand.pdf
Much more work on Australian evaporation issues here – some pdfs available http://www.rsbs.anu.edu.au/Profiles/Graham_Farquhar
Greg // June 4, 2008 at 12:32 am |
I’m the one who took this up on RealClimate, and I’ll be happy to continue it here, but it seems I’m really just repeating myelf. For starters, how about you replace your 1970-present trend map with the one for the full century available here: http://www.bom.gov.au/cgi-bin/silo/reg/cli_chg/trendmaps.cgi?variable=rain®ion=aus&season=0112&period=1900. Why you would have a trend map covering only the last 30 years when we are trying to establish, in your own words, whether Australia is “experiencing unusual drought” is a mind-boggling mystery to me. The country has been here for longer than 30 years. Looks like you have moved quickly with the statistical voodoo on the evaporation too, because the trend in evaporation in the Murray-Darling and Australia wide is of course flat: http://www.bom.gov.au/cgi-bin/silo/reg/cli_chg/timeseries.cgi?variable=evap®ion=mdb&season=0112.
You can handwave and butcher the stats all that you want Tamino, but Australia is a desert country and droughts like the current one are par for the course. There is nothing unusual about the current climate (rainfall and drought wise, temperature maybe) Our lakes are empty because we have more people.
The BOM and CSIRO are organs of the government – a government only too happy to abdicate responsibility for helping farmers and securing water supplies. Thank god for the global warming bogeyman.
[Response: I did show the trend (and not just a linear trend) for the Murray-Darling basin for the entire time span of data. Undeniably there's reduced rainfall at present, and there was in the early part of the century too. But temperature today is a lot higher than back then, and there's no doubt that evaporation is correlated with temperature. Only the post-2000 drought has the combination of reduced rainfall and increased temperature which has brought about disastrous and unprecedented reduction of water resources, and there's little prospect of relief soon.
You're exactly the type of person who says things like "My grandmother smoked cigarettes for 80 years and lived to be 100, so cigarettes don't cause cancer!" The most incomprehensible thing is how you can possibly sleep at night, given that your propaganda is such a pack of lies. I guess its your lack of a conscience that puts your mind at ease.]
Andrew // June 4, 2008 at 4:30 am |
The correlation between daily high temps and pan evaporation is strong, but could be caused by another factor which is itself correlated to daily high temps, such as cloud cover.
Potential transpiration rates assume that plants can satiate themselves on water. This is rarely the case, especially during drought. Much of the work done in this arena has been aimed at irrigated crop land and its applicability to natural vegetation is limited.
I’ve been monitoring outflow of a small watershed for several years now here in Texas and have found that even small changes in rainfall can cause large changes in outflow to bayous (a coastal stream). The Texas coast is dominated by vertisol soils, similar to much of Australia and lots of the arid world. These soils are extremely slowly permeable and the recharge of aquifers and the supply of base flow to rivers is often negligable in areas dominated by these soils. This greatly magnifies the effect of drought on stream flow. Vertisols also preclude the storage of excess rainfall (in excess of immediate plant needs) in deep layers of the soil and so soil water is subject to very rapid depletion by plant transpiration (often only the top foot or so of the soil is at all permeable and plant roots are often confined to this layer). I’ve found that during periods of drought, rainfall runoff is captured in small depressions and is very quickly used by transpiring plants. Very little runoff occurs. During wetter periods, these depressions are filled, plants are satiated, and runoff can be almost constant until high temps and transpiration rates finally drain the system down. In Texas, outflow from a 25-acre watershed during a year in which rainfall was in excess of the average (52″ average) occurred over half the year. During a year in which rainfall was slightly below average, outflow occurred during only a handful of days.
I found a lot of applicable literature on these soils, associated wetlands and surface hydrology in Australian journals. Much of it by waterfowl researchers including a lot written on the Murray, Darling River system. It appears that Australia has a lot of the same sort of small, closed basin wetlands and impermeable soils that Texas does.
The bottomline is that Texas’ and perhaps Australia’s soils and landscapes may cause feedbacks that magnify the decrease in runoff caused by a decrease in rainfall. I’m hoping to publish this in Wetlands (Society of Wetland Scientists) which I believe has a strong presence in Australia.
Lost and Confused // June 4, 2008 at 3:22 pm |
Greg, your criticisms make little sense to me. In his post Tamino clearly stated the current rainfall levels are not unique. Showing a trend map from 1900 would not give any information not provided in the graphs following it. Choosing to display a trend map from 1970 is more meaningful, as the trends noted appear near that point. If you note, the post makes it clear that the low rainfall levels are not unique, but the coinciding temperature increase is.
As for your second complaint, the trend is not flat. It may appear to be flat at a casual glance of that link, but that is only because that graph uses the simple approach of a running average. Properly analyzed, as done in Tamino’s post, the trend is clear and significant.
I will not impugn your motives, but you should consider using a different tone when criticizing someone. It is bad enough to do it when you are right, but it is downright silly to do it when you are wrong.
Lost and Confused // June 4, 2008 at 3:23 pm |
Just to note, at the time I was typing that post Tamino’s response was not displayed. I suppose my post is a little superfluous now.
JCH // June 4, 2008 at 4:24 pm |
Annual trends mean not that much to a dry-land farmer.
What is the trend during the parts of the year in which Australian farmers attempt to grow rice and wheat. It could be drier in the past on an annual basis nationwide, and also have years with good to excellent crops.
If you look at the trend maps of the Australian wheat belt, it appears to be getting hammered during the times of the year that matter the most to crops.
Dano // June 4, 2008 at 4:33 pm |
The bottom line is that Texas’ and perhaps Australia’s soils and landscapes may cause feedbacks that magnify the decrease in runoff caused by a decrease in rainfall. I’m hoping to publish this in Wetlands (Society of Wetland Scientists) which I believe has a strong presence in Australia.
Interesting. I’d be interested in the results.
One thing to note is plant transpiration does not occur in humidities of 100% – as transpiration occurs when there is a difference in the vapor pressure potentials between air and plant (air must be less than turgid plant tissues as water vapor flows from higher to lower potential). I suspect if rainfall is lower in a given time period, RH must be too, so effects may be negligible, but coastal basins/subwatersheds may also experience elevated RHs in a cloudier regime…hmmm…lots to think about.
Thank you for the comment.
Best,
D
JP // June 4, 2008 at 7:59 pm |
Has anyone checked on major changes in the Walker Circulation these past 3 or 4 decades? After all, there precipitation patterns fro Austrailia are tied closely with this oscillation.
Luke // June 4, 2008 at 9:14 pm |
Talking about Australia as a whole is really misleading as an argument. Especially when there are major regional effects where people live and where crops are grown and livestock graze.
Australian soils may be poor in the main, although there are some of the best cracking clay soils, or vertisols, anywhere in the world too (e.g. Darling Downs, clay soils from Goondiwindi to Narrabri NSW, Emerald and Clermont in Queensland in Queensland)
However, the soil is not the climate issue. Farming systems ARE already adapted to the soil types and limitations. 150-200 years of experience.
As a rule of thumb “rain-fed” / “dryland” (not irrigated) cropping systems in these areas run on – 4 years in 10 break even, 3 years in 10 make a good profit, 3 years in 10 make a loss.
Change this frequency distribution too much and whole farming communities and their support towns can go to the wall.
And it is not just total rainfall – winter wheat crops need raining just at the right time to plant – in recent years farmers have sat by knowing they have moisture at depth but cannot get a planting rain.
Plant growth is the integration of rainfall, stating soil moisture, evaporation – which in itself is a combination radiation, humidity (vapour pressure deficit more correctly) , wind, and temperature, and how rainfall is distributed in the season.
No planting rain – no crop. No follow-up rain – seed heads don’t fill. Crops fail. Invested dollars in establishing the crop lost for no return.
Drought feeding of cattle and sheep can be similarly traumatic – $100,000s can be invested in drought feeding for no eventual return is droughts persist over years.
Also evaporation is heavily influenced by radiation and wind. Clear El Nino skys and low humidity mean higher evaporation. Indeed temperature is not the biggest effect.
Darwin (top of Australia) is warmer than Alice Springs (centre of Australia) overall. BUT evaporation is much higher at Alice Springs – why – much more radiation and low humidity.
So drought does not have to be defined in terms of rainfall. Stream runoff is another definition, especially for irrigators and town water supply. And ultimately plant growth or animal production moving to dollars is the big indicator.
So you can define drought in terms of rainfall, runoff, wheat or pasture yield, or even dollars (dollars as long as the measure reflects meteorological impacts and is not confounded with other effects).
Drought has a spatial context – some droughts are much more widespread than others. Droughts have durations. But Australian farmers can cope with the occasional drought. However can they cope with continuous drought since 2001? Following on from other drought episodes in the 1990s.
Many people think as soon as it rains it’s all over. Recovery from drought is protracted – instant rainfall does not provide instant crops, instant livestock or instant dollars. It can take many many years to replace herds and regain cash flow. A decade has been suggested for recent drought sequences.
The Murray River inflows are at a record low. Now for another year.
Drought conditions are back in the wheat belt. http://www.nbr.co.nz/article/rabobank-expect-a-small-australian-wheat-crop
The south-east Queensland inflows also got to a record low in 2007. The cities of Brisbane and Ipswich not out of level 6 restrictions despite recent rainfall.
South-west Western Australian rainfall has gone through a step decline over 30 years.
All this has some very good explanation in both El Nino frequency, oceanic changes, changes in southern hemisphere circulation. Very few La Nina events to reset the system. And this La Nina event has had patchy impact.
There is a more than plausible case for some anthropogenic influence.
Read the Murray Darling reports – this is crunch time stuff. http://www.mdbc.gov.au/__data/page/1366/Drought_Update_Issue_13_-_May_2008.pdf
Australian governments have spent many billions of drought aid now over decades. The drought aid is essentially social welfare support to keep food on the table, kids going to school and the lights on.
The high level of aid drives Treasury economists nuts – some districts have had their next 300 years drought support – based on maybe 3 exceptional events per century as the conceptual level of support for “Exceptional Circumstances”.
Many farmers have to consider whether to continue in agriculture, get out of farming, or move to where the rainfall is – northern Australia. However as well as tremendous social dislocation, that requires a totally new farming system and new crops.
The following papers are the basis for a case that things have changed for Australian agriculture. Where are they wrong?
David W. J. Thompson and Susan Solomon (3 May 2002) Interpretation of Recent Southern Hemisphere Climate Chang, Science 296 (5569), 895. [DOI: 10.1126/science.1069270]
Shindell, D. T., and G. A. Schmidt (2004), Southern Hemisphere climate response to ozone changes and greenhouse gas increases, Geophys. Res. Lett., 31, L18209, doi:10.1029/2004GL020724.
Cai, W. (2006), Antarctic ozone depletion causes an intensification of the Southern Ocean super-gyre circulation, Geophys. Res. Lett., 33, L03712, doi:10.1029/2005GL024911.
Cai, W., and T. Cowan (2006), SAM and regional rainfall in IPCC AR4 models: Can anthropogenic forcing account for southwest Western Australian winter rainfall reduction?, Geophys. Res. Lett., 33, L24708, doi:10.1029/2006GL028037.
Cai, W., T. Cowan, M. Dix, L. Rotstayn, J. Ribbe, G. Shi, and S. Wijffels (2007), Anthropogenic aerosol forcing and the structure of temperature trends in the southern Indian Ocean, Geophys. Res. Lett., 34, L14611, doi:10.1029/2007GL030380.
Power, S. B., and I. N. Smith (2007), Weakening of the Walker Circulation and apparent dominance of El Niño both reach record levels, but has ENSO really changed?, Geophys. Res. Lett., 34, L18702, doi:10.1029/2007GL030854.
Cai, W., and T. Cowan (2008), Evidence of impacts from rising temperature on inflows to the Murray-Darling Basin, Geophys. Res. Lett., 35, L07701, doi:10.1029/2008GL033390.
Cai, W., and T. Cowan (2008), Dynamics of late autumn rainfall reduction over southeastern Australia, Geophys. Res. Lett., 35, L09708, doi:10.1029/2008GL033727.
Trimbal et al. (2008) Final report for Project 1.1.2 for the South East Australian Climate Initiative – Final report for Project 1.1.2 “Compare documented climate changes with those attributable to specific causes” http://www.mdbc.gov.au/subs/seaci/Final_report_for_Project_1.1.2.pdf
Rainfall increases in northern Australia http://www.science.org.au/events/australiajapan/rotstayn.pdf
Rotstayn, L. D., et al. (2007), Have Australian rainfall and cloudiness increased due to the remote effects of Asian anthropogenic aerosols?, J. Geophys. Res., 112, D09202, doi:10.1029/2006JD007712.
Luke // June 4, 2008 at 9:27 pm |
On a few specific points from comments above:
Changes in Walker circulation – see http://www.agu.org/pubs/crossref/2007/2007GL030854.shtml
Failure of Australian rice crop
http://www.theaustralian.news.com.au/story/0,25197,23595713-643,00.html
Effect of land clearing on drought
McAlpine, C. A., J. Syktus, R. C. Deo, P. J. Lawrence, H. A. McGowan, I. G. Watterson, and S. R. Phinn (2007), Modeling the impact of historical land cover change on Australia’s regional climate, Geophys. Res. Lett., 34, L22711, doi:10.1029/2007GL031524. Although I would caution that this is early work in a developing area. There is likely to be some effect but how much it’s swamped by oceans temperatures and large scale atmospheric circulation is still debatable in my opinion.
Luke // June 4, 2008 at 11:32 pm |
I have to say the comments from above are remarkable.
“You can handwave and butcher the stats all that you want Tamino, but Australia is a desert country and droughts like the current one are par for the course. There is nothing unusual about the current climate (rainfall and drought wise, temperature maybe) Our lakes are empty because we have more people.”
Sorry Australia is a little more than deserts. And where there are deserts (which do cover vast areas of central, and Western Australia) there are virtually no people or land use. http://www.nams.gov.au/index.cfm?fa=analyses.show&dataType=analysis&analyses=134&mainCategories=17&subCategories=1&analysesList=4&showWeather=false&showSilo=false&showSurfaceWater=false&showGroundWaterLevel=false&showGroundWaterQuality=false&showDam=false&showdates=false
Deserts do NOT equal drought. Arid environments are simply arid environments. Drought is at least below decile 1 or perhaps severe at percentile 5 annual rainfall. Drought is a relative concept than can apply from desert to rainforest. Saying arid environments are “droughty” is simply wishing the environment to be more than it is.
Drought like the recent and ongoing in parts 2001-2008 Millennium drought as well as the early 1900s Federation Drought are not par for the course. They’re exceptional prolonged multi-year events.
This is what a recent 36 month decile analysis looks like http://www.bom.gov.au/cgi-bin/silo/rain_maps.cgi?map=contours&variable=deciles&area=aus&period=36month®ion=aus&time=latest
“Lakes” ? We don’t have many “lakes” unless you want to include central Australian salt lakes. But if you mean reservoirs or dams built on the Murray – those dams are very low/critical as there has been no rain, the catchment is very dry, and no runoff. Not because of population pressures. The inflows have been demonstrated by the water resources authority as lowest on record (ongoing). Dams in Australia and South Africa are already much larger than northern hemisphere dams for the same level of supply risk due to catering for ENSO variation.
The rules for drought relief through the Commonwealth Exceptional Circumstances scheme are quite tough. The notion behind these schemes are to assist in extreme events which only a few severe drought events will occur each century – not almost ongoing support in parts since the 1991 El Nino.
This is what NSW EC declarations (areas eligible for drought relief) look like currently http://www.daff.gov.au/agriculture-food/drought/ec/nsw_act
Reports for other states can be made or the criteria for declaration status examined at the same site.
Greg // June 5, 2008 at 12:46 am |
Tamino, did you even read the work of Michael L. Roderick and Graham D. Farquhar above? So there what we have is confirmation from people who actually research these things (as opposed to a statistical blog jockey) that pan evaporation is not correlated to temperature. We also have nothing unusual in Australian precipitation levels, both country-wide and in the Murray-Darling.
Australia is an example of the damage that climate change can cause, since our population expanded and our farming infrastructure was established during a time of unusual wetness. Unfortunately for your agenda, the climate change is likely natural – a return to more typical conditions. There is not a jot of evidence that the current dry conditions have anything to do with global warming.
Of the two factors at play in a drought – precipitation and evaporation – you admit (surely you must) that precipitation levels have not decreased unusually.
So the challenge for you then is to refute the work in the papers noted above and show that pan evaporation has increased unusually. I look forward to it – you are truly a master of number-fiddling. Your simple temperature correlation won’t cut it.
Start with:
http://www.rsbs.anu.edu.au/Profiles/Graham_Farquhar/documents/255RoderickRoFaHopanattribGRL2007.pdf
“Over Australia, that approach
revealed differences between sites, but on the whole, decreasing wind speed was found to be the main reason for decreasing pan evaporation.”
[Response: You state that "pan evaporation is not correlated to temperature." But the numbers call you a liar. This isn't a matter of opinion, it's fact; the correlation isn't just statistically significant, it's overwhelmingly so. If one uses monthly data, correlating temperature anomaly against evaporation anomaly, the statistical significance is even stronger. And by the way, when it comes to statistical analysis I'm not just a "blog jockey" (like the fool who runs the "gustofhotair" blog which was your *original* reference on RealClimate), I'm an active researcher with a reasonably long list of peer-reviewed publications.
But you're not able to do the analysis, or you're so attached to ideological opposition to global warming that you'll say or do anything, or both. Either the reference you link to is wrong, or (far more likely) you've mischaracterized and/or misunderstood what they claim. You're not worth the effort to find out.
As long as you continue the "2 + 2 = -12.369 so global warming is natural" line of reasoning, nobody will take you seriously. And that's as it should be.]
Greg // June 5, 2008 at 2:34 am |
“Either the reference you link to is wrong, or (far more likely) you’ve mischaracterized and/or misunderstood what they claim. You’re not worth the effort to find out.”
Here’s a tip, your 5 minute temperature/evaporation correlation doesn’t trump mountains of research. You’re doing exactly what you would tend to accuse Anthony Watts of. How exactly have I mischaracterized when “the overwhelming body of data from pan evaporimeters and estimated lake evaporation rates averaged over large regions in numerous conutries in both hemispheres show decadal trend-lines, fitted through the inter-annual variability, of declining rates of unconstrained free-water evaporation since the early 1970s (when measurements began). This is despite the warming of the lower atmosphere during that period.”. It’s all there, but you tell me you can’t be bothered reading it.
And as for Luke:
“But if you mean reservoirs or dams built on the Murray – those dams are very low/critical as there has been no rain”
In case you’ve been living under a rock for most of this discussion, there has been rain. The BOM say so. Exactly as much as you’d expect in 1900-1950 Australia. If we had 21 million people and a modern irrigated agriculture system going into the federation drought, things would be just as dire. When I said ‘desert country’, I meant that we are a very dry country prone to drought. And when I say ‘par for the course’, I simply mean that one need not invoke global warming to explain them.
[Response: Out of curiosity, I did read the paper you reference. So here's a tip for you: you have completely misunderstood that paper. It does NOT claim that "pan evaporation is not correlated to temperature." Quite the opposite, the model they use depends strongly on temperature. What is *does* claim is that the *trend* in pan evaporation over the Australian continent (not the Murray-Darling basin) is only weakly due to trends in temperature, it's much more strongly due to trends in wind speed.
How the hell you got "pan evaporation is not correlated to temperature" from that paper is beyond me. But here's a guess: you so strongly *wanted* to deny that evaporation increases with increasing temperature, that you leapt at that interpretation and swallowed it whole. Because it's 100% clear you didn't understand the paper you reference or what those authors are talking about.]
Nick Stokes // June 5, 2008 at 2:56 am |
Greg, did you even read the paper of Roderick and Farquhar that you linked. From their discussion (my emphasis):
“Previous research reported a trend in pan evaporation rate, averaged over 61 Australian sites for 1975–2002, of -3.3 mm a^-2 [Roderick and Farquhar, 2004]. This was later updated to -3.2 mm a^-2 to account for the installation of bird guards. The trend for 1975–2004 over the same 61 sites is lower at -2.4 mm a^-2 (results not shown) because of the high pan evaporation rates during the drought conditions prevailing over much of southeast Australia since 2002.”
No drought?
Luke // June 5, 2008 at 4:24 am |
But that’s not to say temperature has no effect. Consider the well used Penman-Monteith evaporation equation http://en.wikipedia.org/wiki/Penman-Monteith
Evaporation is a function of wind, solar radiation (cloudiness, time of year, latitude), vapour pressure deficit (humidity sort of), AND temperature.
It’s not like temperature has no effect. But other effects may be more dominant.
However the wind finding in Australia is most interesting. Now why has the wind changed? Circulation changes which may have an AGW basis (perhaps?).
Anyway – look at Cai’s paper – there’s a paper that says there is a major effect of temperature on drought and inflows. Cai, W., and T. Cowan (2008), Evidence of impacts from rising temperature on inflows to the Murray-Darling Basin, Geophys. Res. Lett., 35, L07701, doi:10.1029/2008GL033390.
The 2001–2007 Australian drought was the hottest on record with inflows to Australia’s longest river system, the Murray-Darling, reaching an historical low. Here we examine the relative importance of rising temperature and decreasing rainfall over its catchment, the Murray Darling Basin (MDB). Although annual-total inflow is more sensitive to rainfall over the southern MDB, where rainfall since 2001, has been the lowest on record, this alone can not explain the observed inflow decline. A relationship exists between inflow variations and fluctuations of temperature not associated with rainfall in the austral winter and spring: a rise of 1°C leads to an approximate 15% reduction in the climatological annual inflow. Our results provide strong evidence that rising temperatures due to the enhanced greenhouse effect have a strong impact on southern Australia’s water resources, in addition to any reduction in rainfall, and project a long-term decline in inflows to this river system as the greenhouse effect continues.
In severe drought those hot sunny cloudless days do take their toll on water balance.
Luke // June 5, 2008 at 4:30 am |
Greg to say that the Murray River headwaters have not been in extreme and record breaking drought defies all belief. I’m gobstopped. The calculated inflows ARE lowest on record. Are you on the planet. Email the Bureau of Meteorology’s National Climate Centre in Melbourne and ask them !! or the Murray Darling Basin Commission.
Have you wondered why all the political attention involving the 4 Australian states (Qld, NSW, Vic and SA) that have land in the Basin and the Australian Federal government is at fever pitch. It’s a catchment in crisis.
Greg // June 5, 2008 at 4:37 am |
And Luke, the fine print on your 36 month decile analysis:
“The rainfall percentages and anomaly maps are calculated with respect to the reference period 1961-1990.
Temperature variables
The temperature anomaly maps are likewise calculated with respect to the reference period 1961-1990.”
…a reference period which was much wetter than the period both before and after. 1961-1990 is an anomalous period.
Phil Scadden // June 5, 2008 at 5:03 am |
perhaps I am not reading this right but looking at http://www.rsbs.anu.edu.au/Profiles/Graham_Farquhar/documents/255RoderickRoFa
it seems that with the penpan model, evaporation is split between radiative and aerodynamic components. Temperature is implicit and the Aerodynamic component is temperature dependent. The paper claims CHANGE in evaporation rates is affected most be change in windspeed. This is about attribution. The model takes as given that evaporation is dependent on temperature. Note also that wind is not independent of AGW either.
[Response: Congratulations, you *are* reading it right. Greg's the one who isn't.]
Greg // June 5, 2008 at 8:01 am |
“You state that ‘pan evaporation is not correlated to temperature.’ But the numbers call you a liar.”
Have you ever heard of the ‘pan evaporation paradox’ Tamino? Go and google it. Obviously, you’d best get in contact with the scientists that try to explain it and let them know that you’ve solved it. And that they, like me, are all liars. Since temperature does correlate with pan evaporation. Right?
And to take your statement to the ridiculous extreme, since worldwide pan evaporation has been declining for 50 years, and Tamino has proven in five minutes on his blog that temperatures and pan evaporation correlate and there is no paradox, I can now conclude that global warming is not occuring. Ha.
[Response: Once again -- the paper you reference makes absolutely no such claim as pan evaporation being uncorrelated with temperature, you have misunderstood that paper to a degree that is breathtaking. You only saw what you *want* to see, and evidently you haven't got the cognitive faculty to comprehend the very paper you use as a reference for your belief.
Your level of understanding confirms that you simply aren't worth the time to bother investigating the issues you raise. You and Anthony Watts belong together -- rank beginners who pontificate on the basis of astounding ignorance.]
Lazar // June 5, 2008 at 12:59 pm |
Greg;
The authors did not find that “pan evaporation is not correlated to temperature”.
1) relatively small effects of temperature on pan evaporation rates were found.
2) the effects were imputed from a physical model.
3) the analysis does not cover the Murray-Darling basin.
4) the effects of temperature are calculated as the effect of surface air temperature on saturation vapour pressure. They do not include the effect of temperature on the vapour pressure deficit, which seems strange to me (Luke?)
5) Temperature is correlated with evaporation rates in the Murray-Darling basin as shown by Tamino above.
The paper you cite says;
Follow the cites. Read the links provided by Luke.
Rainman // June 5, 2008 at 2:58 pm |
I’ll not comment on the rest of Greg’s assumptions, but the paper he links suggests average wind speed and not temperature to be a primary driver for pan-evaporation. This does make sense from a physics standpoint (swamp cooler anyone?)
As to if climate change is altering the wind patterns… that would seem likely…
[Response: Actually it suggests that the *trend* in pan evaporation over the Australian continent (not the Murray-Darling basin) is primarily due to the trend in wind speed. It uses a physical model in which evaporation is *very strongly* dependent on temperature.]
george // June 5, 2008 at 4:10 pm |
Farquhar & Roderick specifically addressed the global decrease in pan evaporation over the past 50 years
There has been a worldwide decrease in pan evaporation over roughly the past half-century (supposedly related to global dimming) — with an apparent reverse in the trend since about 1990.
But that does not mean the decrease in pan evaporation occurred in every region (it did not) and it certainly does not mean “that pan evaporation is not correlated to temperature” or that “There is not a jot of evidence that the current dry conditions [in the Murry darling basin of Australia, specifically] have anything to do with global warming.”
Wikidpedia has this to say on the subject:
Rainman // June 5, 2008 at 4:38 pm |
Hmm… at first I thought you were disputing what I stated… But upon further review, I think you are expanding my (layman’s) summary to be more accurate. Is that the case?
[Response: I think so.]
Goedel // June 5, 2008 at 7:10 pm |
The misunderstanding here seems fairly simple: Greg does not know the real meaning of the word ‘correlation.’
David B. Benson // June 5, 2008 at 9:03 pm |
Background, not specifically Australia:
Water vapor theory with warnings regarding two fallicies:
http://geosci.uchicago.edu/~rtp1/papers/CaltechWater.pdf
No secular trend in global precipitation in over 25 years:
http://cics.umd.edu/~yin/GPCP//ASSESSMENT/assessment.html
Greg // June 5, 2008 at 11:02 pm |
Spin, obfuscate, dodge. There is a global downwards trend in pan evaporation. There is a downwards trend in pan evaporation across most of Australia. There is nothing anomalous about recent Australian rainfall. There is nothing anomalous about recent Australian rainfall in the Murray Darling region.
Which of the four sentences above do you not agree with Tamino? Because they all add up to, for regular people with a working sense of logic, the current drought not being attributable to humans.
And obviously the *trend* in evaporation is the only thing worth discussing, and what I took from that paper. If worldwide temperatures are clearly trending up, and evaporation down, then exactly how strong are you claiming your temperature/evaporation correlation to be?
[Response: We're talking about drought in the Murray-Darling basin. But you want to shift the focus to "global" and "most of Australia." The recent rainfall in the Murray-Darling basin *is* anomalous, although not unprecedented, and multi-year average daily high temperatures in the M-D basin are unprecedented. There's a very clear and very strong correlation between daily high temperature and evaporation. But you *still* dispute this, despite the fact that the *numbers* call you a liar.
And *that* is why the M-D basin is suffering a drought which the Australian government itself refers to as a "once in a thousand years" event. Yet you still insist that it's just normal.
As for the trend being "the only thing worth discussing," that's just a feeble attempt to save face. You must really be stinging, because it's obvious to everyone that you didn't have the faintest understanding of the very paper you used as a reference for your ridiculous claim that there's no correlation between temperature and evaporation.
I'm under the distinct impression you really don't get it. If so, then you're a textbook example of being in denial. Too bad for you. I'm quite sure you don't have anything of value to contribute, here or anywhere else.]
Luke // June 5, 2008 at 11:06 pm |
No No No Greg – read the fine print on the 36 month maps again. It says:
“The rainfall deciles and drought maps based on a reference period comprising all gridded analyses from 1900 to the present available at the time the deciles are calculated. The rainfall percentages and anomaly maps are calculated with respect to the reference period 1961-1990.”
Note what it said about deciles being from 1900 onwards. !!!! Deciles which are one of the oldest and most classic methods of drought analysis. (Gibbs and Maher, 1967).
What are deciles or percentiles – you get all the observations in a time series and rank them lowest to highest. Then divide them into 10 or 100 bins. So decile one would be the lowest 10% of years. For a particular period like the last 36 months that period (as a whole) is then ranked on the decile or percentile scale. Pretty basic stats.
You will not you do NOT add the decile ranking of years together. Has to be the whole period. Adding deciles or percentiles is a no no.
Additionally I can tell you many years had patches of worst ever rainfall deficits i.e. below any previous measurement in 116 to 117 years.
However rainfall is only one measure of drought – runoff is more relevant to water supply.
And plant growth is more relevant to crops and pastures.
What has been shown is that effects on rainfall are greatly amplified when you pile on additional drought effects like evaporation (wind, temperature, humidity, radiation) and antecedent conditions (bone dry catchments which take lots of wetting up to get runoff).
El Nino events often have very sunny, hot, low humidity days.
Australian agricultural scientists use models of plant growth with soil water balances to make these calculations – models well tested in field experiments.
Engineers use well calibrated catchment models.
The USA also uses the Palmer Drought Index – http://en.wikipedia.org/wiki/Palmer_Drought_Index and other indices which are reviewed here by the US National Drought Mitigation Center. http://drought.unl.edu/whatis/indices.htm
NOTE – temperature is part of that well used Palmer index.
Farmers use another index – it’s call reality – no water, no crops, no pasture, dead livestock, high stress, and no income. Strangely they are very perceptive.
Federal Treasury uses another index – regions in drought, lack of export income, and billions of dollars in social support aid (welfare). The Southern Oscillation Index actually moves the whole Australian economy.
Ask them whether they think it’s all “par for the course”.
Luke // June 5, 2008 at 11:15 pm |
Being less parochial and looking at drought globally – has it gotten worse? I be interested in any analyses anyone has found.
There is this one:
Modeling the Recent Evolution of Global Drought and Projections for the Twenty-First Century with the Hadley Centre Climate Model
Journal of Hydrometeorology
A publication of
American Meteorological Society
Volume: 7 Issue: 5 (October 2006)
Simon J. Brown, Hadley Centre for Climate Prediction and Research, Met Office, Exeter, United Kingdom
Eleanor J. Burke, Hadley Centre for Climate Prediction and Research, Met Office, Exeter, United Kingdom
Nikolaos Christidis, Hadley Centre for Climate Prediction and Research, Met Office, Exeter, United Kingdom
Abstract
Meteorological drought in the Hadley Centre global climate model is assessed using the Palmer Drought Severity Index (PDSI), a commonly used drought index. At interannual time scales, for the majority of the land surface, the model captures the observed relationship between the El Niño–Southern Oscillation and regions of relative wetness and dryness represented by high and low values of the PDSI respectively. At decadal time scales, on a global basis, the model reproduces the observed drying trend (decreasing PDSI) since 1952. An optimal detection analysis shows that there is a significant influence of anthropogenic emissions of greenhouse gasses and sulphate aerosols in the production of this drying trend. On a regional basis, the specific regions of wetting and drying are not always accurately simulated. In this paper, present-day drought events are defined as continuous time periods where the PDSI is less than the 20th percentile of the PDSI distribution between 1952 and 1998 (i.e., on average 20% of the land surface is in drought at any one time). Overall, the model predicts slightly less frequent but longer events than are observed. Future projections of drought in the twenty-first century made using the Special Report on Emissions Scenarios (SRES) A2 emission scenario show regions of strong wetting and drying with a net overall global drying trend. For example, the proportion of the land surface in extreme drought is predicted to increase from 1% for the present day to 30% by the end of the twenty-first century.
Additionally Brian Fagan has just written a new book on the Medieval Warm Period (no Hockey Stick wars pls) where he documents major drought in the Americas, Asia and Africa. So makes one wonder how rainfall and circulations get moved around in a warmer world (i.e. winners and losers – even if the overall rainfall is higher). So this brings us back to importance of spatial distribution, timing of rainfall and evaporation factors – a global average of rainfall would be grossly misleading.
Is the MWP a “dry run” for our future? hmmm…
(Fagan’s book here: http://www.amazon.com/Great-Warming-Climate-Change-Civilizations/dp/1596913924 )
Luke // June 5, 2008 at 11:46 pm |
Sorry to go on but missed this again from Greg:
Greg retorts:
“In case you’ve been living under a rock for most of this discussion, there has been rain. The BOM say so. Exactly as much as you’d expect in 1900-1950 Australia. If we had 21 million people and a modern irrigated agriculture system going into the federation drought, things would be just as dire. When I said ‘desert country’, I meant that we are a very dry country prone to drought. And when I say ‘par for the course’, I simply mean that one need not invoke global warming to explain them.”
Again no no no. Yes there has been “some” rain. Unless you have been living under a rock you would have checked out the various links at the Murray Darling Basin Commission site http://www.mdbc.gov.au/
You would have noticed that despite some rain, runoff has NOT improved greatly. Flows are again at record lows. You would have also noticed that these low flows are NOW below the Federation drought for the second year running.
When catchments dry out – it takes a LOT of rain to wet them up to the point of getting runoff. Antecedent conditions the hydrology modellers call it. Which is why multi-year droughts with no relief are very tough to crack. They really need a massive La Nina with floods to put them back.
Inputs (inflows) have nothing to do with 21 million people. Usage of the water does have lots to do with people and agriculture.
And you might say that the Murray ran dry in the Federation drought – horses and buggies pictured in the river bed during that drought. Picture taken of the dry Murray River bed at Riversdale on 1st January 1914 – http://www.jennifermarohasy.com/blog/archives/Dry%20Murray%201914%20blog.JPG
But dams changed all of that. With dams and weirs the river cannot ever run bone dry. A wet river bed doesn’t mean any water is available for irrigation though.
Yes the dam network and irrigated agriculture was not there in 1900.
But the MDB Commission have very good models of the catchment behaviour – “strangely” that’s the main thing they do – if you do the calculations this inflow situation is now worse than what would have happened if the dams had been there in 1900.
There is only some water in the river as the dams can provide that – and essential for town water supplies. But the bottom of the system – the Coorong wetland is now in big trouble with salinity from low flows and ocean incursion. It’s THAT bad. River red gums on the stream banks along the Murray are dying. Special allocations of water have been made to keep some of these forests alive – very controversial when irrigators are missing out.
AND the same story for south-east Queensland water catchments. (not part of the MDB) Brisbane still on level 6 water restrictions. The inflows were assessed to be worse than what would have happened in 1900 drought.
AND SW Western Australia (not part of the MDB) has has a step decline in rainfall going on for 30 years.
What I will give you is this – the Federation drought may have been greater in area. Lack of heavy freight transport, telecommunications and organised government support would have made it much worse.
We do know from off-shore coral core records that the Burdekin River in north Queensland did not flow greatly for 20 years during the 1700s.
So perhaps the past did have worse droughts. I would not surprised.
But look at the references I have provided – I suggest there is a good case for AGW to be nudging the system even further. Not necessarily THE sole driver, but definitely nudging the system. And the CO2 growth rates are just starting to ramp up.
So we have worse droughts in the past with worse current climate drivers added on. Imagine that !
You’d have to be at least curious, and not knee jerk dismissive, if you were a farmer, water catchment manager, or policy maker.
That’s all.
Steve Bloom // June 6, 2008 at 1:21 am |
David, apparently more recent work (discussed in two articles in the May 20th Eos) has found a positive trend in participation. The upshot is that the models predicted on the order of a .3% increase over the last twenty years but an increase of about 1.2% has been measured (the difference being attributed to natural variability rather than model error).
Richard // June 6, 2008 at 3:37 am |
Some things to consider. There should be no agriculture in the Murray Darling Basin (that will get some people hopping). The basin is in a naturally drought prone region of Australia. The flows have been intercepted by Agriculture leaving little to reach the Coorong and Lake Alexandrina. There are many more issues to be considered before blaming this on AGW. Australia is the second dryest continent on earth (Antarctica being the dryest). We farm land that people in the northern hemisphere would regard as unfarmable. We are a land of climate extremes (I did say climate), more so that any other inhabited continent. The temperatures that Tamino shows for the Murray Darling do not seem to gel with the BOM data that I have looked at (although I have to do a more in-depth assessment). There is absolutely no empirical evidence of any AGW influence on Australia’s weather and climate patterns. A recent CSIRO study has revealed century long droughts in the continent’s geological history.
[Response: The temperature data (mean daily high temperature anomaly) were downloaded form the BoM website.]
Luke // June 6, 2008 at 8:47 am |
No evidence of AGW in Australia – hah !
Temperatures, frost trend. Multi-decadal rainfall trends. What more do you want?
Worst inflows into the MDB on record and ongoing.
Well there is good forensic evidence on droughts if you look at the swag of papers I have listed above. A whirl-wind blowing through a junk yard did not assemble that science.
Just because there were worse droughts in the paleo past perhaps does not mean can’t push it some more? And more? Possibility of turning the Pacific into a “semi-permanent El Nino like warm state”?
Interesting point through for planning – do you assume that the your rainfall probability distribution based on the last 120 years is good for the next 30?? Or do you use the available science which says an AGW impact and modify your plans?
Before you write the MDB off – this region has fed the nation for 150 years s well as earning billions of dollars of export income selling grains, cotton, wool, beef and lamb to Europe, the USA, Japan and even Iraq for wheat. And it’s not only farms – the region has major rural towns and cities.
The issue if to know how to roll with the seasons, when to plant, when not to. Farms need to get bigger, be diversified in space nationally (maybe innovatively even having holdings in the USA or South America to hedge against/dodge El Nino). Historically , cotton growers had properties in California and the Namoi Valley in central-north NSW to hedge against El Nino impacts. When one was on, the other was off. But evened out.
Off-farm income and diversification is important. The tax systems needs to be amenable to evening out high year-to-year income variation – don’t want to pay heaps of tax in a good year and have no income in drought years – there is a device not used as much as it could be called Income Equalisation Deposits.
http://www.daff.gov.au/agriculture-food/aaa/fmd/info
Seasonal climate forecasts are of some help, even if they’re not perfect. Putting heaps of fertiliser on a wheat planting in a La Nina year is a better bet than probably wasting it in an El Nino year. Maybe you should consider selling livestock early in an El Nino year and destock.
I thought some of this NZ advice was really good
http://www.maf.govt.nz/mafnet/rural-nz/emergency-management/droughts/challenges/
Given many farmers are hedging on commodity futures knowledge of global climate impacts is increasingly important.
So the question is do we need a new breed of ‘smart adaptable nimble farmers”.
Drought resistance from biotechnology?
New farming systems?
Get out of Murray-Darling completely … hmmmm …. Glass is still half full…..
chrisl // June 6, 2008 at 10:09 am |
Richard makes some good points regarding drought in Australia. The flora and fauna are perfectly adapted to long periods of dry and then the inevitable big wet. The trees are not dieing and animals are not dropping out of said trees. The problems arise when foriegn methods of agriculture are applied, using water hungry crops and animals. For a peach tree, a year of low rainfall is a disaster, for a eucalypt, it’s just time for a rest, which the species has seen thousands of times before.
Luke // June 6, 2008 at 1:27 pm |
You’re very optimistic
About 10,000 river red gums, Eucalyptus camaldulensis, — some 500 years old — would have been dead within a year had not the MDB Commission allocated a special environmental flow to flood critical wetlands. Water now not going to droughted irrigators. Some of these trees are very old “Some of the river red gums were alive when Columbus discovered the Americas. They are part of all Victorians’ heritage,”
This report shows just how incredibly unhealthy sections of the river has become. http://www.envict.org.au/file/Red%20Gum%20Report.pdf Lots of stressed and dying trees. Even back in 2003.
N ow wetlands are turning acid, the massive Coorong wetland is rapidly increasing in salinity and dying.
http://www.abc.net.au/news/stories/2008/05/12/2241583.htm
Yes I’m sure it will all be fine.
http://www.theage.com.au/news/environment/parched-forests-get-an-overdue-drink/2008/05/10/1210131335204.html
A rest indeed – Rest in Peace more like it.
JCH // June 6, 2008 at 1:38 pm |
It can’t be because of global warming.
The drivel was that global warming would be beneficial. Warmth would make it possible to farm new areas. Australia uses very little of its wheat crop. Most of it is consumed by a hungry world, so the loss of that export would make a big difference in the global wheat supply – as seen this year when the crop was way down and wheat prices shot up.
So where are these new wheat fields? People can’t eat eucalyptus leaves. Why are the Canadians being so slow about plowing their softened tundra? Why aren’t we seeing gigantic Alaskan veggies at the supermarket? Where is the rosy scenario that will accompany global warming? It’s missing in action; therefore, this is just natural variation.
David B. Benson // June 6, 2008 at 7:29 pm |
Rather confused about global precipitation. Above there is a citation to a paper (behind a paywall) from Hadley Centre claiming a drought index has increased. Steve Bloom mentioned some papers claiming increased precipitation in last twenty years in response to my link to a ‘precipitation product’ stating there is no secular trend to global percipitation in over 25 years. To add to the mix
http://www.cgd.ucar.edu/cms/wcollins/papers/jcl_2006_v19_p2597.pdf
states “Midlatitude summer drying noted in previous model simulations in a future warmer climate is simulated in the CCSM3, though the relatively small drying does not result in greater soil moisture stress on vegetation in the model.” in the conclusion.
Seems I can take my pick, so I’ll say it doesn’t look to be settled science.
Steve Bloom // June 6, 2008 at 10:54 pm |
David, increased precipitation along with increased drought is unfortunately not a contradiction, and the paper you link discusses results fron a single model from several years ago. You really should read those Eos articles.
David B. Benson // June 6, 2008 at 11:27 pm |
Steve Bloom // June 6, 2008 at 10:54 pm — I’ll be happy to (provided not behind a paywall for me), but I’ll need a better references than just ‘Eos’. Thanks.
Luke // June 7, 2008 at 3:12 am |
Goes back to the original point of taking spatial averages of rainfall over too large an area and imputing a general observation about good/bad. The world’s inherent geography – position of the continents and oceans – plus inbuilt periodic oscillations such as El Nino and others already mean that rainfall is not distributed evenly across the globe. El Nino and La Nina turns some places into drought and others into flood. On/off.
There are winners and losers from El Nino and most probably more winners and losers from additional AGW as well.
Very simplistically – maybe the US/Canadian border will fare better with rainfall, combined with additional warmth and CO2 fertilisation – so extra wheat yield perhaps. Hey maybe George Bush and CIA know this already !! :-)
Of course extra warmth and moisture can also bring new insect plagues as well. And disease.
Mountain pine beetle plagues (Dendroctonus ponderosae) munching through vast new areas of North American conifer forests enabled by warmer conditions. Blue tongue virus and other animal diseases into southern Europe from Africa.
None of this is simple.
Agree that some good references as to whether global drought has increased in recent decades is needed.
As an aside New Zealand has also had record drought in recent times. I think the North Island is now OK but deficits persist in the South. Someone might know more detail.
Luke // June 7, 2008 at 6:21 am |
Today’s news in “The Australian”
http://www.theaustralian.news.com.au/story/0,25197,23822411-11949,00.html
It’s quite dire …
“FOR the past decade, the autumn rains that herald the grain-planting season and produce winter pasture have failed in southeastern Australia.
This year was no exception. Last month was the driest May on record for the country, while autumn was the eighth driest on record.
For the Murray-Darling Basin it was the fourth driest autumn on record, with an average of just 40mm of rain, well below the long-term average of 128mm. Autumn inflows into the Murray River were just 200 gigalitres (200 billion litres), the same as the 2007 autumn’s record-setting low.
The past week has brought the first widespread rains to eastern Australia since February. But, like those summer rains, they have largely missed the Murray River catchment and Victoria.
Murray-Darling Basin Commission head Wendy Craik warns: “There is really no improvement in sight.” Research by CSIRO scientists Wenju Cai and Tim Cowan has detected that, since 1950, Victoria has suffered a 40 per cent decline in autumn rainfall compared with the long-term average. And that decline has been most severe in May. Cai says the decline “is not totally due to climate change but it shows an imprint of climate change”.
Craik points to work undertaken by the Victorian Government for its northern region sustainable water strategy. It found that the inflows into northern Victorian rivers, including the Murray, have fallen in the past decade. In many they are now lower than the levels forecast under climate warming for 2055.
“We are there already,” Craik observes. “We expected we might have to deal with that in 50 years, but we didn’t expect to have to deal with it right now or that we had been dealing with it. The question arises: have we arrived and is this what the future is going to hold for the southern part of the basin or is it going to get worse?”
The strategy report found that, in the past 10 years, the rainfall over almost all of Victoria has been well below average. River flows have been even more severely reduced. The Campaspe River has been 69 per cent below average, the Broken River 48 per cent below, while the Goulburn and the Murray rivers have been 38per cent below the long-term average. The long-term average flow in the Murray is 6595GL. Under medium climate change, the forecast is that it would fall to 4486GL by 2055. But the continuation of the past 10 years of low inflows would result in just 3667GL.
Victorian irrigators are accustomed to high levels of water security: under the long-term average they got their full allocations 99 years out of 100. Under the climate change scenario employed, that would drop to 85 years out of 100, but a continuation of the conditions of the past 10 years would reduce that further to 81. The results were even more severe on the Goulburn, Campaspe, Loddon and Broken rivers.
The irrigation season opens in July and at this stage it looks like the allocations will be zero. Last July all Murray River irrigators had zero allocations, but they later rose to 43 per cent for Victorians, 32 per cent for South Australians and 25 per cent in NSW.
Craik says the water planning and management systems have been “caught on the hop”.
“We have had to put in place special arrangements to meet critical human demand last year and we have it in place again this year. Nobody envisaged that we would have this sort of situation. We thought these were things we could think about and deal with over time, but in fact we have had to deal with them right away.”
Something else has happened in the basin. Rainfall has been this low in the past but river flows were never as low as they have been during the past decade. As Craik puts it: “Average rainfall no longer results in average inflow.” This is thought to be mainly because of higher evaporation due to global warming.
The Murray-Darling Basin has a very dry catchment. Less than 10 per cent of the rain that falls on it ends up in the rivers, compared with 39 per cent in Europe, 48per cent in Asia and 52 per cent in North America. This makes the basin extraordinarily vulnerable to the influence of rising temperatures.
Cai has calculated that a 1C rise in temperature in the basin results in a 15 per cent reduction in river flow or about 1850GL less water in the river. The past three years in the basin were the warmest on record, with last year the warmest yet at 1.1C above average.
The decline in autumn rainfall is critical to inflow because, as Cai explains, it wets the soil so that when the wettest time of the year arrives — winter and spring — the rain runs off the soaked soil and into the river.
Research by Bertrand Timbal, conducted under the South Eastern Australian Climate Initiative, found that rainfall south of a line running roughly from Adelaide to Canberra began declining in late autumn and winter in the 1990s. North of the line (known as the subtropical ridge), rainfall has declined in summer and autumn since 2000. Timbal reported growing evidence that lower rainfall and reduced run-off in southeast Australia is linked to global warming.
Craik says it is hard to believe it could be anything else. “The temperature effect: linked to climate change. The decline in autumn rainfall: again linked to global warming, so it is hard to believe that climate change isn’t a significant player in this drought.”
Hopes were high that last year’s La Nina event in the Pacific, which usually brings rain here, would rescue the basin from drought.
National Climate Centre head Michael Coughlan says the previous big La Nina event, in 1989, produced a subsequent autumn rainfall across the basin of 267mm. But this autumn it received just 40mm. However, Coughlan points out that La Nina did at least bring good rainfall during the summer.
“From November through January, summer rainfall, we had the sixth wettest four-month period on record,” he says. But that rainfall was not sufficient to wipe out the deficit of the previous two years, let alone the past six dry years.
Cai says there are two processes that affect May rainfall in southeastern Australia: the sea surface temperature in the Indonesian through-flow region in the western Pacific, which is part of the El Nino-La Nina cycle, and the subtropical Indian Ocean.
There have not been many La Nina events during the past 30 years. Cai says: “The system seem to be stuck in the quasi-permanent El Nino phase (dry in eastern Australia).” Then last year, when one developed, it wasessentially blocked by rising temperatures in the Indian Ocean.
Barry Batters grows wheat, barley, oats, faba beans, chickpeas and lentils, in partnership with his wife, Jenny, near St Arnaud in central Victoria. He describes his autumn rainfall this year as quite a bit below average, adding: “It depends what average you are talking about. If you are talking about the last 10 years’ average, it is about on par. But over the lifetime of rainfall it is definitely below average.”
Batters says they no longer get the autumn break, or planting rain, they used to. So farmers have adjusted by planting on whatever rain they get and conserving moisture. Instead of ripping out weeds and ploughing, which opens the ground and increases evaporation, they practise minimum till. That means spraying weeds with herbicides and planting the seeds directly into the soil.
“Nowadays the opportunities (to plant) aren’t as great as they used to be. You have to be quick. Everyone is looking at ways all the time to conserve the moisture when you sow,” Batter says.
Victorian dairy farmer Stephen Mills is the chairman of Irrigation Australia, a director of the Murray-Goulburn Co-operative, and was recently appointed to the Victorian Government’s future farming advisory panel. He readily admits the reduction in rainfall is making it harder for farmers to remain productive and viable. “But I still think there is a lot of hope for the way that farmers approach their production systems,” Mills says. “We will see enormous changes in the next decade or so. We have seen changes already that perhaps we haven’t recognised.”
Mills says dairy farmers are adopting new irrigation technologies such as “sub-surface drip and very fast-flow surface flood irrigation, which are proving to provide very significant production increases while maintaining very efficient water use”.
They are growing more lucerne, a deep-rooted crop that responds quickly to rainfall and needs less irrigation, and they have shifted their main irrigation season from spring to autumn.
Mills says that, after deregulation in 2000, there were a lot of changes. He thinks changes will continue, pointing out that “there are enormous challenges”.
Milk prices are high and the north Victorian milk supply “has really held up fairly well, with very low water allocations and low rainfall. That is a good sign that dairy farmers are confident about the future and are willing to change their practices.”
But across the Murray in NSW, dairy farmers have effectively had three years without a water allocation “and they are looking at zero again this year”, Mills says. “Those farmers are really starting to struggle; their resilience has been hit hard. Those guys, even at the milk price today, are still questioning if there is a future for them in that sort of rainfall scenario,” he says.
Chris Mitchell, director of the Centre for Australian Weather and Climate Research, a partnership between CSIRO and the Bureau of Meteorology, says the southeast rainfall decline is “a very active area of research. I don’t think there is an answer that the scientific community has settled on.”
But he adds that there is no doubt Australia has warmed as a result of global warming.
“The extent to which that is affecting rainfall, compared (with) the natural variability that we have in our system, is really very, very hard to disentangle.”
Mitchell argues that it is important to manage on the assumption the downturn will continue.
“If you are assuming that rainfall will return, you won’t try to adapt to a drier climate, and when you get hit by those dry years it will impact your bottom line, your productivity and your system much more. Whereas if it gets wetter, the chance is you will get a bumper crop, but the other years you will be OK.” “
Greg // June 8, 2008 at 1:49 am |
If you want to take on bodgy statistics Tamino, look no further than this one:
“Research by CSIRO scientists Wenju Cai and Tim Cowan has detected that, since 1950, Victoria has suffered a 40 per cent decline in autumn rainfall compared with the long-term average.”
Compare and contrast the reality:
http://www.bom.gov.au/cgi-bin/silo/reg/cli_chg/timeseries.cgi?variable=rain®ion=vic&season=0305
[Response: If I examine the reality, will you accept it? See the next post.]
Lab Lemming // June 11, 2008 at 12:45 pm |
All this talk about rain… But has anyone tried plotting the change in the size of the snowpack with time? The greatest decrease in flow seems to be the August-October time period.
Richard // June 14, 2008 at 1:06 pm |
Luke,
Just because there are climate changes does not mean it is AGW. Why is it that any climate variability in this day and age is blamed on anthropogenic causes. My comment about century long droughts is just that there is natural variation and that variation can be quite extensive. As for the MDB the rainfall anomaly plots do not show a long term multi decadal decline in rainfall:
see: http://www.bom.gov.au/cgi-bin/silo/reg/cli_chg/timeseries.cgi?variable=rranom®ion=mdb&season=0608
The 11 year running mean is tracking at about -2mm rainfall from the 1961-1990 base line. This is for Winter rainfall. The Autumn anomaly is well below the baseline but so it has for most of the 20th Century.
As for southwestern Australia, there have been quite significant declines in Autumn and to a lesser extent in Winter. The only antrhopogenic influence I can think of here is the high level of land clearing for agriculture. Almost no temperature values for SW stations show any significant increase in temperature (see NASA GISTEMP station data). The exception is for Perth which surprise surprise is a rapidly growing city. The rural stations show little or no increase in temperature. In fact, Albany and Esperance show overall declines in temperature over the time series (about 1960 to current).
Luke // June 14, 2008 at 10:28 pm |
Richard – we’ve been over this ad nauseum by now here http://tamino.wordpress.com/2008/06/08/victoria-rainfall-fall-rain/#comments – have you read that? Have you read the papers I have tabled above in this thread?
The Murray Darling is massive place. Quoting the entire basin is totally spurious – the reality is that Murray inflows are the worst on record caused by the likes of Figures 1 and 3 here.
http://www.bom.gov.au/climate/current/statements/scs14.pdf – you don’t those maps are jaw-dropping !!
It’s what is going into the Murray catchment is most of the issue.
As for “The only anthropogenic influence I can think of here is the high level of land clearing for agriculture. ” – so that means if you don’t know about it – it doesn’t exist? Wow !
Temperature changes locally in SW WA are not relevant – greenhouse forcing and stratospheric ozone depletion are thought to have changed southern hemisphere circulation systems.
Ever thought of reading the Indian Ocean Climate Initiative reports http://www.ioci.org.au/ or I might just leave it Cai and Cowan to summarise here http://www.agu.org/pubs/crossref/2006/2006GL028037.shtml There is a good case to expect some anthropogenic influence.
Richard // June 16, 2008 at 5:55 am |
Well Gee. More results from Models. If it is from a model it must be true! Look at just about any RURAL met station in the southern hemisphere (include Antarctica here) and try to see any major climate warming. Then have a look at rural stations in the Northern Hemisphere. Then have a look at the 30year satellite data sets. Tell me there is even close to the warming predicted by your indisputable climate models.
[Response: I have looked at those rural met stations from the southern hemisphere; lots of them. And stations from the northern hemisphere, and the satellite data. Obviously you haven't.]
Luke // June 17, 2008 at 5:51 am |
You are joking surely?
http://www.bom.gov.au/cgi-bin/silo/reg/cli_chg/trendmaps.cgi?variable=tmean®ion=aus&season=0112&period=1970
And 90% of the discussion here has been about observations not models.
Luke // June 17, 2008 at 8:58 am |
An ongoing problem into the future
http://www.abc.net.au/news/stories/2008/06/17/2277161.htm
Eliot // July 8, 2008 at 1:37 pm |
Thanks for this blog. I came across Greg’s lines on Andrew (our favourite climate change sceptic) Bolts blog. Same points from Greg as are well roundly refuted here. I’ve been looking for somewhere that does some of the hard thinking and analysis on the topic, as the “global cooling since 1998″ thing is leaving me a little weary and curious. Sorry I cant add anything to the analysis, but as an Australian in an environment where im taking in a lot of local, superficial scepticism, this sort of site is most welcome!
You would have a field day on bolts blog by the way… hes been very shrill of late: http://blogs.news.com.au/heraldsun/andrewbolt/
Luke // July 14, 2008 at 3:11 am |
Tamino – an interesting exchange on some new CSIRO drought modelling arising from this review http://www.bom.gov.au/climate/droughtec/
http://landshape.org/enm/drought-exceptional-circumstances-reply/
http://landshape.org/enm/drought-exceptional-circumstances-reply/
Begs the question of relevant significance tests, use of different GCMs and averaging of results, and what level of significance is even appropriate ? 5% 10% ?
You may have a view on this evolving science issue.
Situation on the ground is still grim http://www.abc.net.au/news/stories/2008/07/10/2299744.htm
Roger Wickham // July 22, 2008 at 1:41 pm |
Need rain, maybe I can assist.Look at the Fairburn dam dry one minute over flowing the next,guess what ?
Jonathan Lowe // October 6, 2008 at 8:17 pm |
“It even suggested that over the long term, Australia is getting increased rainfall, and refers to a post on a website titled gustofhotair as supporting evidence”
“The Australian Bureau of Meteorology provides climate data for Australia throughout the 20th and 21st centuries, from which we can see some of the changes in rainfall over the last 100 years. Overall, Australia has has increased rainfall over the last century”
“The website claims to present the author’s “statistical analysis of Australian Weather,” but I don’t see evidence of very much statistical analysis on the site. The author claims to be expert in statistics, but I don’t see any evidence of that at all.”
Lol, look harder, and please try not to contradict yourself within a couple of paragraphs, it doesn’t look good for your arguement.
Ohh and the Murray Darling Basin you say is “is the worst [drought] in Australia’s history”
Take a look here at the data here: http://www.bom.gov.au/cgi-bin/silo/reg/cli_chg/timeseries.cgi?variable=rain®ion=mdb&season=0112
and tell me if you think its the worst in history. There is no statistical evidence that the murray darling basin is significantly decreasing in rainfall.
Jonathan Lowe // October 6, 2008 at 9:55 pm |
Oh also, your graphs are fantastic, and I like the way you have used a smoother to show that the current rainfall in the Murray Darling Basin is bad, almost as bad as 1900.
However, lets look at the actual data and find out when the worst the Murray Darling actually was.
And the answer is between 1944 to 1946 the rainfall of the Murray Darling was in fact less than currently.
In fact if we take the last 4 or 5 or 6 or 7 or 8 or 9 or 10 years average annual rainfall and compare that to 1946 and the 4 to 10 years before that, we see that in every single instance rainfall was a lot less than it is now as shown below:
Av.Prev.Years to 2007 to 1946 Difference
4 423.5 361.1 62.4
5 429.0 391.9 37.1
6 405.6 402.1 3.6
7 407.0 386.6 20.4
8 428.9 406.5 22.4
9 447.0 399.6 47.4
10 460.9 397.5 63.4
So rainfall back around that time was around 30-40mm less rainfall than currently. I’m not saying that rainfall isn’t low now, but it’s not the worst in history and there is also no statistically significant decreasing trend like suggested.
[Response: Drought depends on more than just rainfall. Not clear enough for you?]
Jonathan Lowe // October 7, 2008 at 12:58 pm |
Hi,
after my long 2 comments which show that the Murray Darling Basin is not in its worst drought in Australia’s history based on rainfall information, comments about how you criticise my website for saying that rainfall is increasing and then two paragraphs later confirm that the ABM say the same thing I get a simple reply like that?
What about the other comments? Also you should delete the “smoother” that you added to the Murray Darling rainfall graph. A smoother is meant to highlight the trends of a graph which might otherwise be harder to see. Your smoother is so ridicules that the nature of it alone will exaggerate the start and the ends of your data. Clearly a better smoother is the one on the ABM website as shown here
http://www.bom.gov.au/cgi-bin/silo/reg/cli_chg/timeseries.cgi?variable=rain®ion=mdb&season=0112
which shows no significant trends since 1900. My conclusions of this is that either you are incapable of accurate statistical analysis by using such a smoother, or that you used it on purpose to alarm and exaggerate your point. Lets hope its the former.
And in reply to your comment about drought is more than just rainfall. I completely agree, however I was merely informing you of the fact that the Murray Darling Basin has had less rainfall in the past.
Your correlation of pan evaporation and maximum temperature is interesting, but somewhat simple. Pan evaporation is also highly correlated with rainfall. Greater rainfall years = less pan evaporation years. Sounds strange? That’s because maximum annual temperatures are also highly correlated with rainfall. Years of high temperature also have years of lower rainfall. It makes sense. If we have greater cloud cover one year, most likely we’ll have greater rainfall, lower maximum temperatures and hence less pan evaporation. If we have less cloud cover in a certain year, most likely we will have less rainfall, higher temperatures and greater pan evaporation.
All these variables, and more, are intercorrelation, and have to be looked at in whole. Pan evaporation quite clearly according to the graph
http://www.bom.gov.au/cgi-bin/silo/reg/cli_chg/timeseries.cgi?variable=evap®ion=mdb&season=0112
has not increased or decreased in the last 32 years. And even though you say, that 32 years is not enough to find a trend, perhaps this is only because the data do not suit your argument.
[Response: This is why it's just about impossible to get through to you. Has pan evaporation really neither increased nor decreased in the last 32 years? Has it done both? What analysis did you apply? Are you even aware that "trend" doesn't mean the same thing as "linear trend"?
You repeatedly say "look at this graph" then pronounce that there's "no change" without even mentioning any analysis performed or any possibilities considered. You take a real correlation (between evaporation and temperature) with a clear physical causative link and hand-wave it away, expecting us to buy that "related to other variables" bullshit. You take a clear and statistically sound decrease in recent long-term rainfall and attribute it to the choice of smoothing, mainly because you can't wrap your mind around the concept that trends don't have to be linear.
No previous historical records for the Murray-Darling Basin indicate the combination of reduced rainfall and increased temperature observed today.]
[edited]
Jonathan Lowe // October 7, 2008 at 10:14 pm |
Hi and thanks for the reply.
Firstly I was wondering why my comment was edited? Not all of it was shown by yourself. And also you failed to comment on my comments about how you criticized gustofhotair for claiming that Australia’s rainfall has increased and then quoted the ABM a few paragraphs later who said that Australia’s rainfall had increased. I am still waiting for that one.
As for the statistical analysis, I could do it on the data but it is quite clear with the naked eye that there is no significant trend, linear or otherwise has occurred in the last 32 years of pan evaporation. But hey, I did it anyway. As shown by the links just below, there is quite clearly a seasonal but no significant increasing or decreasing trend. To say otherwise is to be blind.
http://www.gustofhotair.com/MDB1.jpg
http://www.gustofhotair.com/MDB2.jpg
http://www.gustofhotair.com/MDB3.jpg
[Response: This is why it's impossible to get through to you. You haven't done any analysis at all.
You just plotted graphs, and frankly, you've done a lousy job of that. Then you draw a conclusion based on "it is quite clear with the naked eye ..." What's "quite clear" is that when it comes to data analysis, you don't know what you're doing.
Here is a graph of monthly pan evaporation anomaly (departure from the seasonal pattern) for the MDB from 1975 to the present, plotted on a scale big enough that people can actually SEE something.
Here is a 4th-degree polynomial fit to that data, showing that pan evaporation was higher in 1980 and 2005 than it was in the early 1990s. The difference is statistically significant, as is the 4th-degree polynomial fit is as well. Goodbye to your ridiculous "no significant increasing or decreasing trend" -- there's both.
And since you seem to like moving averages so much, here are 11-year moving averages showing the same pattern, with error bars illustrating the statistical significance of the changes. Here is the same thing, with 5-yr moving averages.
This seems to be your modus operandi -- produce a few graphs, draw a sweeping conclusion based on the "naked eye" and then make pronouncements about your in-depth statistical analysis when in reality there isn't any.
As for deleting the rest of your comment, and not answering all of your objections, I prefer to spend my time on those who have something intelligent to say and some real analysis to back it up.]
Jonathan Lowe // October 9, 2008 at 7:02 am |
I would put it to you that the reason that you edited my post is because by including it made you look stupid. It included links to accurate and thoroughly research statistical analysis, which showed that almost all of Australia’s recent warming has been caused by an increase of sunshine hours and a decrease of cloud cover. MY theory is that if you had not edited such a comment, you wouldn’t be able to make comments such as “when it comes to data analysis, you don’t know what you’re doing.” And “make pronouncements about your in-depth statistical analysis when in reality there isn’t any.”
[Response: Again: you didn't provide any analysis at all. And the fact that you really don't even know what you're doing, is truly pathetic.]
This is a terrible case against freedom of speech. [edit]
[Response: Who the hell do you think you are? This is MY HOUSE. I didn't invite you. You just decided to "drop in" and leave a pile of shit. If you want to do that in your own house, go right ahead, but "freedom of speech" is no excuse to defile mine.]
Alan Woods // October 10, 2008 at 5:41 am |
Tamino: what is the justification for using a 4th degree polynomial fit for analysing the pan evaporation data? Is there a rule you can follow in choosing the correct method of analysis.
How do you show the difference in various years is statistically significant?