IS the ongoing drought in the Murray-Darling Basin affected by climate change? The simple answer is that there is no evidence that CO2 has had any significant role. Like it or not, that is the science.
In fact, the drought was caused by an entirely natural phenomenon: the 2002 El Nino event. This led to particularly low rainfalls across eastern Australia. The subsequent years were either neutral or weak El Nino conditions. Significantly, neutral conditions are not sufficient to break a drought. In 2006, we had a return to El Nino conditions which further exacerbated the drought. What we didn't have was a strong La Nina.
Last year finally brought a La Nina event but it was relatively weak. It produced a number of major storm events in coastal areas and some useful rainfall in the Murray-Darling basin and elsewhere. Approximately half of NSW drought-declared areas were lifted out of drought (albeit into "marginal" status) and Sydney's water supply doubled in the space of a few months.
This was the first rain-bearing La Nina since 1999 but proved insufficient to break the drought. In short, the drought was initiated by El Nino, protracted by further El Nino events and perhaps more importantly, the absence of substantial La Nina events.
Despite the known causes of the drought, many have claimed that CO2 emissions are to blame. There have been arguments put forward to justify this claim, all eagerly adopted by various groups, but none of which have serious merit.
A key claim is that the multiple occurrence of El Nino is a sign of climate change. This is speculative at best. Recent analysis showed the nine-year absence of La Nina was not unusual. In fact long-term records demonstrate alternating periods of 20-40 years where El Nino is dominant, followed by similarly extended periods where La Nina dominates. Ominously, the data demonstrates that it is possible to go 14-15 years without any La Nina events. The consequent drought would be devastating but entirely natural.
The observation that El Nino and La Nina events cluster on 20-40 year, multi-decadal timescales is an important one. It demonstrates that Australia should always expect major changes in climate as a function of natural variability. When viewed in this light, the drought is most likely a recurring feature of the Australian climate.
A more recent claim is that higher temperatures are leading to increased evaporation of moisture. The weather bureau acknowledges that rainfall from September 2001 until now has not been the lowest recorded, however much has been made of the fact that consequent inflows have been the lowest. It has been claimed increased evaporation, driven by climate change, can make up this discrepancy. Indeed, Wendy Craik, the chief executive of the Murray Darling Basin Commission has stated that temperatures were warmer, leading to more evaporation and drier catchments.
This is disturbing to hear from the head of the MDBC, as it is completely at odds with the known physics of evaporation. While it sounds intuitively correct, it is wrong.
When soil contains high moisture content, much of the sun's energy is used in evaporation. Consequently, there is limited heating of the surface. When soil moisture content is low (as occurs during drought) nearly all of that energy is converted into heating the surface, and air temperatures rise significantly. Consequently, higher temperatures are due to the lack of evaporation, not a cause of significantly higher evaporation.
Cloud cover also provides a major control on air temperatures. El Nino delivers less rainfall but also less cloud cover. This has a major impact on the amount of the sun's energy reaching land; far greater than the trivial increase in radiant energy caused by increased CO2. Again, in the absence of soil moisture, air temperatures increase.
These are known and accepted processes of environmental physics and are not contentious. They are ignored because they detract from the simple message that we should sign up to the concept of "dangerous climate change" and an emissions trading scheme. After all, who would pay for carbon emissions if they were not proven to be detrimental? Who would provide extra funds for climate change science if it wasn't a proven significant factor compared to natural climatic variability?
None of the above is to say that CO2 is not having some effect; the atmospheric CO2 concentration has risen and this is largely attributable to anthropogenic emissions. CO2 is a radiatively-active gas and leads
to a minor increase in downward radiation. However, there is no evidence that this is in any way significant, especially when compared to the naturally varying processes that dominate rainfall variability and evaporation.
We do know why inflows are so low and why various ecosystems of the Murray-Darling are in crisis: the system is over-allocated and has experienced a growth in groundwater extraction and in the number of farm dams preventing rainfall from becoming run-off. This is due to a failure of planning, management and leadership from the relevant authorities. Under these conditions, when a prolonged drought strikes, the system collapses.
This is a man-made problem but not one that is attributable to CO2.
Craik is not alone in her desire to view CO2-induced climate change as proven and affecting the drought. Numerous politicians, environmentalists and especially scientists have made spectacular leaps of faith in their adherence to the doctrine of climate change over recent years, too many to document here. However, the most literally fantastic claim on climate change must go to Kevin Rudd, who has guaranteed that rainfall will decline over coming decades; one can only assume he's based his view on deficient climate models and bad advice.
Perhaps our leading climate authorities who have played such a prominent role in fomenting speculation about climate change, and who apparently adhere to the notion that climate is amenable to prediction, should also point out that these models cannot reproduce the observed multi-decadal variability of El Nino and La Nina in anything like a realistic manner.
Given the uncertainty of El Nino and La Nina behaviour, one clearly cannot predict the future. There is no direct evidence of CO2 impacts on the drought, nor is there any rational basis for predicting rainfall in 30 years time. One just hopes that sensible and sustainable management from our leaders will enable struggling rural communities to weather the vagaries of climatic and political extremes.
Steward Franks
Newcastle, Australia
Stewart Franks is a hydroclimatologist and an associate professor at the University of Newcastle School of Engineering. He is president-elect of the International Commission on the Coupled Land - Atmosphere System.
This article has been republished from The Australian with permission from the author.
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Emissions not making rivers run dry, The Australian, Stewart Franks, September 12, 2008
"Now I’m starting to understand SJT ,so the LIA could be caused by humans afterall, well I never."
I think I said "this change", the change that is happening now. You can chill out again.
Cohenite,
"...As to the MWP; it existed; historical accounts prove that; the issue for AGW is whether the temps back then were such so as to disprove the AGW orthodoxy that 20thC temps and rates are exceptional..."
the MWP may or my not have existed, there is no definitive evidence either way. Again you make your choice based in supporting your paradigm.
Current evidence suggests it is warmer now, if you look at the material being exposed as Glaciers retreat in Canada, Alaska, the Alps, in Chile, New Zealand, typically this material is more than 3000 years old. This correpsonds with a warmer period.
Using the Milankovitch cycles as a guide the World should be slowly cooling. This led even led Arthur C Clarke (who was actually quite a good scientist) in the 1940s to declare we should burn coal to avoid the next ice age.
Now I'm starting to understand SJT ,so the LIA could be caused by humans afterall, well I never.
Of course that 1.5 metre increase in sea level 4,000 years ago could be caused by humans as well I suppose and the MWP gee you be should publish and be damned you're sure to cause a sensation.
Gosh those silly loons who suggest that the LIA was caused by less solar radiation and volcanoes are real dullards because it COULD have been the human race that caused that 5 century misadventure.
Seriously I know that fanatical AGW urgers are at times extreme and delusional but this just about takes the cake.
"Once again our planet behaving oddly all on its Pat Malone without any help from humans at all."
That's why scientists conduct research. The result of the research is that much of this change is caused by us.
Thats the problem it's not my LIA but everyones LIA and some very cold temps were endured by those people over five centuries with the Maunder and Dalton minimums being the coldest.
The reason given today for the LIA is Volcanic activity and low levels of solar radiation, remember the year without a summer referenced in literature around the world?
Once again our planet behaving oddly all on its Pat Malone without any help from humans at all.
Cohenite: during the 60’s I was actually fully employed maintaining a range of imported instruments and sometimes building new ones including non linear devices but mostly at arm length from subs (sub standard reference) for temperature, humidity, pressure and flow. Where suitable calibration points like ice water and boiling point did not cover the range we improvised. Flash point of high grade transformer oil was one, liquid salt was another we used in the back yard lab.
Building up instrument standards outside a physics department is a very crafty business indeed and that’s why our outfit became trusted enough to be the first independent contactors in the local petro chemical industry with defacto international status in all manner of safety codes across companies in a complex.
In understanding trends, instrument accuracy is less important than reliability. The pattern of response has to be well known. Where as calibration is routine, the rest is an art with those most responsible hence the sort of BoM paper I linked to above. Smart Alecs fresh on the scene were my biggest problems. Finding indisputable proof for all ears and eyes of some pending event in time was another so I often had to act alone. In using initiative though we must never loose respect for our cobbers on the same job. That’s probably the hardest thing to maintain.
Neville after you have held a lot of thermometers and wondered how they could so differ the response is simple; go for all the ones that agree almost exactly and hope that is the majority from the bunch. Rejecting those you made in this first elimination process is particularly hard, but believe me fixing each one to conform later is the real chore. Have sympathy for those still struggling with old weather records at BOM hey because they probably never knew either the instrument maker nor the station minder.
“Once again let’s take the LIA and use the beloved Wiki as the reference.
The reduction in temp during that period is put at 1c to 1.5c”
Neville can you seriously imagine me trying do justice to your LIA armed only with a piece of wood as reference?
Using Gavin's point about the inaccuracy of the earlier temp record let's ask the obvious, how do you know the earlier records are not hopelessly low.
In other words if you don't accept the record you must rely on a particular prejudice or bias.
Once again let's take the LIA and use the beloved Wiki as the reference.
The reduction in temp during that period is put at 1c to 1.5c, but since 1850 the planet has only recovered .7c of that reduction, so what is all the fuss about.
In the last 100 years the planet has been subjected to more solar radiation than at anytime in the last 10,400 years, surely that's worth some part of that .7c as well?
What happens when Spencer's team gradually gets full recognition for their work showing a negative feedback to extra co2, he predicts it may take 3years at least before the fraudsters are slowly exposed and throw in the towel.
In the last month even rags like the Age have allowed many serious scientists to write columns ( in the Business section) deriding AGW so it is slowly getting a run in the MSM.
The easy answer to all this of course is show us the positive feedback in the real atmosphere and show us that pesky hotspot.
Just a hint it hasn't been done yet, I wonder why?
"pre-satellite data was extremely variable"
I really don't get this love of satellite data. It has been highly variable and is not a direct measurement, but an interpolation of temperature. It's one more tool in the warchest, but the reverence given it puzzles me.
Cohenite - dude - what you need is to be forced to come up with a quality Australian met variable set given nothing other than the rawest of raw data and a pocket calculator. Then we'll see how good you are. Toorak and Nicholls are very serious guys - if you go after them - better pack a bloody big knife aka Crocodile Dundee. Sure of your facts are you? That's science sure too - not legal dodgy sure.
Bullsheeet Cohneite - you'd like them to use pre-1910 temperature data measured with Glaisher stand.and compare that to Stevenson screens - are you on drugs mate !?
I mean GISS smish - after all McIntyre's grunging around how is our understanding of global temperature trends modified - errr - ummm - not all all - has the same wiggles as the satellite stuff (which is never questioned and it bloody well should be!?).