Finding anthropogenic global warming (AG
W) shapes in the fog of variability is a major challenge, simply because natural climate variability is large. And then the problem becomes attributing those changes to a climate mechanism in an interlinked dynamic climate system.
One of those climate detective stories taking some intriguing twists and turns is the rainfall decline in Western Australia which has been the impetus for the Indian Ocean Climate Initiative (IOCI). Their web site explains:
“In southwest WA, a drying trend has been observed … The rainfall decline has been most apparent in late autumn and early winter, with a major drop in rainfall totals occurring in the 1970s, and possibly another more recently in the 1990s. Averaged across southwest WA, a step decrease in total annual rainfall of almost 10% was seen in the mid-1970s, though individual locations would have experienced a greater decrease.”
Antarctica, in particular both stratospheric ozone decline and tropospheric greenhouse forcing over Antarctica impacting a positively trending southern annular mode (SAM) with the strengthening circumpolar vortex, have been the focus of explanations for the rainfall decline (see for example Thompson and Solomon, 2002, in “Interpretation of recent southern hemisphere climate change”).
For a description of the SAM – http://www.atmos.colostate.edu/ao/introduction.html
Shindell and Schmidt (2004) claim that both Antarctic ozone depletion and increasing greenhouses gases have contributed to these trends. And with an interactive climate model including the stratosphere and both composition changes reproduces the vertical structure and seasonality of observed trends.
Arblaster and Meehl (2006) asserted that a recovery in the ozone hole would be matched by inexorable increase in greenhouse gases:
“Although stratospheric ozone losses are expected to stabilize and eventually recover to preindustrial levels over the course of the twenty-first century, these results show that increasing greenhouse gases will continue to intensify the polar vortex throughout the twenty-first century, but that radiative forcing will cause widespread temperature increases over the entire Southern Hemisphere.”
Fundamentally, the SAM is an expression of the meridional pressure gradient between the sub-Antarctic and middle latitudes. The mode has been increasing towards its positive polarity (in the annual, summer, and autumn means) since the late 1960s, leading to lower (higher) surface pressures over Antarctica (southern mid-latitudes) (Polar Meteorology Group). Although Arblaster et al (2010) in a modelling exercise now suggest that ozone hole recovery will indeed lead to SAM reversing trends in coming “decades”.
In an apparent vindication of the unusual nature of the SWWA rainfall decline, van Ommen reported in Nature Geoscience (2010) a correlation between Law Dome snowfall and SW WA rainfall. (Law Dome – 66°44′S 112°50′E, a large ice dome which rises to 1,395 m directly south of Cape Poinsett, Antarctica) And that the SW WA drought sequence was unusual as being the largest anomaly in the last 750 years and outside the field of variability.
So back in 2006, the trail seemed to be closing on anthropogenic climate change in the Antarctic and associated changes in southern hemisphere circulation (SAM) as being responsible for the decline in SW WA winter rainfall.
Cai and Cowan (2006) in GRL stated:
“It is not clear why the reduction occurs in the winter months, when the observed SAM trend is weak, but not in the summer months, when the observed SAM trend is strongest. It is also not clear to what extent the reduction is attributable to anthropogenic forcing and is congruent with the SAM. Using IPCC AR4 20th century model experiments and available observations, we show that in winter the mid-latitude center-of-action of the SAM is closest to SWWA latitudes, compared to other seasons. As a result, there is a statistically significant relationship between the SAM and SWWA rainfall in winter, but not in other seasons. The observed winter SAM trend, though not statistically significant, accounts for two thirds of the observed winter rainfall reduction.”
At a 2007 conference Cowan reported ” Interannual / multidecadal variability linked to the SAM” and “about ½ of rainfall decline attributable to anthropogenic forcings”.
However, in 2007, Meneghini et al reported:
“The AOIR (Antarctic Oscillation Index regional version) accounts for more of the winter rainfall variability in southwest Western Australia, southern South Australia, western and southern Victoria, and western Tasmania than the Southern Oscillation Index. Overall, our results suggest that changes in the SAM may be partly responsible for the current decline in winter rainfall in southern South Australia, Victoria, and Tasmania, but not the long-term decline in southwest Western Australian winter rainfall”.
Perhaps the downfall of what seemed to be a good story on SAM came from Feng et al (2010) in Journal of Climate. There landmark paper on a new index, the southwest Australian circulation, begins:
“Previous studies have raised the possibility that the recent decline in winter rainfall over southwest Western Australia (SWWA) is related to the concurrent upward trend in the southern annular mode (SAM). On the basis of an analysis of 60-yr (1948–2007) reanalysis and observed data, the authors suggest that the apparent inverse relationship between the SAM and SWWA winter rainfall (SWR) is caused by a single extreme year—1964. It is shown that both the negative and positive phases of the SAM have little impact on SWR in the case that data for 1964 are excluded from the analysis. In addition, for periods prior to and after 1964 in the case that data for 1964 are excluded, the apparent relationship between the SAM and SWR becomes insignificant, and the circulation anomalies with respect to SWR appear to be an SAM-like pattern for which the anomalies at high latitudes are not significant. The result indicates that the SAM does not significantly influence the winter rainfall over SWWA. Instead, the variation of SWR would be more closely linked to the variability in regional circulations…
Feng et al (2010) continue:
“It is found that the climate of southwest Australia bears a strong seasonality in the annual cycle and exhibits a monsoon-like atmospheric circulation, which is called the southwest Australian circulation (SWAC) because of its several distinct features characterizing a monsoonal circulation: the seasonal reversal of winds, alternate wet and dry seasons, and an evident land–sea thermal contrast. The seasonal march of the SWAC in extended winter (May–October) is demonstrated by pentad data. An index based on the dynamics’ normalized seasonality was introduced to describe the behavior and variation of the winter SWAC. It is found that the winter rainfall over SWWA has a significant positive correlation with the SWAC index in both early (May–July) and late (August–October) winter. In weaker winter SWAC years, there is an anticyclonic anomaly over the southern Indian Ocean resulting in weaker westerlies and northerlies, which are not favorable for more rainfall over SWWA, and the opposite combination is true in the stronger winter SWAC years. The SWAC explains not only a large portion of the interannual variability of SWWA rainfall in both early and late winter but also the long-term drying trend over SWWA in early winter.
The well-coupled SWAC–SWWA rainfall relationship seems to be largely independent of the well-known effects of large-scale atmospheric circulations such as the southern annular mode (SAM), El Niño–Southern Oscillation (ENSO), Indian Ocean dipole (IOD), and ENSO Modoki (EM). The result offers qualified support for the argument that the monsoon-like circulation may contribute to the rainfall decline in early winter over SWWA. The external forcing of the SWAC is also explored in this study”.
And what more do we know about what might become of the SWAC?
IPCC climate change simulations diagnose that the Hadley circulation will weaken and expand polewards as a result of climate change. Associated with this is an expansion of the subtropical dry zone. Additional work by Ummenhofer (2008) has shown changes in the Indian Ocean SST may provide another forcing to SWAC.
The potential for the SWAC to become a seasonal climate forecasting tool for SW WA remains an exciting possibility.
********************
Graphic
http://www.ioci.org.au/pdf/Fact%20Sheet%204.pdf
References
http://www.lasg.ac.cn/staff/ljp/data-NAM-SAM-NAO/SAM(AAO).htm SAM index
http://polarmet.osu.edu/acd/sam/sam_recon.html Polar Meteorology Group reconstructions
http://www.ioci.org.au/index.php?menu_id=18 IOCI
http://www.ioci.org.au/pdf/Fact%20Sheet%204.pdf IOCI on rainfall decline
http://www.atmos.colostate.edu/ao/ThompsonPapers/ThompsonSolomon_Science.pdf
http://www.agu.org/pubs/crossref/2004…/2004GL020724.shtml Shindell and Smith
http://www.cawcr.gov.au/bmrc/clfor/cfstaff/jma/arblaster_meehl_sam.pdf
http://www.cgd.ucar.edu/ccr/publications/arblaster_future_sam_2011.pdf
http://www.nature.com/ngeo/journal/v3/n4/full/ngeo761.html#a1 van Ommen
http://www.agu.org/pubs/crossref/2006…/2006GL028037.shtml Cai and Cowan 2006
http://www.clw.csiro.au/conferences/GICC/cowan.pdf Cowan 2007
http://www.earthsci.unimelb.edu.au/~ihs/publication_pdfs/Meneghini%2BSimmonds%2BSmith_2007_IJC_27_109-121.pdf Meneghini et al
http://journals.ametsoc.org/doi/abs/10.1175/2010JCLI3667.1 Feng on SAM in SWWA 2010
http://www.cmis.csiro.au/Yun.Li/Papers/reprints/2010_JCLI_SWWA%20Monsoon_Feng_Li_Li.pdf Feng 2010 on the SWAC
http://www.csiro.au/news/New-climate-index-solves-south-west-WA-rainfall-riddle.html CSIRO on SWAC
http://web.maths.unsw.edu.au/~ccumm/Ummenhofer.etal_2008_SWWA.pdf
Jennifer Marohasy BSc PhD is a critical thinker with expertise in the scientific method.
The Walker is not weakening:
http://landshape.org/enm/files/2011/01/walkerarticle.pdf
That of course has flow on ramifications for any conclusions about any alterations in any other circulation system; this is an odd effort with some interesting details about natural process more or less shoved together with the usual pronouncements about AGW influence.
tsk tsk – the SOI is not Walker – the problem with lack of peer review dear boy.
Do try to digest the references. I know real science can be confronting.
This article seems to be referring to studies of recent times ie the last 80 odd years. Is there no long-term record of rainfall in SW WA – the geological record. 80 years is a fly speck on the backside of an elephant in terms of time (and climate) and if there is no study of the long term any pronouncements about change are too imprecise. And nowhere is there mention of the solar cycle impacts. Since the sun is now quieter than it was in solar cycle 5 (1700s) no one knows what is going to happen.
Neither is the SOI changing: confront this:
http://www.agu.org/pubs/crossref/2008/2008GL034499.shtml
Perhaps the answer is simpler than we imagine, such as a lack of biodiversity. This is human induced and can be easily corrected.
http://www.sciencewa.net.au/topics/agriculture/174-News/3236-land-clearing-to-blame-for-drought
Even if you believe you can find the proper signal that explains all the rainfall patterns over sth Australian and it turns out to be caused by AGW, you still have the numero uno problem to confront.
You can’t do anything about it unless you can literally change the opinions and actions of the developing world.
This article by Terry McCrann shows all the relevant info you could ever require to prove what a complete waste of time the entire scam is and should be required reading by delusional people who want/need to “tackle” CC.
http://www.heraldsun.com.au/business/terry-mccranns-column/hsbc-research-reveals-chinas-coal-rush/story-e6frfig6-1225971769042
Cohenite – I just have to smile. I warned you. Staying outside the climate community and not getting peer review – formal or informal, focusing purely on statistics to the exclusion of mechanisms, leads you to http://landshape.org/enm/files/2011/01/walkerarticle.pdf …. well …. Oh dear – another goof.
I have to smile. And you’ll just have to wait to Part III to find out why you’re ninnies. We’ll just add “that” paper to McLean et al. No wonder the mainstream just politely smile at you guys. It’s a pity really – as if minds like Stockwell engaged he might make a useful contribution.
El Gordo – It’s not the land clearing – the rain systems aren’t turning up as they need to from off-shore. Land clearing might “add” something.
Neville – the politics or solution to AGW have nothing to do with the climate mechanisms – the physics apologises and can’t help it. Even if AGW is unsolvable – farmers and water resource managers still need to know mechanisms and odds. Do you think AGW and climate variability is simply for carbon taxing types? Not very broad minded. And I thought the climate mechanisms would have fascinated you and you at least would have declared it all natural variability. Do we detect a thread of doubt from you?
As they used to say to religious types – don’t pray for rain – pray for warm water anomalies in the right place. God would prefer it if you got closer to the mechanism.
RMD – do try to read the post again and especially – http://www.nature.com/ngeo/journal/v3/n4/full/ngeo761.html#a1 van Ommen
“The movement of air in the Walker circulation affects the loops on either side. Under “normal” circumstances, the weather behaves as expected. But every few years, the winters become unusually warm or unusually cold, or the frequency of hurricanes increases or decreases, and the pattern sets in for an indeterminate period.
The behavior of the Walker cell is the key to the riddle, and leads to an understanding of the El Niño (more accurately, ENSO or El Niño – Southern Oscillation) phenomenon.”
I think your Uncle Gilbert would think you are trying to cut heads off the uncertainty monster.
Even Gavin has become a sceptic these days.
Luke,
You need more faith in natural feedbacks.
Why do you think our overpopulated world is being loaded with gays and lesbians? Green voters? Muslims? Public servants? Bacteria-resistant diseases?
Gaia has it all under control.
spangled – well strangely your burgeoning Asian populace is generating that brown haze cloud which is probably influencing an INCREASE in NW WA rainfall…. Muslims and Hindus I guess.
Google Rotstayn
Poor Cohenite. bad call on the SOI ….
WA traditionally produces between 30 and 40% of Australia’s wheat crop and last year produced about 8.2 million tonnes of a 21.7 mt crop which is around average.
This year is down because of the drought in the west but a year ago you could have made a similar claim for SE Australia.
Just don’t lose sight of Dorothea’s original words.
Looking ahead it’s wet, but BoM got it wrong last time so I’ll wait and see.
http://www.bom.gov.au/climate/ahead/rain.wa.shtml
Before you get too excited Luke you’ll see I’ve used the word scam above, so no I don’t believe in your new religion.
You’d have to get me to believe that this present climate is somehow unprecedented or unusual compared to the last 11,400 years of the holocene.
It’s not hot enough to grow trees up to the arctic coastline as happened for thousands of years before it cooled again by 3,000 bp.
We know that parts of the Arctic were ice free for thousands of years and much warmer than the present day.
We know that the Antarctic peninsula melted a number of times over the holocene.
We are told that a mega drought held fast for hundreds of years over western Nth America around the period 1,000ad to 1300ad.
These are just a few of the findings of peer reviewed studies that show extremes of climate that we thankfully don’t have to cope with at our present time.
Man couldn’t have caused these extreme climate changes so what caused them?
Obviously these extreme changes were caused by natural CC.
I could go on about the lack of a hot spot, little warming shown by the Argo studies since 2003, sea level rise going nowhere, IPO/PDO changes, IOD changes effecting SE Australia, southern Aust slowly drying over the last 5,000 years etc.
Sorry Luke but that increase of 0.01% of co2 in the atmosphere doesn’t look too convincing to me particularly when a positive feedback in the real atmosphere is suspect as well.
From the IOCI research document above.
‘In early winter in the south-west, atmospheric conditions have become more stable. There have been
fewer low pressure systems, more prevalent high pressure systems and, since 2000, the rainfall associated
with each system has decreased. The changes that have already being experienced in the south-west
are projected to continue at the same rate over the next century under increasing levels of atmospheric
greenhouse gases.’
No, this won’t stand the test of time. Once the negative IOD gets back into stride the people of south-west Oz will experience ‘good seasons’ again.
The vagaries of the system will soon become clearer, once they give the flick to greenhouse gas forcing in the models.
Everyone look at this http://joannenova.com.au/2011/02/questions-real-journalists-ought-to-be-asking-about-yasi/#more-13123
Listen to wise people and you may learn something, listen to idiots and you may know less
Keep Strong
cementafriend (cementing friendship?)
If you look at UNISYS there is a cold patch in the Coral Sea and the La Nina cool waters are drifting south into the cyclone spawning ground.
http://weather.unisys.com/surface/sst_anom.gif
It will be interesting to see if this anomaly diminishes cyclone activity on the Queensland coast.
Well Neville – even if you find nothing of AGW merit I hope you enjoy the unravelling of climate mechanisms.
As I said – don’t pray for rain – pray for a warm water anomaly in the right spot
Cementsy – Nova’s position is highly unintelligent. And misleading. I commented at Deltoid – http://scienceblogs.com/deltoid/2011/02/the_australians_war_on_science_60.php#comment-3218049 really her blog is simply hysterical
Luke, you fit in well with the Deltoidians, even Janet senses that you’re not a ‘concern troll’ after all.
‘Do the public understand all this? Is it in the Australian’s interest to explain?’
No and yes, but you are wasting your time preaching to the converted over there. Why don’t you join Gates at Watts and argue your case at every opportunity?
el, luke did a good job taking on the faux concern of the weirdos at Deltoid and pointing out that there are real, disastrous consequences to AGW ‘remedies’, unlike the imaginary consequences of AGW; in fact when luke goes to town he can even quell, or at least bemuse, even the most elitist of the AGW acolytes; for instance there was a thread at Taminos a couple of years ago when luke got going and absolutely paper-snowed them with masses of detail about the expanding drought conditions facing Australia under the yoke of AGW; unfortunately I have lost the link but I’m sure luke will oblige us.
His second part here is vintage, as I say with all sorts of modelling and copious detail but it still is just modelling which has collapsed under its own unreality. He has had a shot at me about the SOI; I don’t know what he means; I have linked to the Nicholls paper which shows no alteration in SOI parameters; the Nicholls paper completely contradicts the earlier Power and Smith paper which said the SOI had shifted to a lower level consistent with never-ending droughts.
How is this my fault?
Luke you and I both know that we can’t do zip to change the climate to some improved condition by reducing our emissions by 20% or 1.4% less .28%= 1.12%, it just can’t happen.
My simple point is why not spend a much smaller ammount on research and hopefully new technology and as a by product we may just reduce our emissions as well.
I don’t believe it will change the climate at all but at least we won’t be flushing billions $ straight down the dunny and we might just get a new source of energy, who knows.
Well Cohers – you do have to keep up and you haven’t. And as I said there are consequences from hiding away from BoM and CSIRO and behaving like sneaky little 5th columnists. You may see but not observe.
And this is where you are very dopey – it’s not “all about modelling” – it’s about observations, pinch o’ stats, mechanisms, and some modelling.
Now I’ve just given you a grand tour of climate science in SW WA – be grateful. And probably at least parts 3, 4 and 5 to come.
Yes that Tamino post was when I was on my game.
You’re hopeless luke: “Now I’ve just given you a grand tour of climate science in SW WA – be grateful”
For real tour try this:
http://kenskingdom.wordpress.com/2010/06/18/the-australian-temperature-record-part-4-south-australia/
” There landmark paper on a new index, the southwest Australian circulation, begins:”
Fail…not need to any further. Obviously not Peer Review standard.
Yeah. That’s all very interesting, but the new alarmism is that warm air holds more moisture, giving the required water vapor feedbacks in order to make the world scary hot, instead of the piddling little lukewarm, of a non feedback, co2 stand alone warming. Therefore global warming causes higher precipitation, not lower.
Al Gore said it himself.
http://tomnelson.blogspot.com/2011/02/nyt-update-gore-blames-more-water-vapor.html
Surprised you didn’t get the memo.
Please try to keep up in future.
Luke, your problem is you actually believe this crap, and seek out facts to support your case. This will invariably cause you to come to loggerheads with the climate change orthodoxy, who know it’s a scam to separate the peeps from their hard earned money.
Using facts to support AGW science is like pinning the tail on a jello mold donkey.
My advise is you hold on to part three until after the seasons change, so that when the climate apocrypha swings back from apogee, you’ll be in a better position to match their nebulous, one size fits all, position of the moment.
Yawn – as the guys wilt under the reality of real science as opposed to sceptic waffle. So a great explanation of Antarctic climate change and sub-tropics change and they’re suddenly content free. Having a little tanty ranty is much easier isn”t it. commie plot, world govt, Al Gore zzzzzzzz
Was there some kind of sea change in 1964?
http://www.nerc-bas.ac.uk/public/icd/gjma/newsam.win.pdf
According to Feng et al.
‘The reported inverse relationship between the SAM and SWR is entirely dependent on the inclusion of data for an extreme year—1964. In this year, an extreme negative value of the SAM is associated with the wettest winter in SWWA during the period 1948–2007.
This implies that the SAM shows a non-significant relationship with SWR.’
and relationships with regional pressure and sea surface tem-
perature. Int. J. Climatol., 20, 1113–1129.
Cai, W., and I. G. Watterson, 2002: Modes of interannual vari-
ability of the Southern Hemisphere circulation simulated by
the CSIRO climate model. J. Climate, 15, 1159–1174.
——, 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.
England, M. H., C. C. Ummenhofer, and A. Santoso, 2006: In-
terannual rainfall extremes over southwest Western Australia
linked to Indian Ocean variability. J. Climate, 19, 1948–1969.
Feng, J., J. Li, and Y. Li, 2010: A monsoon-like southwest Aus-
According to Feng et al.
‘The reported inverse relationship between the SAM and SWR is entirely dependent on the inclusion of data for an extreme year—1964. In this year, an extreme negative value of the SAM is associated with the wettest winter in SWWA during the period 1948–2007.
This implies that the SAM shows a non-significant relationship with SWR.’
Ooops…sorry about the attached which I failed to edit.
http://www.co2science.org/education/truthalerts/v14/TruthAboutClimateChangeOpenLetter.pdf
Does wilting under the reality of so called real science included this type of reaction.
Lets face one would never go broke underestimating the biases of faux scientists.
Its all a waste of time anyway if the rumour is true, namely that the Great Serial Exaggerator Flannery has been appointed as Chair of the Climate Commission.
God help Australia….please.
Malcolm: “Fail…not need to any further. Obviously not Peer Review standard”. Say, what God of wisdom?
Cohenite; has anyone actually read your paper and written a proper review? The problem with all index seeking excursions is the shoddy data at the far end of a series and the noise in between. How have you improved the research?
Yes boys – isn’t that interesting. So looks like an AGW effect on Antarctica itself but some revision not implicating SAM itself in the SW WA rainfall decline. So findings overturned. The way science works. So it’s Now SWAC to the max.
yes Mal – apologise for the there/their – was left over from a “there is” sentence.
What paper gav? This one:
http://theresilientearth.com/?q=content/stat-model-predicts-flat-temperatures-through-2050
http://www.abc.net.au/news/stories/2011/02/10/3135059.htm
My god …its true.
The opportunists and “science” extremists are going to send us backwards into the dark age.
Is there no end to this stupidity…are there ANY people in Canberra with ANY functioning brain cells at all.
Cant they do anything with integrity and competence.
The silliness of the cohenite stance is again illustrated by an article in today’s Canberra Times about a fresh review of old news relating to our nearby Lake George.
As lakes go it’s been a bit of a mystery because it completely disappears from time to time. Now this is seen as a good indicator of modern climate variations ie no models needed nor analyse of sketchy rainfall stats from a mere 200 years.
Yes; its quite black and white when the thing is full or empty! And yes; your average Joe has been called in to again witness its history by helping to find and collate that old news.
Anyone-re that cohenite link above; at what point and how do we tap the slipstream around the moving train engine to find it’s average waste heat?
Gavin, could you give me a link to that Lake George data?
Here’s the article from the Canberra Times.
http://www.canberratimes.com.au/news/local/news/general/papers-chart-climates-georgian-era/2072081.aspx
Good old gav and Lake George; I’ll tell you the real mystery and its not the fluctuating water in Lake George; the real mystery is how supposedly sensible people gave Australian taxpayer’s money to subsidise Capital Wind Farm around Lake George; here is its output:
http://windfarmperformance.info/?date=2010-05-15
Explain that gav.
Weak as , cohenite but it’s about what I’d expect from a little guy who can’t find a fart in a smoke screen.Go play trains hey.
El gordo; thanks for that CT link caues it wasn’t up when I posted. Perhaps you can have a go at my slipstream Q since coers has ducked off.
That wind farm link off beat as it is here proves nothing re our dire need for climate info and any day can be just that
http://windfarmperformance.info/?date=2011-02-03
Try again
Last year Luke mentioned a warm spot in the southern Pacific Ocean and I became intrigued. Is it a coincidence that interglacial global warming begins in the southern hemisphere?
In my travels I came across a fairly old paper by Fischer et al. who were collecting ice cores in Antarctica. They went back 250,000 years and discovered that the last three deglaciation commenced with a warming signal and then CO2 increases 400 to 600 years later.
Here’s the abstract:
http://www.sciencemag.org/content/283/5408/1712.abstract
When an abrupt cooling commences the CO2 concentrations remain high for up to 6000 years before plummeting.
el; most observers realize the lead lag scenario first discovered in ice cores is played on a different stage to the AGW game as we have changed the surface, the rules and umpires
Note the rhetoric used n this formation training update
http://www.physorg.com/news/2011-02-ice-cores-yield-rich-history.html
Don’t take your eye off the CO2 ball, gavin. AGW rhetoric only goes back 30 years and let me assure you that piddling trace gas has no case to answer.
The ‘bipolar see-saw’ is dynamic and the appeal of Milankovitch type hypotheses doesn’t completely explain what is going on here.
http://www.sciencemag.org/content/291/5501/109.abstract
The sun still seems to be be a major player and there are random events like volcanos to muddy the waters, but I’m thinking it’s some kind of internal self-regulating process which brings about climate change.
And don’t talk to me of Gaia.
Even if the trend extracted is granted as being from CO2, what is the impact on policy and people’s lives? Clearly modest rain events will still cause flooding in flood plains.
It seems that instead, the trend you describe- which is frankly pretty subtle- was used to help tip the policy balance against taking prudent measures to manage the reality of Australian weather.
With Luke discussing light bulbs elsewhere, this abstract may be of interest.
http://www.agu.org/pubs/crossref/2011/2010GL045698.shtml
There is no tipping point in the Arctic.
eg,
Ya can’t believe that! That comes from a GCM.
But if they’re as good as watson…..
http://wattsupwiththat.com/2011/02/10/worth-watching-watson/
BTW, this is what it would take for Aust to meet the least ambitious emissions targets:
http://blogs.news.com.au/heraldsun/andrewbolt/index.php/heraldsun/comments/so_many_nuclear_power_stations_will_gillard_build_by_2020/
To paraphrase Arblaster et al. above ‘Contributions of external forcings to SAM’.
By the end of this century the build-up of greenhouse gases will magnify radiative forcing, producing ‘large warming over most of the Southern Hemisphere.’
The recent cooling in Antarctica has been put down to SAM, but ‘the surface warming amplifies as the radiative forcing increases, implying that the recent local cooling over the Antarctic will reverse at some point in the future.’
This is their idea of a tipping point in the SH, a human induced ‘meltwater pulse’ (MWP) which will severely impact West Antarctica and produce rapid sea level rise.
If Antarctica remains unusually cool for another decade, then the MSM will assume GHGs are having no effect.
Scientists are focussed on ozone depletion in the stratosphere and its part in Antarctic ice extent. Turner et al. in a 2009 paper claim the buildup is significant.
‘Based on a new analysis of passive microwave satellite data, we demonstrate that the annual mean extent of Antarctic sea ice has increased at a statistically significant rate of 0.97% dec-1 since the late 1970s.’
This dove-tails perfectly with the great climate shift of 1976 and the changeover to a warm IPO. It appears to be natural variability producing the decline in SWWA rainfall, but we need to analyze precipitation rates during the 1930s to prove the point.
From the late 1970s the Leeuwin Current has become weaker and the SSTs in the Leeuwin Current have risen by about 0.6 degrees C since the 1960s.
This will be worth watching, it doesn’t quite add up.
The Antarctic Circumpolar Current has also been edging south at 10 kilometers per year, which is surely indicative of natural variability.
el gordo, do you have a reference of any sort for your comment about the Leeuwin Current? I don’t mind if it’s anecdotal from the locals because even that might give me a hint of where to look for proper monitoring.
Feng et al.
http://www.oceanclimatechange.org.au/content/images/uploads/Leeuwin_Current.pdf
The authors are pro-AGW, so I’m a little sceptical. The Rottnest station is the apparent source for the 0.6 C increase since the 1950s, but not sure if that data has been adjusted.
Still looking for raw sst data, so far without success. Maybe Luke Desk has something up his sleeve.
It’s possible that 40 years of increased El Nino (because of a positive IPO) may have bumped up the temperatures in the austral winter.
http://www.publish.csiro.au/paper/MF08199.htm
Assuming increased SST is natural and nought to do with GHGs, a recent paper by Brown et al. says warmer waters are good news for Australian fish stocks.
http://www.worldclimatereport.com/index.php/2011/02/10/australian-fisheries-to-flourish/
Still in the marine world, this time in Queensland, analyzing climate through corals.
Precipitation in Queensland from the late 17th century and 18th century was ‘probably a bit above the long term average and was reasonably variable’, while 1785 to 1884 was ‘drier and less variable’. The past 100 years have been wetter and more variable.
Ignore the global warming spin and any suggestion that we can expect extreme events in the future.
http://uk.news.yahoo.com/22/20110210/tsc-uk-climate-corals-011ccfa.html
Here is more evidence to support the idea that 19th century Queensland was drier and less variable than the long term average.
http://www.nature.com/nature/journal/v421/n6924/fig_tab/nature01361_F2.html
Searching for Luke’s AGW signal is like looking for a needle in a haystack, because ‘natural climate variability is large’. There are regular oscillations at work (cycles within cycles) that seem to stand outside volcanic eruptions or solar behavior.
Which suggests the internal dynamics of the system (ocean, atmosphere and cryosphere) is still beyond our understanding.
The lack of ‘good seasons’ in SWWA has nothing to do with AGW or SAM and we should focus our attention on the behavior of the Indian Ocean monsoon.
Yes yes yes El Gordo – we’ll just ignore the Law Dome results. hmmmm
Speaking of monsoons too http://www.sciencemag.org/content/322/5903/940.abstract oh dear
Reading the Norman Treloar paper ‘Luni-solar tidal influences on climate variability’.
‘The Earth’s rotational acceleration has been used to define different atmospheric circulation regimes (Lamb, 1972), and shows a 60 year cycle with maxima near 1860 and 1920 (Lambeck, 1980).’
The 60 and 180 year cycles are very interesting and Treloar gives us a starting point to unravel the mystery of a dry south-west.
In the meantime the IOD remains the focal point.
http://journals.ametsoc.org/doi/full/10.1175/JCLI3700.1
The Zhang abstract above was on the right track, until the gravy train pulled up alongside.
‘The sign of the correlation between the AM and temperature switches around 1960, suggesting that anthropogenic forcing superseded natural forcing as the major driver of AM changes in the late 20th century.’
By comparison this abstract by Agnihotri et al. blames the sun for everything.
‘Solar influence on the intensity of the Indian monsoon is demonstrated using a sediment core from the eastern Arabian Sea dating back to 1200 yr, through pattern matching as well as spectral analysis of proxy records of monsoon and solar activity.
‘The intensity of the Indian monsoon is found to have decreased during periods of solar minima during the last millennium. Periodicities of 200±20, 105±15 and 60±10 yr are observed in the proxy records coinciding with those known for solar cycles.
‘The 60-yr periodicity observed in the instrumental rainfall data appears to be of solar origin and supports the hypothesis of solar control on the Indian monsoon on a multi-decadal time scale. Evidence for the presence of a coupled atmospheric forcing for the Indian and East African monsoons on a centennial time scale is also seen.’
The cycles are clearly solar related.
What you need to know el Gordo is that Treloar has other work unpublished. There’s a very big greenhouse signal and he definitely believes in AGW. BTW he had heaps of trouble getting published on lunar-tidal stuff but never yelled conspiracy.
It would have done Treloar no good to yell conspiracy, the lunar-tidal stuff sounds like astrology. He merely adapted to the new AGW religion, which has wealth and power beyond measure.
The Shindell and Schmidt abstract above says: ‘It has been suggested that both Antarctic ozone depletion and greenhouse gases have contributed to these trends.’
Alright, I might pay that. Ozone depletion is natural and the increase in CO2 over recent times may also be predominantly of natural origin. Tom Quirk is not convinced that fossil fuel is the bogeyman you think it is.
http://icecap.us/images/uploads/TomQuirkSourcesandSinksofCO2_FINAL.pdf
This sentence from the Meneghini et al. (2006) abstract.
‘Overall, our results suggest that changes in the SAM may be partly responsible for the current decline in winter rainfall in southern South Australia, Victoria, and Tasmania, but not the long-term decline in southwest Western Australian winter rainfall.’
Exactly what I was thinking.