I liked this part:
According to the study an important issue remains as to why the poleward expansion is largest in autumn, and there is still uncertainty about the role of external forcings – such as greenhouse gases – as climate models underestimate the southward expansion of the Hadley cell edge.
From CSIRO Australia
Southern Hemisphere becoming drier
A decline in April-May rainfall over south-east Australia is associated with a southward expansion of the subtropical dry-zone according to research published today in Scientific Reports, a primary research journal from the publishers of Nature.
CSIRO scientists Wenju Cai, Tim Cowan and Marcus Thatcher explored why autumn rainfall has been in decline across south-eastern Australia since the 1970s, a period that included the devastating Millennium drought from 1997-2009.
Previous research into what has been driving the decline in autumn rainfall across regions like southern Australia has pointed the finger at a southward shift in the storm tracks and weather systems during the late 20th century. However, the extent to which these regional rainfall reductions are attributable to the poleward expansion of the subtropical dry-zone has not been clarified before now.
Mr Cowan said rainfall patterns in the subtropics are known to be influenced by the Hadley cell, the large-scale atmospheric circulation that transports heat from the tropics to the sub-tropics.
“There has been a southward expansion of the edge of the Hadley cell – also called subtropical dry-zone – over the past 30 years, with the strongest expansion occurring in mid-late autumn, or April to May, ranging from 200 to 400 kilometres,” Mr Cowan said. The CSIRO researchers found that the autumn southward expansion of the subtropical dry-zone is greatest over south-eastern Australia, and to a lesser extent, over the Southern Ocean to the south of Africa.
“The Hadley cell is comprised of a number of individual branches, so the impact of a southward shift of the subtropical dry-zone on rainfall is not the same across the different semi-arid regions of the Southern Hemisphere,” says CSIRO’s Dr Wenju Cai.
The researchers tested the hypothesis that the dry-zone expansion would give rise to a southward shift in the average rainfall during April and May, and questioned how rainfall across semi-arid regions, including southern-coastal Chile and southern Africa, would be affected.
“During April and May, when the dry-zone expansion is strong, rainfall over south-eastern Africa, south-eastern Australia and southern-coastal Chile is higher than over regions immediately to their north,” Dr Cai said.
Using high-quality observations and an atmospheric model the CSIRO team found that for south-eastern Australia, up to 85% of recent rainfall reduction can be accounted for by replacing south-eastern Australia rainfall with rainfall 400km to the north. Such a southward shift of rainfall can explain only a small portion of the southern Africa rainfall trend, but none of the autumn drying observed over southern Chile.
“For south-east Australia, autumn is an important wetting season,” Dr Cai explained. “Good autumn rainfall wets the soil and effectively allows for vital runoff from follow-on winter and spring rain to flow into catchments.”
According to the study an important issue remains as to why the poleward expansion is largest in autumn, and there is still uncertainty about the role of external forcings – such as greenhouse gases – as climate models underestimate the southward expansion of the Hadley cell edge.
This research was conducted through CSIRO’s Water for a Healthy Country Flagship, and was funded by the Goyder Institute for Water Research and the Australian Climate Change Science Programme. Wenju Cai, Tim Cowan and Marcus Thatcher are from CSIRO’s Marine and Atmospheric Research division.
UPDATE:
Some commenters can’t look beyond the title and see the bigger picture, so here’s an update just for them. Note that the study deals with the Hadley cell, which is NOT regional, but hemispherical. They looked not only at Australia, but also rainfall in southern-coastal Chile and southern Africa.
This is where I was coming from, which I thought would be obvious to anyone who’s been following the positive water vapor feedback issue for any length of time.
http://www.gfdl.noaa.gov/bibliography/related_files/hall0001.pdf
===============
Abstract. Using two versions of the GFDL coupled ocean-atmosphere model, one where
water vapor anomalies are allowed to affect the longwave radiation calculation and one
where they are not, we examine the role of water vapor feedback in internal precipitation
variability and greenhouse-gas-forced intensification of the hydrologic cycle. Without
external forcing, the experiment with water vapor feedback produces 44% more annualmean, global-mean precipitation variability than the one without.
We diagnose the reason for this difference: In both experiments, global-mean surface temperature anomalies are associated with water vapor anomalies. However, when water vapor interacts with longwave radiation, the temperature anomalies are associated with larger anomalies in surface downward longwave radiation. This increases the temperature anomaly damping through latent heat flux, creating an evaporation anomaly.
The evaporation anomaly, in turn, leads to an anomaly of nearly the same magnitude in precipitation. In the experiment without water vapor feedback, this mechanism is absent. While the interaction between longwave and water vapor has a large impact on the global hydrologic cycle internal variations, its effect decreases as spatial scales decrease, so water vapor feedback has only a very small impact on grid-scale hydrologic variability. Water vapor feedback also affects the hydrologic cycle intensification when greenhouse gas concentrations increase. By the 5th century of global warming experiments where CO2 is increased and then fixed at its doubled value, the global-mean precipitation increase is nearly an order of magnitude larger when water vapor feedback is present.
The cause of this difference is similar to the cause of the difference in internal precipitation variability: When water vapor feedback is present, the increase in water vapor associated with a warmer climate enhances downward longwave radiation. To maintain surface heat balance, evaporation increases, leading to a similar increase in precipitation. This effect is absent in the experiment without water vapor feedback. The large impact of water vapor feedback on hydrologic cycle intensification does not weaken as spatial scales decrease, unlike the internal variability case. Accurate representations of water vapor feedback are therefore necessary to simulate global-scale hydrologic variability and intensification of the hydrologic cycle in global warming.
=================
So if positive water vapor feedback were occurring, based on this idea, we’d see an “intensification of the hydrologic cycle”, i.e. more rainfall, runoff, and evaporation. That would apply to the southern hemisphere continents too.
And the researchers by their own admission can’t even fit GHG feedbacks into the Hadley cell migration equation successfully. It is just more evidence of uncertainty in the “settled science” of AGW.
to D Böehm,
You can see my full resume including over 100 research papers published in the top journals over a period of 40 years along with my educational background prior to that on my website, ericgrimsrud.com. My experiences in atmosphere sciences go back to 1974 when I made rhe first quanitative determinations of the two most abundant chlorine containing compounds in the background atmosphere, CFC-12 and methyl chloride (See Grimsrud and Rasmussen, Atmos. Sci. 1975). This work was done the same year, 1974, as the theory of stratospheric ozone depletion was proposed by Rowland and Malino. For the following 29 years at Montana state, my research group continued to develop new methods of trace analysis, often resulting in first detections of myriad other trace components of the atmosphere (again see resume) including numerous trace level greenhouse gases.
Now concerning the scientific record of Mr. Richards Courtney, where is the evidence of that? In the previous thread he refers to above, I repeated asked him the same question and received no response to those requests. I asked because he seemed to me to be nothing more than a BSer whose ignorance of the basics became apparent when discussing even the very basic simple aspects of the greenhouse effect. (go look back at the long thread concerning Senator Inhofe.
So you suppose that he is simply to shy to provide the public such a resume – as all other real scientists do when holding forth on the important issue of climate change. What Mr. RC is very good at is undermining the input and credibility of real scientists who comment on WUWT and then hiding behind claims of political correctness when any of them counter attack.
I’ll look forward to the results of your own search for Mr. Richards Courtney’s credentials and remember that you suggested that “Mr Courtney is a published, peer reviewed author”. Personal letters to His Majestry’s Government or comments on open web sites, for exampe, will not do.
ericgrimsrud,
Considering that most everything you believe has been falsified, your ad-hom insistence that anyone with a scientific point of view must be a member of the AGW priesthood is ridiculous.
Mr Courtney is a peer reviewed climate author, and also a peer reviewer. Your false statement is that “he has no demonstratable background in science, in general, and certainly no record of contribution to climate science” is provably wrong.
Obviously you are wrong. It took only a minute to find that reference to Mr Courtney’s peer reviewed publication. There may be more, but one example falsifies your derogatory statement.
It is not my ox being gored, so I am not concerned about your ignorance. But you do owe Mr Courtney an apology for your baseless ad hominem attack. A stand-up guy would admit it when he is shown to be wrong. We will now see if you possess any character, or if you instead continue to argue the man instead of the science.
Bill Illis October 5, 2012 at 6:13 am
provides a link to an interesting comparison of the AR5 total precipitable water vapour forecast and hindcast to the observations. The modelers apparently make no attempt to match the historical record.
Changes to water vapour in the upper atmosphere above the clouds have a much greater effect on out-going radiation than changes in water vapour near the surface. There is so much water vapour near the surface that it absorbs most of the upward radiation from the surface except in the “window” region of the spectrum where water vapour has very little effect. Heat transported by convection and evapo-transpiration to the upper atmosphere can escape as radiation only where the amount of water vapour is small. Both radiosonde and satellite measurements show declining water vapour in the upper atmosphere, just where it has the greatest effect on climate. Simulations show an absolute change of water vapour in an atmospheric layer from the 300 mb to the 400 mb level has 30 times the effect on out-going longwave radiation as the same change near the surface. So the total water vapour column trends are a minor part of the story. Changes in the upper atmosphere is much more important.
Here is a graph water vapour specific humidity versus CO2 content in the tropics upper atmosphere.
http://www.friendsofscience.org/assets/documents/FOS%20Essay/SH400TropicsVsCO2.jpg
The water vapour content shows a downward trend with R2 of 0.71. CO2 replaces water vapour as a greenhouse gas in the upper atmosphere.
The graph of relative humidity by layer versus time from the NOAA data is
http://www.friendsofscience.org/assets/documents/FOS%20Essay/GlobalRelativeHumidity300_700mb.jpg
The NASA water vapour project (NVAP) uses multiple satellite sensors to create a standard climate dataset to measure long-term variability of global water vapour. The satellite based water vapour content in the 300 to 500 mbar pressure range (about 6 to 9 km altitude) is shown here:
http://www.friendsofscience.org/assets/documents/FOS%20Essay/NVAP_500-300_WV.jpg
I requested the data by atmosphere layer by email. Janice L. Bytheway of the NVAP-M Team, Colorado State University replied 24/07/2012 12:18 PM,
“As for your interest in the trends at the upper versus lower levels of the atmosphere, we unfortunately don’t have the staff or funding to provide subsets of the data at this time. This feature should be provided in about 6 months after the NASA Langley ASDC has taken stewardship of the data.”
The total column amount is the sum of the layers, but they can’t provide the data by layer. Very strange!
ericgrimsrud, no wonder you keep changing the topic to CFCs. Yet even in your area of expertise you are prone to spouting nonsense like “CFC’s were completely destroying ALL stratospheric ozone over the continent of Antarctica every Springtime.” see http://wattsupwiththat.com/2012/09/28/the-president-decides-to-stick-with-climatism/#comment-1094768
There are at least two problems with your thinking and approach. First you are prone to stating exaggerations. You later correct and said “near zero”. But you never acknowledged the fact that natural processes could also bring stratospheric ozone down to near zero and CFCs simply made that natural occurrence worse. Your inexactitude is distressing for someone who supposedly taught science to students who probably don’t know any better and end up poorly trained.
Second, you seem to be equating your knowledge of CFCs with an understanding of greenhouse gas warming. But above you demonstrate ignorance of weather when you state (at the beginning of this thread): “But the amount of water in (evaporation) still will equal the amount of water out (condensation. Thus, in very general terms, on the surface of the Earth dry places will tend to get drier and wet places will tend to get wetter”
It is possible that wet places will get wetter due to increased water cycle. It is even possible but less likely that drier places will get drier due to weather pattern changes. But the latter is *not* because of the balance of evaporation and condensation as you claim. The latter can only happen due to (speculated) changes in circulation such as enlargement of the Hadley cells.
In short your expertise in some atmospheric science field does not apply to the discussion in this thread and most threads on this site. It’s mildly amusing and a little sad that you think it does and keep posting your nonsense.
To D Böehm,
Very good!! You managed to find a publication with Sir Richards Courtney’s name on it. I guess he was too shy after all to produce evidence of his scientific background when repeatedly asked to do so.
Concerning who are “stand up guys”, however, you should read some of your friend’s mindless smears of me on this and the previous Inhofe treat and see for yourself if due respect was demonstrated by him. For example, read his “summary” of my contributions to science that he posted on this threat above and then look them up yourself at ericgrimsrud.com.
Since I suspect that your admonitions for showing proper respect at WUWT will go only one way in this case, I don’t expect to hear from you on that one. That is, it is OK for Sir Richard to post mindless smears but not OK for the recipent of those smears to respond in kind.
During my last 5 years of interacting with the public on the subject of AGW, my feces detector for sensing pseudo science has become increasingly expericenced and I reserve the right to hold my own opinions of the pseudo scientist thereby dedected that are endeavoring to make the lives of my greadchildren even more difficult than we already know they will be. Let Sir RC have his 30 pieces of gold for services rendered to the fossil fuel industries, but apologize to him? You much be kidding !!
ericgrimsrud:
Among other falsehoods about me which ytou have asserted in this thread at October 5, 2012 at 8:57 am you write
Actually, I point out the nonsense of people – including you – who pretend to present knowledge which they do not have, and I welcome their response because it encourages them to reveal the nature of their pretensions.
I get snipped on WUWT because of my lack of “political correctness”.
You are trivial, but a NASA GISS ‘climate scientist’ such as Perlw1tz is not. A currently ongoing example of my encouraging him to display his ‘true colours’ can be read in the WUWT thread at
http://wattsupwiththat.com/2012/09/28/dr-leif-svalgaard-on-the-new-scientist-solar-max-story/
(In checking this link I notice that he has still not learned the First Rule Of Holes so I shall return to that thread).
I don’t need to justify my posts because people can judge my contributions for themselves, as they can judge your contributions.
Richard
ericgrimsrud, even though Richard Courtney warned me, I bought your book at Amazon ($3.99) so I could see for myself what was in it. Already you mislead : “…detrimental effects of compounds which have extremely long lifetimes (such as the CFC’s and carbon dioxide) will persist for several centuries even after their man-caused emissions are entirely stopped.”
Some effects may persist but the compounds do not. As you well know, CFCs break down immediately in the upper atmosphere upon exposure to UV. The chlorine remains, so perhaps you meant to say the chlorine has a long lifetime. The CFCs do not. As for CO2, it will be absorbed into the ocean at the same rate that it is today and therefore drop half way back to preindustrial in less than 40 years. The “lifetime” of CO2 in the atmosphere would be “extremely” long were it not for the ocean absorbing lots of it. Your answer in the other thread was wrong, namely that if we stopped emitting the ocean would start to off gas. No, it would not, it would keep absorbing the excess.
D Boehm,
There you have one answer straight from a pseudo scientistist’s mouth. Sir RC said, “I don’t need to justify my posts because people can judge my contributions for themselves”.
I hope this statement also applies to me with the additional understanding that I am alway willing and pleased to explore any details of the science that I have related with any interested party. In my first comment at the very top of this thread I did just that and no more – until Sir Richardscourtney showed up, starting with a personal insult to me. That man will not stick to scinence. When losing on the science front, he switches to personal insults. When treated in kind by the person he insults, he then claims violations of political correctness. Yes to me, he does seem to be both a charlatan and a wimp who does a great disservice to public discussions of AGW. But as the man himself says, “people can judge my contributions for themselves”. My own goal at ericgrimsrud.com is to help the public learn the basic science to that they can do just that.
ericgrimsrud,
You stated categorically that Richard Courtney “has no demonstratable background in science, in general, and certainly no record of contribution to climate science”.
I proved you are wrong. Mr Courtney has demonstrated a more learned science background than most. He is a peer reviewed climate author.
You owe Richard an apology. Instead, you exhibit the shabby and unprofessional qualities we have come to expect from the climate alarmist crowd. Despicable. Now readers can judge your lack of character for themselves.
Friends:
I wish to make clear that one of the lies by Eric Grimsrud is his repeated assertion that I have a knighthood. I do not.
Richard
More from the Grimsrud book: “First the relatively thin surface layers of the ocean mix exceedingly slowly with the colder depths beneath them, and many hundreds of years are required for the complete mixing to occur throughout the oceans. Therefore the surface layers become saturated relatively quickly and absorb much less CO2 than they would if the vertical mixing of the oceans was relatively fast.”
Your writing reminds me of certain politicians who like to pontificate to the camera with hand wavy cliches instead of concise and precise facts. Your adjective “exceedingly” is simply exaggeration. Your implication that complete mixing is required is wrong. Your statement about saturation is exceedingly simple-minded designed to appeal to ignorant individuals and keep them ignorant.
The fact is that the each year the oceans as a whole absorb at least 1/80th of the total CO2 that we have added to the atmosphere. That’s why if we stopped producing CO2 the levels in the atmosphere would drop half way back to preindustrial levels in less than 40 years. That means there is more than enough mixing between the surface layers and deep ocean to do that.
Either you know this fact and withheld it from your readers, or you didn’t know and you should not have written such a book from your poor state of knowledge.
to D Boehm,
Evidently you did not read Sir RC’s comments on this post, as I suggested you should – such as the one he posted at 1:07. With respect to acceptable decorum, you seem to have one set of standards for your friends and another for the “climate alarmist crowd”, as you can American scientists.
Instead, you return here to nitpick on the point that I had not noticed that SirRC had actually managed to get his name on one scientific paper in the past – and I did admit that I missed that detail – while am still waiting for his full resume to be made available to the public – as I and all other scientists have.
I don’t know who you are either of course, Mr. Boehm (resume please!), but from our breif interactions here, I am inclined to think that it is you who is “despicable”. And for good measure, let me add that I’ll bet my Dad is stronger than your Dad. So there!! And if you call me despicable again, I’ll look into the rumors concerning the footware favored by your grandmother !!
(Note to others: toying with the self-righteous is so much fun!!)
Eric
With your extensive knowledge of the Ozone Layer perhaps you can answer a question that has defeated both Cambridge University and the Max Planck Institute.
‘How do we know the ozone hole has’nt always been there, prior to the ability of instruments to detect it in the 1950’s?’ Thank you
Tonyb
More ignorance from the Grimsrud book: ” In addition, during the first half of the twentieth century, a gradual increase in the solar intensity of about 0.1 percent was observed. While the change might have contributed to a small increase in temperature over that fifty-year period, it would have had no effect after 1950.”
Wrong in several ways. Solar intensity rose through 1950, but then stayed historically high fully into the 1980’s and only recently decreased drastically. More importantly solar radiation heats the ocean more than the atmosphere and (along with the warming from increased CO2) is lagged in reaching the atmosphere. So the atmospheric warming would clearly not stop in 1950 as you state. My conclusion is the same as Richard Courtney’s, you cribbed this information from SkepSci or a related site but you do not understand it. At the very least you should have read through the commentary below the “myth” articles presented there because often people will point out the flaws.
eric1skeptic:
I write to provide you with a warning.
You are fast approaching the point where Grimsrud proclaims to the world that you are “feces” in the pay of “the fossil fuel industry”.
Richard
[Snip. Do not refer to scientific skeptics as “deniers” here. You have been warned several times. This is strike two. — mod.]
Eric1sceptic,
I just read Sir RC’s last note to you. Please know that I have no reason or intention to call you any such names. I reserve such names for those who have clearly shown they deserve them. You are not in Sir RC’s “class” so to speak. That is, one who pretends to be someone he is not and uses that pretense to fool the lay public. We used to call such people “snake oil salesmen” but the coarser term he claims I have assigned to him will do just a well.
The most obvious feature that this model captures qualitatively is the subtropical dry zones. Air parcels in these driest areas have either been carried down and warmed due to compression by the mean subtropical subsidence after losing most of their water in upward motion near the equator — or they have traveled down the midlatitude isentropic surfaces after having condensed most of their water during an earlier poleward and upward excursion. (The point of this paper was to think about how to quantify the relative importance of these two classes of trajectories.) Differences with the comprehensive models on the left are due in part to the absence of realistic boundary layer mixing spreading the evaporated water upwards, the absence of a seasonal cycle and monsoons that move subtropical dry zones and wash out the minima in the annual mean figure shown on the left, and the distortion of the vertical structure of the outflow from the tropical rising motion. (In the dry model, this outflow is spread over a broad layer of the troposphere, whereas in more realistic models with moist convection this outflow is confined more sharply to a layer near 200mb, causing the dry zone to be displaced upwards compared to the passive water model.) The bottom line is just that the atmospheric flow is what prevents this model atmosphere from becoming saturated everywhere – by wringing water out of parcels of rising/cooling air and then bringing these parcels back down so their relative humidity drops as they warm.
To climatereason,
Time here for a quick response. The reason we believe this is because the British measurement of the total ozone content in the column above their facitily on the Antarctic stared back in the 50s, I believe, when those measurement undoubtedly showed a close to natural ozone lever. Then in the 70’s and 80’s a distinct and severe decrease was noted to occur in the springtime. It was only then in about 1985 that high elevation aircraft began to fly though the region and determine where exactly the ozone loss was occurring. So it was the simpler ground level measurments from the 50’s to the present that suggest that the present condition constitutes a change from the past.
If you can’t find those ground level O3 measurements, let me know and I’ll point you to them later, as time allows.
eric1skeptic,
You comments concerning the measured intensity of the Sun at the Earth’s location will be easy to check out. Such measurement have been made since about 1850, as I recall. My statement was made by looking at those measurements and I have a graph in from of me that suggest what I said in my book. When I get back (need to run at the moment) I will retrieve another graph from source on the internet. Why don’t you do the same and refer me to your information souce. Then we will see if you are just nitpicking or talking about something important.
By the way, have you learned yet for yourself that the CFC molecules are not quicky restroyed. If not get a sample from your backyard and bring it into your neighborhood analysis store. They will tell you that your samle contains about 550 pptril CF2Cl2 – essentially the same as your backyard had twenty years ago just before the use of the compound was discontinued.
ericgrimsrud:
At October 5, 2012 at 1:44 pm you say
That is demonstrably untrue because if it were true then you would apply those names to yourself.
Richard
PS Please inform who Sir RC is. Would that be the founder of RealClimate?
eric1skeptic:
Although Eric Grimsrud knows nothing (and understands less than nothing) about climate science, he claims authority on CFCs and ozone depletion.
At October 5, 2012 at 2:17 pm he says to you
This is yet another case of Grimsrud either not knowing what he is talking about (which is very probable) or his being willfully misleading.
What happens to CFCs in the lower atmosphere is not relevant to your point that they are rapidly broken down in the stratosphere where the ozone layer exists. For example,the ‘Ozone Layer Protection Glossary’ of the US Environmental Protection Agency says at
http://www.epa.gov/ozone/defns.html at
If CFCs don’t reach the stratosphere then they cannot affect the ozone layer, and if they do reach the stratosphere they break down so their chlorine disrupts ozone. But Grimsrud says
(a) CFCs have not depleted at ground level since they were banned 20 years ago
but
(b) CFCs have destroyed the ozone layer over that time.
I await Grimsrud’s explanation of this magical ability of CFCs to be destroyed but continue to exist. On the basis of previous experience, I anticipate that his explanation will consist solely of foul-mouthed personal abuse at me for pointing out this inconsistency in his assertions.
Richard
Eric1sceptic:
I have found a graph showing the solar irradiance from 1850 to 2003. You can see it at colli239.fts.educ.msu.edu/2003/12/31/solar-activity-2003/ and is provided by the Met Office of Great Britian. My intent was mainly to show how solar intensity has been essentially constant along with the small (less than 1 watt/m2) 11-year cycle superimposed on that cycle. As to your suggestion that the additional increase of about 1 watt/m2 observed before 1950 has caused recent temperature increases, I’ll leave you to explain and provide support for that one.
SE Australia, are they including the red center and Great Victorian Desert, hmmm, DESERT!
Perth has been short of water, but had floods not so long ago, in Australia it is drier following flooding! Since when has it been different, you tell me, certainly it is normal for Australia, as most people live within 50 miles of the coast as from their on, depending on altitude precipitation decreases, like in America. The whole point of water in Australia is much more crucial as the cities have failed sometimes to store enough water and have to put on water restrictions or build an expensive salt water conversion plant. Out in the rural areas the same, but also they sometimes depend on only dams, river water or reticulated water for animals. Rainwater tanks for domestic use.
@joeldshore
“The story is that none of you supposed climate experts have any real clue of how it all works, nor does anybody for that matter, and this is just another example of the uncertainties of a science in its infancy.”
Something worth checking is if the lunar cycle of just under 19 years (precession of its orbit) has been considered in these models. There is a huge influence on the rainfall in the summer rainfall area of Southern Africa cause by the position of the moon. The leads to changing sea water temps and wind patterns that fluctuate is a clearly sinusodial cycle with the same period as the moon’s. For example, presently Southern Africa is at the wettest point of the cycle (2012) with extended summer rains, early spring rains and above average total precipitation.
In 2021 when they are at the dry end of the cycle, the moon having heaved its tilted orbit to the ‘other side’ as it were, there will be a drought ‘of unprecendented magnitude’ like that last unprecedented one in 1983, 1964, 1945 etc. While there are significant inconsistencies because ‘it is weather’ in the pattern, the cycle period is well known and is used to make long term weather predictions. This year is a good one to plant 60,000 maize seeds per hectare, not 30,000, for example in the good rains areas.
As the influence of this cycle is so large as to cause floods and droughts in a cycle (the winter rainfall area cycle is 10 years long) I can’t see it being over-run with the considerations in the paper above, above all, CO2’s influence. This ‘dry areas get drier and wet areas wetter’ looks like nonsense to me. There are good reasons to doubt the analysis and even if it were true, it is minor compared with the other known cycles and would be swamped to the point of undetectability, where it remains to this day.