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.
Climate models fail again!
(((Note to moderator, please discard my first comment and replace it with this one in which I have corrected a typo)).
I don’t get the title of this piece. As the atmosphere gets warmer, it holds more water. 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 (or collect more snow). Therefore, evidence of drier places does not justify the title of this piece – while it might fool the public that does not generally understand what I have said here.
Well, they are moving onto the right track at last but the process they describe has been starting to reverse since around 2000 in my opinion.
And they haven’t made any attempt to identify a natural process that might lead to such observations.
As it happens the shift they describe occurred at a time of high solar activity, generally positive AO and AAO, reducing global cloudiness and a cooling stratosphere.
The evidence is pretty convincing to me that upper atmosphere effects from solar variations are the true natural cause.
All those features are now going in the opposite direction with low solar activity, more negative AO and AAO, increasing global cloudiness and the stratosphere warming a little.
Another example of the challenges of climatology as a generalist discipline. I wrote about these issues with general circulation and specifically the Hadley Cell and the failures of the IPCC and other models as representations of reality years ago and again recently in two articles.
http://drtimball.com/2012/static-climate-models-in-a-virtually-unknown-dynamic-atmosphere/
http://drtimball.com/2012/errors-and-omissions-in-major-tropical-climate-mechanism-invalidate-ipcc-computer-models/
The real travesty is CSIRO and all government run weather and climate agencies are just catching up with what we knew thirty years ago. They are victims of the hijacking of real climatology by the pseudo- climate science of the World Meteorological Organization (WMO) sanctioned IPCC.
Get the government and the politics out of climatology and stop pretending that a specialist in one small part of a vastly complex interconnected system is a climate scientist and we might have a chance at better understanding. Something about not seeing the forest for the trees.
ericgrimsrud says:
October 4, 2012 at 8:34 am
Quite a lot of what you have said appears to have been lost in translation.
Like Eric I don’t see the connection between this article’s title and decreased humidity in the atmosphere (a negative feedback). I also don’t yet see a positive feedback. What is demonstrated is a change in regional rain fall pattern as a result of changing atmospheric circulation patterns, not atmospheric warming, chaning humidity levels, or increased storm activity. This probably means I need to find and read the original paper. I would also say that if the only thing that changes as a result of heating from increased CO2 is an expansion of the dry zones then we have a problem. That alone is bad enough to be a concern. I hate to invoke the old joke, but this analysis probably needs more grant money to discover the whole truth. The grain belts in both hemispheres are facing significant change if this is an accurate portrayal of the effects of CO2 warming. No feedbacks needed, apparently, as this appears to be a direct affect of CO2 warming warming alone.
“over the past 30 years”
Nicely coinciding with the warm cycle of the PDO.
(Yes, I know correlation is not causation. But as I said earlier, it gives you real good clues as to where to look.)
dp:
re your post at October 4, 2012 at 9:10 am.
Be not afraid. The “study” “demonstrated” nothing. It reported the output of a climate model. None of the climate models (except perhaps one) emulates the climate of the real Earth, so the “study” reports the result of playing a computer game.
As to the “effects of CO2 alone” if their are any then they are too small for them to be discernible.
You say you share the concerns of Eric Grimsrud. That alone should be sufficient to cause you to question your concerns.
I commend you to read the post of Tim Ball (i.e. a real climatologist) at October 4, 2012 at 8:45 am and to study the links he provides. Your fears will be assuaged to give you peace of mind.
Richard
ericgrimsrud says:
October 4, 2012 at 8:34 am
It seems quite consistent to me that as the dry zone moves further south so the amount of water vapour from above the warmer parts of the planet decreases, so more radiation can escape from the more strongly radiating parts of the earth. Hence there might be more water vapour overall but it acts less effectively at producing back radiation and so the overall positive feedback could well decrease.
So much for the title of posts on WUWT having anything whatsoever to do with the study that is discussed in the body of the post!
The article discussed didn’t have anything whatsoever to do with the water vapor feedback. It had to do with region variations in rainfall patterns that are observed and also predicted by climate models.
And, the water vapor feedback is already well-verified by observations as discussed in these two articles, for example:
http://www.sciencemag.org/content/323/5917/1020.summary
http://www.sciencemag.org/content/310/5749/841.abstract
REPLY: So much for you being able to look at the bigger picture of research. This is where I was coming from:
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 souther hemisphere continents too.
Congratulations to Connolley! /sarc
http://en.wikipedia.org/wiki/Wikipedia_talk:Articles_for_deletion/Marcel_Leroux
For those who do not see the connection, Eric, dp, the difference is WHERE the moisture is located relative to insolation, the energy input from the sun. If the greenhouse gases are not in the region where most of the energy is coming in, then they cannot trap it, it reflects and re-radiates.
Anthony Watts says:
There are many things going on, including shifting weather patterns, as described in this study. Surely you are aware of the fact that climate models predict greater drought in some regions? It is not just a uniform increase in precipitation everywhere!
As for intensification of the hydrologic cycle, that has in fact been seen. In fact, on this site some have claimed (in comments if not in the body of posts themselves) that one study by Wentz et al. that shows precipitation increasing MORE than models seem to have predicted (although there are in fact significant uncertainties and variability) is somehow evidence against AGW.
So, the question is which story do you guys want to go with: Is the hydrologic cycle intensifying more than expected or not as expected? And, does either way it turns out somehow lead to the same conclusion (i.e., that AGW is wrong or overstated)?
REPLY: 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. Reminds me of “knobs”. A few years ago they were predicting “permanent drought” for Australia, now its floods. Sure whatever. See the update above. See also Dr. Tim Ball’s comment. – Anthony
In August 2012, global water vapour levels were 0.13 mms/m2 or 0.6% above normal – ie. nothing.
Australia’s individual levels are very highly dependent on the ENSO pattern (in La Nina’s, there is more rain and more water vapour and there are lower values during El Ninos) versus some Hadley cell explanation. There is no long-term trend in the ENSO so one would expect no long-term trend in Australia rainfall either.
What they are saying WAS the case when the sun was active.Since 2005 the sun has become inactive and the Hadley -cell is most likely moving equatorward, as the Antarctic vortex expands N.
They are in the past, not the present.. It figures.
When the hydrological cycle intensifies it doesn’t produce more humidity globally if the cycle is faster.
A faster hydro cycle can be larger without increasing humidity because the water is in vapour form for a shorter time.
Nor need it be accompanied by a higher temperature globally as opposed to locally because a faster or larger hydro cycle ejects energy to space faster as a negative feedback.
My position is that solar cycles, ocean cycles AND GHGs all produce a negative system response via a change in the hydro cycle which manifests itself as a change in the global air circulation including the position, sizes and intensities of the subtropical high pressure cells.
However, the contribution from human CO2 emissions would be imperceptible compared to that from sun and ocean variability.
The big problem with increasing the pace in the hydrological cycle is the latent heat, 2500 joule per gram water. I calculated once that in order to keep the relative humidity constant at higher temperatures as per alleged CO2 doubled forcing at the same cycle rate, you’d need something about double the energy that is allegedly avaible for doubling CO2 for the additional evaporation.
The other point is, without extra water to multiply the warming of CO2, CO2 alone doesn’t come close to cause enough heating to match measurements. As the paper said, approximately the correct amount of water is falling Australia, but further to the south (this did not apply to Africa or Chile, but that is possibly a measurement issue ie maybe the rain is falling into the ocean). So at least in Australia there’s no indication of the excess water required to create CO2 warming.
From the rainfall graphs available from the Oz BOM (http://reg.bom.gov.au/cgi-bin/climate/change/timeseries.cgi?graph=rain&area=seaus&season=0112&ave_yr=0), it appears there was an increase in overall rainfall from 1900 – 1970 whilst 1970 onwards shows a decline.
Whilst the study concentrated on our Autumn rainfall, perhaps taking into account ALL available data might be useful to identify causes, particularly cyclic ones.
They could’ve saved time and money and just asked any Melbournian. We could’ve told them we observed this change. During the 80’s Melbourne’s weather would track in a pretty much Easterly direction from the Great Australian Bight, then in the 90’s our weather would track South-East across Australia bringing hotter drier weather. Then during the 00’s the weather tracks moved further South so now our weather tracks North-East from the direction of Antarctica (reversal occurred about 2008).
You can physically notice the difference as we USED to know we’d have the same weather as Perth 3 days later (Adelaide got it 2 days later). Then we had to start looking at the Western Australia Central Coast in the 90’s. Now we look at what comes out of the Southern Ocean. These last 3-4 years have been cold and wet as a result.
The Southwest US can see this intensification of the hydrologic cycle evertime the Hadely Cell expands into the Desert Southwest during the summer. Heavy thunderstorms, flash floods, and tropical cyclones hitting Baja follow in the wake of this expansion. Downstream, across the Lee of the Rockies, there are drought conditions; but, this is induced by geography more than anything else.
Eastern Australia has just experienced 3 of the wettest years in more than a decade including 2012 which was the wettest since the 1974 flood year.
CSIRO abandoned science years ago and now produce propaganda for sale.
Couple of things.
Water vapour ‘feedback’…eh?
So these clowns claim to have detected/measured and fixed a ‘stable’ rate of evaporation from the tropical OCEANS!!! and then proceed to claim that they have detected/measured a deviance from this rate which they assign to ‘greenhouse gases’. Wow.
Blind Freddy (he’s the politically incorrect, dumb Australian who is gifted with seeing the bleeding obvious)…yes Blind Freddy himself could point out that there are major shifts in SSTs in the vicinity of this vast continent which totally and directly affect the rainfall wildly different climate areas.
For instance right now, to the north of Australia the SSTs are unusually cool and the evaporation rates subsequently lower, hence the dry spring we have been having on the northern part of the east coast.
Second thing.
Blind Freddy could also point to the vast swathes of rain falling in the Pacific Ocean to the East of Australia where of course it is not measured by the droughtist, angst ridden CSIRO but goes on it’s merry way into the ocean currents.
The CSIRO really is in the grip of CO2 Warmism, it rides the vagaries of the Australian Climate (land of droughts and floods) like a surfer. It is only interested in funding.
Oh – and included in that devastating 1997-2009 millenium drought were the 2001 floods of northern NSW and South East Queensland – road transport severly disrupted due to flooding.
Eastern Australia has seen way above average rainfall since the drought broke in Spring 2009 – especially northern NSW and SE Queensland.
Wivenhoe dam in SE Queensland went from <15 % in Spring 2009 to over 65 % after the 09/10 wet season (Summer here) to 199% in January 2011 where it nearly created an even worse flood disaster because politicians listened to climate scientists claiming it would never rain again and refused to lower what is essentially a flood control dam – then tried to blame the engineers for the politicians stupidity in believing the lie that it would never rain again.
January to June 2012 was the wettest six months since 1974 – despite no major flood event like 2011.
Every major wet season in my life has coincided with LaNina conditions in Eastern Australia.
After 2 major wet years I am hoping that the ENSO meter stays in neutral territory and we have a more normal summer – but I wouldn't bet on it though.
Rosco:
The paper only takes into consideration up to 2009, just after the Hadley Cell started moving north again. As I noted above, since 2008 Melbournians have started looking at what weather is coming to us from the Southern Ocean instead of what’s coming across WA.