From UC Berkeley: Rising temperature difference between hemispheres could dramatically shift rainfall patterns in tropics
By Robert Sanders, Media Relations
BERKELEY —
One often ignored consequence of global climate change is that the Northern Hemisphere is becoming warmer than the Southern Hemisphere, which could significantly alter tropical precipitation patterns, according to a new study by climatologists from the University of California, Berkeley, and the University of Washington, Seattle.
Such a shift could increase or decrease seasonal rainfall in areas such as the Amazon, sub-Saharan Africa or East Asia, leaving some areas wetter and some drier than today.
“A key finding is a tendency to shift tropical rainfall northward, which could mean increases in monsoon weather systems in Asia or shifts of the wet season from south to north in Africa and South America,” said UC Berkeley graduate student Andrew R. Friedman, who led the analysis.
“Tropical rainfall likes the warmer hemisphere,” summed up John Chiang, UC Berkeley associate professor of geography and a member of the Berkeley Atmospheric Sciences Center. “As a result, tropical rainfall cares a lot about the temperature difference between the two hemispheres.”
Chiang and Friedman, along with University of Washington colleagues Dargan M. W. Frierson and graduate student Yen-Ting Hwang, report their findings in a paper now accepted by the Journal of Climate, a publication of the American Meteorological Society. It will appear in an upcoming issue.
Generally, rainfall patterns fall into bands at specific latitudes, such as the Intertropical Convergence Zone. The researchers say that a warmer northern hemisphere causes atmospheric overturning to weaken in the north and strengthen in the south, shifting rain bands northward.
Impact of the Clean Air Act
Even though greenhouse gas warming of Earth has been going up since the 19th century, Chiang, Friedman and their team found no significant overall upward or downward trend in interhemispheric temperature differences last century until a steady increase beginning in the 1980s.
The researchers attribute this to human emissions of aerosols, in particular sulfates – from coal-burning power plants, for example – which cooled the Northern Hemisphere and apparently counteracted the warming effect of rising greenhouse gases until the 1970 U.S. Clean Air Act led to a downward trend in sulfur emissions. The act reduced pollution and saved more than 200,000 lives and prevented some 700,000 cases of chronic bronchitis, according to 2010 figures from the Environmental Protection Agency.
“Greenhouse gases and aerosols act in opposite directions, so for much of the 20th century they essentially canceled one another out in the Northern Hemisphere,” Chiang said. “When we started cleaning up aerosols we essentially leveled off the aerosol influence and allowed the greenhouse gases to express themselves.”
The regions most affected by this shift are likely to be on the bands’ north and south edges, Frierson said.
“It really is these borderline regions that will be most affected, which, not coincidentally, are some of the most vulnerable places: areas like the Sahel where rainfall is variable from year to year and the people tend to be dependent on subsistence agriculture,” said Frierson, associate professor of atmospheric sciences. “We are making major climate changes to the planet and to expect that rainfall patterns would stay the same is very naïve.”
20th century rainfall patterns
Many discussions of climate change focus on long-term trends in the average global temperature. The UC Berkeley and University of Washington researchers went a step further to determine how the temperature difference between the two hemispheres changed over the last century and how that may have affected tropical rainfall patterns.
Using more than 100 years of data and model simulations, they compared the yearly average temperature difference between the Northern and Southern hemispheres with rainfall throughout the 20th century and noticed that abrupt changes coincided with rainfall disruptions in the equatorial tropics.
The largest was a drop of about one-quarter degree Celsius (about one-half degree Fahrenheit) in the temperature difference in the late 1960s, which coincided with a 30-year drought in the African Sahel that caused famines and increased desertification across North Africa, as well as decreases in the monsoons in East Asia and India.
“If what we see in the last century is true, even small changes in the temperature difference between the Northern and Southern hemispheres could cause measureable changes in tropical rainfall,” Chiang said.
This bodes ill for the future, he said. The team found that most computer models simulating past and future climate predict a steadily rising interhemispheric temperature difference through the end of the century. Even if humans begin to lower their greenhouse gas emissions, the models predict about a 1 degree Celsius (2° F) increase in this difference by 2099.
As global temperatures rose over the course of the 20th century (top), the temperature between the two hemispheres changed little until the 1980s, though it has been rising since. Courtesy of Andrew Friedman.While the average temperature of the Earth is increasing as a result of dramatic increases in atmospheric greenhouse gases, primarily carbon dioxide, the Earth is not warming uniformly. In particular, the greater amount of land mass in the north warms up faster than the ocean-dominated south, Chiang said. He and his colleagues argue that climate scientists should not only focus on the rising global mean temperature, but also the regional patterns of global warming. As their study shows, the interhemispheric temperature difference has an apparent impact on atmospheric circulation and rainfall in the tropics.
“Global mean temperature is great for detecting climate change, but it is not terribly useful if you want to know what is happening to rainfall over California, for example,” Chiang said. “We think this simple index, interhemispheric temperature, is very relevant on a hemispheric and perhaps regional level. It provides a different perspective on climate change and also highlights the effect of aerosols on weather patterns.”
The research was supported by the U.S. Department of Energy and the National Science Foundation.
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“could”. “might”. “if”. “some areas wetter and some drier”. “model”.
Throw in a little anthropomorphizing of rainfall and get a nice government grant for churning out crap. This one really had me laughing:
“…allowed the greenhouse gases to express themselves.”
Mike
Stephen Wilde says:
April 3, 2013 at 4:31 am
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Plus 1.
As Steven points out, there is more land in the Northern Hemisphere and more ocean in the Southern Hemisphere, and hence response between the two hemispheres is different (whatever be the cause of warming) . Because of this, personally, I would expect to see variations in rainfall patterns
They have to keep the aerosol meme going since without that the AGW argument that CO2 is a strong driver is all but a busted flush. However, there is no empirical evidence backing up the aerosol conjecture. The measurements were simply not being done and hence the aerosol argument is conjecture.
It is difficult to see how aerosols played out during the LIA, or the Viking, Roman, Minoan warm periods etc when according to the warmists CO2 levels were stable during the Holocene right up to the industrial revolution.
Doug says:
April 3, 2013 at 6:33 am
//////////////////////////////////
But so it should be. The fact is no body knows very much about climate, what drives it, what real world response there will be to changes in drivers/forcings/feedbacks.
One of the main problems with CAGW is the certainty with which claims are made, when in reality and if honest, they would be couched in terms of may be, possibly, might happen, do not know for sure, etc. I do not consider that we are at the stage where any of their claims could be couched in terms of probable in the sense of it being a better than 50/50 outcome.
Every time you read “could” replace it with “could fail to” . No worrires.
OMG… “…and allowed the greenhouse gases to ‘express themselves’.” – Next they will be giving speeches in Congress. Naughty GHGs!
It should be noted that the extreme AGW theory predicted most of the warming should occur in the tropics. There is no significant observed warming in the tropics which supports Lindzen and Choi’s satellite analysis that shows cloud cover in the tropics increase or decreases to resist (negative feedback) planetary temperature change by reflecting more or less sunlight off into space. The extreme AGW theory predicted that the troposphere at around 10 km in the tropics would experience the most warming on the planet (The tropical troposphere hot spot.) The reason the hot spot is at 10 km is the greenhouse warming affects of CO2 are already saturated in the lower atmosphere. There is no observed tropical troposphere hot spot.
The extreme AGW paradigm pushers ignore the observations which clearly indicate the majority of the 20th century warming has not due to increases in atmospheric CO2. The majority of the warming was in Northern Hemisphere with most warming occurring in the Arctic. Interestingly the paleoclimatic specialists have remained silent on the fact that are cycles of warming and cooling that follow the same pattern as the 20th century warming in the paleoclimatic record. The phenomena where the Arctic and Greenland ice sheet warm and the Antarctic ice sheet cools and vise versa is called the polar see-saw.
http://www.climate4you.com/images/GISP2%20TemperatureSince10700%20BP%20with%20CO2%20from%20EPICA%20DomeC.gif
Interestingly there are cosmogenic isotope changes at each and every polar see-saw event which indicates there changes to solar magnetic cycle are causing what the cycle. i.e. There is a smoking gun that connects the sun as a serial climate changer. The missing piece of the logical puzzle is how does the sun cause cyclic climate change.
As the solar magnetic cycle has been abruptly interrupted we will have a chance to observe the mechanisms. Based on what has happened in the past the planet will now cool.
Comment:
One of the reasons the Southern Hemisphere is colder than the Northern Hemisphere is the South Atlantic geomagnetic anomaly. The geomagnetic field intensity is 30% less than the main geomagnetic field in the region of the Southern Atlantic geomagnetic anomaly. The Southern Atlantic geomagnetic anomaly is located east of South America. As one can see there is a large cold spot located in the vicinity of the Southern Atlantic geomagnetic anomaly which is consistent with Svensmark’s mechanism. (The amount of low level clouds, the lifetime of low level clouds, and the albedo of low level clouds are affect by galactic cosmic rays GCR (GCR are mostly very, very, high speed protons that are believed to be created by super nova. The GCR strike the atmosphere and create ions. An increase in ions, result in an increase in low level clouds, particularly over the ocean. The ion mediated low level cloud mechanism is strongest in the latitudes 40 to 60.)
William: The following is link to ocean surface temperature anomalies.
http://www.ospo.noaa.gov/data/sst/anomaly/2013/anomnight.4.1.2013.gif
William: The following are a few papers that discuss the polar see-saw.
http://www.agu.org/pubs/crossref/2003/2003GL017115.shtml
Timing of abrupt climate change: A precise clock by Stefan Rahmstorf
Many paleoclimatic data reveal a approx. 1,500 year cyclicity of unknown origin. A crucial question is how stable and regular this cycle is. An analysis of the GISP2 ice core record from Greenland reveals that abrupt climate events appear to be paced by a 1,470-year cycle with a period that is probably stable to within a few percent; with 95% confidence the period is maintained to better than 12% over at least 23 cycles. This highly precise clock points to an origin outside the Earth system; oscillatory modes within the Earth system can be expected to be far more irregular in period.
http://arxiv.org/abs/physics/0612145v1
The Antarctic climate anomaly and galactic cosmic rays
Borehole temperatures in the ice sheets spanning the past 6000 years show Antarctica repeatedly warming when Greenland cooled, and vice versa (Fig. 1) [13, 14]. North-south oscillations of greater amplitude associated with Dansgaard-Oeschger events are evident in oxygenisotope data from the Wurm-Wisconsin glaciation[15]. The phenomenon has been called the polar see-saw[15, 16], but that implies a north-south symmetry that is absent. Greenland is better coupled to global temperatures than Antarctica is, and the fulcrum of the temperature swings is near the Antarctic Circle. A more apt term for the effect is the Antarctic climate anomaly.
Attempts to account for it have included the hypothesis of a south-flowing warm ocean current crossing the Equator[17] with a built-in time lag supposedly intended to match paleoclimatic data. That there is no significant delay in the Antarctic climate anomaly is already apparent at the high-frequency end of Fig. (1). While mechanisms involving ocean currents might help to intensify or reverse the effects of climate changes, they are too slow to explain the almost instantaneous operation of the Antarctic climate anomaly.
Figure (2a) also shows that the polar warming effect of clouds is not symmetrical, being most pronounced beyond 75◦S. In the Arctic it does no more than offset the cooling effect, despite the fact that the Arctic is much cloudier than the Antarctic (Fig. (2b)). The main reason for the difference seems to be the exceptionally high albedo of Antarctica in the absence of clouds.
http://www.johnstonanalytics.com/yahoo_site_admin/assets/docs/LindzenChoi2011.235213033.pdf
On the Observational Determination of Climate Sensitivity and Its Implications
Richard S. Lindzen1 and Yong-Sang Choi2
We estimate climate sensitivity from observations, using the deseasonalized fluctuations in sea surface temperatures (SSTs) and the concurrent fluctuations in the top-of-atmosphere (TOA) outgoing radiation from the ERBE (1985-1999) and CERES (2000- 2008) satellite instruments. Distinct periods of warming and cooling in the SSTs were used to evaluate feedbacks. An earlier study (Lindzen and Choi, 2009) was subject to significant criticisms. The present paper is an expansion of the earlier paper where the various criticisms are taken into account. … …We again find that the outgoing radiation resulting from SST fluctuations exceeds the zerofeedback response thus implying negative feedback. In contrast to this, the calculated TOA outgoing radiation fluxes from 11 atmospheric models forced by the observed SST are less than the zerofeedback response, consistent with the positive feedbacks that characterize these models. ….
…The heart of the global warming issue is so-called greenhouse warming. This refers to the fact that the earth balances the heat received from the sun (mostly in the visible spectrum) by radiating in the infrared portion of the spectrum back to space. Gases that are relatively transparent to visible light but strongly absorbent in the infrared (greenhouse gases) interfere with the cooling of the planet, forcing it to become warmer in order to emit sufficient infrared radiation to balance the net incoming sunlight (Lindzen, 1999). By net incoming sunlight, we mean that portion of the sun’s radiation that is not reflected back to space by clouds, aerosols and the earth’s surface. CO2, a relatively minor greenhouse gas, has increased significantly since the beginning of the industrial age from about 280 ppmv to about 390 ppmv, presumably due mostly to man’s emissions. This is the focus of current concerns. However, warming from a doubling of CO2 would only be about 1C (based on simple calculations where the radiation altitude and the Planck temperature depend on wavelength in accordance with the attenuation coefficients of well mixed CO2 molecules; a doubling of any concentration in ppmv produces the same warming because of the logarithmic dependence of CO2’s absorption on the amount of CO2) (IPCC, 2007). This modest warming is much less than current climate models suggest for a doubling of CO2. Models predict warming of from 1.5C to 5C and even more for a doubling of CO2. Model predictions depend on the ‘feedback’ within models from the more important greenhouse substances, water vapor and clouds. Within all current climate models, water vapor increases with increasing temperature so as to further inhibit infrared cooling. Clouds also change so that their visible reflectivity decreases, causing increased solar absorption and warming of the earth. Cloud feedbacks are still considered to be highly uncertain (IPCC, 2007), but the fact that these feedbacks are strongly positive in most models is considered to be an indication that the result is basically correct. Methodologically, this is unsatisfactory. Ideally, one would seek an observational test of the issue. Here we suggest that it may be possible to test the issue with existing data from satellites.
It appears that the Northern Hemisphere is cooling. apparently, according to the GWPF, NOAA is suggesting that it is cooling at a rate of 0.27degC per decade.
http://www.thegwpf.org/noaa-northern-hemisphere-trend-cooling-27c-decade-1998-2013/
I have not checked the data, but CET shows that the UK has cooled by about 0.5degC since 2000. This is quite a bit more than the NOAA assessment.
More worrying CET suggests that the UK in the winter season (December to February inclussive) has cooled by 1.5degC since 2000.
So the temperature balance between the two hemispheres may be changing in a manner not considered by the Berkeley paper. It may be that we are now in a cycle which will see the temperatures moving towards more equalisation. Perhaps they need to go back to look at the empirical data (which admittedly is recent and of relatively short duration) and go back to the drawing board.
Some day, papers like this will be used as ‘Exhibit A: Pitfalls and Pratfalls’ in climate science courses taught by competent professors at responsible institutions of higher learning. Or so I imagine.
replace ‘could’ with ‘will’ and every person here will trot out ‘science is never settled”
The formula is simple and stuck on stupid.
Say “will”. The chorus responds, “science is never settled”
Say “could” The chorus responds, “these guys know nothing”
Its like CalvinBall
Is UK heading for a new Little Ice Age?
It’s official, CET March coldest for 125 years.
http://www.vukcevic.talktalk.net/CET-March.htm
William Astley says:
April 3, 2013 at 8:33 am
Sir:
Did you happen to read & view in the comments replying to yours in Anthony’s “Breaking” post the quotations & footage (from Zoot Cadillac, Jimbo, et al.) of Dr. Hansen’s demented, delusional blathering about Earth’s being on the Venus Express, etc (to include from his book)? If so, would you now agree that his repeatedly stated beliefs are those of a blithering idiot, raving lunatic or shameless liar, or some combination thereof?
Thanks for your response.
What a pathetic press release from authors who are desperate to “fit in” the CAGW bandwagon.
The shifting of pluviogenic structures has been observed and well understood especially since the late Marcel Leroux retrieved weather data in tropical Africa and analyzed them for his PhD thesis in 1983, later republished and updated by Springer/Praxis with the entire dataset in CD in 2001.
http://www.springer.com/earth+sciences+and+geography/atmospheric+sciences/book/978-3-540-42636-3
In French, on the Sahel drought:
http://ddata.over-blog.com/xxxyyy/2/32/25/79/Leroux-La-dynamique-de-la-grande-secheresse-sahelienne.pdf
In 1993, the author explained in a seminal paper how and why these shifts occur:
http://ddata.over-blog.com/xxxyyy/2/32/25/79/Leroux-Global-and-Planetary-Change-1993.pdf
Data and first hand observations from Leroux over these armchair climatists’ activism.
The more obvious observation would be that it may be that temperature data in the North has been overstated.
The authors, Chiang and Friedman are also self congratulating obfuscators:
In their 2012 paper, they dare write: http://www.annualreviews.org/eprint/vymzZYuaARgtA4e3eyiT/pdf/10.1146/annurev-earth-042711-105545
“4. THE INFLUENCE OF EXTRATROPICAL COOLING
ON TROPICAL CLIMATE CHANGE
The previous section highlights the sensitivity of the tropical rainfall climate to change. We
now address how thermal forcing from the extratropics can drive such changes. Chiang & Bitz
(2005) and Broccoli et al. (2006) were the first to explicitly propose atmospheric mechanisms
underlying the influence of extratropical cooling on the tropical ITCZ climate.”
Really? No Mr. Chiang, you were certainly not the first.
In 1993, Leroux explained in a seminal paper how and why these shifts occur:
http://ddata.over-blog.com/xxxyyy/2/32/25/79/Leroux-Global-and-Planetary-Change-1993.pdf
Notwithstanding Leroux’s thesis and book Meteorology and Climate of Tropical Africa…
Shame on you Chiang/Friedman for not properly doing reference checking!
“… said UC Berkeley graduate student Andrew R. Friedman, who led the analysis”
###
Yet another victim of Marxist education playing scientist to the cheers of his leftist buddies. It always seems to be students and post grads writing these headline grabbing fact free studies.
I have read several papers documenting movement, sometimes on century scale durations, of the ITCZ in Africa and South America. There are pretty well-documented cases where large areas transitioned from savannah to forest and back again to savannah. Overall, I would say that this is nothing unusual. Climate is not a static entity. It is always changing.
What do you expect from grant administration that does not even check for plagiarism on grant applications according to audits?
vukcevic says:
April 3, 2013 at 9:14 am
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The UK is certainly getting colder as noted in my post above (See .April 3, 2013 at 8:37 am)
It is not only the UK that has had a cold March, Germany has experienced its coldest March for 130 years.
Comparing hemispheric differences on their temperature chart I note that the big difference between north and south begins around 1980, at the beginning of the satellite era. By the twenty-first century the north is ahead by 0.2 to 0.3 degrees Celsius. I consider this difference faked because that same difference shows up when ground-based temperature curves are compared with satellite temperature curves. There is hanky-panky being performed with these temperature curves to make the warming seem higher than it actually is. Proof that they have manipulated temperature curves is found in the temperature curves themselves. The software they used to manipulate their data had some unanticipated consequences that they did not know about. Specifically, it left high temperature spikes pointing upward at the beginning months of a number of years. They show up as a sore thumb when you use my method of temperature analysis in “What Warming?” – a book I wrote in 2010. Most prominent of these extraneous spikes are located at the beginnings of years 1990, 1995, 1998, 1999, 2002, 2007, and 2012. They are found in exactly the same locations and line up perfectly in HadCRUT, GISSTEMP, and NCDC temperature curves. Since these data-sets all carry the same signature of computer tampering it is highly probable that it was a cross-ocean cooperative venture that produced these doctored curves. In my opinion the only temperatures that can be trusted today are satellite temperature measurements. These compromised ground-based curves should not be used after 1979 when satellite temperatures begin. Older data should be analyzed with appropriate equipment to determine how far back the temperature manipulation extends.
Steven Mosher says:
April 3, 2013 at 9:04 am
replace ‘could’ with ‘will’ and every person here will trot out ‘science is never settled”
The formula is simple and stuck on stupid.
Say “will”. The chorus responds, “science is never settled”
Say “could” The chorus responds, “these guys know nothing”
Its like CalvinBall
****************************************************************************
What science do you consider settled? IMO faith in settled science is an unscientific attitude, indeed fundamentally anti-scientific.
OK, it’s settled that the earth goes around the sun, but other aspects of Copernicus’ heliocentric theory (which took a long time to displace the settled geocentric consensus) have been falsified. Planetary orbits are eccentric, not circular, for instance. The sun is not at rest at the center of the universe, nor does a sphere of fixed stars surround it. Astronomy has continued to march on through the centuries, with planets discovered to have multiple moons & nebulae to be galaxies, with a vastly expanded universe expanding, etc. It, or at least astrophysics & cosmology, are arguably more unsettled now than ever. And that’s a good thing.
Physics might have seem settled after Newton, but then along came electromagnetism, radioactivity, relativity & quantum mechanics. The more real scientists learn (or think they’ve learned), the more honest searchers realize there remains to find out.
Examples abound in every science, least of all is climatology settled.
Settled, consensus opinion is that general circulation models do a good job of predicting future global temperature, precipitation, storminess, sea level, etc. Furthermore, there is no possible other explanation for what the models show than man-made GHG forcings, so it has to be we evil humans.
“Deniers” (ie practitioners of real science) posit various other causes of climate change than do the man-made greenhouse gas mafiosi. These skeptics claim that the models are GIGO, rely on faulty data & make assumptions not based on actual observed data, while ignoring such important considerations as clouds. Their view has been vindicated by reality so far, & CAGW will be falsified further if coming years are colder, as many skeptics predict.
The most skeptical group feels that climate is totally chaotic & therefore cannot be predicted meaningfully. They are convinced that the cycles seen by Group 2 & the non-GHG forcings argued for them may be as erroneous as the simplistic models of defenders of “settled, consensus science”.
Whoever proves right, the fact is that skeptics anxious to learn more instead of accepting GHG orthodoxy have found out a lot since CAGW was proposed in the ’80s (the Pacific Decadal Oscillation wasn’t discovered until 1997, by a PNW fisheries researcher, not a “settled consensus scientist”), but the approved “experts” still cling to the false god of CO2. Just as approved expert geologists did to anti-catastrophism & unmoving continents until they couldn’t deny reality anymore in the 1960s.
All increased oceanic and atmospheric joules caused by a slower lapse rate due to anthropogenic emissions of carbon dioxide from burning fossil fuels are hereby prohibited from crossing the equator. Violators face a $100 fine and up to sixty days in jail per incident.
An attorney spokesman for the joules said they will file an immediate injuction against the prohibition in Federal District Court, saying “it’s unfair to restrict the travel of these particular joules, when other joules are free to cross the equator without restriction.” Immigration experts have already begun to speculate that the new law will create underground markets which include joule coyotes who charge the joules exhorbitant prices across the boundary. Joule rights activists decry the new law saying…
I have seen a theory that because the sahara was warmer 10k years ago it caused a general uplift which in turn induced an inflow[monsoon-like] from the atlantic rather like the indian monsoon…it is no longer ‘hot’ enough ironically!
Arno, I have just plotted the UAH NH-SH difference and there is a slow increase over the 35 years of data, but it is pretty small. A linear trend (in Excel – I am not confident with other stats) is 0.4C (0.13 per decade) – but the R^2 is crap so a linear fit is useless.
I agree with you that the spatial distribution of surface data points will skew the comparison so what I am wondering is how big is the difference between NH and SH in HadCRUT etc?
michael hart says:
April 3, 2013 at 3:38 am
“It’s always in the future, isn’t it? If they haven’t made any accurate previous predictions of today’s rainfall then they should make their predictions now and get back to us in a couple of decades.”
Yeah, very well said. They should do what physical scientists do. Once they have a relevant set of physical hypotheses with a record of confirmation then they should get back to us.
DesertYote says:
April 3, 2013 at 9:56 am
“… said UC Berkeley graduate student Andrew R. Friedman, who led the analysis”
###
Yet another victim of Marxist education playing scientist to the cheers of his leftist buddies. It always seems to be students and post grads writing these headline grabbing fact free studies.
—————————————————————————————————————–
It`s all about education,
UK,
Teachers attacked Michael Gove’s new school curriculum yesterday for placing too much emphasis on “hard facts”.
The biggest teachers’ union vowed to oppose the changes, claiming that they were culturally narrow and would squeeze out creativity. Some teachers said schools should not produce pupils who “just know stuff” and that children could look up facts on the internet.
Look up the facts on the internet, the first place they go is Wikipedia.