Climate variability in East Africa & El Niño Southern Oscillation

Mt Kilimanjaro.

Mount Kialmanjaro - Image via Wikipedia

From the Helmholtz Association of German Research Centres  another reason why Mount Kialmanjaro isn’t controlled by CO2 as Al Gore and Lonnie Thompson think.

La Ninas distant effects in East Africa

Droughts and floods are remote-controlled climate effects

5 August 2011 | Potsdam: For 20 000 years, climate variability in East Africa has been following a pattern that is evidently a remote effect of the ENSO phenomenon (El Niño Southern Oscillation) known as El Niño/La Niña. During the cold phase of La Niña, there is marginal rainfall and stronger winds in East Africa, while the El Niño warm phase leads to weak wind conditions with frequent rain. Moreover, during the coldest period of the last ice age about 18 000 to 21 000 years ago, East Africa’s climate was relatively stable and dry. This result was published by an international group of researchers from Potsdam, Switzerland, the United States, the Netherlands and Belgium in the latest issue of the journal “Science” (Vol. 333, No.6043, 05.08.2011).

ENSO with its warm phase (El Niño) and its cold phase (La Niña) is actually known as a climate phenomenon in the Pacific with global teleconnections. Using the example of climate variability in East Africa, the study shows the long-term impact of this phenomenon in this sensitive region. The sediments in Lake Challa in southeastern Kenya, at the foot of Mount Kilimanjaro, serve as a climate archive. Sample cores that were drilled here show a pattern of stripes, so called annual laminae. Each individual layer holds information about the climate. “The thickness of these layers varies according to the climate, from 0.08 to 7 millimeters,” explains Christian Wolff (University of Potsdam and GFZ German Research Centre for Geosciences). “A comparison of temperature measurements in the tropical Pacific over the last 150 years shows a strong correlation between ENSO cycles and the rhythms of droughts and floods in East Africa.”

That is to say, two climate patterns are superimposed here. The basic rhythm is provided by the annual rainy seasons, which are linked to the so-called Intertropical Convergence Zone (ITCZ). This refers to the band of clouds near the equator, which is formed by sunlight and excessive evaporation. With the sun high in June on the northern hemisphere and in December in the southern hemisphere, this band of clouds and the rain associated with it moves north- or southwards, respectively. This seasonal event is apparently superimposed by the ENSO phenomenon.

The length of the drill core allowed the tracking of climate variations to the last ice age. Biogeochemical proxy data and careful seismological exploration of the sediment layers brought together a very good agreement with the thicknesses of individual layers. It was found that even in the last glacial, when the world was about 5 degrees colder globally and thus the energy budget of the tropics system was smaller due to lower temperature, the ENSO phenomenon was seen as a superimposed pattern, albeit weaker. In comparison, the last 3000 years were warmer and more volatile, with intensive dry and drought periods, as this year, and massive rainy periods, which frequently lead to flooding. Climate models show that this trend towards an increase in extreme dry and wet phases continues on in a warming world.

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The study was funded by the DFG German Research Foundation, the ESF European Science Foundation and the U.S. National Science Foundation NSF.

Christian Wolff et al.: „Reduced Interannual Rainfall Variability in East Africa During the Last Ice Age”, Science, Vol. 333, No.6043, 05.08.2011

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15 thoughts on “Climate variability in East Africa & El Niño Southern Oscillation

  1. ENSO with its warm phase (El Niño) and its cold phase (La Niña) is actually known as a climate phenomenon in the Pacific with global teleconnections.
    LOL
    Another case of the tail that wags the dog… How about ENSO is a consequence of a global event…

  2. The climate and weather is a great subject to read and try to understand ..ths WUWT and the many people that take up the conversation…I just wanted to pass along this very interesting article that has some nice info in it …maybe someone could model it ,or better understand history of what the climate might do next week ….peace Gill now had proof of devastating droughts in the past, but not in the key ninth century. Then he discovered an extraordinary coincidence. He’d studied hundreds of papers on meteorology before he stumbled on one entitled ‘Dendrochronology, mass balance and glacier front fluctuations in northern Sweden’.
    It had been extremely cold in northern Europe at just the time of the Maya collapse, but what could possibly be the link? Gill went back to the meteorological records, and found that one of the high pressure systems in the north Atlantic had moved towards Central America at the start of the 20th century. This was a time of both drought in the Maya areas and extreme cold in northern Europe.
    Conclusive proof
    The scientists discovered that the ninth century had been the driest time in the region for 7,000 years.
    Though the circumstantial evidence was growing stronger, Gill still didn’t have direct proof of devastating drought in the Maya areas in the ninth century. He finally got that evidence when a team from the University of Florida visited Lake Chichancanab in Mexico’s Yucatan region.
    The team was interested in past climates and measured them by taking cores of mud from the bottom of the lake. The mud had built up over thousands of years – the deeper the mud, the older the shells and seeds it contained.
    Back at their labs in Gainesville, they looked at tiny shells from each part of the core, and in particular the two types of oxygen locked in them – heavy and light.
    The surfaces of shells from times of high rainfall are dominated by light oxygen. More of the heavy oxygen means the water in the lake was evaporating at that time. A core from the ninth century showed an exceptional surge of heavy oxygen, indicating it was the driest time in the region for 7,000 years.
    Here at last was the clinching evidence Gill had been searching for – exceptional drought at the time of the Maya collapse. His quest was over, but it had been an emotional journey of discovery.
    ‘There’s a certain satisfaction that I have finally understood what happened to the Maya, but as a human being it’s awful to think about what happened’, he says. http://www.world-mysteries.com/Fall_of_of%20Mayan_civilization.htm

  3. TomRude says:
    August 5, 2011 at 9:02 am
    “global teleconnections” does not tellyou what the direction is ( cause or result ) and does not even say that the connection is uni-directional.
    so, i don’t know what yyou are “LOL”ing for

  4. Drought and famine in the Horn of Africa in 2000, roughly two years after peak of large El Nino that was followed by La Nina. http://news.bbc.co.uk/1/hi/world/africa/696803.stm
    Drought and famine in the Horn of Africa in 1984, roughly two years after peak of large El Nino that was followed by La Nina. http://en.wikipedia.org/wiki/1984%E2%80%931985_famine_in_Ethiopia
    Drought and famine in the Horn of Africa in 1973, roughly two years after peak of large El Nino that was followed by La Nina. http://countrystudies.us/ethiopia/46.htm
    “By the end of 1973, famine had claimed the lives of about 300,000 peasants of Tigray and Welo, and thousands more had sought relief in Ethiopian towns and villages” and led to the overthrow of Emperor Haile Selassie.
    Drought and famine in the Horn of Africa in 1958, after large El Nino that was followed by La Nina.
    Not difficult to spot the pattern, but not easy to get a political situation in the region whereby measures can be taken to prevent widespread suffering.

  5. Scientists have known about the effects of ENSO on East African climate for almost a century. Of course, 100 years ago they didn’t dubb the teleconnection ENSO. But Sir Walker Gilbert studied very good weather records from Tahiti to Austrialia, India, as well as East Africa. The so-called Walker Circulation was discovered through the statistical studies of winds, temperature and rainfall of the South Pacific, Austrailia and Indian Oceans. Sir Walker et als discovered there was a statistical correlation between rainfall in East Africa and changes in the windfield of the Central Pacific. And changes in rainfall in East Africa directly correlated with variations in drought conditions of the Nile Valley.
    This was a groundbreaking discovery. But it would not be until the late 20th Century when the El Nino Southern Oscillation (ENSO) teleconnection would be formerly quantified. It is too bad such a bright scientist as Lonnie Thompson would muddy the waters. There is still so much to be discovered about ENSO. Yet, we chase out tails as we concentrate on a trace Greenhouse Gas. Go figure.

  6. I’m pretty sure the effect in Africa is caused more by the Indian Ocean Dipole, which is related to ENSO. During El Niño, the IOD goes into a positive phase, which causes reduced uplift near Indonesia and strong winds. This causes upwelling and the result brings a tongue of cooler water extending west from Indonesia. At the same time, warm water is bunched up against Africa where the water downwells. This warm water and reduced winds there is what brings the heavier rains to east Africa. During La Niña, uplift is concentrated near Indonesia and so the winds near Africa blow stronger, leading to a cooling of waters off the eastern African coast. This decreases precipitation there. At the same time, the warm water bunches up near Indonesia, which just feeds the cycle. In recent years, there has been an unusual lack of negative IOD events. In fact, the last time a major negative IOD event took place during NH summer was in the early 1990s. The IOD was a bit negative last winter and could very well be part of the reason Somalia is suffering form intense drought.

  7. Africa, same as Australia get affected by El Nino / La Nina. But affect of those two phenomena is not same every time. Therefore, another force plays a roll in coordination, sometime against those two. Same as the affect of the sun and the moon is different at different times on the sea-tides.
    1] clouds go around Australia and Africa as cars around traffic island, especially around Australia. (I have repeated that sentence 20 times in my book) Clouds avoid dry land. The elite will not acknowledge that; because would have exposed that water / clouds control climate ; nothing to do with CO2. 2] the second mutual influence on rainfall for the southern half of Africa and for Australia is: the amount of ice on waters around Antarctic. When is more water covered by ice – the currents bring warmwater there – ice is insulating it – that water goes back north with less coldness absorbed = increased evaporation in the waters north = better rainfall, not just Kilimanjaro. In the ideal world, climatologists would study my work – then follow which tide takes the water where. I.e. the amount of ice on waters around Antarctic and direction of currents will tell them about the following season’s rainfall.
    Unfortunately, the same idiots are demolishing as much as possible ice with the nuclear ice crushers ships. Because under their theology; ice is white = reflects the sunlight = they think is an obstacle for producing at least a small GLOBAL warming – to get them out of the mess they put themselves in, with the misleading propaganda… Without taking in consideration that: water has mirror effect also. Plus there is 6 months without sunshine, but lots of coldness to absorb without ice as insulator. Bottom line: the more ice is damaged by those ice crusher ships – water damages much more, thanks to those corridors. More damaged ice on the polar waters = worse climate / more extreme climate. On my website http://www.stefanmitich.com.au you will find some work why northern Europe /USA experienced bad winters. In my book is in more details. Here I will state a bit in two paragraphs:
    North Atlantic, Mediterranean; and to a small degree far north Pacific; produce enough raw material for 0,5m of snow for Europe / north America – the rest of the moisture goes north to replenish the ice on Arctic’s water. When is less ice on those waters – they absorb extra coldness. With double strength, as ripples are radiating that coldness south and convert all the moisture in double the amount of snow in Europe / USA = no raw material for renewal of the ice on arctic – simple arithmetic. That has started the chain reaction 3 years ago. The ice crusher ships are speeding the process. Because they are wrong and back to front on everything, they cannot comprehend the damages they are doing. First they have to accept that they are completely wrong on everything; then they can realize that they have triggered a Midi Ice Age.
    When northern winter starts – cold /dry winds from north poll go south right to Mediterranean and Asia Miner (Sirocco). To avoid vacuum above Arctic – lots of moist air from north Atlantic goes north. Unfortunately, the extra coldness is converting it all into snow = no moisture left to replenish the ice over the water on Arctic. Unfortunately, the same idiots from both camps still think that: when is and was less ice on Arctic’s waters means warmer planet… bullocks, boys, bullocks!!! As for example they use the Norwegian kayaker in 1883. No boys, it was colder than, when is less ice = colder. You want to find what changed at that time, is on my website, in the condensed version of my book. Why the river in London was freezing? Is all there.
    This is one of the reasons I am begging the Skeptics to forget about past phony GLOBAL warmings and help me to get the truth to the public, we prevent the second biggest lunacy. If you learn about the real reasons what started the last big ice age and what made it to finish; will understand what is coming soon. Same ice age is impossible now, because Gibraltar Straits is open for business, but can be much worse. Please help, plus keep this text for a record. I and the laws of physics, we are never wrong.

  8. Pretty good correlation shown in the data.
    La Nina brings drought conditions, as it has in the current year where Somalia is facing an extreme drought and famine (which was almost becoming a thing of the past in the modern world). El Nino brings increased precipitation to the horn of Africa.
    The data goes back 3000 years and they also provided a 2500 year period at the last glacial maximum showing that there was reduced rainfall as was expected.
    In overall cooler climate conditions, rainfall is less. When climate conditions are warmer, there is more rainfall. So the ice ages, the Little Ice Age, the Medieval Warm Period, the Roman Warm Period all show up in the record (with an ENSO cycle superimposed on it).
    We also know that the Sahara was more like savana during the Holocene Optimum so generally we should expect there to be more precipitation as it gets warmer, not the drought propaganda provided by the pro-AGW people.
    The impact on equatorial East Africa and the horn of Africa from the ENSO is shown in the ENSO climate impact maps so this paper just puts a “confirmed” on it.

  9. Stefan;
    Aside from some weird English “clangers”, what bothered me most about your post were the sheer self-praising arrogance and the statements about “coldness” being “absorbed”.
    “Coldness” is not absorbable. Heat can be lost or can migrate to a colder zone, but that is not moving “coldness”.
    All that said, there seem to be some important observations and guesses in your comment. But I doubt you’ll get much of an audience with that kind of ranting.

  10. Brian Short;
    Your explanation of the probable course of the drought situation is quite interesting, the Indian Ocean Dipole has however been found to influence rainfall over East Africa during its positive phase, the influence is however significant during the October-November-December(OND) season only. A pointer here is that La Nina effects could have been the dorminant causal factor given that there was already less rainfall then normal earlier in the yea.

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