Claim: Greenhouse gases linked to past African rainfall

From UCAR/NCAR, something that seems like a wild claim to me, especially since all they have is proxy evidence (sediments) and model runs, not direct evidence. It is a stretch IMHO.

Greenhouse gases linked to past African rainfall

December 04, 2014

BOULDER — New research demonstrates for the first time that an increase in greenhouse gas concentrations thousands of years ago was a key factor in causing substantially more rainfall in two major regions of Africa. The finding provides new evidence that the current increase in greenhouse gases will have an important impact on Africa’s future climate.

The study, led by the National Center for Atmospheric Research (NCAR), is being published this week in Science.

“The future impact of greenhouse gases on rainfall in Africa is a critical socioeconomic issue,” said NCAR scientist Bette Otto-Bliesner, the lead author. “Africa’s climate seems destined to change, with far-reaching implications for water resources and agriculture.”

The research drew on advanced computer simulations and analyses of sediments and other records of past climate. It was funded by the National Science Foundation, which is NCAR’s sponsor, and the Department of Energy Office of Science.

A mysterious period of rain

Otto-Bliesner and her co-authors in the United States and China set out to understand the reasons behind dramatic climate shifts that took place in Africa thousands of years ago.

Ubari Oasis in southern Libya

Lakes and other water features, such as the Ubari Oasis in southern Libya, were more prevalent across now-dry parts of Africa during past periods of more-plentiful precipitation. (Wikimedia Commons photo by Sfivat.)

As the ice sheets that had covered large parts of North America and northern Europe started retreating from their maximum extent around 21,000 years ago, Africa’s climate responded in a way that has puzzled scientists. Following a long dry spell during the glacial maximum, the amount of rainfall in Africa abruptly increased, starting around 14,700 years ago and continuing until around 5,000 years ago. So intense was the cumulative rainfall, turning desert into grasslands and savannas, that scientists named the span the African Humid Period (AHP).

The puzzling part was why the same precipitation phenomenon occurred simultaneously in two well-separated regions, one north of the equator and one to the south. Previous studies had suggested that, in northern Africa, the AHP was triggered by a ~20,000-year cyclic wobble in Earth’s orbit that resulted in increased summertime heating north of the equator. (In contrast, the northern hemisphere today is closest to the Sun in winter rather than summer.) That summertime heating would have warmed the land in such a way as to strengthen the monsoon winds from the ocean and enhance rainfall.

But Otto-Bliesner said the orbital pattern alone would not explain the simultaneous onset of the AHP in southeastern equatorial Africa, south of the equator, since the wobble in Earth’s orbit led to less summertime heating there rather than more. Instead, the study revealed the role of two other factors: a change in Atlantic Ocean circulation that rapidly boosted rainfall in the region, and a rise in greenhouse gas concentrations that helped enhance rainfall across a wide swath of Africa.

Tracing multiple causes of a wetter Africa

As Earth emerged from the last Ice Age, greenhouse gases, especially carbon dioxide and methane, increased significantly—reaching almost to pre-industrial levels by 11,000 years ago—for reasons that are not yet fully understood. It was, the authors note, the most recent time during which natural global warming was associated with increases in greenhouse gas concentrations. (Because of feedbacks between the two, greenhouse gas concentrations and global temperature often rise and fall together across climate history.)

The end of the last Ice Age also triggered an influx of fresh water into the ocean from melting ice sheets in North America and Scandinavia about 17,000 years ago. The fresh water interfered with a critical circulation pattern that transports heat and salinity northward through the Atlantic Ocean, much like a conveyer belt. The weakened circulation led to African precipitation shifting toward southernmost Africa, with rainfall suppressed in northern, equatorial, and east Africa.

When the ice sheets stopped melting, the circulation became stronger again, bringing precipitation back into southeastern equatorial and northern Africa. This change, coupled with the orbital shift and the warming by the increasing greenhouse gases, is what triggered the AHP.

To piece together the puzzle, the researchers drew on fossil pollen, evidence of former lake levels, and other proxy records indicating past moisture conditions. They focused their work on northern Africa (the present day Sahel region encompassing Niger, Chad, and also northern Nigeria) and southeastern equatorial Africa (the largely forested area of today’s eastern Democratic Republic of Congo, Rwanda, Burundi, and much of Tanzania and Kenya).

In addition to the proxy records, they simulated past climate with the NCAR-based Community Climate System Model, a powerful global climate model developed by a broad community of researchers and funded by the National Science Foundation and Department of Energy, and using supercomputers at the Oak Ridge National Laboratory.

By comparing the proxy records with the computer simulations, the study demonstrated that the climate model got the AHP right. This helps to validate its role in predicting how rising greenhouse gas concentrations might change rainfall patterns in a highly populated and vulnerable part of the world.

“Normally climate simulations cover perhaps a century or take a snapshot of past conditions,” Otto-Bliesner said. “A study like this one, dissecting why the climate evolved as it did over this intriguing 10,000-year period, was more than I thought I would ever see in my career.”

About the article

Title: Coherent changes of southeastern equatorial and northern African rainfall during the last deglaciation

Authors: Bette L. Otto-Bliesner, James M. Russell, Peter U. Clark, Zhengyu Liu, Jonathan T. Overpeck, Bronwen Konecky, Peter deMenocal, Sharon E. Nicholson, Feng He, Zhengyao Lu

Publication: Science, doi: 10.1126/science.1259531

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49 thoughts on “Claim: Greenhouse gases linked to past African rainfall

  1. I have not seen the paper yet. But there may be some serious problems here. The age of 14,7 ka age suggest a codate with the Bolling event, visible in Greenland ice cores, but not in Antarctic ice cores. That this event was associated with a strong warming in the Northern Hemisphere, is challenged by numerous publications, for instance “The Mystery Interval”, Denton et al 2006 http://www.pages-igbp.org/download/docs/newsletter/2006-2/science_highlights/Denton_etal_2006-2%2814-16%29.pdf
    but I could cite many others. Also the 14.7 Ka date of start of the African humid period is also associated with a sudden spike in snow accumulation in the greenland ice cores, which could suggest that large changes in hemispheric precipitation patterns, for whatever unknown reason, is all you need to explain excursion changes in isotope proxies and methane concentrations. We don’t need temperature for that, especially since Antarctic isotopes and CO2 do not correlate at all.

  2. “Previous studies had suggested that, in northern Africa, the AHP was triggered by a ~20,000-year cyclic wobble in Earth’s orbit that resulted in increased summertime heating north of the equator. (In contrast, the northern hemisphere today is closest to the Sun in winter rather than summer.) That summertime heating would have warmed the land in such a way as to strengthen the monsoon winds from the ocean and enhance rainfall.
    But Otto-Bliesner said the orbital pattern alone would not explain the simultaneous onset of the AHP in southeastern equatorial Africa, south of the equator, since the wobble in Earth’s orbit led to less summertime heating there rather than more.”
    ———————————————————————————————————————
    Perhaps I am being too nit picky but why are they referring to “northern Africa” on one hand and “southeastern equatorial Africa” on the other. I wouldn’t think that obliquity changes would have too much effect on any area that is near the equator especially since almost all of their “southeastern equatorial Africa” is north of the Tropical of Capricorn and still in a tropical climate zone whereas almost all of their “northern Africa” is north of the Tropic of Cancer and out of a tropical climate zone.

  3. Is there any record (ice cores perhaps?) of the Chlorine, Bromine and Iodine concentrations in the atmosphere for this same period?
    The reason I ask is that there is an alternative explanation for the temperature changes which relates to polar ozone concentrations, its elevation, solar CR – basically the opening and closing of a heat vent valve at each pole.
    The storyline is pretty complicated in the paper above – kind of a lot of assumptions. If there is a better fitting and simpler explanation that is related to polar cooling (or not), and not tropical tropospheric warming, we should consider it as well. Do we have a good grasp of solar CR variation from 10Be for this period? Can we separate CR from GCR if there is?
    Blaming CO2 and methane seems a bit too easy when the variation was small and the effect so large. Lots of invocations in there. I think there was (proposed) a high latitude, high velocity comet strike at about that time (3100 BC) which wiped out farming and many temperate tree species in the UK. The Earth is still wobbling from it – about 10 feet at the pole. Paul Dunbavin’s book with the crazy name describes it very well in Ch1-3 – maybe the best explanation in print of the Earth’s three ‘poles’.

    • The claim is that with “advanced models” first ….. Why would they use ” unadvanced models”. …and second, this is an implication that the previous models were, as my son would say ” no damn Bueno “

  4. So implied here (without saying it directly) is that GHG increases will be good a good thing, as the desert retreats across North Africa. One more reason to feel good about the industrialization of the world.
    (But how can this be published?)

  5. “Africa’s climate seems destined to change,…..

    Brilliant!

    The research drew on advanced computer simulations and analyses of sediments and other records of past climate.

    So there you have it.

  6. Since these chaps want to talk about proxies and carbon dioxide let’s take a look. Is that 425ppm I see about 12,750 years ago. Unprecedented!

    Abstract
    – Margret Steinthorsdottir et. al. – 15 May 2013
    Stomatal proxy record of CO2 concentrations from the last termination suggests an important role for CO2 at climate change transitions
    …The record clearly demonstrates that i) [CO2] were significantly higher than usually reported for the Last Termination and ii) the overall pattern of CO2 evolution through the studied time period is fairly dynamic, with significant abrupt fluctuations in [CO2] when the climate moved from interstadial to stadial state and vice versa. A new loss-on-ignition chemical record (used here as a proxy for temperature) lends independent support to the Hässeldala Port [CO2] record. The large-amplitude fluctuations around the climate change transitions may indicate unstable climates and that “tipping-point” situations were involved in Last Termination climate evolution. The scenario presented here is in contrast to [CO2] records reconstructed from air bubbles trapped in ice, which indicate lower concentrations and a gradual, linear increase of [CO2] through time….

    http://ars.els-cdn.com/content/image/1-s2.0-S0277379113000553-gr7.jpg

      • Hey Bill,
        As far as I’m concerned the post’s paper is speculation driven by proxies and models. I’m sure someone can show how co2 played a part in the Sahara’s desertification too! Here is a paper published in 2001 that says:

        Paper – August 2001
        Desertification and a shift of forest species in the West
        The results of this research provide evidence for desertification in the West African Sahel. These documented impacts of desertification foreshadow possible future effects of climate change….
        http://www.int-res.com/articles/cr/17/c017p217.pdf

        Fast forward to the future and what do I see?

        Abstract – May 2013
        The causes, effects and challenges of Sahelian droughts: a critical review
        …….However, this study hypothesizes that the increase in CO2 might be responsible for the increase in greening and rainfall observed. This can be explained by an increased aerial fertilization effect of CO2 that triggers plant productivity and water management efficiency through reduced transpiration. Also, the increase greening can be attributed to rural–urban migration which reduces the pressure of the population on the land…….
        http://link.springer.com/article/10.1007/s10113-013-0473-z
        ==============
        Abstract – 19 March 2014
        Martin Brandt et al
        Local Vegetation Trends in the Sahel of Mali and Senegal Using Long Time Series FAPAR Satellite Products and Field Measurement (1982–2010)
        …..Significant greening trends from 1982 to 2010 are consistently observed in both GEOV1 and GIMMS3g FAPAR datasets. Annual rainfall increased significantly during the observed time period, explaining large parts of FAPAR variations at a regional scale. Locally, GEOV1 data reveals a heterogeneous pattern of vegetation change, which is confirmed by long-term ground data and site visits……
        Remote Sensing 6, pp. 2408-2434
        http://www.mdpi.com/2072-4292/6/3/2408/htm

  7. The primary greenhouse gas is water vapor, and it is at the core of the most powerful Atmospheric engine, the water cycle. Let’s talk about that and stop paying people to put CO2 in every equation. CO2 is insignificant as a greenhouse gas and only changes state to and from a solid at minus 109 degrees F. Forgetaboutit!

  8. Piffle. Seriously, who thinks this stuff up?
    How many factors have to line up to have humid air and lots of rainfall in North Africa? CO_2 levels then — to the extent that we know them at all — were almost certainly somewhere in between present levels and mid-ice age low-water levels of 180-190 ppm. There isn’t the slightest shred of evidence, or any chance of putting any together, that supports the assertion that increasing CO_2 levels increases the level of rainfall, even over the well over 33% increase from the mid 19th century to the present. North Africa was a desert then, and is a desert now.
    Was CO_2 a “factor” that contributed to overall climate and temperature? Sure, probably. Still is. Is that factor, or the resulting temperature, a sufficient cause of desertification? No. Or hell, maybe yes, but good luck proving it. We can’t even predict or explain the current climate, with the best of data satellites can provide, and they’re drawing astounding conclusions on the basis of the most indirect of evidence of causality in a world where we had literally not one single scientific instrument.
    I like goats as a cause of the Sahara better than that. There really is a decent reason to think that the Sahara is anthropogenic, but not from CO_2.
    rgb

    • Its probably reasonable to expect much drier air during the glacial maximum, at least in the temperate and polar areas with cold air’s low ability to retain moisture, and increased humidity with warming and melting of the ice both because any tropical air moving north is going to lose its moisture as snow in cold period and as rain in the warm. I know it isn’t instrumentation and recorded observation and I’ve uncritically accepted that the abundance or scarcity of stomata on leaves and leaf fossils is at least a qualitative indication of CO2 availability.
      Probably the best thought experiment about these things is to reflect on what conditions developed to cause the locking of over 50km^3 of ice in the continental glaciers, all taken from the air as snow. What else could it be but moisture from tropical areas drawn largely from the oceans, transported poleward, cooling and falling as snow. I would suggest that we have a simple air conditioner. Lets model this. Maybe we can take another look at the ice cores and say gee the snow came down like crazy for the first 3000 years and then it gradually slowed and stopped. Maybe the tropical ocean, trying to maintain its level of heating by the sun, gradually got rid of all the clouds and now it had nowhere else to turn and started to cool somewhat, too. There appears to be a ceiling on tropical heating of the sea surface -demonstrably 31C- but their is no similar cap on cooling of these same oceans once all the stops are pulled out and the sky is clear. Heaven forbid if one or more big volcanoes spew ash and other sun-blocking stuff into the air during this situation.
      You have eloquently explored on a number of occasions the chaotic non-linear multi-coupled system comprising atmosphere, oceans, sun, affects of aerosols, clouds, radiation feedbacks, etc. I would suggest that this may be so EXCEPT during the development and growth of ice during the onset and quiet life of glacial periods. I think here we have a relatively boring, non-chaotic, simply coupled process that is easy to model. The questions we are having difficulty with are what conditions caused them to go into this state and what finally caused them to exit it after thousands of years. Milankovich? plus other things?
      We may make more real progress in climate science by concentrating on these two conditions. So what if the warm periods are chaotic. Boiling up chicken soup is a chaotic system when you look at the details, both water and pepper and parsely going up and down on rotating cells, perhaps chicken bones conducting heat better than chicken flesh, bubbles, steam and some volatile aromatic emissions…. but in the end we end up with familiar chicken soup that basically tastes the same as the last ones and we put it through another chaotic system. When we freeze the leftover soup in a ziplock bag, it just sits there. Lets boil up a thousand chicken soups using chickens, pots, amounts of ingredients – all the same for the first 500 and vary them for the rest. Use lots of thermocouples, radiation measurements, humidity sensors, etc.
      It seems fruitless to select one reactant, CO2 and assume we can understand much. It seems equally fruitless to agonize over impossible complexities. Eemian chicken soup may have been a bit different but it would be recognizable. A good chef can make hollandaise sauce despite the chaos of the details. Certainly what we have been doing for the past 40 years hasn’t been productive. We find that scientists from 40 years before that may have been more advanced than we are now (Guy Calendar: http://climatecrocks.com/2013/04/23/guy-callendar-called-it-75-years-ago/ comes to mind)

      • “…what conditions caused them to go into this state and what finally caused them to exit it after thousands of years. Milankovich? plus other things?”
        Ice stacking to the extent that it lowers sea levels significantly. As the glaciers and ice sheets grow, their weight and insulation values can work to undermine them. As a glacial continues more freshwater is dammed above sea levels in ice sheets. Given enough time, dams fail. The freshwater makes its way to somewhat lower latitudes where it is warmed by the sun. To consistently exit a glacial period, we need a regime change, a reversal, an ice collapse.

  9. This has not been much of a mystery. The melting of the NH ice sheets is associated with the so-called Pluvial Period, obvious for over a century in for instance, the periglacial lakes of the American West, of which the Great Salt is a remnant (of glacial Lake Bonneville).
    The GHG responsible for more rain was, surprise!, water! As the glaciers melted under rising temperatures, there was more water in the air. Colder is generally drier, warmer wetter, although the world might not be all of those things everywhere under a changed climate. But where once there was periglacial tundra or cold desert, suddenly (geologically speaking) there was more warmth & lots of rain. These halcyon conditions lasted quite a while.
    The oldest human artifact in North America, a sandal, was found in Ft. Rock Cave, Oregon, which 11,000 years ago overlooked such a pluvial lake, rich in animal & vegetable foods, with high quality obsidian nearby for tools.
    But, yeah, sure, CO2 increased as the world warmed & the ice retreated, too.

  10. This study ignores the well established fact that precipitation increased worldwide. Ice cores from Greenland show it doubling at the beginning of the Holocene. The Gobi turned into a well watered plain, as did the Sahara, and the American west. It has all dried up since the end of the Climatic Optimum, because of the cooling for the last four millennia.

  11. And no, not the African Humid Period. It has been known as the Climatic Optimum or the Holocene Optimum and it was certainly worldwide, not confined to Africa. You have to wonder what cooks with these types. Is it ignorance?

  12. Wait a minute.
    “They focused their work on northern Africa (the present day Sahel region encompassing Niger, Chad, and also northern Nigeria)”
    That’s not northern Africa; that’s sub-Saharan Africa. Guess they skipped Geography.
    Best winter strawberries and mangoes I ever had (Jos and Yola, Nigeria).
    Are these real people or does the model spit out the authors too?

    • I spent 3 years headquartered in Jos with the Geological Survey of Nigeria in the middle-late 60s. Verdant, succulent produce on top of a plateau. Emerald green oranges with luscious orange flesh, I had ~30 big mango trees in my yard, and I found out why grapefruit are called grapefruit (I leave that for an exercise). But drop down from the plateau onto the Sahel proper in only a dozen miles or so, where the then British heads of the Survey directed my Canadian butt to map thousands of square miles of crackling hot dusty terrain and you see what a bit of topography can do for the climate. I also crossed the Benue R with my landrover on a rocking wooden motorless ferry that used inserted angled rudders pushed on by the current to propel it across. It had to be towed back upstream by laborers – my destination, Yola! Adventure, in addition to being caught in Nigeria’s civil war was climbing Wase Rock, a volcanic neck ~ 1000 feet high (a volcanic throat filled with lava which solidifies and over thousand of years the cinder cone is eroded away leaving the frozen tower. http://commons.wikimedia.org/wiki/File:Wase_Rock.JPG

      • mpainter
        December 4, 2014 at 9:04 pm
        “Gary,
        Interesting. How high was your plateau above the Sahel, generally?”
        It is about 1000m average above the plain. It rises abruptly from the plain ~800m and the access roads are switchback and a scary ascent with (at the time) just a gravel surface. A large bus or truck, wired together and with loads piled 3-4m above the roof or box of the truck and the ever-present passengers piled on top of that coming down the narrow roadway with hardly any brakes is an adventure I left out of my above narrative.

  13. By comparing the proxy records with the computer simulations, the study demonstrated that the climate model got the AHP right. This helps to validate its role in predicting how rising greenhouse gas concentrations might change rainfall patterns in a highly populated and vulnerable part of the world.
    Wow. The models can’t get the last 20 years right on a global basis, on a regional basis they are even worse, but they can pin down two areas of Africa from 15,000 years ago? And so should be trusted for future predictions?
    This isn’t even science by press release anymore. This is science by the Marketing Department.

  14. Don’t ya hate it when, the more you know the less you know.
    It’s like chaos, or something even more devilish.

  15. It is absolutely chaos – theory. These dynamical systems (climate) don’t lend themselves to easy linear predictions, but politicians require easy and some simple variable to hang the hat on.
    It’s not CO2.

    • Chaotic during interglacials but I don’t think so during the ice maxima.
      “Gary Pearse
      December 4, 2014 at 6:18 pm
      My response to rgb above:
      “……You have eloquently explored on a number of occasions the chaotic non-linear multi-coupled system comprising atmosphere, oceans, sun, affects of aerosols, clouds, radiation feedbacks, etc. I would suggest that this may be so EXCEPT during the development and growth of ice during the onset and quiet life of glacial periods. I think here we have a relatively boring, non-chaotic, simply coupled process that is easy to model. The questions we are having difficulty with are what conditions caused them to go into this state and what finally caused them to exit it after thousands of years. Milankovich? plus other things?”
      Moisture rises mainly in the tropical zone and travels poleward and falls as snow, over 50million km^2 of it during an ice age. A fairly linear process for the atmosphere – an air conditioner that we understand quite well. The warm periods may be chaotic but so what. SST max is 31C and this puts a cap on the warming. There is not such a benevolent cap on cooling of the oceans.

  16. A bit off topic, but I’m puzzled and was hoping someone could answer this.
    On this page http://www.ncdc.noaa.gov/temp-and-precip/national-temperature-index/time-series?datasets%5B%5D=uscrn&datasets%5B%5D=cmbushcn&parameter=anom-tavg&time_scale=p12&begyear=2005&endyear=2014&month=12
    We see that USCRN and USHCN coincide almost exactly.
    They are two very separate systems, aren’t they?
    In which case how is it possible to get such a match unless one is being massively manipulated?

  17. Another example of how the US Government spends annually $20 + billion dollars to “fight” climate change although the science is settled.

  18. Not one mention of the Indian Ocean.
    For us in Australia, what happens with the rainfall in Africa bordering the Indian Ocean is reflected in our rainfall, along with the other countries surrounding the I.O.
    Our existing knowledge of the Indian Ocean Dipole means that the African rainfall cannot be studied in isolation.

  19. You cannot present any valid physics which supports the hoax that greenhouse gases like water vapor and carbon dioxide warm planetary surfaces. They don’t: they cool by radiating thermal energy out of the atmosphere and thus helping to cool the nitrogen and oxygen molecules that make up over 98% of Earth’s atmosphere and which hold (or “trap”) 98% of the thermal energy in that atmosphere.
    Empirical studies of real world temperature data prove water vapour cools. It is well known that it reduces the temperature gradient (lapse rate) and so it could not raise the surface temperature whilst lowering the temperature gradient or there would be enormous radiative imbalance at the top of the atmosphere. Measurements of radiative balance virtually always show a mere ±0.5% difference between incident and outgoing radiative flux. The surface temperature is “propped up” by the gravity-induced temperature gradient, not by back radiation from a cooler troposphere.

    • Skeptical scientist says:
      “You cannot present any valid physics which supports the hoax that greenhouse gases like water vapor and carbon dioxide warm planetary surfaces. They don’t: they cool by radiating thermal energy out of the atmosphere…”
      Since you speak of planetary surfaces, let’s look at Venus. It’s proximity to the sun means sunlight at TOA is Approx. twice as strong as at Earth’s TOA, yet it has Approx. twice the albedo as Earth. Before measurements were possible it was thought that Venus surface temps were only slightly greater than Earth’s. If CO2 did cool the planetary surface, wouldn’t Venus, with an atmosphere over 95% CO2, be much cooler that the Earth?
      Here I am not supporting a strong positive GHG effect, as other factors do come into play, just saying radiative gases do not seem to effectively reduce average surface temps.
      I do say radiative gasses in Earth’s atmosphere reduce heat flow to and from the surface. That is, they cause the surface to heat more slowly during the day, and to cool more slowly at night. This is a valuable effect, look at the moon’s ~ 15C rise per hour after sunrise with the same Solar distance as the Earth.
      It is the reduced cooling rate at night that is the actual GHG warming effect. Note that the surface is not actually rising in temperature.
      The temperature influences due to CO2 are already in play. They change little with changes in CO2 concentration (which also changes very little), and are swamped by H2O, especially when considering H2O phase changes and cloud cover changes (pun intended).
      SR

  20. My studies indicate a cyclic pattern in African Rainfall. Durban in South Africa present a 66 year cycle [sub-multiples]; Mahalapye in Botswana presents a 60 year cycle [sub-multiples], Catuane in Mozambique presents a 54 year cycle [sub-multiple]. They all followed a typical pattern of WMWM —-. Sediment data studies showed a 66-year cycle pattern in Canberra in Australia. Ethiopia presented a different pattern starting from 22 year cycle at Asmara in Eritria [new country born from Ethiopia] — it is a sub-multiple in Durban precipitation. Jijiga in Ethiopia presented 28 years cycle — a bi-model rainfall zone. Coffee growing zone presents a 36 year cycle — border to Sudan.
    Dr. S. Jeevananda Reddy

  21. For the sake of argument I won’t question the accuracy of the models and the proxies.
    Accepting this study then tells us that increasing CO2 has an effect that is gradual over about 10,000 years.
    Can we adapt to that rate?

  22. There were lots of changes occurring on the earth during that time period as the earth continued to emerge from the previous ice age.
    But because allegedly there was a small change CO2 levels at the same time, everything else can be ignored because the magic of CO2 means that whatever happens, it is always responsible.

  23. So….climate change from colder to warmer put more water vapor in the air…which collided with cold fronts that were still coming down….which made more rain

  24. Nonsense. CO2 has nothing to do w/Saharan rainfall. It’s well known that it varies w/the earth’s orbital precession & whether the max solar insolation occurs during summer or winter. Summer max (like 10kya) = partial expansion of the ITCZ into the Sahara. Summer min (like now) = no expansion of ITCZ.

  25. Basic read to debunk this carbogarbage: Marcel Leroux PhD published as “The Meteorology and Climate of Tropical Africa” by Praxis/Springer

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