Solar panels all over the Sahara desert?

Solar panels all over the Sahara desert?

– Imagine newsletter #2

subscribe to the Imagine newsletter

Solar panels all over the Sahara desert? Asked Will de Freitas, Environment + Energy Editor, The Conversation, starting with:

You may have seen a variant of this meme before. A map of North Africa is shown, with a surprisingly small box somewhere in Libya or Algeria shaded in. An area of the Sahara this size, the caption will say, could power the entire world through solar energy:

Over the years various different schemes have been proposed for making this idea a reality. Though a company called Desertec caused a splash with some bold ideas a decade ago, it collapsed in 2014 and none of the other proposals to export serious amounts of electricity from the Sahara to Europe and beyond are anywhere close to being realised.

It’s still hard to store and transport that much electricity from such a remote place, for one thing, while those people who do live in the Sahara may object to their homeland being transformed into a solar superpower. In any case, turning one particular region into a global energy hub risks all sorts of geopolitical problems.

The Imagine newsletter aims to tackle these big “what if” questions, so we asked a number of academics to weigh in on the challenges of exploiting the cheapest form of electricity from perhaps the cheapest and best spot on Earth.

Sahara has huge energy potential

Amin Al-Habaibeh is an engineer at Nottingham Trent University who has researched various options for Saharan solar.

Read more: Should we turn the Sahara Desert into a huge solar farm?

He points to the sheer size and amount of sunshine the Sahara desert receives:

  • It’s larger than Brazil and slightly smaller than the US.
  • If every drop of sunshine that hits the Sahara was converted into energy, the desert would produce enough electricity over any given period to power Europe 7,000 times over.
Solar panels all over the Sahara desert?
Global horizontal irradiation, a measure of how much solar power is received per year. Global Solar Atlas/World Bank

So even a small chunk of the desert could indeed power much of the world, in theory. But how would this be achieved?

Al-Habaibeh points to two main technologies. Both have their pros and cons.

  • Concentrated solar power uses lenses or mirrors to focus the sun’s energy in one spot, which becomes incredibly hot. This heat then generates electricity through a steam turbine.
  • In this image the tower in the middle is the “receiver” which then feeds heat to a generator:
Solar panels all over the Sahara desert?
Aerial view of a large concentrated solar power plant. Novikov Aleksey/Shutterstock
  • Some systems store the heat in the form of molten salt. This means they can release energy overnight, when the sun isn’t shining, providing a 24h supply of electricity.
  • Concentrated solar power is very efficient in hot, dry environments, but the steam generators use lots of water.
  • Then there are regular photovoltaic solar panels. These are much more flexible and easier to set up, but less efficient in the very hottest weather.

Overall, Al-Habaibeh is positive:

Just a small portion of the Sahara could produce as much energy as the entire continent of Africa does at present. As solar technology improves, things will only get cheaper and more efficient. The Sahara may be inhospitable for most plants and animals, but it could bring sustainable energy to life across North Africa – and beyond.

Solar panels could have remarkable impact on the desert though

Installing mass amounts of solar panels in the Sahara could also have a remarkable impact on the desert itself.

The Sahara hasn’t always been dry and sandy. Indeed, archaeologists have found traces of human societies in the middle of the desert, along with prehistoric cave paintings of Savannah animals. Along with climate records, this suggests that just a few thousand years ago the “desert” was far greener than today.

Solar panels all over the Sahara desert?
Long-extinct elephants still remain carved into rocks in southern Algeria. Dmitry Pichugin / shutterstock

Alona Armstrong, an environmental science lecturer at Lancaster University, wrote about a fascinating study in 2018 that suggested massive renewable energy farms could make the Sahara green again.

Read more: Massive solar and wind farms could bring vegetation back to the Sahara

A team of scientists imagined building truly vast solar and wind farms, far larger than most countries, and simulated the impact they would have on the desert around them. They found that:

  • Solar panels reflect less heat back into space compared to sand.
  • This means the surface would warm, causing air to rise and form clouds.
  • This would mean more rainfall, especially in the Sahel region at the southern edge of the desert.
  • And more vegetation would grow, which would absorb more heat, drive more precipitation, and so on
  • It’s an example of a climate feedback.
Solar panels all over the Sahara desert?
Large-scale wind and solar would mean more new rain in some areas than others. Eviatar Bach, CC BY-SA

This may be a nice side effect of a huge Saharan solar plant, but it doesn’t necessarily mean it should happen. As Armstrong points out:

These areas may be sparsely populated but people do live there, their livelihoods are there, and the landscapes are of cultural value to them. Can the land really be “grabbed” to supply energy to Europe and the Middle East?

Solar panels all over the Sahara desert?
Ghardaia, Algeria. Even in the middle of the Sahara, there are settlements. Sergey-73/Shutterstock

Is this climate colonialism?

If we want to deploy millions of solar panels in the Sahara, then who is “we”? Who pays for it, who runs it and, crucially, who gets the cheap electricity?

This is what worries Olúfẹ́mi Táíwò, a philosopher who researches climate justice at Georgetown University. He mentions Saharan solar power as one of the possible policies involved in a Green New Deal, a wide-ranging plan to enact a “green transition” over the next decade.

Read more: How a Green New Deal could exploit developing countries

He points out that exports of solar power could: “Exacerbate what scholars like sociologist Doreen Martinez call climate colonialism – the domination of less powerful countries and peoples through initiatives meant to slow the pace of global warming.”

  • While Africa may have abundant energy resources, the continent is also home to the people who are the least connected to the grid.
  • Solar exports risk “bolstering European energy security … while millions of sub-Saharan Africans have no energy of their own.”

What if we’re looking at the wrong desert?

All of this will be moot if Saharan solar never actually happens. And Denes Csala, a lecturer in energy systems at Lancaster University, is sceptical.

Read more: Why the new ‘solar superpowers’ will probably be petro-states in the Gulf

It’s true that much of the world’s best solar resources are found in the desert. Here’s a graph from his PhD research which shows how Saharan nations dominate:

Solar panels all over the Sahara desert?
The sunniest tenth of the world is mostly Saharan countries … and Saudi Arabia. Denes Csala / NREL, Author provided

But Denes says that we’re looking at the wrong desert. In fact, the countries of the Arabian peninsula are better placed to exploit the sun. He argues several factors work in favour of Saudi Arabia, the UAE and co:

  • They have a history of exporting oil.
  • In the energy market, worries over security of supply means countries tend to do business with the same partners over time.
  • Ports, pipes and other infrastructure that have been built to ship oil and gas could be repurposed to ship solar energy as hydrogen.

[Energy security] would be the Achilles heel of a northern African energy project: the connections to Europe would likely be the continent’s single most important critical infrastructure and, considering the stability of the region, it is unlikely that European countries would take on such a risk.

It would be fair to say academics have mixed views about the idea of mass Saharan solar. While the energy potential is obvious, and most of the necessary technology already exists, in the long run it may prove too complicated politically.

Still think this is all fantasy?

Maybe Europeans should look closer to home. The UK Planning Inspectorate is currently examining the Cleve Hill solar farm proposal in Kent, which would involve installing nearly a million solar panels across a marshland site the size of 600 football pitches. To protect against flooding, the panels would be mounted several metres in the air. If built, despite opposition from locals and conservationists, Cleve Hill would be by far the country’s largest solar farm and about the same size as Europe’s largest, near Bordeaux.

Alastair Buckley from the University of Sheffield points out the project would be groundbreaking as, unlike other ventures of this kind, it doesn’t rely on subsidies. With solar power getting ever cheaper, Cleve Hill – if it happens – seems to mark the moment when solar may start paying for itself – even far from the world’s deserts.

Further reading

What is Imagine?

Subscribe to the newsletter Imagine.

Imagine is a newsletter from The Conversation that presents a vision of a world acting on climate change. Drawing on the collective wisdom of academics in fields from anthropology and zoology to technology and psychology, it investigates the many ways life on Earth could be made fairer and more fulfilling by taking radical action on climate change. You are currently reading the web version of the newsletter.

Here’s the more elegant email-optimised version subscribers receive. To get Imagine delivered straight to your inbox, subscribe now.

Click here to subscribe to Imagine. Climate change is inevitable. Our response to it isn’t.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

The Conversation

Why the new ‘solar superpowers’ will probably be petro-states in the Gulf

Why the new ‘solar superpowers’ will probably be petro-states in the Gulf

Why the new ‘solar superpowers’ will probably be petro-states in the Gulf and not those countries of North Africa? Why indeed; here is Dénes Csala, Lancaster University‘s opinion.

File 20190430 136794 45bqac.jpg?ixlib=rb 1.1

capitanoproductions / Shutterstock

Every now and then, the idea of powering Europe using the vast solar resources of the Sahara Desert comes up. Were this to actually happen, we may witness the rise of new energy superpowers in Northern Africa. But a look at the economic and political energy system suggests what’s more likely is the oil-rich countries of the Arabian (or Persian) Gulf will continue to dominate energy trade even in the post-fossil era.

Renewable energy, of course, is very location dependent – the sunnier a place is, the more energy you get out of photovoltaic panels. Over the course of a year, southern Algeria, for example, gets more than twice as much solar energy as southern England. The graph below, which I put together as part of my PhD, shows that some of the best solar resources in the world are indeed found in Algeria, Libya, Egypt, Niger, Chad and Sudan.

Russia and Canada have lots of low-solar land, but the most sunny areas are elsewhere. Denes Csala / NREL, Author provided

So, one could build large Saharan solar farms and then transmit the power back to densely populated areas of Europe. Such a project would need to overcome various technical challenges, but we can say that in theory it is possible, even if not practical.

Yet plans to actually set up mass Saharan solar have floundered. The most notable project, Desertec, was fairly active until the mid 2010s, when a collapse in the price of oil and natural gas made its business case more difficult. At that time, the major technology considered was concentrated solar power, where you use the heat from the sun to run a steam turbine. Energy can be stored as heat overnight, therefore enabling uninterrupted energy supply and making it preferred to then expensive batteries.

Solar is getting cheaper and cheaper. Nature

Since then, however, the cost of both solar panels and battery storage have dropped drastically. But, while conditions might look favourable for Saharan solar, it is unlikely that new solar energy kingpins will arise in North Africa. Instead, we should look one desert further to the East – the Rub al Khali on the Arabian peninsula, the home of the reigning energy powers.

Sun shines on the Gulf

The economies of the United Arab Emirates, Saudi Arabia, Qatar and the other Gulf nations are built around energy exports. And as climate change imposes pressure on the extraction of fossil fuels, these countries will have to look for alternative energy (and income) sources in order to keep their economies afloat. The International Renewable Energy Agency set up its headquarters in Abu Dhabi, and the region has no shortage of ambitious solar projects promising extremely cheap electricity. However only a small amount of capacity has actually been deployed so far. Low oil revenues have not helped with the megaprojects.


Countries in the Sahara also have little history of trading fossil fuels, outside of Libya and Algeria, while things are rather different for the petro-states of the Gulf. And this matters because, in the energy business, worries over longer-term security of supply mean countries tend to trade with the same partners.

This would be the Achilles’ heel of a Northern African energy project: the connections to Europe would likely be the continent’s single most important critical infrastructure and, considering the stability of the region, it is unlikely that European countries would take on such a risk.

Which brings us to an alternative way to transmit energy: hydrogen. A process called electrolysis can use renewable electricity to split water into hydrogen and oxygen, and the resulting hydrogen can store lots of energy. Soon it will become feasible to move energy around the world in this form, using shipping infrastructure similar to that already in use today for liquefied natural gas.

Sure, there are disadvantages compared to batteries. It would mean introducing two more conversion stages and thus reduced efficiency (30% roundtrip efficiency compared to 80% for batteries), but it would overcome the distance barrier. And perhaps just as importantly: shipping energy by hydrogen would mean no significant change to the existing maritime trade infrastructure, which will hand an advantage to established energy exporters.

If this means the Sahara is unlikely to develop renewable energy superpowers, then perhaps this is for the better. With the booming populations of Sub-Saharan Africa in dire need of electrification, clean solar power might be better used to alleviate the energy crisis in somewhere like Nigeria rather than sent to Europe. While these countries may eventually be able to shake off any solar resource curse, in the short term, exports like these could just look like yet another European attempt to extract natural resources from Africans.

Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.The Conversation

Dénes Csala, Lecturer in Energy Storage Systems Dynamics, Lancaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Investment in Renewables now led by Developing Countries

Investment in Renewables now led by Developing Countries

Populations increases amongst many other things in all developing countries are turning these to be the largest source of energy demand, to the point of overtaking all developed countries in terms of growth. As a consequence, investment in renewables now led by developing countries is showing the way.

Scientific American Observations article by Riccardo Puliti,
Director for Energy and Extractives at the World Bank and Morgan D. Bazilian, Professor of Public Policy and Executive Director, were posted on April 25, 2019. Here there are.

How a Key Energy Technology Can Help Developing Countries

The World Bank has a new program for financing the advanced battery storage systems essential for making wind and solar power work.

How a Key Energy Technology Can Help Developing Countries
Artist’s rendering of a battery backup system for storage of renewable energy. Credit: Getty Images

A global energy transition is under way. Its potential to redraw the landscape will be most profoundly felt in developing economies. These economies will be the key locations of growth and investment. Developing countries have already become the largest absolute source of energy demand, and they are far outpacing OECD countries in terms of growth. Similarly, investment in renewables is now also led by developing countries. Sub-Saharan Africa, home to a majority of the world’s population living with limited, poor quality or no electricity, will likely witness some of the most significant of these transformations.

What we can safely guess about the changing system is that it will include a large role for batteries for both electric vehicles and power storage. How governments respond will be essential, and the World Bank is responding with a focused, first-of-its-kind program to help.

The global energy storage (excluding pumped hydro) market is forecast to attract over $600 billion in investment over the next 20 years. Bloomberg New Energy Finance sees the market for both utility scale and “behind-the-meter” (on-site at businesses, industrial facilities, and homes) growing exponentially to reach about 7 percent of total installed capacity by 2040. This battery revolution is happening all over the world, and its rapid growth is due to both falling prices, and the many benefits to the electricity system, ranging from helping shift demand to enabling the integration of solar power to improving reliability.  

The solar revolution has already had an impact. Many countries in Africa are rapidly deploying centralized, utility-scale systems, as well as decentralized, smaller systems that can power homes and businesses. These decisions are motivated by economics. The price of photovoltaics (PVs) has dropped roughly 80 percent over the last decade. Batteries can be deployed quickly and offer modularity—both very attractive qualities to the region.

As an example, countries in the Sahel such as Burkina Faso and Mali are developing regional solar parks that will serve as demonstration projects for other countries in West Africa. And the focus is not limited to residential uses. A priority is to power local agricultural processing, irrigation and light industry. A shift to a low-carbon and more secure energy future, lower operating costs and strengthening grids has multiple benefits to these countries ranging from economic and social development to security. Well-designed regulations are fundamental to realizing these benefits, and to ensuring they are realized in developing countries.

Battery storage systems are delivering reliable power at roughly a third of the cost of diesel generators, and have better supply chain resilience. There are other benefits as well: poor-quality and adulterated diesel is highly polluting and linked to major health impacts across the continent. The selling of diesel is also often tied with organized crime; consumers can pay even higher prices for fuel in poor communities where there is little monitoring.

Storage comes in many varieties. Energy storage can complement and, in some cases, replace transmission infrastructure projects, as well as diesel generators and gas power plants. Pumped storage has been in use for decades, but it is battery storage that is receiving the lion’s share of attention now as costs come down and technologies proliferate. The International Energy Agency (IEA), in its World Energy Outlook 2018, included for the first time the contribution of batteries to flexibility of power systems. By 2040 the IEA foresees a hundredfold increase in grid-connected battery additions compared to today.

Battery storage systems have already proven cost-effective in balancing supply and demand on a timescale of seconds. As a result, frequency swings are limited, there are fewer blackouts, operating costs go down, and system stability is enhanced for the benefit of all customers. In South Africa, the national utility Eskom is focused on developing battery storage capacity (the largest in the region) that will be used to enable the integration of current and future variable renewable energy capacity. The Gambia and the Central African Republic are looking to battery storage to help stabilize their fragile grids.

The coming boom in batteries promises another range of benefits, if managed right. Demand for the metals and minerals that are critical components in these next-generation batteries (such as cathode materials like lithium, nickel, manganese and cobalt) is expected to grow very fast—in some cases by almost tenfold by 2050—and large deposits of some of these are found in African countries. One of the largest challenges of Africa’s energy transition will be ensuring that the governance and management of extractive industries be strengthened so that the benefits of this coming boom are enjoyed by Africans, and that issues of sustainability and labor conditions in supply chains are addressed.

Last autumn, the World Bank Group committed $1 billion for a program to accelerate investments in battery storage in developing countries. Associated with this program is a new international partnership to help expand the use of energy storage and bring new technologies to developing countries’ power systems.

Recognizing the need to sustainably scale up the deployment of energy storage in developing countries and the significant opportunity that storage brings for increasing access to electricity and integrating more renewable energy, the Energy Storage Partnership (ESP) will foster international cooperation on: Technology Research Development & Demonstration, System Integration, and Policies and Regulations to help develop energy storage solutions tailored to the needs of developing countries.

To date, the investments have been small in scale, but significant in the nascent market. Globally, the bank has financed roughly 15 percent of the stationary battery storage capacity that is already deployed or currently under development—mostly through mini-grid projects and in island states to improve resilience. But now larger projects are being developed. For example, in Mali and Burkina Faso the bank is developing the largest solar parks in the region with PV-battery systems. These projects will combine standard tenders and de-risking instruments to attract private developers. 

In some ways, the pace of the energy transition will be set by developing countries. So far, grid-scale battery technologies have been deployed primarily in OECD countries, but by sharing the lessons learned and showing the benefits of battery storage, this new solution should be a foundation of economic growth in the Global South.

The views expressed are those of the author(s) and are not necessarily those of Scientific American.

About the authors:

Riccardo Puliti is Senior Director for Energy and Extractives at the World Bank.

Morgan D. Bazilian is a Professor of Public Policy and Executive Director of the Payne Institute at the Colorado School of Mines. He is an affiliated faculty member with Mines’ Space Resources program, which just started offering a first-of-a-kind PhD in Space Resources.

newsletter promo

Sign up for Scientific American’s free newsletters.
Should we turn the Sahara Desert into a huge solar farm?

Should we turn the Sahara Desert into a huge solar farm?

Amin Al-Habaibeh, Nottingham Trent University

Whenever I visit the Sahara I am struck by how sunny and hot it is and how clear the sky can be. Aside from a few oases there is little vegetation, and most of the world’s largest desert is covered with rocks, sand and sand dunes. The Saharan sun is powerful enough to provide Earth with significant solar energy.

The statistics are mind-boggling. If the desert were a country, it would be fifth biggest in the world – it’s larger than Brazil and slightly smaller than China and the US. Each square metre receives, on average, between 2,000 and 3,000 kilowatt hours of solar energy per year, according to NASA estimates. Given the Sahara covers about 9m km², that means the total energy available – that is, if every inch of the desert soaked up every drop of the sun’s energy – is more than 22 billion gigawatt hours (GWh) a year.

This is again a big number that requires some context: it means that a hypothetical solar farm that covered the entire desert would produce 2,000 times more energy than even the largest power stations in the world, which generate barely 100,000 GWh a year. In fact, its output would be equivalent to more than 36 billion barrels of oil per day – that’s around five barrels per person per day. In this scenario, the Sahara could potentially produce more than seven times the electricity requirements of Europe, with almost no carbon emissions.

Global horizontal irradiation, a measure of how much solar power received per year.
Global Solar Atlas / World Bank

What’s more, the Sahara also has the advantage of being very close to Europe. The shortest distance between North Africa and Europe is just 15km at the Strait of Gibraltar. But even much further distances, across the main width of the Mediterranean, are perfectly practical – after all, the world’s longest underwater power cable runs for nearly 600km between Norway and the Netherlands.

Over the past decade or so, scientists (including me and my colleagues) have looked at how desert solar could meet increasing local energy demand and eventually power Europe too – and how this might work in practice. And these academic insights have been translated in serious plans. The highest profile attempt was Desertec, a project announced in 2009 that quickly acquired lots of funding from various banks and energy firms before largely collapsing when most investors pulled out five years later, citing high costs. Such projects are held back by a variety of political, commercial and social factors, including a lack of rapid development in the region.

The planet Tatooine from the Star Wars movies was filmed in southern Tunisia.
Amin Al-Habaibeh, Author provided

More recent proposals include the TuNur project in Tunisia, which aims to power more than 2m European homes, or the Noor Complex Solar Power Plant in Morocco which also aims to export energy to Europe.

Two technologies

There are two practical technologies at the moment to generate solar electricity within this context: concentrated solar power (CSP) and regular photovoltaic solar panels. Each has its pros and cons.

Concentrated solar power uses lenses or mirrors to focus the sun’s energy in one spot, which becomes incredibly hot. This heat then generates electricity through conventional steam turbines. Some systems use molten salt to store energy, allowing electricity to also be produced at night.

A concentrated solar plant near Seville, Spain. The mirrors focus the sun’s energy on the tower in the centre.
Novikov Aleksey / shutterstock

CSP seems to be more suitable to the Sahara due to the direct sun, lack of clouds and high temperatures which makes it more efficient. However the lenses and mirrors could be covered by sand storms, while the turbine and steam heating systems remain complex technologies. But the most important drawback of the technology is its use of scarce water resources.

Photovoltaic solar panels instead convert the sun’s energy to electricity directly using semiconductors. It is the most common type of solar power as it can be either connected to the grid or distributed for small-scale use on individual buildings. Also, it provides reasonable output in cloudy weather.

But one of the drawbacks is that when the panels get too hot their efficiency drops. This isn’t ideal in a part of the world where summer temperatures can easily exceed 45℃ in the shade, and given that demand for energy for air conditioning is strongest during the hottest parts of the day. Another problem is that sand storms could cover the panels, further reducing their efficiency.

Both technologies might need some amount of water to clean the mirrors and panels depending on the weather, which also makes water an important factor to consider. Most researchers suggest integrating the two main technologies to develop a hybrid system.

Just a small portion of the Sahara could produce as much energy as the entire continent of Africa does at present. As solar technology improves, things will only get cheaper and more efficient. The Sahara may be inhospitable for most plants and animals, but it could bring sustainable energy to life across North Africa – and beyond.

Click here to subscribe to our climate action newsletter. Climate change is inevitable. Our response to it isn’t.The Conversation

Amin Al-Habaibeh, Professor of Intelligent Engineering Systems, Nottingham Trent University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Sahara Desert once verdant oasis

Sahara Desert once verdant oasis

The Sahara Desert is one of the harshest, most inhospitable places on the planet, covering much of North Africa in some 3.6 million square miles of rock and windswept dunes. But it wasn’t always so desolate and parched. Primitive rock paintings and fossils excavated from the region suggest that the Sahara was once a relatively verdant oasis, where human settlements and a diversity of plants and animals thrived.  

This January 2, 2019 essay by Jennifer Chu, of Massachusetts Institute of Technology does encapsulate climate evolution through time, and not its undeniable change.

Study shows the Sahara swung between lush and desert conditions every 20,000 years, in sync with monsoon activity

A new analysis of African dust reveals the Sahara swung between green and desert conditions every 20,000 years, in sync with changes in the Earth’s tilt. Credit: Massachusetts Institute of Technology

A new analysis of African dust reveals the Sahara swung between green and desert conditions every 20,000 years, in sync with changes in the Earth’s tilt. Credit: Massachusetts Institute of Technology

Now researchers at MIT have analyzed dust deposited off the coast of west Africa over the last 240,000 years, and found that the Sahara, and North Africa in general, has swung between wet and dry climates every 20,000 years. They say that this climatic pendulum is mainly driven by changes to the Earth’s axis as the planet orbits the sun, which in turn affect the distribution of sunlight between seasons—every 20,000 years, the Earth swings from more sunlight in summer to less, and back again.

For North Africa, it is likely that, when the Earth is tilted to receive maximum summer sunlight with each orbit around the sun, this increased solar flux intensifies the region’s monsoon activity, which in turn makes for a wetter, “greener” Sahara. When the planet’s axis swings toward an angle that reduces the amount of incoming summer sunlight, monsoon activity weakens, producing a drier climate similar to what we see today.

“Our results suggest the story of North African climate is dominantly this 20,000-year beat, going back and forth between a green and dry Sahara,” says David McGee, an associate professor in MIT’s Department of Earth, Atmospheric and Planetary Sciences. “We feel this is a useful time series to examine in order to understand the history of the Sahara desert and what times could have been good for humans to settle the Sahara desert and cross it to disperse out of Africa, versus times that would be inhospitable like today.”

McGee and his colleagues have published their results today in Science Advances.

A puzzling pattern

Each year, winds from the northeast sweep up hundreds of millions of tons of Saharan dust, depositing much of this sediment into the Atlantic Ocean, off the coast of West Africa. Layers of this dust, built up over hundreds of thousands of years, can serve as a geologic chronicle of North Africa’s climate history: Layers thick with dust may indicate arid periods, whereas those containing less dust may signal wetter eras.

Scientists have analyzed sediment cores dug up from the ocean bottom off the coast of West Africa, for clues to the Sahara’s climate history. These cores contain layers of ancient sediment deposited over millions of years. Each layer can contain traces of Saharan dust as well as the remains of life forms, such as the tiny shells of plankton.

Past analyses of these sediment cores have unearthed a puzzling pattern: It would appear that the Sahara shifts between wet and dry periods every 100,000 years—a geologic beat that scientists have linked to the Earth’s ice age cycles, which seem to also come and go every 100,000 years. Layers with a larger fraction of dust seem to coincide with periods when the Earth is covered in ice, whereas less dusty layers appear during interglacial periods, such as today, when ice has largely receded.

But McGee says this interpretation of the sediment cores chafes against climate models, which show that Saharan climate should be driven by the region’s monsoon season, the strength of which is determined by the tilt of the Earth’s axis and the amount of sunlight that can fuel monsoons in the summer.

“We were puzzled by the fact that this 20,000-year beat of local summer insolation seems like it should be the dominant thing controlling monsoon strength, and yet in dust records you see ice age cycles of 100,000 years,” McGee says.

Beats in sync

To get to the bottom of this contradiction, the researchers used their own techniques to analyze a sediment core obtained off the coast of West Africa by colleagues from the University of Bordeaux—which was drilled only a few kilometers from cores in which others had previously identified a 100,000-year pattern.

The researchers, led by first author Charlotte Skonieczny, a former MIT postdoc and now a professor at Paris-Sud University, examined layers of sediment deposited over the last 240,000 years. They analyzed each layer for traces of dust and measured the concentrations of a rare isotope of thorium, to determine how rapidly dust was accumulating on the seafloor.

Thorium is produced at a constant rate in the ocean by very small amounts of radioactive uranium dissolved in seawater, and it quickly attaches itself to sinking sediments. As a result, scientists can use the concentration of thorium in the sediments to determine how quickly dust and other sediments were accumulating on the seafloor in the past: During times of slow accumulation, thorium is more concentrated, while at times of rapid accumulation, thorium is diluted. The pattern that emerged was very different from what others had found in the same sediment cores.

“What we found was that some of the peaks of dust in the cores were due to increases in dust deposition in the ocean, but other peaks were simply because of carbonate dissolution and the fact that during ice ages, in this region of the ocean, the ocean was more acidic and corrosive to calcium carbonate,” McGee says. “It might look like there’s more dust deposited in the ocean, when really, there isn’t.”

Once the researchers removed this confounding effect, they found that what emerged was primarily a new “beat,” in which the Sahara vacillated between wet and dry climates every 20,000 years, in sync with the region’s monsoon activity and the periodic tilting of the Earth.

“We can now produce a record that sees through the biases of these older records, and so doing, tells a different story,” McGee says. “We’ve assumed that ice ages have been the key thing in making the Sahara dry versus wet. Now we show that it’s primarily these cyclic changes in Earth’s orbit that have driven wet versus dry periods. It seems like such an impenetrable, inhospitable landscape, and yet it’s come and gone many times, and shifted between grasslands and a much wetter environment, and back to dry climates, even over the last quarter million years.”

Explore further: Scientists find huge reduction in African dust plume led to more Saharan monsoons 11,000 years ago

More information: “Monsoon-driven Saharan dust variability over the past 240,000 years” Science Advances (2019).

Read more at:

Research points to abrupt and widespread climate shift in the Sahara 5,000 years ago

Problématique de la Sécurité du Maghreb

Problématique de la Sécurité du Maghreb

Cette présente contribution est une synthèse de mes différentes contributions et interventions internationales entre 2010 et 2014,  posant la Problématique de la Sécurité du Maghreb tributaire d’un développement harmonieux,  face aux enjeux géostratégiques .   Car la récupération récente de missiles Stinger de courte portée, 4 800 mètres en altitude destinés à la destruction des aéronefs, avions et hélicoptères souvent  portées par un seul individu. à El-Oued par les forces armées en Algérie met  la problématique de l’insécurité des frontières au premier plan.

Enjeux géostratégiques et tensions sécuritaires aux frontières du Maghreb    

Par le Professeur des Universités,  Expert International en management stratégique,  Dr Abderrahmane MEBTOUL


1.-  Privilégiant en premier lieu ses intérêts stratégiques propres, partie prenante du dialogue méditerranéen (DM), le Maghreb  doit   agir  en fonction d’un certain nombre de principes et à partir d’une volonté avérée de contribuer à la promotion de la sécurité et de stabilité dans la région. C’est que la  fin de la guerre froide marquée par l’effondrement du bloc soviétique et les attentats survenus aux Etats-Unis le 11 septembre 2001 représente  un tournant capital dans l’histoire contemporaine. Le premier événement marque la fin d’un monde né un demi siècle plutôt et la dislocation d’une architecture internationale qui s’est traduite des décennies durant par les divisions, les déchirements et les guerres que nous savons.  Aujourd’hui, les menaces sur la sécurité ont pour nom terrorisme, prolifération des armes de destruction massive, crises régionales et  délitement de certains Etats. Or,  les défis collectifs nouveaux, sont une autre source de menace : ils concernent les ressources hydriques, la pauvreté, les épidémies, l’environnement. Ils sont d’ordre local, régional et global. Entre la lointaine et très présente Amérique et la proche et bien lointaine Europe, entre une stratégie globale et hégémonique, qui possède tous les moyens de sa mise en œuvre et de sa projection, et une stratégie à vocation globale qui se construit laborieusement et qui peine à s’autonomiser et à se projeter dans son environnement géopolitique immédiat, quelle attitude adopter et quels choix faire pour  le Maghreb  ? Interpellée et sollicitée, le Maghreb   s’interroge légitimement sur le rôle, la place ou l’intérêt que telle option ou tel cadre lui réserve ou lui offre, qu’il s’agisse du  dialogue méditerranéen de l’Otan ou du partenariat euro- méditerranéen, dans sa dimension tant économique que sécuritaire.  L’adaptation étant la clef de la survie et le pragmatisme un outil éminemment moderne de gestion des relations avec autrui, le Maghreb   dont son devenir segment de l’Afrique Nord, le   Maghreb, pont entre l’Europe et l’Afrique   doit   faire que celui que commandent la raison et ses intérêts.

2.- Le Maghreb  est confronté actuellement à  la sécurité dans la zone sahélo-saharienne, les tensions géostratégiques au Moyen Orient ( Irak, Syrie)  risquant de se déplacer en Afrique du Nord, du fait e rivalités des grandes puissance rentrant dans le cadre d’une recomposition politique et économique au niveau de la région.  Nous avons assisté dans la région à de profondes  mutations de la géopolitique saharienne après l’effondrement du régime libyen, avec  des   conséquences pour la région. . Bien avant et surtout depuis la  chute du régime  de Kadhafi  le Sahel est l’un de ces espaces échappant à toute autorité centrale, où se sont installés groupes armés et contrebandiers. Khadafi disparu des armes, dont 15 000 missiles sol-air étaient dans les entrepôts de l’armée libyenne dont une partie a été accaparé par de différents groupes qui opèrent au Sahel. Dès lors la sécurité   est posée à ses frontières occasionnant  d’importantes dépenses militaires impliquant une coordination entre les pays du Maghreb  pour minimiser les coûts en les mutualisant ,  sans compter des dépenses pour l’adaptation du renseignement  aux nouvelles mutations tant internes que mondiales de ses forces  de sécurité, dépenses  soustraites à des fins de développement . Il s’agit également   de penser à  la cybercriminalité enjeu du XXIème siècle.  Bien que le risque  des cyber-attaques  est actuellement minime, mais devant préparer l’avenir,  car les services électroniques sont à l’état primaire  (e-commerce, e-santé et e-administration) au Maghreb  et les entreprises et administrations maghrébines   fonctionnent  sur des modes de gestion désuètes n’étant pas orientées  vers les transactions  et services électroniques.  L’analyse par le professeur en stratégie  à Harvard  Michael Porter des « cinq forces »,  qui déterminent la structure concurrentielle d’une industrie de biens ou de services , le pouvoir de négociation des clients, le pouvoir de négociation des fournisseurs, la menace des produits ou services de substitution, la menace d’entrants potentiels sur le marché et l’intensité de la rivalité entre les concurrents,   fait apparaître que souvent les différents acteurs maghrébins  un faible pouvoir de négociation du fournisseur et un fort pouvoir de négociation du client, alors que les barrières d’entrées sur le marché maghrébin  tant des entreprises économiques que de l’armement sont élevées (1).

3.-  La  lutte contre le terrorisme implique de mettre fin à cette inégalité tant  planétaire qu’au sein des Etats où une minorité s’accapare une fraction croissante du revenu national enfantant la misère et donc le terrorisme, renvoyant à la moralité de ceux qui dirigent la Cité. Le tout  sécuritaire pour le sécuritaire a des limites,  existant des liens dialectiques entre développement et sécurité,  une  sécurité efficace  devant impliquer toute la population et une coopération internationale notamment Europe/Maghreb (1) afin d’éviter cette immigration massive qui constitue actuellement un drame humanitaire. Je suis convaincu que le XXIème siècle sera culturel ou ne le sera pas, ce qui serait préjudiciable à l’ensemble de l’humanité. L’élément inter-culturalité est la base des échanges, par le combat, contre toute forme de racisme et de diktat de la pensée unique, signe le plus évident de décadence de toute société, nécessitant  un renouveau culturel pour véhiculer le nouveau mode de pensée fondée sur la tolérance et contre toute forme de racisme afin de favoriser la symbiose des cultures de l’Orient et de  l’Occident.   Aussi, cela   implique  surtout de s’attaquer à l’essence ( un co-développement) et non aux apparences comme le montre  une  étude du Forum économique mondial (WEF) du 14 novembre 2013.  Aussi l’efficacité sécuritaire  devra  s’insérer  dans le cadre d’une vision  stratégique.  Face à un monde en perpétuel mouvement, tant en matière de politique étrangère, économique  que de défense, actions liées,  avec  les  derniers événements au Sahel, aux frontières du Maghreb,  se posent  l’urgence des stratégies d’adaptation et d’une coordination, internationale et  régionale afin d’agir efficacement sur les événements majeurs.  Ces nouveaux défis pour le Maghreb,  sous-segment du continent Afrique,  dépassent en importance et en ampleur les défis que le Maghreb   a eu à relever jusqu’à présent.   

(1)-Etude du professeur Abderrahmane MEBTOUL  parue à l’Institut Français des Relations Internationales (IFRI Paris France) » la coopération Maghreb Europe face aux enjeux géostratégiques » (novembre 2011)- chapitre III- « la stratégie de l’OTAN face aux enjeux géostratégiques en Méditerranée »Ouvrage collectif « le Maghreb face aux enjeux géostratégiques » sous la direction du professeur Abderrahmane Mebtoul  et  du Docteur Camille Sari de la Sorbonne ( Paris) deux tomes ( 1050 pages) Edition Harmattan paris 2015 avec la collaboration  de 36 experts internationaux et professeurs du Maghreb et de l’Europe ( économistes, sociologues, juristes, historiens,  sociologues, officiers militaires)