The Sahara is shrinking (not expanding)

Dr. Stefan Kröpelin is an award-wining geologist and climate researcher at the University of Cologne. He specializes in the eastern Sahara desert, specifically its climatic history, and has been active out in the field for more than 40 years.

Contrary to other evidence that the Sahara suddenly changed from a wet to dry climate 5,000 years ago, Kröpelin's core samples at Lake Yoa in northern Chad suggests the transition took longer, some 3,000 years from 5,600 to 2,700 BC[1].

In an interview, given on November 9, 2023, Dr. Kröpelin confronts the alarmist claim of expanding desertification and looming climate ‘tipping points’.

He states that even back in late-1980s rains had begun spreading into northern Sudan, with the rains increasing ever since leading to a vegetation spread northwards and the emergence of a trend: “The desert is shrinking; it is not growing.”

When the last glacial period ended some 12,000 years ago, explains Kröpelin, the eastern Sahara turned green with vegetation, it teemed with wildlife, and also had numerous bodies of water even as recently as 5,000 years ago.

"The most important studies that we conducted all show that after the ice age, when global temperatures rose, the Sahara greened … the monsoon rains increased, the ground water levels rose."

This all led to vegetation and wildlife thriving, but then over the past few thousands of years, the region dried out. It didn’t happen all of a sudden like climate models suggest, Kröpelin stresses.

When asked about dramatic tipping points, such as those claimed by the Potsdam Institute (PIK), Kröpelin says he is very skeptical when it come to 'crisis scenarios' 'such as those proposed by former PIK head, Hans-Joachim Schellnhuber, saying people making such claims "never did any studies themselves in any climate zone on the earth and they don’t understand how complex climate change is."

Barring catastrophic geological events, "it’s not how nature works," says Kröpelin. "Things change gradually."

The claims that "we have to be careful that things don’t get half a degree warmer, otherwise everything will collapse, is of course complete nonsense … I would say this concept [tipping points] is baseless."

Anyone who approaches the climate with control technology terms (feedbacks, negative feedbacks, trigger points, tipping points) has not understood something essential: Nature does not work with controlled variables, control algorithms or manipulated variables because it neither measures anything, sets anything nor uses algorithms. Everything that takes place in nature and in the entire universe are balancing processes.

[1] Francus et al: Varved sediments of Lake Yoa (Ounianga Kebir, Chad) reveal progressive drying of the Sahara during the last 6100 years in Sedimentology - 2013

Air Pollution and Antibiotic Resistance

Air pollution can be measured in Particle Matter (or PM), which is the term for a mixture of solid particles and liquid droplets found in the air. Some of these particles are dust, dirt, soot, or smoke. But PM's can also carry potentially harmful bacteria, viruses and fungal spores over large distances.

Now, research seems to indicate that PM_2.5 (2.5 micrometers and smaller) has diverse elements of antibiotic resistance that increase its spread after inhalation[1]. Antibiotic resistance is a constantly increasing global issue, causing millions of deaths worldwide every year.

PM _2.5 carries abundant antibiotic resistance-determinant genes. These levels are higher than what is found in sediments, soil, rivers and some engineering treatment systems. Humans are potentially directly exposed to antibiotic-resistant elements while inhaling air pollutants. The daily intake of antibiotic-resistant genes through inhalation exceeds what you would through drinking water.

Analysis suggests that environmental dissemination of antibiotic resistance genes (ARG's), particularly via airborne fine particle, the PM _2.5, may be partly to blame for the highest levels of antibiotic resistance and premature death in population-dense India and China.

With every one per cent rise in PM _2.5 pollution, there is an increase in antibiotic resistance between 0.5 and 1.9 per cent, depending on the pathogen. The analysis indicates antibiotic resistance resulting from air pollution is linked to an estimated 480,000 premature deaths in 2018.

Also, the continued overuse of antibiotics in humans and animals exacerbates the emergence of antibiotic-resistant elements, which can be primarily discharged into environment via waste water, agricultural manure application, or evaporation. Often, these antibiotic-resistant elements can be transferred from environmental micro-organisms to human pathogens through drinking water, food and air inhalation. The pollution can cross regional boundaries and spread antibiotic resistance over long distances and on a large scale, which could be a crucial link between the dissemination of environmental and human antibiotic resistance.

Zhou et al: Association between particulate matter (PM)_2.5 air pollution and clinical antibiotic resistance: a global analysis in Lancet Global Health – 2023.

Duststorms blanket Beijing

Om March 22, 2023, a severe duststorm has swept across Beijing and several northern provinces in China, blanketing the region in thick clouds of orange dust and sending air pollution soaring to hazardous levels, state weather authorities reported. The dust even turned the sun blue, a phenomenon called 'Mie scattering'.

The current duststorm originated from Mongolia and gradually moved towards central and eastern China, according to Chinese weather forecasters. A lack of rainfall and low pressure winds also meant small dust particles have also drifted into the country.

Dense clouds enveloped the Chinese capital where the air quality index of PM10 – particles of pollution that are less than 10 micrometers in diameter and can enter through the nose and travel to the lungs – have exceeded monitoring charts.

Concentrations of PM10 particles hit 1,667 micrograms per cubic meter by 06:00 hours local time, according to Beijing’s monitoring center, with the agency calling it “the most severe sandstorm to date this year.”

That figure is more than 37 times the daily average guideline of 45 micrograms per cubic meter set by the World Health Organization.

Beijing is regularly hit with duststorms in the spring with the smog made worse by rising industrial activities and rapid deforestation throughout northern China.

Nearly a dozen provinces issued 'yellow' warning signals, including Shaanxi, Shanxi, Hebei, Heilongjiang, Jilin, Liaoning, Shandong, Henan, Jiangsu, Anhui and Hubei, according to China’s Meteorological Administration.

China uses a four-tier weather warning system, with 'red' representing the most severe warning, followed by 'orange', 'yellow' and 'blue'.

Which means that everybody is cheating. Which, of course, is nothing new in a communist country where every official may be held accountable if 'the party' disagrees. If a duststorm that exceeds every guideline is 'just' yellow, one wonders how severe a duststorm must be to achieve a 'red' status.

India gets colder (and hotter)

While India has seen a number of record-breaking warm spells in the recent decades, there have also been a number of record-breaking cold waves in the country, despite mumblings about global warming.

The analysis, led by Raju Mandal and Susmitha Joseph, scientist of the Indian Institute of Tropical Meteorology (IITM), took into account the number of cold wave events in the last seven decades, from 1951 to 2022[1]. They found that more cold wave days were observed in the recent decades compared to the previous ones.

“In the recent decade, more cold wave days have been observed across the central and eastern parts,” Mandal explained: “In Madhya Pradesh, Jharkhand, Vidarbha, Marathwada, Uttar Pradesh, Bihar and also some areas of northwest India such as Chhattisgarh, Haryana, Chandigarh and Delhi. Over the central and eastern parts of the country, the average number of cold wave days increased by more than five days per decade, and even more by over 15 days, in some places during the 2011-2021 period”.

On average, these regions used to record 2 to 5 cold wave days per 10 years during most decades from 1951 to 2011, but this rose to nearly 5 to 15 days in the last decade (ending 2021).

Even in built-up areas, where the Urban_Heat_Island-effect will be a negating factor, the data also showed that cold waves days in Haryana, Chandigarh and Delhi have increased to 5 to 10 per decade during the last 20-year period vs the average of 2 to 5 in the previous decades.

The study found that the longest cold waves – more than 60% - that occured during the last eigth decades were associated with La Niña conditions in the Equatorial Pacific Ocean.

Mandal: “We wanted to understand through the study if there can be a reduction in cold wave events amidst a global warming scenario. We, however, found that occurrences of cold wave events have continued even under the general warming scenarios.”

So, even the climate doesn't like Indians. The conditions in the country get more extreme, where the hot periods get even hotter and the cold periods get even colder.

[1] Raju Mandal and Susmitha Joseph: Diagnostics and real-time extended range prediction of cold waves over India in Climate Dynamics - 2023

Ancient Alaskan sand dunes

Sand dunes in Alaska (USA)? Were parts of Alaska akin to the Sahara or were these dunes once coastal dunes? But 55 kilometers above the Arctic Circle?

Situated in Kobuk Valley National Park, the Great Kobuk Sand Dunes rise unexpectedly out of the sea of trees along the southern bank of the Kobuk River. These dunes – the largest active sand dunes in the Arctic – along with the smaller Little Kobuk Sand Dunes and Hunt River Sand Dunes create more than 75 square kilometers of towering sand. There are smaller patches of dune all along the Tanana River up to the Canadian border, and just across the border there is an enormous dune field. Some of the dunes in the Great Kobuk Sand Dunes rise over 30 meters high and these are the largest active sand dunes in arctic North America.

Kobuk Valley’s sand dunes are a relic of the last Ice Age. 28,000 years ago, the Earth cooled and glaciers began to form high in the mountains surrounding the valley. Over time, the slow, grinding advance and retreat of the glaciers ground the rocks beneath them into a fine sand which was blown by the wind into the sheltered, ice free Kobuk Valley.

In a 1990 paper, Peter Lea and Chris Waythomas mapped out the active and inactive sand bodies in Alaska[1]. Sand is just about everywhere, but most of the dunes are now covered with trees and shrubs. Large sand deposits remain on Alaska’s North Slope, the Seward Peninsula and all through Southwest and Interior Alaska (where the Taylor Highway dune is located).

In a study of the Nogahabara dunes, scientists including Mann wrote that one of the active dunes’ values is continuing to host plants like the Asiatic sand sedge (Carex kobomugi) that are relics from the time of the Bering Land Bridge[2].

Sand deposits everywhere in Alaska harken back to a time thousands of years ago when big winds blasted fine particles of glacier-ground mountain a long way. It must have been an unpleasant time to be walking around Alaska, but scientists like Mann are fascinated with what it left behind.

[1] Lea and Waythomas: Late-pleistocene eolian sand sheets in Alaska in Earth and Oceanographic Science Faculty Work – 1990
[2] Mann et al: Holocene history of the Great Kobuk Sand Dunes, Northwestern Alaska in Quaternary Science Reviews - 2002

The death of Mono Lake (California, USA)

Mono Lake is a saline soda lake in Mono County (California, USA). The lack of an outlet causes high levels of salts to accumulate in the lake which make its water alkaline.

The city of Los Angeles diverted water from the freshwater streams flowing into the lake, lowering its lake level. But 2022 was already the third consecutive year of drought that shrunk the creeks that cascade down the eastern Sierra Nevada. The level of Mono Lake has fallen so low it has triggered a 72% reduction in the amount of water Los Angeles could divert from area streams.

On April 1, 2022, Mono Lake’s level measured just under 1,945 meters above sea level — about 2.5 centimeters below a threshold set in the licenses of Los Angeles Department of Water and Power (DWP) for diverting alpine runoff from streams that feed the lake east of Yosemite National Park.

The measurement, taken at the start of a new runoff year, triggered a requirement that the DWP reduce its annual water exports from 19,735,680 m³, which is enough to supply 192,000 residents, to 5,550,660 m³, just enough to serve 54,000 residents. Over the last runoff year from April through March, the DWP exported 17,022,024 m³ from Mono Basin, less than the permitted of 5,550,660 m³. That amount shrunk by two-thirds during the next 12 months.

The last time Mono Lake fell below the same threshold was from 2015 to 2017, in the final years of California’s last severe drought. Mono Lake’s level rebounded with wet weather in 2017, then declined over the last three extremely dry years.

The hypersaline high-desert lake, famous for its towering, craggy tufa formations, has been at the center of long-running disputes over the city’s diversions of water from the lake’s feeder streams. The State Water Resources Control Board established limits on diversions in 1994 to resolve a fight between environmentalists and Los Angeles.

But conservationists remain concerned about the environmental effects of decades of water diversions, especially given the current extreme drought and the worsening effects of global warming. The Mono Lake shoreline is continuing to retreat, creating a 'bathtub ring' of dusty lake bottom. Prepare for dust and salt storms in the near future.

Mono Lake's current level can be checked here.

Parched Poyang Lake (China)

Poyang Lake, in China’s Jiangxi Province, routinely fluctuates in size between the winter and summer seasons. In winter, water levels on the lake in are typically low. Then, summer rains cause the country’s largest freshwater lake to swell as water flows in from the Yangtze River.

[Situation on 10 July 2022]

The lake has not swelled in the summer of 2022. A prolonged heat wave and drought across much of the Yangtze River Basin dried the lake out early and pushed water levels to lows not seen in decades.

[Situation on 27 Augustus 2022]

The Operational Land Imager (OLI) on Landsat 8 acquired these pairs of images on July 10, 2022 (left images), and August 27, 2022 (right images). The images are composites, and combine OLI observations of shortwave infrared, near infrared, and visible light.

The highest water levels of the year on Poyang Lake occurred on June 23 (as measured at the Xingzi Station). After that, high temperatures and a lack of rain caused the lake to drop rapidly, according to the Jiangxi Hydrological Monitoring Center. By August 6, water levels had declined to 11.99 meters, marking what the center called the start of the lake’s 'dry season'. That low came roughly 100 days earlier than usual. It was the earliest date that the water dropped to such a low mark since records were first kept in 1951. Water levels have continued to drop, registering 8.96 meters on August 30.

The emptying of Poyang Lake has disrupted irrigation, shipping, and drinking water systems for nearby communities. In addition, millions of people living throughout the Yangtze River watershed are being affected as extreme heat and drought put pressure on China’s water supplies, electricity generation, farming, and industrial activity. Also, in past times when it dried up it became a major dust source.

Megadrought Threatening Millions Of Americans

The Colorado River Basin meanders through seven US states and supplies water to Lake Powell in the Upper Basin and Lake Mead in the Lower Basin. In turn, these reservoirs deliver water and power to millions of Americans.

They’re also going dry.

[Photos of the Colorado River showing drought at the Overton Arm between 2000 and 2022.]

In August 2021, the Bureau of Reclamation issued the first Level One Shortage Condition when Lake Mead fell below 1,075 feet (328 meters). Then, in March 2022, the Bureau reported that Lake Powell fell below the target elevation of 3,525 feet (1074 meters) for the first time since the 1960s. In 1999, Lake Powell averaged a water elevation of almost 3,681 feet (1,122 meters), and Lake Mead was almost near capacity at 1,220 feet (372 meters) near the dam.

After more than 20 years of severe drought, the Western US has officially entered a megadrought (meaning 20 or more years of below average precipitation), and Lake Powell’s water level is down almost 150 feet (46 meters). Lake Mead’s water level is down nearly 176 feet (54 meters).

Water conditions on the river depend largely on snowmelt in the basin’s northern areas of Colorado and Wyoming, and global warming will likely decrease the amount of snow that accumulates there every year.

The result is that the lives and livelyhood of millions of Americans who live in the affected areas are threatened because of a shortage of water and hydroelectric power.

Bowing to the reality of dwindling water levels, the American Congress began enacting contingency plans for when and if water levels dropped below a certain level in Lake Mead and Lake Powell.

For Lake Mead, the Drought Contingency Plan decreases water deliveries to Arizona and Nevada if the water level falls below 1,075 feet (328 meters) (pdf). For Lake Powell, the Drought Response Operations Agreement kicks in when water levels fall below 3,525 feet (1074 meters).

Despite these efforts, storage levels at both reservoirs have continued to fall, CRS reported in August 2022 (pdf). Studies indicate the ongoing possibility of Lake Mead falling significantly more and triggering additional shortages within two years.

Capacity of Lake Powell is shrinking due to sediments

Sedimentation is a known problem for artificial lakes. Sediments are mostly composed of sand with the remainder being a mix of clay and silt. Most of the clay and silt has been transported to the deepest parts of the lake by the dense, sediment-laden currents flowing into Lake Powell.

Lake Powell, located in the Colorado River Basin is the second-largest reservoir in the US. Both Lake Powell and nearby Lake Mead, the nation's largest reservoir, have drained at an alarming rate.

In August 2021, the government declared a water shortage on the Colorado River for the first time after Lake Mead's water level plunged to unprecedented lows, triggering mandatory water consumption cuts for states in the Southwest that began in January.

And in May 2022, Lake Powell dipped below the critical threshold, sparking additional concerns about water supply and hydropower generation millions of people in the Western US rely on for electricity.

Lake Powell has lost nearly 7% of its potential storage capacity since 1963, when Glen Canyon Dam was built, a new report shows. It seems that Lake Powell suffered an average annual loss in storage capacity of about 6.8 percent (from 1963 to 2018) and 4.0 percent (from 1986 to 2018).

So, not only is less and less water flowing into Lake Powell, but its total capacity is dwindling too as a result of sediments. It's like smoking a cigar with both ends alight.

The system supplies water for more than 40 million people living across seven Western states and Mexico. Lake Powell and Lake Mead provide a critical supply of drinking water and irrigation for many across the region, including rural farms, ranches and native communities. This region is already devastated by continuing droughts.

[Drought in the southwestern US]

In the end, there will be too little water in both Lake Powell and Lake Mead to service the entire southwestern US with its ever growing demand for water. Maybe people shouldn't live in a desert.

Seen from space: dust in Southeast Asia

This map of Southeast Asia from May 1, 2022 shows aerosols in the atmosphere from seasonal fires and blowing dust. Measurements were taken by the Visible Infrared Imaging Radiometer Suite VIIRS instrument on the Joint Polar Satellite System (JPSS).

Dark red color indicates very thick aerosols, in areas where smoke & dust are prevalent.

Air quality in Delhi (India) gets even worse

We've talked about Delhi (India) before and every year the air quality seems to get worse. Indian politicians seem unable or unwilling to remedy the problem that will eventually (not potentially) will kill their voters in ever larger numbers.

In April 2022, temperatures in large parts of the country already reached nearly 50^oC, and it will even get warmer and worse in the coming months. Monsoon rains will only (hopefully) arrive in June.

Huge numbers of cars crowd the city, many of which are ancient trucks, lorries and buses, which emit extremely high volumes of particularly harmful soot that all living creatures inhale. This soot (or black carbon) is caused by the inefficient combustion of fossil fuels and various forms of organic matter, such as food waste, and forest and farmland being set ablaze.

Delhi has an estimated (nobody really knows, because nobody really cares) population of about 30 million and those amounts of people produce an immense amount of waste. Modern cities can dispose of that waste in modern ways, possibly even 'go green' to limit the daily amounts that end up in a landfill or incinerator.

Not Delhi, because that city simply dumps its waste in a landfill that has been completely filled decades ago. The solution was simple: keep dumping on the same spot, which turned a landfill into a massive garbage dump. The mountain of garbage is now more than 60 meters high. It has been 'officially closed' for years, but more than 2,300 tons of garbage still get dumped there every day.

The sweltering heat also set fire to this garbage dump (again), probably caused by higher levels of methane and – yup – smoking, although the 'official cause isn't known'.

Now, acrid smoke drifts once again over the city, further reducing the already bad air quality.

[Update April 23, 2023] A year later: How does Delhi plan to control landfill fires this season? As the temperature rises and with it the possibility of fires at the landfills and dump sites, a number of suggestions have been put forward to counter this danger, such as installing spark arresters; laying pipelines at the dumpsite to release methane; increasing number of tankers to sprinkle water; ensuring adequate water storage capacity and pumps at the dumpsite to douse fires; CCTVs; methane detectors; temperature sensors and fire alarms; jetting machines to keep vulnerable areas damp; construction of roads around the dumpsite to allow movement of fire tenders and patrolling; and plantation in areas that are cleared.

What has been done? As so often in India: nothing.

Persistent La Niña promotes drought

Drought continues to prevail from southwestern Canada’s Prairies through the entire western half of the United States. January and February weather allowed the drought to expand eastward into the western US Corn Belt, which is a bad omen since winter is normally a time for diminishing drought rather than expanding it.

La Niña events remove moisture from the mid-latitudes in both the Northern and Southern Hemisphere. Dryness that occurred in the summer 2021 in Canada and the central United States impacting crop production could easily be attributed to La Niña with some help from the negative phase of Pacific Decadal Oscillation (PDO). Dryness last summer in Russia’s eastern New Lands and Kazakhstan also can be linked to La Niña.

Multi-year droughts occurred in the 1930s and 1950s and each were associated with lengthy La Niña events. Each of the prolonged La Niña events always occurred shortly after the solar minimum in sunspots. Normally, the longer La Niña events occur in every other 11-year solar cycle.

The statistics suggest La Niña will prevail longer and that has been this meteorologist’s concern for an extended period of time. All indicators are suggesting this La Niña will be around through the entire spring and now there are a few forecasters suggesting it will linger into the summer.

With drought already in place across the central and western parts of North America there will already be potential for a high-pressure ridge to develop over the US Great Plains during the middle and latter part of spring. If La Niña lasts through spring that would be long enough for the summer ridge of high pressure to begin to build strongly across the region prior to the arrival of summer heat.

The earlier-than-usual development of high pressure in the central United States will suppress rain events and allow warming to occur, which will further exacerbate the dryness. Essentially, La Niña conditions that last through spring will leave behind enough dryness in agricultural areas to allow drought to begin festering, expanding and intensifying, which could lead to a more serious bout of dryness. If La Niña does go away after the ridge is well established in June there would not be enough time to change the weather pattern until seasonal cooling arrives in the late summer or autumn resulting in a more persistent ridge of high pressure and greater drought regardless of what happens to La Niña after June.

Western US faces the worst drought in 1,200 years

The drought that has parched southwestern United States and parts of Mexico over the last two decades is the worst to hit the region in at least 1,200 years, according to new research. Occasional heavy snow or rainfall have not been enough to compensate the lack of moisture.

The scientists (and subsequently the media) were quick to point an accusing finger at us, humans. "The turn-of-the-21st-century drought would not be on a megadrought trajectory without anthropogenic climate change," lead author Park Williams, an associate professor at the University of California in Los Angeles, and colleagues wrote.

Over the last decade, California and other western states have experienced severe water shortages, triggering periodic restrictions on water usage and forcing some communities to import bottled water for drinking.

During the summer of 2021, two of North America's largest reservoirs (Lake Mead and Lake Powell) reached their lowest recorded levels ever.

Running simulations based on soil moisture records stretching back 1,200 years, the researchers calculated a 75 percent chance that the drought would extend through the 2030s.

Tree-ring analysis shows that the area west of the Rocky Mountains from southern Montana to northern Mexico was hit repeatedly by so-called megadroughts - lasting at least 19 years - between the years AD 800 and AD 1600.

Earlier research had established that the period 2000-2018 was likely the second worst drought since the year 800, topped by one in the late 1500s. Data from 2019-2021, backed by new climate models released last year, have revealed the current drought to be worse than any from the Middle Ages.

So, we now learn that extreme droughts are nothing new in the southwestern United States. However, the researchers maintain that without climate change it "wouldn't hold a candle to the megadroughts of the 1500s, 1200s or 1100s."

That's not science, but seems more like victim blaming* to me. But we could have guessed that conclusion, because the Journal in which the article was published is called 'Nature Climate Change'.

[1] Williams et al: Rapid intensification of the emerging southwestern North American megadrought in 2020–2021 in Nature Climate Change – 2022

* Victim blaming occurs when the victim of a crime (or any wrongful act) is held entirely or partially at fault for the harm that befell them.

The end of turqouise-coloured lakes

Glaciers, even small ones, are rivers of ice. Along their way they erode and pulverize rock into tiny flour-fine particles.

Rock flour (or glacial flour) consists of fine-grained, silt-sized particles of rock, generated by mechanical grinding of bedrock by glacial erosion. Once the ice in which it is transported downward is melted, the material becomes suspended in meltwater making the water appear cloudy, which is sometimes known as glacial milk.

When the sediments enter a river, they turn the river's colour grey, light brown, iridescent blue-green, or milky white. If the river flows into a glacial lake, the lake may appear turquoise in colour as a result.

It is simply the result of reflection of light. Sunlight reflects off these tiny white particles. Because of the scattering of the light as it hits these particles, the lake takes on this turquoise colour.

But even this phenomenon might become a thing of the past as a direct result of global warming. When temperatures rise, glaciers melt and retract They may even completely disappear. No glacier means no grinding of the rock beneath it. That in turn means that no rock flour will be created that could give a mountain lake that beautiful turquoise hue.

Between the '70s and the '90s, when nobody was talking about global warming, a lot of smaller glaciers had already melted and disappeared[1]. Even now lakes are clearing up, turning into 'normal' lakes.

A clear blue lake admits much more sunlight into depths than a lake clouded with glacial flour. That's likely to bring in a different local ecology, because organisms adapted to the low light of milky waters are unlikely to survive what would be to them a harsh new glare of ultraviolet radiation. The problem is especially acute because of the speed of the transition. If you take that sunscreen away, some organisms may not be able to tolerate that increase in UV radiation. It doesn't give organisms time to adapt.

Researchers like Rolf Vinebrooke suspect that some of these lakes, at least temporarily, may be left 'biologically impoverished'.

[1] Vinebrooke: The Changing Colours of Mountain Lakes in the Twenty-First Century in State of the Mountains Report 2021. See here.

Rare subtropical storm forms in South Atlantic Ocean

In 2021, an unusual tropical system developed in the southern Atlantic Ocean where tropical systems rarely occur. Only 14 named tropical systems were ever recorded in the southern Atlantic Ocean, a majority of which were 'just' subtropical storms. This means that they have meteorological characteristics of both a tropical storm and a non-tropical storm.

On April 20, 2021, subtropical storm Potira formed off the coast of southeastern Brazil with sustained winds of 65 kilometers per hour outside of the traditional northern Atlantic.

Potira's origin could be traced back to a non-tropical disturbance that moved off the coast of Brazil over the previous weekend before stalling over the ocean just off the coast. As it sat over the water, it gradually started to organize and take on some characteristics of a proper tropical storm, eventually being declared a subtropical storm by Brazil's Navy.

The frequency of this phenomenon has been trending upward in recent years. The most recent was subtropical storm Oquira which developed on December 28, 2020.

Only one system has ever reached hurricane status in the South Atlantic. In 2004 near the end of March, Hurricane Catarina became a Category 2 hurricane before making landfall in Brazil.

Why are tropical systems so rare in the southern Atlantic Ocean? The conditions south of the equator are different than they are north of the equator. One of the biggest factors is windshear. When wind shear is low, it allows disturbances to organize and potentially develop into a tropical storm or hurricane. This disruptive wind is typically higher in the southern Atlantic when compared to the northern Atlantic. Another factor is that the water temperature is typically lower in this region of the southern Atlantic, limiting the potential for tropical development.

When was the Amazon rainforest created?

We know that nowadays dust from the Sahara feeds the Amazon rainforest, but exactly when the Amazon jungle was created was unclear. Now we know.

65 million years ago a large asteroid impacted the Yucatan peninsula. It killed the dinosaurs and heralded a nuclear winter that lasted several years. But the 11 to 81 kilometers wide asteroid didn't 'just' erase the dinosaurs from the face of the earth, the impact had a profound effect on the fauna too.

Recently, researchers used fossil pollen and leaves from Colombia to investigate how the impact changed South American forests[1]. They found that cone-bearing plants called conifers and ferns were common before the huge asteroid struck what is now the Yucatan Peninsula in Mexico.

But after the devastating impact, plant diversity declined by roughly 45% and extinctions were widespread, particularly among seed-bearing plants.

While the forests recovered over the next six million years, flowering plants, came to dominate them.

The structure of tropical forests also changed as a result of this transition. During the late Cretaceous Period, when the dinosaurs were still alive, the trees that made up the forests were widely-spaced. The top parts did not overlap, leaving open sunlit areas on the forest floor.

But post-impact, forests developed a thick canopy that allowed much less light to reach the ground.

So how did the impact transform the sparse, conifer-rich tropical forests of the dinosaur age into the rainforests of today, with their towering trees dotted with multi-coloured blossoms and orchids?

The scientists have formulated some theories as to why this could happen. Firstly, the foraging dinosaurs could have kept the forest from growing too dense by feeding on and trampling plants growing in the lower levels of the forest. A second explanation is that falling ash from the impact enriched soils throughout the tropics, giving an advantage to faster-growing flowering plants. The third explanation is that the preferential extinction of conifer species created an opportunity for flowering plants to take over.

These ideas aren't mutually exclusive, and could all have contributed to the outcome we see today.

[1] Extinction at the end-Cretaceous and the origin of modern Neotropical rainforests in Science - 2021

The Sahara was once a Paradise

Large parts of today’s Sahara Desert were green thousands of years ago. Prehistoric engravings of giraffes and crocodiles testify to this, as does a stone-age cave painting in the desert that even shows swimming humans.

However, these illustrations only provide a rough picture of the living conditions. Recently, more detailed insights have been gained from sediment cores extracted from the Mediterranean Sea off the coast of Libya. A research team examined these cores and discovered that the layers of the seafloor tell the story of major environmental changes in North Africa over the past 160,000 years.

A team of scientists organized a research cruise on the Dutch vessel Pelagia to the Gulf of Sirte in December 2011[1]. “We suspected that when the Sahara Desert was green, the rivers that are presently dry would have been active and would have brought particles into the Gulf of Sirte, situated to the north of Libya”, says lead author Cécile Blanchet. Such sediments would help to better understand the timing and circumstances for the reactivation of these rivers.

The scientists were able to recover 10-meters long columns of marine mud. “The marine mud layers contain rock fragments and plant remains transported from the nearby African continent. They are also full of shells of microorganisms that grew in seawater. Together, these sediment particles can tell us the story of past climatic changes”, explains Blanchet.

“By combining the sediment analyses with results from our computer simulation, we can now precisely understand the climatic processes at work to explain the drastic changes in North African environments over the past 160,000 years”, adds co-author Tobias Friedrich.

From previous work, it was already known that several rivers episodically flowed across the region, which today is one of the driest areas on Earth. The team’s unprecedented reconstruction continuously covers the last 160,000 years. It offers a comprehensive picture of when and why there was sufficient rainfall in the Central Sahara to reactivate these rivers. “We found that it is the slight changes in the Earth’s orbit and the waxing and waning of polar ice sheets that paced the alternation of humid phases with high precipitation and long periods of almost complete aridity”, explains Blanchet.

The fertile periods generally lasted five thousand years and humidity spread over North Africa up to the Mediterranean coast. For the people of that time, this resulted in drastic changes in living conditions, which probably led to large migratory movements in North Africa.

“With our work we have added some essential jigsaw pieces to the picture of past Saharan landscape changes that help to better understand human evolution and migration history”, says Blanchet. They now understand more about what controlled the past succession of humid and arid phases in North Africa.”

[1] Cécile Blanchet et al: Drivers of river reactivation in North Africa during the last glacial cycle in Nature Geoscience – 2021

India: Burning Plastics Increases Smog

You probably know that plastic waste is increasingly polluting our oceans but new data shows that plastic is also contributing to the rampant air pollution in Indian cities.

Scientists were puzzled why Delhi was more susceptible to thick smogs than other polluted cities such as Beijing. New research links this to tiny chloride particles in the air that help water droplets to form[1]. Globally, chloride particles are mainly found close to coasts, due to sea spray and carried some distance inland by the wind, but the air in Delhi and over inland India contains much more than expected.

At first, the sources were thought to be illegal factories around Delhi that recycle electronics and those that use strong hydrochloric acid to clean and process metals. These are certainly part of the problem, but new measurements have revealed another source.

Other researchers looked at the other pollutants that increased at the same time as the chloride particles. This chemical fingerprint matched the burning of household waste containing plastics and the burning of plastics themselves. These large amounts of chloride are estimated to be responsible for around half of Delhi’s smog events. Episodic hourly averaged chloride concentrations reached 50–100 µg m⁻³, ranking among the highest chloride concentrations reported anywhere in the world.

In low-income countries about 90% of waste ends up in open dumps or is burned in the open air. If you set fire to plastic, it rapidly reveals its origins as an oil-based product by producing huge amounts of black smoke. Using data on the contents of rubbish from around the world, researchers estimated that the soot from open waste burning has a global warming impact equivalent to between 2% and 10% of the global emissions of carbon dioxide[2].

Burning plastics also produces large amounts of dioxins and other highly toxic pollutants that can persist in the food chain. Modern waste incinerators in the UK and Europe go to great lengths to reduce these toxic emissions but there are no protections when waste is burned at home or in the open air.

The problems of waste burning in Indian cities do not end there. As James Allan from the University of Manchester, who took part in the latest Indian study, explained, the extra chloride could be promoting chemical reactions between different air pollutants. This includes adding to the ground-level ozone across India. Already this is estimated to reduce yields of some Indian crops by 20% to 30%.

The solution to this problem seems easy: better waste management and an end to global plastic production and use.

[1] Gani et al: Submicron aerosol composition in the world's most polluted megacity: the Delhi Aerosol Supersite study in Atmospheric Chemistry and Physics – 2019. See here.
[2] Reyna-Bensusan et al: Experimental measurements of black carbon emission factors to estimate the global impact of uncontrolled burning of waste in Atmospheric Environment - 2019

London: The Deadly Fog of 1952

For five days in December of 1952, the fog enveloped all of London. Residents at first gave it little notice because it appeared to be no different from the familiar natural fogs that have swept over Great Britain for thousands of years.

But over the next few days, conditions deteriorated, and the sky literally turned dark. Visibility was reduced to just 1 meter in many parts of the city and tens of thousands of people had trouble breathing. By the time the fog had lifted on December 9, at least 4,000 people had died and more than 150,000 had been hospitalised.

Researchers now estimate that the total death count was likely more than 12,000 people[1]. Despite its lethal nature, the exact cause of the deadly fog has largely remained a mystery. Recently, a team of researchers has determined the likely reasons for its formation[2].

Emissions from burning coal interacted with the deadly fog, but the exact chemical processes that led to the deadly mix of pollution and fog were not fully understood. To determine what turned the fog into a killer, a team of scientists recreated the fog in a lab using results from laboratory experiments and atmospheric measurements from Beijing and Xi’an, two heavily polluted cities in China.

They found that sulfate was a big contributor to the deadly London fog. Sulfuric acid (H₂SO₄) particles, which formed from the sulfur dioxide (SO₂) that was released from the burning of coal, were also a component of the fog. But how did sulfur dioxide get turned into sulfuric acid?

The results showed that it was an oxidation of sulfur dioxde (SO₂) by nitrogen dioxide (NO₂), another by-product of coal burning, resulting in sulfuric acid (H₂SO₄). These acidic particles were suspended in the fog and thus an acidic haze was covering the city. Inhaling acids is never good for your lungs.

The air of cities in China, which is often heavily polluted, has a chemistry that’s similar to the killer fog in London. China is home to 16 of the world’s 20 most polluted cities.

The researchers said that the main difference between China’s smog and the killer London fog is that China’s haze is made up of much smaller nanoparticles.

[1] Bell, Davis: Reassessment of the lethal London fog of 1952: novel indicators of acute and chronic consequences of acute exposure to air pollution in Environmental Health Perspectives – 2001
[2] Wang et al: Persistent sulfate formation from London Fog to Chinese haze in PNAS – 2016

Where's the Rio Grande?

Even if you don't speak Spanish, you will understand that the Rio Grande means 'Great River'. Numerous westerns featured this once majestic river that serves as part of the natural border between the US state of Texas and the Mexican states of Chihuahua, Coahuila, Nuevo León, and Tamaulipas.

In the past, the Rio Grande would run through Las Cruces, the second-largest city in New Mexico (USA) for the irrigation season from February to October. But in 2020, the river didn’t flow until March, and was dry by September. In 2021 it is estimated that water levels will be so low they won’t arrive until June and it will probably be gone again at the end of July.

So, the Rio Grande changed from a great river to just a trickle. What happened?

The Rio Grande’s flow was always variable, but drying up completely was an extraordinary event until the 1890s.

Due to (supposed) climate change or the lasting effects of El Niño, hotter and drier seasons are reducing the snowpack that melts to feed the Rio Grande, and rising temperatures are increasing evaporation from the reservoirs. Because of this, the river has had just seven years with a 'full supply' of water in the past 20, and only two in the past decade.

In Las Cruces, the Rio Grande’s flow is diverted and drained, flooding into pecan orchards and feeding crops like onions, corn and famously green chillis, for which the state is known. But New Mexico is mostly desert and it can only support agriculture because of irrigation. Despite making up only about 2.4% of New Mexico’s GDP, the agriculture and processing industry receives three-quarters of the state’s surface and groundwater.

So much water is diverted, that when the growing season ends, nothing is left in the river near Las Cruces.

It not climate change or the effects of El Niño but the increased demands of agriculture that hasn't any right to be in the desert that is the principal cause of the disappearance of the once great Rio Grande.

Bangladesh: Drinking water turns saline

A look at the map of Bangladesh shows that the country is awash with water. The sea encroaches the land and vast rivers flow southwards from the low lying land to the sea. So, water is everywhere in coastal Bangladesh, but is increasingly undrinkable as sea levels rise and land sinks.

As climate change has (supposedly) raised sea levels, most scientists forget to mention that excessive population growth also results in ever decreasing groundwater levels. Coastal Bangladesh is sinking because of a phenomenon called subsidence. This happens when extraction of groundwater causes layers of rock and sediment to slowly pancake on top of each other. The effect is worsened by the sheer weight of all the buildings to house the ever increasing population.

Higher seas, sinking cities, and more people mean worsening impacts from storms and floods. And the frequency of these events is increasing, too. Recorded floods and severe storms in Southeast Asia have risen sixfold, from fewer than 20 from 1960 to 1969 to nearly 120 from 2000 to 2008, according to an Asian Development Bank study. At the same time. drinking water turns saline and undrinkable.

Back in 2011, a study estimated salt intake from drinking water in Bangladesh’s coastal population exceeded recommended limits[1]. Things have worsened since then.

Many studies have shown that people in coastal Bangladesh are suffering more and more as saltwater intrudes into their water supply.

A 2014 World Bank report, forecasts that by 2050 climate change will cause major changes in river salinity in the south-west coastal region during the October-May dry season[2]. This will result in a shortage of drinking and irrigation water, with changes in aquatic ecosystems.

The shortage is here already. And all over coastal Bangladesh, it has spawned a new business: selling potable water.

The saltwater invasion of drinking water sources has been worsened even more by commercial shrimp farming, which started in coastal Bangladesh in the 1980s. Shrimp farmers flooded plots of land with saltwater because shrimps grow best in brackish water. That saltwater has seeped into aquifers everywhere. 

The problem isn't isolated to Southeast-Asia. Even Venice is sinking.

[1] Khan et al: Drinking Water Salinity and Maternal Health in Coastal Bangladesh: Implications of Climate Change in Environmental Health Perspectives – 2011
[2] Dasgupta et al: River Salinity and Climate Change Evidence from Coastal Bangladesh - The World Bank Development Research Group Environment and Energy Team – 2014. See here.

Atolls grow (and not shrink) despite global warming

You've been led to believe that global warming leads to rising sea levels. This, in turn, would lead to the disappearance of low-lying atolls. That would certainly be a disaster for communities that are living on those islands.

But, now, against all odds, most low-lying reef islands actually appear to be growing in some parts of the world, despite rising sea levels, increasing their footprint and defying calamatous predictions.

Geomorphologist Murray Ford led a team of researchers who examined Jeh Island, one of the 56 islands that make up the Ailinglaplap Atoll in the (Republic of the) Marshall Islands in the Pacific, itself considered one of the most endangered nations on Earth.

Ford and his team pored over old aerial and new satellite imagery of the island from above and made the startling discovery that not only has Jeh increased in total land area by 13 percent since 1943, it may actually have once been four separate islands which have now morphed together due to net land-mass gains[1].

”Counter to predictions, popular media coverage and political proclamations, recent studies have shown the majority of reef islands studied have been stable or have increased in size since the mid-20th century," Ford, explains.

According to the geomorphologist and his colleagues, the more dire sea-level rise predictions were based on the assumption that islands are static and unchanging and would therefore simply drown once the tides rose enough.

The research team found that the islands grew by organic material formed by the reef and that sediment washed ashore by the tides.

"The coral reefs which surround these islands [are] the engine room of island growth, producing sediment which is washed up on the island shoreline," Ford explains. "Healthy coral reefs are essential for this process to continue into the future."

Research dating back as far as 2018 found that among 30 coral atolls, accounting for over 700 islands in total, 88.6 percent remained stable or increased in size in recent decades, while none lost land overall.

[1] Ford et al: Active Sediment Generation on Coral Reef Flats Contributes to Recent Reef Island Expansion in Geophysical Letters - 2020. See here.

Shift in SE Asian monsoon resulted in dry Sahara 4,000 years ago

Today, the Southeast Asian Monsoon provides critical water resources to more that 600 million people each year. Even slight variations in the strength and/or timing of the monsoon can have profound impacts on the region. But there's a problem, because while we do know more, very little is known about the range and mechanisms of Southeast Asian monsoon variability, particularly on timescales such as the Holocene. The mid- to late Holocene, roughly six to four thousand years ago, was characterized by one of the largest climate shifts since the last glacial termination.

New evidence from stalagmites from a cave in Laos, indicate a major decrease of monsoon rainfall in mainland Southeast Asia during the mid-to late Holocene (6,000 to 4,000 years ago). At the same time the African monsoon failed to deliver enough moisture and that signalled the end of the 'Green Sahara'[1].

It signalled the end of the 'Green Sahara' (also known as as the African Humid Period), when a vegetated northern Africa into the current desert landscape. It also resulted in the collapse of the Akkadian Empire of Mesopotamia, the de-urbanization of the Indus Civilization, and the spread of pastoralism along the Nile, as people were driven from the arid Sahara.

Computer modelling experiments show that reduced vegetation and increased dust loads during the Green Sahara termination shifted the Walker circulation, the air flow in the tropics in the lower atmosphere, eastward and cooled the Indian Ocean, causing a reduction in monsoon rainfall in mainland Southeast Asia. The results of the research indicate that reduced vegetation and increased dust from the Sahara may have been the catalyst for societal shifts in mainland Southeast Asia.

The megadrought it caused would have led to mass population movements and the adoption of new, more resilient subsistence strategies. It may even have led to the inception of Neolithic farming in mainland Southeast Asia, the researchers have concluded.

So, maybe as a result of an extreme El Niño, the Walker circulation was influenced, which resulted in an decrease in monsoon activity in Southeast Asia and Northern Africa. This in turn resulted in an arid and dusty Sahara which now feeds the Amazon rainforest and forced people in Southeast Asia to migrate.

[1] Griffiths et al: End of Green Sahara amplified mid- to late Holocene megadroughts in mainland Southeast Asia in Nature - 2020

The Dangers of Fugitive Dust

Fugitive dust is an environmental air quality term for very small particles suspended in the air, the source of which is primarily the Earth's soil. It does not include particulate matter from other common sources, such as vehicle exhaust or smokestacks.

Fugitive dust results from dry conditions where there is insufficient moisture content in the ground to hold the soil together.

Fugitive dust arises from the mechanical disturbance of granular material exposed to the air. Dust generated from these open sources is termed 'fugitive' because it 'escapes' and is not discharged to the atmosphere in a confined flow stream from a exhaust pipe or chimney.

Common sources of fugitive dust include unpaved roads, agricultural tilling operations, aggregate storage piles, and heavy construction operations. Fugitive dust particles are mainly minerals common to soil, including silicon oxides, aluminium, calcium, and iron.

Thus, the dust-generation process is caused by two basic physical phenomena: [a] Pulverization and abrasion of surface materials by application of mechanical force through implements (wheels, blades, explosion, etc.) and [b] Entrainment of dust particles by the action of turbulent air currents, such as wind erosion of an exposed surface by wind speeds over 20 kilometers per hour.

About half of fugitive dust particles are larger than 10 microns in diameter and settle more quickly than the smaller particles. The U.S. Environmental Protection Agency (EPA) estimated that fugitive dust was responsible for 92% of the PM-10 emissions in the United States in 1995.

[The fungus Coccidioides]

It's just dust, you might argue, but danger hides in the soil. A family of fungi, called Coccidioides, lingers in the soil and dust in the United States, Meso and South America. When you inhale the fugitive dust, you might also inhale the fungus, leading to a potentially fatal fungal pneumonia. The disease is called coccidioidomycosis or Valley Fever.

The latest numbers show that in 2018, about 15,600 people were diagnosed with Valley Fever in the United States, with most cases coming out of southern Arizona and California’s San Joaquin Valley. But these numbers only reflect known cases reported to the Centers of Disease Control. Experts think that number is probably much higher.

Symptoms include fatigue (tiredness), cough, fever, shortness of breath, headache, night sweats, muscle aches or joint pain, rash on upper body or legs.

Air pollution may be ‘key contributor’ to Coronavirus deaths

New research examined the relationship between [1] levels of nitrogen dioxide (NO₂), a pollutant produced mostly by older diesel vehicles, [2] weather conditions that can prevent dirty air from dispersing away from a city and [3] Coronavirus fatalities[1]. Long-term exposure to NO2 can cause severe health problems, such as hypertension, diabetes, heart and cardiovascular diseases and even death.

[Dense smog over Milan]

The analysis was conducted on a regional scale and combined with the number of deaths taken from 66 administrative regions in Italy, Spain, France and Germany. Results show that out of the 4443 fatality cases, 3487 (78%) were in five regions located in north Italy and central Spain. Additionally, the same five regions show the highest NO₂ concentrations combined with downwards airflow which prevent an efficient dispersion of air pollution.

These results indicate that the long-term exposure to this pollutant may be one of the most important contributors to fatality caused by the Coronavirus in these regions and thus maybe across the whole world.

“Poisoning our environment means poisoning our own body, and when it experiences chronic respiratory stress its ability to defend itself from infections is limited,” said Yaron Ogen, who conducted the research.

The analysis is only able to show a strong correlation, not a causal link. “It is now necessary to examine whether the presence of an initial inflammatory condition is related to the response of the immune system to the coronavirus,” Ogen said.

A separate study looked at fine particle pollution (PM₁₀, PM_2.5) in the northern Italy and found that even small increases in levels in the years before the pandemic were associated with far higher death rates if infected with the Coronavirus[2].

Did I already mention that sigarette smoke also contain those pesky fine particles (PM_2.5)[3]?

[1] Ogen: Assessing nitrogen dioxide (NO₂) levels as a contributing factor to coronavirus (COVID-19) fatality in The Science of the Total Environment – 2020. See here. 
[2] Conticini et al: Can atmospheric pollution be considered a co-factor in extremely high level of SARS-CoV-2 lethality in Northern Italy? in Environmental Pollution - 2020. See here. 
[3] Jebel et al: Surface bound radicals, char yield and particulate size from the burning of tobacco cigarette in Chemistry Central Journal - 2017

Dust storms on Mars

If you've seen the movie 'The Martian', starring Matt Damon, you might have guessed that the weather on Mars can be pretty unpredictable.

When a huge dust storm on Mars turns up the power, it can easily turn into a gigantic weather phenomenon. During the last Martian global dust storm in 2018 orbiting space crafts kept a close eye on the planet, getting a good look at the storm's life-cycle. The tower that rose during that storm rose as high as 70 to 90 kilometers[1].

"Global dust storms are really unusual," said David Kass, a co-author of the paper. "We really don't have anything like this on the Earth. On Mars, the entire planet's weather changes for several months."

During the 2018 storm, NASA's Mars Reconnaissance Orbiter (MRO) saw something unusual. "Normally the dust would fall down in a day or so," said Heavens. "But during a global storm, dust towers are renewed continuously for weeks." In some cases, multiple towers were seen for as long as 3.5 weeks.

The dust towers that form during these storms are warmed by the Sun and rise high into the atmosphere. Scientists think that water molecules that form Mars' wispy clouds get trapped in all that dust, and are carried high into the atmosphere.

It's similar to how a thunderstorm cloud forms during a powerful storm on Earth. But at high altitudes on Mars, solar radiation breaks apart the H₂O molecules. These dust towers might explain, at least partially, how Mars lost its water over billions of years[2].

[1] Heavens et al: Dusty Deep Convection in the Mars Year 34 Planet-Encircling Dust Event in JGR Planets – 2019. See here.
[2] Heavens et al: Hydrogen escape from Mars enhanced by deep convection in dust storms in Nature Astronomy – 2018. See here.

Hindus perform ceremony in river covered in toxic foam

Thousands of Hindus in New Dehli, India's capital city, waded into a sacred river on Saturday, 02 November 2019, to observe the Chhath Puja festival despite the water being covered with toxic foam.

The Yamuna, a tributary of the Ganges, is one of India's most sacred rivers but has also become one of its most polluted.

Industrial effluents and untreated sewage continue to flow into the Yamuna, despite repeated government attempts to clean the sacred river.

For many Hindus, the Yamuna remains a key water source which resonates deeply with their faith so on that Saturday they waded into the extremely polluted waters nonetheless to observe the ancient festival which is dedicated to the Sun God.

The festival is to worship the Sun God and the rituals are rigorously observed over a period of four days. They include holy bathing, fasting and abstaining from drinking water (Vratta), standing in water for long periods of time and offering prasad (prayer) and arghya (offerings) to the setting and rising sun.

Strong winter dust storms and the collapse of the Akkadian Empire

Fossil coral records provide new evidence that frequent winter shamals (or dust storms) and a prolonged cold winter season contributed to the collapse of the ancient Akkadian Empire in Mesopotamia[1].

The Akkadian Empire (22th to 20nd century BC) was the first united empire in Mesopotamia and thrived with the development of irrigation. Yet, settlements appear to have been suddenly abandoned ca. 4,200 years ago, causing its collapse. The area would also not experience resettlement until about 300 years later.

Past studies have shown that the Akkadian Empire likely collapsed due to abrupt drought and civil turmoil. However, the climatic dynamics which caused widespread agricultural failures and the end of an era have yet to be sufficiently explored.

Researchers made paleoclimatic reconstructions of the temperature and hydrological changes of the areas around the archaeological site of Tell Leilan, the center of the Akkadian Empire. They sampled six 4,100-year-old fossil Porites corals from the Gulf of Oman, just directly downwind. The samples were aged by radiocarbon dating and geochemically analyzed to confirm they have not been significantly altered from their present state.

The coral data was then compared to modern coral samples and meteorological information. Although it is normal for the survey area to receive a significant amount of rainfall in the winter, the coral data suggests that, during the time of the empire’s collapse, the area suffered from significant dry spells. The data before and since the collapse are furthermore comparable to modern coral data, showing the dry spells would have been sudden and intense.

The fossil evidence shows that there was a prolonged winter shamal season accompanied by frequent shamal days. The impact of the dust storms and the lack of rainfall would have caused major agricultural problems possibly leading to social instability and famine, both factors which have been previously associated with the collapse of the empire.

“Although the official mark of the collapse of the Akkadian Empire is the invasion of Mesopotamia by other populations, our fossil samples are windows in time showing that variations in climate significantly contributed to the empire’s decline,” said lead-author Tsuyoshi Watanabe.

[1] Watanabe et al: Oman corals suggest that a stronger winter shamal season caused the Akkadian Empire (Mesopotamia) collapse in Geology - 2019