Snowfall in Namibia

The borders of modern Namibia were drawn up on a map at the Berlin conference of 1884, named of South West Africa, and given to Germany as a colony. The germans ruled it from then until 1915, when it was invaded by South African troops during the First World War.

Namibia. The sticky-out bit at the top (Caprivi Strip) was because the Kaiser (german king) wanted his colony to have a view of Victoria Falls.

During the period 1884-1915 the Germans built farms, exploited the county's vast mineral wealth, and drove the indigenous population off the land wherever possible. Many settlers arrived during this period and they did their best to re-create their homes, building faithful reproductions of german houses in the deserts of southern Africa. Many of these buildings followed the traditional style of the German Alps, with steep roofs to prevent the snow piling up, something of a rarity in the area, but a popular tourist attraction a century later.

A row of historic shops in Windhoek, Namibia, with steep roofs to prevent snow accumulation, combined with an open bar on the roof of one building.

In June this year (2011), snow did indeed fall in Namibia. Images of this snow quickly made their way onto the internet, leading to much speculation around the globe, and the emergence of some interesting theories online, which can be quickly ran through.

1) This is a sign that the end of the world is immanent, as prophesied in the Book of Revelations. Basically we're all doomed, though there are a few religious organizations (or at least organizations which claim to be religious) offering salvation in return for large, and prompt, cash donations.

2) This is a sign that the end of the world is immanent, as prophesied in the writings of the ancient Mayans. Unfortunately the ancient Mayan priestly class are no longer with us, so it is unclear if they could have offered salvation in return for cash, or anything else. What we do know of their religion suggests that they may have thought a human sacrifice on top of a large pyramid was worth a go.

3) This is a sign of global warming, normal weather patterns are breaking down and freak weather events are becoming more likely. This is certainly a lot more plausible than either of the previous explanations, and there certainly has been an increase in freak weather conditions in the last few years, which may well be linked to global warming. Yet while climate models used to predict the outcome of various warming scenarios do predict a wide range of extreme weather events becoming more common, I am not aware of any that predict snowfall in the Namib Desert. From a scientific viewpoint just saying 'more freak weather' conditions is not very satisfying, this is just invoking the bogeyman to explain anything we don't have an answer for; as a scientist one should look for more direct explanations.

4) This is a sign that global warming is not happening, all climate science is complete hogwash, and we cannot predict the weather in any meaningful way. There will always be weather events that happen outside our expectations, and we should stop worrying about it. This is more of a political viewpoint than a scientific explanation, it rejects an explanation that its adherents do not like, but offers no explanation for events, indeed it rejects the idea that we should look for explanations - profoundly unscientific.

5) It snows in Namibia, this is not a freak weather event, but an uncommon one, entirely within Namibia's normal conditions.

Actually it does snow in Namibia from time to time (the last snowfall was in 2006), but this is a rare event. and there is only ever a light sprinkling, never enough to collapse anybody's roof. Namibia has a subtropical climate with two seasons; a short, hot, wet season, and a longer, cooler, dry season. The wet season is to hot for snow, and the cool season far to dry (and as a rule, still to warm). So the snow still needs a bit of an explanation.

The snowfall in Namibia, not actually that dramatic.


So if snow in Namibia is an unusual event that requires an explanation, then it is logical to look for other unusual events that happen at roughly the same time. This year has seen a number of dramatic weather events, from floods in Australia to tornadoes in New England, but these are effects rather than causes, and, unlike the Namibian snow, they are all events that have been predicted by the models of climatologists studying global warming. There have also been earthquakes in Japan and New Zealand, but again it is difficult to see how these could cause snow in Namibia.

More interestingly there have been two significant volcanic eruptions this year; Grímsvötn in Iceland and Puyehue kin Chile. Grímsvötn is in the northern hemisphere, too far from Namibia to have had any significant effect on the climate, but Puyehue is ideally placed to cause precipitation in southern Africa.

Volcanoes are not obviously wet objects. We associate them with ash and heat, but volcanic plumes actually contain a considerable amount of water vapor. The volcanoes of South America are fed by the subduction of the Pacific Plate beneath the South American Plate. As the waterlogged sea-floor is pushed deeper it is warmed by the internal heat of the Earth. This eventually forces the water out of the sinking crust, and it rises up through the overlying South American Plate, carrying superheated liquid rock with it. Eventually it emerges in the Andes, forming volcanoes such as Puyehue. This superheated water vapor explodes far into the atmosphere, carrying the more obvious volcanic ash with it (gaseous water vapor is invisible). Once this reaches the upper atmosphere it is carried eastward by the Earth's motion (the ground rotates more rapidly than the upper atmosphere, so anything in the upper atmosphere is carried eastward). The majority of the Puyehue plume has passed to the south of Africa, eventually traveling round the world to disrupt air travel in Australia and New Zealand, but enough material has spread over southern Africa to have an effect (there has been snowfall in South Africa as well, but this is less unusual, and so has escaped comment). In addition to the water vapor the volcano will have produced significant amounts of sulphur dioxide (SO₂) into the upper atmosphere. This (in addition to other effects) acts as a cooling agent, facilitating but not guaranteeing snowfall.

As a theory this is all very well, but to make a strong association between volcanoes in South America and snow in Namibia we would need more than one example. The last time it snowed in Namibia was in February 2006, this time during what should have been the warmer season. This was a month after the onset of volcanic activity at Galeras Volcano in Chile, hundreds of kilometers to the north of Puyehue.

An areal photograph of the Galeras caldera. To the lower right a smaller plume comes from a fumarole, a small vent through which only gas escapes.

Unfortunately I do not have details of every recorded snowfall in Namibia at my fingertips, so I am unable to check them against volcanic eruptions in South America, however the small sample have been able to check suggests that snow in Namibia is usually preceded by volcanic eruptions in South America, although the reverse is not true; not every volcanic eruption in South America leads to snowfall in Namibia.

See also The Puyehue-Cordón Caulle Volcanic Complex,
The Puyehue Eruption, Chile, 2011.

The Puyehue Eruption, Chile, 2011.

Puyehue is a stratocone volcano (i.e. a cone-shaped volcano of the kind seen in Hollywood movies) in central Chile. It forms part of the Puyehue-Cordón Caulle Volcanic Complex, along with the Cordón Caulle volcanic fissure and Cordillera Nevada caldera. Puyehue began erupting on June 3rd this year, the complex having been dormant since 1960, when, following an earthquake with a magnitude of 9.5 on the Richter scale (the largest earthquake ever recorded), the Cordón Caulle fissure erupted throwing ash eight kilometers into the air.

See The Puyehue-Cordón Caulle Volcanic Complex.

It is not clear what part of the volcanic complex the eruption occurred in - the complex is rather remote - it could be Puyehue itself or the Cordón-Caulle fissure. There has been an evacuation of the immediate area, although it is unclear what proportion of the population has actually left.

The ash cloud is proving to be far more disruptive than the volcano itself; this has caused heavy ash-falls in neighboring Argentina and Uruguay, leading to power failures as ash settles on power lines and brings them down, as well as the closure of airports in all three countries. The Argentine army has been dispensed to the area to help with the clean-up operation.

From South America the ash-cloud has spread east across the southern ocean (ash clouds entering the upper atmosphere always spread to the east, as this part of the atmosphere does not rotate as fast as the solid Earth; effectively the ash stays still while the planet moves beneath it), missing the tip of Africa then arriving in South East Australia and New Zealand, where it is causing considerable disruption to air traffic. Most airlines affected have agreed to follow guidelines and remain grounded while the crisis lasts, but worryingly Air New Zealand appear to be following the lead of British and Irish airlines and are proposing to fly during the crisis, hoping to dodge the ash clouds. Volcanic ash is particularly dangerous to jet aircraft as the fine ash can melt inside the hot engines, coating their innards with volcanic glass.

Satellite image showing the progress of ash from the Puyehue eruption (false coloured in yellow) around the southern hemisphere.

In addition to the ash cloud a pyroclastic flow (avalanche of hot volcanic material) has apparently reached the Nilahue River, raising the temperature from 10°C to 45°C and causing a mass die-off of salmon. Other rivers in the area are reported to be partially blocked by ash, leading to some flooding of farmland; there are no reports of any urban areas being threatened, nor have there been any reports of loss of life directly connected to the volcano.

The volcanic cloud has produced some spectacular lightning displays. These occur when convection currents in within the cloud carry particles with different charges apart; eventually the charge differential becomes to great and an electric discharge occurs.

See also The Grímsvöten Volcano and
Volcanos on Sciency Thoughts YouTube

The Puyehue-Cordón Caulle Volcanic Complex

The Puyehue-Cordón Caulle Volcanic Complex is in southern Chile, about 450 miles south of the capital Santiago, and about 20 miles west of the Argentine border. Chile has about 3000 volcanoes running from north to south along the whole length of the country, which about 80 are still periodically active. These occur as the Nazca Plate (part of the Pacific sea floor) is forced below the South American Plate; the South American plate is lifted up, forming the Andes Mountains, as the Pacific Plate is subducted into the Earth's mantle lighter minerals are melted and bubble up to the surface, creating a string of volcanoes throughout the Andes. The Andes are among the fastest growing mountains on Earth, and were where mountain orogeny (the growth of mountains) was first understood.


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The Puyehue-Cordón Caulle Volcanic Complex lies on the Liquiñe-Ofqui Fault, where the Nazca, South American and Antarctic Plates collide, an area of intense volcanic activity. The Puyehue-Cordón Caulle Volcanic Complex itself is between 200 000 and 300 000 when a shift in the fault shifted to the east and narrowed. A series of older volcanoes to the east all ceased activity at this time, and were replaced by younger larger volcanoes such as Puyehue-Cordón.

Technically Puyehue is a stratocone volcano, i.e. a classic cone-shaped volcano, whereas Cordón Cauelle is an adjacent volcanic fissure. The volcanic complex is very active, with a record of observed eruptions going back to 1759 when the first permanent European settlements in the area were established. There were nine eruptions during the twentieth century, including one in 1960 associated with the May 22 Valdivia earthquake, the most powerful earthquake ever recorded.

The complex began to erupt again on the 4th of June this year (2011), an eruption accompanied by a swarm of earthquakes and throwing an ash-cloud high into the air. It is not yet clear if this originates from the Puyehue stratocone or the Cordón Cauelle fissure, due to the remote location of the complex, within the Puyehue National Park and the fact that it is mid-winter in the southern hemisphere in June.

The Chilean government has responded by ordering the evacuation of around 3000 people from the area around the volcano, although it is unclear how many people have actually left; the raising livestock is an important part of the local economy and people are often reluctant to leave their animals.

The ash cloud has blown eastward over Argentina where two small airports servicing ski resorts among the extinct volcanoes of the eastern Liquiñe-Ofqui. Unlike British and Irish airlines, Argentine ones seem happy to accept that volcanic ash-clouds are dangerous to aircraft.



See also The Puyehue Eruption, Chile, 2011.
The Grímsvöten Volcano and
Volcanos on Sciency Thoughts YouTube