olelog

To understand the future, we have to understand the past is a motto often repeated by geologists.

Can we learn anything about the climate today from the Great Oxidation Event around 2450–2200 million years ago and a second increase in atmospheric oxygen that appears to have taken place in distinct stages during the late Neoproterozoic era (approximately 800–542 million years ago).

In other words which role does atmospheric oxygen content play in global warming? This question has become extremely relevant now that Professor Robert Frei from the University of Copenhagen, in collaboration with colleagues from Uruguay, England and the University of Southern Denmark, has established that there is a historical correlation between oxygen and temperature fluctuations towards global cooling.

They conclude that high oxygen content in seawater enables a lot of life in the oceans "consuming" the greenhouse gas CO2, which subsequently leads to a cooling of the earth's surface. Throughout history our climate has been dependent on balance between CO2 and atmospheric oxygen. The more CO2 and other greenhouse gases, the warmer the climate has been.

The findings do not mean that we cannot do anything to slow down the current global warming trend. For example by increased forestry and other initiatives that help to increase atmospheric and oceanic oxygen levels.

• http://www.nature.com/nature/journal/v461/n7261/full/nature08266.html
  
• http://www.eurekalert.org/pub_releases/2009-09/uoc-mo090809.php
  
• http://www.sciencecodex.com/more_oxygen_colder_climate
  
• http://www.redorbit.com/news/science/1750652/ancient_oceans_give_new_insight_into_the_origins_of_animal/index.html?source=r_science
  

In Danish:

• http://www.ku.dk/nyheder/?content=%2Fnyheder%2Fvis_indlaeg.asp%3Ftype%3D1%26amp%3Bid%3D8670%26amp%3Bref%3D0
  
• http://borsen.dk/fodevarer/nyhed/165457/newsfeeds_rss/
  
• http://www.videnskab.dk/composite-2930.htm
  
• http://ing.dk/artikel/102276-jorden-fik-pludselig-iltmangel-for-19-milliarder-aar-siden?utm_medium=rss&utm_campaign=nyheder
  

Let me concentrate myself on two deserts - the driest and the oldest in the world - the Atacama Desert in South America and the Namib Desert in Southern Africa. Unlike for instance the Gobi desert, that is so far away from the sea that the water can’t make it that far and so it falls before arriving to the desert, they are both situated next to a large ocean.

To understand why these two deserts are where they are we need a bit of elementary oceanography. I suppose the coriolis effect is more or less well known. It makes ocean currents curve to the right (clockwise) in the northern hemisphere and to the left (counter-clockwise) in the southern hemisphere. This way it forms large circular ocean currents known as gyres. This map shows the 5 largest ocean gyres in the world.

Please notice in particular the South Atlantic Subtropical Gyre and the South Pacific Subtropical Gyre. Currents flowing from equator towards the poles will be warm currents (like the Gulf Stream). Currents flowing towards the equator will be cold. Due to the ocean gyres a cold current is flowing northwards along the west coast of Chile - the cold Humboldt current (also known as Peru Current). Likewise a cold current is flowing northwards along the west coast of Namibia - the cold Benguela current.

And this leads us to what is possibly the driest place on on earth (actually another outstanding candidate for this honour is a low spot in the Lut Desert of eastern Iran). The Atacama Desert is a virtually rainless plateau in South America, extending nearly 1000 km between the Andes mountains and the Pacific Ocean. Parts of Chile's Atacama Desert haven't seen a drop of rain since record-keeping began. Here a place called Arica gets just 0.76 millimetres of rain per year. At that rate, it would take a century to fill a coffee cup (not even a tee cup for my dear British readers). The precipitation (moisture equivalent to rain) in Atacama averages less than 1 centimetre per year from fog. Measurable rainfall (more than a millimetre of rain) occurs every five to 20 years and heavy rains fall only two to four times a century. No vegetation grows here. It is what is termed ‘absolute desert’.

The desert is to a great extent created by the cold Humboldt current. A great mass of ice cold water surges out of the Antarctic Ocean and flows north along the South American continental shelf. The shallowing land forces the cold deep waters up to the sea surface where the waters may encounter warm winds that blow land-ward. The warm air cools as it moves across the cold current and the air becomes too cold to hold much moisture. No rain clouds, therefore, can reach the coast and the land dries into a hostile area for life. In the winter, fog rises from the upwelling cold currents, blankets the desert, and gives moisture to the land. The mountain ranges also play a role. The Atacama is blocked from moisture on both sides by the Andes mountains to the east and by coastal mountains to the west. The trade winds blow westward on the east side of the Andes, but the desert lies in the rain shadow of the Andes.

I would indeed like to compare the situation with the Namib Desert and the cold Benguela current in Southern Africa. The Namib Desert is considered to be the oldest desert in the world, having endured arid or semi-arid conditions for at least 55 million years. Its aridity is caused by the descent of dry air cooled by the cold Benguela current along the coast. It has less than 10 mm of rain annually and is almost completely barren. The cold waters of the north-flowing Benguela current move from the western coast of South Africa and Namibia towards north and Northwest up to the line where it joins the southern equatorial current which is a warm current. Its waters are cold because there are very deep waters that were brought upward due to the rotation of Earth from west to east. This upward movement of deep waters are sometimes increased by southern Trade winds which blow west from the Kalahari Desert towards the ocean. The cold current creates the desert conditions of the shore of Namibia, and the persistent fogs of the Skeleton Coast.

That these two deserts are both located at the same southern latitude (trade wind zone) on the west coast of a large continent is no coincidence. The Tropic of Capricorn passes through both deserts.

Deserts can, by the way, be classified by their geographical location and dominant weather pattern as trade wind, mid-latitude, rain shadow, coastal, monsoon, or polar deserts. The Atacama Desert covers three of these categories: trade wind, mid-latitude, and coastal.

This is a special post written for the the sixth Carnival of the Arid coming up soon at Coyote Crossing. I’ll give you the URL here in due time...

... and here it comes:

• http://faultline.org/index.php/site/item/carnival_of_the_arid_6/

go and enjoy it!

Generalized model of the thermohaline circulation: 'Global Conveyor Belt'. This illustration (from NASA) shows cold deep high salinity currents circulating from the north Atlantic Ocean to the southern Atlantic Ocean and east to the Indian Ocean. Deep water returns to the surface in the Indian and Pacific Oceans through the process of upwelling. The warm shallow current then returns west past the Indian Ocean, round South Africa and up to the North Atlantic where the water becomes saltier and colder and sinks starting the process all over again.

According to a 50-year-old model of ocean currents the Labrador Current is a southbound subsurface flow of cold water forming a continuous loop with the familiar northbound flow of warm water on the surface, called the Gulf Stream.


This model of North Atlantic currents as shown in the diagram here below from a press release from Duke University has been called into question by new data from Duke University and the Woods Hole Oceanographic Institution.


The following is primarily based on the press release from the Duke University, but the real thing is of course the relevant paper of 14 May 2009 in the journal Nature.

Climatologists pay attention to the Labrador Sea because it is one of the starting points of a global circulation pattern that transports cold northern water south to make the tropics a little cooler and then returns warm water at the surface, via the Gulf Stream, to moderate temperatures of northern Europe.

Oceanographers long thought the Labrador seawater moved south along what is called the Deep Western Boundary Current (DWBC), which hugs the eastern North American continental shelf all the way to near Florida and then continues further south.


But studies in the 1990s using submersible floats that followed underwater currents "showed little evidence of southbound export of Labrador sea water within the Deep Western Boundary Current (DWBC).

Lozier and Bower launched 76 special Range and Fixing of Sound floats into the current south of the Labrador Sea between 2003 and 2006. Those "RAFOS" floats could stay submerged at 700 or 1,500 m depth and still communicate their data for a range of about 1,000 km using a network of special low frequency and amplitude seismic signals.

Only 8 percent of the RAFOS floats' followed the conveyor belt of the Deep Western Boundary Current. About 75 percent of them escaped that coast-hugging deep underwater pathway and instead drifted into the open ocean by the time they rounded the southern tail of the Grand Banks.

The new float observations and simulated float trajectories provide evidence that the southward interior pathway is more important for the transport of Labrador Sea Water through the subtropics than the DWBC, contrary to previous thinking,

• http://news.duke.edu/2009/05/conveyor.html
• http://www.nature.com/nature/journal/v459/n7244/abs/nature07979.html
• http://www.eurekalert.org/pub_releases/2009-05/whoi-sfs051309.php
• http://www.eurekalert.org/pub_releases/2009-05/du-cwo051309.php
• http://www.physorg.com/news161439846.html
• http://www.scientificblogging.com/news_articles/climate_change_modeling_complication_ocean_circulation_does_not_work_expected
• http://www.geologytimes.com/research/Cold_water_ocean_circulation_doesnt_work_as_expected.asp

Climate, Wars, Economics, and Pirates

First let us get things straight. Human beings lived in Africa long before Europe was populated. In other words the history of Africa didn’t start with the European colonisation of Africa. Neither is culture a European monopoly.

From the 25th century BC and onwards the Egyptians sent expeditions to the land of Punt, which is supposed to have been the Horn of Africa. If so a lot of things have changed since then, as the Land of Punt was known for producing and exporting gold, aromatic resins, African blackwood, ebony, ivory, slaves and wild animals.

Somalia became independent in 1960. It has been tormented by crude civil war most of the time since 1986. UN humanitarian troops landed in 1993 and started a two-year effort (primarily in the south) to alleviate famine conditions. The period of 1998–2006 saw the declaration of a number of self-declared autonomous states within Somalia. In January 2009, Ethiopian troops withdrew from Somalia following a two year insurgency. In short their is practical no law and order and the central Somalian government has little to say.

Today 85% of the population are Somalis, a population that CIA estimates at nearly 10 million people (another source says 4 million in 1979). The Somalis began populating the area around 1000 years ago. About 70 percent of all Somalis are nomads who travel with their herds through Somalia, Kenya, and Ethiopia. Today more than 3 million Somalis are dependant on food aid and 1.3 million are fugitives.

Only 1.64% of Somalia’s 637 657 km² is arable land with permanent crops on 0.04% of Somalia. Most of the country receives less than 500 millimeters of rain annually, and a large area encompassing the northeast and much of northern Somalia receives as little as 50 to 150 millimeters. One of the country’s biggest problem is the heavy loss of livestock suffered by the pastoralist communities in the worst drought in 30 years.

Somali has a 3,025 km long coastline. In 2005 ca. 700 foreign fishing trawlers were illegally active in Somalian waters. For years other countries have dumped nuclear and toxic waste off the coast of Somalia. After the tsunami in 2005 some of this waste washed ashore with disastrous results for the coastal population like skin diseases and mouth bleedings.

So what can you do in Somalia for a living. Crops gone, livestock gone, fish gone, and no social security. One solution is taking aid helpers as hostages to get ransom money. It has been done lately. There is however bigger money in piracy. And the pirates are local heroes. They are the revengers of those foreigners that destroyed the fishing industry and they provide money.

Eyl in Puntland is the location of most of Somalia's casualties from the 2004 Indian Ocean Tsunami. It has about 3 million inhabitants and has become something like the capital of the Somalian pirates. As the so-called pirate capital it is where the high seas hijackers often steer their captured vessels. Special restaurants in the town cater for the captive crews. With their expensive tastes in fancy houses, cars and women, the pirates have brought boom times to the local economy. The Puntland government has acknowledged that they are relatively powerless to stop pirate activities.

To recapitulate: Somalia is one of the poorest, most violent, least stable countries anywhere on Earth. It suffers from severe drought and its people face hunger and violence on a daily basis.

How can you stop the piracy. Much is said these days about warships and other military or paramilitary actions. No doubt such things are necessary. But without improving the humanitarian situation for all Somalis, the problem will not be solved. This is an extremely difficult task for the international community.

I wonder if the international conference held these days in Brussels, and sponsored by the United Nations and the European Union, that aims to raise at least euro128 million ($166 million) in donations for Somalia's nascent security forces and for the African Union peacekeeping contingent there, leads to any decisive results.

• http://www.time.com/time/world/article/0,8599,1892376,00.html
• http://www.latimes.com/news/nationworld/world/la-fg-somalia-pirates15-2009apr15,0,165660.story

See also my post: http://my.opera.com/nielsol/blog/2009/04/20/floods-in-somaliland

The flooding along the upper Zambezi river and its tributaries is the worst since 1969. Flooding in the upper Zambezi river basin has already displaced hundreds of thousands in Angola, Namibia and Zambia. Zambia's air force began airlifting relief supplies on Friday 27 march. Namibia has declared a state of emergency. At least 100 people have died. Crocodiles and hippos are swimming through the flood waters, attacking and killing people. Field after field of crops have been destroyed, as have houses, schools, health centres and roads. More than 20 000 families have been displaced.


The waters of the Okavango delta in Botswana have reached their highest levels since 1939.

In Angola the flooding has affected more than 200 000 people . So far at least 20 people are dead.

The north of the Zambezi basin has mean annual rainfall of 1100 to 1400 mm which declines towards the south, reaching about half that figure in the south-west. The rain falls in a 4 to 6 month rainy season when the Inter-Tropical Convergence Zone moves over the basin from the north. The Inter-Tropical Convergence Zone, or ITCZ, is a region that circles the Earth, near the equator, where the trade winds of the Northern and Southern Hemispheres come together. The intense sun and warm water of the equator heats the air in the ITCZ, raising its humidity and causing it to rise. As the air rises it cools, releasing the accumulated moisture in an almost perpetual series of thunderstorms.

• http://www.terradaily.com/reports/Rain-soaked_southern_Africa_hit_by_worst_floods_in_years_999.html
• http://www.reuters.com/article/unitedNations/idUSLR643933

PS of 31 March 2009:
There are now new satellite images and more information at NASA's Earth Observatory.