Pelican airlift in Etosha
July 29, 2016
A story etched in vegetable ivory
August 2, 2016
Text by Hu Berry | Main photo ©Paul van Schalkwyk
On a frosty winter morning there is no wind over the Khomas Hochland in central Namibia. Rising over 2 000 metres into the atmosphere, this plateau was elevated hundreds of millions of years ago during the turbulent birth of Africa. Today, with its deeply incised valleys, it is where the wind of the day gains its strength.
N urtured by high-pressure cells that formed over the Kalahari Desert far to the east, the wind begins to drift across the undulating mountain savannah. Silver grasses that stood motionless under the starlight chill, begin swaying in rhythm with the infant wind as it gains vigour, flowing westwards to the abrupt rim of the Kalahari Basin. Below the ragged lip of the escarpment lies the Namib Desert, still cold from the frequent fogs that are carried inland from the icy Benguela Current.
As the wind descends the slopes, it undergoes a drastic transformation. Immutable laws of physics dictate that for every 100 metres it loses in altitude, it will gain 10C in temperature. In addition, the scant wintry moisture it contains is sucked away until the air becomes brittle and dry. After a relentless descent of more than 2 000 metres, the altered wind arrives at the Namib coast with desiccating dryness and temperatures of up to 400C. Coastal residents look up knowingly at the dust-laden skies and pronounce that the Ostwind (east wind) has arrived. In this strangest of all coastal deserts, winter temperatures are often higher than in the fog-drenched summers.
Wind is air in motion, but how do we define air, this invisible, essential agent of life? Held tightly against the earth’s surface by gravity, our atmosphere delivers exactly the right balance of gases to sustain life, in the proportion of 78% nitrogen and 21% oxygen. Traces of other gases, infused with water vapour, constitute the remaining 1%. Unfortunately, one of them, carbon dioxide, weighs heavily on the earth (and on our minds). This ubiquitous gas has reached levels that led prominent scientists to coin the phrase ‘crashing climate’.
An ominous warning about the 9.8 Gigatonnes (nearly 10 thousand million tonnes) of C02 that our industries, aircraft, automobiles and homes spew into the air every year came from the International Energy Agency, Washington DC in 2006. It reminds us that climate change has been a real threat for some time now.
Based on indisputable research, we are informed that the earth’s surface temperatures are most likely the warmest they’ve been in the past million years. Humans haven’t lived in a world this warm before, and we simply don’t know, since we’ve never been there before, what the ‘tipping point’ will be. When the environmental decay we are causing gives way to sudden and self-perpetuating collapse of ecosystems, we will know, but it will be too late. Pump sufficient carbon dioxide into the sky and it may behave like the 100th degree Celsius, which turns hot water into steam. If the Antarctic ice were to melt, it would yield enough water to raise sea levels more than 65 metres, according to the United States National Centre for Atmospheric Research in Colorado. The rare gases remaining have unusual names, derived from Greek, like argon (idle of work), helium (from the sun), hydrogen (water-forming), krypton (hidden) and neon (new).
Spare a thought for the traces of ozone that occur throughout our atmosphere. Derived from the Greek word ozein for the peculiar smell generated in lightning storms, it is produced by ultraviolet rays reacting with oxygen. This makes it an unstable combination of ‘super oxygen’ that magically filters out most of the sun’s harmful ultraviolet rays. Ironically, we humans need them in tiny doses to produce vitamin D. Too little ultraviolet on our skins and our health declines; too much and we develop skin cancer – it’s a fine balance.
The atmosphere provides a protective screen against invisible, but potent solar winds, which speed 150 million kilometres from the sun across the ether in less than 10 minutes. This incoming solar radiation has the energy to destroy all life on earth. Our air shield has no precise cut-off point. It thins and fades away imperceptibly into space. Nevertheless, if a person ascends higher than 100 kilometres, he or she is dubbed an astronaut. Below this altitude we are mere aeronauts. The hazardous, heat-generating re-entry of spaceships becomes noticeable at 120 kilometres, but for general purposes the Karmen line at 100 kilometres altitude is frequently used as the starting point of space.
Strange as it may seem, air has a mass or weight (about 5 000 trillion tons in total), resulting in what we know as air pressure. The density or mass of air at sea level is about 1.2 kg per cubic metre. Nearly two-thirds of this is below the summit of Mount Everest and three-quarters lies beneath the intercontinental jetliners that ply the world’s skyways, 10 kilometres above sea level. In the rarified regions above this, we witness the ghostly effects of the Aurora Borealis or Northern Lights, displaying phantom-like curtains of gas in the heavens of the high latitudes.
Within the 1000C range of extreme temperatures that have been measured on earth, from minus 500 C to plus 500C, our planet has a livable but cool surface average of 140C. Indeed, it is this span of cold and heat that generates the winds that shaped the planet’s surface by aeolian processes. Named after the mythological Greek god of wind, Aeolus, particles such as abrasive sand both erode and leave deposits. Moreover, frost and precipitation of fog, rain and hail persistently pockmark the surface.
As earth enters an uncertain climatic future, we take the knowledge that we are living in the ‘third atmosphere’ with us. The first two atmospheres, formed more than three to four thousand million years ago, were so noxious that present life forms could not exist. If people persist, in their ignorance, to pollute the air, a fourth atmosphere will develop, erasing life as we know it.
Namibia fortunately boasts one of the cleanest atmospheres in the world. Let us hope that the clean, cold, air that pervades the wintry Namibian nights and the hot desert winds remain as pure as they are at present.
This article was first published in the Flamingo March 2007 issue. (Information has been adapted accordingly)
