26 ENVIRONMENT AND ENERGY
NASA
Satellite imagery illustrating the nesting of humans — essentially drawn to the cities . vertically upwards from the Earths ’ surface to an average height of roughly 12 – 13 kilometres — at the poles , roughly nine kilometres and at the equator , some 17 kilometres , with the average thickness being around 13 kilometres . That is one of the reasons why airlines fly at similar altitudes / flight levels , to avoid weather build-up en route .
Again , this layer [ the troposphere ] is not very thick and can be represented by a slightly thicker film of commercial-grade cling wrap wrapped around the soccer ball .
Nearly all the atmospheric water vapour is found in the troposphere . Water vapour is an invisible gas , and when a mass of air containing sufficient water vapour is cooled adiabatically by various natural trigger actions to its saturation temperature , clouds will form and then there is a possibility that precipitation will take place .
Now if we tamper with and pollute this miniscule layer of weather-producing atmosphere , then indeed rainfall patterns and the areas within which it rains will change too ; the climate will essentially change . The difference between weather and climate is time based . Weather is what conditions exist in
the atmosphere over a short period of time , while climate in a defined region is the way the atmosphere behaves over a protracted or extended time period .
Global temperature patterns and variations of temperatures over the surface of the earth determine pressure patterns and , therefore , weather patterns in certain regions . So , if we alter and shift the global temperature footprint ( that is , global warming — a complete and separate topic ), then we will alter the rainfall patterns and climate in certain regions , too . Where it used to rain , it will no longer rain and vice versa .
THE HUMAN RACE VIEWED FROM SPACE – MIMICKING NATURE In saying this , I do not mean to insult anyone , but human beings are like insects : we form densely populated nests on the surface of the Earth . Over the past 50 years , the world population has more than doubled ; hence , the size of the nests / cities have increased exponentially .
Astronauts who have been in orbit regularly over the past 30 years on space shuttle missions like Gemini or Apollo will tell you how they have witnessed this expansion and the changes , especially to the atmosphere . They will tell you that cities seem to have their own atmosphere , possibly due to pollution .
DEFINING DROUGHT The term drought is not easy to define since there are many causal factors that may result in a drought . A simplistic definition of a drought could be “ an insufficient amount of water to meet the demands of a region over an extended time period ”.
There are many conditions that can cause a drought :
• Meteorological : Caused by climatic changes — insufficient precipitation .
• Hydrological : Persistently low volumes in streams , rivers , reservoirs , and groundwater .
June 2018 Volume 24 I Number 4 www . plumbingafrica . co . za