Sometime ago, a warning endorsed by more than 1,600 of the world’s most distinguished scientists, including 102 Nobel Prize winner states in part:
Human being and the natural world are on collision course. Human activities inflict harsh and often irreversible damaged on the environment and critical resources. If not checked, many of our current practices put as serious risk the future that we wish for human society and the plant and animal kingdoms, and may so alter the living world that it will be unable to sustain life in the manner we know. Fundamental changes are urgent if we are to avoid the collision our present course will bring about.
Two of the potentially disastrous phenomena are global warming and ozone layer depletion. In a national study conducted in 1995, it was found that less than 5% of Nigerians surveyed know the causes and consequences of global warming and ozone layer depletion. The intent of this series is to enhance public understanding of the two phenomena with a view to mobilising local and national action in taking corrective actions.
The presentation begins with a look at the atmosphere, since is where the action is in discussions on global warming and ozone layer depletion and anchors with suggestions for local, national and global action.
The Earth and other planets of the solar system are each enclosed in a thin shell of gas called the atmosphere. If the Earth is compared to an orange, the atmosphere can be considered the skin of the orange.
Layers of the atmosphere
Scientists have developed three different classification systems for the atmosphere on the basis of (a) Varying temperature, (b) varying electrical characteristics, and (c) varying composition.
On the basis of temperature, scientists distinguish five layers. The troposphere, stratosphere, mesosphere, exosphere, thermosphere.
Scientists also divided the atmosphere into layers on the basis of electrical properties. Overall, they recognise a neutral atmosphere, which lies below about 60km, and the ionosphere above it. The ionosphere, a region of electrically charged particles of ions may be divided into regions according to the degree of ionisation. Beyond its outer boundary is the magnetosphere, a magnetic envelope that shelters the Earth from the ionised blast of the solar wind.
Composition in the lower regions of the atmosphere; up to about 100 kilometres above the Earth, turbulence causes a continuous mixing of the constituent elements of the atmosphere so that the composition is relatively uniform. These regions make up the homosphere. Above this is the heterosphere. Where various constituents tend to separate out, the concentrations of heavier elements, such as nitrogen and oxygen, decrease with increasing altitude, so that eventually the atmosphere is dominated by the lighter elements, such as helium and hydrogen. At the outermost part of the ionosphere, helium becomes dominant at about 960 kilometres, and hydrogen above about 2,500 kilometres.
GREENHOUSE EFFECT AND GLOBAL WARMING
The glass-roofed structure in which plants are gown is called a greenhouse. Usually the walls are also made of glass. A greenhouse creates an artificial environment (a steady-state climate) by careful control of temperature, light, humidity, air quality, soil moisture, and heat levels. Most greenhouses are either commercial business for raising and selling flowers, vegetables and other plants, or experimental agricultural laboratories. A properly situated greenhouse depends on the average weather conditions in the area. Heating is usually by hot water, steam, or hot-air systems. Ventilation, either by fans or vents, circulates the air, controls its quality and prevents overheating.
The glass windows of a greenhouse let in sunlight. The Sunlight warms up objects inside the greenhouse. These...