In our lower atmosphere, the troposphere, the ‘greenhouse’ gases act like the glasses in the greenhouse; in the day time the sun shines through the atmosphere and warms the Earth's surface and then, at night, as the Earth cools, the heat is released back into the air. Not all the warmed air can escape back into space because some of it gets ‘trapped’ in the ‘greenhouse’ gases. The more greenhouse gases in the atmosphere, the more warm air becomes trapped, thereby increasing the Earth's global temperature.
Just as the glasses of a greenhouse that allow the sunlight to go through but not the infrared radiation emitted by the warmed surfaces within, so certain atmospheric gases, known collectively as greenhouse gases (e.g. carbon dioxide and nitrous oxide), allow sunlight, especially as ultraviolet, to pass unimpeded, but keep heat from escaping because the greenhouse gases absorb the infrared radiation emitted from the Earth's surface.
The atmospheric concentration of greenhouse gasses has increased by more than 15% in the last hundred years mainly due to the burning of fossil fuels, coal and oil, and this, combined with unprecedented global deforestation, is leading to a continued increase in the concentration of carbon dioxide in the atmosphere.
The Earth's average temperature is currently around 59 degrees Farenheit, with some areas much colder (at the north and south poles) and some, as in sub Saharan Africa, considerably hotter. In the last one hundred and fifty years or so, since the onset of industrialisation and the discovery of oil, increased concentrations, of more than 15%, of atmospheric pollutants have been released into the air with the result that the average global temperature has risen by 1.8F at that time.
There is no doubt that for life to exist on Earth, we need the greenhouse effect to some extent because the Earth's oceans would be frozen without it. But an excessive amount of greenhouse gases in the atmosphere will have the opposite effect: rising temperatures will cause the sea levels to rise and the deserts to cover more areas of the planet.
Global temperatures are increasing, glaciers are melting, sea levels are rising, cloud forests are drying, weather patterns are changing, the number of natural disasters is increasing, deserts are spreading and the world’s wildlife and biodiversity are struggling, and in many cases, many species fail to adapt to the changes. It has become clear that humans have caused most of the past century's warming by releasing heat-trapping gases to provide the energy for the global development of ‘civilization’. The greenhouse gases in our atmosphere are now at a higher level than at any time within last 650,000 years and they are rising by the minute.
We, human kind, have only been around for the last 100,000 years or so, and we have never, ever, lived in an atmosphere such as the one that we have now. Whether we manage to adapt, or fail and become extinct, remains to be seen……
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