Do you know, why you feel warm when standing in direct sunlight on a winter morning? The answer lies in the infrared radiations, which are absorbed by the surface of the Earth as visible light. About 70% of the solar radiation reaches the Earth through the atmosphere, of which a huge chunk of infrared radiation is absorbed by the Earth's surface, and some is reflected back into the atmosphere. 15-30% of this is transmitted through the atmosphere and the rest 70-85% is reflected again on Earth's surface, further increasing the temperature.
Now, this is precisely what happens in a greenhouse (which is more often made of glass): the transparent medium (glass) lets the higher wavelength light rays to pass through, of which some of the radiations get absorbed by the Earth's surface and the rest are reflected back into the atmosphere within, due to which the atmosphere remains warm inside.
The radiations that are trapped inside a glass house cannot escape the medium and are further absorbed by certain gases (like carbon dioxide, released from plants) within the greenhouse, which are known as the greenhouse gases. These infrared radiations that are absorbed bend and vibrate the chemical bonding of the gas molecules and they in turn gain more momentum, where the kinetic energy is transmitted to other gas molecules, causing the general heating of the Earth's atmosphere. Similarly, in the atmosphere outside, these gases form a blanket by absorbing the infrared radiations, thereby increasing the temperature of the Earth.
- Water vapor (produced due to constant evaporation of water and sublimation of ice, constitutes about 33-66% of these gases)
- Carbon dioxide (released by burning of wood, fossils, organic matter, respiration in animals and plants; constitutes about 9-26% of greenhouse gases)
- Methane (released by decomposition of organic matter, production and transport of fossil fuel, constitutes about 4-9%, hence methane and global warming are closely connected)
- Nitrous oxide (emitted during various industrial and agricultural processes that involve burning of fossil fuels)
- Fluorinated gases (emitted by electrical appliances and these emissions contain chlorine and bromine)
- Other gases (like sulfur hexafluoride, hydrofluorocarbons, nitrogen trifluoride and perfluorocarbons)
There has been a significant climate change in the past few decades. This also relates well to the fact that illustrates the rising levels of carbon dioxide in the atmosphere. Then there are other significant changes too like changing weather patterns and rising sea levels, with an increased frequency of hurricanes and typhoons. And all of this boils down to one term: Global warming, a continual increase in the average temperature of the air near the earth's surface. So what causes it? Increasing greenhouse gases!
For instance, a molecule of methane, absorbs about 21 times more heat than what one molecule of carbon dioxide can absorb. Similarly, a nitrous oxide molecule absorbs about 270 times more heat than every molecule of carbon dioxide. With so much heat generated in the atmosphere, following are the effects of global warming:
- The increased temperatures are melting the ice beds of Earth, i.e., the Arctic and the Antarctic. The ice here has started melting at a faster rate than ever. This phenomenon is also evident in the mountains, where melting glaciers are one of the prime reason for increasing sea levels.
- A substantial decrease in the population of Adelie penguins of Antarctica, from 32000 to 11000 in the last three decades is a proof indicating a rapid global warming.
- Rising sea levels (further expected to rise up to 23 inches by the end of this century), increased precipitation and heightened ferocity of storms are added impacts of greenhouse gases on global warming.
- Animals have already started migrating to higher and cooler areas as they are always the ones, who sense any further impinging of global warming.
- Ozone depletion is also directly proportional to the rate of global warming. Because these gases trap the heat in the troposphere layer of atmosphere, very less heat is radiated into the stratosphere, which makes this atmospheric layer colder, thereby accelerating the ozone layer depletion. And the consequences of this ozone layer depletion can severely disturb the ecological balance and also increase human's susceptibility to infections.
Most of the greenhouse gas emissions are man-made. Environmental pollution, deforestation, using electrical appliances (like refrigerators) that emit fluorinated gases, combustion of fossils and coal and combustion in automobiles add on to the influx of gases into the atmosphere, which are some of the major causes of the greenhouse effect. It is estimated that with the ongoing global warming, floods, droughts, disrupted ecological balance, and outbreak of diseases should not be surprising in future. We need to work out ways to reduce the emissions, if not stop them.
Emission of gases into the atmosphere can also be closely related to the butterfly effect, a metaphor which illustrates the sensitive dependence of an event on the initial conditions that factor an environment. Rising sea levels may not be a sudden effect, but the consequences may be too cataclysmic to comprehend. So, it is the responsibility of every individual to work towards reducing emission of greenhouse gases into the atmosphere to save our beautiful planet from deteriorating.