How Does Climate Change (“Global Warming”) Work?
The Mechanism of Global Warming, an Extra Greenhouse Effect
[Or: “Why do some gases concern scientists––like carbon dioxide (CO2)––but not others, like oxygen?”]
by Professor Michael Ranney, Daniel Reinholz, and Dr. Lloyd Goldwasser (with special thanks to Professor Ronald Cohen and the Reasoning Group)
Scientists tell us that human activities are changing Earth’s atmosphere and increasing Earth’s average temperature. What causes these climate changes?
First, let’s understand Earth’s “normal” temperature: When Earth absorbs sunlight, which is mostly visible light, it heats up. Like the sun, Earth emits energy––but because it is cooler than the sun, Earth emits lower-energy infrared wavelengths. Greenhouse gases in the atmosphere (methane, carbon dioxide, etc.) let visible light pass through, but absorb infrared light––causing the atmosphere to heat up. The warmer atmosphere emits more infrared light, which tends to be re-absorbed––perhaps many times––before the energy eventually returns to space. The extra time this energy hangs around has helped keep Earth warm enough to support life as we know it. (In contrast, the moon has no atmosphere, and it is colder than Earth, on average.)
Since the industrial age began around the year 1750, atmospheric carbon dioxide has increased by 40% and methane has increased by 150%. Such increases cause extra infrared light absorption, further heating Earth above its typical temperature range (even as energy from the sun stays basically the same). In other words, energy that gets to Earth has an even harder time leaving it, causing Earth’s average temperature to increase–– producing global climate change.
[In molecular detail, greenhouse gases absorb infrared light because their molecules can vibrate to produce asymmetric distributions of electric charge, which match the energy levels of various infrared wavelengths. In contrast, non-greenhouse gases (such as oxygen and nitrogen–– that is, O2 and N2) don't absorb infrared light, because they have symmetric charge distributions even when vibrating.]
Summary: (a) Earth absorbs most of the sunlight it receives; (b) Earth then emits the absorbed light’s energy as infrared light; (c) greenhouse gases absorb a lot of the infrared light before it can leave our atmosphere; (d) being absorbed slows the rate at which energy escapes to space; and (e) the slower passage of energy heats up the atmosphere, water, and ground. By increasing the amount of greenhouse gases in the atmosphere, humans are increasing the atmosphere’s absorption of infrared light, thereby warming Earth and disrupting global climate patterns.
Shorter Summary: Earth transforms sunlight’s visible light energy into infrared light energy, which leaves Earth slowly because it is absorbed by greenhouse gases. When people produce greenhouse gases, energy leaves Earth even more slowly––raising Earth’s temperature.
Global warming means the rise in the mean global temperature to a level which affects the life-forms on the earth surface. The factors responsible for this warming may be both natural and man made. Warming of the globe due to natural factors is not an unusual phenomenon.
The earth's climate is variable. For example, about 18,000 years ago, the earth was about 5°C cooler than it is today. That was the last glacial period on the earth. There after, the global temperature began to rise.
The earth is kept warm due to what is known as the green house effect. Without it the earth would be a frozen waste land. The short wave lengths or ultraviolate radiation coming from the sun penetrates the atmosphere and is absorbed by the earth. This observed energy is also radiated back to space at infra-red wave lengths. The earth atmosphere contains gases which trap some of the outgoing radiation and thereby warm the earth.
These gases are known as green house gases. Wastes vapour, carbon dioxide, methane, ozone, nitrous cxide, CFCS and halons are prominent examples to maintain the global energy balances, both the atmosphere and the surface will warm until the outgoing energy equals the incoming energy.
The increase in the quality of the greenhouse gases in the atmosphere can reinforce the greenhouse effect (increase in temperature of the earth) and lead to global warming. Carbon dioxide is the largest contributor to the global warming as it holds the largest share among the green house gases in the atmosphere. The reason behind it is natural disorder as well as man made activities.
Volcanic eruptions and forest fire are some of the natural reasons which cannot be checked. But the current global trend i.e., deforestation, along with increased combustion of fossil fuels have a cumulative effect on the net increase in carbon dioxide content. We know forests are the areas where the green leaves efficiently utilize carbon-dioxide to make their own food. Deforestation reduces this utilization of carbon dioxide.
Consumption of fossil fuels and house hold fuels gives off considerable amount of carbon dioxide. Hence, reduction in the use of fossil fuels is very necessary. Equally necessary is afforestation. It should be encouraged and we, the people, should realize its importance.
Along with reduction in the use of fossil fuels, the use o. the house hold fuels like wood coal, Kerosene should also be reduced by encouraging LPG stove and bio-gas plants. They cause less atmospheric pollution. If these methods are applied, we will have to face serious consequences such as floods, droughts, storms and extremely warm summer. Not only this, the sea level may increase due to the rise in global temperature.
We cannot control natural happenings but we can control ourselves. We can reduce the threat of the global warming to a great extent by applying the ways which have been mentioned above. We have to think as a whole to get rid of this problem.