There are two common meanings of the term "greenhouse effect". There is a "natural" greenhouse effect that keeps the Earth's climate warm and habitable. There is also the "man-made" greenhouse effect, which is the enhancement of Earth's natural greenhouse effect by the addition of greenhouse gases from the burning of fossil fuels (mainly petroleum, coal, and natural gas).
In order to understand how the greenhouse effect operates, we need to first understand "infrared radiation". Greenhouse gases reduce the rate at which the Earth's surface loses infrared radiation to outer space. Because one way to increase the temperature of anything is to reduce its rate of energy loss to its surroundings, this makes the Earth's surface and lower atmosphere warmer than they would otherwise be.
What the Greenhouse Effect Isn't
Since there is considerable misunderstanding and misconceptions regarding the greenhouse effect, it is useful to list a few of the things the greenhouse effect is not:
1) The greenhouse effect does not operate like a greenhouse that plants are grown in. Plant
2) The greenhouse effect does not require solar radiation (sunlight) to operate. The greenhouse effect would still exist if there was no sun, and the climate system was instead warmed from below by geothermal energy.
3) The greenhouse effect cannot be demonstrated with a jar or other enclosure because there is too little greenhouse gas involved. Thousands of feet of atmospheric depth are required for the greenhouse effect to have a measurable effect on temperature.
The greenhouse effect is entirely due to the fact that the atmosphere absorbs and emits infrared energy, combined with a heat source to warm the bottom of the atmosphere (in our case, the Sun) and the cold depths of outer space above the top of the atmosphere. The greenhouse gases (and clouds) reduce the ability of the Earth's surface to cool, thus raising its temperature above what it would be without those greenhouse gases.
What is Global Warming?
Global Warming is the increase of Earth's average surface temperature due to effect of greenhouse gases, such as carbon dioxide emissions from burning fossil fuels or from deforestation, which trap heat that would otherwise escape from Earth. This is a type of greenhouse effect.
Is global warming, caused by human activity, even remotely plausible?
Earth's climate is mostly influenced by the first 6 miles or so of the atmosphere which contains most of the matter making up the atmosphere. This is really a very thin layer if you think about it. In the book The End of Nature, author Bill McKibbin tells of walking three miles to from his cabin in the Adirondack's to buy food. Afterwards, he realized that on this short journey he had traveled a distance equal to that of the layer of the atmosphere where almost all the action of our climate is contained. In fact, if you were to view Earth from space, the principle part of the atmosphere would only be about as thick as the skin on an onion! Realizing this makes it more plausible to suppose that human beings can change the climate. A look at the amount of greenhouse gases we are spewing into the atmosphere (see below), makes it even more plausible.
What are the Greenhouse Gases?
The most significant greenhouse gas is actually water vapor, not something produced directly by humankind in significant amounts. However, even slight increases in atmospheric levels of carbon dioxide (CO2) can cause a substantial increase in temperature.
How much have we increased the Atmosphere's CO2 Concentration?
Human beings have increased the CO2 concentration in the atmosphere by about thirty percent, which is an extremely significant increase, even on inter-glacial timescales.
You can help to reduce the demand for fossil fuels, which in turn reduces global warming, by using energy more wisely. Here are 10 simple actions you can take to help reduce global warming.
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