The ‘greenhouse effect’ is an atmospheric heating phenomenon in which the Earth experiences rise in temperature because certain gases (water vapor, carbon dioxide, nitrous oxide, and methane) in the atmosphere allow incoming sunlight to pass through but trap heat radiated from the earth’s surface. If these gases wouldn’t trap heat in the atmosphere, the temperature of the earth would be about 33 degrees centigrade colder on average. Because how these gases warm our planet, they are called as greenhouse gases and the effect they create in the atmosphere is called as greenhouse effect.

The greenhouse effect, although it sounds scary, is perfectly natural and normal. It is simply the name given to the process whereby certain naturally occurring gases in the Earth’s atmosphere retain some of the thermal radiation that reaches Earth from the sun. The main gases that are termed ‘greenhouse’ gases (GHG’s) are: Ozone, Carbon dioxide, Nitrous oxide, Water vapor and Methane. All of these are naturally occurring.

When the thermal radiation (or heat) arrives from the sun, some of it is bounced from the surface of the Earth by the ozone layer (which is the reason we can safely walk out in the sun, is this prevents the most dangerous radiation from the sun getting through the atmosphere), leaving only some heat to make it through to heat the Earth. This heat then rises back through the atmosphere, but most of it gets trapped by the greenhouse gases, which causes it to remain in the Earth’s atmosphere.

This principle is exactly the same as what happens in greenhouses, hence why it is called the greenhouse effect. Although it is natural, the fact that we are contributing to the greenhouse gases in the atmosphere by burning fossil fuels at such a great rate means that we are making the greenhouse effect worse, which is having some terrible consequences on life on Earth.

Causes of the Greenhouse Effect
Although the greenhouse effect is a natural phenomenon and is one of the reasons that life can exist on Earth (as greenhouse gases keep the surface of the Earth warm enough for us to live here: without them the Earth would be about 33 degrees centigrade colder on average, rendering many places inhospitable), the greenhouse effect is getting worse. This is having knock on effects, causing problems such as global warming, where the average temperature of the Earth is steadily rising over the years.

There are a number of reasons that there more of the normal greenhouse gases are being poured into the atmosphere. We ourselves are causing a lot of those extra greenhouse gases. There are several causes of extra greenhouse gases in the atmosphere.

1. Burning of Fossil Fuels
Fossil fuels, such as gas, petroleum and coal, are carbon based compounds that have existed in the Earth’s crust for many millions of years. They have been created as a result of the decomposition of organic matter such as plants and even the dinosaurs that lived on the surface of the Earth hundreds of millions of years ago. This carbon, therefore, has been stored within the surface of the Earth in various states – solid, liquid and gas, in fact – and have not been released into the atmosphere until recently.

However, since we have started using fossil fuels for our cars, electricity and heat, for instance, we have started pouring out thousands of metric tons of carbon dioxide into the atmosphere each and every year. The burning of fuels like coal, oil, wood, gas produce carbon dioxide which is released in to the atmosphere. The carbon that was once contained within the Earth, therefore, is being released into the atmosphere, and this carbon dioxide, as previously stated, is a greenhouse gas that causes the heat of the sun to be kept in the Earth’s atmosphere. CO2 is one the gases primarily responsible for the greenhouse effect. Waste material produced from factories and industries which contain toxic substances is dumped in the open air which produce harmful gases. Burning fossil fuels, therefore, is directly contributing to the greenhouse effect, and in a big way.

2. Farming
As odd as it may sound, farming may be drastically contributing to the greenhouse effect. Basically, because the demands of farming are now so great – the fact that there are so many people on Earth who all want food and drink, for example – even more animals are being kept on farms to provide both of these things. Amongst the most commonly farmed animals are cows. Problematically, however, cows release methane gas – one of the main greenhouse gases – into the atmosphere very regularly. How? By farting! And with so many millions of them living on Earth right now, an awful lot of extra methane gas is being released into the atmosphere every single day, contributing to the greenhouse effect.

3. Deforestation
Humans breathe oxygen in a carbon dioxide out; plants do exactly the opposite. In fact, carbon dioxide is a key element in photosynthesis. Trees and plants take in a lot of the carbon dioxide from the air and give back oxygen, making things balance in the atmosphere. After all, we do need greenhouse gases and the greenhouse effect in order to be able to live on the Earth, but we do not need too much, otherwise the Earth will start heating up too much too quickly.

Unfortunately, however, because we are cutting down so many trees every year and either not replacing them at all or not growing enough new trees, these plants cannot help to regulate the amount of oxygen and carbon dioxide in the atmosphere. This means that there is more carbon dioxide than ever before in the air and it is contributing greatly to the greenhouse effect.

Deforestation, on the other hand contributes effectively towards global warming. Due to increase in real estate projects and new new development, more trees are chopped off daily. Trees maintain balance of the environment as they intake carbon dioxide and release oxygen. Since, the growth of new plants doesn’t happen at that rate at which old plants are chopped off, the result is that are fewer trees to perform left to maintain ecological balance.

4. Increase in Population
Increase in population has further taken toll on the environment. With the rise in population, the demand for fuel, oil, gas, house, transport also increases. All these in some way or the other raises the CO2 level, which in turn increases global warming.

Greenhouse effect is explained well in this article.

Climate scientists are telling us that gases like carbon dioxide are causing global warming. Carbon dioxide is produced when petrol is burned in your car engine, or when coal and gas are burned at power-stations to make electricity. Carbon dioxide causes global warming because it contributes to the so-called greenhouse effect. So what is this greenhouse effect?
Winter is a good opportunity to observe the greenhouse effect in action. It should be obvious that sunlight heats the earth: it gets hotter when the sun shines, and colder at night when it doesn't. On clear dry nights it can get very cold indeed, but if the sky is cloudy, or overcast, then it doesn't get so cold. This happens because clouds trap heat. The more clouds there are, the warmer it stays overnight.
So how does this heat trapping work? And how does carbon dioxide come into play?
You know that radio stations have different frequencies. When you tune your radio to your favourite station, you are telling your radio receiver to block all radio-frequencies except those that the station uses. These frequencies are allowed into the radio's electronics.
Heat, just like radio-waves, has different frequencies, and clouds, just like a radio receiver, block certain frequencies of heat and allow other frequencies through. Without clouds most frequencies of heat escape into space and it gets very cold overnight. When there are clouds, some frequencies of heat are blocked from escaping into space, keeping it warmer.
It turns out that clouds and carbon dioxide trap heat differently, like radios tuned to different frequencies. In fact, carbon dioxide pretty much blocks precisely those frequencies that clouds would allow through. Add to this the fact that unlike clouds, which come and go, carbon dioxide is always there, its warming effect occurs even when the sky is clear and dry. You can probably understand now why climate scientists are so concerned about carbon dioxide. The more carbon dioxide in the atmosphere, the hotter the earth will become.
Of course, this is a simplified explanation of global warming, but the basic story I have just told you is correct. Scientists have known and understood this for over 100 years, and it has been confirmed in laboratory experiments. There is no doubt about the basic science behind global warming.
So does it really matter that driving a car and using electricity adds more carbon dioxide to the atmosphere? In my next segment, I will examine why scientists are convinced that if we are not careful, the earth will warm 2 or more degrees, and I will examine what the consequences of this will be.