The greenhouse effect refers to a process through which heat is trapped in the atmosphere by greenhouse gases and the average temperatures at the surface of the Earth rise.
The greenhouse effect can be natural or man-made.
The natural greenhouse effect helps in keeping the planet’s climate warm and proper for living. Through industrial and agricultural (cattle growing) activities, mining, fossil fuel and solid waste burning and deforestation, man has enhanced Earth’s natural greenhouse effect by adding greenhouse gases in the atmosphere.
The main such gases in our atmosphere are water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and ozone (O3). They have an important effect on Earth’s temperature, since, in their absence, the average temperature at the surface of our planet would be lower by 33°C, the present average being of 14°C.
The greenhouse effect and infrared radiation
The greenhouse effect is related to the amount of infrared radiation that is lost by Earth to outer space. Gases that contribute to the greenhouse effect reduce the rate at which infrared radiation is lost, as they trap part of it. By reducing the rate of energy loss of anything to its surroundings, its temperature is increased, and that is exactly what happens to Earth when it loses less infrared radiation than it used to. While the lower layers of the atmosphere are kept lower by these gases, the upper ones are kept colder.
A few figures to better understand man’s impact on the atmosphere
Around 80-90% of the natural greenhouse effect of Earth is related to water vapor and the presence of clouds. Most of the left percentage is related to carbon dioxide, methane and other greenhouse gases. Methane has a stronger greenhouse effect than carbon dioxide; however, it is less present in the atmosphere than the latter. Less present or not, the fact is that the amount of methane in the atmosphere has increased by about 150% since 1750. The concentration of carbon dioxide in the atmosphere in pre-industrial times was of 270 parts per million and it has reached 400 parts per million in 2012. Thus, man’s part in the formation of the greenhouse effect can be seen, which many scientists believe to be the cause of the global warming in the last 50 years.
With all these in mind, it is clear that it is necessary to find a way for the amount of greenhouse gases to be kept under control, as the rise in average temperatures leads to sea level rise, impacts agriculture and economy and the hydrological cycles.