A greenhouse gas is any gaseous compound in the atmosphere that is capable of arbsorbing infrared radiation, thereby trapping and holding heat in the atmosphere. By increasing the heat in the atmosphere, greenhouse gases are responsible for the greenhouse effect, which which leads to global warming.
It has been estimated that if greenhouse gas emissions continue at their present rate , Earth's surface temperature could exceed historical values in the nearest future , with potentially harmful effects in ecosystems, biodiversity and the livelihoods of people worldwide.
The most abundant greenhouse gases in Earth's atmosphere are: water vaour(H2O), Carbon dioxide(CO2), Methane(CH4), Nitrous Oxide (N2O), Ozone, Chlorofluorocarbons (CFCs), Hydrofluorocarbons (HCFCs).
SOURCES
Since the beginning of Industrial Revolution, the concentrations of most of the greenhouse gases have increased. For example, the mole fraction of Carbon dioxide has increased from 280ppm to 400ppm. Today the stock of Carbon dioxide in the atmosphere increases by more than 3million tonnes per annum compared with the existing stock. This increase is the result of human activities by burning fossil fuels, deforestation and forest degradation in tropical regions. The other greenhouse gases produced from human activities show similar increases in both amount and rate of increase.
The main sources of greenhouse gases due to human activity are:
■ burning of fossil fuels and deforestation leading to higher carbon dioxide concentrations in the air.
■livestock enteric fermentation and manure management, pipeline losses lead to higher methane concentrations.
■ use of Chlorofluorocarbons (CFCs) in refrigeration systems, and use of CFCs and halons in fire suppression systems and manufacturing process, lead to higher CFCs concentration.
■ Agricultural activities, including the use of fertilizer, lead to higher nitrous oxide concentration.
EFFECT
The main effect of increased greenhouse gas
emissions is global warming.
Carbon dioxide,methane, nitrous oxide and fluorinated gases all help trap heat in the Earth's atmosphere as a part of the greenhouse effect. The Earth's natural greenhouse effect makes life possible. However, human activities, primarily the burning of fossil fuels and deforestation, have intensified the greenhouse effect, causing global warming.
Apart from global warming, increases in the different greenhouse gases have other effects such as: ocean acidification, smog pollution, ozone depletion as well as changes to plant growth and nutrition levels.