Global warming is an average increase in the temperature of the atmosphere near the Earth's surface and in the troposphere, which can contribute to changes in global climate patterns.
The Intergovernmental Panel on Climate Change (IPCC) reported that the 20th century saw an increase in global average surface temperature of approximately 0.6 °C (1.1 °F).
Rising average temperatures are affecting the environment. Some observed changes include shrinking of glaciers, thawing of permafrost, later freezing and earlier break-up of ice on rivers and lakes, lengthening of growing seasons, shifts in plant and animal ranges and earlier flowering of trees
CAUSES OF GLOBAL WARMING: THE GREEN HOUSE EFFECT
The greenhouse effect is the natural process by which the atmosphere traps some of the Sun's energy, warming the Earth enough to support life.
It is the warming that results when solar radiation is trapped by the atmosphere; caused by atmospheric gases that allow sunshine to pass through but absorb heat that is radiated back from the warmed surface of the earth
Without greenhouse warming the Earth’s average surface temperature would be around –18°C (0°F) and unable to support life.
Scientists believe a human-driven increase in "greenhouse gases" is increasing the effect artificially.
Modern global warming is the result of an increase in magnitude of the called greenhouse effect, a warming of Earth’s surface and lower atmosphere caused by the presence of water vapour, carbon dioxide, methane, and other greenhouse gases
Greenhouse gases include water vapour, Carbon dioxide, Methane, Nitrous oxide, Halogenated Fluorocarbons, Ozone, Perfluorinated carbons, and Hydrofluorocarbons.
G reenhouse gases warm Earth’s surface by increasing the net downward longwave radiation reaching the surface
Global warming is also caused by an increase in the levels of these gases brought about by human activity. The greatest impact on the greenhouse effect has come from industrialization and increases in the amounts of carbon dioxide, methane, and nitrous oxide.
SOME GREEN HOUSE GASES
Water vapour is the most important greenhouse gas, but human activity doesn’t have much direct impact on its amount in the atmosphere.
The primary role of water vapour is not as a direct agent of radiative forcing but rather as a climate feedback
Increased evaporation leads to a greater concentration of water vapour in the lower atmosphere capable of absorbing longwave radiation and emitting it downward
Carbon dioxide (CO 2 ) is is a colourless, odorless non-flammable gas and is the most prominent Greenhouse gas in Earth's atmosphere
Carbon dioxide is used by plants during photosynthesis to make sugars
It is produced during respiration by plants, and by all animals, fungi and microorganisms that depend either directly or indirectly on plants for food
Carbon Dioxide is also produced by burning of fossil fuels and deforestation
Methane (CH 4 ) is the second most important greenhouse gas.
Methane is a colourless, odorless, flammable gas
Natural sources of methane include tropical and northern wetlands, methane-oxidizing bacteria that feed on organic material consumed by termites, volcanoes, seepage vents of the seafloor in regions rich with organic sediment
Methane is also released from rice paddies, livestock farms and landfill sites
Nitrous Oxide ( N 2 O) is a colourless non-flammable gas, with a pleasant, slightly sweet odor.
It is a significant Greenhouse gas
Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste.
Hydrofluorocarbons, Perfluorocarbons, and Sulfur Hexafluoride are synthetic, powerful greenhouse gases that are emitted from a variety of industrial processes.
Fluorinated gases are sometimes used as substitutes for ozone-depleting substances (that is, CFCs, HCFCs, and Halons).
These gases are typically emitted in smaller quantities, but they are potent greenhouse gases