Global+Warming

Global warming refers to an increase in temperatures around the world that have been noticed in the past 50years and particularly in the 1980s. The greenhouse effect is the process by which certain gases allow short wave radiation from the sun to pass through and heat up the earth, but trap an increasing proportion of long wave radiation from the earth. click here For more on this topic

The Enhanced greenhouse effect the increasing amount of greenhouse gases in the atmosphere as a result of human activities, and their impact on the atmospheric systems, including the depletion of the ozone layer which leads to global warming.

Recent human activities have led to a significant increase in the amount and type, of greenhouse gases in space, and is believed to be responsible for a rise in world temperatures. World temperatures rose by 0.6degrees Celsius in the last century and according to a UN report a further rise of 5.8 degrees by the end of the 21st Century.

The history of global climate change:


 * Causes of Global Warming **

a. The Human Causes of global warming include:

//Carbon Dioxide: // This is the most important factor in global warming. It is produced by road vehicles and by burning fossil fuels in power stations, largely produced by MEDCs due to the high level of energy they consume. The production of carbon monoxide will come into contact with oxygen to produced carbon dioxide, which significantly contributes to global warming. Secondary sources include deforestation and the burning of the tropical rainforests. These processes contribute to global warming by increasing the amount of carbon dioxide in the atmosphere because vegetation (forests) serves as a carbon sink. Therefore the reduction in vegetive cover would significantly reduce the natural ability of the forest to absorb carbon dioxide. Statistics indicate that CO2 levels have risen from about 315 parts per million (ppm) in 1950 to 355 ppm and are expected to reach 600ppm by 2050.

//Methane: // The second largest contributor to global warming, increasing at a rate of 1% per annum. It is released from decaying organic matter such as peat bogs, swamps, landfill sites, animal dung and farms. It is estimated that cattle produce about 100 million tons of methane by converting 10% of their food. 150m tons of methane is produced annually by paddy fields. Bogs also melt in high temperatures to release methane into the atmosphere.

//Chlorofluorocarbons (CFCs) // These gases produced from aerosols, air conditioners, foam packaging and refrigerators. They destroy the ozone layer and also absorb long wave radiation. Their production is increasing at a rate of 6% per annum and they are more efficient at trapping heat.

//Nitrous Oxide //

Nitrous oxide is emitted through combustion from cars and power stations,nitric acid production, agricultural fertilizer and biomass burning.

<span style="background-color: #ffffff; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">Water Vapour <span style="background-color: #ffffff; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">This is abundant in the atmosphere, however it does contribute to global warming to some extent.

<span style="background-color: #ffffff; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">b. Physical causes of global warming and cooling.

<span style="background-color: #ffffff; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">External factors contribute to climate change in a number of ways which are generally described as part of the atmospheric forces. These forces take place outside the earth's atmosphere and do not have anything to do with human activities. They may increase or decrease the temperature of the earth. examples include:

<span style="background-color: #ffffff; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">//Variations in solar energy// - sunspot activity raises global temperature

<span style="background-color: #ffffff; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">//Volcanic eruptions// - large quantities of volcanic dust in the atmosphere shield the earth from incoming insulation, lowering global temperature. For example, the eruption of Mount Pinatubo in 1991 caused a dip in global temperatures in the early 1990s. Also, the eruption of a volcano in Chile in produced dust that traveled around the earth.

<span style="background-color: #ffffff; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">//Milankovitch cycles or variations// in the tilt and/or orbit of the earth around the sun- refers to the three dominant cycles through which variations in the Earth's eccentricity, axial tilt and preccession occur.

<span style="background-color: #ffffff; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">//Changing oceanic circulation// such as the periodic warming (El Nino) and cooling (La Nina) of areas of the tropical Pacific Ocean.

<span style="background-color: #ffffff; font-family: 'Lucida Sans Unicode','Lucida Grande',sans-serif;">These physical causes of global temperature change have always existed and have been responsible for alternate heating and cooling cycles of the earth's temperature

Details on the physical factors responsible for global warming can be found here:Atmospheric forcings

Find below BBC documentaries on Climate Change