Abdul Shakoor : The writer is M.Sc in Physics from University of Karachi. He can be reached at: abdulshakoorbhutto50@gmail.com

Global warming is a gradual process of warming the earth’s surface and the entire environment, including the oceans, ice caps, etc. Global warming refers to the increase in average temperature of earth’s surface during the last century, from 1900-2000.
In recent years, global warming has clearly been observed. According to the Environmental Protection Agency, the average surface temperature of the Earth has risen by 1.4 degrees Fahrenheit (0.8 degrees Celsius) in the last century. It is also estimated that global temperatures could rise by another 2 to 11.5 degrees Fahrenheit in the next century.
Causes of Global Warming: There are many causes of the global warming, some are natural causes and some are human made causes. The most important cause of global warming is greenhouse gases which are generated by some natural processes as well as human activities. The increase in the level of greenhouse gases has been seen in the 20th century because of the increasing population, economy and use of energy. Increasing demand of industrialization in the modern world to fulfill almost each need is causing the release of variety of greenhouse gases through many industrial processes in the atmosphere.
The release of carbon dioxide (CO2) and sulphur dioxide (SO2) gas has been increased in the recent years by 10-fold. The release of carbon dioxide gas varies according to the natural and industrial processes including photosynthesis and oxidation cycles. Methane is another greenhouse gas release in the atmosphere by the anaerobic decomposition of organic materials. Other greenhouse gases are like oxides of nitrogen (nitrous oxide), halocarbons, chlorofluorocarbons (CFCs), chlorine and bromine compounds, etc. Such greenhouse gases get collected to the atmosphere and disturb the radiative balance of atmosphere. They have capability to absorb heat radiations and cause warming of the earth surface.
Another cause of global warming is ozone depletion means declination of ozone layer over Antarctica. Ozone layer is declining day by day by increasing release of chlorofluorocarbon gas. It is a human generated cause of global warming. Chlorofluorocarbon gas is used at many places as aerosol propellants in the industrial cleaning fluids and in the refrigerators, the gradual release of which causes declination to the ozone layer in the atmosphere.
Ozone layer causes protection to the earth surface by inhibiting the harmful sun rays to coming to the earth. However, gradually declining ozone layer is the big indication of increasing global warming of the earth surface. Harmful ultraviolet sun rays are entering to the biosphere and get absorbed by the green houses gases which ultimately increase the global warming. According to the statistics, it has been estimated that the size of ozone hole has been twice the size of Antarctica (more than 25 million km2) by 2000. There is no any clear trend of ozone layer declination in the winter or summer seasons.
Presence of various aerosols in the atmosphere is also causing earth’s surface temperature to increase. Atmospheric aerosols are fully capable to scatter (causes cooling to the planet) and absorb (makes air warm) the solar and infrared radiations. They are also capable to change the microphysical and chemical properties of the clouds and possibly their lifetime and extent. The increasing number of aerosols in the atmosphere is because of human contribution. Dust is produced by agriculture, organic droplets and soot particles are produced by biomass burning, and aerosols are produced by the industrial processes through the burning of wide variety of products in the manufacturing process. Various emissions by means of transport generate different pollutants which get converted to the aerosols through many chemical reactions in the atmosphere.
Effects of Global Warming: The effects of global warming have been very clear in the recent years because of increasing sources of global warming. According to the U.S. Geological Survey, it has been recorded that there were 150 glaciers located in the Montana’s Glacier National Park however because of increasing effect of global warming, only 25 glaciers are left. Huge level climate changes are making hurricanes more dangerous and powerful. Natural storms are getting so strong by taking energy from temperature difference (of cold upper atmosphere and warm Tropical Ocean). Year 2012 has been recorded as hottest year since 1895 and year 2013 together with 2003 as the warmest year since 1880.
Global warming causes lot of climate changes in the atmosphere such as increasing summer season, decreasing winter season, increasing temperature, changes in air circulation patterns, jet stream, rain without season, melting ice caps, declining ozone layer, occurrence of heavy storms, cyclones, flood, drought, and so many effects.
Solutions of Global Warming: Many awareness programmes and programmes to reduce global warming have been run and implemented by the government agencies, business leaders, private sectors, NGOs, etc.
While we cannot stop global warming overnight, or even over the next several decades, we can slow the rate and limit the amount of global warming by reducing human emissions of heat-trapping gases and soot (“black carbon”) …Once this excess heat radiated out to space, Earth’s temperature would stabilize.
Some of the damage caused by global warming cannot be reversed by solutions (such as melting ice caps). However, we must not go back and do our best to reduce the effects of global warming by reducing the human causes of global warming. We should try to reduce greenhouse gas emissions and adapt to some of the changes that have taken place over the years. Instead of using electricity, we should try to use clean energy or energy from the solar system, wind and geothermal. Reducing the level of burning coal and oil, the use of means of transportation, the use of electrical appliances, etc. can reduce global warming to a great extent.