<prompt> Which of the following is the greatest contributor to global warmig as a consequence of human activities and life style: September 2012CO2ChlorofluorocarbonsMethaneOzone  <response>: Ans: A i.e. CO2 Global warming It is the rise in the average temperature of Eahs atmosphere and oceans since the late 19th century and its projected continuation. Since the early 20th century, Eahs mean surface temperature has increased by about 0.8 degC1.4 degF, with about two-thirds of the increase occurring since 1980. Warming of the climate system is unequivocal, and scientists are more than 90 ceain that it is primarily caused by increasing concentrations of greenhouse gases produced by human activities such as the burning of fossil fuels and deforestation. The major greenhouse gases are water vapor, which causes about 36-70 of the greenhouse effect; carbon dioxide CO2, which causes 9-26;methane CH4, which causes 4-9; and ozone03, which causes 3-7 