The correct answer is option A) global warming.
CO2 molecules have a tendency to trap the radiations emitted from sun. So, the increased atmospheric levels of carbon dioxide means more trapping of heat radiations leading to more global warming. Even during the time of dusk when sun disappears the environment remains warm because of the presence of CO2 gas in our atmosphere. This tendency of CO2 to trap the heat is known as green house effect. Apart from CO2, there are some other green house gases too which are able to trap heat. So, the heat generated because of the sun rays remains in the earth's atmosphere rather than dissipating back into the space. The role of CO2 is not profound in causing El Niño, wind storms or ozone depletion. El Niño is caused by trade winds, wind storms are caused by generation of differential pressure gradient whereas ozone depletion is caused by chlorofluorocarbons.
