Global warming is simply defined as a process by which there is a gradual increase in the earth's surface temperature. Global warming has emerged as one of the most serious challenges facing the globe today. A National Research Council study dated May 2001 states "Greenhouse gases are accumulating in earth's atmosphere as a result of human activities, causing surface air temperatures and sub-surface ocean temperatures to rise. Owing to global warming there is an alarming increase in the temperature of Arctic region where the speedy melting of ice is causing a rising of global sea level, posing great threat of flooding to low lying areas of many countries". Other effects of global warming include retreat in glacier crusts all over the world, changes in agricultural yields and animal species extinctions. Carbon dioxide is deemed as the great contributor to the global warming. Owing to industrial revolution and technological progress, there has been colossal increase in the amount of carbon dioxide whose presence in the atmosphere causes global warming. -ISHFAQUE RUSTAMANI, Dadu, via e-mail, April 25.