Test: Greenhouse Effect & Global Warming (Old NCERT) - Grade 12 MCQ

Greenhouse gases like CO₂ ,CH4 and CFC_s are essential for keeping the earth warm and hospitable. They prevent a substantial part of long wave radiations emitted by earth to escape into space, but these gases radiate a part of this energy back to the earth. This phenomenon is called greenhouse effect. Because of green house effect, the mean annual temperature of earth is 15. In its absence, it will fall to −18.

Increases in the level of greenhouse gases has led to considerable heating of earth leading to global warming. During the past century, the temperature of earth has increased by 0.6, most of it during the last three decades. Rise in temperature is slight in tropics, moderate in middle latitudes and maximum in polar regions. It will led to melting of polar ice caps as well as of other places like the Himalayan snow caps.

The rise in temperature due to global warming is leading to deleterious changes in the environment and resulting in odd climatic changes like EL Nino effect. El Nino effect is the abnormal warming of surface ocean water. It affects the weather in large parts of the world. Moisture carrying capacity of air will increase. Pattern of air-mass movement will change. Precipitation will increase at higher latitudes both in summer and winter and in southern as well as Eastern Asia in summer. Frequency of droughts and floods  will increase. Threat to human health will increase in tropical and subtropical countries due to changed ranges of disease vectors and water borne pathogens.

Earth summit (United Nations Conference on Environment and Development 1992) was held in Rio de lanerio (Brazil) and adopted the recommendations of CCC (Convention on Climate Changel for reducing greenhouse gases. The recommendations were sioned by 154 nations They pledged to maintain emission of greenhouse gases level.

Green house effect is due to O₃ and CO₂.