Global Environmental Issues - Mechanical Engineering MCQ

Explanation: Molecules of carbon dioxide (CO₂) can absorb energy from infrared (IR) radiation. This ability to absorb and re-emit infrared energy is what makes CO₂ an effective heattrapping greenhouse gas. Not all gas molecules are able to absorb IR radiation. For example, Nitrogen (N₂) and Oxygen (O₂), which make up more than 90% of Earth's atmosphere, do not absorb infrared photons. CO₂ molecules can vibrate in ways that simpler nitrogen and oxygen molecules cannot, which allows CO₂ molecules to capture the IR photons.
Water vapour in the atmosphere does act as a greenhouse gas, however this is not because of its absorption by carbon dioxide. Air in general has water vapour which traps heat and provides a warming effect. It is the infrared part of solar radiation which carries heat. Even if Carbon Dioxide trapped
Ultra Violet light it would not lead to rise in temperature. Therefore (b) is a made up statement.
If Carbon Dioxide were to trap all the Solar Radiation, the Earth would have had a cooling effect instead of rise in temperature. Hence option C is incorrect as well.
Educational Objective: Test candidate's knowledge of harmful effects of carbon dioxide on the environment.

Explanation: Wetlands are the largest source for Methane emission, as bacteria decompose organic materials in the absence of oxygen. Domestic Livestock such as cattle, buffalo, sheep, goats and camels produce large amounts of methane as part of their normal digestive process.
Fermentation process in Rice Fields produces methane gas too. Methane is released as a direct result of the physical process of Coal extraction.
Educational Objective: Learn about sources of major Greenhouse gases.

Explanation: Impact of rise in temperature above 2 degree from pre industrial levels:

Hence statement 1 and 2 are correct. Statement 3 states that all the global wetlands will permanently disappear, which is an extreme statement and can be eliminated easily.
Similar to statement 3, statement 4 is also extreme which says cultivation of cereals will not be possible and can be eliminated.
Educational Objective: Understand the impact of Global warming and climate change.

Explanation: Cirrus cloud thinning is a proposed form of climate engineering. Cirrus clouds are high cold ice that, like other clouds, both reflect sunlight and absorb warming infrared radiation. However, they differ from other types of clouds in that, on average, infrared absorption outweighs sunlight reflection, resulting in a net warming effect on the climate. Therefore, thinning or removing these clouds would reduce their heat trapping capacity, resulting in a cooling effect on Earth's climate. This could be a potential tool to reduce anthropogenic global warming. Cirrus cloud thinning is an alternative category of climate engineering, in addition to solar radiation management and greenhouse gas removal. Solar Winds have hardly any significant impact on earth hence it is incorrect.
Reducing the frequency and intensity of tropical cyclones requires altering ocean water temperatures which is humanly impossible and hence is incorrect.
Artificial rains are created by spraying Dry Ice(solid carbon dioxide), Silver Iodide, Salt powder etc. on the rain bearing clouds. Hence it is incorrect.
Educational Objective: Test candidate's knowledge of various methods being suggeted to reduce the effect of global warming.

Explanation: Carbon sequestration or carbon dioxide removal is the long-term removal, capture or sequestration of carbon dioxide from the atmosphere to slow or reverse atmospheric CO2 pollution and to mitigate or reverse global warming. The carbon that is captured can be stored in geological formations such as deep saline aquifers, basalt formations, unmineable coal seams and depleted oil or gas reservoirs. Hence all the given options are correct.
Educational Objective: To learn various methods that can be employed to reduce the release of various Greenhouse Gases.

Explanation: Bretton Woods Conference: This conference led to the establishment of the World Bank and IMF. Hence option (a) is incorrect.
Montreal Protocol: The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion
Kyoto Protocol: The Kyoto Protocol is an international treaty which extends the 1992 United Nations Framework Convention on Climate Change (UNFCCC) that commits state parties to reduce greenhouse gas emissions.
Nagoya Protocol: The Nagoya Protocol is about Access to Genetic Resources and the Fair and Equitable Sharing of Benefits Arising from their Utilization to the Convention on Biological Diversity.
Educational Objective: To learn and differentiate various international treaties signed in the context of saving mother earth.

Explanation: CFCs are widely used in four areas: aerosol propellants, solvents in the cleaning of electronic components and metals, refrigerants, and the blowing agents in foam plastic manufacturing.  In aerosols, CFCs such as trichlorofluoro methane (CCl3F, CFC-11) and dichlorodifluoromethane (CCl2F2) were normally packed with materials like paint, insecticide, or cosmetic preparations in pressurized canisters. Tubeless tyre has no component which is a Greenhouse Gas. Hence it is the required answer.
Educational Objective: To learn different sources of Greenhouse Gases.

Explanation: In 1980s atmospheric scientists working in Antarctica reported about depletion of ozone layer commonly known as ozone hole over the South Pole. It was found that a unique set of conditions was responsible for the ozone hole. In summer season, nitrogen dioxide and methane react with chlorine monoxide (reaction iv) and chlorine atoms (reaction v) forming chlorine sinks, preventing much ozone depletion, whereas in winter, special type of clouds called polar stratospheric clouds are formed over Antarctica. These polar stratospheric clouds provide surface on which chlorine nitrate formed (reaction iv) gets hydrolysed to form hypochlorous acid (reaction (vi)). It also reacts with hydrogen chloride produced as per reaction (v) to give molecular chlorine.
When sunlight returns to Antarctica in the spring, the sun’s warmth breaks up the clouds and HOCl and Cl₂ are photolysed by sunlight, as given in reactions (viii) and (ix). The chlorine radicals thus formed, initiate the chain reaction for ozone depletion as described earlier.
Educational Objective: Test candidate's understanding of Ozone hole formation.

Explanation: Ocean acidification is the ongoing decrease in the pH of the Earth's oceans, caused by the uptake of carbon dioxide from the atmosphere. Seawater is slightly basic, and ocean acidification involves a shift towards pHneutral conditions rather than a transition to acidic conditions. This phenomenon will have an effect on: growth and survival of calcareous phytoplankton, coral reefs and phytoplanktonic larvae.
Ocean acidification may lead to decreased cloud formation and worsen global warming over time. Hence all the given statements are correct.