Q.2. Write a short note on
(a) Climate Change
(b) Global Warming
(c) Ozone Depletion
(d) Acid Rain
Ans. (a) Climate Change
Introduction: Climate change is a change in global or regional climate patterns, in particular a change apparent from the mid to late 20th century onwards and attributed largely to the increased levels of atmospheric carbon dioxide produced by the use of fossil fuels.
Causes of Climate Change:
(i) Human Activities: Humans have been influencing the climate since the start of the Industrial Revolution. Since then, the average world temperature has risen by approximately 0.8 degrees Celsius. The sea level has risen by around twenty centimetres and most of the glaciers have shrunk dramatically.
(ii) Carbon dioxide emissions: The most well-known and the most important. greenhouse gas is carbon dioxide. The concentration of carbon dioxide in the atmosphere is subject to variation even without human intervention. Vast amounts of carbon dioxide are also released by the burning of fossil fuels. This creates a layer of gases around the Earth which traps sunlight and makes the Earth warmer. This is known as the greenhouse effect.
(iii) Aerosols: Aerosols are less well-known than greenhouse gases. Aerosols are dust particles which, in addition to carbon dioxide, are released into the atmosphere in large quantities when wood and fossil fuels are burned. Natural phenomena, greenhouse gases and aerosols create an imbalance in the incoming and outgoing radiation in the atmosphere. This process is known as radiative forcing. When the Earth heats up, the short-wave radiation from the sun that enters the atmosphere is greater than the long-wave radiation that exits the atmosphere. The temperature changes on Earth will not stop until the radiation balance is restored.
Effects of Climate Change:
(i) Alteration in seasonal patterns: A warmer atmosphere causes the planet's snowpack, glaciers and sea and freshwater ice to melt rapidly. Melting glaciers and polar ice sheets contribute to unprecedented sea level rise. Melting sea ice exposes darker ocean waters, which absorb more sunlight than ice-heating the ocean more and speeding up a relentless cycle of melting and heating. This alters the rain cycle and hence causes delays/advancements in seasons For example, late winters have been observed all the world at multiple places.
(ii) Human prosperity suffers: Due to climate change, agriculture takes a hit. Worldwide, farmers are struggling to keep up with shifting weather patterns and increasingly unpredictable water supplies. Farms are more likely to face attacks from weeds, diseases and pests, which affect yield. Extreme events also threaten crop yields, such as through flooding or reduced water supply. A warmer atmosphere increases the formation of ground-level ozone, also known as smog in polluted regions. Smog irritates lungs and triggers asthma attacks.
(iii) Hostile natural habitats: Habitats on land and in the sea are changing making them inhospitable for some species, while letting others move in and take over. Some ecosystems are at risk of collapsing.
Case Study: Coral Reefs
Coral reefs are highly sensitive to small changes in ocean temperatures. The heat stresses the algae that nourish the corals and provide their vibrant colours. The algae then leave, and the corals eventually starve - an event known as bleaching. As coral reefs are home to many other species, such as fish, their collapse would disrupt the entire ecosystem. Also, a more acidic ocean affects the normal calcium balance, meaning creatures with calcified shells, such as shellfish and coral, may not have enough calcium to grow.
Ans. (b) Global Warming
Introduction: Global Warming is a gradual increase in the overall temperature of the earth's atmosphere generally attributed to the greenhouse effect caused by increased levels of carbon dioxide, CFCs, and other pollutants.
Causes of Global Warming:
(i) Greenhouse Effect: The atmosphere allows most of the visible light from the Sun to pass through and reach Earth's surface. As Earth's surface is heated by sunlight, it radiates part of this energy back toward space as infrared radiation. This radiation, unlike visible light, tends to be absorbed by the greenhouse gases in the atmosphere, raising its temperature. The heated atmosphere in turn radiates infrared radiation back toward Earth's surface.
Although the greenhouse effects is naturally occurring phenomenon, it is possible that the effect could be intensified by the emission of greenhouse gases into the atmosphere as the result of human activity. From the beginning of the Industrial Revolution through the end of the 20th century, the amount of carbon dioxide in the atmosphere increased by roughly 30 percent and the amount of methane more than doubled. A number of scientists have predicted that human-related increases in atmospheric carbon dioxide and other greenhouse gases could lead by the end of the 21st century to an increase is the global average temperature of 0.3 to 4.8 °C.
(ii) Volcanic Eruptions: Volcanic eruptions are another issue that causes globe warming For instance, a single volcanic eruption will release amount of carbon dioxide and ash to the atmosphere. Once carbon dioxide increase, the temperature of earth increase and greenhouse trap the solar radiations in the earth
(iii) Methane: Methane is another issue that causes global warming. Methane is also a greenhouse gas. Methane is more effective in trapping beat in the atmosphere that carbon dioxide by 20 times. Usually methane gas can release from many areas. For instance, it can be from cattle, landfill, natural ga petroleum syster systems, coal mining, mobile explosion, or industrial waste process.
Effects of Global Warming:
(i) Polar Ice Caps Melting: As the temperature increase, the ice at the North Pole will melt. Once the ice melt the first effect will be raise on sen levels because the melting glaciers become oceans.
(ii) Loss of Habitat: Species that include polar bears and tropical frogs will be extinct due to climate change. Besides, various birds will migrate to other places because animals are not like humans. They cannot adapt the habitat that changes their living or temperature.
(iii) Increase in Diseases: Global warming is allowing disease-causing bacteria, viruses and fungi to move into new areas where they may harm species as diverse as lions and snails, butterflies and humans. Pathogens that have been restricted by seasonal temperatures can invade new areas and find new victims as the climate warms and winters grow milder.
Ans. (c) Ozone Depletion Introduction: Ozone depletion, gradual thinning of Earth's ozone laver in the upper atmosphere caused by the release of chemical compounds containing gaseous chlorine or bromine from industry and other human activities. Ozone depletion is a major environmental problem because it increases the amount of ultraviolet radiation that reaches Earth's surface, which increases the rate of skin cancer, eye cataracts, and genetic and immune system damage.
Case Study: Antarctic Ozone Hole
The severe depletion of the Antarctic ozone layer known as the "ozone hole occurs because of the special atmospheric and chemical conditions that exist there and nowhere else on the globe. The very low winter temperatures in the Antarctic stratosphere cause polar stratospheric clouds (PSC) to form. The primary cause of ozone depletion is the presence of chlorine-containing source gases (primarily CFCs and related halocarbons). In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyse orone destruction.
Causes of Ozone Depletion:
(i) Use of chloro-fluoro-carbons: They are compounds of chlorine, fluorine, and carbon used in refrigerators, air conditioners, and in cooling plants. These molecules can destroy ozone molecules and therefore depletion of the ozone layer.
(ii) Burning of Fossil Fuels: Nitrogen oxides such as nitrous oxide are also very reactive to ozone and are also responsible for holes in the ozone layer. These molecules are released by burning fossil fuels by cars and especially airplanes which fly near the ozone layer.
Effects of Ozone Layer Depletion:
(i) Effect on Humans: Exposure to UV rays from sun can lead to increased risk for developing of several types of skin cancers Direct exposure to UV rays can lead to Cataract problems, and also Photo keratitis or snow blindness. Increased exposure to UV rays can lead to weakening of the response of immune system and even impairment of the immune system in extreme cases.
(ii) Effect on animals: It affects amphibians in every stage of their life cycle; from hampering the growth and development in the larvae stage, deformities and decreases immunities in some species and to even retinal damage and blindness in some species. UV rays also have adverse effect on the marine ecosystem. It adversely affects the planktons which plays a vital role in the food chain and oceanic carbon cycle. Affecting phytoplankton will in turn affect the whole ocean ecosystem.
(iii) Effect on plants: UV radiations can alter the time of flowering in some plant species. It can also directly affect the plant growth by altering the physiological and developmental processes of the plants.
Ans. (d) Acid Rain Introduction: Acid rain is a broad term that includes any form of precipitation with acidic components, such as sulfuric or nitric acid that fall to the ground from the atmosphere in wet or dry forms. This can include rain, snow, fog, hail or even dust that is acidic.
Causes of Acid Rain:
(i) Volcanic Eruptions: Volcanoes can cause acid rain by blasting pollutants into the air. These pollutants can be carried around the world in jet streams and turned into acid rain far from the volcano.
(ii) Combustion: Sulphur dioxide and nitrogen oxides released into the air by fossil-fuel power plants, vehicles and oil refineries are the biggest cause of acid rain today. Two thirds of sulphur dioxide and one fourth of nitrogen oxide found in the atmosphere come from electric power generators.
(ii) Acid Rain: A chemical reaction happens when sulphur dioxide and nitrogen oxides mix with water, oxygen and other chemicals in the air. They then become sulfuric and nitric acids that mix with precipitation and fall to the ground. Precipitation is considered acidic when its pH level is about 5.2 or below. The normal pH of rain is around 5.6.
Effects of Acid Rain:
(i) Effects on Environment: Acid rain can make trees lose their leaves or needles. The needles and leaves of the trees turn brown and fall off. Trees can also auffer from stunted growth; and have damaged bark and leaves, which makes them vulnerable to weather, disease, and insects. Lakes are also damaged by acid rain.
(ii) Effect on Infrastructure: Architecture and artwork can be destroyed by acid rain. Acid particles can land on buildings, causing corrosion. When sulphur pollutants fall of the surfaces of buildings (especially those made out of sandstone or limestone), they react with the minerals in the stone to form a powdery substance that can be washed away by rain.
(iii) Effect on humans: One of the major problems that acid rain can cause in a human being is respiratory problems. Asthma, along with dry cough, headaches and throat irritations can be caused by the sulphur dioxides and nitrogen oxides from acid rain.
Case Study: Taj Mahal Decolourisation
The air in this place contains serious levels of sulphur and nitrogen oxides. This is due to the large number of industries set up nearby Taj Mahal and pollution of Yamuna River. As per metrological studies the wind direction is usually move in the direction where Taj is situated. All these led to acid rain. Acid rain reacted with the marble (calcium carbonate) of Taj Mahal and this causing damage to heritage structure.
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