Tag: global environmental change

Carbon dioxide is a greenhouse gas. It is released constantly by burning of fuels in industries, automobiles etc. It causes a severe increase in atmospheric temperature and leads to global warming. It contributes nearly 60% of global warming.

When carbon dioxide and other air pollutants are collected in the atmosphere they absorb sunlight that has bounced from the earth’s surface. This leads to an increase in the earth's average surface temperature and is called global warming. Carbon dioxide emissions from burning fossil fuels and deforestation are the primary cause of global warming. Thus the correct answer is option C.

Global warming is caused by increased atmospheric concentration of $CO _2$ and other green house gases. As greenhouse gases absorbs the solar energy when radiation is reflected back to the atmosphere from earth's surface and increase the earth's temperature. Eutrophication refers to the presence of excess organic compounds in water. Depletion of the ozone layer is caused by the excess release of chlorine and bromine-containing the chemical in the atmosphere. Acid rain is the result of increased sulphur and nitrogen oxide levels in the atmosphere. Slow metabolism and excretion of pesticides causes their accumulation in fat tissues of organisms and is referred to as biomagnifications. The correct answer is A.

When carbon dioxide and other air pollutants are collected in the atmosphere they absorb sunlight that has bounced from the earth’s surface. This leads to an increase in the earth's average surface temperature and is called global warming. When there is no carbon dioxide in the atmosphere, the temperature of the Earth's surface will be less than the present temperature. 

When carbon dioxide and other air pollutants are collected in the atmosphere they absorb sunlight that has bounced from the earth’s surface. This leads to an increase in the earth's average surface temperature and is called global warming. When there is no effect of the global warming, the temperature of the Earth's surface will decrease. 

The unplanned clearing of land leads to loss of habitats and also it leads to loss of biodiversity.

Strategies to deal with global warming include (i) Complete replacement of chlorofluorocarbons with substitutes that have little effect on ozone and global warming, (ii) Increasing vegetation cover or forests for photosynthetic utilisation of carbon dioxide, (iii) Reduction in the use of nitrogen fertilizers and instead relying more on nitrogen fixation, (iv) Limiting use of fossil fuels by developing alternate sources of energy eg Solar energy, wind energy etc.

The warming up of global atmosphere present day is due to the increase in green house effect. Green house effect (GHE) describe the roles of water vapour, $CO _2$ and other trace gases in keeping the Earth's surface warmer than it would be otherwise.These radiatively active gases are relatively transparent to incoming shortwave radiation (visible spectrum), but are relatively opaque to outgoing reradiating (infrared rays) longwave radiation. The latter radiation, which would otherwise escape to space, is trapped by these gases within the lower levels of the atmosphere. The subsequent reradiation of some of the energy back to the surface maintains surface temperature higher than they would be if the gases were absent (without the green house effect the Earth's average global temperature would be 18 degree celsius rather than the present 15 degree celsius). There is concern that increasing concentration of the green house gases including CO2, CH4, and man made chlorofluorocarbons (CFCS), may enhance the green house effect and cause global warming. Ozone layer present in the stratosphere is depleted by the aerosols and chloroflurocarbons. Ozone protects the earth from high energy ultra violet radiation. So, the correct answer is 'If both the assertion and reason are true but the reason is not a correct explanation of the assertion'

Carbon dioxide atmosphere absorbs and stores the energy near the earth's surface when incoming solar radiation is reflected back to the space. If there was no carbon dioxide then there would no absorption of solar energy and hence the temperature of earth's surface would be less than the present level. So, the correct answer is 'Less than the present level'.