Geography Write short note

1. Greenhouse gases are the primary gases, such as, water vapour carbon dioxide, nitrous oxide, methane and ozone in the earth’s atmosphere that absorbs and traps energy from the sun.
2. Of all greenhouse gases, carbon dioxide absorbs more heat.
3. Without greenhouse gases, the average temperature of the earth’s surface would be about -18°C rather than the present average of 14°C.
4. Carbon dioxide emissions comes from many human activities such as combustion of fossil fuels, oil and natural gas, with additional contributions coming from deforestation, changes in land use, soil erosion and agriculture (including live stock).

Coral reefs:

1. Coral reefs are very sensitive to changes in climate. –
2. Corals form skeletons by extracting calcium carbonate from the ocean waters.
3. When the water temperature changes, densities of calcium carbonate in the skeletons also change.
4. Coral formed in the summer has a different density than coral formed in the winter.
5. This creates seasonal growth rings on the corals.
6. Scientists can study these rings to determine the temperature of the water and the season in which the coral grew.

Tree rings:

1. There are rings on the stem of the tree.
2. Variation in these rings is due to variation in the environmental conditions when they were formed.
3. Thus, studying this variation leads to improved understanding of past environmental conditions.

Ice cores:

1. These are samples of ice taken from the inner sides of the ice sheets.
2. Throughout each year, layers of snow fall over the ice sheets in Greenland and Antarctica.
3. Each layer of snow is different.
4. Summer snow differs from winter snow.
5. Each layer gives scientists a lot of information about the climate each year.

1. A flash flood is a term that describes floods, which is usually observed in the low-lying areas.
2. Floods are caused due to extremely heavy rainfall.
3. Flash floods generally occur after the collapse of natural ice, debris dam or a man-made dam, etc.
4. Flash foods also occur due to very high precipitation in one day (Mumbai in 2005, Kedarnath in 2013) or because of changed weather conditions like cyclones (Chennai, 2015).
5. Flash foods are different from the regular floods by having a time scale of fewer than six hours between rainfall and the onset of flooding.

1. When temperature changes, corals throw out the algae living in their tissues.
2. These algae are responsible for their colour.
3. An increase of 1°C – 2°C in ocean temperatures for a long time can lead to bleaching, turning corals white.
4. If corals are bleached for prolonged periods, they eventually die.
5. Coral bleaching leads to death of large amounts of corals.

1. Greenhouse gases are the primary gases, such as, water vapour carbon dioxide, nitrous oxide, methane and ozone in the earth’s atmosphere that absorbs and traps energy from the sun.
2. Of all greenhouse gases, carbon dioxide absorbs more heat.
3. Without greenhouse gases, the average temperature of the earth’s surface would be about -18°C rather than the present average of 14°C.
4. Carbon dioxide emissions comes from many human activities such as combustion of fossil fuels, oil and natural gas, with additional contributions coming from deforestation, changes in land use, soil erosion and agriculture (including live stock).