Polar Climates (E)

Polar Climates (E)

Polar climates are found poleward of 70° latitude. The defining feature is extreme cold throughout the year, with temperatures that never rise high enough to support trees. The book divides polar climates into two distinct types: Tundra (ET) and Ice Cap (EF).

Tundra Climate (ET)

The tundra climate gets its name from the vegetation that grows there — low-growing mosses, lichens, and flowering plants. This is the region of permafrost, where the subsoil remains permanently frozen. Because the ground below stays frozen, water cannot drain away, and the surface becomes waterlogged during the brief thaw.

The growing season is very short, and combined with waterlogging, it supports only these low-growing plants. Trees cannot survive here. During summer, however, the tundra regions experience very long durations of daylight — in some places the sun barely sets. This long daylight partially compensates for the short growing season.

Ice Cap Climate (EF)

The ice cap climate occurs over interior Greenland and Antarctica. Even in summer, the temperature remains below freezing point. This area receives very little precipitation — it is essentially a cold desert.

The snow and ice that fall accumulate over time. The mounting pressure from the weight of accumulated ice causes deformation of the ice sheets, and eventually they break. These broken pieces move as icebergs that float in the Arctic and Antarctic waters. The book cites Plateau Station, Antarctica (79°S), as a place that portrays this climate.

Climate Change — A Natural Process

The section then shifts to a broader point: climate change is not new. The climate we experience now has been prevailing for roughly the last 10,000 years, with minor and occasionally wide fluctuations. The planet has witnessed many variations in climate since the beginning.

Several lines of evidence show this:

• Geological records show alteration of glacial and inter-glacial periods.
• Geomorphological features, especially in high altitudes and high latitudes, exhibit traces of advances and retreats of glaciers.
• Sediment deposits in glacial lakes reveal the occurrence of warm and cold periods.
• Tree rings provide clues about wet and dry periods.
• Historical records describe the vagaries in climate.

All these evidences indicate that change in climate is a natural and continuous process.

India's Climatic Past

India also witnessed alternate wet and dry periods. Archaeological findings show that the Rajasthan desert experienced a wet and cool climate around 8,000 B.C. The period from 3,000 to 1,700 B.C. had higher rainfall. From about 2,000 to 1,700 B.C., this region was the centre of the Harappan civilisation. Dry conditions have accentuated since then. …