March 23, 2014

10th Social New Text Book - Global Warming and Climate Change

Global Warming and Climate Change: As Earth started to take shape from a fiery ball to a planet, many gases were released. These gases did not escape into outer space because of the Earth’s gravitational pull. It still holds them back. The result?

A thin layer of gases surrounds Earth and provides us several important benefits. For example: the oxygen that we breathe, the ozone that protects us from harmful ultraviolet rays from the sun, the nitrogen that our plants use to make proteins that we need, the medium through which fresh water is circulated, and keep us warm (look at the image from Class IX Chapter 4).

Keeping us warm is one of the most important things that the atmosphere does for us. It is like a light, but effective, blanket enveloping Earth. You will recall from Class IX that the atmosphere traps a lot of the solar energy that reaches Earth by preventing it from totally escaping back into space. This is called global warming. This is important and vital for life to survive on this planet. If it did not have this atmosphere, earth would be very cold indeed.

However, since the 19th century the planet is warming up very rapidly. There is an increasing concern about this. Why this concern? After all, Earth has been through many cycles of warming and cooling (in fact, freezing!). So what is so special about it now? Earlier cycles of cooling and warming happened over very long periods of time. This allowed life on Earth the time to adapt to the changes. The problem now is that the heating is much more rapid and could lead to catastrophic changes. Much of the warming that has been occurring since the Industrial Revolution, is because of human activities. Hence, the current global warming trend is called AGW (Anthropogenic Global Warming; means caused by humans).

More recently, scientists are discovering large volumes of methane under the frozen tundras of the far northern latitudes (mainly in the vast expanses of northern Russia). As global temperature increases, the ice in the tundra melts more. The methane that is trapped under the ice escapes into the atmosphere, increasing the global temperatures. In turn, this causes even more ice to melt, releasing even more
methane, and so on. Methane is said to be even more powerful than carbon dioxide as a greenhouse gas.

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