● The term `color{brown}("‘Greenhouse effect’")` has been derived from a `color{violet}("phenomenon")` that occurs in a `color{violet}("greenhouse. ")`

● A `color{violet}("Greenhouse")` looks like a `color{violet}("small glass house")` and is used for `color{violet}("growing plants")` especially during winter.

● In a `color{violet}("greenhouse")` the `color{violet}("glass panel")` lets the `color{violet}("light")` in, but does not allow heat to escape.

● Therefore, the `color{violet}("greenhouse warms")` up, very much like inside a `color{violet}("car")` that has been parked in the `color{violet}("sun")` for a few hours.

● The `color{violet}("greenhouse effect")` is a naturally occurring phenomenon that is responsible for `color{brown}("heating of Earth’s surface")` and `color{violet}("atmosphere.")`

● Without `color{violet}("greenhouse effect")` the `color{violet}("average temperature")` at `color{violet}("surface of Earth")` would have been a `color{brown}("chilly" –18^o C)` rather than the present `color{brown}("average of" 15^oC)`.

● In order to understand the `color{violet}("greenhouse effect")`, it is necessary to know the `color{violet}("fate")` of the `color{violet}("energy of sunlight")` that reaches the outermost atmosphere.

● `color{violet}("Clouds and gases reflect")` about `color{violet}("one-fourth")` of the incoming `color{violet}("solar radiation")`, and `color{violet}("absorb")` some of it but almost half of incoming `color{violet}("solar radiation")` falls on `color{violet}("Earth’s surface heating")` it, while a small proportion is reflected back.

● `color{violet}("Earth’s surface re-emits heat")` in the form of `color{violet}("infrared radiation")` but part of this does not escape into space as `color{violet}("atmospheric gases")` (e.g., carbon dioxide, methane, etc.) absorb a major fraction of it.

● The molecules of these `color{violet}("gases radiate heat energy")`, and a major part of which again comes to `color{violet}("Earth’s surface")`, thus `color{violet}("heating")` it up once again.

● This cycle is repeated many a times.

● The above-mentioned gases – `color{brown}("carbon dioxide and methane")` – are commonly known as `color{brown}("greenhouse gases")` because they are responsible for the `color{violet}("greenhouse effect")`

● Increase in the level of `color{violet}("greenhouse gases")` has led to considerable `color{violet}("heating of Earth")` leading to global warming.

● During the past century, the `color{violet}("temperature of Earth")` has increased by `color{violet}(0.6^oC)`, most of it during the last three decades.

● Scientists believe that this `color{violet}("rise in temperature")` is leading to deleterious changes in the `color{violet}("environment")` and resulting in `color{violet}("odd climatic changes")` (e.g. `color{brown}(" El Nino effect")`), thus leading to increased melting of polar ice caps as well as of other places like the Himalayan snow caps.

● Over many years, this will result in a `color{violet}("rise in sea level")` that can submerge many coastal areas.

● The total `color{violet}("spectrum of changes")` that global warming can bring about is a subject that is still under active research.

● We can `color{violet}("control global warming")` by various measures.

● The measures include cutting down use of `color{brown}("fossil fuel")`, `color{violet}("improving efficiency")` of energy usage, reducing
deforestation, planting trees and slowing down the growth of human population.

● International initiatives are also being taken to `color{violet}("reduce the emission")` of greenhouse gases into the atmosphere.