Rainbow & Climate Change | 04 Nov 2022

Why in News?

Recently, a research has found out that the changes in cloud cover and liquid precipitation due to increased greenhouse gas emissions are projected to lead to a net increase in mean global annual rainbow days.

• Mean days of rainbows are expected to go up globally by 4.0–4.9% in a year by 2100.

What has the Study Revealed about Rainbows?

• Areas with Lesser Rainbows:
  • Around 21–34% of land areas will lose rainbow days.
  • Areas that will lose rainbow days are projected to have lower total precipitation by 2100, except those in Central Africa, Madagascar and central South America.
  • All are projected to have more annual dry days and less total annual cloud cover.
• Areas with Higher Rainbows:
  • Around 66–79% will gain rainbow days under higher emission futures.
  • India is one of the countries where the number of rainbow days will increase.
  • African countries like Mali, Niger, Chad, Sudan and Ethiopia are also likely to experience more rainbow days.
  • Rainbow gain hotspots are mostly located at higher latitudes or at very high elevations, like the Tibetan Plateau, where warming is predicted to lead to less snow and more rain.
  • Two rainbow gain hotspots namely, eastern Borneo and northern Japan, will see overall precipitation increase but more dry days per year.

How is Rainbow & Climate Change Inter-related?

• About: 

• • A rainbow is a common atmospheric optical phenomenon. It is a multicoloured arc in the sky that results when water droplets refract sunlight.
    • When sunlight hits a rain droplet, some of the light is reflected. The electromagnetic spectrum is made of light with many different wavelengths, and each is reflected at a different angle. Thus, spectrum is separated, producing a rainbow.
  • Rainbows can also be viewed around fog, sea spray, or waterfalls.
  • It is an optical illusion; it does not actually exist in a specific spot in the sky.
  • Rainbows are the result of the refraction and reflection of light.
    • Both refraction and reflection are phenomena that involve a change in a wave's direction.
    • A refracted wave may appear "bent", while a reflected wave might seem to "bounce back" from a surface or other wavefront.
  • The colors on a primary rainbow are always in order of their wavelength, from longest to shortest: red, orange, yellow, green, blue, indigo and violet.
• Linkage with Climate Change:
  • Human activities such as burning fossil fuels are warming the atmosphere, which changes patterns and amounts of rainfall and cloud cover.
  • Climate change will alter the distribution of rainbow occurrence by affecting evaporation and convergence of moisture.
    • This alters patterns of precipitation and cloud cover.

Source: DTE