HEATWAVE IN INDIA

  • The global warming trends over the Indian region are very different.
  • An assessment of climate change over the Indian subcontinent, published by the Ministry of Earth Sciences in 2020, said annual mean temperatures had risen by 0.7 degree Celsius from 1900.
  • This is significantly lower than the 1.59 degree Celsius rise for land temperatures across the world.

Why is warming over India lower?

  • The increase in temperatures is known to be more prominent in the higher altitudes, near the polar regions, than near the equator.
  • This is attributable to a complex set of atmospheric phenomena, including heat transfers from the tropics to the poles through prevailing systems of air circulation.
  • India happens to be in the tropical region, quite close to the equator.
  • The planet as a whole has warmed by 1.1 degree Celsius compared with preindustrial times.
  • Different regions have seen very different levels of warming.
  • The polar regions, particularly the Arctic, have seen significantly greater warming.
  • The IPCC report says the Arctic region has warmed at least twice as much as the world average.
  • Its current annual mean temperatures are about 2 degrees Celsius higher than pre-industrial times.

Reason:

  • Transfer of heat through air circulation.
  • Albedo effect, or how much sunlight a surface reflects.
  • The ice cover in the Arctic is melting, because of which more land or water is getting exposed to the Sun.
  • Ice traps the least amount of heat and reflects most of the solar radiation when compared with land or water.
  • Changes in clouds, water vapour and atmospheric temperatures.

Higher warming over land than oceans

  • The 0.7 degree Celsius temperature rise over India has to be compared with the warming seen over land areas, not the entire planet.
  • Land areas have become warmer by 1.59 degree Celsius.
  • Land areas have a tendency to get heated faster, and by a larger amount, than oceans.
  • Daily and seasonal variations in heating over land and oceans are usually explained in terms of their different heat capacities.
  • Oceans have a higher capacity to cool themselves down through the process of evaporation.
  • The warmer water evaporates, leaving the rest of the ocean relatively cooler.
  • However, longer-term enhanced heating trends over land have to be attributed to other, more complicated, physical processes involving land-ocean-atmospheric interactions. 

Impact of aerosols

  • Aerosols refer to all kinds of particles suspended in the atmosphere.
  • Many of these scatter sunlight back, so that lesser heat is absorbed by the land.
  • Aerosols also affect cloud formation.
  • Clouds, in turn, have an impact on how much sunlight is reflected or absorbed.
  • Aerosol concentration over the Indian region is quite high, due to natural as well as man-made reasons.
  • Emissions from vehicles, industries, construction, and other activities add a lot of aerosols in the Indian region.
  • A reduction in warming could be an unintended but positive side-effect.

SOURCE: THE HINDU, THE ECONOMIC TIMES, PIB

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