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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