The warming of the Arctic, as seen by the Siberian heatwave, may also impact western disturbances in India
Verkhoyansk, a town in Siberia, has recorded the highest temperature in the Arctic circle in the last 140 years at 38 degree celsius. This is around 18°C higher than the normal temperature for this time of the year for the place.
Even though the town is in the Guinness book of world records for the largest temperature range it experiences — from some -67 °C to some 37°C, this new record has an imprint of global warming and the impact of such warming can be witnessed even here in India.
“The new high shows temperature swings may be increasing,” Raghu Murtugudde, a climate scientist at the University of Maryland, said.
This is consistent with the consequences of the decrease in the Arctic Sea ice cover and reduction in ice thickness. The Arctic region is warming at twice the rate as the rest of the world because of anthropogenic green house gas emissions.
The increased rate of warming is because of a phenomenon known as Arctic amplification in which the melting ice hastens the process of warming by exposing areas that are not good at reflecting back heat into the atmosphere. This creates a feedback loop between melting ice and rising temperatures, amplifying the impact of warming.
The Arctic region has experienced repeated heat waves in the past few months, with Siberia recording average temperatures of 10°C more than normal in May 2020.
Arctic warming increases the north-south migrations of the polar jet stream, which is a permanent band of winds over the Arctic region. This means that some places get warm subtropical air coming up to Arctic latitudes and some places get Arctic air coming down into subtropics, according to Murtugudde.
“The jet stream is like the fence between the cold high pressure air of the Arctic and the warm low pressure air of the subtropics. If this fence swings north-south then the cold and warm air follow the jet stream,” Murtugudde said.
The Arctic ice is projected to continue to melt away due to warming and may even disappear in a few decades. This means that more extreme weather in the mid-latitudes might become commonplace. So Fairbanks in Alaska can have 15.5ºC during Christmas and Washington, DC, may have -45ºC at the same time.
The impacts of a warming Arctic are not limited to the region but can be felt as far as here in India in various ways. For instance, western disturbances respond to the pressure variations associated with the jet stream swings.
The western disturbances are extra-tropical storms that originate in the Mediterranean and travel to India on the sub-tropical jet stream. They cause rainfall in north west, northern and north eastern India during the winter and spring months and snowfall in the high altitude regions.
This year, they were particularly active and caused heavy rainfall in March, April and May over northern and north western India. These rains, moisture and the vegetation they produced was partly responsible for the early locust attacks in Rajasthan this year which spread as far east as Chattisgarh for the first time in decades.
“The temperatures over the Siberian region were warmer by several degrees during the pre-monsoon this year and we had an unusual western disturbance activity and rainfall over Iran, Afghanistan, Pakistan and India and this led to a locust swarm. So things may be connected in ways we don’t even imagine,” Murtugudde said.
But he also pointed that we will need more studies to quantify the impact of Arctic warming on the Indian weather and the monsoon.
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