Climate Change

Look back at the decade: Extreme weather

The second decade of the millenium will be remembered as the one when the climate emergency set in

 
By DTE Staff
Published: Saturday 28 December 2019
extreme weather. Artwork: Ritika Bohra

Across continents, extreme and contrasting weather became the new normal in the decade that just passed by. The period from 2011 to 2015 has been the warmest five-year on record globally. The average temperature in 2015 had already risen by more than one degree since the pre-industrial period.

While there’s growing fear that 2015’s record-breaking temperatures will be normal by 2030, 2019 had already seen record-breaking heat for nine consecutive months.

The term “climate change” has been rechristened “climate emergency”. According to the World Meteorological Organization, 22 million people were displaced in 2019 due to extreme weather events. Now, weather events displace more people than conflicts in the world. Here's a throwback:

Which way the wind blows 

The sight of wheat, mustard, gram and fenugreek crops spread over 10 hectares (ha) would fill Vidyadhar Olkha’s heart with joy. It was end of February and the crops were almost ready to be harvested. A week later, all he had was a mat of leaves and stalks lying on the ground. The rain and hailstorm in the first week of March destroyed 70 per cent of his crops in Jhunjhunu district of Rajasthan. Olkha has no idea what brought so much rain this March. Neither do scientists nor weather forecasters, who attribute the rain to western disturbances and have different theories on what made the disturbances so severe this year.

Western disturbances are low-pressure areas embedded in the Westerlies, the planetary winds that flow from west to east between 30° and 60° latitude. They usually bring mild rain during January-February, which is beneficial to the rabi crop.

But in the past few years western disturbances have been linked to disasters. The cloud burst in Leh in 2010, the floods and landslide in Uttarakhand in 2013 and the excessive rain in Jammu and Kashmir in 2014 were all linked to these disturbances. This year, as per the India Meteorological Department (IMD), the average rain received between March 1 and March 18 was 49.2 mm—197 per cent above normal. This caused severe damage to crops in several states of the country.

There is no unanimity among scientists on the reasons behind the changes in the phenomenon. They offer a number of explanations. First, easterly wave, that according to IMD, the severe rain this year is the result of the confluence of western disturbance and easterly wave from the Bay of Bengal. Easterly wave, or Easterlies, blows throughout the year from east to west. The confluence of the two winds happens throughout the year, but the results vary. They generally bring rain only to the northern part of the country but this year states in central and south India also received rain, says B P Yadav, head of IMD’s National Weather Forecasting Centre. Western parts of Madhya Pradesh, for instance, received over 2,025 times more than usual rainfall during March 1-18, while the rainfall in central Maharashtra was 3,671 times above normal, says IMD data.

Second, according to another study which blames global warming is by Jennifer Francis of Rutgers University, New Jersey, and S J Vavrus of University of Wisconsin Madison, both in the US. The study, published in the January issue of Environment Research Letters, suggests that heating up of the Arctic has weakened the jet streams in the northern hemisphere.

The west to east flow of jet streams in the northern hemisphere is maintained by the “gradient of heat” between the cool Arctic and warmer areas near the equator. But the Arctic has been warming since the past 20 years due to which the jet streams have become weaker. Rather than circling in a relatively straight path, jet streams now meander. This is making the South colder and the North warmer. Francis says western disturbances could definitely be affected by these jet streams.

A study by the Indian Institute of Tropical Meteorology, Pune, has directly linked western disturbances to global warming. In a paper published in Climate Dynamics in February 2015, the researchers say global warming is impacting air currents and causing freak weather events. Pronounced warming over the Tibetan plateau in recent decades has increased the instability of the Westerlies and this has increased the variability of the western disturbances.

According to the study, the western Himalayan region has seen a significant rise in surface temperatures since the 1950s. Observations from the area show a significant increase in precipitation in recent decades. The researchers looked at a variety of climate data to understand the increasing frequency of heavy precipitation. They say temperatures have risen in the middle- and upper-tropospheric levels over the subtropics (area between the Tropic of Cancer and the Tropic of Capricorn) and the middle latitudes. “Our study suggests that human induced climate change is the reason for the increased variability of western disturbance,” says R Krishnan, one of the researchers. “The findings are based on direct observations and we are now using climate models to confirm if the impact is human-induced,” says Krishnan.

Also in the decade

2012>>

The year set major records. A quick Google search reveals it was the hottest year in US history and second wettest in the UK. Data from 2011 and 2010 show similar extremes. A report by United Nations reveals 2012 is the third consecutive year to suffer economic losses of over $100 billion due to extreme weather events.

2019>>

Since the Internal Displacement Monitoring Centre for the first time started collating data on persons displaced by disasters in 2018, this set of population has been increasing. In 2019, 1.6 million people displaced by disasters were still in camps or places out of home. This was a “highly conservative estimate” as it didn’t consider displacement by disasters before this year. At 2.678 million, India had the highest number of people displaced by disasters and extreme weather events in 2018.

NUMBer : 144 Countries reported displacement due to natural disasters in 2019

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