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HomeIndiaUttarakhand could see catastrophic floods if global warming targets are not met

Uttarakhand could see catastrophic floods if global warming targets are not met

Over 5,000 people died when an unprecedented spell of rain over four days flooded Uttarakhand during peak tourist season in 2013.

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New Delhi: The odds of a 2013-like deluge in Uttarakhand will be over four times higher every year if the world is allowed to warm 2°C over pre-industrial levels this century, a study has warned.

Over 5,000 people were killed and nearly 10 lakh affected when an unprecedented spell of rain over four days in June 2013 submerged vast swathes of Uttarakhand right in the middle of peak tourist and pilgrimage season (May-November).

It was one of the worst natural disasters to ever hit India.

The study adds to a growing pool of scientific evidence that rising temperatures, due to increasing greenhouse gas (such as carbon dioxide and methane) emissions, are making extreme weather events like heatwaves, droughts and floods more likely and more intense all around the world.

It was published in Environmental Research Letters (ERL), a peer-reviewed, open-access journal, this month.


Also read: Climate change is accelerating, says another UN report. Here’s why


Caught off-guard

Home to many popular pilgrimage centres, Uttarakhand is often referred to as Devabhumi, or ‘Land of the Gods’.

With its stunning setting in the lap of the Himalayas, clean air, lush green forests teeming with a variety of flora and fauna, and vast scope for adventure sports, it is also a tourist magnet.

According to government records, in 2017 alone, the state hosted well over 3 crore tourists, with the majority headed for the holy town and adventure-sport hotspot of Haridwar.

However, the state also has a fragile ecology vulnerable to earthquakes, landslides, avalanches, floods and flash floods.

Even so, the sheer intensity of the 2013 deluge — rain on one of the four days was 375 per cent the daily average for monsoon in the state — caught everyone offguard.

Worsening odds

The Oxford University study used computer simulations to investigate the future likelihood of extreme rainfall events in Uttarakhand, like the one that occurred in 2013, in an Earth 1.5°C and 2°C hotter than pre-industrial times.

This is in line with the temperature targets set out in the landmark Paris Agreement.

The researchers concluded that an extreme four-day rainfall event, which in current conditions is a 1-in-100-year event (uncertainty range: 1-in-51-year to 1-in-192-year) in Uttarakhand, will become a 1-in-39-year event in a 1.5°C warmer world (uncertainty range: 1-in-25 years to 1-in-61 years) and a 1-in-23-year event (uncertainty range: 1-in-16 years to 1-in-33 years) in a 2°C warmer world.

A 1-in-100-year event does not mean that it is likely to occur once every 100 years — it is just the scientific way of saying that the odds of such an event occurring in any given year are 1 in 100.

“The return period of a 1-in-100-year event represents that the probability of such an event occurring in any given year is very low, which does not necessarily mean they cannot occur in consecutive years,” wrote the study’s lead author, Savitri Kumari, a researcher at the University of Oxford, in an email to The Print.


Also read: Study shows climate change has a new victim — a type of cloud


Dilemma in the offing

The 2016 Paris agreement calls on the world to restrict warming this century to 2°C above pre-industrial levels, but suggests that temperature rise should ideally be kept below 1.5°C.

According to the projections made by the United Nations Intergovernmental Panel on Climate Change (IPCC), a business-as-usual scenario will see temperatures rise by 1.5°C between 2040 and 2050, and 2°C between 2070 and 2080, thus dooming the world to catastrophic consequences before the turn of the century.

Importantly, in addition to the effects of greenhouse gases, the study examined the impact of aerosol concentrations on extreme rainfall events as well.

Aerosols are tiny atmospheric particles, primarily made up of salt and water. Industrial and vehicular pollution is the major source of these particles. When present in excess, they make cloud formation less likely and hence reduce rainfall.

Rising temperatures due to human-caused climate change have the opposite effect. Warm air can hold more moisture and hence makes rainfall more likely and more intense.

“The amount of water vapour that the atmosphere can hold (saturation humidity) is an exponential function of temperature,” wrote Krishna AchutaRao, an associate professor and climate modelling expert at the Centre for Atmospheric Sciences at IIT-Delhi, in an email to The Print.

“Every one-degree Celsius rise in temperature results in a 7 per cent rise in saturation humidity,” he added. “So, that leads to more rain.”

This study suggests that the increase in rainfall due to the warming we have had so far has been partly counter-balanced by the decrease in rainfall on account of increasing aerosol particle concentration from rising pollution levels.

This raises a serious dilemma: In our efforts to limit the sources of greenhouse gases, we will also limit the sources of aerosols and lose the masking effect that they have had so far.

As we move towards the 1.5°C and 2°C targets, rising temperatures could overcome the aerosol-masking effect and we may see a greater rise in extreme rainfall events.

Given that Uttarakhand already sees a heavy monsoon, a further increase in the likelihood of extreme events would mean more frequent rainfall-related disasters.

“With the increasing rate of socio-economic loss due to an increasing number of devastating extreme weather events, all around the world, instant action on implementing adaptation and mitigation measures is not just the right thing to do but the smart thing to do,” said Kumari.

Given the high stakes involved, the Oxford University study also encourages further investigation into the subject with more sophisticated, high-resolution climate models to better understand these events at a local level and guide adaptation strategies.

The author is a freelancer and has a keen interest in climate change and science. 


Also read: How global media goes wrong on coverage of climate change


 

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