Several major cities across Asia could face months of drought or severe flooding as an unusually strong El Nino develops later this year, with researchers warning that the scale of the phenomenon could be unlike anything seen in previous records.
An analysis by WaterAid, carried out by academics from the universities of Bristol and Cardiff, examined 44 years of rainfall data across 12 cities in South and Southeast Asia alongside the strength of previous El Nino events.
The researchers found that stronger El Nino events generally increase the likelihood of rainfall levels deviating significantly from normal conditions. However, the effects are expected to vary sharply from one region to another.
Cities including Jakarta and Surabaya in Indonesia, Phnom Penh in Cambodia, Bangkok in Thailand, Kuala Lumpur in Malaysia and Mumbai in India are expected to become progressively drier as El Nino strengthens, with the strongest events associated with the driest conditions recorded in the analysis.
In contrast, Shanghai and Hangzhou in China, as well as Colombo in Sri Lanka, have historically experienced wetter conditions as El Nino intensifies.
Meanwhile, Faisalabad and Karachi in Pakistan and Dhaka in Bangladesh sit between the two patterns and could experience conditions shifting in either direction, making preparations particularly challenging for authorities.
El Nino occurs when surface waters in the Pacific Ocean become warmer than normal, disrupting the movement of moisture around the world. Depending on their location, some areas can experience increased rainfall and flooding, while others face prolonged dry conditions.
The phenomenon typically occurs every five to 10 years, with its strength measured by how far sea surface temperatures deviate from their normal levels.
What makes the current situation particularly concerning is the projected scale of the event, which has been described as a ‘super’ El Nino. Meteorological agencies and researchers worldwide are closely monitoring the development as the phenomenon has strengthened at an unusually rapid rate.
Temperatures could reach as high as 3.6 degrees Celsius above normal, exceeding the previous monthly record of 2.75 degrees Celsius recorded during the 2015-2016 El Nino.
Researchers said there are no previous records that closely match the scale currently being forecast, making the potential size of its impact difficult to determine.
They stressed that although uncertainty remains over the severity of the effects, there is greater confidence in the likely direction of those impacts. Areas that typically become drier during El Nino are expected to face a greater risk of drought, while regions that tend to receive more rainfall could see an increased risk of flooding.
Professor Michael Singer of Cardiff University, one of the lead scientists involved, said a super El Nino would involve extremely large deviations in sea surface temperatures measured around the world.
He explained that such extreme conditions could cause moisture to move in highly specific patterns around the planet, increasing the likelihood of severe flooding in some areas while raising the risk of drought elsewhere.
