As El Niño exits, La Niña looms

As El Niño exits, La Niña looms

Workers unload sugarcane tops at a cattle shelter in Beed district, Maharashtra, India, on April 15, 2016. Hundreds of millions of people in India are grappling with one of the nation's worst droughts since independence, following two years of poor rainfall and the intense summer heat. (Bloomberg photo)
Workers unload sugarcane tops at a cattle shelter in Beed district, Maharashtra, India, on April 15, 2016. Hundreds of millions of people in India are grappling with one of the nation's worst droughts since independence, following two years of poor rainfall and the intense summer heat. (Bloomberg photo)

BOSTON — Think of it as Mother Nature's roller-coaster ride: the shift between the weather patterns known as El Niño and La Niña that, at their worst, can cause havoc worldwide.

El Niño — spurred on by a warming of the equatorial Pacific — has dried up rice crops across Southeast Asia, cocoa fields in Ghana, coffee in Indonesia and sugar cane in Thailand since last year. It contributed to the Western Hemisphere's strongest hurricane on record and the planet's warmest year since at least the 1880s.

Now the ocean's surface is starting to cool, which may signal the start of a La Niña. Scientists say this pattern typically contributes to more hurricanes in the Atlantic, drought in Brazil and heavy rain in Indonesia and India. While it might give a boost to US natural gas, it could hurt Australian coal operations and palm-oil output in Malaysia. For some areas, it may be worse than a typical El Niño.

"El Niño extremes are greater, while La Niña lasts longer," said Kevin Trenberth, distinguished senior scientist at the National Center for Atmospheric Research in Boulder, Colorado.

The cycles occur every two or three years on average and help regulate the temperature of the Earth as the equatorial Pacific absorbs the heat of the sun during the El Niño and then releases it into the atmosphere. That can create a La Niña: a "recharge state" when "the whole Earth is cooler than it was before this started," Mr Trenberth said.

Forecasters on two continents have issued La Niña watches for this year. Australia's Bureau of Meteorology says the odds are about 50%. The US Climate Prediction Center's bet is 75% by December, but it says formation also could come earlier: sometime from July to September.

Peruvian fisherman centuries ago were first to notice the ocean would often warm late in the year. They called the phenomenon El Niño, after the Christ child. Modern researchers came to realise its importance to global weather in the 1960s, when they recognised the link between warm surface water and corresponding atmospheric changes. They tweaked the name to El Niño/Southern Oscillation. La Niña was named about two decades later.

The patterns aren't simply opposite sides of the same coin. "La Niña is more like a strong case of 'normal'," Mr Trenberth said. If a region is typically dry, it could become arid in a La Niña. If it's usually wet, there may be floods.

Greater intensity

So far, the US hasn't tried to predict how strong a La Niña might be. For both parts of the cycle, greater intensity means greater impact. The ebbing El Niño was one of the three strongest on record, spurring the growth of Hurricane Patricia last year, which clocked winds exceeding 322km per hour before going ashore in Mexico.

Las Niñas typically produce more hurricanes, but that may not mean more losses: What matters most is where the storms hit, according to Peter Hoeppe, head of Munich Re's Geo Risks Research/Corporate Climate Center in Germany. And Las Niñas actually have lowered the Atlantic hurricane count in some years by bringing more African sand storms - which reduce the moisture hurricanes need - and cooler water into the tropics, he said.

Commercial and academic forecasters have said La Niña probably will cause a slightly above-average year for tropical storms and hurricanes. The 30-year normal for the June 1-to-Nov 30 season is 12. Last year, 11 storms rose out of the Atlantic. The year before, when the El Niño was trying to get started, only eight were named. One storm, Alex, already formed this past January. (Story continues below) 

Tree stumps usually underwater stand in and around cracked earth and a pool of water at the dried up Mae Jok Luang reservoir in Chiang Mai on April 23, 2016. (Bloomberg photo)

United States

While El Niño can produce a milder winter across the northern US, La Niña often brings chills to the Pacific Northwest, northern Great Plains and parts of the Midwest. For places like Iowa, a major source of corn and soybeans, timing is key, said Harry Hillaker, the state's climatologist. If a La Niña occurs early in summer, there's a chance for hot and dry weather, which can hurt the plants as they are pollinating.

Natural-gas producers in the US "would really like La Niña," said Teri Viswanath, managing director for the commodity at PIRA Energy Group in New York. They hope it will produce warmer temperatures in summer and the possibility for cooler temperatures in winter. "A cool winter, wow, that would be really helpful."

UK and Europe

For Europe, the energy prospects are more muddled. From November to December, the phenomenon could mean colder temperatures and thus higher fuel demand.

"It's also the case that we get the unfortunate relationship of lower wind speeds during that period, so that could mean we get lower wind power," said Hazel Thornton, manager of the UK Met Office's climate-change adaptation team. After the New Year, the pattern in Europe would typically flip, with temperatures becoming milder and wind increasing.

Brazil

For Brazil, La Niña is more dangerous than El Niño because it hits crop production "hard," said Eduardo Assad, a climate researcher at Brazil's state-run agricultural research company, Embrapa. That's because it can bring drier conditions, which also could damage the water supply, worsening São Paulo's water crisis, he said.

Brazil tops the world for soybeans and oranges, and São Paulo is one of the cities hosting football matches for this year's Olympic Games.

India

For India, La Niña "means good rains," said Atul Chaturvedi, chief executive officer of Adani Wilmar Ltd, a refiner and retailer of cooking oils. "India has been reeling with poor rains for almost two years now, so La Niña for all practical purposes should be a boon."

It might come too late to enhance this year's monsoon, however, said Dave Streit, chief operating officer for the Commodity Weather Group LLC in Bethesda, Maryland.

Malaysia

It also may come too late to help this year's palm-oil crop in Malaysia, with futures there rising in February to the highest in eight years.

"There is no way the emergence of La Niña, or just normal weather, will undo the damage done by El Niño," said Ling Ah Hong, director of Malaysian plantation consultant Ganling Sdn in Kuala Lumpur. "This is something a lot of people misunderstand."

An extreme La Niña could cause yields to fall. Flooding hurts the ability to harvest and reduces the quality of fruit, said Roy Lim, group plantations director at Kuala Lumpur Kepong Bhd., Malaysia's third-largest producer.

Australia

For Australia, the "main negative impact" from La Niña is heavy rainfall and "a disproportionate number of major flood events," said Blair Trewin, a climatologist with the national Bureau of Meteorology.

In 2010-11, the pattern triggered so much rain that 85% of the continent's coal production was hit by flooding. Spot prices of metallurgical coal jumped to $383 by the start of 2011 from $212 per tonne in the third quarter of 2010, Mark Levin of BB&T Capital Markets said in a May 10 note to clients.

La Niña returned in 2011-12, helping to boost wheat production to a record 29.9 million tonnes. It also caused vegetation to flourish in the usually arid interior - which fuelled widespread grass fires when the rains stopped.

While the world waits to see if a La Niña will develop, there's always a chance it could fizzle. Forecasters were certain an El Niño would form in 2014, only to see it fall apart. The prediction models are better around June and July than they are now, according to Michelle L'Heureux, a forecaster for the Climate Prediction Center.

So stay tuned.

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