Persistent La Niña Is Back Again — And Driving Up Food Prices

By Stephen Leahy *

UXBRIDGE, Canada, Oct 11, 2011 (Tierramérica)

La Niña is back less than three months after the end of its last appearance, a particularly strong event that contributed to driving up global food prices.

The new La Niña will continue the largely dry conditions in important agricultural regions in Brazil and Argentina as well as the southern United States and hurt yields of soy and wheat, experts say.

“Multi-year La Niñas are not uncommon,” said Jeff Masters, co-founder and director of meteorology for Weather Underground, the web’s first commercial weather service.

“The last was between 1998 to 2001 with a few months of neutral conditions like this year,” Masters told Tierramérica.

La Niña and El Niño are, respectively, the cold and warm phases of the famous El Niño-Southern Oscillation (ENSO), a cyclical climate phenomenon that affects weather patterns around the world.

ENSO is part of the system that regulates heat in the eastern tropical Pacific Ocean and is driven by changes in surface ocean temperature and air pressure.

“ENSO is undoubtedly being affected by climate change,” said Masters.  Continue reading

Now Historic Flooding Hits Southern Australia

[UPDATE 19 Jan – 25 % of state of Victoria underwater]

While flood levels drop in Queensland and Brisbane, Australia’s state of Victoria has now been hit with historic levels of flooding.

A strong La Nina enhanced by global warming seems to be behind the record flooding in Australia, Brazil, Sri Lanka and elsewhere as documented in my earlier article. Part of the reason for the severity of the flooding is that the atmosphere now contains 4 per cent more water vapour as a result of the increased global temperature of roughly 0.8C.

As the planet continues to warm from the burning of fossil fuels floods will get worse, but so will droughts.

Climate Change Could Be Worsening Effects of El Niño, La Niña

Global Warming Worsening Impacts; Creating New ENSO ‘Flavors’

By Stephen Leahy*

UXBRIDGE, Canada, Jan 11, 2011 (Tierramérica) 

The strongest La Niña weather system in 50 years has brought historic flooding to Australia and drought to Argentina, Brazil and Uruguay, driving up food prices.

Scientists now believe climate change is likely enhancing the impacts of the famous El Niño-Southern Oscillation (ENSO), a cyclical climate phenomenon that affects weather patterns around the world.

La Niña and El Niño are, respectively, the cold and warm phases of the ENSO cycle, and form part of the system that regulates heat in the eastern tropical Pacific Ocean.

Both accompany simultaneous changes in surface ocean temperature and air pressure.

In conditions defined by climatologists as “neutral,” high air pressure predominates in the eastern Pacific, while low pressure predominates in the west.

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The difference in pressure generates the trade winds, which blow east to west over the surface of the tropical Pacific, pushing the warm waters westward. The deeper, cooler waters then surface in the east, replacing the warm waters.

During episodes of La Niña, the differences in pressure are more marked, the trade winds blow more strongly, and the cold-water currents in the eastern Pacific intensify.

On the other hand, during El Niño, high surface air pressure in the western Pacific and lower pressure on the coasts of the Americas cause the trade winds to weaken or change direction, resulting in warmer water temperatures in the eastern Pacific.

“There has been a very rapid transition from El Niño to La Niña in 2010,” Kevin Trenberth, a senior climate scientist with the National Centre for Atmospheric Research (NCAR) in the central U.S. state of Colorado, told Tierramérica. Continue reading