Floods in eastern Bolivia.
Credit: Franz Chávez/IPS
La Niña and Climate Confusion
By Daniela Estrada*
While the climate cycle known as La Niña gradually winds down over the equatorial Pacific, its local consequences have surprised experts in the countries most affected.
SANTIAGO, Mar 10 (Tierramérica).- It is still difficult to predict the local impacts of the cyclic climate phenomenon known as La Niña, which has been responsible for catastrophic floods in Bolivia, Ecuador, Peru and Argentina, and -- on the other extreme -- severe drought in Chile.
The death toll has already reached about 100, and around one million people have been affected by the floods and drought.
"La Niña" and "El Niño" are the extreme phases of the oceanic-atmospheric phenomenon known as "El Niño-Southern Oscillation" (ENSO), which takes place in the equatorial region of the Pacific Ocean every two to seven years, affecting many regions around the world to varying degrees.
La Niña is characterized by an atypical cooling of the surface waters of the ocean and an increase in the winds blowing east to west at the equator. The better known El Niño is the opposite: warmer surface waters and weaker winds.
La Niña tends to provoke intense rains in Colombia, Ecuador, the high plains of Bolivia and Peru and northwestern Argentina, and drought in Uruguay, southern Brazil, northeastern Argentina and central Chile.
According to Jorge Carrasco, chief of Chile's weather and climate department at the government's Meteorological Directorate, the current La Niña episode began in May-June 2007 and is expected to conclude between June and August 2008, marking the beginning of a neutral period.
To predict the ENSO behavior, experts use historical data and dynamic and statistical climate models generated at centers in the United States, Europe and Asia, which have great computing capacity, Carrasco told Tierramérica.
The information generated by those centers is available to everyone over the Internet.
"Nearly all the countries (of South America) have quite broad knowledge of the rain patterns associated with the presence of El Niño and La Niña in their own territories, especially Peru, Ecuador and Colombia," said the expert.
Nevertheless, "one must keep in mind that the interaction of the atmosphere with the ocean is not linear, and that means that one El Niño or La Niña event is never identical to another," Rosa Compagnucci, professor of natural sciences at the University of Buenos Aires, told Tierramérica.
"Although we can predict in advance and with some certainty the occurrence of an event -- and in some cases even its potential intensity -- it is more difficult to predict its local impact," added the atmosphere and ocean expert.
La Niña now under way has been an atypical manifestation in Chile. Experts say there should have been heavier rainfall in the central region of Araucanía during the austral summer months, but it never came. Across the country, 144 municipalities have declared agricultural emergencies from the effects of the drought.
In Bolivia, La Niña has also surprised meteorologists because instead of hitting the high plains -- in the western departments of La Paz, Potosí and Oruro -- it has affected the entire country, but especially Pando, in the north, and Beni and Santa Cruz in the east, which had already suffered heavy floods a year ago caused by rains from El Niño.
"This is the first time we've conducted a more exhaustive monitoring of La Niña, because about the previous ones our information was quite general," said Gualberto Carrasco, head of the climate unit at Bolivia's national weather and hydrology service, known by its Spanish acronym SENAMHI.
"In the short term it's important to strengthen the early warning system," said the expert from SENAHMI, which is part of the Ministry of Sustainable Development and Planning.
"One of the difficulties Argentina faces is that the official forecasting agency, the National Meteorological Service, has dramatically reduced its science staff. If more meteorologists are trained there would be greater awareness of these events of great socio-economic impact," said professor Compagnucci.
Chilean expert Jorge Carrasco says the information produced by his country's Meteorological Directorate is presented to the relevant authorities on a regular basis, but he acknowledges that a greater effort could be made to provide basic information to the population about forecasts for droughts or floods to improve disaster prevention.
"There is sufficient information in terms of diagnosis and prediction (of the ENSO episodes). The models are not 100 percent correct, but in general they have a good record three months out. As a result, there are data available for making decisions both at the governmental and personal levels," he said.
Meteorology professor at the University of Chile, Patricio Aceituno, added that "now under discussion is how to prepare programs" to adapt to and to mitigate climate change caused by human activities. "These programs should be inserted into permanent plans for mitigation and management of extreme climate situations, like drought and floods," he told Tierramérica.
"There is still great uncertainty about the changes that are going to occur in the next 50 years (due to global warming), but I would bet, with 100 percent certainty, that in the next 10 years there will be a major drought or flood," he said.
The Chilean experts point out that another phenomenon acts upon ENSO, and is known as the Pacific Decadal Oscillation (PDO), which manifests itself over decades and is believed to determine the frequency of La Niña and El Niño.
Studies indicate that the positive phase of the PDO, which has been under way since the mid-1970s, is coming to an end. It is expected to begin its negative phase, in which La Niña events will be more frequent than El Niño.
But other lines of research suggest that beginning in 2008, "when the new cycle begins of the approximately 11 years of solar activity, the probability of an El Niño occurrence is on the rise, reaching maximum probability in 2012, the year, according to predictions of (the U.S. space agency) NASA, expected to have maximum solar activity," said Compagnucci.
* With additional reporting by Marcela Valente (Argentina) and Bernarda Claure (Bolivia).