David Fogarty, Reuters 7 Jul 09;
SINGAPORE (Reuters) - Across the globe an emerging El Nino weather pattern threatens to cause droughts and floods and trigger a spike in planet-warming greenhouse gas emissions from burning forests.
El Nino is a warming of tropical Pacific waters that affects wind circulation patterns. Its effects on the global climate vary from one event to the next.
Trying to predict how El Nino will be affected by global warming is a major challenge, scientists say, although data shows El Ninos have become more frequent and more intense over the past three decades. The last event was in 2006.
"I don't think there are any studies that are saying El Nino will become less severe but there is disagreement among the climate models on whether they will become more severe or stay steady," said Matthew England of the Climate Change Research Center in Sydney.
Getting the forecasting right is crucial for farmers in planning their crops, and even for the oil industry in assessing storm risks in the Gulf of Mexico.
"Certainly we know from past climates that El Nino intensity has varied. As climate changes, we know that the intensity of El Nino can wax and wane over long time scales," he said.
Australia's Bureau of Meteorology said last week an El Nino was almost certain this year and the signs point to one already well underway. A formal declaration could be within days.
(For more details see the bureau's website at: www.bom.gov.au/climate/enso/)
One of the biggest threats from El Nino comes from the release of vast amounts of greenhouse gases through the burning of dried out forests.
Scientists say there is very strong correlation between El Nino and drought in Southeast Asia, which has large areas of carbon-rich peat forests.
"People are waiting for appropriate conditions to get rid of the forests," said Pep Canadell of the Global Carbon Project in Canberra.
"So the drier the El Nino the more incentive there is for people to take advantage of those unique conditions," he said. Most of the burning occurs in Indonesia.
SPIKE IN TEMPERATURES
During the very intense El Nino of 1997/98, fires in Southeast Asia released between 2.9 billion 9.4 billion tonnes of CO2, blanketing the region in a choking haze. The smoke equated to between 15 and 40 percent of global fossil fuel emissions and is credited with causing a spike in global temperatures.
By comparison, average annual emissions from forest fires in Southeast Asia between 2000 and 2006 were 470 million tonnes of CO2, while average fossil fuel emissions for the same period in the region were 543 million tonnes of CO2, said Canadell.
Over the past two years, forest fire emissions have plunged because of wet weather.
"I think the next El Nino we have here in Southeast Asia is going to be a big one in terms of emissions," said Canadell, whose project issues annual reports on the planet's "carbon budget."
"The longer it takes for an El Nino to come, the bigger the emissions will be because the more people will be keen in burning because they have been waiting all this time."
The effects of the current El Nino, if confirmed, could already be apparent in the weakening of equatorial trade winds that normally blow strongly east to west and in the amount of cloud in the eastern Pacific.
"As El Nino is developing right now we should start to experience its impacts as we speak," said Harry Hendon, a senior climate scientist at the Bureau of Meteorology in Melbourne.
"Historically our biggest impacts are in the (southern) spring. But we start to see them as early as winter," he said.
SAME BUT DIFFERENT
Normally, warm ocean water is piled up in the Pacific around east Asia causing rain and moisture-laden winds that flow over parts of Australia.
But during El Nino, the warm waters migrate east toward South America, taking the wet weather, often causing floods in Colombia, Ecuador and elsewhere.
It's unclear how intense the next El Nino will be but Hendon said even weak El Ninos can have a dire impact on rainfall in Australia, depending on where the warm water pool was in Pacific.
"El Ninos that are peaking in the central Pacific have a bigger negative impact on rainfall on Australia than El Ninos that peak further east," said Hendon.
Complicating the picture, scientists now know there are at least two types of El Nino, one in which the warm waters pile up against the Pacific coast of equatorial South America, and the other in which warmest of the waters are in the central Pacific.
Scientists from the Georgia Institute of Technology in the United States released a study last week showing that periodic warming of the central Pacific was linked to an increase in Atlantic hurricanes, a finding that could change the way oil firms assess storm risks for operations in the Gulf of Mexico.
Previously, El Ninos in general were thought to suppress hurricane activity, but the latest research suggests this is only for episodes where the warmest waters are off the South America.
"The fundamental problem is we don't simulate El Nino very well with our existing climate models," said Hendon. "That makes it a real challenge to run your model for a future climate and see how El Nino will behave."
(Editing by Alex Richardson)
El Nino developing slower, India monsoon to stay weak
Michael Perry, Reuters 7 Jul 09;
SYDNEY (Reuters) - A key measure of El Nino weather patterns eased in June, suggesting the potentially damaging condition may be developing slowly, although India's monsoon will remain weak, Australia's weather bureau said.
An El Nino, which means "little boy" in Spanish, is driven by an abnormal warming of the eastern Pacific Ocean, and creates havoc in weather patterns across the Asia-Pacific region.
The Southern Oscillation Index (SOI), a key factor in identifying an El Nino that is calculated from monthly and seasonal fluctuations in air pressure between Tahiti and Darwin, eased in June to negative 2 from a negative 5 in May, the bureau said on Tuesday.
A sustained negative SOI often indicates El Nino, a condition that can bring drought conditions to Australia's farmlands, weaken the Asian monsoon critical for Indian crops, stir up storms in the Gulf of Mexico and cause flooding in Latin America.
"Minus 10 is an often used threshold level and it just got to there a few times, but it hasn't been sustained at that level," Sam Cleland, author of the Bureau of Meterology's weekly Tropical Climate Note, said on Tuesday.
"I don't think we'd make the call just yet that we have an El Nino event in place," he said ahead of the bureau's El Nino update on Wednesday.
Its last report said an El Nino was very likely in 2009 and may be declared in coming weeks. The last El Nino was in 2006.
David Palmer, a meteorologist at private forecasting firm the Weather Company says indicators suggest there is a 60 percent chance of an El Nino developing in August, the month when it usually can be determined whether the weather pattern exists.
"We've been suggesting for some time now that there is an El Nino developing but it is not until August that you can say that for sure," said Palmer.
"If I were a betting man I would be putting my money on it."
But Cleland said the Pacific trade winds, another key El Nino factor, had also weakened in June.
"The equatorial Pacific Ocean continues to develop into a more El Nino like pattern," said Cleland, manager of climate services at the bureau's Darwin office.
"To call an El Nino or not is difficult and it takes a number of parameters over a sustained period. The formal definition of an El Nino often occurs in hindsight," he said.
The last severe El Nino in 1998 killed more than 2,000 people and caused billions of dollars in damages to crops, infrastructure and mines in Australia and Asia. It came in the middle of the Asian crisis that roiled financial markets.
India, one of the world's biggest producers and consumers of everything from sugar to soybeans, is already experiencing a weaker annual monsoon. Its faltering sugar crop has helped drive world prices of the commodity to their highest in three years.
India's monsoon will remain weak according to the latest Madden-Julian Oscillation (MJO) index, which gauges the eastward progress of tropical rain, Cleland said. It was too early to get a read on the potential intensity of a new El Nino, he added.
"There's no strong indication at this stage of what level of impact this ENSO event could have," he said, adding that some weak El Ninos have had severe impacts on Australia rainfall, while stronger El Ninos have only had marginal impacts.
(Additional reporting by Bruce Hextall)
(Editing by Clarence Fernandez)
El Nino "boy child" developing slowly
Rueters 7 Jul 09;
SYDNEY (Reuters) - An El Nino weather pattern that could bring drought to Australia's farms and weaken Asia's monsoons, severely disrupting crop and livestock production, is developing slower, Australia's weather bureau said on Tuesday.
Here are some facts about the El Nino and La Nina weather patterns in the Pacific.
PACIFIC OCEAN
The Pacific Ocean is a huge mass of water which controls many climate features in its region. Its equatorial expanse, far larger than the Indian or Atlantic Oceans, is critical to the development of an El Nino.
In most years relatively cold water moves northward along the west coast of South America, an effect increased by upwelling or rising cold water along the Peruvian Coast. The cold water then flows westward along the equator and is heated by the tropical sun. These normal conditions make the western Pacific about 3-8 degrees Celsius warmer than the eastern Pacific. EL NINO OR BOY CHILD
El Nino translates from Spanish as "the boy-child."
Peruvian fisherman originally used the term -- a reference to the Christ child -- to describe the appearance, around Christmas, of a warm ocean current off the South American coast.
El Nino now refers to the extensive warming of the central and eastern Pacific that leads to a major shift in weather patterns across the Pacific.
El Nino benefits traditional fisheries in Peru and Ecuador, with colder nutrient-rich water from the deeper ocean drawn to the surface near the coast, producing abundant plankton, food source of the anchovy. However, when the upwelling weakens in El Nino years and warmer low-nutrient water spreads along the coast, the anchovy harvest plummets. It was ruined in the four or five most severe El Nino events this century.
In Australia (particularly eastern Australia), El Nino events are associated with an increased probability of drier conditions and severe El Ninos have caused widespread drought, decimating Australia's crops and livestock, and bushfires.
Asia's monsoons are weakened by El Nino and can severely impact vital food production in India and Indonesia.
SOUTHERN OSCILLATION INDEX
The Southern Oscillation Index (SOI) gives a simple measure of the strength and phase of El Nino and La Nina.
The SOI is calculated from the monthly or seasonal fluctuations in the air pressure difference between Tahiti in the eastern Pacific and Darwin in northern Australia.
SOI close to zero indicates a normal Pacific weather pattern.
A sustained negative SOI often indicates an El Nino. A negative SOI means the seas around Australia cool, trade winds weaken and feed less moisture onto Australia and Asia.
A positive SOI reflects a La Nina episode. A positive SOI are associated with stronger Pacific trade winds and warmer sea temperatures to the north of Australia, meaning a high chance that eastern and northern Australia will be wetter than normal.
LA NINA OR GIRL CHILD
La Nina translates from Spanish as "the girl-child" and is the meteorological label for the opposite of El Nino.
The term La Nina refers to the extensive cooling of the central and eastern Pacific Ocean. La Nina events are associated with increased probability of wetter conditions in the western Pacific, particularly in eastern Australia and Asia.
For the latest report, see: www.bom.gov.au/climate/enso/.
Source: Australia's Bureau of Meteorology here
(Editing by Ben Tan)
