Floods devastated Eastern parts of Sri Lanka. Similar extreme rainfall was experienced in 2008 damaging the havest of many parts of Sri Lanka. This article published on SundayTimes on 30.03.2008 explores the La-nina effect and future dangers by Climate Change..
——- published on 30.March.2008 —————-
March is usually a hot month but heavy rains have lashed Sri Lanka this year. Meteorologists believe the prevailing weather is due to the La Nina conditions in the Pacific – Malaka Rodrigo reports
The price of rice had risen. Surveying his paddy fields in Anuradhapura, Punchi Banda had high hopes that he could sell his crop for a better price this year. He hoped that at least part of the debt that had been accumulating for years could be settled with this money. The paddy was ready for harvesting.
Then came the rains. Punchi Banda could only pray to the weather gods. The continuing heavy rain flooded his paddy field and the ‘ready to harvest’ paddy was soon underwater. “It never rained during the harvesting period like this before,” he said in despair. The Maha harvest looked promising this time, but hundreds of paddy farmers like Punchi Banda now face the same fate in many districts because of the unseasonal rains.
March is traditionally a drier period for Sri Lanka between the north-eastern monsoon and the inter-monsoonal rains. The earth’s movement exposes Sri Lanka directly to the sun during this month, bringing swinging heat waves across the country. This year, the weather gods had different plans. Why? Is the unusual weather linked to the global warming phenomenon?
Weather experts at the Meteorology Department believe these unseasonal rains have been caused by conditions related to the phenomenon known as La Nina – meaning ‘girl child’ in Spanish. The phenomenon, which is said to have an impact on global weather patterns, takes place when there is a drop in the sea-surface temperatures in the central and eastern tropical Pacific Ocean.
The large-scale variations in atmospheric pressure between the Pacific and the Indian oceans affect the trade winds. When the wind moves across large oceans, it absorbs water that later comes down as rain or storms. Recently there has been a change of temperature in the eastern seas near Indonesia/Sumatra which is believed to be due to the La Nina phenomenon.
The famous El Nino is the opposite condition of La Nina and usually brings drought conditions to countries like Sri Lanka. Climatologists say that during the last century El Niño and La Niña events occurred in equal numbers with an average return period of about four years. They usually last about a year and peak in the northern hemisphere winter. But there seems to be a change of the patterns. Scientists are still looking for a Global Warming “fingerprint” on El Nino La Nina conditions. But many believe it is likely we will see more El Nino/La Nina because of global warming.
The Intergovernmental Panel on Climate Change (IPCC) – the UN’s scientific arm studying climate change — warned that the frequency of extreme weather patterns like heavy rainfall will increase due to global warming.
IPCC vice chairman Mohan Munasinghe says the recent changes in weather patterns in Sri Lanka are consistent with climate change. He also points out that we do not as yet have the detailed climate change models specific to Sri Lanka, to prove these phenomena.
According to Prof. Munasinghe, who shared the Nobel Peace prize on behalf of IPCC for its work on climate change, the need of the hour is to build a climate change model for identifying the patterns. The Meteorology Department established a special unit called ‘The Centre for Climate Change Studies’ (CCCS)’ to research climate change patterns impacting on Sri Lanka. Established by a special Cabinet Memorandum in 1999, the unit’s main tasks include research, monitoring, gathering and dissemination and execution of models of climate change. Though having initially conducted some research, of late, the CCCS has been dormant.
Even the UNDP – the United Nation’s body on poverty alleviation — in its Human Development report, points out that the economies based on agriculture would be badly hit. Unfortunately, paddy farmers in Sri Lanka had to taste this bitter truth during the last few weeks.
“This time, the rain is devastating,” said Anuradhapura’s Senior Irrigation Engineer Frankie Perera. He says disturbances to paddy cultivation due to heavy rains or prolonged drought conditions have increased over the past few years.
Mr. Perera says the sudden heavy rains are of little use to the irrigation systems. Heavy rain fails to fill irrigation tanks which are the lifeline for paddy farming. The irrigation tanks depend on the seeping water that slowly flow from catchments areas. Sudden intensified rain doesn’t give time for the soil to absorb water and it just flows to the river system. It also causes soil erosion and fills the canal system with mud.
Paddy farming needs a spread-out rainfall and the traditional Yala and Maha seasons are designed according to such predictable weather patterns. The despondent farmers like Punchi Banda battling to save their harvest would not have any clue of La Nina, El Nino or global warming. Many of them will never know about the “child girl” that brought trouble for them. They can only pray for a better Yala season. But will the next season too be affected? Will there be a drought instead of unexpected rain? With global warming and climate change, nothing appears to be predictable.
La Niña is a phenomenon that occurs due to cooler sea-surface temperatures in the central and eastern tropical Pacific ocean. During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 0.5 °C. Like La Nina means “little girl”, the El Nino meaning “little boy” in Spanish is the opposite. During El Nino, the sea surface temperature will be higher than normal, atleast by 0.5 °C .
What are the global impacts of La Niña?
Both El Niño and La Niña impact on global climate patterns, the tropics being especially vulnerable. For instance, some parts of Asia can be prone to drought during El Niño, but are typically wetter than normal during La Niña.
How are sea surface temperatures monitored?
Observations of conditions in the tropical Pacific are essential for the prediction of climate variations. Sea surface temperatures in the tropical Pacific Ocean are monitored with data buoys and satellites.
To provide necessary data, a network of buoys that measure temperature, currents and winds in the equatorial band are set up in the ocean. These buoys transmit data that are available to researchers.