ENSO shows abnormal signs, Vietnam faces series of natural disasters

ENSO anomalies

ENSO (El Nino-Southern Oscillation) is a natural phenomenon that has a serious impact on the global climate system. ENSO consists of two opposite phases, El Nino and La Nina, the transition between these two phases occurs periodically every 2-7 years.

El Nino is used to describe the phenomenon of abnormal warming of the surface ocean water in the central and eastern equatorial Pacific Ocean, lasting 8-12 months (or longer), usually occurring every 3-4 years, but sometimes more or less frequently.

La Nina (the opposite of El Nino) is a phenomenon in which the surface water layer in the above mentioned area cools abnormally, occurring with a similar or less frequent cycle than El Nino. The cycle of La Nina usually lasts longer than El Nino.

In Vietnam, under El Nino conditions, the number of cold spells and the duration of their effects will be less than normal. At the same time, the average monthly temperature will be higher, the temperature difference in winter is more obvious than in summer, and the southern regions are more affected than the northern regions. On the contrary, under La Nina conditions, the average monthly temperature will be lower, and the northern regions will be more affected than the southern regions.

El Nino often causes rainfall shortages in most regions of the country, commonly 25-50% (most obvious in the North Central region), leading to a high risk of local or widespread drought in areas with high water demand for production and daily life.

In the context of global climate change, ENSO is showing abnormal manifestations in intensity and frequency of occurrence.

Mr. Nguyen Hong Sinh, Deputy Director of Hai Phong Hydrometeorological Station, said that El Nino and La Nina phenomena affect global weather and climate to different degrees and in a very diverse way. However, for each specific region, it is still possible to identify the main and characteristic impacts of each of the above phenomena.

These two phenomena represent anomalous fluctuations in the atmosphere-ocean system on interannual time scales, with cyclical or quasi-cyclical characteristics.

"In recent years, ENSO has appeared more frequently.

The impact of ENSO may vary from region to region. However, it should be noted that ENSO is not the only factor affecting climate and weather in Vietnam, but also interacts with other factors such as local climate and global climate change.", Mr. Sinh emphasized.

Taking a specific example of climate change caused by ENSO, according to the Deputy Director of the Hai Phong Center for Hydro-Meteorological Forecasting, as a coastal city in the Northeast region, in recent years, Hai Phong has been clearly affected by climate change.

This is reflected in prolonged and unusual cold spells, along with historically high summer temperatures. Storms, tropical depressions and other dangerous weather phenomena are occurring more frequently and with greater intensity.

Mr. Sinh cited some typical cases such as January 2016, Hai Phong recorded a historic cold spell lasting 6 days from January 23-28. The lowest temperature in history was observed on January 24 at Phu Lien Meteorological Station at 4.5 degrees Celsius.

On June 3, 2017, Hai Phong recorded exceptionally severe heat with the highest temperature reaching a historical threshold of 39.5 degrees Celsius.

On New Year's Eve 2020 (January 24, 2020), hail appeared in the northern mountainous region from noon to evening, until the night of the same day and into the early morning of January 25. Hail appeared in the midlands and coastal areas (including Hai Phong). On January 25 (the first day of the Lunar New Year), Hai Phong had heavy to very heavy rain. This is a rare phenomenon on the first day of the new year.

According to information from the Ministry of Natural Resources and Environment, in recent years in our country, extreme climate phenomena continue to be recorded with greater intensity and higher frequency.

Observation data over 60 years (1958 - 2018) show that: The average annual temperature across the country increased by about 0.89 degrees Celsius; rainfall decreased in the northern regions by 1-7% and increased in the southern regions by 6-21%; the number of strong storms increased; the highest and lowest daily temperatures increased.

Monitoring data also show that the number of hot days has increased in most areas; droughts have increased nationwide; the number of days with severe cold has decreased; extreme rain has increased; the average sea level of coastal and island stations has increased by 2.74 mm/year, with an increase of 3.0 mm/year in the period 1993 - 2018 alone.

According to Mr. Lam, this summer, provinces and cities across the country will experience hot and extremely hot weather. The heat in the North will be concentrated in May and June, while the heat in the Central region may last until July and August.

The South is currently experiencing widespread heat waves and the peak of the heat waves in this area occurs in March and April. Heat waves in the South, the Northwest, the North and the Central regions are likely to come earlier and appear more frequently and more severely than the average of many years.

According to the Deputy Director of the National Center for Hydro-Meteorological Forecasting, in 2024, from around the end of June, the storm season in the East Sea may begin. This year's storm season will be mainly influenced by the La Nina phase. Therefore, storms will be more concentrated in the last months of the year (from around September to November).

Along with the storms concentrated at the end of the year, heavy rain will also occur frequently in the Central region, especially the Central and South Central regions.

With the La Nina scenario appearing, developing as forecasted and starting to impact our country right at the time when rain and storms are concentrated in the Central region, the storm, rain and flood season in the second half of 2024 may have many complicated developments that require attention and response.

According to the meteorological agency's forecast, 2024 is likely to have more hot days than the average of many years. However, the probability of reaching a record temperature exceeding or equaling 2023 is not high. Explaining this, Mr. Lam said that because El Nino was relatively weak at the beginning of this year and will quickly transition to a neutral phase, its impact will be weaker than in 2023.

Besides, it is still the dry season nationwide, especially in the Central Highlands and the South.

“With the temperature continuing to rise and humidity low in the coming time, there is still a risk of widespread forest fires in mountainous provinces, especially along the western strip from the Northwest, North Central, Central Central regions extending down to the Central Highlands.", Deputy Director of the National Center for Hydro-Meteorological Forecasting analyzed.

In addition, the National Center for Hydro-Meteorological Forecasting said that this year, saline intrusion is higher than the average of many years. The deepest saline intrusion occurred from March 8-13, penetrating 40-66km deep, and in some places deeper, such as Tien Giang and Ben Tre provinces, penetrating 70-76km deep.

In particular, in the Ben Tre area and Co Chien River, salinity intrusion is deeper than in 2016. In addition, canals in some provinces in the Mekong Delta are experiencing dryness.

The cause of drought and saltwater intrusion in the Mekong Delta is primarily due to the impact of the El Nino phenomenon. Since the beginning of 2024, this area has had almost no rain (60-95% below standard), and prolonged sunny days have caused a large amount of surface water stored in fields, canals, rivers, and lakes to evaporate.

At the same time, water resources from the upper Mekong River to the Mekong Delta are lower than the average of many years, combined with the high tide period, pushing saltwater deep into the fields.

The meteorological agency forecasts that the rainy season in the South will likely start later than the average of many years, around the middle of May. Therefore, in the coming time, severe heat will still occur in this area with high temperatures.

According to new research published in the journal Scientific Reports, there is a 90% chance that the average global surface temperature will hit a record high for the year by June. Some places will experience hotter, more severe summers, especially parts of Asia. The heat increases the risk of drought and wildfires.

The ENSO statistical series has recorded super strong El Nino events in 1982-1983, 1997-1998, 2015-2016, of which the 2015-2016 El Nino was the strongest. This is recorded as the year with the highest global average temperature in the observation series.

Recent strong La Nina events were in 1998-2000, 2007-2008, 2010-2011.

According to NOAA (National Oceanic and Atmospheric Administration), whether we are in a La Nina year, an El Nino year, or neither (an ENSO neutral phase), is determined by sea surface temperatures near the equator in the Pacific Ocean.

On average, every 2–7 years, sea surface temperatures in the tropical Pacific Ocean switch between El Nino and La Nina phases, then pause in a neutral phase in between.

ENSO states directly influence temperature, rainfall, and wind patterns across the tropics, and have indirect cascading effects on a global scale.

The most recent strong El Niño in 2015-2016 coincided with a record-breaking hot year, causing widespread drought, wildfires, flooding and agricultural disruption, leading to ecosystem instability in some regions.

Estimates from the United Nations show that this El Nino phase significantly affects the lives of more than 60 million people due to socio-economic losses, migration, disease outbreaks and food insecurity.

Record-breaking global temperatures have been recorded even during La Nina years, demonstrating the long-term warming trend caused by climate change. For example, the La Nina year of 2022 ranks as the fifth warmest year on record.

In the near future, a series of El Niño indices are forecast to be high, and the world is likely to experience climate instability equal to or greater than that of 2016, with widespread flooding and drought. Experts predict this will cause huge economic losses and food insecurity.

Studies also show that current sea surface temperatures caused by El Nino are about 10% higher than pre-1960 levels, and predict that the frequency of extreme El Nino events could double this century due to faster surface warming in the eastern Pacific.

Additionally, the cycle to switch from El Nino to La Nina and vice versa can last for decades.

In addition, although the connection is unclear, El Nino, combined with climate change, could have a compounding effect. The combined effects of both rising temperatures and El Nino are predicted to cause record-breaking global temperature rises and increase the likelihood of catastrophic weather events.