Trends in the number of hot days in 7 climate zones over 60 years
One day in late May, at 7am, the temperature outside in Hanoi was already 35 degrees Celsius. Mr. Hoang Hai Nam, 50 years old, an electrician, and his colleagues started their work two hours earlier to avoid the scorching midday sun. But by 10am, the heat from the road surface was already sweltering. He felt like he was working at 40-50 degrees Celsius. His eyes were burning.
"It's terribly hot, like in a boiler," Mr. Hai complained.
Hanoi entered a particularly hot summer right from the beginning of summer - something that has not been unusual in recent years. On May 18, the Ha Dong meteorological station recorded 41.3 degrees Celsius - a historic mark for May in more than 30 years. But this is not the highest temperature in the country. Before that, many records were broken one after another. Hoi Xuan station (Thanh Hoa) was 44.1 degrees Celsius on May 6, the highest in Vietnam in 65 years. The next day, Tuong Duong station (Nghe An) set a peak of 44.2 degrees Celsius.
Mr. Hoang Hai Nam, 50 years old, electrician at Gia Lam District Electricity Company (Hanoi), on a working day at the end of May. Photo: Gia Chinh
Over the past few years, every time summer comes, Mr. Nam's life cycle changes. He leaves home at 4am instead of 7am, and tries to complete his tasks as quickly as possible. Having worked as an electrician for 15 years, he has clearly felt the extremes of the weather through the increasing workload. On hot days, the number of calls reporting electrical problems to the switchboard is 3-6 times higher than usual.
"The more the temperature rises, the more we have to go out," he concluded, wiping sweat from his forehead. "The sun is terrible. It seems like the days are getting longer and more intense."
The 50-year-old's memories of summers a decade ago rarely include the "endless" and exhausting heat waves of recent years.
Data from the Ha Dong meteorological station (Hanoi) from the 90s shows that the entire summer only had a few days of intense heat (37-39 degrees Celsius). By August, Hanoi entered autumn. The number of extremely hot days only increased sharply in 2004 and 2010 - years with the El Nino phenomenon, a climate pattern of increased sunshine and less rain, usually lasting 8-12 months and appearing every 3-4 years. But since 2014, Hanoi has continuously faced summers above 37 degrees Celsius, even reaching 42.5 degrees Celsius.
Temperatures are also rising across the North and Central regions. Summers are getting longer, more intense, and constantly reaching new levels of severity.
The peak of summer usually falls between March and May in the South and May and July in the North and Central regions. However, data collected by VnExpress in 12 localities across the country shows that over the past 30 years, many places have recorded heat waves outside this rule.Many localities have experienced unusual heat waves.
Along with the lengthening summer, the number of hot days (35 to 37 degrees Celsius) tends to increase at stations in the North and Central regions such as Viet Tri (Phu Tho), Ha Dong (Hanoi), Vinh (Nghe An), Ha Tinh. The number of hot and extremely hot days has increased significantly from 2017 to present. Meanwhile, although the South has the highest average annual temperature in the country, the heat rarely reaches severe levels.
Number of hot , extremely hot , and extremely hot days at 12 meteorological stations from 1991 to present
Statistics from the United Nations Intergovernmental Panel on Climate Change (IPCC) show that the average global temperature is increasing. Vietnam shares this trend, however, the rate of increase is 38% faster, according to data on temperature differences in the period 2006-2015 compared to the previous 20 years.
During the 2010-2019 period, Vietnam had the highest average temperature in 60 years. According to data from monitoring stations, 30% recorded new maximum temperatures. Of which, the Central region is the "hot spot" of the country. The three most recent temperature records were all in this region.
Having lived in the "fire pan" of Huong Khe (Ha Tinh) for more than 30 summers, the last decade has been the most difficult for Mrs. Nguyen Thi Bau (74 years old) and her husband. Summer is now "like a nightmare", with no way out from the heat.
Mrs. Bau and her husband and four grandchildren faced days of struggling due to lack of sleep. At noon, the sun baked the brick walls. The lychee tree in front of the house became a "shelter" for the grandmother and grandchildren, but it could not escape the scorching heat of the Lao wind. At night, she had to put a basin of water in front of the fan, but many days it was still not cool enough, the four children took turns crying, the couple in their 80s stayed up all night fanning the grandchildren to sleep.
Ms. Nguyen Thi Bau (74 years old, Huong Khe, Ha Tinh) and her two grandchildren avoid the heat under a lychee tree in front of their house. Photo: Duc Hung
Mrs. Bau’s generation rarely had to endure this heat. Coming here to reclaim land since 1990, she felt comfortable on most summer days. The whole family of seven spread out mats in the middle of the house, using only palm leaf fans to sleep soundly. But since 2010, she has clearly felt the change in heat when she had to buy an electric fan for each room. Even though it was on all night, she still sweated profusely, her mouth was dry from thirst. Sleep became shorter and shorter, and summer seemed to be getting longer.
"Thinking about the heat makes my skin crawl. I just hope there won't be a drought, the worst thing is the lack of water," Ms. Bau recalled about 2020.
At that time, Ha Tinh people had just experienced a year of record-breaking heat, reaching 43.4 degrees Celsius, and were facing an unprecedentedly long summer - lasting nearly two months. Daytime temperatures were always 39-40 degrees Celsius. The scorching heat caused fields to crack, wells to dry up, rivers and lakes to "evaporate", and crops to wither. Ha Tinh's thirst reached its peak.
For the first time, the well and the stream behind her house were dry, not a drop of water could be found. In the fiercest heat of June, she and her husband took turns getting up at 6am, going around the village to get water for cooking, and in the afternoon cycling to the ponds that had not dried up yet to bathe and wash. The work and rest schedules of many farmers in Ha Tinh were turned upside down. They went to the fields at night and returned home early in the morning, racing to "finish" before the sun rose to escape the scorching heat.
Satellite image of Ngan Pho River, Ha Tinh, drought year 2020 and present. Photo: Google Earth
Last April, Ha Tinh entered summer again with the highest temperature reaching 42 degrees Celsius, signaling a "boiling hot" season. Mrs. Bau fears that another record summer will push her hometown to the brink of drought.
"Heat is becoming more and more unusual and extreme due to human impacts," said Dr. Chu Thi Thu Huong, lecturer in Meteorology and Climatology at Hanoi University of Natural Resources and Environment.
Hanoi is a typical example. Over the past 10 years, the capital has witnessed extreme temperatures comparable to some provinces in the North Central region - places that often suffer from intense heat due to terrain characteristics and the impact of Lao winds.
"If it weren't for climate change, Hanoi's temperatures wouldn't be so extreme," Ms. Huong explained.
Climate change is the result of humans emitting greenhouse gases (such as CO2) into the environment. It acts as a "blanket" to retain the Earth's heat radiation, instead of emitting it into the atmosphere, causing the surface temperature and air temperature to increase, making the weather hotter and hotter. In cities like Hanoi, the heat is even more severe when concrete absorbs and retains heat, causing the urban heat island effect - a large temperature difference between the inner city and the suburbs. These factors combined with high humidity can make the perceived temperature 3-5 degrees Celsius higher than predicted.
In addition, temperatures tend to be higher in El Nino years. In six of the past seven decades, the hottest year of each decade has been an El Nino. The US National Oceanic and Atmospheric Administration (NOAA) estimates that there is a 93% chance that 2023 will be one of the five warmest years on record.
Statistics show that over the past 30 years, El Nino has occurred in 12 years, accompanied by an unusually long number of hot days. For example, in the El Nino cycle of 2014-2016, the North and South Central regions experienced a heat wave lasting 42 days (in 2014), the Central Central region experienced 35 days (in 2015) and the South experienced 60 days (in 2016).
The weather is expected to escalate further in the coming months as summer temperatures peak, and the El Nino phenomenon officially takes hold.
Ms. Pham Thi Thanh Nga, Deputy Director of the Institute of Meteorology, Hydrology and Climate Change (Ministry of Natural Resources and Environment) forecasts that this year the average temperature across the country will be about 1 degree Celsius higher than many years, with heat waves covering from Ha Giang to Thua Thien Hue. Each wave can last 5-7 days instead of the usual 3-5 days.
But even in years without El Nino, heat waves are becoming more intense. According to the World Meteorological Organization (WMO), the United Nations agency that monitors weather and climate, 2015, 2016 and 2017 were the three hottest years on record. Of these, 2017 was a year without an El Nino. Thirty years of data in Vietnam also show similarities.
Over the past 30 years, the trend of the number of heat waves has increased, even in years without El Nino.
Not only is there a lot of sunshine, El Nino also often causes a 25 to 50 percent rainfall deficit, with a trend that will last until 2024, according to Mai Van Khiem, Director of the National Center for Hydro-Meteorological Forecasting. Rainfall decreases, but it is more extreme and there may be records for rainfall in 24 hours. For example, in the year of El Nino 2015, Quang Ninh experienced a 10-day rainstorm, the largest in 50 years. The double impact of increased sunshine and reduced rain also leads to the risk of drought during the dry months, as happened in 2020, which caused a record drought in more than 100 years.
Rainfall trend decreases in El Nino years in most localities
"There is a possibility that this year will see many new temperature records," said Mr. Mai Van Khiem, adding that there is a 70-80% probability that El Nino will last until 2024.
The World Meteorological Organization (WMO) also warned that there is a 98% chance that the hottest year on record will be 2027, surpassing 2016. "The combination of human-caused climate change and the El Nino phenomenon in the coming months will push global temperatures to unprecedented levels," WMO Director Petteri Taalas warned in April.
During the El Nino season three years ago, Mrs. Bau's family suffered heavy losses. 3,000 square meters of oranges and grapefruits were not harvested, withered and died. 2,000 square meters of crops and peanuts also had reduced productivity, the income was only enough to buy seeds and fertilizer. She and her husband had to go to the forest to cut firewood to sell for rice, while many families in the village gave up rice cultivation to work as construction workers and porters. Not only Ha Tinh, the General Department of Natural Disaster Prevention and Control reported that the whole country suffered 2,500 billion VND in damage due to drought and saltwater intrusion.
Heat waves not only reduce agricultural output, but also "melt" human productivity. Every year, heat waves cause the world to "evaporate" 677 billion working hours, equivalent to 2,100 billion USD, according to a 2022 study by Durham University (USA). The most affected industries are agriculture and construction.
Vietnam does not have data on outdoor workers. However, according to the General Statistics Office in 2021, Vietnam has 18.5 million workers in the agriculture, forestry, fishery and construction sectors. This is the group most at risk of being affected by heat.
Damage will increase as temperatures continue to rise over the next 80 years, possibly 7-10 times higher than the 1998-2005 period, according to the 2020 climate change scenario of the Ministry of Natural Resources and Environment.
Temperature forecast from now to 2099
According to Dr. Nguyen Ngoc Huy, a climate change expert, urban residents and low-income people will be the groups most affected by extreme heat. City dwellers are increasingly dependent on cooling technologies such as air conditioning. This becomes a "comfort box" for humans, but at the same time pushes the temperature into a vicious cycle of resonance and upward translation. As a result, the weather is becoming more and more extreme.
Those without access to air conditioning are the most vulnerable, forced to endure the combined heat of the city, with the resulting long-term health effects and illnesses. But in the long run, he said, everyone will be a victim.
"The heat is just the beginning. We put emissions into the atmosphere, what we get back is natural disasters," he warned.
Content: Thu Hang - Gia Chinh - Duc Hung - Viet Duc
Graphics: Hoang Khanh - Thanh Ha
About the data:
- El Nino years are counted by NOAA. For years with El Nino, La Nina, and neutral, the statistics choose the longer phase. For example, 2016 has all three phenomena of El Nino (January to April), neutral (May to July) and La Nina (August to December), it is considered a La Nina year. If the duration of all three phases in a year is equal, it is a neutral year.
- The country currently has 150 meteorological stations, VnExpress selected 12 meteorological stations to evaluate weather trends in 10 regions: Northwest North (Lai Chau); Viet Bac North (Phu Tho); Northeast North (Hai Phong); Northern Delta (Ha Dong station, Hanoi); North Central (Nghe An, Ha Tinh); Central Central (Da Nang); South Central (Nha Trang); Central Highlands (Pleiku); Southeast (Ho Chi Minh City, Vung Tau); Southwest (Can Tho).
- Data of 7 climate zones are taken from the 2021 National Climate Assessment Report of the Ministry of Natural Resources and Environment (updated to 2018).
- The article was written with the advice of the experts in the article and Mr. Le Dinh Quyet (Southern Hydrometeorological Station); National Hydrometeorological Center.
- Temperature forecast data for the period 2016-2035 is taken from the Climate Change and Sea Level Rise Scenario of the Ministry of Natural Resources and Environment in 2016; the period from 2045 to 2099 is taken from the 2020 updated version of this scenario.
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