Extreme weather includes unexpected, unusual or unseasonal weather, weather at the extremes of the historical distribution. Often, extreme phenomena are based on a location‟s recorded weather history and defined as lying in the most unusual percent. In recent years some extreme weather phenomena have been attributed to the humaninduced global warming with a number of studies indicating an increase of natural, social and economic threats from extreme weather. This paper attempts to overview some extreme weather phenomena in Vietnam over recent years, present their social and economic impacts, and to recommend policy implications.
AN OVERVIEW OF SOME EXTREME WEATHER PHENOMENA AND SOCIO AND ECONOMIC IMPACTS IN VIET NAM Prof.Dr Tran Tho Dat1, Assoc Prof.Dr Dinh Duc Truong1, Dr Nguyen Dang Quang 2, Dr Doan Quang Tri 2, MA Huynh Thi Mai Dung1 National Economics University, Hanoi Vietnam Vietnam Meteorological and Hydrological Administration Abstract Extreme weather includes unexpected, unusual or unseasonal weather, weather at the extremes of the historical distribution Often, extreme phenomena are based on a location‟s recorded weather history and defined as lying in the most unusual percent In recent years some extreme weather phenomena have been attributed to the humaninduced global warming with a number of studies indicating an increase of natural, social and economic threats from extreme weather This paper attempts to overview some extreme weather phenomena in Vietnam over recent years, present their social and economic impacts, and to recommend policy implications Keywords: Extreme weather, climate change, natural disaster damages, social and economic impacts Introduction Vietnam is one of the most severely affected countries by natural disasters and extreme weather in the Asia-Pacific region due to its geographical location and topography In recent years, under the impact of climate change, extreme natural disasters have occurred more frequently, causing human losses and significant impacts on the economy According to IMHEN and UNDP (2015), from 1990 to 2010, 74 floods occurred in the river systems of Vietnam, severe droughts, salinity intrusion, landslides and other natural disasters have also been hindering the development of Vietnam In the past 20 years, Vietnam has suffered more than 800 natural disasters (an average 40 disasters/year) with increasing intensity and frequency causing great damages to economic, social and ecological dimensions, especially during 2005-2015 (WMO) Currently, Vietnam suffers annual losses of 1.4-1.8% of GDP annually due to natural disasters phenomena The economic consequences are not only in the short term but also in the medium and longterm including reduced economic growth, employment, income, investment and trade This paper tries to overview some extreme weather phenomena in Vietnam over recent years and their social and economic impacts, then some policy implications will be drawn Theoretical framework In theory, a climate variable is considered to be a random variable with a value changing within a certain limit This limit may be blocked or not blocked, on one side or both A weather variable is called extreme if its value domain centers on one side of the possible set of weather variables being considered For example, the temperature in the air 679 (at some point in time) is an atmospheric variable Its value range can range from the smallest a0 to b0 Every day has a minimum value (minimum daily temperature) and a highest value (maximum daily temperature) The set of all minimum (maximum) daily temperature values is considered to be the set of possible values of a random quantity called the minimum (maximum) factors (or extreme climatic factors) Then, the minimum temperature will be in the range or range from a0 to a1, while the maximum temperature will vary from b1 to b0, with a0 ≤ a1 and b1 ≤b0 Let X is a particular climatic variable with the distribution function F(x), or the probability density function F(x) Then, the set of x values of X satisfying the following condition is called the extreme set of values for X, or extreme climate: { { | } (1) or | } (2) with =∫ P = P(X< )=F( P = P(X )=1-F( (3) or =∫ (4) That is, the probability of occurrence of events X< or X =p When studying extreme elements and climatic phenomena, people often pay attention to its extreme values and call it extremist climatic extremes Extreme climatic factors are defined as the values of extreme weather variables with a probability of occurring less than or equal to 10% However, each locality or region has different application For example, one can reduce the probability of appearing to 5% or even 1%, or increasing p to 15%, 20%, or even to 25% or 30% In many cases, for simplicity, instead of using the notion of probability, one can use the concept of percentile The extreme climatic variables considered are usually the maximum or minimum climate variables If it is a minimum climate, the values smaller than the q centimeter (for 100 centigrade) are considered extreme, and for the extreme climatic factors, values greater than q is considered extreme The qth subdivision of the random variable X is the x value of X that satisfies the condition: [ ] In other words, the solution of f (x) = q% For the minimum climate, q (%) = p (%) and for the maximum climate variables q (%) = - p (%) In order to avoid confusion, attention should be paid to distinguishing the concept of the radical with the absolute concept of the absolute term of many years which is often referred to as the record of values An overview on some extreme weather phenomena in Vietnam There have been accelerated developments in weather and extreme natural hazards due to climate change recently The intensity, time span and place of occurrence of these phenomena are no longer stick to conventional climate patterns The catastrophic floods 680 have been recorded in the North, heat waves and severe droughts have been seen in the Central region, especially in the South, where traditionally known as temperate climate, have been suffering the lack of fresh water and serious saline intrusion In this paper, we try to synthesize and analyze the evolution of dangerous meteorological phenomena, namely heat wave, drought, substantial rain and typhoon a Heat wave In the past 40 years, the average national temperature in each decade has increased at a rate of 0.26 ± 0.100C, which has been two times higher than the pace of global temperature rise in the same timescale (Nguyen Dang Quang et al 2013) According to the research, the increase in winter temperature was greater than that in summer temperature, and the average temperature increase in the South was greater than that in the North (Fig 1) In the South, while the lowest temperature at night (Tmin) in the winter has increased significantly than the maximum temperature in the daytime (Tmax), in several places in the South and islands, the opposite is true As a result, fierce heat waves have been increasingly observed in the North and this phenomenon has been verified through measured data Phan Van Tam et al (2010) demonstrated that the number of hot days tended to increase at a national level from 1961 to 2007, and these figures even increased more (approximately 10%) between 1991 and 2007 at stations in the North East, the Northern Delta and the North Central Coast, in which the North Central Coast was the area having a majority of hot days (Fig 2) The hot days on average of this area fluctuated from about 40 to 60 days per year, of which the highest number of hot days was 90 (Nam Dong station) and the lowest one was 20 (Thanh Hoa station) Apart from two coastal stations (Nha Trang, Phan Thiet), the number of hot days in South Central was similar to that in North Central Coast 681 Fig.1 Standard deviation of average temperature over the climate zones of Viet Nam from 1971 to 2010 N1 - N4, S1 - S3: the northern and southern climate The bold lines showed standard deviations of temperature on June, July, August, December, January and February; the light lines illustrated standard deviations of temperature on May, June, July, November, December and January; dotted lines represented standard deviations of temperature on August, September, October, January, February and March (Nguyen Dang Quang et al., 2013) 100 80 Số ngày nắng nóng B4 60 40 N1 B1 B2 B3 N2 N3 Điện Biên Lai Châu Sơn La Bắc Quang Hà Giang Lạng Sơn Thái Ngun n Bái Hòa Bình Láng Nam Định Ninh Bình Phủ Liễn Đơng Hà Đồng Hới Hà Tĩnh Hồi Xn Huế Nam Đơng Thanh Hóa Tương Dương Vinh Ba Tơ Đà Nẵng Nha Trang Phan Giang Phan Thiết Quy Nhơn Trà My Tuy Hòa Ayunpa Buôn Ma Đắc Nông Kon Tum Cà Mau Cần Thơ Rạch Giá 20 Fig Annual sunshine days in some typical stations in climate zones (Phan Van Tan, 2010) The records of extreme heat are being broken easily in several places in Vietnam In other words, the time span between two recorded heat waves is shortened and the next extreme heat is higher than that in the previous year In 2010, in two consecutive months, June and July 2010, the highest temperature of the heat wave in Northern Delta and North Central generally fluctuated from 400C to 410C The highest temperature recorded at Con Cuong station (Nghe An province) was 42,20C (compared to the previous record was 420C in 1980) In 2015, during the long-lasting heat wave on May, June and July 2015 in the same places, the recorded temperature in 2010 at Con Cuong station was broken, and the new record was 42.70C The highest temperatures during the heat wave of 2015 were commonly varied from 400C to 420C, and new records were updated simultaneously b Drought Drought is one of the most common natural disasters in Viet Nam Drought and water shortage have been occurred with greater frequency and intensity (Nguyen Van Thang et al., 2013) The severe droughts have taken place more often, with high frequency was mainly from January to April (winter rice crop) and from May to August (summer rice crop) Droughts in winter mainly occurred in the North, the South and Central Highlands; droughts in summer mainly occurred in North Central and South Central (Fig 3) 682 Fig The frequency of seasonal drought (three consecutive months) in some typical areas (Phan Van Tan, 2010) At the national level, areas that suffered drought the least were mainly in the North East and areas suffered the longest span were concentrated in the South Central Coast (drought might last from January till August and September) In term of fluctuations, the figures for droughts in the North West were the lowest, while those of North Central and South Central were the highest The frequency of occurrence of drought monthly and seasonally slightly differed According to the statistics, water shortage in Central provinces and Central Highlands have been increasingly severe in the dry seasons recently Some typical prolonged droughts took place in 2010, the water flow in the rivers and streams nationally was greatly lower than the average ones in several years; the water shortage was 60% to 90% in some places, water levels in many places in Central Vietnam were the lowest with the rare occurrence of 40 - 100 years/time In 2005, the lowest water level in the record was seen on major rivers over the country In the North, new records of lowest water level were updated in some major stations in Lo River, the downstream of Hong River in Ha Noi, and the downstream of Thai Binh River (Pha Lai) Similarly, the lowest water level of the data also is observed in the Central and the South, Ma River in Ly Nhan, DakBla River in KonTum, Cai Nha Trang River in Dong Trang, and Cuu Long River 683 c Heavy rain Rainy season starts in April and May and lasts until October and November, particularly the rainy season in South Central roughly ends in November and December On average, there are about 25 showers of heavy rains across the country, the first heavy rains of the year usually occur in the North and the Central Highlands (in March and April), and later in other areas in the country In the coastal zones, heavy rain moves from the North to the South over time and usually reaches a peak in months of the fall Different from the relatively uniformly change patterns of temperature, heat and drought, the increase and decrease of rain in climatic regions in the past decades have random properties, lowering the statistical reliability (Nguyen Dang Quang et al 2013) While many studies show an increase in the rainfall in the South in the last four or five decades (Endo et al, 2009; Phan Van Tan et al, 2010; Nguyen Dang Quang et al, 2013), the trend in the North was different More specifically, some researches show that the rainfall in the North decreases uniformly (Endo et al, 2009; Phan Van Tan et al, 2010), whereas other research papers demonstrate an increase in the rainfall in some places at Northern Delta and North East (Nguyen et al, 2013) Furthermore, the research by Nguyen et al (2013) demonstrated a decrease in the rainfall in Highlands, but the decrease is not proven statistical reliability The difference between these results can be attributed to using different approach and the length of statistics, locations and the number of observed stations More importantly, a general conclusion is brought about from among research on the trend of heavy rain in Viet Nam, there is a clear correlation between global warming reflected by sea surface temperature in the Eastern Pacific Ocean (the areas NINO 3.4) with changes in climatic conditions in Southern provinces of Vietnam Fig The value of slope a1 of heavy rain data from 1961 to 2007 at typical stations (Phan Van Tan et al., 2010) Apart from research on the trend and development of rain, studies on heavy rain have also been conducted recently These studies show that extreme phenomena, historical values together with human and economic losses are likely to increase (IPCC, 2013) The 684 observed data confirm that the number, intensity, and location of heavy rains are unusually high For example, in the first half of October 2010, there were two torrential rains causing devastating floods in the history from Nghe An to Quang Binh provinces The total volume of the rainfall within 10 days fluctuated from 700mm-to 1600mm, accounting for 50%70%, even 80%-90% the annual precipitation There were pouring rains in some places (for example, the rainfall in Tuyen Hoa on October 3rd was 470mm and that in Ba Don on October 5th was 540mm), and lasted for a long time with the highest intensity during over past 60 years Consecutive floods triggered serious inundation in days, several places were flooded to 4m-6m, causing damage to people, property and traffic and irrigation constructions The unusual torrential rains were not only in the rainy season but also took place in the dry season, particularly, the rain in March 2015 (March 24-27, 2015) in Thua Thien Hue - Quang Ngai with the average rainfall of 300-450 mm, and records of rainfall were set in several places Among recent heavy rains, it is important to study the heavy rains in the North at the end of July and beginning of August 2015 The records of intensity were in narrowed areas, mainly occurred in some communes of Quang Ninh province Heavy rains mainly took place in Cua Ong, Ha Long, Co To (Quang Ninh), while nearby locations were Hon Dau and Bach Long Vi (Hai Phong), the intensity of heavy rains was lower The precipitation of Quang Ninh province generally fluctuated from 1000-1300mm, especially the figure for Cua Ong was approximately 1600mm; Bai Chay station registered the highest precipitation in 1960‘s data at 387mmm (28/7/2015) The probability of this rare occurrence is estimated to be approximately 500 years d Typhoons and tropical depressions Meteorological extremes such as typhoons, tropical low pressure, cold spell, and winter freeze have also recorded new historical points Firstly, unusual developments of typhoons and tropical low pressure should be taken into consideration - these phenomena are regarded as deadliest natural disasters in Vietnam On March 2012, the No.1 typhoon (Pakhar typhoon) affected the Northern provinces in Vietnam In fact, early typhoons that take place in March are rare (the last time this phenomenon was recorded was 31 years ago), and Pakhar typhoon was the sole phenomenon that still reached the typhoon level when it landed in Viet Nam during the past 61 years In the same time, the No.8 typhoon (Son Tinh typhoon) did not follow climatic patterns when it landed in Thai Binh and Hai Phong provinces in last October with magnitude of 11-12 and the highest ones varied from 14-15 After that, the typhoon changed direction, moving in the Northeast along the coast of Hai Phong-Quang Ninh and eventually weakened into a low-pressure zone This typhoon has caused strong winds and heavy rains in the Eastern provinces of North and North Central, seriously damaging people and properties Hurricanes with magnitude of 14-15 seem to appear more in the South China Sea, such as typhoon No.6 (Megi typhoon in 2010 and Haiyan typhoon in 2013,…) 2017 was affirmed as the year with the greatest number of typhoons and tropical depressions in the past 50 years in the East Sea, including 20 typhoons and tropical depressions These figures outnumbered that in 2013, in which 685 there were five typhoons and two tropical depressions landed in Viet Nam On the sea, the huge waves recorded occurred during the North East monsoon and typhoons On November, 2013 Haiyan typhoon caused waves which were 10 meters higher in the area between the South China Sea and the Central Coast of Viet Nam The recorded wave was 4.5 meter at Bach Long Vi Island which occurred in the North East monsoon in January 2016 Social and economic impacts of extreme weather in Vietnam In Vietnam, the vulnerability of the natural and social system depends very much on the degree of danger of extreme weather, density, adaptability of exposed entities and some natural factors such as geology, geomorphology, terrain, hydrology, etc In general, since 1989 the number of deaths (social harm) and total economic loss (economic damage) due to natural disasters in Vietnam is complex, but overall there is a tendency to increase along with GDP growth Over the last 30 years, natural disasters have killed and lost about 500 people, injured thousands, lost about 1.5% of GDP annually (Tran Tho Dat and Vu Thi Hoai Thu, 2012) Only in five years from 2002-2006, natural disasters caused about 1,700 people died, property damage estimated at VND 75,000 billion The total value of losses caused by natural disasters in 2013 is estimated at nearly VND 30,000 billion (twice more than that in 2012), 313 deaths and 1150 injuries (GSO, 2013) Fig Economic losses and death caused by disaster 1999-2013 (SREX report Vietnam, 2015) Regarding damage by disaster types, Vietnam suffered most from tropical cyclones, floods, followed by droughts and landslides During 13 years (1990-2012), tropical cyclones caused losses of nearly $ 4.7 billion, floods costing nearly $ 3.7 billion while droughts and landslides caused losses of 649 and 2.3 $ millions, respectively The indirect damage of floods is partly attributable to heavy rainfall during and after storms, as rainfall in storms can account for up to 25% of total annual precipitation in some coastal stations of Central Vietnam 686 Fig Economic losses caused by types of disasters in Vietnam (EM-DAT The international disaster databases, 2015) Climate extremes cause different losses to sectors of the socio-economic system The impact of climate change (expressed as a percentage of GDP from high to low) for each sector (for 2010/2030) is as follows: Labor productivity is 4.4%/8,6%; aquatic products: 0.5% /1.6%; agriculture: 0.2%/0.4%; biodiversity: 0.1%/0.1%; The extreme weather (in 2010/2030) includes sea level rise of 1.5%/2.7%, hot and cold weather of 0.1%/0.3%; floods and landslides of 0.1%/0.1% (DARA, 2012) Fig.7 Loss (million VND) of some main sectors due to disasters form 1989-2009 (SREX Report Vietnam, 2015) Total losses due to natural disasters are highest for industries that are heavily dependent on weather, climate, and terrain, land, such as agriculture, fisheries, irrigation and transportation If the sea level rises by m without coping activities, most of the Mekong Delta will be submerged for long periods of time, and property damage is estimated at $ 17 billion 687 By the end of the 21st century, if the sea level rises by m, 6.3% of Vietnam's area, about 39% of the Mekong Delta, over 10% of the Red River Delta and Quang Ninh, over 2.5% of the area Central and over 20% of Ho Chi Minh City area are at risk of flooding (MONRE, 2012).The area of agricultural land and aquaculture is most inundated (10,962 km2) when sea level rises by 76%, respectively, followed by wetland with 1,895 km2 and 13%, forest and natural vegetation with 1,159 km2 and 8%, and residential areas with 302 km2 and 2% Coastal industrial zones of the Mekong River Delta, the Red River Delta and the North Central Coast are the most vulnerable due to sea level rise of m (The sea level rise of m directly affects 16% of the population of the country, nearly 55% of the population in the Mekong Delta provinces; over 9% of population in Red River Delta and Quang Ninh; near the 9% of the population in the central coastal provinces and about 7% of the population in Ho Chi Minh City At the same time, over 4% of the railway system, over 9% of national highways and about 12% of Vietnam's provincial roads will be affected The highest level of sea level rise is in the Mekong Delta and the Red River Delta According to UNDP (2012), among the developing countries, Vietnam is one of the countries most vulnerable to sea level rise The impact of sea level rise on 84 coastal developing countries by the six indicators of land use, population, GDP, urban size, agricultural land size, and swampy area shows that Vietnam is one of the five countries most affected by the 1m high sea level rise (Dasgupta et al., 2009) Moreover, the World Bank ranked Vietnam as one of 12 World Bank borrowers most affected by sea level rise due to climate change The impact of radicals on the community is also reflected in the decline in livelihoods Nearly half a million Vietnamese have a primary income from fishing and other two million people with incomes associated with fishery The livelihoods of these people depend on climatic factors and natural resources, so life is particularly uncertain and at risk from natural disasters as well as weather patterns Provinces in the Mekong Delta and Central Coast are economically vulnerable as the majority of their income is related to fishing However, if adaptating appropriately to extreme climate, Vietnam can reduce the negative impact of hazards and vulnerabilities Flooding in the Mekong Delta is a phenomenon that occurs annually, bringing many benefits to people in the region such as supplying fishery resources, sedimentation for the Delta, increasing agricultural production for the production season, wash away the toxic substances accumulated in the lowlands and reduce the vulnerability caused by flooding here Residents adjust to living with floods, production activities and activities change in the direction of adaptation, taking advantage of opportunities caused by floods, thereby reducing exposure to hazards, vulnerability to flooding Conclusion and recommendations Climate change is occurring and having broad impacts across the world Climate change projections draw a grim picture of Vietnam‘s climate vulnerability in the coming decades A transformation of different sectors-including agriculture, water resource 688 management, energy, fisheries, forestry, and infrastructure is needed to counter climate threats and enhance Vietnam‘s adaptive capacity To improve disaster preparedness and build longerterm resilience, Vietnam should act now to adapt to changing climate As in many countries, Vietnam‘s risk and vulnerability are intensified by unplanned urban development, inappropriate land use, and ecosystem degradation Yet it is still possible for the country to correct course if its policy makers and communities take right and appropriate actions A holistic and integrated approach that includes both structural and nonstructural measures is proposed to address impacts of extreme weather and to promote longer-term resilience measures across key sectors Tackling the impacts of all types of disaster risks nationally will require well thought-out strategic planning and coordinated implementation of medium- and long-term measures from a multi-hazard perspective Such planning must be backed by sound local knowledge, scientific understanding (for targeting and prioritizing investments for technology development and adoption), infrastructure creation, and capacity building To effectively address the extreme weather, an integrated approach using both structural and nonstructural interventions (policies, capacity building, information, technologies, infrastructure, and services) is needed References IMHEN UNDP (2015) Báo cáo Ďặc biệt Việt Nam quản lý rủi ro thiên tai tượng cực Ďoan nhằm th c Ďẩy thích ứng với biến Ďổi khí hậu, NXB Tài ngun-Mơi trường Bản Ďồ Việt Nam, 451 trang IPCC (2013) Summary for policymakers In: Climate Change 2013: The Physical Science Basis Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T F., D Qin, G -K Platter, M Tignor, S K Allen, J Boschung, A Nauels, Y Xia, V Bex and P M Midgley (eds)] Cambridge University Press, Cambridge, Unided Kingdom and New York, NY, USA, 1535 pp, doi: 10.1017/CB09781107415324 Nguyen, D.Q., Renwick, J and McGregor, J (2014) Variation of surface temperature and rainfall in Viet Nam from 1971 to 2010, Int J Climatol., 34, 249-264, DOI: 10.1002/joc.3684 Phan Văn Tân, (2010) Nghiên cứu tác Ďộng biến Ďổi khí hậu toàn cầu Ďến yếu tố tượng khí hậu cực Ďoan Việt Nam, khả dự báo giải pháp chiến lược ứng phó, Báo cáo tổng hợp kết khoa học công nghệ Đề tài, KC08.29/06-10, 598 trang UNDP and IMHEN (2015), Viet Nam special report on managing the risks of extreme events and disasters to advance climate change adaptation, Vietnam 689 ... 2016 Social and economic impacts of extreme weather in Vietnam In Vietnam, the vulnerability of the natural and social system depends very much on the degree of danger of extreme weather, density,... at the end of July and beginning of August 2015 The records of intensity were in narrowed areas, mainly occurred in some communes of Quang Ninh province Heavy rains mainly took place in Cua Ong,... River in KonTum, Cai Nha Trang River in Dong Trang, and Cuu Long River 683 c Heavy rain Rainy season starts in April and May and lasts until October and November, particularly the rainy season in