PROJECTIONS FOR VIETNAM

Transcription

1 HIGH-RESOLUTION CLIMATE PROJECTIONS FOR VIETNAM REGIONAL NORTH EAST

2 KEY FINDINGS CURRENT TRENDS PROJECTED TRENDS THROUGHOUT THE 21 ST Annual temperature observations showed a significant trend of about.11 to.25 C increase per decade, while annual rainfall observations showed decreases. Annual temperature is projected to increase by about 1.5 to 6.1 C by end-of-century. Little change in annual rainfall amounts is projected, although seasonal changes are apparent. Small increases in the number and duration of heatwaves are projected. The number of hot days in low lying areas of this region is projected to increase. Extreme rainfall amounts are projected to increase in the northern and decrease in the southern parts of this region. Droughts are projected to increase in the eastern and decrease in the western parts of this region. The length of the southwest monsoon is projected to remain unchanged, but its intensity is projected to decrease by end-of-century. Projections indicate that the number of tropical cyclones may decrease. Other studies have also suggested some increases in intensity. Sea levels are projected to rise by about 1 to 4mm by mid-century, with further increase by end-of-century and beyond. ABOUT THIS PUBLICATION This Regional Summary has been developed as part of the High-resolution Climate Projections for Vietnam project funded by Australia s Agency for International Development (AusAID) in order to provide information and data for updating the official climate change and sea-level rise scenarios for Vietnam in 215. This brochure provides a summary of the key findings from this research for the North East region. For a summary of findings for all of Vietnam see the Project Summary Report and for more detailed information on the scientific approach and results see the Technical Report (available in 214). All publications and climate projection information can be accessed on the project website:

3 CURRENT CLIMATE CLIMATE FEATURES 1 Annual average temperature: 18 to 23 C Maximum temperature: 38 to 41 C Minimum temperature: -2 to 2 C Annual average rainfall: 14 to 2mm Daily maximum rainfall: 15 to 5mm Rainfall season: May to Sep FIGURE 1. MAP OF VIETNAM WITH NORTH EAST REGION HIGHLIGHTED. The station trend analyses (below) are based upon all available data within the last 5 years ( ). ANNUAL TEMPERATURE HAS INCREASED Annual temperature in this region has increased significantly by approximately.11 to.25 C per decade (Figure 2). The highest increasing rate of.25 C per decade is observed at the TamDao station (south). It should be noted that trends less than.1 C per decade are not significant 2. HOANG SA ISLANDS MINIMUM TEMPERATURE HAS INCREASED MORE THAN THE MAXIMUM TEMPERATURE While minimum daily temperature has significantly increased by up to approximately.26 C per decade, the trend in maximum daily temperature was slightly smaller, with increases of approximately.21 C per decade. MORE HOT DAYS AND FEWER COLD NIGHTS The number of hot days 3 significantly increased by up to 6 days per decade, while the number of cold nights 4 has significantly decreased at almost all stations by up to 5 days per decade. ANNUAL RAINFALL HAS DECREASED PHU QUOC ISLAND CON DAO ISLAND TRUONG SA ISLANDS Observations of most inland stations showed a significant decreasing trend in annual rainfall (Figure 3). The largest station decrease is about 6% per decade at the Phu Ho station (south). Note that the trend at the Lang Son station (east) is not significant. EXTREME RAINFALL AMOUNTS HAVE DECREASED The annual maximum of 1-day rainfall amounts and the number of very wet days remain unchanged for almost all stations in this region, while the annual maximum of 5-day rainfall amounts has decreased significantly. 1 Nguyễn Đức Ngữ, Nguyễn Trọng Hiệu (24). Khí hậu và tài nguyên khí hậu, NXB Nông nghiệp. Hà Nội. 2 Statistical significance has been calculated using the Mann-Kendall test. 3 Hot days with temperatures above 35 C. 4 Cold nights with temperatures below 15 C. NORTH EAST 1

4 FIGURE 2: ANNUAL TEMPERATURE TRENDS BASED ON STATION OBSERVATIONS. TEMPERATURE CHANGES ARE INDICATED FOR EACH STATION IN C PER DECADE. RED CIRCLES REPRESENT AN INCREASING TREND AND BLUE CIRCLES, DECREASING. CIRCLES ARE FILLED WHERE THERE ARE STATISTICALLY SIGNIFICANT TRENDS 2. ELEVATION IS INDICATED BY THE COLOUR BAR TO THE RIGHT AND LIGHT BLUE LINES REPRESENT MAJOR RIVERS. 23N HAGIANG.16 22N 21N BACQUANG.23.2 SAPA THAINGUYEN TUYENQUANG YENBAI PHUHO TAMDAO LANGSON.6 BAICHAY.19 COTO.11 m E 15E 16E 17E 18E FIGURE 3: ANNUAL RAINFALL TRENDS BASED ON STATION OBSERVATIONS. RAINFALL CHANGES ARE INDICATED FOR EACH STATION IN PERCENT CHANGE PER DECADE. RED CIRCLES REPRESENT A DECREASING TREND AND BLUE CIRCLES, INCREASING. CIRCLES ARE FILLED WHERE THERE ARE STATISTICALLY SIGNIFICANT TRENDS 2. ELEVATION IS INDICATED BY THE COLOUR BAR TO THE RIGHT AND LIGHT BLUE LINES REPRESENT MAJOR RIVERS. 23N HAGIANG.88 22N 21N BACQUANG SAPA THAINGUYEN TUYENQUANG YENBAI PHUHO TAMDAO LANGSON 1.35 BAICHAY 2.35 COTO 1.6 m E 15E 16E 17E 18E 2 HIGH-RESOLUTION CLIMATE PROJECTIONS FOR VIETNAM

5 FUTURE CLIMATE Regional and global models 5 are used to project changes in rainfall and temperature by mid-century ( ) and end-of-century (28 299) relative to the baseline period (198 2). TEMPERATURE INCREASES Projections from regional models for average temperature changes by mid-century and end-of-century are presented in Table 1. The warming is very clear, with an increase in annual temperature of about 1.3 to 3.4 C by mid-century and 2.5 to 6.1 C by end-of-century under the higher (RCP8.5) greenhouse gas scenario. The largest warming is projected in the SWMS 6 (Jun Sep) and the SIMS 6 (Oct Nov). Less warming is evident in the lower greenhouse gas scenario (). TABLE 1: OF TEMPERATURE CHANGES (IN C) ANNUALLY AND BY SEASON 6 FROM REGIONAL MODELS FOR THE LOWER () AND HIGHER (RCP8.5) GREENHOUSE GAS SCENARIOS BY MID- ( ) AND END-OF- (28 299). THE AMOUNT OF CHANGE AND THE LEVEL OF AGREEMENT AMONGST MODELS ARE INDICATED BY SHADING. LOWER GREENHOUSE GAS SCENARIO () HIGHER GREENHOUSE GAS SCENARIO (RCP8.5) LOWER GREENHOUSE GAS SCENARIO () HIGHER GREENHOUSE GAS SCENARIO (RCP8.5) ANNUAL CHANGES NEMS DEC MAR SEASONAL CHANGES FIMS APR MAY SWMS JUN SEP SIMS OCT NOV +.9 to to to to to to to to to to to to to to to to to to to to +6.8 Small increase Half or more projections show increases of less than 2 C Medium increase More than half of projections show increases of 2 to 4 C High increase Half or more projections show increases of greater than 4 C 5 These are global climate models from the Coupled Model Intercomparison Project Phase 5 that will be used in the Intergovernmental Panel on Climate Change s Fifth Assessment Report. 6 Given the influence of monsoons on Vietnam s climate, monsoon-based seasons have been used in these analyses: North East Monsoon Season (NEMS), First Inter-Monsoon Season (FIMS), South West Monsoon Season (SWMS) and Second Inter-Monsoon Season (SIMS). NORTH EAST 3

6 TEMPERATURE INCREASES Projections of changes over time by global models, and the range of changes by end-of-century for both global and regional models, are presented for temperature in Figure 4. Both global and regional models agree on large increases in temperature by end-of-century, with less warming in the lower () greenhouse gas scenario. However, projections by the regional models show slightly less warming in all seasons except for the SWMS (Jun Sep). The varying amounts of temperature increase signify the need to consider both mid-range and extreme changes. FIGURE 4. REGIONALLY AVERAGED SEASONAL TEMPERATURE CHANGES: SERIES GRAPH OF PROJECTIONS BY GLOBAL CLIMATE MODELS () SHOWN ON THE LEFT, FOR HIGHER (RCP8.5) GREENHOUSE GAS SCENARIO. END-OF- OF PROJECTIONS BY GLOBAL CLIMATE MODELS () AND REGIONAL CLIMATE MODELS () SHOWN AS BARS, ON THE RIGHT, FOR BOTH LOWER () AND HIGHER (RCP8.5) SCENARIOS. FIRST INTER-MONSOON SEASON (APR MAY) 32 6 TEMPERATURE ( C) CHANGE IN TEMPERATURE ( C) COMPARED TO HISTORIC BASELINE PERIOD (198 2) SOUTH WEST MONSOON SEASON (JUN SEP) 34 6 TEMPERATURE ( C) CHANGE IN TEMPERATURE ( C) COMPARED TO HISTORIC BASELINE PERIOD (198 2) HIGH-RESOLUTION CLIMATE PROJECTIONS FOR VIETNAM

7 LEGEND: 1. Middle (bold) line is the mid-point value (median) of or simulations from multiple models over a 2-year average. 2. Shaded area is between the upper and lower ranges (9th and 1th percentiles) of or simulations from multiple models over a 2-year average. This represents the potential range of projections in any given 2-year period. SECOND INTER-MONSOON SEASON (OCT NOV) 28 6 TEMPERATURE ( C) CHANGE IN TEMPERATURE ( C) COMPARED TO HISTORIC BASELINE PERIOD (198 2) NORTH EAST MONSOON SEASON (DEC MAR) 24 6 TEMPERATURE ( C) CHANGE IN TEMPERATURE ( C) COMPARED TO HISTORIC BASELINE PERIOD (198 2) NORTH EAST 5

8 SOME SEASONAL DECREASES IN RAINFALL Similar to temperature, projections of seasonal rainfall changes over time by global models, and the range of changes by end-of-century for both global and regional models, are presented in Figure 5. These projections for rainfall show larger variations in the direction of change than were projected for temperature. This reinforces the need to consider both mid-range and extreme changes. FIGURE 5. REGIONALLY AVERAGED SEASONAL RAINFALL CHANGES: SERIES GRAPH OF PROJECTIONS BY GLOBAL CLIMATE MODELS () SHOWN ON THE LEFT, FOR HIGHER (RCP8.5) GREENHOUSE GAS SCENARIO. END-OF- OF PROJECTIONS BY GLOBAL CLIMATE MODELS () AND REGIONAL CLIMATE MODELS () SHOWN AS BARS, ON THE RIGHT, FOR BOTH LOWER () AND HIGHER (RCP8.5) SCENARIOS. FIRST INTER-MONSOON SEASON (APR MAY) 25 8 RAINFALL (MM/MONTH) % CHANGE IN RAINFALL COMPARED TO HISTORIC BASELINE PERIOD (198 2) SOUTH WEST MONSOON SEASON (JUN SEP) 45 8 RAINFALL (MM/MONTH) % CHANGE IN RAINFALL COMPARED TO HISTORIC BASELINE PERIOD (198 2) HIGH-RESOLUTION CLIMATE PROJECTIONS FOR VIETNAM

9 LEGEND: 1. Middle (bold) line is the mid-point value (median) of or simulations from multiple models over a 2-year average. 2. Shaded area is between the upper and lower ranges (9th and 1th percentiles) of or simulations from multiple models over a 2-year average. This represents the potential range of projections in any given 2-year period. SECOND INTER-MONSOON SEASON (OCT NOV) 14 8 RAINFALL (MM/MONTH) % CHANGE IN RAINFALL COMPARED TO HISTORIC BASELINE PERIOD (198 2) NORTH EAST MONSOON SEASON (DEC MAR) 8 RAINFALL (MM/MONTH) % CHANGE IN RAINFALL COMPARED TO HISTORIC BASELINE PERIOD (198 2) NORTH EAST 7

10 SOME SEASONAL DECREASES IN RAINFALL Projections from regional models for annual rainfall (Table 2) show large variations in both direction and amount of change. However, there is medium agreement on decreases projected for the SIMS 6 (Oct Nov) by mid-century and for the SWMS (Jun Sep) by end-of-century. TABLE 2: OF RAINFALL CHANGES (IN %) ANNUALLY AND BY SEASON 6 FROM REGIONAL MODELS FOR THE LOWER () AND HIGHER (RCP8.5) GREENHOUSE GAS SCENARIOS BY MID- ( ) AND END-OF- (28 299). THE LEVEL OF AGREEMENT IN CHANGE AMONGST MODELS IS INDICATED BY SHADING. LOWER GREENHOUSE GAS SCENARIO () HIGHER GREENHOUSE GAS SCENARIO (RCP8.5) LOWER GREENHOUSE GAS SCENARIO () HIGHER GREENHOUSE GAS SCENARIO (RCP8.5) ANNUAL CHANGES NEMS DEC MAR SEASONAL CHANGES FIMS APR MAY SWMS JUN SEP SIMS OCT NOV -14 to to to to to to to to to to to to to to to to to to to to +94 High agreement on decrease All projections show decrease Medium agreement on decrease More than half of the projections show decrease less than -1% Low agreement on change Projections do not agree or show little change Medium agreement on increase More than half of the projections show increase greater than +1% High agreement on increase All projections show increase 8 HIGH-RESOLUTION CLIMATE PROJECTIONS FOR VIETNAM

11 CLIMATE EXTREMES Projected changes throughout the 21 st century for a number of key climate extremes that affect this region are summarised below: SLIGHT INCREASES IN HEATWAVES The number and length of heatwaves (consecutive periods with hot conditions) are projected to increase slightly by end-of-century. INCREASE IN HOT DAYS IN SOME PARTS The number of hot days (days with maximum temperatures above 35 C) is projected to increase in the lower lying areas of this region. Since temperature decreases with height, increases in hot days are not projected to reach the mountainous areas of this region, even by end-of-century. MORE INTENSE EXTREME RAINFALL IN THE NORTH AND LESS INTENSE IN THE SOUTH Due to their rarity, changes in extreme rainfall events (annual maxima of 1-day and 5-day rainfall amounts) are not easy to project and are often associated with a large degree of uncertainty. Nevertheless, some projections by regional models show a tendency towards more intense extreme rainfall in northern parts and less intense extreme rainfall in southern parts of this region. DROUGHTS TO INCREASE IN EAST AND DECREASE IN WEST Some projections by regional models show that short-term droughts (3-month consecutive periods with a rainfall deficit) are expected to occur more often in eastern parts and less often in western parts of this region. On the other hand, long-term droughts (12-months) are projected to occur more often and last longer in most parts of this region. SOUTHWEST MONSOON REMAIN UNCHANGED Based upon some projections by regional models, the length and intensity of the southwest monsoon are expected to remain unchanged by mid-century, with slight decreases in both evident by end-of-century. FEWER BUT POSSIBLY MORE INTENSE TROPICAL CYCLONES (TYPHOONS) Preliminary analysis of projections by regional models in this study suggests that the number of tropical cyclones may decrease in the East Vietnam Sea by mid-century. Other studies support this decreasing trend and suggest increases in intensity by end-of-century. SEA LEVELS WILL CONTINUE TO RISE The new projections indicate that the rate of sea-level rise during this century will be larger than the last. Sea levels rise approximately 1 to 4mm by mid-century with further increase by end-of-century and beyond. In addition, ground subsidence can occur in regions where there is ground water extraction or possible loss of sediment supply as rivers become more managed (i.e. more dams). These effects may be contributing to the substantially larger rates of relative sea-level rise at some locations.

12 CONTACT VIETNAM INSTITUTE OF METEOROLOGY, HYDROLOGY AND ENVIRONMENT WEB Assoc. Prof. Dr. Nguyen Van Thang PHONE For more information, please visit the project website: