1. Climate change projections for Vietnam from CMIP5 simulations Ramasamy Suppiah 29 November 2012

2. Climate Change in Vietnam | Suppiah Ramasamy 2 | Why we need this study? Vietnam’s long coastline, geographic location, and complex topography and monsoonal climates contribute to its being one of the most hazard-prone countries of southeast Asia, with storms and flooding, and drought in particular, responsible for economic and human losses. It is expected that anthropogenic climate change conditions can change the severity of climatic extremes in the future How good are the new generation of global climate models (GCMs) simulating the present climate over a broader region centered Vietnam? What are the projected changes in mean climate (temperature and rainfall) over Vietnam by the end of the century?

3. Data Climate Change in Vietnam | Suppiah Ramasamy 3 | Observed global surface air temperature, winds and mean sea level pressure data from ERA-Interim archives. The data set covers land and ocean areas Observed land only global rainfall from Climate Research Unit (CRU) and ERA-Interim archives for land and ocean areas. Observed gridded precipitation (Aphrodite) Simulated mean sea level pressure, surface air temperature and rainfall for historical and future climates for Representative Concentration Pathways (RCP) for RCP8.5 from Coupled Model Intercomparison Project phase 5 (CMIP5) simulations 15 Organisations and 31 simulations. Historical climate 1979-2004 and also 1979-2001 for CRU and future climate 2080-2099 for RPC8.5. Future temperature and rainfall changes for RCP8.5 are from 24 and 22 models, respectively.

4. Climate Change in Vietnam | Suppiah Ramasamy 4 | Methods and Seasons Statistical analyses: Pattern correlation and root mean square (RMS) errors Four Seasons: Northeast monsoon season: December to March (NEM) First Intermonsoon season: April and May (FIM) Southwest monsoon season: June to September (SWM) Second Intermonsoon season: October and November (SIM) Pattern correlation Perfect = 1.0, Worst -1.0 RMS Error small is good and high is worst

5. Climate Change in Vietnam | Suppiah Ramasamy 5 | Some thoughts about GCMs Simulation of the current climatology Capture the interannual and possibly intra-seasonal variability El Niño-Southern Oscillation Tropical cyclones Onset, retreat and duration of the monsoons Location of the Inter-tropical Convergence Zone (ITCZ) GCMs are the best available tool to simulate future climate

6. Comparison of CO 2 concentrations from SRES (A1B, A1FI, A2, B1) and RCPs (3.0, 4.5, 6.0, 8.5) approaches Climate Change in Vietnam | Suppiah Ramasamy 6 | Source: Meinshausen, M. and Coauthors, 2011 RCP 8.5 RCP 4.5

7. Winds at 850 hPa level for First Intermonsoon (FIM) and Southwest monsoon (SWM) seasons Presentation title | Presenter name 7 | FIM (April-May)SWM (June-September) Winds ms -1 Latitude Longitude

8. Winds at 850 hPa level for Second Intermonsoon (SIM) and Northeast monsoon (NEM) seasons Presentation title | Presenter name 8 | SIM (October-November)NEM (December-March) Winds ms -1 Latitude Longitude

9. Mean sea level pressure for First Intermonsoon (FIM) and Southwest monsoon (SWM) seasons Presentation title | Presenter name 9 | FIM (April-May)SWM (June-September) (hPa) Latitude

10. Mean sea level pressure for Second Intermonsoon (SIM) and Northeast monsoon (NEM) seasons Presentation title | Presenter name 10 | SIM (October-November)NEM (December-March) (hPa) Latitude

11. Mean rainfall during First Intermonsoon (FIM) and Southwest (SWM) monsoon seasons Climate Change in Vietnam | Suppiah Ramasamy 11 | FIM (April-May)SWM (June-September) mm/day Latitude

12. Mean rainfall during Second Intermonsoon (SIM) and Northeast (NEM) monsoon seasons Climate Change in Vietnam | Suppiah Ramasamy 12 | SIM (October-November) NEM (December-March) mm/day Latitude

13. Climate Change in Vietnam | Suppiah Ramasamy 13 | Pattern correlation and RMS Error for surface air temperature for four seasons based on the larger region Surface air temperature for Region (90-140°E,0-40°N) Best Worst

14. Climate Change in Vietnam | Suppiah Ramasamy 14 | Pattern correlation and RMS Error for surface air temperature for four seasons based on the larger region Surface air temperature for Region (60-160°E,-15-50°N) Best Worst

15. Climate Change in Vietnam | Suppiah Ramasamy 15 | Pattern correlation and RMS Error for mean sea level pressure for four seasons based on the larger region Mean sea level pressure for Region (90-140°E,0-40°N) Best Worst

16. Climate Change in Vietnam | Suppiah Ramasamy 16 | Pattern correlation and RMS Error for mean sea level pressure for four seasons based on a relatively smaller region Mean sea level pressure for Region (95-135°E,0-25°N) Best Worst

17. Climate Change in Vietnam | Suppiah Ramasamy 17 | Pattern correlation and RMS Error for rainfall for four seasons. Results against ERA-Interim data for the larger region Rainfall for Region (90-140°E,0-40°N) Land and ocean areas Best Worst

18. Climate Change in Vietnam | Suppiah Ramasamy 18 | Pattern correlation and RMS Error for rainfall for four seasons. Results against ERA-Interim data for the Asian region Rainfall for Region (60-160°E,-15-50°N) Land and ocean areas Best Worst

19. Climate Change in Vietnam | Suppiah Ramasamy 19 | Pattern correlation and RMS Error for rainfall for four seasons. Results against CRU data based on the larger region Rainfall for Region (90-140°E,0-40°N) Land area only Best Worst

20. Climate Change in Vietnam | Suppiah Ramasamy 20 | A comparison of annual results from both ERA-Interim and CRU data ERA-Interim (Land and ocean) CRU Data (Land only) Best Worst

21. Climate Change in Vietnam | Suppiah Ramasamy 21 | Observed and simulated annual surface air temperature over the region Temperature (°C)

22. Climate Change in Vietnam | Suppiah Ramasamy 22 | Annual Temperature bias: Model-Obs Temperature (°C)

23. Climate Change in Vietnam | Suppiah Ramasamy 23 | Mean seasonal and annual temperature bias from 24 simulations Temperature °C

24. Climate Change in Vietnam | Suppiah Ramasamy 24 | Future annual surface air temperature changes by 8 of 24 models by the end of the century Temperature (°C)

25. Climate Change in Vietnam | Suppiah Ramasamy 25 | Future annual surface air temperature changes by 8 of 24 models by the end of the century Temperature (°C)

26. Climate Change in Vietnam | Suppiah Ramasamy 26 | Future annual surface air temperature changes by 8 of 24 models by the end of the century Temperature (°C)

27. Temperature change by the end of the century (°C) for RPC 8.5 from 24 models Climate Change in Vietnam | Suppiah Ramasamy 27 | First Intermonsoon Northeast monsoonSecond Intermonsoon Southwest monsoon Annual Temperature change (°C) Mean and ranges of future temperature changes ( °C) over Vietnam Season Low Mid High NEM 1.6 3.7 5.8 FIM 2.1 4.1 5.6 SWM 2.2 3.8 5.2 SIM 1.9 3.7 5.1 ANNUAL 2.1 3.8 5.1

28. Climate Change in Vietnam | Suppiah Ramasamy 28 | Observed and simulated annual rainfall over the region Rainfall (mm/day)

29. Climate Change in Vietnam | Suppiah Ramasamy 29 | Annual rainfall bias: Model-Observation Rainfall (mm/day)

30. Climate Change in Vietnam | Suppiah Ramasamy 30 | Mean model rainfall bias between simulations and observations: Model minus observations Rainfall bias (mm/day) First Intermonsoon Northeast monsoonSecond Intermonsoon Southwest monsoon Annual

31. Number of models agreeing on future rainfall increase from 22 GCMs Climate Change in Vietnam | Suppiah Ramasamy 31 | Increase First Intermonsoon Northeast monsoonSecond Intermonsoon Southwest monsoon Annual

32. Rainfall change by the end of the century (%) for RPC 8.5 from 22 models Climate Change in Vietnam | Suppiah Ramasamy 32 | Rainfall change (%) Mean and ranges of future rainfall changes (%) Over Vietnam Season Low Mid High NEM -40 +04 +70 FIM -50 -04 +45 SWM -14 +07 +25 SIM -08 +20 +65 ANNUAL -08 +07 +20 First Intermonsoon Northeast monsoon Second Intermonsoon Southwest monsoonAnnual

33. Climate Change in Vietnam | Suppiah Ramasamy 33 | Conclusions CMIP5 models fairly well capture the spatial patterns of seasonal and annual surface air temperature. However, there are large model-model variations. Most of the models tend to underestimate observed air temperature over the land areas. Current GCMs capture the observed spatial patterns and seasonality of rainfall. More rainfall over low latitudes and less rainfall over mid and high latitudes. Models tend to overestimate rainfall over low and high latitudes and underestimate over mid latitudes. However, there are small differences in regional scale.

34. Conclusions Cont. Climate Change in Vietnam | Suppiah Ramasamy 34 | Models suggest an increase of annual temperature between 2.0 and 5.0 with the mid value of 4.0°C over Vietnam by the end of this century for RPC 8.5 Rainfall changes are more complex as decreases and increases are simulated by models for future Annual average rainfall changes between -08 and +20% with a mid value of +07%. However, there are differences among the seasons. The largest mean rainfall increase is simulated for Second Intermonsoon season (+20%) and a small decrease is for First intermonsoon season (-04%). Most of the models agree on rainfall increases during, Northeast, Southwest and Second Intermonsoon seasons and decreases during the first intermonsoon season over Vietnam by the end of this century for RCP 8.5.

35. Future plan Climate Change in Vietnam | Suppiah Ramasamy 35 | Investigate temperature and rainfall changes for RCP4.5 and RCP8.5 with additional model experiments. Investigate the effects of aerosol on temperature and rainfall changes over Southeast Asia by the end of this century.

36. Suppiah Ramasamy CSIRO Marine and Atmospheric Research, Aspendale, Vic. 3195 t+61 3 9239 4554 esuppiah.ramasamy@csiro.au Thank you