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Changes in surface climate of the tropical Pacific

Changes in surface climate of the tropical Pacific. Based on……. Outline and key messages. Main features of region’s climate system Human influence on the climate system - climate is already changing Future will be warmer Extreme weather likely to be more extreme

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Changes in surface climate of the tropical Pacific

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  1. Changes in surface climate of the tropical Pacific

  2. Based on…….

  3. Outline and key messages • Main features of region’s climate system • Human influence on the climate system - climate is already changing • Future will be warmer • Extreme weather likely to be more extreme Our climate will be changing for foreseeable future

  4. Main climate features of the region

  5. Pacific atmospheric circulation • Trade winds • Convergence zones • Walker and Hadley circulations

  6. El Niño-Southern Oscillation (ENSO) • Major source of year-to-year climate variations

  7. Sea surface temperature & ENSO

  8. Effects of El Niño and La Niña on SST Warmer (red) or cooler (blue)

  9. Typical El Niño and La Niña rainfall patterns Wetter (green) or drier (orange)

  10. Typical El Niño and La Niña rainfall Annual rainfall – Port Vila

  11. Typical El Niño and La Niña temperature Annual temperature – Port Vila

  12. ENSO shifts SPCZ and tropical cyclones El Niño • Further north El Niño • Further southLa Niña La Niña • Fewer cyclones further east El Niño • More cyclones further west La Niña

  13. Cyclones in Vanuatu Number of cyclones passing within 400 km of Port Vila

  14. Tropical Cyclones Vanuatu projections indicate there is likely to be a decrease in the number of tropical cyclones by the end of the 21st century. But there is likely to be an increase in the average maximum wind speed of cyclones by between 2% and 11% and an increase in rainfall intensity of about 20% within 100 km of the cyclone centre.

  15. Unclear how ENSO will change in CC context – continued influence CLOUD NASARA Animation Project, Launch in June/July 2013!

  16. Projected changes in Vanuatu’s climate

  17. Redistributing sun’s energy = climate system • Without the atmosphere the Earth would be ~30oC cooler • More greenhouse gases trap more energy in climate system

  18. Why are climate scientists so sure climate is changing due to human activities? • Theory • Modelling • Evidence: • instrumental measurements • changes in the physical world • changes in the biological world • paleoclimate archives The climate system appears to be changing faster than earlier thought likely Steffen 2009

  19. Measured increase in carbon dioxide 18th century = 280ppm air bubbles in ice cores 2011= 391ppm Mauna Loa

  20. Observed warming of global temperatures

  21. Projecting future climates • Predicting future forcing – how much more greenhouse gases? • Range of possible futures but the future will be WARMER

  22. Spatial variation in warming

  23. Spatial variation in rainfall

  24. Vanuatu’s Rainfall projections • Wet season rainfall is projected to increase (moderate confidence) • Dry season rainfall is projected to decrease (moderate confidence) • Annual mean rainfall is projected to increase (low confidence) • Rainfall over Vanuatu is strongly influenced by ENSO

  25. Extremes The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be Trenberth 2012 Preparing for TC Jasmine Vanuatu

  26. WhitegrassDeclining Cool Days and Increasing Warm Days

  27. Extremes of Vanuatu Temperature & Rainfall • The intensity and frequency of days of extreme heat are projected to increase (very high confidence) • Increase in the number of hot days and warm nights and a decline in cooler weather. • The intensity and frequency of days of extreme rainfall are projected to increase (high confidence) • Little change is projected in the incidence of drought (low confidence)

  28. Important points to note • ENSO and climate variability are KEY PART of Vanuatu’s Climate System • Human influence on the climate system already being measured in Vanuatu • Future will be warmer • Extreme weather likely to be more extreme • Not just a ‘new climate’ to which we can adapt……. • For foreseeable future, climate will be CHANGING Our climate will be changing for foreseeable future

  29. For More Information.... Vanuatu Meteorology & Geo-hazards Department Tel: 24686

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