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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 We are affecting 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 • We are affecting 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. Sea surface temperature

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

  8. Typical El Niño and La Niña rainfall anomalies Wetter (green) or drier (orange)

  9. Typical El Niño and La Niña rainfall Annual rainfall - Apia

  10. Temperature

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

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

  13. Cyclones

  14. Projected changes in climate

  15. Redistributing sun’s energy = climate system Global annual mean energy budget W m-2 Trenberth et al 2009 • Without the atmosphere the Earth would be ~30oC cooler • More greenhouse gases trap more energy in climate system

  16. 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

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

  18. Observed warming of global temperatures

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

  20. Spatial variation in warming

  21. Spatial variation in rainfall

  22. 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

  23. Important points to note • Extremes will become more extreme • Unclear how ENSO will change – continued influence

  24. Summary • Not just a ‘new climate’ to which we can adapt……. • For foreseeable future, climate will be CHANGING

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