Changes in surface climate of the tropical pacific
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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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Outline and key messages
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



Pacific atmospheric circulation

  • Trade winds

  • Convergence zones

  • Walker and Hadley circulations



El Niño-Southern Oscillation (ENSO)

  • Major source year-to-year climate variations


Typical El Niño and La Niña rainfall anomalies

Wetter (green) or drier (orange)




Effects of El Niño and La Niña on SST

Warmer (red) or cooler (blue)


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




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


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


Measured increase in carbon dioxide to human activities?

18th century = 280ppm

air bubbles in ice cores

2011= 391ppm

Mauna Loa



Projecting future climates to human activities?

  • Predicting future forcing – how much more greenhouse gases?

  • Range of possible futures but the future will be WARMER


Spatial variation in warming to human activities?


Spatial variation in rainfall to human activities?


Extremes to human activities?

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


Important points to note to human activities?

  • Extremes will become more extreme

  • Unclear how ENSO will change – continued influence


Summary to human activities?

  • Not just a ‘new climate’ to which we can adapt…….

  • For foreseeable future, climate will be CHANGING


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