1. Changes in surface climate of the tropical Pacific

2. Based on Chapter 2

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
Nauru sensitive to SPCZ position
Walker and Hadley circulations

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

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

8. Typical El Niño and La Niña rainfall

9. Typical El Niño and La Niña SST anomalies
Warmer (red) or cooler (blue)

10. Sea surface temperature

11. Projected changes in climate

12. 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

13. 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

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

15. Observed warming of global temperatures

16. Projecting future climates
Emisions Scenario
IPCC-AR4
(2007)
Temperature (oC)
2100
Rainfall
2035
2050
Low (B1)
ppm CO2 ?
5-15%
10-20%
High (A2)
ppm CO2
5-20%
Predicting future forcing – how much more greenhouse gases?
Range of possible futures but he future will be WARMER

17. Spatial variation in warming

18. Preparing for TC Jasmine Vanuatu
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

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

20. For foreseeable future, climate will be CHANGING
Summary
Future for Nauru will be warmer and wetter
Not just a “new climate” to which we can adapt
For foreseeable future, climate will be CHANGING