Changes in surface climate of
the tropical Pacific
Based on Chapter 2
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
Main climate features of the region
Pacific atmospheric circulation
• Trade winds
• Convergence zones
• Nauru sensitive to SPCZ position
• Walker and Hadley circulations
El Niño-Southern Oscillation (ENSO)
• Major source year-year climate variations
Typical El Niño and La Niña rainfall anomalies
Wetter (green) or drier (orange)
Typical El Niño and La Niña rainfall
Typical El Niño and La Niña SST anomalies
Warmer (red) or cooler (blue)
Sea surface temperature
Projected changes in climate
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
18th century = 280ppm
air bubbles in ice cores
2011= 391ppm
Mauna Loa
Observed warming of global temperatures
Projecting future climates
Emisions Scenario
Temperature (oC)
Rainfall
IPCC-AR4
2100
(2007)
2035
2050
2100
2035
2050
2100
Low (B1)
0.5-1.0
?
1.0-1.5 5-15% 10-20% 10-20%
450-500 ppm CO2
High (A2)
0.5-1.0 1.0-1.5 2.5-3.0 5-20% 10-20% 10-20%
750-800 ppm CO2
• Predicting future forcing – how much more
greenhouse gases?
• Range of possible futures but he future will be
WARMER
Spatial variation in warming
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
Important points to note
• Extremes will become more extreme
• Unclear how ENSO will change – continued
influence
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