Changes in surface climate of the tropical Pacific

Solomon Islands Government

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

Our climate will be changing for foreseeable future

Main climate features of the region

Pacific atmospheric circulation

• Trade winds

• Convergence zones

• Walker and Hadley circulations

Sea surface temperature

El Niño-Southern Oscillation (ENSO)

• Major source of year-to-year climate variations

Typical El Niño and La Niña rainfall patterns

Wetter (green) or drier (orange)

Typical El Niño and La Niña rainfall

Annual rainfall – Honiara

Typical El Niño and La Niña temperature

Annual temperature – Honiara

Effects of El Niño and La Niña on SST

Warmer (red) or cooler (blue)

ENSO shifts SPCZ and tropical cyclones

El Niño

La Niña• Further north El Niño • Further south La Niña

• Fewer cyclones further east El Niño• More cyclones further west La Niña

Cyclones in Solomon Islands

Number of cyclones passing within 400 km of Honiara

Projected changes in climate

Global annual mean energy budget W m-2

Redistributing sun’s energy = climate system

• Without the atmosphere the Earth would be ~30oC cooler

• More greenhouse gases trap more energy in climate system

Trenberth et al 2009

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 = 280ppmair bubbles in ice cores

2011= 391ppmMauna Loa

Observed warming of global temperatures

Projecting future climatesEmissions Scenario

IPCC-AR4 (2007)

Temperature (oC) Rainfall

2035 2050 2100 2035 2050 2100

Low (B1)450-500 ppm CO2

0.5-1.0 ? 1.0-1.5 5-15% 10-20% 10-20%

High (A2)750-800 ppm CO2

0.5-1.0 1.0-1.5 2.5-3.0 5-20% 10-20% 10-20%

• Predicting future forcing – how much more greenhouse

gases?

• Range of possible futures but the future will be WARMER

Spatial variation in warming

Spatial variation in rainfall

Preparing for TC Jasmine Vanuatu

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

Extremes

• Extremes will become more extreme

• Unclear how ENSO will change – continued influence

Important points to note

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

Summary