South Pacific countries will experience more severe and extreme weather events as a consequence of increasing greenhouse gas emissions, according to a research paper published in the journal Nature.

 

The international study, led by the CSIRO’s oceanographer Dr Wenju Cai, found that the increase in emissions will lead to large changes to the South Pacific rain band, the largest of its kind in the Southern Hemisphere.

 

The study found that changes to the band as a result of climate change will double the frequency of extreme weather evens in the band.

 

Dr Wenju and colleagues turned to the extensive archives of general circulation models submitted for the fourth and fifth IPCC Assessments and found that increases in greenhouse gases are projected to enhance equatorial Pacific warming.  In turn, and in spite of disagreement about the future of El Niño events, this warming leads to the increased frequency of extreme excursions of the rain band.

 

During moderate El Niño events with warming in the equatorial eastern Pacific, the rain band moves north-eastward by 300 kilometres.  Countries located within the bands’ normal position such as Vanuatu, Samoa, and the southern Cook Islands experience forest fires and droughts as well as increased frequency of tropical cyclones, whereas countries to which the rain band moves experience extreme floods.

 

“During extreme El Niño events, such as 1982/83 and 1997/98, the band moved northward by up to 1000 kilometres. The shift brings more severe extremes, including cyclones to regions such as French Polynesia that are not accustomed to such events,” said Dr Cai, a scientist at the Wealth from Oceans Flagship. 

 

A central issue for community adaptation in Australia and across the Pacific is understanding how the warming atmosphere and oceans will influence the intensity and frequency of extreme events. The impact associated with the observed extreme excursions includes massive droughts, severe food shortage, and coral reef mortality through thermally-induced coral bleaching across the South Pacific.

 

“Understanding changes in the frequency of these events as the climate changes proceed is therefore of broad scientific and socio-economic interest."