Lightning
New research suggests global warming could either lead to either drying significant increases in rainfall in the South Pacific.

Warming world creates uncertainty for Pacific rainfall

Alvin Stone
20 November 2012

Global warming has increased the uncertainty around future rainfall patterns over some of the most vulnerable nations in the South Pacific Islands, according to a new paper in Nature Climate Change.

The paper, Changes in South Pacific rainfall bands in a warming climate, has revealed two competing effects generated by global warming that could directly affect the future of a vital rainfall band, known as the South Pacific Convergence Zone, which brings important seasonal rain to the region.

As a result, the future rainfall patterns over islands in this region are now clouded in doubt.

The research was led by a team of scientists at the International Pacific Research Centre (IPRC) in collaboration with researchers from the Climate Change Research Centre (CCRC) and ARC Centre of Excellence in Climate System Science (CoECSS). 

“The South Pacific Convergence Zone is the main source of rainfall for many South Pacific Nations,” said one of the co-authors of the paper, Chief Investigator Prof Matt England.

 “This new research suggests we could see two completely opposite effects impact these islands that are directly linked to global warming. These effects could either lead to drying of this region or generate significant increases in rainfall.”

The cause of these apparently opposite effects is directly related to the warming world.

The first effect is caused by rising tropical temperatures, which introduce more water vapour into the atmosphere. This increases the size and distribution of heavy rainfall events around areas of converging winds – such as the South Pacific Convergence Zone.

The second effect is caused by the fact that the Equatorial region is likely to heat faster than the convergence region. This uneven heating can cause the rain band across the South Pacific Convergence Zone to move northwards, bringing more rain to Equatorial regions while taking it away from the current area under the convergence zone. 

Previously, climate models were notoriously poor in simulating this rainband, even under present day conditions. The researchers overcame this lack of clarity by adjusting their models to match the sea surface temperatures observed in the region.

With the resulting improvements in climate model performance from this approach, the researchers could then clearly identify the two competing mechanisms affecting rainfall trends in the Pacific and see how they responded to different rates of global warming.

“The key is how quickly the tropics warm compared to the region around the South Pacific Convergence Zone,” said Dr. Shayne McGregor, a co-author of the study.

“With moderate warming the altered temperature gradients between the tropics and South Pacific act to pull the rainband northwards, potentially drying the Southwest Pacific nations underlying the current convergence zone.

“But if we get much higher warming, which is possible by the end of the century, models suggest the increase in atmospheric water vapour will overcome the temperature gradient changes, leading to more rainfall in the South Pacific Convergence Zone.”

However, before scientists can make more definite projections of the delicate balance between the two climate change mechanisms, more extensive observations in the South Pacific are needed to determine how clouds and rainfall form and how they respond to climate phenomena such as El Niño along with improvements in the simulation of cloud formation physics in the models.

Source: ARC Centre of Excellence for Climate System Science web site

Latest news

Plastic bottle caps found in the ocean (source: NOAA PIFSC) Ocean debris leads the way for castaway fisherman
05 February 2014
The fisherman who washed up on the Marshall Islands last weekend was very lucky to have stranded on a remote beach there. The currents in the Pacific Ocean would have inevitably taken him into the great garbage patch of the North Pacific, where he could then have been floating for centuries to come.

Man in heat wave Get used to heat waves: extreme El Niņo events to double
20 January 2014
Extreme weather events fuelled by unusually strong El Niņos, such as the 1983 heatwave that led to the Ash Wednesday bushfires in Australia, are likely to double in number as our planet warms.

Ocean clouds Solution to cloud riddle reveals hotter future
20 December 2013
Global average temperatures will rise at least 4°C by 2100 and potentially more than 8°C by 2200 if carbon dioxide emissions are not reduced according to new research published in Nature that shows our climate is more sensitive to carbon dioxide than most previous estimates.

More news...

Copenhagen Diagnosis logo

The Copenhagen Diagnosis

On 25th November 2009 members of The Climate Change Research Centre, as part of a group of 26 international climate scientists, were part of a major international release of a new report synthesizing the latest climate research to emerge since the last IPCC Assessment Report of 2007.

Read more...

World map

There are no time-travelling climatologists: why we use climate models

In the absence of time-travelling climatologists, models are unrivalled tools for understanding our changing climate system. That is, climate models are scientific tools. We should recognise them as such and consider them with rigorous scientific, not political, scepticism.

Read more...

Antarctica

The Big Engine 2: oceans and weather

Federation Fellow and 2008 Eureka Prize winner, Professor Matthew England of CCRC, on the latest research into the role oceans play on weather.

Read more...

Smoke stack

The Science of Climate Change: Questions and Answers

Co-authored by Professor Steven Sherwood and Professor Matt England of CCRC, this Academy of Science report aims to summarise and clarify the current understanding of the science of climate change for non-specialist readers.

Read more...

Ocean weather

The Big Engine 1: oceans and weather

Federation Fellow and 2008 Eureka Prize winner, Professor Matthew England of CCRC, on the latest research into the role oceans play on weather.

Read more...

Tree rings

New insights into the climate of the past 2,000 years

A comprehensive new scientific study has revealed fresh insights into the climate of the past 2,000 years, providing further evidence that the 20th century warming was not a natural phenomenon. After 1900, increasing temperatures reversed a previous long-term cooling trend. This 20th Century warming has occurred simultaneously in all regions except Antarctica.

Read more...

Ocean

The dynamics of the global ocean circulation

The ocean is far from a stagnant body of water. Instead, it is constantly in motion, at speeds from a few centimetres per second to two metres per second in the most vigorous currents.

Read more...

Plastic rubbish

Leave the ocean garbage alone: we need to stop polluting first

Recent plans to clean plastics from the five massive ocean garbage patches could do more damage to the environment than leaving the plastic right where it is.

Read more...

Plastic rubbish

Charting the garbage patches of the sea

Just how much plastic is there floating around in our oceans? Dr Erik van Sebille from UNSW's Climate Change Research Centre has completed a study of ocean "garbage patches", and has found that in some regions the amount of plastic outweighs that of marine life.

Read more...

COECSS logo

UCC logo

Share | | RSS feed