By examining tree rings, lake sediment and coral, University of Hawaii scientists and colleagues have found that the El Niño weather phenomenon and its counterpart, La Niña, appear to be increasing in strength and frequency with the rise of global temperatures.

The study, conducted by a team of scientists from the UH International Pacific Research Center, National Oceanic and Atmospheric Administration and the University of New South Wales in Australia, also suggests that El Niño weather patterns were more active and intense from 1979 to 2009 than at any other time in the past 600 years.

Axel Timmermann, a UH professor and co-author of the study, said in a UH news release last week that the research represents "a significant step towards understanding where current ENSO activity sits in the context of the past."

ENSO stands for El Niño Southern Oscillation, the phenomenon’s formal name.

El Niño is characterized by sea temperatures that are higher than normal in the eastern tropical Pacific, conditions more favorable to storms, while La Niña features temperatures that are lower than normal. ENSO-neutral conditions currently prevail in the Central Pacific, which means the sea temperature is about average.

Shayne McGregor of Australia, the lead author of the report, said that the findings could pave the way for climate models to be able to more accurately estimate how El Niño activity will continue to evolve with climate change.

"Our research suggests in a warming world we are likely to see more extreme El Niño and La Niña events, which over the past decade in Australia have been related to extreme flooding, persistent droughts and dangerous fire seasons," he said.

The team used a newly defined method it developed to compare tree ring and lake sediment and coral core samples taken from various locations with computer models that are based on historical data to determine how El Niño events have changed across the Pacific.

"By applying these observations and finding which climate models represent past changes, we will have a better idea of which climate models are more likely to reproduce the ENSO response to climate change in the future," said professor Matt England of the Australian Research Council’s Centre of Excellence for Climate System Science.

McGregor noted, however, that scientists still don’t know exactly why ENSO cycles appear to be affected by rising global temperatures.

"Understanding this relationship will be vital to help us get a clear idea of the future changes to global climate," he said.

The research is published in the Oct. 10 issue of Climate of the Past, an international journal published by the European Geosciences Union.

On Friday, President Barack Obama launched the national Climate Preparedness and Resilience Task Force and appointed Gov. Neil Abercrombie to serve on it with 25 other elected officials from around the nation and Guam. Abercrombie said in a statement that he hopes his principal contribution will be highlighting and encouraging research into the role that the Pacific plays in worldwide climate change.