New findings help sharpen global warming projections
A chemical analysis of cave formations in Indonesia has helped climate researchers identify a large-scale pattern of El Niño shifts in the Pacific Ocean that may play a role in how climate change plays out over the next few decades.
Measuring isotopes in the stalagmites, and comparing it with records from East Asia and the central-eastern equatorial Pacific, enabled the researchers to pinpoint century-scale patterns in Pacific rainfall and temperature, and link them with global climate changes in the past 2000 years.
A long phase in the Pacific dominated by El Niño-like conditions (between 950 and 1250) corresponded with hemisphere warming and droughts, which switched to a La Niña-like pattern during a cold period between 1350 and 1900.
The new data will help scientists build more accurate models of future climate, said member of the research team, Alena Kimbrough, from The Australian National University.
“Our work is a significant piece in the grand puzzle. The tropics are a complicated, yet incredibly important region to global climate and it’s been great to untangle what’s happening,” said Kimbrough, a PhD student at the ANU Research School of Earth Sciences. “The current models struggle to reflect century-scale changes in the El Niño Southern Oscillation (ENSO). “We’ve shown ENSO is an important part of the climate system that has influenced global temperatures and rainfall over the past millennium
The El Niño Southern Oscillation (ENSO) is an irregular variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean.
The new work found periods of predominantly El Niño-like patterns for several hundred years that alternate with La Niña patterns, impacting on global climate over the last 2000 years.
“Until we can model this lower-frequency behavior in the tropical Pacific, one can only speculate on how the warming will play out over the next few decades,” said lead author Dr Michael Griffiths from William Paterson University, in the United States.
The international team of scientists was led by Dr Michael Griffiths of William Patterson University in New Jersey, along with PhD candidate Alena Kimbrough and Dr Michael Gagan at the ANU, Professor Wahyoe Hantoro of the Indonesian Institute of Sciences and colleagues at the University of Melbourne and the University of Arizona.