Extending climate predictability beyond El Nino

April 21, 2015, University of Hawaii at Manoa
Inter-basin coupling as a cause of multi-year tropical Pacific climate predictability: Impact of Atlantic warming on global atmospheric Walker Circulation (arrows). Rising air over the Atlantic subsides over the equatorial Pacific, causing central Pacific sea surface cooling, which in turn reinforces the large-scale wind anomalies. Credit: Yoshimitsu Chikamoto

Tropical Pacific climate variations and their global weather impacts may be predicted much further in advance than previously thought, according to research by an international team of climate scientists from the USA, Australia, and Japan. The source of this predictability lies in the tight interactions between the ocean and the atmosphere and among the Atlantic, the Pacific and the Indian Oceans. Such long-term tropical climate forecasts are useful to the public and policy makers.

At present computer simulations can predict the occurrence of an El Niño event at best three seasons in advance. Climate modeling centers worldwide generate and disseminate these forecasts on an operational basis. Scientists have assumed that the skill and reliability of such tropical climate forecasts drop rapidly for lead times longer than one year.

The new findings of predictable up to three years in advance are based on a series of hindcast computer modeling experiments, which included observed ocean temperature and salinity data. The results are presented in the April 21, 2015, online issue of Nature Communications.

"We found that, even three to four years after starting the prediction, the model was still tracking the observations well," says Yoshimitsu Chikamoto at the University of Hawaii at Manoa International Pacific Research Center and lead author of the study. "This implies that central Pacific climate conditions can be predicted over several years ahead."

"The mechanism is simple," states co-author Shang-Ping Xie from the University of California San Diego. "Warmer water in the Atlantic heats up the atmosphere. Rising air and increased precipitation drive a large cell, which then sinks over the Central Pacific. The relatively dry air feeds surface winds back into the Atlantic and the Indian Ocean. These winds cool the Central Pacific leading to conditions, which are similar to a La Niña Modoki event. The central Pacific cooling then strengthens the global atmospheric circulation anomalies."

"Our results present a paradigm shift," explains co-author Axel Timmermann, climate scientist and professor at the University of Hawaii. "Whereas the Pacific was previously considered the main driver of variability and the Atlantic and Indian Ocean its slaves, our results document a much more active role for the Atlantic Ocean in determining conditions in the other two ocean basins. The coupling between the oceans is established by a massive reorganization of the atmospheric circulation."

The impacts of the findings are wide-ranging. "Central Pacific temperature changes have a remote effect on rainfall in California and Australia. Seeing the Atlantic as an important contributor to these rainfall shifts, which happen as far away as Australia, came to us as a great surprise. It highlights the fact that on multi-year timescales we have to view climate variability in a global perspective, rather than through a basin-wide lens," says Jing-Jia Luo, co-author of the study and climate scientist at the Bureau of Meteorology in Australia.

"Our study fills the gap between the well-established seasonal predictions and internationally ongoing decadal forecasting efforts. We anticipate that the main results will soon be corroborated by other computer models," concludes co-author Masahide Kimoto from the University of Tokyo, Japan.

Explore further: Atlantic warming turbocharges Pacific trade winds

More information: Chikamoto, Y., A. Timmermann, J.-J. Luo, T. Mochizuki, M. Kimoto, M. Watanabe, M. Ishii, S.-P. Xie, and F.-F. Jin: Skilful multi-year predictions of tropical trans-basin climate variability. Nature Communications, 6:6869, DOI: 10.1038/ncomms7869 (2015).

Related Stories

Atlantic warming turbocharges Pacific trade winds

August 3, 2014

New research has found rapid warming of the Atlantic Ocean, likely caused by global warming, has turbocharged Pacific Equatorial trade winds. Currently the winds are at a level never before seen on observed records, which ...

Wind bursts strongly affect El Nino severity

April 15, 2015

The long-forecasted El Niño event of 2014/15 did not meet expectations. On March 5, 2015, the National Weather Service finally declared a "weak" event arriving several months later than expected, formally dashing predictions ...

Climate change may draw gray whale back to Atlantic

March 11, 2015

The effects of global warming are proving so severe that the gray whale, famous for its annual migrations along the Pacific Coast, could find its way back to the Atlantic Ocean, according to a new study co-authored by scientists ...

Volcanic eruptions durably impact North Atlantic climate

March 30, 2015

Particles emitted during major volcanic eruptions cool the atmosphere due to a 'parasol' effect that reflects sunlight. The direct impact of these particles in the atmosphere is fairly short, lasting two to three years. However, ...

Recommended for you

Weather anomalies accelerate the melting of sea ice

January 16, 2018

In the winter of 2015/16, something happened that had never before been seen on this scale: at the end of December, temperatures rose above zero degrees Celsius for several days in parts of the Arctic. Temperatures of up ...

Jet stream changes since 1960s linked to more extreme weather

January 12, 2018

Increased fluctuations in the path of the North Atlantic jet stream since the 1960s coincide with more extreme weather events in Europe such as heat waves, droughts, wildfires and flooding, reports a University of Arizona-led ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.