El Nino's slow arrival may be down to this distant weather phenomenon

In spite of conditions looking conducive to El Nino forming as far back as May, the Bureau of Meteorology confirmed in its latest El Nino Southern Oscillation update that the key drivers were not yet in place to declare a fully fledged El Nino event.

Climate specialists are planning to investigate a new lead that may be responsible for the unusual set of climate drivers, looking further afield and assessing whether climate change induced weather conditions in parts of the distant Atlantic Ocean are playing a role in stopping the Pacific Ocean El Nino forming.

Matthew England, Scientia Professor at the Centre for Marine Studies at the University of New South Wales, has researched complex interlinking weather patterns between the oceans and their impact on Australian conditions.

He said it was possible the Atlantic could be playing a role on weather here.

"Given what we know about Atlantic-Pacific teleconnections, it could well be that the current warm Atlantic anomalies are playing some role here, in terms of delaying and potentially suppressing the usual atmospheric response to warm east Pacific temperatures," Professor England said.

Warmer waters in the eastern Pacific normally lead to rising air in the Pacific near the coast of the Americas and sinking air near Australia, but as of recent measurements in July the opposite was true.

Andrea Taschetto, Associate Professor with the Climate Change Research Centre at UNSW, agreed the Atlantic influence could be playing a role in the Pacific.

"It is possible that the Atlantic may be influencing the way the Pacific is responding," Associate Professor Taschetto said.

"Normally we see the tropical North Atlantic warming after the peak of an El Nino.

"This time the North Atlantic has been warm before El Nino development."

Prof Taschetto said this set-up could be the key to the odd atmospheric conditions in the eastern Pacific.

"Given that the southern hemisphere has been warmer than the northern hemisphere, maybe the extra heat in the South Atlantic is what is driving the rising air there and descending air in the east north Pacific," she said.

"So, I agree with Matt, it is plausible, but extra analysis on the Walker circulation and trade winds is needed to check if this is what is really happening."

Ass Prof Taschetto said the temperature in the east Pacific was up three degrees, but said western Pacific temperatures were yet to cool.

"This east-west temperature difference is important because it drives changes in atmospheric pressure and a weakening of the trade winds, characteristic of El Nino events," she said.

Prof England's work last year looked at the role of the Atlantic overturning circulation, which has slowed in recent years.

He said it was possible this decline in the movement of tropical water into the north Atlantic may have the influence of creating more La Nina like conditions in the Pacific, which in Australia means wetter than average conditions.