ANALYSIS: ROUGHLY a year ago, scientists poring over temperature readings of the Pacific from satellites and a depleted array of ocean buoys were so sure an El Nino was on the way, the debate was mostly how strong it would be.
The event, though, failed to materialise largely because the winds failed to reverse their normal course and blow to the east. Without the reinforcement, the relative warmth of the eastern Pacific compared with the west broke up, and an El Nino did not occur.
That false start is one reason authorities have been 'gun shy' this time around, said Cai Wenju, a CSIRO climate modeller who has published widely on El Ninos and their counterparts, La Ninas.
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"Last year, we were over-confident. This year, we will be under-confident," Dr Cai told Fairfax Media during a visit to Hawaii, where the current conditions are being discussed.
In fact, El Nino-like conditions persisted throughout the past year. The US National Oceanic and Atmospheric Administration (NOAA), which has a lower threshold of temperature anomalies than the Bureau of Meteorology for gauging such events, stated in March that "the long-anticipated El Nino has finally arrived".
Usually conditions in the Pacific reset in the southern autumn, creating a so-called predictability barrier that makes it harder to tell what's coming later in the year.
This year, though, the signals are particularly strong, with El Nino conditions intensifying.
A strong El Nino doesn't necessarily mean temperatures and rainfall deficiencies in Australia will be worse than in a more moderate event.
But a powerful one – such as in 1997 – tends to have a bigger impact on worldwide temperatures given the driving role played in the global climate by the Pacific.
The temperature spike in the following year created such a high record that it fostered debate in years since that global warming may have slowed since temperature readings have only inched above 1988 – in 2005, 2010 and 2014 – even as greenhouse gas emissions continued to climb.
While the link between climate change and El Nino is an area of active research – including by Dr Cai who has projected a doubling of the frequency of severe El Ninos and La Ninos this century – another El Nino-fuelled leap in global temperatures this year or next may quell some of the debate about a "hiatus" in warming.
Here's NOAA's ranking of warmest years: