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<\/div>During the 2022 La Ni\u00f1a season, wild storms lashed the Gold Coast in Australia<\/p>\n
zstock\/Shutterstock<\/p>\n<\/div>\n<\/figcaption><\/figure>\n<\/p>\n
An expected shift to cool La Ni\u00f1a conditions in the Pacific Ocean has been delayed again. Forecasters now project only a weak event to emerge by the end of November, which is likely to limit the cooling influence of the climate pattern on global average temperatures.<\/p>\n
\u201cI do not know why it has slowed down,\u201d says Michelle L\u2019Heureux<\/a> at the US National Oceanic and Atmospheric Administration (NOAA). \u201cIf someone did, we might have been able to predict it.\u201d<\/p>\n La Ni\u00f1a is the cool phase of the cycle of sea surface temperatures in the equatorial Pacific Ocean known as the El Ni\u00f1o Southern Oscillation (ENSO). The climate pattern is among the largest influences on the global climate, and irregularly swings between La Ni\u00f1as, neutral temperatures and warm El Ni\u00f1os every several years.<\/p>\n A rare \u201ctriple-dip\u201d La Ni\u00f1a<\/a> between 2020 and 2022 gave way to a strong El Ni\u00f1o in 2023. On top of warming due to greenhouse gas emissions, the release of stored heat in the oceans from that event boosted global average temperatures, making 2023 the hottest year on record<\/a>.<\/p>\n <\/p>\n As the El Ni\u00f1o faded and neutral temperatures emerged<\/a> in May of this year, forecasters projected a rapid shift to La Ni\u00f1a conditions would follow. In June, researchers at NOAA gave La Ni\u00f1a a greater than 60 per cent chance<\/a> of developing between July and September and a greater than 70 per cent chance of developing between August and October. This contributed to forecasts for an extreme Atlantic hurricane<\/a> season.<\/p>\n While sea surface temperatures in the Pacific have cooled since then, a full-blown La Ni\u00f1a still has not emerged, possibly contributing to a \u201csuspiciously quiet\u201d lull in hurricane activity<\/a>. NOAA now gives La Ni\u00f1a just a 60 per cent <\/a>chance of developing by the end of November. The agency projects a weak and short event lasting through January to March.<\/p>\n That bullish early forecasts were far off the mark is not hugely surprising, says Emily Becker<\/a> at the University of Miami in Florida. Forecasts made that early in the year tend to be less accurate because small fluctuations in wind or water can have big effects, she says. It is also not unheard of for La Ni\u00f1a to arrive so late, even following a strong El Ni\u00f1o event. Four La Ni\u00f1as have emerged <\/a>this late in the year since 1950.<\/p>\n But the reasons for the delay are unclear. \u201cThe trade winds have been slower than expected in parts of the eastern Pacific, which may be keeping waters on the equator warmer than forecasted,\u201d says L\u2019Heureux. \u201cBut this may be more of a symptom than a cause.\u201d<\/p>\n Whether human-caused climate change played a role in the delayed La Ni\u00f1a remains an open question, says Becker. Some research <\/a>suggests climate change will make ENSO more variable, but this remains a contentious area of climate science. \u201cThere have been studies published in the past five years or so saying practically everything,\u201d says Becker.<\/p>\n Despite the delays, a La Ni\u00f1a is slowly emerging, and it is likely that it will have its characteristic influence on global weather, from dry weather in the southern US to rain in Indonesia. But as a weak event, it won\u2019t cool global average temperatures as much as a strong and long-lasting one. \u201cWe have seen the global average temperature come down, but it\u2019s still very elevated,\u201d says Becker. \u201cWe probably won\u2019t see as much of a decrease.\u201d<\/p>\n Topics:<\/p>\n<\/section><\/div>\n