El Niño: how the weather event is affecting global heating in 2023
Planet is being hit by double whammy of global heating and emerging El Nino The planet is being hit with a double whammy of global heating in 2023. On top of the inexorable rise in global temperature caused by greenhouse gas emissions is an emerging El Nino. This sporadic event is the biggest natural influence on year-to-year weather and adds a further spurt of warmth to an already overheating world. The result is supercharged extreme weather, hitting lives and livelihoods. The last major El Nino from 2014 to 2016 led to each of those years successively breaking the global temperature record and 2016 remains the hottest year ever recorded. However, El Nino has now begun and may already be driving new temperature records , with record heatwaves on land from Puerto Rico to China and record heatwaves in the seas around the UK . Variations in wind strength and ocean temperatures in the vast Pacific Ocean lead to two distinct climate patterns, El Nino and La Nina. The switch between them happens irregularly, every three to seven years, usually with neutral years in between. El Ninos tend to last about a year but the La Nina phase can be longer, and 2023 has brought the end of an unusual run of three successive La Nina years. Easterly winds normally push warm surface waters in the equatorial Pacific towards Australia and Indonesia and away from South America. As a result, warm water piles up in the west Pacific and cool water is drawn up from depth in the east Pacific. This is the neutral state. But at the onset of El Nino, the easterly winds weaken and the warm water spreads back across the whole Pacific. In contrast, at the onset of La Nina, the easterly winds are even stronger than normal, leading to further cooling of the east Pacific waters. The erratic timing of the switches between neutral, El Nino and La Nina conditions are the result of complex interactions between different climate system phenomena, from ocean current dynamics to thunderstorm cloud formation. The ocean absorbs more than 90% of the heat trapped by greenhouse gases released by fossil fuel burning and other human activities. The ocean is particularly effective at absorbing the heat during a La Nina event, when east Pacific temperatures are especially cold. However, during an El Nino, some of this heat is released to the atmosphere because warm water is spread right across the Pacific, smothering cooler waters. El Nino can add up to 0.2C to annual global surface temperatures. The El Nino-La Nina cycle switches the position of warm ocean waters and the damp, rain-laden air above it, meaning the cycle brings increased heatwaves, droughts, wildfires and floods to different regions. The places closest to the Pacific are most strongly affected. In Peru and Ecuador, El Nino brings heavy rains and flooding. The events full name El Nino de Navidad, or the Christ Child comes from the region and was coined because the biggest impacts occur at Christmas time. In the Amazon, the weather gets hotter and drier during an El Nino, meaning less growth and greater risk of fires in a forest already approaching a tipping point . Heat and drought also increase in Colombia and Central America. On the other side of the Pacific, Australia can be hit hard by the higher temperatures brought by El Nino . It raises the risk of heatwaves, drought, and bushfires in the east of the country and also increases the chances of mass coral bleaching of the Great Barrier Reef. The black summer of 2019-20 occurred during a small El Nino. Drought risk also increases in Indonesia and the last big El Nino from 2014-2016 fuelled huge forest fires , which sent a smoke plume halfway around the world. Countries further from the equator are still significantly affected by El Nino, which shifts the position of the high-altitude jet stream wind. As a result, the southern US gets wetter weather and increased flood risks, while the northern US and Canada get warmer and drier. The situation is similar In China, wetter in the south and hotter and drier in the north. Yes its impacts reverberate throughout the global climate system. Perhaps the biggest impact is a tendency for reduced rainfall in the Indian monsoon , which provides 70% of the countrys water and is vital for growing food in the worlds most populous nation. However, El Nino could bring increased rain to the drought-stricken Horn of Africa, where dry conditions brought by the three consecutive La Ninas exacerbated a long-term drought in parts of Ethiopia, Kenya and Somalia. El Nino also affects the risk of hurricanes and typhoons, usually suppressing those that affect the Caribbean and US , India and Bangladesh , and Japan and Korea. However, these storms are powered by ocean heat, and record-high sea temperatures in the Atlantic in 2023 have led the UK Met Office to forecast an above-average number of tropical storms in the North Atlantic. Europe is less affected, but in winter El Nino can shift the jet stream and bring more rain to the south of the continent and drier, colder conditions in the north . El Ninos impact on rainfall, temperature and plant growth also has knock-on effects, such as increased infectious disease including dengue fever in south-east Asia and Brazil. One study has even linked lower food production in El Nino years to civil wars . Weak El Nino conditions arrived in May and are expected to strengthen in the coming months, with an 84% chance of a moderate event at its peak from November to January, and a 56% chance of a strong event. Global average temperatures in early June were nearly 1C above levels previously recorded for the same month, leading to record heatwaves from Puerto Rico to Siberia to China . Some scientists said the heating suggested 2023 could become the hottest on record, although most of El Ninos heat will appear in 2024. Scientists are not sure. This is partly because there are not very many El Nino and La Nina events in the observational record, which goes back about 150 years. That makes it hard to be sure that trends in the data, which suggest a tendency towards more La Nina events, are not simply the result of chance. Furthermore, climate models do not agree on the question. This is because climate models have a relatively coarse resolution of 100km and cannot represent well either the ocean dynamics of the tropical Pacific or the thunderstorm clouds that drive large-scale circulation patterns. Prof Tim Palmer, at the University of Oxford, UK, hopes that a new generation of kilometre-scale global climate models , run on the latest exascale supercomputers, will provide more robust answers to this vitally important question. One thing is certain. Rising global temperatures, boosted in El Nino years and bringing worse extreme weather, will not end until carbon emissions are reduced to net zero .