In 2016, the world experienced the hottest year on record, with average global temperatures nearly exceeding 1°C above pre-industrial levels. The World Health Organization estimated that over 60 million people were affected by drought, heatwaves, and extreme precipitation events that year, leading to devastating food insecurity, outbreaks of vector-borne diseases, and lack of fresh water. The weather phenomena which contributed to this increase in temperature and its associated effects were not meteorological anomalies. Rather, they were part of a larger climate pattern called El Niño-Southern Oscillation (ENSO).
ENSO describes the complex cycle of fluctuations in air pressure, sea surface temperature, and winds over the equatorial Pacific Ocean. More commonly known, however, are the opposing phases of the oscillation: El Niño and La Niña. As the warm phase of ENSO, El Niño events in particular tend to make international headlines for the destructive aftermath left in their wake. As opposed to La Niña cycles, El Niño is associated with unrelenting heat, arid conditions, and excess flooding across different regions of the world.
The phases of ENSO alternate every two to seven years in a relatively unpredictable manner, with individual events generally lasting between one and three years. Since 2020, a prolonged but weak La Niña has taken effect in the Pacific Ocean. Yet, scientists with the United States National Oceanic and Atmospheric Administration (NOAA) tentatively predict this phase is coming to an end. Instead, NOAA forecasts show a likely shift to a neutral phase come springtime and the formation of a full-blown El Niño event by late 2023. With an intensified El Niño coupled with current effects of anthropogenic climate change, scientists warn of an unprecedented increase in global temperatures. Over the next two years, warming will likely surpass 1.5°C, a critical climate threshold established by the Paris Agreement in 2015. More than ever before, the world is now racing to find better ways to model, prepare for, and mitigate El Niño.
One challenge scientists must overcome is that the mechanisms behind El Niño are not yet fully understood. In a simplified sense, El Niño events originate from slack trade winds along the equatorial Pacific Ocean. As trade winds weaken, the ocean’s surface currents reverse direction. While these winds regularly push water west towards Australia and Southeast Asia, during an El Niño event, they shift to move water east towards South America. The result is abnormally hot, dry conditions in the western Pacific and wet conditions in the eastern Pacific.
As warm water stagnates along the Pacific coast of South America, oceanic upwelling––the process by which cold, nutrient-rich waters are brought to the surface––slows down or stops entirely. The nutrients which rise to the surface of the ocean through upwelling, namely nitrates and phosphates, are crucial to the phytoplankton living along this stretch of coast. More importantly, phytoplankton make up the foundation for the marine food web in South America. In their absence, animal populations either die off or migrate elsewhere in search of food. Consequently, normally prosperous fisheries in Ecuador, Peru, and Chile find their catches dwindle in relation to El Niño.
Beyond South American fisheries, El Niño also dramatically alters routine weather patterns. The western Pacific, a region which already suffers from faster rates of warming than others, is most affected by El Niño-induced drought and high temperatures. In Indonesia, Australia, and India, unusually hot, dry summers lead to increased risk of wildfires igniting on wilted vegetation. With the abnormal heat and lack of precipitation also comes decreased agricultural output and reduced hydropower availability from insufficient rainfall. Furthermore, as the ocean warms, coral bleaching expands into some of the world’s most biodiverse reefs, in turn causing losses to the tourism sector. This becomes especially important for countries dependent on tourism for national revenue, like Australia and its Great Barrier Reef.
Across the Pacific, Ecuador, Peru, and Chile face the opposite problem. Increased rainfall from El Niño brings life-threatening flooding and mudslides to those living on the west coast of South America. Additionally, the warm, damp weather provides the ideal conditions for outbreaks of insect-borne diseases like malaria and dengue fever. Interestingly enough, certain areas of the Amazon Rainforest experience a drier environment in response to El Niño, similar to what is seen in Southeast Asia. This lack of moisture slows vegetation growth in the rainforest, ultimately reducing rates of carbon uptake by plants.
In an interconnected world, the force of El Niño holds no regard for national borders. The physical destruction inflicted by extreme weather events greatly affects the entire planet. What begins as decreased fishery productivity and agricultural disruption in a single country gives way to millions of people being impacted by food scarcity and public health crises. Losses to a region’s income, gross domestic product, and consumption of international goods brings instability to the global market. Furthermore, bouts of inflation and rising costs are the makings of social unrest in countries which depend upon such commodities as either imports or exports.
In light of 2023 being declared the year of El Niño’s return, experts have strategized how to mitigate what will likely be widespread devastation. In a study of past El Niño events conducted by the United Nations (UN), researchers found that disastrous effects were overwhelmingly exacerbated by vague forecasts, lack of education and communication, insufficiently allocated financial resources, political or economic crises coinciding with the event, and a general lag in response efforts. The UN went on to publish recommendations supporting the formation of regional organizations which establish collective response efforts to El Niño. In this way, groups of similarly-affected countries can streamline their government management, infrastructure, flow of information to the public, and early warning signals. By crafting a more refined approach to preparing for and responding to El Niño, the UN hopes to provide a framework to minimize damages caused by future events.
On the other hand is a network of scientists looking for innovative solutions to strong El Niño events. Common proposals include drought-tolerant crops, more expansive irrigation systems, and better agricultural storing methods. At the core of this research is the potential to make better predictions of ENSO phases and cycling. Although forecasting has improved in recent years, there still exists a great deal of uncertainty in modeling individual events due to differing sea surface temperature gradients, atmospheric pressures, and precise locations of origin. Related to policy, restrictions on agriculture exports and food import subsidies during the height of El Niño may prove useful.
The worst El Niño events are yet to come. Considering a rapidly changing climate, recurring cycles of El Niño have become one of the most dangerous weather phenomena of the current era. As the effects of El Niño continue to intensify in the coming years, the world’s population and ecosystems will endure the consequences.
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