El Niño

May 20, 2024, 6 a.m. • By Adam Forster

Navigating the Shifts: Understanding El Niño’s Role in Our Changing Climate

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Image showing the April surface temperature variation compared to the average April temperatures between 1991 and 2020The recent El Niño event, which has begun to wane over the past month, has undoubtedly played a significant role in the unprecedented global surface temperatures we've been experiencing. Experts indicate that "El Niño weakened substantially over the past month, and we think a transition to neutral conditions is imminent. There’s a 69% chance that La Niña will develop by July–September (and nearly 50-50 odds by June-August)" (Climate.gov). The right hand figure shows the siginificantly elevated April temperature compared to the average for April between 1991 and 2020.

Understanding El Niño and its Global Impact

Figure showing the el niño mechanism. Hot air from Asia moves across the pacific towards South AmericaEl Niño is a complex climate pattern stemming from variations in ocean temperatures across the Equatorial Pacific, integral to the broader climatic cycle known as the El Niño Southern Oscillation (ENSO), which also encompasses the cooler La Niña phases. Characterised by the warming of ocean surface waters in the central and eastern Pacific, El Niño events disrupt the normal patterns of trade wind circulation, often causing these winds to weaken or even reverse. Typically, these trade winds blow westward, shifting warm water from South America towards Asia and allowing for the upwelling of cold, nutrient-rich water off the west coast of the Americas. However, during El Niño, this upwelling is hindered, leading to a substantial rise in sea surface temperatures and releasing large amounts of heat into the atmosphere. This thermal shift influences global circulation patterns and dramatically impacts weather systems worldwide.

The term "El Niño," Spanish for "the little boy," refers to the Christ Child, named for its tendency to begin around December. Fishermen off the coast of South America originally coined this term to describe the unusually warm waters that disrupted their fishing seasons. El Niño's effects extend globally, causing not just warmer conditions but also triggering extreme weather patterns, including significant rainfall and flooding in the Americas and severe droughts in Australia and Southeast Asia. It has been a known phenomenon for centuries, with early records from Spanish colonies in the Americas noting major climatic fluctuations as early as the 1600s. Interestingly, traditional knowledge in various parts of the world incorporates methods to predict El Niño events based on observations of natural elements such as the behaviours of birds, fish, and plants, underlining its deep cultural significance.

As we observe the recent weakening of this climatic event and the potential transition towards La Niña, which tends to cool global temperatures but still disrupts typical weather patterns, it's crucial to understand these natural phenomena's roles within our global climate system. Such knowledge is essential for predicting future conditions and preparing for the range of effects these climatic patterns can cause, especially as they may be exacerbated by human-driven climate change.

The Counterpart: La Niña

In contrast to El Niño, La Niña is associated with cooler-than-average sea surface temperatures in the same region of the Pacific Ocean. La Niña often has a cooling effect on global temperatures but creates its own set of weather patterns, typically the opposite of those experienced during El Niño years. For instance, while El Niño may bring heavy rainfall to the western coast of South America, La Niña could cause drier conditions in these same areas.

The Human Factor: Greenhouse Gas Emissions and Climate Change

Plot showing increasing surface temperatures over time.While El Niño and La Niña play crucial roles in short-term climate variability, the long-term warming trend we are witnessing is driven by human-induced factors, primarily greenhouse gas (GHG) emissions. To illustrate this point, we can compare the impact of past El Niño events with recent decades' temperature records. Historical data show that while El Niño years tended to be warmer than average, the baseline temperatures have risen steadily over the years due to human activities.

For example, the strong El Niño event of 1997-1998 was considered one of the warmest at the time. However, recent years without El Niño have seen similar or even higher temperatures, underscoring the significant role of GHG emissions in driving global warming. The continued increase in GHG concentrations in the atmosphere is setting new temperature records, which are now higher than what was observed during what were once considered exceptional El Niño events.

ConclusionImage of various effects of climate change.

As we observe the potential shift from El Niño to La Niña conditions, it is crucial to recognise and address the underlying, human-driven factors contributing to climate change. The transient effects of natural phenomena like El Niño do not mask the urgent need to reduce greenhouse gas emissions and mitigate their long-term impacts on our planet. By understanding both natural and anthropogenic influences on our climate, we can better prepare for and adapt to our increasingly dynamic global environment.

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