The Green Analysis

El Niño, or ENSO, is a weather phenomenon in the Pacific Ocean that affects global weather patterns. In recent years, the world has associated ENSO with natural disasters, climate change, and extreme weather. However, ENSO is not caused by climate change and also doesn’t necessarily mean more severe weather. However, in many cases, it can actually cause weather to weaken in certain areas.

What is ENSO?

ENSO, or El Niño Southern Oscillation, is a phenomenon in the Pacific Ocean that has three states: the El Niño state, neutral, and La Niña, with El Niño lasting around a year and La Niña lasting 1-3 years on average. During El Niño, there are sea surface temperature anomalies and wind direction anomalies over the Pacific—specifically, warming over the east Pacific and cooling over the west Pacific, which causes the trade winds to reverse and become westerly or highly weakened. This is starkly different from the neutral state, where there is warm water in the western Pacific and cool in the east, which reinforces the easterly trade winds. La Niña reinforces the neutral state through increased heating in the west and cooling in the east, which further intensifies the easterlies. Each of these different states significantly alters global heat transport, impacting global weather in countless ways. For example, changes in where heat flows alter the winds, cloud formation, pressure systems, precipitation patterns, the jet stream, and much more. With how impactful knowing which ENSO state the world is in, the true cause of these cycles and how they shift from one state to another is currently a topic of extensive research.

Actual Impacts

The actual impacts of El Niño and La Niña are often hard to trace directly to these phenomena since they impact global heat transport in many different ways, but many things have been discerned. During El Niño, there is reduced upwelling in South America, droughts in Southeast Asia and Australia, heavy rains in South America, California, and the Gulf Coast, milder winters across Canada and the northern US, increased hurricanes in the Northwest Pacific, and fewer hurricanes in the Atlantic. During La Niña states, there is colder and stormier weather in Canada and the northern US, warmer and less stormy weather in the southern US, and strengthened hurricanes in the Atlantic with suppressed hurricanes in the Pacific. Since the effects of ENSO are so expansive on global heat transport, there are countless other effects that have been documented and even more that have not. Overall, El Niño phases cause higher than average sea surface temperatures, leading to more intense warm weather over North America and dryer climates in Oceania. While La Niña causes intensified cold weather in North America and wetter climates in Oceania.

Correlation to Climate Change

ENSO has been closely associated with climate change. Still, it is important to note that ENSO’s effects are not caused by climate change and that it is not a new phenomenon caused by recent anthropogenic climate change. However, what is true about ENSO’s correlation to climate change is that climate change may be intensifying the severity of ENSO phases and also increasing the frequency in which they occur, leading to concerns due to how expansive the effects of ENSO can be as climate change continues to worsen and further strengthen ENSO cycles.