In this blog post, we will examine how the El Niño and La Niña phenomena—exacerbated by global warming—threaten our climate and our lives, and analyze their impacts.
Global warming is over. Now, the Earth is boiling. This is not merely a figure of speech, but an expression that reflects the very real crisis we currently face. The Earth’s temperature has already risen by more than 1 degree Celsius compared to pre-industrial levels, and the resulting impacts are accelerating every year. Polar ice caps are melting, causing sea levels to rise, and extreme weather events are becoming more frequent worldwide. These changes are not merely problems confined to the natural environment. Declining crop yields, ecosystem destruction, and water shortages caused by climate change are having a direct impact on human society. Thus, global warming is no longer a story of the future; it has already become a serious problem in our daily lives.
As the Earth’s temperature rises, extreme weather events are increasingly threatening the planet. Among these, El Niño and La Niña are among the phenomena that most significantly alter the Earth’s climate patterns. El Niño originally referred to the phenomenon of abnormally high sea surface temperatures off the coast of Peru around Christmas. However, after observing that other abnormal phenomena occurred alongside this event, scientists concluded that El Niño was not merely a phenomenon limited to changes in sea surface temperatures off the Peruvian coast. Since then, El Niño has been defined as the term for all abnormal weather phenomena associated with changes in sea surface temperatures off the coast of Peru. In contrast, La Niña refers to the phenomenon where sea surface temperatures off the coast of Peru are measured abnormally low—the opposite of El Niño—and the abnormal weather phenomena that occur alongside it. The changes caused by El Niño and La Niña and their underlying mechanisms are as follows.
The Earth has a system known as the atmospheric general circulation, which is driven by solar radiation. This explains the dominant wind patterns that form across different latitudes of the Earth. The trade winds, westerlies, and polar easterlies are part of this atmospheric general circulation; in the South Pacific, there is a southeasterly trade wind that blows from east to west. These trade winds generate the South Equatorial Current, a large-scale water flow extending from the coast of Peru (Eastern Pacific) toward the coast of Indonesia (Western Pacific). This South Equatorial Current transports seawater to the Western Pacific. Consequently, the sea level in the Eastern Pacific drops; when the sea level in the Eastern Pacific drops, a flow of seawater is required to replenish the lost volume. Consequently, upwelling occurs, where cold deep-sea water rises to replenish the lowered sea level in the eastern Pacific. As a result, the annual water temperature along the Peruvian coast in the eastern Pacific remains low. Additionally, the southeasterly trade winds reach the western Pacific region and rise into the upper atmosphere there. The rising air forms a low-pressure system in that region and generates clouds. Consequently, clouds form and rain falls in areas where these updrafts occur, such as the Philippines, northeastern Australia, and Indonesia.
El Niño occurs when the southeasterly trade winds weaken. When the southeasterly trade winds weaken in this way, the South Equatorial Current, which is driven by them, also weakens. As a result, seawater in the eastern Pacific cannot move far westward, and the sea level in the eastern Pacific does not drop sufficiently. If the sea level in the eastern Pacific does not drop sufficiently, the flow of cold deep-sea water rising from below weakens, and upwelling also weakens. In this case, because cold water is not supplied in sufficient quantities, the sea surface temperature off the coast of Peru rises. When the sea surface temperature rises, the amount of dissolved oxygen and nutrients decreases, causing damage to fish stocks. This phenomenon has serious impacts not only on Peru but also globally. In addition to the Peruvian coast, the western Pacific region is also affected. Due to the weakening of the southeasterly trade winds, they are unable to reach the western Pacific region and instead rise upward. This creates an updraft, causing cloud formation and shifting the location of rainfall further east than usual. Consequently, while upwellings typically occur in the western Pacific, including northeastern Australia, they fail to develop during El Niño events, leading to severe droughts in these regions. Additionally, it is known that during El Niño events, abnormal weather phenomena occur, such as flooding in Central and South America and southern China, and high temperatures in Alaska and western Canada.
La Niña occurs when the southeasterly trade winds strengthen more than usual, the opposite of El Niño. When the southeasterly trade winds strengthen, the intensity of the South Equatorial Current increases. As a result, the volume of seawater transported from the eastern to the western Pacific increases, and sea levels in the eastern Pacific drop below normal. In this case, upwelling intensifies to compensate for the reduced volume of seawater. Consequently, due to the influence of the cold seawater brought up by upwelling, sea surface temperatures along the Peruvian coast—which corresponds to the eastern Pacific—become lower. When La Niña occurs, the strengthened southeasterly trade winds generate stronger updrafts in the western Pacific region. This is a contributing factor to flooding in the Philippines and Indonesia, which are located in the western Pacific. In addition, droughts in South America and severe cold spells in North America are known to be phenomena caused by La Niña.
The effects of El Niño and La Niña are not limited to climate change alone. They have far-reaching impacts on the global economy, agriculture, fisheries, and ecosystems. For example, severe droughts caused by El Niño can significantly reduce crop yields, leading to rising food prices. This can trigger serious food crises, particularly in developing countries. Furthermore, it affects marine ecosystems, leading to reduced fish catches, which can deal an economic blow to communities dependent on fishing. Similarly, La Niña can cause extreme weather anomalies in specific regions, leading to natural disasters such as floods or droughts, which can have serious ripple effects on the local economy and society.
In conclusion, El Niño and La Niña are not merely weather phenomena but major climate patterns with global implications. Understanding and preparing for these phenomena is emerging as an increasingly important task in the era of climate change. It is our collective responsibility to predict these phenomena more accurately through continuous research and observation and to develop appropriate countermeasures. If we fail to understand and respond to these phenomena effectively, we will inevitably face not only natural disasters but also the resulting social and economic turmoil. Therefore, systematic research and the development of policies addressing climate change, including El Niño and La Niña, are urgently needed.
