Earth is a fragile being, and one change in one part of the globe can affect multiple other locations, both near and far. This is especially true when the one change is in the giant Pacific Ocean. When the air and water of the Pacific Ocean becomes warmer, winters get wetter in places like Southern California and Southeastern America, while becoming drier in places like Southeast Asia and Australia.1 This natural phenomenon, also known as El Niño or Southern Oscillation, has been occurring more often, with more intensity, making it a topic worth brining up in the Climate Change talks.
Under normal conditions, trade winds blow from east to west (easterlies) in the Pacific Ocean, causing a “pile up” in the west Pacific.2 The surface waters of the west are usually warmer than that of the east (near South America) due to a natural occurrence known as upwelling. As wind blows across the surface waters, pushing the ocean, cold and nutrient-rich waters rise from the deep ocean to the surface near South America, causing the surface waters to be cool.3 Upwelling fuels a large majority of primary productivity, replenishing and providing nutrients to the creatures that live above the deep sea.
The thermocline is a transition zone between surface and deep sea waters.4 Temperatures of the ocean are usually constant until there is a gradual drop while passing the thermocline and then a severe drop when looking at the deep waters beneath.5 During normal conditions, the thermocline is at an angle because of the winds causing upwelling to occur in the eastern regions. El Niño occurs naturally and is the warming of the surface water by the warmer atmosphere of the Pacific Ocean along with the slowing of the winds driving the ocean. As the wind gets weaker, the ocean gets warmer, causing the wind to get even weaker and creating a positive feedback loop.6 The weakened winds suppress upwelling which then flattens the thermocline. With the suppression of upwelling, nutrients can no longer easily reach the surface water, severely decreasing productivity in the upper regions of the ocean. In fact, this phenomenon was first noted by fishermen in Peru and Ecuador who noticed a period of time, usually around Christmas, when the fish populations decreased. The fishermen decided that this was a time to repair equipment and prepare for the next season, since the output of the ocean was not optimal. They called this time period which usually lasted a couple months “El Niño,” or “the Christ Child,” due to its timing.7
The El Niño is usually followed by La Niña which is a cooling of the Pacific Ocean surface waters. As previously stated, the changes in ocean temperature not only affects the output of the ocean, but also the climate around the globe. This usually includes wet winters for the Northern Hemisphere and droughts in areas like South India, Australia, and Central America.8 The intensity and period of time between El Niños vary. They are predicted to happen about every three to seven years and vary in severity—from extra rainfall to extreme flooding, to increased hurricanes and storms. Their effects can be devastating to the communities that reside in areas within range of the storms, droughts, and other natural disasters. Not to mention the havoc wrecked on the fishing market and the farming industry in areas that will be laden with drought due to El Niños. But how does this concern global climate change?
The relationship between El Niño and climate change is a very controversial one. The theories are scattered all over the place. Some scientists claim that human activity has triggered something in the atmosphere that is causing this El Niño phenomenon to happen more often and for longer periods of time, thus explaining recent global warming. However, others contest that climate change due to human actions could be the huge player causing the increase in global temperatures, not El Niño.9 With so many polarizing views, it is hard to understand what role El Niño plays in global warming, or if it just a “natural variance.”10 In the past century, frequencies and lengths of El Niño have increased, as seen in the graph below.11
Although the graph shows how sporadic and random El Niño effects—in red—occur, the average temperature of the recent El Niños are larger than that of the ones in the past. This causes the overall temperature of surface water of the Pacific Ocean to steadily rise and, as one may assume, this has caught the attention of climate change researchers. Some researchers claim that this may be an early sign that climate change is already affecting the El Niño trend by shifting the center of action from the central and the eastern Pacific.13 Studies on fossilized corals are showing that recent El Niños are alarmingly more intense than previous years, however, there was a similar occurrence in the 17th century.14 Other researchers say that although the frequency is random and is not affected by human activity, the intensity of the most recent El Niños is a direct cause of global climate change.15 Thus, the answer is still unclear as to whether the recent intensity of the El Niño effect is related to climate change at all.
The current status of El Niño is an El Niño/Southern Oscillation (ENSO) – neutral,16 so there is currently no prospect of an El Niño occurring this year, although there is no way to predict when one is approaching. The National Weather Service provides ENSO status reports on a weekly basis that you can check here. Like many things related to the environment, there is much debate whether there is anything we can do to change the trend. All we can say now is that El Niños exist and they affect every part of the world. We can only speculate the connection of global warming and this natural but increasingly abnormal phenomenon.
