El Niño: The Climate Pattern and its Impact
The Federal forecasters have confirmed that El Niño, the climate pattern, has arrived. El Niño is a natural disturbance in global climatic conditions that, while generally weaker, can have far-reaching effects on weather patterns and temperatures worldwide. The climate pattern begins when warm water accumulates in the tropical Pacific region west of South America, which occurs every three to seven years. This warming can lead to various effects through teleconnections, which include the warming of the stratosphere and cooling of the lower tropical stratosphere, potentially altering the jet stream that blows from west to east.
The Two Sides of El Niño
An El Niño occurrence creates two regions: the best of times for some and the worst of times for others. On a global scale, El Niño years tend to be warmer than La Niña years, El Niño’s opposite. A strong El Niño can typically increase temperatures by about 0.7 degrees Fahrenheit (0.4 Celsius) globally. However, local variation exists in North America, with the Pacific Northwest and Ohio Valley being unusually dry in the winter and fall. In contrast, the northern part of the US and Canada tends to experience warmer temperatures. The shift in the jet stream created by El Niño usually blocks moisture from the Gulf of Mexico from reaching the Southeast, reducing the fuel for thunderstorms. However, the Southeast regions tend to experience more severe weather activity than the South during La Niña.
Implications for Agriculture
El Niño can have varying effects on crops worldwide. In the middle of the US, El Niño is usually associated with warm and dry conditions that can slightly increase the likelihood of bountiful corn crop. Conversely, in Southern Africa and Australia, El Niño can wreak havoc and increase the risk of bushfires due to dangerously dry conditions, while North America is cooler and wetter. In South America, Brazil and northern regions tend to be drier, whereas parts of Argentina and Chile tend to be wetter.
The Challenges of Forecasting
The current El Niño is still weak, but forecasters anticipate steady growth. The National Weather Service dictates the onset of El Niño at 0.9 F (0.5 C) above normal water temperatures for three or more months in the Niño3.4 zone along the equator south of Hawaii, where El Niño occurs primarily. Strong El Niño requires a warming of 2.7 F (1.5 C) for three months in the Niño3.4 area. Though early advisory announcements from NOAA predict that El Niño has an 84% chance of being greater than moderate and, up to 56% chance of being strong by winter, such forecasts are subject to change. Despite the wide gap in predictions, however, static forecast models, like the one used by author Bob Leamon, are far less optimistic of a strong El Niño occurring this year. Alternatively, dynamic models that are similar to weather forecasting models are shown to have projected a very strong El Niño.
Conclusion
El Niño is a natural climate incident that occurs every three to seven years and can have significant impacts on global weather patterns. While it can contribute to warmer global temperatures, it may also cause local variation that can result in drought, severe weather, and wildfires. With the challenges of predicting El Niño’s strength, it is necessary to stay informed of forecast changes and prepare for either good or bad possibilities.
<< photo by André Cook >>
