The current El Niño weather pattern, which refers to climate patterns in the Pacific Ocean that push water toward America’s coast, began in June. Now, El Niño is projected to reach super status, which can result in drastic weather patterns such as high temperatures, floods and hurricanes.
Ryan Shadbolt is a senior academic specialist in the Department of Geography, Environment and Spatial Sciences at Michigan State University’s College of Social Science. As anticipation of El Niño’s impact this year builds, Shadbolt provides an overview of the science behind these weather patterns and their potential effects.
What is El Niño and how does it work?
El Niño is identified by warmer-than-normal sea-surface temperatures over the central or eastern equatorial Pacific basin. It is coupled with changes to the atmosphere above, which we call the Southern Oscillation. Together, we often refer to this interconnected system by the abbreviation, ENSO. El Niño events are semiperiodic on a cycle of 2–7 years. As easterly trade winds along the equator weaken, there is less upwelling of deeper, cold water along the western coast of South America. The result is the accumulation of warm water over the central or eastern equatorial Pacific.
Are certain parts of the country going to be more impacted?
Not necessarily. Severe weather takes place at specific times and places. In contrast, El Niño has more influence on the regional to global scale and on timescales of weeks and longer.
Do we expect Michigan’s fall and winter to differ from prior seasons?
From past events, we primarily expect that Michigan’s winter will likely be warmer than average. Given this, we can secondarily infer that while our precipitation amount may be similar to average, we may receive less snow, with greater likelihood for sleet, freezing rain, and rain.
How does El Niño differ from La Niña?
La Niña is approximately the opposite scenario of what was described above. With increased easterly trade winds and increased upwelling of cold water along the western coast of South America, the result is cooler-than-normal sea-surface temperatures over the central or eastern equatorial Pacific. The effects of La Niña over the Great Lakes region are also opposite that of what we see for El Niño.
What effects can El Niño cause?
While El Niño events vary, they typically emerge in the northern hemisphere in late summer or early autumn. Observations show anomalously warm sea-surface temperatures and changes to atmospheric conditions over the central or eastern equatorial Pacific. Generally, our local impacts from El Niño will reach their greatest magnitude in our mid-winter. With its associated effects on the jet stream, we observe changes to regional temperature and precipitation globally. Some regions may experience drier conditions, while others get wet. Some areas may experience warmer conditions, while others are cooler. Over the Great Lakes region, El Niño generally results in a warmer-than-normal winter season. With that, we may see reduced ice coverage on the lakes with impacts on water levels and coastal erosion. While our total precipitation may not change much, we could see changes in winter precipitation type with perhaps less snowfall, but greater likelihood for sleet, freezing rain and rain.
Why is this year’s El Niño expected to be intense?
According to the National Oceanic and Atmospheric Administration’s Climate Prediction Center, over the past month the current El Niño event has intensified with sea-surface temperature anomalies exceeding +3.0 degrees Celsius. The anomalies look similar to other recent events. However, subsurface temperature observations reflect that the warm water is extending to a greater depth than typical, with anomalies exceeding +10.0 degrees Celsius! Long-term temperature observations of Earth’s ocean volume confirm that our ocean has warmed over recent decades. In our warmer world, it is entirely possible that El Niño events will grow more frequent and more intense.
What years had notable El Niño patterns?
There are many notable past El Niño events. Some events of recent memory include 1982–83, 1997–98, 2014–16, 2023–24. You can read more from my former student, Chris Easlick, who published a piece summarizing past events.
What else should people know?
ENSO is a single ocean-atmosphere system connected with a geographic location and semiperiodic cycle. ENSO demands our attention because it is such a dominant player in our climate. However, it is just one of more than a dozen other such systems observed by climate scientists. The interplay between these systems is complex and remains an area of active research.
