La Nina, the cold phase in the El Nino-Southern Oscillation (ENSO) cycle, is expected to appear with weak intensity this winter and last until spring next year. However, not all signs are consistent, and scientists are facing many unanswered questions about the link between ENSO and global climate change.
La Nina occurs when sea surface temperatures in the central and eastern Pacific Ocean drop below average, with a difference of at least 0.5 degrees Celsius. This causes major changes in atmospheric flows and global weather. In contrast to El Nino (hot weather), La Nina typically brings colder winters to North America, more rain to Australia, and affects the Atlantic hurricane season.
Although it has not yet reached the official threshold of a La Nina event, atmospheric conditions still show familiar characteristics. First, trading winds are stronger than normal, causing less rainfall in the Pacific. The second is the more active Atlantic hurricane season, with increased storm numbers and intensity. Third, there is an unusual drought in some areas, while other areas are experiencing prolonged heavy rain.
These signs are giving scientists a headache because they do not completely match traditional ENSO standards.
The US National Oceanic and Atmospheric Administration (NOAA) predicts that a weak La Nina will transition to a neutral state in the spring and last throughout the summer of 2025. A neutral state occurs when sea temperatures in the ENSO region range from -0.5 degrees Celsius to +0.5 degrees Celsius, leaving the weather not strongly affected by La Nina or El Nino.
In this context, local weather patterns often dominate, rather than the large fluctuations that occur when ENSO is active. However, recent neutral summers have coincided with unusually high temperatures globally, raising questions about the role of climate change in regulating ENSO.
One of the major challenges is understanding the interaction between ENSO and climate change. Unprecedented global sea temperatures over the past year are complicating traditional forecasts. According to NOAA, current ENSO indices may no longer accurately describe the phenomenon as the ocean warms.
Scientists are also debating whether climate change will increase the frequency of El Nino and La Nina, or make them more intense. "ENSO is a complex system where the ocean and atmosphere constantly interact. Climate change is like an invisible hand, regulating the knots of this system in ways we do not yet fully understand" - Tom Di Liberto, NOAA meteorologist, commented.
Although a weak La Nina does not bring historic cold winters, uncertainty in ENSO models is posing a major challenge. This phenomenon can cause extreme weather, mixed with unexpected fluctuations, especially when interacting with climate change.
According to NOAA, while waiting for more research and data, people and countries need to prepare for unpredictable weather situations, from extreme temperatures to fluctuations in rainfall, to minimize risks and damage this winter.
