NOAA advisory: Persistent El Niño may impact U.S. winter weather

The National Oceanic and Atmospheric Administration (NOAA) released an advisory yesterday that there is a 90 percent chance or higher that an El Ni√±o will persist throughout the fall of 2015. They are also 85 percent confident it will continue throughout the 2015-2016 winter, influencing the U.S. weather. El Ni√±os form when a “three-month average warming of at least 0.5 degrees Celsius (0.9¬∞F) in a specific area of the east-central tropical Pacific Ocean” occurs. Using satellite data, the El Ni√±o event looks like a long, jagged ribbon of warm water spreading across the central and east-central equatorial Pacific Ocean (see Figure 1).

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Side effects of a long-running El Ni√±o event are “warmer and drier winters in the Northwest, northern Midwest, and upper Northeast United States” and “significantly wetter winters” for drought-stricken central and southern California. Other climate events associated with El Ni√±o years are above-normal tropical cyclones forming east of the dateline, less-then-robust tropical Pacific fishing, and flooding along the coasts of northern Peru and Ecuador.

NOAA predicts that “across the contiguous United States, temperature and precipitation impacts associated with El Ni√±o are expected to remain minimal” during the summer, but will increase into the late fall and winter. NOAA also expects the El Ni√±o will be a factor in a below-normal Atlantic hurricane season, and “above-normal hurricane seasons in both the central and eastern Pacific hurricane basins.” Because the “warm ocean waters suppress the nutrient-rich, cold water from reaching the surface,” which feed and sustain large fish populations, the entire equatorial ecosystem is affected.

El Ni√±os (also known as the El Ni√±o Southern Oscillation or ENSO) are also accompanied by a high pressure system over the western Pacific and a low-pressure system over the eastern Pacific. NOAA predicts this still-developing El Ni√±o will continue throughout 2015, with some computer models predicting it will persist into the late fall of 2015. NOAA did note in its announcement that the El Ni√±o may turn out to be ‘moderate,’ weaker then expected, or peter out completely. If the designated area of the Pacific Ocean decreases below the 0.5 degree Celsius threshold, the El Ni√±o is considered to have dissipated.

Currently, this still-developing El Ni√±o shows surface sea temperatures “in excess of 1 degree Celsius, with the largest anomalies in the eastern Pacific.” Some recent weekly values showed above-average temperatures in certain areas ranging from 1.4 to 1.9 degrees Celsius. Since 1979, when satellite data became available, research has shown no correlation between global warming and past El Ni√±o events. Consequently, “there is no scientific consensus on how/if climate change may affect ENSO.”

According to geologist James Kamis, deep-ocean volcanic vents are the most likely culprits for El Ni√±o events. “These vents emit massive amounts of heat that force warm ocean water to the surface, displacing cooler water in the process,” Kamis writes in an email. “This warm water then helps El Ni√±os develop and in the process warm the atmosphere above. The vents also emit enormous volumes of gases such as methane and CO2.”

Kamis doesn’t think the air above the Pacific Ocean has enough energy to heat such large swaths of ocean by more than the 0.5 degrees Celsius for such a prolonged period. He also thinks these vent gases have a profound impact on our climate that’s only now being understood. “The emphasis here is that the ocean is vast and largely unexplored. As such, we are finding more and more vents in the most unlikely of places,” Kamis writes in an email. “These vents are very big climate controllers. Not everything can be attributed to the trace gas carbon dioxide.”

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