In this series on "Big Fat Planet," we answer reader-submitted questions about Earth's climate. The following is from Dr. Bill Patzert, who specializes in sea level rise and climate forecasting. He is a NASA-JPL research scientist and media spokesperson on ocean- and climate-related space activities.
Question: Is "La Nada" connected to climate change, or is it only part of the Pacific's regular heating and cooling cycles?
The comings and goings of El Niño, La Niña and "La Nada" (neutral conditions) are natural cycles of the climate system. There is evidence that these important climate events have been happening for thousands of years. This latest image of a La Nada highlights the processes that occur on time scales of more than a year, but usually less than 10 years. These processes are known as the "interannual ocean signal." To show that signal, scientists refined data for this image by removing trends over the past 20 years, seasonal variations and time-averaged signals of large-scale ocean circulation. For the past several decades, about half of all years have experienced La Nada conditions, compared to about 20 percent for El Niño and 30 percent for La Niña.
Scientists are studying how global warming caused by humans will impact these natural events. It's a hot research topic and no one has really nailed the answer yet.
For context on La Nada, read this article.