Will It Be A La Niña Winter?



Photo by Atilla Bingöl on Unsplash

A little background first…

Global temperatures impact how heat and moisture move around the planet. Carbon dioxide from the burning of fossil fuels (gasoline, natural gas, etc.) and methane (mainly from agricultural operations and fossil fuel extraction) builds up in the atmosphere, trapping heat. Rain clouds form over warm patches of the ocean, and warmer temperatures cause more water to evaporate into the air. When excessive water vapor condenses into precipitation, it sets the stage for heavier downpours. Heavy precipitation events contribute to flooding and other negative consequences.

What’s Normal? What Does La Niña Mean?

A natural climate pattern called the El Niño-Southern Oscillation (ENSO) cycle is defined by opposing warm and cool phases of oceanic and atmospheric conditions in the Pacific Ocean and exists in three states: El Niño (the warm phase), Neutral, and La Niña (the cool phase). Normally, winds along the equator push warm water westward, which causes cold water from the deep to churn up to the surface. During a La Niña year, the winds are much stronger and cause a build up of cooler sea surfaces near the equator in the Pacific Ocean. (In contrast, unusually warm ocean temperatures near the equator characterize El Niño.) Deviations caused by human-induced climate change tip the delicate balance of this naturally occurring positive/negative feedback system and change surface temperatures of the eastern Pacific Ocean. This in turn affects weather all over the world and brings intense storms in some places and droughts in others.

What About Our Area?

There are no guarantees, but forecasters believe there is an almost 90% chance of La Niña conditions occurring between December 2021 and February 2022. NOAA climate scientist Michelle D’Heureux points out that it’s important to keep in mind that the La Niña effect depends on where you live in the United States. La Niña typically brings drier conditions to the southern half of the country and more rain and snow to pockets in the northern half. On the West Coast, a La Niña year brings storms to the Pacific Northwest but not to areas further south, particularly Southern California. In fact, Washington and Oregon will get some relief from their drought conditions, whereas California is too far south to count on it. Our state reservoirs have fallen to historic lows, and according to the U.S. Drought Monitor, thirty-eight percent of California is in the most severe category of “exceptional drought.” Northern California falls in “no man’s land,” right in the middle, between the wetter north and the drier south, so it’s hard to predict where the line will fall for our rainy season this winter. Water policy expert Jeff Mount notes, “We rarely seem to get the Goldilocks moment in California. It’s either too dry or too wet.”

Did The Torrential Rains Help?

We rejoiced when it rained recently, but the dramatic and extended rainfall that came in “one go” was far from ideal. Reservoirs gained some new water and wildfires were put out, but California’s ability to capture and store water from the downpours remains inadequate. The state relies heavily on the snowpack that builds up in the Sierra Nevada Mountains in the winter, melts in the spring, fills the streams, rivers, and reservoirs, nourishes wildlife, and steadily irrigates the state’s farmland. The heavy rains brought three feet of snow to the mountains, but global warming is causing it to melt way too quickly, thereby depleting the waterways it feeds. (Read here for more on how California's snowpack could disappear altogether within 25 years.) In any case, it makes sense to think of drought as something caused by climate change, not by the weather.

What Can We Do On The Home front?

Stay tuned for Part 2 of this discussion next month when we’ll learn how we can put whatever amount of rain we get to good use in our landscaping and edible gardens!

Sources for this article and further reading:











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