By Isobel Whitcomb ‘17
A little over one year ago, the first predictions were made of a monster El Niño to come in the winter of 2015-2016. As predicted, El Niño did hit California with an nearly record breaking intensity. March drenched Northern California and reservoirs throughout the state are fuller than they have been in years. However, it doesn’t appear that the winter quite matched up to climatologists hopes. For instance, although the Sierra Nevada are back up to 92% of the historical average snowpack (up from the 5% reported in 2015), that number is still hovering slightly below average. And although this year has certainly given California much needed respite from the drought, climatologists warn that “one average year isn’t enough.”
If you didn’t catch my column published back in September on the then upcoming El Niño, here is a primer on the cyclical weather pattern: Occurring every 4-8 years in the Eastern Pacific Ocean (the side of the Pacific nearest to the Americas), El Niño is triggered by a sudden change in the trade winds that normally blow in from the East. During El Niño these trade winds don’t blow in, and the Eastern Pacific’s normally cool sea surface temperatures increase rapidly, causing adverse weather conditions throughout throughout the west coast of the Americas. These changes in weather patterns typically include drought in the Amazon and heavy rains throughout California. However, not all El Niños are equal in magnitude. The winter of 1997-1998 broke records as the strongest El Niño on record, bringing monsoon level gales to Southern California and inundating Northern California with floods.
It was speculated that this year’s El Niño would break records set by that famous winter. So far, it’s a close call. According to experts, this year’s El Niño has certainly ranked up there as one of the strongest on record. However, there are many different ways of ranking the strength of weather oscillations, from sea temperatures to atmospheric pressure to the force of wind patterns. Based on these various measurements, this year’s El Niño was very similar to that of 1997-1998, but there is no conclusive evidence that it was stronger in magnitude.
The good news is that thanks to El Niño, California’s landscape has undergone a transformation. The Sierra Nevada have the highest snowpack seen in 10 years. Lake Shasta and Lake Folsom, two of the state’s most important reservoirs, are at 105% and 119% of the average recorded water levels, respectively. This is largely thanks to the fact that El Niño struck Northern California with a much greater intensity than Southern California, actually leaving Southern California relatively dry. As I mentioned in my previous column, this scenario was ideal. California relies on the snowpack from the Sierras as its main water source, and Southern California has comparably poor rainwater management techniques. Had El Niño spared Northern California and poured down on Southern California, there might a very different outlook for the coming water year.
However, despite this good news, California isn’t out of the woods. We are still in a deep drought. One meteorologist commented that people are so happy to see rain, that they seem to have forgotten that even the seemingly large amount of rainfall received this year isn’t as much as it should be under normal climatic conditions. That is, this year’s El Niño brings us to just about average in terms of rainfall and snowpack for the past water year. Although rains have been heavy in February and March, it only just about makes up for the driest, hottest summer on record experienced in 2015. This fact coupled with the possibility of a La Niña event this summer (in which El Niño’s weather patterns reverse themselves, bringing drought to the West Coast) means that California needs to continue its water conservation measures.
Extreme weather patterns are part of the global warming phenomena. In the future, it’s likely that we will experience more extremely dry summers followed by very wet winters. Think of this past year of extreme weather as a trial run: California should use the 2015-2016 water year as a model for how to best harvest and conserve water in coming years. After all, it’s unclear whether the California drought is a natural disaster or a more permanent change.