California Drought: Frequent and Severe Extreme Heat Events More Likely in the Future

The drought continues in California, and the desert is spreading further west. In addition to wildfires, the situation has also other lesser-known consequences which are discussed in this article.

Projected Increases In California Average Maximum Temperature. © LAO

The 122.9°F temperature threshold was reached on 11 June in Death Valley, California, a threshold that has not been reached this early since records began 100 years ago. The first months of the year January, February, and March were the driest on record. Only about 6 inches of rain fell in the wettest months of the year in the Sierra Nevada. By early June, the extremely low soil moisture was already four months above where it should be in late summer and early autumn. In some parts of California, soils are 40% drier than in the same period in 2016, which was a historic drought. The problem is that when precipitation is at its lowest, water demand increases for agriculture and people. The four driest years in a row are 2013, 2014, and 2015, followed by 2021.

The Californian desert is undergoing extreme and rapid drying, linked to climate change and exacerbated by the two-year La Niña phenomenon. The trend is more pronounced in the Southwest (California, Arizona, Nevada, and Utah), but is present throughout the West, even in the Rockies. Similar signs are also appearing in the east, with more heat waves, droughts, and more extreme weather events (floods and sandstorms).

LAO study predicts a global temperature increase of about 4-6°C in California between 2035 and 2064

Up to 6°C warmer in California in 40 years

An LAO study predicts a global temperature increase of about 4-6°C in California between 2035 and 2064 compared to the baseline average: the state’s desert area will be much more affected than the coastal zone. It should be noted that the summer of 2021 was already the hottest summer ever recorded in California, surpassing the record set in 2017. Between 1961 and 1990, the Los Angeles and Sacramento areas averaged four days of extreme heat per year. By 2050, forecast models predict an average of nine days of extreme heat per year in Los Angeles and up to 12 days per year by the end of the century. For Sacramento, the study predicts 20 days of extreme heat per year in 2050 and 28 days per year in 2100! For Fresno, the forecast is 29 days per year in 2050 (up from 5 today) and 43 days in 2100 or earlier.

Water rationing, fires, and energy impacts

All 58 counties in California are in a state of crisis. The drought is manifested by a decrease in snow cover in the western US during winter, faster melting of snow cover as temperatures rise, and more evaporation of moisture from the ground. Snowmelt accelerated by rising temperatures also increases the risk of flooding, especially on dry, impervious, or concrete surfaces. An estimated 1.5 million California homes will be at high risk of flooding by 2050. California’s vegetation is also changing. Low ground plants are dying in large numbers, and trees are weakening and becoming more susceptible to disease.

As for wildfires, as of early June, there had already been 2,000 fires in California since the beginning of the year. The drought and extreme heat have simply burned away vegetation, making it easier for fires to start and spread quickly. In 2018, the most destructive wildfires in the state’s history occurred, and five of the 20 largest wildfires in California history occurred in 2020 alone. Because of dry soils and vegetation, California officials expect another record fire season in 2022.

The droughts in the western US have had serious consequences on the levels of the two largest reservoirs, Lake Mead and Lake Powell: in the face of impending water shortages, the Southern Nevada Water Authority, which manages Las Vegas’ water supply, said, “We are 30 meters away from depriving 25 million Americans of water from the Colorado River”. 80% of Colorado River water is used in agriculture, and states are implementing a plan to convert farms to produce less water-intensive crops.

Currently, 6 million Californians face water restrictions, and some municipalities are rationing water. The governor has asked Californians to reduce water use by 15% based on 2020 usage in an effort to maintain sufficient levels in reservoirs for wildlife especially fish to survive. The target is far from being met: currently, the reduction is only 3.7%. This increasingly dry climate also has implications for energy: if the drought continues at the same level this summer – as expected – the hydroelectric grid will be operating at just 48% of its capacity.