The deadly cocktail of factors for drought and fires in California

Drought worsens in this region of the US 0:38

(CNN Spanish) --

No, droughts and fires are not new in California.

However, the situation that the western United States has gone through in recent times is exceptionally serious and does not stop raising alarms.

Climate change, of course, is behind the worsening of conditions.

But how is it specifically involved?

And what other factors come into play?

We explain it to you.

Droughts in California are recurrent, says the California Public Policy Institute, explaining that the state has the most variable climate in the entire United States: very dry years and very wet years are common, while years with average rainfall They are rare".

Across the West, in fact, megadroughts are nothing new: Between 800 and 1600, for example, they occurred repeatedly, according to research published in February in

that reviews the government's drought information system.

In California, in recent decades there have been several episodes of significant drought, for example in 1976-1977, from 1987 to 1992, from 2007 to 2009 and, more recently, from 2012 to 2016.

However, what is happening now has reached another level: according to the cited study, the period from 2000 to 2021 was the driest in the western United States in more than 1,200 years.

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And climate change, with its sustained rise in temperatures, has made the megadrought 72% worse, according to the study.

The megadrought in the western US is the worst in 1,200 years 1:40

A thirstier atmosphere

One of the consequences of rising temperatures, explains the California Public Policy Institute, is the existence of a "thirstier" atmosphere that, through evaporation, absorbs more water from the earth, drying out soils and vegetation. .

"A thirstier atmosphere means that the same amount of precipitation leaves less water for plants, streams, reservoirs and aquifers. We get less benefit from precipitation because more of it returns to the thirsty atmosphere. Smaller storms, in particular, they may provide little or no water benefit if the atmosphere is thirsty," explains climate scientist Mike Dettinger.

Air can absorb 7% more water for every degree Celsius it warms, according to data from NASA's Earth Observatory.

Climate change, says the study published in

, is responsible for about 42% of the soil moisture deficit in the western United States since 2000.

An abandoned boat on a dry patch of Oroville Lake bed in Oroville, California, in a September 2021 image. (Photo: EDELSON/AFP via Getty Images)

less rain

To the increase in temperatures must be added the decrease in rainfall.

"There is good documentation that there is, in fact, less rain. What seems to be happening according to most climate scientists is that we are having longer drier periods," David Feldman, professor of planning, told CNN recently. urban and public policy at the University of California at Irvine, and director of Water UCI, in reference to the situation that crosses the west.

This, however, does not mean that there are no strong storms.

"The irony is that those longer, drier periods are punctuated by very intense storms," ​​says Feldman.

The snow factor

The proportion of precipitation that falls as snow also decreases with rising temperatures, says the Public Policy Institute of California.

And, particularly in California, snow cover is key because it accounts for about 30% of the water supply.

"The 'snow droughts' make it difficult to manage reservoirs for water supply and hydroelectric power generation," explains the institution.

This is also key, because the water reserves and underground basins can protect the state against a year that is dry, but it is the combination of dry years plus problems in the reserves that generates what are defined as droughts.

Drought favors fires (not only in the short term)

Twelve of the 20 largest fires on record in California took place in the last five years, NASA's Earth Observatory reviews based on state data, and states that they burned about 4% of the total area of ​​California.

This is just one of the many data that illustrate the severity of the California wildfires, intrinsically linked to drought and climate change.

How exactly?

In the short term, drought causes more serious fires by taking moisture away from trees and plants, making it easier for them to burn.

But in addition, in the long term, drought increases the amount of dead wood left in the landscape, which also increases the possibility of intense fires.

Will California's water rationing measures be enough?

1:53

How extinguishing some fires fueled others

California's fire suppression policy, which has lasted more than 100 years, has caused "excessive amounts of dead trees, leaf litter, and dry brush to accumulate in forests," leading to more severe fires, explains the Earth Observatory of the POT.

Before firefighters began to stop fires in the early 20th century, cases caused by lightning or the action of native tribes were periodically recorded in Northern California, explains NASA.

"These fires periodically burned the surface and removed leaf litter, brush and young trees, thus reducing the risk of serious fires," he explains.

In other words: low intensity fires had a certain positive effect in preventing others.

"But for the better part of a century, we've followed a policy of total fire suppression with few prescribed fires. That's left California with a lot of abnormally dense, overgrown forest stands," the California climate scientist told NASA. the University of California Daniel Swain.

That overabundance makes it easier for flames to climb up tree trunks and spread through the canopy, leading to more destructive fires.

the human footprint

As the state's population has increased in recent decades, more people have built buildings on and along the edge of fire-prone land.

This reality has a counterpart in numbers: in 20 years, the number of homes in California's urban-wilderness interface increased by one million.

This, explain the scientists cited by NASA, is also a key factor in understanding the progress of the flames.

More population, for example, means more power lines, which have sparked some of the most destructive fires in the state.

A home is seen engulfed in flames as the Beckwourth Complex Fire rips through Doyle, Calif., on July 10, 2021.

Is the drought solved with a year of good rains?

A year with good humidity probably won't end the drought, said Park Williams, a climate scientist at the University of California, Los Angeles.

The expert believes that it will take several years of above-average rainfall and snowfall to end the mega-drought.

With information from CNN's Stephanie Elam

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