The major fire seasons in California over the past two years are part of a trend that scientists have been tracking for more than four decades. The area consumed annually by fires has increased significantly during this period, especially in the Sierra Nevada and northern areas of the state. Although Southern California also had a share of forest fires during this period, the region did not experience the same growth.

But this disparity between north and south is unlikely to persist. The number of days a year at increased risk of increasing forest fires in Southern California is projected to increase significantly by the end of the century, according to a new study led by UCLA.

A study published in Nature magazine Communications Earth and Environmentanalyzes data dating back to 1975. Researchers have not found a significant increase in the number of burned areas per year over the past 45 years.

“If you look at the whole state, there’s a statistically significant increase in the number of burns,” said UCLA climatologist Glenn MacDonald, co-author of the paper. “The North Coast and Sierra Nevada are contributing to that. There are no significant trends in the central and southern coasts to increase the annual number of burned areas.”

Under a scenario in which the average temperature in Southern California increases by almost 9 degrees Fahrenheit by 2100 – which would be likely if there were no significant reductions in greenhouse gas emissions – the study estimates that the number of days at high risk of fire will almost double up to about 58 days a year. Even in a more conservative scenario, if people take more drastic measures to slow climate change, and the average temperature in the region increases by about 5.4 degrees Fahrenheit, the number of high-risk days is expected to increase by an average of about 60%. year end of the century.

The researchers concluded in part by increasing low-resolution global climate models to predict regional conditions in more detail. They also studied what climatic factors correlate with major forest fires, and considered long-term projections for greenhouse gas emissions to see how these factors are likely to change over time.

Conditions that determine the likelihood and severity of forest fires in the southern part of the state are quite different from the north. In the south, for example, there are fewer lightning strikes, but a larger population means there are more human sources of ignition that could potentially cause a fire, and more people are at risk. And in the north there are more forests, where fires often leave burning because there is less significant danger to human life and property, while in the south there are more thickets, which are likely to burn more often.

Probably longer fire seasons

Researchers have concluded that most of the high-risk extra days fall at the beginning and end of the current fire season, which means fire seasons will last longer than they do now, MacDonald said.

Although the number of acres burned per year has not increased in Southern California for more than four decades, the region has not regretted it completely. In recent years, Thomas ’fire in 2017 burned more than 280,000 acres in Ventura and Santa Barbara counties, destroying more than 1,000 buildings; and the Woolsey fire in 2018 in the mountains of Santa Susanna and Santa Monica covered nearly 97,000 acres, destroying more than 1,600 structures, killing three people and evacuating nearly 295,000 people.

The Woolsey fire affected McDonald personally as he was evacuated from his home in Thousand Oaks. His house survived, but others nearby burned down completely.

“I look at our data and think,‘ Chances are you have one of these big ones fire events increase every year as we dump more and more carbon dioxide into the environment, “said MacDonald.” It’s not theoretical; it bothers me in the fall and early winter. ”

After watching the news coming out of the November COP26 global climate summit, MacDonald said the event did not reassure that sufficient measures would be taken to slow global climate change.

“I don’t think we can back down and wait for COP26 to save us because it won’t,” he said.

Instead, regional and local responses will be needed to reduce the risk of forest fires and mitigate other devastating effects of climate change – led by studies such as a new study led by UCLA.

Although the risk of forest fires in California will increase over the next few decades, whether climate change continues on the current trajectory or on a slightly more optimistic model, reducing emissions as soon as possible remains critical, the lead author said. Chunyu Dong.

“Carbon dioxide can stay in the environment for a long time,” said Dong, who is now an associate professor at the Center for Water Resources and the Environment at Sun Yat-sen University in China. “It will be too late when Southern California will fight the endless fires.”

The major fire seasons in California over the past two years are part of a trend that scientists have been tracking for more than four decades. The area consumed annually by fires has increased significantly during this period, especially in the Sierra Nevada and northern areas of the state. Although Southern California also had a share of forest fires during this period, the region did not experience the same growth.

But this disparity between north and south is unlikely to persist. The number of days a year at increased risk of increasing forest fires in Southern California is projected to increase significantly by the end of the century, according to a new study led by UCLA.

A study published in Nature magazine Communications Earth and Environmentanalyzes data dating back to 1975. Researchers have not found a significant increase in the number of burned areas per year over the past 45 years.

“If you look at the whole state, there’s a statistically significant increase in the number of burns,” said UCLA climatologist Glenn MacDonald, co-author of the paper. “The North Coast and Sierra Nevada are contributing to that. There are no significant trends in the central and southern coasts to increase the annual number of burned areas.”

Under a scenario in which the average temperature in Southern California increases by almost 9 degrees Fahrenheit by 2100 – which would be likely if there were no significant reductions in greenhouse gas emissions – the study estimates that the number of days at high risk of fire will almost double up to about 58 days a year. Even in a more conservative scenario, if people take more drastic measures to slow climate change, and the average temperature in the region increases by about 5.4 degrees Fahrenheit, the number of high-risk days is expected to increase by an average of about 60%. year end of the century.

The researchers concluded in part by increasing low-resolution global climate models to predict regional conditions in more detail. They also studied what climatic factors correlate with major forest fires, and considered long-term projections for greenhouse gas emissions to see how these factors are likely to change over time.

Conditions that determine the likelihood and severity of forest fires in the southern part of the state are quite different from the north. In the south, for example, there are fewer lightning strikes, but a larger population means there are more human sources of ignition that could potentially cause a fire, and more people are at risk. And in the north there are more forests, where fires often leave burning because there is less significant danger to human life and property, while in the south there are more thickets, which are likely to burn more often.

Probably longer fire seasons

Researchers have concluded that most of the high-risk extra days fall at the beginning and end of the current fire season, which means fire seasons will last longer than they do now, MacDonald said.

Although the number of acres burned per year has not increased in Southern California for more than four decades, the region has not regretted it completely. In recent years, Thomas ’fire in 2017 burned more than 280,000 acres in Ventura and Santa Barbara counties, destroying more than 1,000 buildings; and the Woolsey fire in 2018 in the mountains of Santa Susanna and Santa Monica covered nearly 97,000 acres, destroying more than 1,600 structures, killing three people and evacuating nearly 295,000 people.

The Woolsey fire affected McDonald personally as he was evacuated from his home in Thousand Oaks. His house survived, but others nearby burned down completely.

“I look at our data and think,‘ Chances are you have one of these big ones fire events increase every year as we dump more and more carbon dioxide into the environment, “said MacDonald.” It’s not theoretical; it bothers me in the fall and early winter. ”

After watching the news coming out of the November COP26 global climate summit, MacDonald said the event did not reassure that sufficient measures would be taken to slow global climate change.

“I don’t think we can back down and wait for COP26 to save us because it won’t,” he said.

Instead, regional and local responses will be needed to reduce the risk of forest fires and mitigate other devastating effects of climate change – led by studies such as a new study led by UCLA.

Although the risk of forest fires in California will increase over the next few decades, whether climate change continues on the current trajectory or on a slightly more optimistic model, reducing emissions as soon as possible remains critical, the lead author said. Chunyu Dong.

“Carbon dioxide can stay in the environment for a long time,” said Dong, who is now an associate professor at the Center for Water Resources and the Environment at Sun Yat-sen University in China. “It will be too late when Southern California will fight the endless fires.”