Climatologists worry California wildfires part of cycle of increasing magnitude

SAN FRANCISCO (KGO) -- There is growing concern among climate scientists that California wildfires are expected to keep breaking records for size. The top two in state history have happened just in the past eight months -- the Mendocino Complex and the Thomas fire.

The power of wildfires can be numbing, knowing that lives and property are being lost. The battle to contain them, a combination of ground-based fire science and precision air drops.

What worries climate scientists is the intensity and size of California's fires, creating a cycle of increasing magnitude.

RELATED: Mendocino Complex Fires grow to more than 290,000 acres

The Mendocino Complex fire has become the largest in state history, bumping last December's Thomas fire in Santa Barbara and Ventura counties to second place.

What's striking is that out of the 10 biggest wildfires in California, dating back to 1932... Seven of them have occurred in the past 11 years.

Alison Bridger is chair of meteorology and climate science at San Jose State. She says there are two factors behind this pattern of record-breaking fires. One is tied to variations in warm and cool surface water in the mid-Pacific, which affects land temperatures. It's called the Pacific decadal oscillation.

"We're in the part of the cycle where we're warmer and dryer and then we'll head to cooler and wetter" Dr. Bridger said. "And that would be driven by giant, slow oscillations in the Pacific Ocean."

LIST: Largest wildfires in California history

The other culprit, she says, is climate change, which is raising temperatures during the day and even at night when firefighters counted on cool weather to help.

"Relative humidity depends on water in the atmosphere but also temperatures, so you won't get that rebound at night quite as well as you used to as it's warmer overnight," said Prof. Bridger.

The result is a cycle that shows no sign of ending.

"The fire's going to be more likely in a warmer world more intense, spread a little further, therefore cover a bigger area, and therefore become the biggest fire in California history," she concluded.

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