SACRAMENTO (CBS13) — Historically, Sacramento Valley winters have been saturated with dense fog, making it difficult for drivers. But over the last few years, researchers say there have been fewer foggy days.

It’s been a fact of life, living in the central valley, winter skies can get socked in with dense fog and the near-zero visibility can create dangerous driving conditions that trigger massive car crashes.

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A new UC Berkeley study shows the frequency of foggy days is dramatically lower.

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Atmospheric researcher Ellyn Gray says Sacramento’s gray skies are clearing up. She said since 1980, there has been around a 75% decrease. Her team has analyzed seven decades of weather data and they’ve found the formation of dense fog is directly connected to air pollution levels.

“You have these small particles in the air and if you have high-enough relative humidity, the water can condense on them. They act as a cloud seed and in this case, it’s a ground cloud, so a fog cloud,” Gray said.

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So why are there fewer foggy days?

“Due to regulation controls, we have much less pollution, 50% less, and so that’s changed the frequency of the fog,” Gray said.

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Most of California’s greenhouse gas pollution comes from vehicles and those levels have been dropping due to improved fuel efficiency and tougher emission standards. It’s been a positive impact on air quality and now this study shows has another clear advantage.

“It’s remarkable to see a way that we can tie improved safety back to measures that the state took 35 years ago to begin reducing air pollution,” Gray said.

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Researchers say the valley fog is still a natural phenomenon that will never completely go away. The scientists plan on expanding their study to other parts of the country and internationally.