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Are There Observable Phenomena In Our Area That Scientists Can Attribute To Climate Change?


"The discussion about climate change can seem a little bit abstract sometimes. My question is: are there observable phenomena in our area that scientists can confidently attribute to climate change?" - Ken, Chico 

That’s a great question and one that perhaps is harder to answer definitively than at first glance. Science has a pretty high bar for declarative statements. That’s pretty much why gravity and evolution are often referred to as theories.

Now, we obviously lack polar ice caps or sea levels here in interior Northern California — the items typically measured, mentioned and argued over — but there are plenty of natural systems locally, and people keeping tabs.

Agriculture is huge in the North State, as are rain, snow and migrating wildlife, not to mention temperature records dating back to the late 19th century.

I started with the Yuba-Sutter Farm Bureau, figuring who else is better connected to the land than farmers — people who financially live or die by crop yields? Surely there would be people who have noticed long-term changes to when the first and last frost occurs or precisely when to plant, pollinate or harvest.

Now, the farm bureau didn’t get back to me, but it also occurred to me that such observations might be dismissed as anecdotal. So, I turned to Dr. Hyunok Lee, a research economist for the Department of Agricultural and Resource Economics at UC Davis. She’s published a peer-reviewed paper after poring over data about the climate in the prime farm country of Yolo County. 

Since You Asked is a series that answers your questions about the North State. Submit your question by calling 530-433-4887 or emailing

“Our study suggests that climate warming is happening,” Hyunok Lee said.

But perhaps not in the most obvious way.

“The way it is happening, the pattern is, climate warming is happening by increasing the lows in the wintertime,” she said.

That in turn, impacts agriculture, especially some nuts and stone fruit that need cold periods to trigger dormancy.

“Some crops may require more ‘chill hours’ than other crops,” she said. “For example, cherries. Cherries is one of those crops which require lots of chill hours.”

Agriculture is responding by tweaking crop varieties, making them less dependent on cold.

But, what about animals? Particularly, migratory birds. If it were getting warmer, wouldn’t birds arrive later in the year, and leave earlier? I contacted the Sacramento National Wildlife Refuge Complex, operator of eight distinct sites in the valley. But, officials said they don’t analyze data concerning when species appear and depart. If they did, I was told, it may not be a reliable indicator. Short-term weather conditions and headwinds can delay migratory birds, plus, recent local farming changes — flooding, rather than burning rice straw — give waterfowl much more habitat than just the refuges, making it harder to derive any long-term trends.

Luckily, I had a much better find when looking into historic temperature throughout the region. is a website aimed at mainly city planners, helping them guide future development in hopes of making projects less vulnerable to a changing world.

Dan McEvoy is a regional climatologist with the Western Regional Climate Center, a joint project of the Desert Research Institute and the National Oceanic and Atmospheric Administration.

Using historic data collected across the Sacramento Valley since modern record keeping began, McEvoy said a distinct trend has emerged. The data confers with Lee’s findings, but covers a much larger area than just Yolo County.

“We’ve seen a very sharp warming trend from 1895 to present,” McEvoy said. “Temperatures have been getting warmer, but we’ve seen this really, much sharper warming occur from about 1970 to present, where, we’ve just seen this steady sort of increase.”

The trend also appears to be intensifying. He said 2014 was the warmest year on record for the region and all of California and that 2015 was the second warmest year.

“… and 2016 and 17 were all in the top 10 warmest years. And right now, this winter alone is shaping up to be one of the warmest on record,” McEvoy said.

How is that manifesting itself? Is that having knock-on effects?

Albert Lundeen is a spokesperson for the California Energy Commission.

“Some of the very largest and most destructive fires for instance have happened in the last decade, more than any other decade in the history of California, at least in the recorded history of California,” he said.

Lundeen also said more of the state’s annual precipitation is falling as rain, rather than snow — further evidence.

The commission has built a website called Although aimed at public officials — mainly city planners, helping them guide future development in hopes of making projects less vulnerable to a changing world. The site, available to the general public, also enables one to compare historic with more recent observations.

Mark Stemen, a professor of geography at CSU Chico and a fan of the site says the evidence is getting hard to ignore.

“You’re seeing the snowpack is starting to decrease, you’re seeing the fire danger start to increase, and these are pretty easy to track,” he said. “Heat days, the amount of days that are over 104 have almost doubled over the historic average, so yeah, we’re starting to see this. Climate change isn’t something that’s coming, climate change is here.”

While some look for reasons to deny it, it seems a consensus is building.