From record rainfall and flooding in winter to record heat and major wildfires burning into winter, 2017 hit a new benchmark for weather extremes in California.
But do a series of extreme weather events have a direct link to climate change, or just part of natural swings in daily weather?
"Its been an extreme year in California, and not only the rest of the U.S. but other parts of the world," said Dr. Noah Diffenbaugh, an Earth System Science professor at Stanford University.
"The warming we are seeing is not consistent with natural forcing alone," Diffenbaugh explained while speaking at Operation Sierra Storm in Lake Tahoe.
Climate models based on natural processes alone can’t account for the true numbers we are seeing based on human forcing with greenhouse gas emissions, Diffenbaugh said.
As more carbon dioxide is released into the atmosphere, a cause and effect cycle is also playing out within the Earth’s oceans. As more CO2 is absorbed, oceans are trending more acidic over time.
California's changing climate means the extreme weather the state has been experienced in the last five years provide a good preview into the future.
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"The percentage of drought years in California has doubled as the state’s temperatures have been higher than average," Diffenbaugh explained.
Based on current trends likely future impacts for California include more frequent droughts, higher snow levels and enhanced risk of flooding events.
"Global warming is a measurement," Diffenbaugh said. "It is not a matter of politics. It is not a matter of belief. If you believe in thermometers you have no choice to believe in global warming."
Data from the Western Region Climate Center and Desert Research Institute shows the trends in California since 1895. The last four years have been among the warmest for high and low temperatures in the last 123 years.
