It was a few years ago I tool a look at the impact fewer sunspots might have on droughts when combined with the PDO phases in Northern California. To do that, I looked at the flow of the historic flow of the Sacramento River and then overlay the PDO periods, during the Dalton Minimum. Below is the chart that I created.
The Red and Blue dots denote the PDO phases. Red is Warm Phase. Blue is Cool Phase. The gold dots mark the minimum start of solar cycle 4 and the end of solar cycle 5, which were two lower than average solar cycles, similar to Solar Cycle 24 we are experiencing now. The red line is the average flow, about 18.6 Million Acre Feet. The green line smooths the data over six year periods.
As you can see, between the two gold triangles, river flow is below average, but there are no long term droughts.
According to a UC Berkeley paleoclimatologist on Channel 3 news last night, we would have to go back to the 1500s to find a similar drought. I looked at the record and the worst drought was in in 1580 AD, when the river flow dropped to almost 1 MAF. In 1579 it was 6.02. The average is about 18.6 MAF. The paleoclimatologist’s concern was long term droughts lasting 200 years or more in the past.
From 892 AD to 1112 AD there was a California drought lasting 220 years and a second 140 years from 1209 AD to 1350 AD. Each of these droughts were more intense than six-year dry spells that afflicted California from 1928 to 1934, or the more recent severe dry spell from 1987 to 1992.
California weathered the 1930s drought and the late 1980s drought, but we have continued to increase our population, while not increasing our water storage capacity. The question is, how long a drought can California survive, before we run out of water?