“The past 150 years have been wetter than the past 2,000 years,” Ingram said. “And this is when our water development, population growth and agricultural industry were established.”
Ingram made the statement in a video presentation that is part of the UC California Institute for Water Resources new online video series. The series consists of presentations featuring UC and other experts speaking on topics aimed at helping farmers and all Californians better understand and cope with drought.
Precipitation during the last three years in California has been low by standards set since records were kept, which began in the late 1800s. However, the current drought appears to be well within normal fluctuations in the state's climate, according to research by Ingram and other paleoclimatologists. A trend of gradually increasing temperature since the 1960s has been causing earlier spring snowmelt, decreased snowpack, and is predicted to cause more extreme droughts and floods.
In her 17-minute video, Ingram noted that her colleague Scott Stine of California State University East Bay found some of the first evidence of a medieval warm period in California by studying the water level of Mono Lake. The lake expands and contracts depending on the amount of runoff from the adjoining Sierra Nevada. Stine's research reveals a dry spell from 1,800 to 600 years ago.
Ingram studies sediment cores at locations near the San Francisco Bay, which is fed by a watershed that covers 40 percent of California.
“The salinity reflects precipitation and runoff from a very large area of California,” she said. “As fresh water comes in, it mixes with salt water. Sediment records changes in salinity over time.”
Looking at the chemistry of the sediment layers and their fossil composition, she was able to tease out a record of past floods and droughts.
“There was a significant increase in salinity during the medieval warm period,” Ingram said. “Salinity increased from 15 to 22 parts per thousand in the dry period.”
The higher salinity suggests there was less fresh water flowing into the bay.
Ingram said scientists believe the current warming trend will continue into the future.
“The drier climate will increase evaporation, so drier soils, more frequent wildfires, increased dust levels,” Ingram said. “It's also predicted that we will have more extreme climate; as the climate warms, you're adding more energy and more water vapor in the atmosphere. That will produce larger floods and deeper droughts.”
Detailed information about California's climate past and future may be found in a book Ingram wrote with Frances Malamud-Roam, The West without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us About Tomorrow.
Watch her talk here: