Sea levels off most of California are expected to rise by about three feet over the next century, according to projections released Friday by the National Research Council.
The study is arguably the most comprehensive report of its kind for the West Coast, and its conclusions fall into the range offered by other estimates in recent years. They reinforce predictions that coastal areas will face increased damage from storms and big waves — what the research council called one of the most visible effects of large-scale climatic changes.
“Following a few thousand years of relative stability, global sea level has been rising since the late 19th or early 20th century, when global temperatures began to increase,” said the peer-reviewed report, co-authored by Daniel Cayan, a research meteorologist at the Scripps Institution of Oceanography at UC San Diego.
Authors said global sea level likely will rise at a faster rate during 21st century, putting coastal development such as airports, homes and highways in harm’s way.
“One meter of sea-level rise in the next century is something like five times the sea-level rise we experienced in the 20th century,” Cayan said. “One meter would be enormous. Hopefully it’s not that much. If that materializes, it’s going to be a huge challenge for humans and structures and ecosystems.”
For California’s coast south of Cape Mendocino, the committee used models and measurements to conclude that sea level will rise 4 to 30 centimeters by 2030, 12 to 61 centimeters by 2050, and 42 to 167 centimeters by 2100, compared with 2000. Scientists acknowledged several uncertainties associated with their work, including a shortage of data and an incomplete understanding of the world’s climate system decades into the future.
A warming climate causes sea level to rise primarily by warming the oceans — which causes the water to expand — and by melting land ice, which drains water to the ocean. Sea levels at any given spot depend on a complex interaction of factors, such as ocean and atmospheric circulation patterns, melting of modern and ancient ice sheets, and tectonic plate movements.
Sea levels vary from place to place, depending on changes to the land and the water. For instance, most of the tide gauges north of Cape Mendocino show that sea level has been falling relative to the land over the past several decades, while most gauges to the south show that relative sea level has been rising.
“Sea-level rise will send reverberations throughout local and state economies,” Philip King, an economics professor at San Francisco State University, said when he released a study last year about the financial impact of rising seas.
Friday’s study was commissioned by California, Oregon, Washington and several federal agencies. California’s Natural Resources Agency said the study “confirms the need to take action to address the impacts of rising sea levels.”
“Our coast and ocean largely define California. Because of that, we must be keenly aware of and plan for sea-level rise,” said a statement by resources Secretary John Laird. “The National Research Council’s study will help policymakers and planners prepare for the next century.”
Local governments in San Diego County already are preparing for higher ocean levels by assessing the kinds of infrastructure that could be damaged and how to respond.