Climate Experts Release Latest Science on Sea Level Rise Projections to Support California Policy Guidance
From the California Natural Resources Agency:
In a compelling analysis of the factors that affect how much the ocean will rise along California’s coast in coming decades, a seven-member team of experts has provided the State with a report on the best-available sea-level rise science — including recent scientific advances on the role of polar ice loss.
The report includes new information on the expected sea level changes that will occur based on different greenhouse gas emission scenarios. For example, with very successful mitigation efforts, the report states that there is a 67 percent probability that the Bay Area will experience sea level rise between 1.0 foot and 2.4 feet by 2100. However, if no significant mitigation efforts are taken, that range increases to 1.6 to 3.4 feet.
The report also emphasizes the importance of preparing for extreme but uncertain scenarios involving the rapid loss of the Antarctic ice sheet, which would have an enormous impact on coastal regions. In one such scenario, sea levels along California’s coastline could rise up to 10 feet by 2100 – about 30-40 times faster than sea-level rise experienced over the last century.
“Although our scientific understanding is rapidly increasing, waiting for scientific certainty about the rate or ultimate amount of sea-level rise is neither a safe nor prudent option” said Dr. Gary Griggs, Chair of the science team and professor at University of California Santa Cruz. “The sea-level rise projections presented in this report provide the scientific foundation for taking action today, preparing our coastal communities and mitigating hazards, and preventing much greater losses than will occur without action now.”
An estimated 75 percent of California’s population lives in coastal counties. Sea-level rise, already underway, threatens hundreds of miles of roads and railways, harbors, airports, power plants, wastewater treatment plants, coastal wetlands, beaches, dunes, bluffs, and thousands of businesses and homes.
The new science report was requested by the California Ocean Protection Council and the California Natural Resources Agency, in collaboration with the Governor’s Office of Planning and Research, the California Energy Commission, and the California Ocean Science Trust. Expertise on the scientific team includes risk assessment, climatic change, ice sheet behavior, and statistical modeling.
The science report will be presented on April 26 at a meeting in Sacramento of the Ocean Protection Council. The report provides the scientific basis for updating statewide policy, which guides state and local decisions along California shorelines.
“California leads the way in both addressing climate change and protecting our coastal and ocean communities and resources,” said Jenn Eckerle, Deputy Director of the Ocean Protection Council. “Our statewide policy on sea-level rise is another example of that leadership. We provide guidance to state agencies and local governments for incorporating sea-level rise projections into planning, permitting, investment, and other decisions, so it is critical that it is grounded in the best and latest science.”
The current State of California Sea-Level Rise Guidance Document, released in 2010 and updated in 2013, included a range of projections over various timescales, but did not estimate the likelihood that such levels would be met. The scientific team’s new report includes information on the likelihood of specific scenarios and provides a framework for evaluating risk, adaptive capacity and consequences from rising seas. This will allow local and state stakeholders to weigh the costs and benefits of taking action now against the potential harmful effects of inaction.
The science report will inform California’s sea-level rise guidance document, which will help cities and counties as they comply with state law that requires them to incorporate climate change into their planning efforts. The updated guidance document will also assist state agencies prepare for, and adapt to sea level rise, as directed by Governor Brown’s April 2015 Executive Order on climate change. Public input will be integrated into the final guidance document update, which is scheduled for adoption by the California Ocean Protection Council in January 2018.
The seven scientists who synthesized the latest science as a working group of the Ocean Protection Council’s Science Advisory Team, convened by the California Ocean Science Trust, are Gary Griggs, University of California, Santa Cruz; Dan Cayan, Scripps Institution of Oceanography; Claudia Tebaldi, National Center for Atmospheric Research; Helen Amanda Fricker, Scripps Institution of Oceanography; Joe Arvai, University of Michigan; Rob DeConto, University of Massachusetts; and Robert E. Kopp, Rutgers University.
Among their key findings:
- Scientific understanding of sea-level rise is advancing at a rapid pace. Projections of future sea-level rise, under high emissions scenarios, have increased substantially over the last few years, primarily due to new and improved understanding of mass loss from continental ice sheets.
- The rate of ice loss from the Greenland and Antarctic Ice Sheets is increasing. These ice sheets will soon become the primary contributor to global sea-level rise, overtaking the contributions from ocean thermal expansion and melting mountain glaciers and ice caps.
- Mountain glaciers contain enough ice to raise sea levels by only about 1.5 feet. In contrast, the Greenland and Antarctic ice sheets contain enough ice to raise global mean sea level by 24 feet and 187 feet, respectively. Although these ice sheets are not expected to melt completely, even on century or millennial timescales, the loss of even a small fraction of either of these huge ice sheets could have devastating consequences for global shorelines.
- For California, ice loss from Antarctica, and especially from West Antarctica, causes higher sea-level rise in than the global average. For every 1 foot of global sea-level rise caused by loss of ice on West Antarctic, sea-level will rise approximately 1.25 feet along the California coast.
- After 2050, sea-level rise projections increasingly depend on the trajectory of greenhouse gas emissions.
- While model results have revealed the potential for high rates of ice loss and extreme sea-level rise during this century if greenhouse gas emissions continue unabated, the precise magnitude and timing of when the Antarctic Ice Sheet may begin to contribute substantially to rising sea levels is uncertain.
- It is clear that sea-levels are rising. As cities, counties, and state agencies make decisions about adaptation and hazard mitigation efforts, it is increasingly important to incorporate long-range planning for sea-level rise. Consideration of high and even extreme sea levels in decisions with implications past 2050 is needed to safeguard the people and resources of coastal California.
For a schedule of upcoming listening sessions, and more information on the process of updating the State’s sea-level rise guidance document, please visit:
LADWP Runoff Preparations Underway in the Eastern Sierra Region
From the LA DWP:
The Los Angeles Department of Water and Power (LADWP) is working proactively to prepare for the arrival of anticipated massive runoff water resulting from this year’s near record snowpack in the Eastern Sierra Nevada Mountains. These efforts are in partnership with Inyo County, the Inyo Sheriff’s Department, Bishop Police Department, Cal-Trans, Southern California Edison and others, as a member of the Inyo County Interagency Emergency Preparation team.
Work to prepare for the anticipated high water flows began in late February. The efforts have been assisted by an Emergency Declaration from the Mayor of the City of Los Angeles to allow LADWP to take immediate steps to protect infrastructure and aid in managing flood waters while also protecting public safety. Inyo County issued a similar declaration.
To maximize the beneficial use of runoff water to the fullest extent, LADWP is spreading water throughout the aqueduct system to replenish local groundwater aquifers. Current spreading is moderate and will increase as runoff occurs in larger quantities later this spring and summer. LADWP is also maximizing flows in the LA Aqueduct by lowering reservoirs to create more storage space for runoff water and supplying the City of Los Angeles with aqueduct water in place of purchased water and groundwater wherever possible to manage excess flows. Further, LADWP crews are hard at work preparing, cleaning, and repairing water conveyance ditches, spreading basins, sand traps, and other facilities located on City of Los Angeles property, areas controlled by LADWP, and along the Los Angeles Aqueduct, in order to manage the anticipated runoff.
Water that exceeds what can be spread to recharge local aquifers and which does not make it into the LA Aqueduct system will end up on the Owens Lakebed, the natural terminus point for waters flowing down the Owens River. Once there, it will add to the existing 30 sq. miles of saline brine pools and is expected to cause significant flood damage to dust control infrastructure managed and constructed by LADWP over the past 17 years. These measures, spread over nearly 50 sq. miles of dried lake, have effectively reduced dust pollution in the area by 96 percent. Damage to these dust control areas may result in increased air pollution that could threaten the health of the public after the runoff evaporates in 12 to 18 months.
LADWP is also concerned by the potential of water overflow in and around the towns and communities of the Eastern Sierra and is actively providing assistance in preventing and controlling runoff that could impact the public. Emergency assistance will be provided on lands throughout the valley should flooding threaten the property of a partner agency or the public.
“Inyo County is no stranger to emergencies and disasters,” Inyo County Sheriff Bill Lutze said. “Our resilience comes from a strong unified command made up of local, state and federal agencies as well as a public that is proactive in emergency preparedness. We continue to be grateful for our strong working relationships with our allied agencies, including Department of Water and Power, as well as with our residents.”
In order to keep the public informed of the steps being taken to manage runoff to the greatest extent possible and minimize the impact to dust control measures, LADWP will issue regular updates of its runoff management efforts.
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About News Worth Noting: News Worth Noting is a collection of press releases, media statements, and other materials produced by federal, state, and local government agencies, water agencies, and academic institutions, as well as non-profit and advocacy organizations. News Worth Noting also includes relevant legislator statements and environmental policy and legal analyses that are publicly released by law firms. If your agency or organization has an item you would like included here, please email it to Maven.
