Melting ice floes in Antarctica.
A state-commissioned report on climate change released Wednesday raises the stakes for fighting global warming, offering a clearer and, in some cases, more catastrophic picture of how much sea levels will rise in California...
The Bay Area will see the ocean swell as much as 3.4 feet by 2100 if significant action isn’t taken, the report says. The scientists who produced the study pegged the prospect of that outcome at 67 percent. Tougher action on greenhouse gases would mean a lesser rise of up to 2.4 feet, the study says.
The scope of the likely rise is largely in line with earlier estimates, but not completely. One worst-case scenario says ocean levels could rise 10 feet by century’s end, which would swamp countless homes, roads, harbors and even airports along the coast.
“We have learned that the potential for a higher sea level is greater than we thought,” said Gary Griggs, a professor of Earth sciences at UC Santa Cruz and one of seven climate experts who prepared the report.
The 71-page document was requested by the California Natural Resources Agency and the California Ocean Protection Council, in collaboration with the governor’s office, to help state and local officials plan for rising seas.
The report, an update of a 2013 state analysis, lays out expected ocean levels through 2150 for a number of locations and scenarios varying with the amount of greenhouse gas emissions globally.
Last year, nearly 200 nations committed in Paris to curb greenhouse gases enough so that the Earth’s temperature wouldn’t rise more than 2 degrees Celsius. The emission targets are not binding, however, and many scientists predict that President Trump’s executive order aimed at repealing Obama administration limits on coal-fired power plant pollution will prevent the U.S. from reaching its target.
The new analysis for California is based largely on recent, better information on ice melt at the Earth’s poles.
The main drivers of rising seas to date have been melting glaciers and the expansion of water that naturally occurs as temperatures warm. However, thawing ice sheets will soon become the primary contributor, according to the state-commissioned study.
The report indicates that Greenland has enough ice to raise global sea level by 24 feet while Antarctica has enough to lift oceans 187 feet. Glaciers, meanwhile, contain only enough ice to raise seas 1.5 feet.
While these continent-size masses of ice are not expected to completely melt, even a small amount of liquefaction could have big effects, particularly for California.
Because the ocean at the poles is lifted by strong gravitational forces, when that ice thaws and water is released toward the tropics, the liquid relaxes and spreads out, according to Griggs.
“It turns out for Antarctica, the biggest impact is along the California coast,” he said.
For every foot of global sea-level rise caused by melting ice in the western Antarctic, California will see the the ocean rise about 1.25 feet, according to the report.
The report emphasizes the importance of preparing for the spike.
“California leads the way in both addressing climate change and protecting our coastal and ocean communities and resources,” Jenn Eckerle, deputy director of the Ocean Protection Council, said in a statement. “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.”
Updated 5:49 pm, Wednesday, April 12, 2017
Rising Reality series
Read Chronicle urban design critic John King’s stories on the challenges posed by sea-level rise in the Bay Area: http://projects.sfchronicle.com/2016/sea-level-rise/
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