The study confirms that sea level rise is accelerating and is in accord with other recent studies estimating global sea level rise at a metre or more by the end of the century, with the melting of land ice now the largest component of global sea-level rise (about 65%). Scientists say that Global Warming means 20 Metre sea level rise is in the pipeline.
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"The harms of climate change are all around us, but our leaders have failed to act to reduce this threat," said Shaye Wolf, climate science director at the Center for Biological Diversity, which has advocated for years to secure powerful reductions in greenhouse gas emissions in a media release.
The report says that large parts of the California coast could experience more than 1 metre (3 feet) of sea level rise by 2100, with a large earthquake amplifying this another metre or more. "Vertical land motions caused by plate tectonics and the ongoing response of the Earth to the disappearance of North American ice sheets have a significant impact on sea-level rise along the Washington, Oregon, and California coasts." says the report.
The report says that Global sea level is projected to rise 8-23 cm (3-9 in) by 2030, relative to 2000 levels, 18-48 cm (7-19 in) by 2050, and 50-140 cm (20-55 in) by 2100.
California will be particularly hard hit. South of Cape Mendocino sea-level rise is projected to rise 4-30 cm (2-12 in) by 2030, relative to 2000 levels, 12-61 cm (5-24 in) by 2050, and 42-167 cm (17-66 in) by 2100.
North of Cape Mendocino along the Washington, Oregon, and California coasts, sea level is projected to change between -4 cm (-2 in) (sea-level fall) and +23 cm (9 in) by 2030, -3 cm (-1 in) and +48 cm (19 in) by 2050, and 10-143 cm (4-56 in) by 2100. These values are lower than projections further north. But along this coast plate tectonic movements need to be considered. An earthquake magnitude 8 or greater along the Cascadia Subduction Zone would suddenly raise sea level along parts of the coast by an additional 1-2 meters (3-7 feet) over projected levels.
Some $100 billion worth of facilities that currently are high and dry are expected to become at risk from 100-year flood / storm surge events from these projections, including power plants, airports and seaports, transport and other coastal buildings and infrastructure.
Increased coastal damage is expected from the confluence of large waves, storm surges, and high astronomical tides during strong El Niño (ENSO) events. Strong El Niño events can boost sea levels by as much as a foot.
Some climate models predict a northward shift in North Pacific storm tracks. While some observational studies report that largest waves are getting higher and winds are getting stronger, there is insufficient records over time to confirm whether these are long-term trends. But even without an increase in storminess, the report warns that sea level rise will exacerbate and amplify the adverse impact of storm surges and high waves on the coast. The report estimates that sea cliffs could retreat more than 30 m (about 100 feet) by 2100.
Wetlands provide coastal protection against the destructive impact of storm surges and also provide significant carbon sink capabilities. The report says that "Wetlands are likely to keep pace with sea level until 2050. Their survival until 2100 depends on maintaining elevation through high sedimentation, room to move inland, or uplift."
According to a 2011 PRBO Conservation Science study of California coastal ecosystems, wetlands will need our help to survive which found that Marin County's critical marshes could face extinction as sea level rises. The study found that 93 percent of San Francisco Bay's tidal marsh could be lost in the next century with sea-level rise, combined with low sediment levels. The researchers recommended protecting areas from development or that moving roads or buildings may be necessary.
The IPCC 2007 report largely ignored ice sheet loss from their calculations of projected sea level rise, as estimating the non-linear dynamics of ice sheet loss was still at the very earliest stages. Instead, the calulations were based upon thermal expansion of the world's oceans caused by global warming. The increasing use of aquifer ground water also contributes to sea level rise, but is balanced to some extent by dams and above ground water storage. By 2009 some climate scientists here projecting that Rising Sea Levels may exceed one metre this century.
As the Greenland, Alaskan, West Antarctic Ice Sheet (WAIS), and mountain glaciers melt and retreat it causes changes in the distribution of mass on the planet, inducing regional changes in Earth's gravitational field which results in greater sea level rise in regions far away from the ice sheet mass loss - such as the west coast of the United States, Australia and the Pacific.
According to the Centre for Biological Diversity, deep and rapid greenhouse gas cuts are needed in order to avoid the most extreme and damaging sea-level rise and other climate change impacts. The organisation says the technology and legal tools to implement deep reductions are available today, with only the political will absent. The 40 year old Clean Air Act is the United States main tool for curbing greenhouse gas pollution. The Act has achieved major public-health gains while saving money and benefiting the economy. But the legislation is under attack from polluters and in Congress. The EPA has been slow with implementation of the Act for reducing greenhouse pollution to address the urgency of the challenges we face.
"Today's warning, coming from our country's leading scientific advisors, sends an urgent message to our president and other policymakers: We need strong action, right now, to avert climate catastrophe." said Shaye Wolf from the Centre for Biological Diversity.
While reducing greenhouse gas emissions has been slow on the national level, more than two dozen cities across the U.S. have joined the Centre for Biological Diversity Clean Air Cities campaign urging President Barack Obama and the EPA to use the Clean Air Act to address the global climate crisis and reduce carbon in our atmosphere to no more than 350 parts per million, the level needed to reach to avoid catastrophic climate change.
- Centre for Biological Diversity media release 22 June 2012, Study: Rising Seas Will Inflict Serious Damage Along the U.S. West Coast
- U.S. National Research Council, 22 June 2012 - Study: Rising Seas Will Inflict Serious Damage Along the U.S. West Coast - Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future (2012)