New Studies on Sea Level Rise Make Clear We Must Act Now

The bad news is that even modest global warming likely leads to dangerous sea level rise. The worse news is that continuing to do nothing about greenhouse gas emissions leads to levels of warming and sea rise that are unimaginably catastrophic.

Stabilizing at 2C (3.6F) warming leads to 2.5 feet of sea level rise by 2100 and a devastating 8 feet by 2300, a new analysis finds. The figure at the right is long-term sea level rise under scenarios of very aggressive CO2 mitigation (via one of the new studies, Schaeffer et al. in Nature Climate Change).

Stabilizing at 3C (the RCP4.5 scenario, close to 550 ppm CO2 levels) leads to about 3 feet of SLR by 2100 and over 11 feet of SLR by 2300. That would still require a huge amount of clean energy deployment in the coming decades (see here).

Staying near our current greenhouse emissions emissions path — the “reference” case below, which is not the worst-case scenario — still leads to over 40 inches of SLR by 2100 and then seas continue to rise 7 inches or more a decade!

Rate of sea level rise (in mm/year) under various emissions scenarios.

How future generations would adapt to endlessly rising seas at that rate (or higher) is hard to imagine — even if it were not accompanied by many other simultaneous catastrophes, including Dust-Bowlification, ocean acidification, and ever-worsening extreme weather. The time to act is now.

The SLR analysis above is based on a “a semi-empirical approach” using historical data (see RealClimate). It does not factor in the possibility of nonlinear disintegration of the Greenland or West Antarctic ice sheets, which is already occurring.

Below the jump is a Climate Central excerpt on this study and two others that just came out, which suggest sea level rise could be even greater in key parts of coastal America — JR.

Three New Studies on Sea Level Rise Bring New Concerns

by Andrew Freedman, via Climate Central

Three new sea level rise studies published during the past week offer sobering lessons for coastal residents and policy makers, spelling trouble for portions of the East and West Coasts of the U.S.

The first lesson is that sea levels won’t rise at the same rate everywhere — in fact, some unlucky places are already seeing sea levels rise at rates that are dramatically faster than the global average. Specifically, the 600-mile stretch of coastline from North Carolina to Massachusetts is experiencing rates that are nearly three to four times higher than the global average, a trend that may continue during the coming decades.

This finding comes from a study published June 24 in the journal Nature Climate Change. The study makes clear that some of the most valuable real estate in the country, from the beaches of North Carolina to the posh Hamptons in Long Island, and including major cities such as New York and Boston, may see severe coastal flooding events much earlier than other parts of the country.

As Margaret Davidson, director of the Coastal Services Center for the National Oceanic and Atmospheric Administration (NOAA) in Charleston, South Carolina, told the Associated Press that the new research has “huge” implications.

“Somewhere between Maryland and Massachusetts, you’ve got some bodaciously expensive property at risk,” she said.

The study, by researchers with the U.S. Geological Survey (USGS), emphasized that factors such as changing ocean currents, coastal land elevation fluctuations, and water temperature and salinity shifts in the North Atlantic Ocean are influencing the rate of sea level rise on the local level.

The study refers to the Cape Hatteras-to-Massachusetts stretch as a sea level rise “hotspot”….

“Ongoing accelerated sea level rise in the hotspot will make coastal cities and surrounding areas increasingly vulnerable to flooding by adding to the height that storm surge and breaking waves reach on the coast,” said Abby Sallenger, a USGS oceanographer and lead author of the study.

According to the Boston Globe, the study and others like it are prompting the city of Boston to require developers to take sea level rise into account when planning new development projects and take other climate change adaptation steps.

The USGS study is similar to a report on West Coast sea level rise that was published last week by the National Research Council. That report found that California stands to experience greater sea level rise impacts than other parts of the West Coast.

Climate Central’s research, entitled Surging Seas, shows that California, New York, and New Jersey have the third, fourth, and fifth largest populations on low-lying coastal land prone to sea level rise-driven coastal flooding issues, and New York City has the second largest population at risk of any city nationwide other than New Orleans.

Another paper from Nature Climate Change shows just how difficult it will be to avoid damaging amounts of sea level rise over the longer term unless greenhouse gas emissions are significantly slashed.

That study, by a research team in Germany, showed that even if global warming were limited to 2 degrees Celsius (3.6°F) compared to preindustrial times — a target that many policymakers and scientists now consider too difficult to achieve — global mean sea levels are likely to continue to rise during the next three centuries. On the bright side, the study found that emissions reductions that contain warming to 1.5°C (2.7°F) or below would “strongly” reduce sea level rise.

The researchers, led by Michiel Schaeffer of Climate Analytics and Wageningen University, found that if global average surface temperatures increase by more than 3°C, sea level rise could range between 6.6 and 16.4 feet by the year 2300, which would prove disastrous to many coastal population centers.

“. . . For New York City, it has been shown that 1 meter of sea level rise could raise the frequency of severe flooding from once per century to once every three years,” said study coauthor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research.

The study is the first long-term sea level rise projection that combines historical records of sea level rise during the past millennium with future scenarios for greenhouse gas emissions. It relied in part on estimates of the historical relationship between global average surface temperatures and global average sea level.

— Andrew Freedman is a senior science writer for Climate Central. This piece was originally published at Climate Central and was reprinted with permission.

12 Responses to New Studies on Sea Level Rise Make Clear We Must Act Now

  1. Paul Klinkman says:

    It’s not the general sea level rise, it’s the exceptional storm surge that ruins your day. These numbers simply will not compete with the 38 foot storm surge that category 2 hurricane Katrina tossed at Mississippi. If we double the power of the storm surge damage, or more likely if we increase it by a factor of 10, there will already be nothing left when the general sea level starts licking a few house foundations.

    Not that a 3 foot or 7 foot sea level rise won’t add to the height of the storm surges.

  2. Dan Ives says:

    Indeed, sea level rise will make storm surges even more destructive. And even though most coastlines aren’t affected by tropical cyclone storm surges, the sea level rise on its own will be devastating.

  3. rjs says:

    the loss of manhatten & it’s inhabitants can only be seen as a blessing for the rest of humanity…

  4. Rabid Doomsayer says:

    If you look at the paleo climatic record comparing temperature, CO2 levels and sea levels Then if would appear that the above estimates are very much on the conservative side.

    Already we have CO2 well above Eemian levels where the seas were at least three and possibly more than five meters higher than today.,5&as_vis=1

    To get CO2 levels as high as today you have to go back millions of years where the sea level was tens of meters higher than today.

  5. Joan Savage says:

    A finding of the Sallenger et al. letter (full quote below) is the 12-year time lag between land-ocean temperature anomaly index (LOTI) and sea-level rise difference (SLRD), with high correlation between them.

    This is a potentially powerful application for prediction of future rates of sea level differences in the Atlantic Coast’s Northeast Hotspot.

    From a GHG-boosted temperature anomaly to a sea change is only a twelve year interval! Wow.
    Twelve years seems like a short time, much shorter than thinking about the year 2100.

    “We find rate differences of Northern Hemisphere temperature (Land and Ocean Temperature Anomaly Index, or Northern Hemisphere LOTI: Fig. 4b,c and Supplementary Fig. S9B) explain 91% of the variance of NEH SLRDs (r2=0.91; 12 yr lag; positive indicates Northern Hemisphere LOTI rate difference leads SLRD). We find similar results with rate differences of global temperature (that is, global LOTI: r2=0.92; 12 yr lag). Good correlations were also found with rate differences of other temperature-based parameters such as Atlantic Multidecadal Oscillation (AMO) and Greenland summer coastal temperatures (AMO: r2=0.92; 8 yr lag; Supplementary Fig. S9C; Greenland coastal temperatures: see Supplementary Information; r2=0.88; 12 yr lag).

  6. sue houston says:

    These may very well be low numbers.
    Its unclear from the article if the studies even attempt to include feedbacks such as melting permafrost or methane clathrate releases.

    James Hansen has been predicting up to 5 meters of SLR by 2100. He’s been right before, unfortunately.

  7. Doug Bostrom says:

    Further to this subject it’s worth looking at this:

    Greenland ice sheet reflectivity at record low, particularly at high elevations

    In particular see abstract therein of forthcoming paper “Greenland ice sheet albedo feedback: thermodynamics and atmospheric drivers.”

  8. squidboy6 says:

    The surf was up in the last decade in the Santa Barbara Channel. Fourteen foot waves broke at the Harbor one year and half a dozen spectators were washed into the rocks at low tide – falling ten feet onto rip rap and then into the water under some boats. They were washed off the walkway fifty feet from the breakwater and the sand was on the beach was gone.

    These waves had been generated up the coast just past Point Conception. Surf’s up! The longshore current was so strong a whirlpool was generated near the mouth of the harbor. It’s been pretty normal this year except the water is a lot warmer than usual for this time of year.

    But don’t tell anyone since Santa Barbara hastes bad PR. They even outlawed solar panels one residences up until a couple of years ago. There’s no energy generated in Santa Barbara Country even though there’s oil and gas extracted and there’s not enough water for the farms, ranches, and communities so they have to pipe more in.

  9. MarkfromLexington says:

    If staying on our current emissions path leads to a 40 inch SLR and if the east coast is seeing SLR rates that are nearly three to four times higher than the global average, then the east coast can expect to see 10 to 13 feet of SLR by 2100.

    Can you tell me if I’m connecting the dots properly here?

  10. Joan Savage says:

    They weren’t reporting a 3 to 4 x ratio in SL rise.
    They found the NEH has 3 to 4 times the “sea-level rate differences” (SLRD) of the global average. The R’s in the abbreviations don’t mean the same thing.

    The increase in rate of SLR along the northeast coast is associated (proximally) with a slowing Gulf Stream. This report ties the slowing the Gulf Stream ever more closely to atmospheric temperature and ice melt, with a 12 year time lag (globally) and an 8 year time lag for Greenland ice melt.

    I’m not counting on the Northeast hotspot staying a constant SLRD for the next 82 years, as it is a dependent variable in the system.

  11. Joan Savage says:

    That should be 8 years for Greenland coastal temperature, not a direct measure of Greenland ice melt.

  12. MarkfromLexington says:

    Thanks Joan!