Global and Regional Sea Level Rise Scenarios

The National Oceanic and Atmospheric Administration has released a report on Global and Regional Sea Level Rise Scenarios for the United States.

This includes a revised extreme level of rise of 2.5 meters by 2100, 0.5 more than used at Paris in 2012.


The Sea Level Rise and Coastal Flood Hazard Scenarios and Tools Interagency Task Force, jointly convened by the U.S. Global Change Research Program (USGCRP) and the National Ocean Council (NOC), began its work in August 2015. The Task Force has focused its efforts on three primary tasks:

1) updating scenarios of global mean sea level (GMSL) rise,

2) integrating the global scenarios with regional factors contributing to sea level change for the entire U.S. coastline, and

3) incorporating these regionally appropriate scenarios within coastal risk management tools and capabilities deployed by individual agencies in support of the needs of specific stakeholder groups and user communities.

This technical report focuses on the first two of these tasks and reports on the production of gridded relative sea level (RSL, which includes both ocean-level change and vertical land motion) projections for the United States associated with an updated set of GMSL scenarios.

In addition to supporting the longer-term Task Force effort, this new product will be an important input into the USGCRP Sustained Assessment process and upcoming Fourth National Climate Assessment (NCA4) due in 2018.

This report also serves as a key technical input into the in-progress USGCRP Climate Science Special Report (CSSR). In order to bound the set of GMSL rise scenarios for year 2100, we assessed the most up-to-date scientific literature on scientifically supported upper-end GMSL projections, including recent observational and modeling literature related to the potential for rapid ice melt in Greenland and Antarctica.

The projections and results presented in several peer-reviewed publications provide evidence to support a physically plausible GMSL rise in the range of 2.0 meters (m) to 2.7 m, and recent results regarding Antarctic icesheet instability indicate that such outcomes may be more likely than previously thought.

To ensure consistency with these recent updates to the peer-reviewed scientific literature, we recommend a revised ‘extreme’ upper-bound scenario for GMSL rise of 2.5 m by the year 2100, which is 0.5 m higher than the upper bound scenario from Parris et al. (2012) employed by the Third NCA (NCA3).

In addition, after consideration of tide gauge and altimeter-based estimates of the rates of GMSL change over the past quarter-century and of recent modeling of future low-end projections of GMSL rise, we revise Parris et al. (2012)’s estimate of the lower bound upward by 0.1 m to 0.3 m by the year 2100.

This report articulates the linkages between scenario-based and probabilistic projections of future sea levels for coastal-risk planning, management of long-lived critical infrastructure, mission readiness, and other purposes. The probabilistic projections discussed in this report recognize the inherent dependency (conditionality) of future GMSL rise on future greenhouse-gas emissions and associated ocean-atmosphere warming.

In recognition of the different time horizons of relevance to different decision contexts, as well as the long-term GMSL rise commitment (lagged GMSL response) from on-going increases in oceanatmosphere warming, GMSL rise and associated RSL change are quantified from the year 2000 through the year 2200 (on a decadal basis to 2100 and with lower temporal frequency between 2100 and 2200).

The 0.3 m-2.5 m GMSL range for 2100 is discretized by 0.5-m increments and aligned with emissionsbased, conditional probabilistic storylines and global model projections into six GMSL rise scenarios: a Low, Intermediate-Low, Intermediate, Intermediate-High, High and Extreme, which correspond to GMSL rise of 0.3 m, 0.5 m, 1.0 m, 1.5 m, 2.0 m and 2.5 m, respectively.

These GMSL rise scenarios are used to derive regional RSL responses on a 1-degree grid covering the coastlines of the U.S. mainland, Alaska, Hawaii, the Caribbean, and the Pacific island territories, as well as at the precise locations of tide gauges along these coastlines.

These scenario-based RSL values fill a major gap in climate information needed to vii support a wide range of assessment, planning, and decision-making processes.

GMSL was adjusted to account for key factors important at regional scales, including:

1) shifts in oceanographic factors such as circulation patterns;

2) changes in the Earth’s gravitational field and rotation, and the flexure of the crust and upper mantle, due to melting of land-based ice; and

3) vertical land movement (VLM; subsidence or uplift) due to glacial isostatic adjustment (GIA, which also changes Earth’s gravitational field and rotation, as well as the overall shape of the ocean basin), sediment compaction, groundwater and fossil fuel withdrawals, and other nonclimatic factors.

Key findings include:

● Along regions of the Northeast Atlantic (Virginia coast and northward) and the western Gulf of Mexico coasts, RSL rise is projected to be greater than the global average for almost all future GMSL rise scenarios (e.g., 0.3-0.5 m or more RSL rise by the year 2100 than GMSL rise under the Intermediate scenario).

● Along much of the Pacific Northwest and Alaska coasts, RSL is projected to be less than the global average under the Low-to-Intermediate scenarios (e.g., 0.1-1 m or less RSL rise by the year 2100 than GMSL rise under the Intermediate scenario).

● Along almost all U.S. coasts outside Alaska, RSL is projected to be higher than the global average under the Intermediate-High, High and Extreme scenarios (e.g., 0.3-1 m or more RSL rise by the year 2100 than GMSL rise under the High scenario).

Finally, the consequences of rising RSL are presented in terms of how the frequency of moderate-level flooding associated with a NOAA coastal/lakeshore flood warning of a serious risk to life and property may change in the future under the sea level scenarios.

The elevation threshold used to classify such events by NOAA on their tide gauges varies along the U.S. coastline, but in general it is about 0.8 m (2.6 feet) above the highest average tide and locally has a 20% annual chance of occurrence.

For example, using the flood-frequency definition, we find at most locations examined (90 cities along the U.S. coastline outside of Alaska) that with only about 0.35 m (<14 inches) of local RSL rise, annual frequencies of such disruptive/damaging flooding will increase 25-fold by or about (±5 years) 2080, 2060, 2040 and 2030 under the Low, Intermediate-Low, Intermediate and Intermediate High subset of scenarios, respectively.

Click to access techrpt83_Global_and_Regional_SLR_Scenarios_for_the_US_final.pdf

Leave a comment


  1. Alan Wilkinson

     /  9th February 2017

    0.3m per century is the current rate and has been for some time. It seems by far the most likely outcome. The conceded range of 0.3 – 2.5 is so vast it shows the level of confidence of any prediction other than the current rate is vanishingly small. That, of course, gets no headlines or funding.

  2. David

     /  9th February 2017

    I think it’s appropriate to use the Russian approach to the y2k bug;

    “If in the year 2000 we have a problem, we will fix it’

  3. Dave Kennedy

     /  9th February 2017

    While there may be good reasons to trade in seaside living in St Clair for burbs further up the hill, I’m not sure the current rate of sea level rise at Port Chalmers of 0.92 mm/year (which has remained virtually linear for the past ~100 years) is one of them.

    Click to access coastal-hazards-climate-change-guidance-manual.pdf

    I’m trying to figure out the rationale for including such dire scenarios… it a genuine expression of uncertainty or is it more targeted at pushing a political viewpoint, eliciting adulation among fellow climate devotees or, more cynically, ensuring future funding and associated largesse.

    Certainly, a little more transparent discussion of uncertainties would assist evaluation of such claims.

    • Alan Wilkinson

       /  9th February 2017

      The level of incompetence shown in the MFE “Guidance Manual” is pretty astounding, not least in demanding local authorities assume an average rate nine times greater than the present rate you report and three times greater than the current reported world average with absolutely no evidence of the huge acceleration that would be required to generate those numbers.

  4. PDB

     /  9th February 2017

    If you have time (and an open mind) go through the graphs & old newspaper clippings in the link below which show not only temperature data change upwards in favour of increased warming at the beginning of the 20th century but changes to data over the past decade or so that can’t be blamed on ‘data homogenization’. Note the more recent changes made go against the narrative in the newspapers and scientist data of the time (e.g. clear evidence of global cooling between 1940-1970 which climate scientists said in 1970 was minus 0.4c but has now ‘disappeared’ in more recent temperature records.

    Towards the end you can see the same changes have been made with sea levels – again increasing the rate of rise.

    Click to access Olympia-Washington-February-7-2017-3.pdf

  5. PDB, as I have said multiple times, its the Sun nor the CO2 responsible for climate change. I hope to say I told you so in 2022 when the next short Ice Age locks in. Meantime, I will watch with amusement the so called scientists arguing about the details. It is a pity that so much of the information has not been archived correctly so that we can recheck the data. But you know that already don’t you? The proof of the pudding is in the eating? Tell me one logical change in human behaviour that will put off climate change. Oh, you have none, well neither have I.

    • PDB

       /  9th February 2017

      I think we are on the verge of the turning of public opinion against the man-made climate change proponents – the computer projections and tales of impending doom have been so far out to what has actually happened the ‘cry wolf’ effect will kick in soon. Hence the warnings get more shrill and the projections more extreme. Just like the heatwaves and extremely high temperatures of the 1930’s led to a gradual cooling of the planet for the following 40 odd years so too will the highs reached in the 2010’s lead to a similar cooling.

      The movie ‘An Inconvenient Truth’, which helped bring man-made climate change ideas into the mainstream has been so wrong in its predictions that in years to come it will be classed as sci-fi rather than a documentary.

  6. David

     /  9th February 2017

    Pete I have been waiting for you to cover the dodgy temperature records that the Americans supplied to the Paris climate change shindig, apparently they didnt get peer reviewed and have been deleted from the computer.

    • PDB

       /  9th February 2017

      PG did reply when I brought this up a couple of days by posting an article debunking that article. The graph on the bottom of the Daily Mail article IS incorrect but the rest of the article is valid. We will see more whistle blowing in future as man-made climate change becomes questioned more and the fact that financial rewards are now being offered to potential whistle-blowers.

      • Brown

         /  9th February 2017

        It does appear that in the States at least the funding for laptop games masquerading as science is going to dry up. It will be nice to see some real science being done again.

  7. Rather than someone’s interpretation of a model with dodgy data, how about going to real data on sea level, like here:
    Note their comment “The graphs can provide an overarching indication of the differing rates of regional vertical land motion, given that the absolute global sea level rise is believed to be 1.7-1.8 millimeters/year. Note that they are relative sea level trends, and are not corrected for local land movement.”
    Or how about here:
    Where is the accelerating sea level rise – or is it another inconvenient truth?

  8. PDB

     /  9th February 2017

    Slightly off-topic but a brief reminder of the global cooling ‘crises’ of the early 20th century and 1970’s.

    “The title of a 1976 book by well-known science writer Lowell Ponte pretty much summed up the crisis, “The Cooling: Has the Next Ice Age Already Begun? Can We Survive it?”

    Ponte correctly pointed out that “global cooling presents humankind with the most important social, political, and adaptive challenge we have had to deal with for 110,000 years.”

    But not to worry after all. Earth’s temperatures soon began to warm up again.

    So did the political climate which ratcheted up media thermostats during then-Sen. Al Gore’s fiery 1988 Senate Committee on Science, Technology and Space Hearings.

    Yup, those same CO2-belching smokestacks which were previously causing hell to freeze over were now setting the planet ablaze.”

  9. unitedtribes2

     /  9th February 2017

    Great Ill be able to turn my wetland into a marina and park my boat by my bedroom

  1. Post 7. How Much Is Too Much? – Guy On Climate

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: