Rate of sea level rise is controlled by natural oscillations

A new paper by Dr. Nicola Scafetta of Duke University examines the relationship of natural, solar-driven ocean oscillations such as the Pacific Decadal Oscillation (PDO), Atlantic Multidecadal Oscillation (AMO), and the North Atlantic Oscillation (NAO) to the changes in rate of sea level rise. He finds no correlation with atmospheric carbon dioxide or temperature.

Before I get into the Scafetta paper, here is some background.

Measuring sea level is more complicated than pounding a stake into a beach. Ideally, global sea level would be a rotating oblate ellipsoid of polar radius of 6365.752 km and equatorial radius of 6378.137 km in absence of any other forces. Gravity distorts this ideal shape to make it lumpy.

There are daily and seasonal variations, and storm surges in addition to the oscillations mentioned above. There are tectonic events: is the ocean rising or is the land sinking? Also, extraction of groundwater near coasts may cause the land to sink and present an apparent rise in sea level. All these confounding factors can produce a local rate of sea level change very different from global rate of change.

post-glacial-sea-level-riseSince the end of the last glacial epoch, sea level has risen 120 meters (393 feet), about one meter per century. Sea level is still rising at the rate of 1- to 3mm per year, according to NOAA, about the thickness of one or two pennies.

As you can see from the figure, the rate of sea level rise has changed on broad time scales. Scafetta has found patterns of acceleration and deceleration of rise at much smaller time scales.

Scafetta studied six long-term tidal gauge records sited to represent all of the world’s oceans. He found the rate of sea level rise “…to be characterized by significant oscillations at the decadal and multidecadal scales up to about 110-year intervals. Within these scales both positive and negative accelerations are found if a record is sufficiently long. This result suggests that acceleration patterns in tide gauge records are mostly driven by the natural oscillations of the climate system. The volatility of the acceleration increases drastically at smaller scales such as at the bi-decadal ones.”

“Tide gauge accelerations oscillate significantly from positive to negative values mostly following the PDO, AMO and NAO oscillations. In particular, the influence of a large quasi 60–70 year natural oscillation is clearly demonstrated in these records.”

A conclusion from this paper has implications for climate model predictions: “at scales shorter than 100-years, the measured tide gauge accelerations are strongly driven by the natural oscillations of the climate system (e.g. PDO, AMO and NAO). At the smaller scales (e.g. at the decadal and bi-decadal scale) they are characterized by a large volatility due to significant decadal and bi-decadal climatic oscillations. Therefore, accelerations, as well as linear rates evaluated using a few decades of data (e.g. during the last 20-60 years) cannot be used for constructing reliable long-range projections of sea-level for the twenty first century.”

The cyclical nature of the rate of sea level rise, and its quite variable accelerations and decelerations at different time scales may explain why different researchers get different rate values. So, scary stories saying we are doomed because of acceleration in the rate of sea level rise, such as the ‘science fiction” stories linked below, should be taken with a grain of salt.

Reference: Scafetta, N., 2013, Multi-scale dynamical analysis (MSDA) of sea level records versus PDO, AMO, and NAO indexes, Climate Dynamics, DOI 10.1007/s00382-013-1771-3.

See the full paper here.

See also:

Science Fiction from the University of Arizona?

More science fiction from the University of Arizona

University of Arizona dances with sea level

Sea Level Rising?

Sea Level Rise in the South Pacific: None

Sea Level Rise Declining says EU

Obama parts the waters, sea level drops

Size matters in sea level studies

Sea level rising fast along American East Coast – or not

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17 comments

  1. polluting the earth is my god given right! god made the world and all the pollutants so it’s obvious good.

    I mean why would we try to maintain the planets environment? its not as if god would ever let us destroy the place.

  2. While there is some valid science in this article, it is a great example of questioning a short term correlation, and totally confusing the larger picture. It is true that ocean temperature patterns such as El Nino’s have effects on Sea Level. But the larger fact is missed in this article. The planet’s temperature does change. As it changes, the ice sheets change size, changing sea level, which moves the shoreline. SL changes hundreds of feet. We have entered a new era as we have now departed from the ice age cycles of the last five million years. To see how sea level follows temperature and CO2 see the chart at http://www.johnenglander.net/420kyr-T-CO2-SL CO2 is off the charts. Global temperature and SL are already starting to rise. The long term pattern is clear and should be a cause for great concern.

    1. The graphs presented in your link show that CO2 does not have an effect on temperature and sea level. They show CO2 rising dramatically while temperature and sea level leveling off and declining.

      1. Apparently you are looking for an immediate or rapid effect Jonathan. You know that nature does not necessarily work that way in Earth science. CO2 traps heat and about 90% of it goes into the ocean, which has enormous heat capacity, meaning that the increase in temperature is fractional. Nonetheless it is enough to change the equilibrium size of the ice sheets and glaciers changing sea level over centuries. It is a matter of “lag time” in plain speak. Scientists might call it thermal inertia. As a geologist you would perhaps recognize some very slow lag times. For example nature has a way of reducing high CO2 levels through the weathering of rocks and the creating of calcium carbonates on land and in the ocean (corals, etc). Such processes take millions of years.
        While we can explain the delay for temperature and sea level to follow CO2, what is clear is that all three are now heading higher, where they would be starting to move down in accordance with the glacial cycles, aka Ice Ages, of the last five million years.

      2. The only thing that is clear is the rise in CO2. The rapid rise in sea level stopped 8000 years ago. Holocene temperatures reached their highest point 4000-8000 years ago and we have had a general cooling since then, modified by lesser warming and cooling cycles such as the Medieval Warm period and “little ice age.”.

  3. Scafetta continues to publish his physics-free post-hoc statistical curve fittings despite his undergraduate level mistakes. Past examples have been easily torn apart. Just some examples are at RealClimate and at Open Mind. I would not have let my undergrad statistics students get away with this sort of thing. Sheesh.

  4. To John Englander:

    Let’s return to your first comment, I have some questions. You state “We have entered a new era as we have now departed from the ice age cycles of the last five million years.” First let’s clarify terms for other readers. An Ice Age consists of glacial epochs separated by interglacial periods. Ice ages have occurred at intervals of approximately 145 million years. The cycle of glacial epoch-interglacial periods within an ice age is variable and seems to depend on which Milankovitch cycle has the upper hand. It is common for journalists (and even some geologists) to use the term“ice age” when they really mean “glacial epoch.”

    Now, what is your evidence that the current ice age has ended? Do you really mean to say that we will not have another glacial epoch?

    Second, you seem to believe that our CO2 emissions play a major role in driving global temperature. What is your physical evidence to support that contention?

    I believe that CO2 is a minor player and that its small warming effect is overwhelmed by natural climate drivers. And yes, I agree that global temperature changes and that ice sheets wax and wane. Do you think that reducing our CO2 emissions would really have any great effect on that?

    1. Jonathan Duhamel, Milankovich cycles have been causing slow cooling for several thousands of years. That effect has been overwhelmed by human greenhouse gas emissions (and into the early 20th Century by added contribution of increased solar radiance). Tzedakis et al. said “we should also be able to predict the duration of the current interglacial in the absence of anthropogenic interference,” and “glacial inception is possible despite the subdued insolation forcing, if CO2 concentrations were 240±5ppmv (Tzedakis et al. 2012).” That latter paper (“Determining the Natural Length of the Current Interglacial”) says “No glacial inception is projected to occur at the current atmospheric CO2 concentrations of 390 ppmv. … The end of the current interglacial would occur within the next 1500 years, if atmospheric CO2 concentrations did not exceed 240±5 ppmv.” There is no chance that CO2 levels will drop that low in the next several thousand years.

      An excellent explanation of the implication of past interglacials for our current one has been written as a series by Steve Brown.

      Here is Richard Alley’s excellent explanation of why CO2 plays a major role: “The Biggest Control Knob: Carbon Dioxide in Earth’s Climate History.”

      Reducing our CO2 emissions indeed would have a great effect on the warming. If you want to argue with any of those facts, why don’t you do so on those sites I’ve linked to, where the big kids play?

      1. The earlier Tzedakis paper you cite says “…thus, the first major reactivation of the bipolar seesaw would probably constitute an indication that the transition to a glacial state had already taken place.” And we have already seen the action of the bipolar seesaw, see The Arctic-Antarctic seesaw

        http://tucsoncitizen.com/wryheat/2012/09/24/the-arctic-antarctic-seesaw/

        The later Tzedakis paper, a modeling study, maintains that CO2 must be at or below 240ppm. That ignores the fact that we have had ice ages and ice age cycles when the CO2 was over 4000ppm (Ordovician) and over 2000ppm (end Jurassic).

        The “skeptical science” article pretends to be science but adds nothing.

      2. Tom,

        The Science News article is interesting. I think, however, they are ignoring a more probable scenario. Let’s posit that the initial atmosphere contained abundant nitrogen and methane, and little or no CO2 or oxygen. Methane, a greenhouse gas 65 times stronger than CO2 would account for liquid water early in Earth’s history.

        As cyanobacteria developed, they emitted oxygen. At some point approximately 2.5- to 3 billion years ago, the concentration of oxygen in the ocean caused precipitation of iron and manganese, thereby forming the great banded iron formations of the world. Once the iron was used up, the oxygen was released into the atmosphere. The reaction of oxygen and methane produced CO2 a greenhouse gas much weaker than methane. This change precipitated the first great ice age, the Huronian about 2.1-2.4 billion years ago. This scenario accounts for the presence of liquid water early in Earth’s history and for the very high levels of CO2 in the atmosphere at the time of the Ordovician and Jurassic ice ages.

      3. I’m sure you are correct, Jonathan, that hundreds of scientists studying this issue for decades have overlooked the most probable explanation. I assume you have been typing comments using the wifi that is on the plane on your way to get that Nobel prize.

  5. Why did you choose to review this one particular article? My reading of the Scafetta, et al. article is that its analysis methods are suspect, and highly focused on short term variation which we all agree happens. So what? It would be much more helpful to take a broader approach and review a meta-analysis that considers many articles on the topic. http://www.metoffice.gov.uk/media/pdf/t/f/AVOID_WS2_D1_13_sea-level.pdf This particular meta-analysis concludes that “sea level rise is very likely to continue; that the rise by the year 2100 is almost certain to be below two metres…” One or two meters rise in some regions would be of no consequence, and in other areas would be devastating. Perhaps you should send your article to the leaders of Kiribati or The Maldives, but I doubt it will bring them much comfort.

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