Dr. Lawrence Cahoon on Sea Level Rise

These are the questions presented to Dr. Lawrence Cahoon from BrunswickGreen.com regarding his article publshed by the Wilmington Star News titled:  “Lawrence Cahoon – Face the facts on sea-level rise”

(view article here http://www.starnewsonline.com/article/20120721/ARTICLES/120729928)

1. Based on the statement in 1(a) below, What is your findings regarding planetary alignments and sea level rise?

(a) Under its “Sea Level Rise“ subsection, NC-20′s website posts several papers by Nicola Scafetta, whose basic argument is that planetary movements in our solar system control Earth’s climate. None of his papers actually addresses sea level rise. (source: http://www.starnewsonline.com/article/20120721/ARTICLES/120729928)

Dr. Cahoon: I am aware of no mechanism by which planetary alignments can cause sea level rise. Gravitational effects by the sun and moon are well known influences on tidal amplitudes (there are 15+ modes of effect), but gravitational forces by themselves do not change the mass, density, or volume of sea water. The planets are much smaller and/or farther away, so following the well-known inverse square law of gravity from Newton, their gravitational effects are miniscule. If they had gravitational effects, we’d incorporate them into our tide predictions. Physical oceanographers are aware that changes in the distribution of the mass of water on earth, such as by melting ice caps and putting that water into the oceans, can affect sea level through changes in centrifugal force effects from earth’s rotation. Scafetta’s papers claim some kind of correlation between planetary alignments, the behavior of the sun, and earth’s temperature, but he has not identified any mechanism supported by data by which this happens. Most solar irradiance effects, by the way, happen in wavelengths that are irrelevant to surface temperatures on earth.

Planetary alignments have not been shown by any data or analysis I have read in the literature, Scafetta’s correlation claims notwithstanding, to cause any effects on earth’s climate. If they had, we would have looked especially closely at ENSO, the dominant inter-annual climate oscillation. No extra-terrestrial effects on ENSO have ever been demonstrated, and folks have looked hard for them, as good ENSO predictions would have immense value. In fact, the skill of ENSO predictions has declined recently, almost certainly owing to climate change. We are essentially certain that ENSO is an internally-driven ocean-atmosphere coupling phenomenon, not something caused by outside influences, even sun spots.

2. What observatory scientific experiment, with time measurements, regarding NC Sea Level rise has been conducted?

Dr. Cahoon: Technically we would not call such observations “experiments”, as true experiments have a manipulation, controls, and replication. There are two reasonably well trusted tide gauges in North Carolina with precision sufficient to analyze sea level rise. Bear in mind that they are necessarily confounded by local effects. The gauge at Duck is showing an average change of about +4.2 mm/year, while the one at Wilmington (in the CFR estuary) is showing about +2.2 mm/year. My geologist colleagues tell me that’s local geology – the Outer Banks are slowly sinking and the Wilmington region is slowly uplifting. The global rate of rise measured by satellites and integrated over the whole ocean between 66 degrees N and S latitudes is about +3.3 mm/year since the early 1990’s. It’s a bit noisy, owing to inter-annual variations, notably ENSO, which changes the hydrological cycle enough to alter the mass of water in the oceans between phases.

I would also offer that the two gauges in NC may experience effects from oceanic processes. Recent published work shows that the Mid-Atlantic Bight (where Duck lies) is experiencing rather rapid sea level rise owing to changes in ocean circulation – currents exert an effect on coastal sea level. Winds do as well, and the South Atlantic Bight has apparently experienced an increased intensification in the Bermuda High, which affects the intensity and duration of southwesterly winds, which in turn would act to lower sea level at Wilmington. The Wilmington gauge may also be affected by changes in salinity in the CFR estuary owing to dredging and drought. Salinity would affect density of water there and therefore water height.

The point is that sea level can be affected by a number of factors, as I said in my op-ed, and must be evaluated that way for any one location. Globally, we are expecting (and to some extent seeing) an acceleration of global sea level rise, although it is geographically uneven at this period in time. Bear in mind that as warming and ice melt accelerate, the global effects will begin to swamp the other local effects. Paleo-oceanography studies indicate a statistically significant relationship between global temperatures and sea level, with warmer temperatures yielding higher sea levels. That’s one basis for predictions. The problem is that the current warming is proceeding much more rapidly than previous warmings.

3. Do you have data regarding earth directed solar flares (Coronal Mass Ejection) and M/X Class Flares and their impact on the increasing rate of sea level rise?

Dr. Cahoon: I am a biological oceanographer and do not collect data on solar flares. I am aware of no mechanism by which solar flares could drive any trends in sea level. There is no evidence of which I am aware that solar flare activity shows any correlation with climate on earth. Most notably, the well-known sunspot cycle, with an average periodicity of about 10.8 years, has never been shown to correlate with any major climate oscillation on earth. That’s because it acts by affecting primarily high-energy UV fluxes(basic black-body radiation theory), which don’t affect earth’s troposphere. If solar flare activity (a different issue vs. sun spots) affected anything but electronics (through well-known electromagnetic effects) and auroras, we would be warning people to use extra sunscreen, wear foil hats, or predicting weather based on that. We’re not, so there you have it.

4. What is the impact of possible extreme oceanic volcanic eruptions and potential displacement of the sea level due to same? Has the rate of underwater eruptions accelerated in the past decade?

Dr. Cahoon: I am aware of no published work showing that submarine volcanism has changed in any significant way in recent years. There’s been a lot of work on undersea vents, but these are long-term phenomena and have not changed notably. We are also aware of sub-sea volcanic activity in “hot spots”, such as the one southeast of the big island of Hawaii. If submarine volcanism had somehow changed in any extreme way, we would have noticed it, as it would have had major effects on ocean chemistry, temperature, biota, etc. The sea level rise data show no evidence of changes consistent with massive changes in submarine volcanism. Moreover, the volumes of water involved in making noticeable changes in sea level occur are really massive, generally orders of magnitude larger than anything volcanic. You can do the math – the surface area of the ocean is about 362 million square kilometers. Calculate how much water you’d have to displace to drive the, say, 6 cm or so of rise we’ve had in the last 20 years. Bear in mind that the mass of the earth is essentially constant, so a bulge in earth’s crust large enough to affect the ocean’s level would have to be countered by a sinking of earth’s crust on land of equal magnitude. We’d have noticed.

5. What scientific data modeling has been conducted by you and your research team regarding ACTUAL rate of sea level rise along the NC Coast in the past few years (and acceleration thereof)?

Dr. Cahoon: Again, I am a biological oceanographer and my published research has focused on biological questions. I am familiar enough with the sea level issues to point you at people who do know and can vouch for the numbers I cited above – Spencer Rogers with Sea Grant, Stan Riggs with ECU, Rob Young at Western Carolina, among others. Have a look at University of Colorado‘s web site and check out their satellite altimetry-based maps of sea level rise on a global scale to put our NC situation in perspective.

6. What is your prediction on the rate of sea level rise along the NC Coast up to the year 2100?

Dr. Cahoon: As I don’t directly work on the data sets and modeling in question, I defer to the guys who do. We know the ocean is warming and expanding, and we know that ice melt is accelerating, so it’s safe to say that sea level rise will accelerate over what we have historically measured. The uncertainties in the whole climate system are large, partly as positive feedbacks in the system are very tough to model with any precision, so picking a number is easy if you don’t mind a lot of variance, hard if you think you want a precise forecast. Personally, given the accelerations I have seen in the published literature and the consistent underestimates generated by many models vs. actual results (likely a consequence of inability to incorporate positive feedbacks, which accelerate things), I expect rather more sea level rise than the “consensus” estimates. Most scientists tend to be conservative in predictions, as do I in my own work, but that means we are often surprised by the data. Note that the climate-forcing greenhouse gas emissions are accelerating as well.

Ultimately, the deniers are forced to claim that carbon dioxide, methane, nitrous oxide, ozone, CFCs and other greenhouse gases do not absorb infrared radiation, which is a false assertion, if they are to argue that something else is really happening.

I hope this is helpful. Public education is part of my job. Best wishes.

Lawrence B. Cahoon, Professor
Biology and Marine Biology
University of N C Wilmington


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