Sea Level Rise Projections, Reality or Hype?

Sea Level Rise Projections – Reality or Hype? (an update)

In recent years there has been much press regarding global warming (climate change) and how this will affect sea level, including claims that the oceans could rise up to 3 meters (10 feet) or more by 2100. Just how much weight should we give these high-end projections? If true, then vast areas of the world’s coastline could be flooded with increasing frequency during storm surges or even with king tides affecting huge numbers of people.
sea level blog image

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Interesting article. The conclusion of the article stated “There remains, however, a significant amount of uncertainty…”. That is clear, though the discussion as to whether climate change is anthropogenic in its origin does seem clear when one reads articles such as this one: Plimer Where CO2 COmes From

71% of the earth is covered by water. How many weather stations have you sailed by recently? Very little is known about the oceans impact on climate and extremely limited research is being conducted. My local meteorologist can’t even give me an accurate forecast of anything beyond two weeks. No way that you can convince me that the computer models that they are using to forecast decades into the future have even a tiny portion of the relevant variables dialed in with something approaching accuracy.

Photos and soundings of places like the San Francisco Bay have been remarkably consistent for over a hundred years. I was told 20 years ago that SF would be underwater by now. :man_facepalming: When the dire predictions turn out to be false, you loose precious credibility. We should be better stewards of our planet, however, scare tactics to force people into compliance will not have the desired results.
Pic of Alcatraz Island 100 years ago… looking about the same (sea level wise) as it did last week when I sailed by it.

What was the tidal level when the above picture was taken and when you sailed by?

SF Bay Tides:


Mean sea level rise in SF bay is less than 8” per 100 years. And no “spike” showing that it is rising any more rapidly today than it was long before you and I were born.

We should be taking better care of our planet/environment. But climate alarmists, that have the best intentions, are paving the preverbal road to hell. When actual real world measurements start showing alarming trends then I/we should be alarmed. Computer modeling predictions should be viewed with extreme skepticism. The computer models are woefully inadequate at making accurate predictions until they have a better understanding of all the real world variables at play.

I was using my “seaman’s eye” to compare the 100 year old pic with my recent real word one. But if you want actual data points they are freely available:

Yes that is the statistics, starting from the time of the Industrial revolution
But was the picture taken at HWS and you past by at LWS?

Max. tidal diff. this January is 8.5’ (+7.0’/-1.5’ CD) according to the Tide Tables above.
Without knowing the tidal status at the time the 100 year old picture was take it is hard to judge, even with a keen “seaman’s eye”.

Agreed. But the OP is predicting a 10 foot rise in sea level by 2100. I can assure you that my seaman’s eye can discern a 10’ difference in sea level from a pic 100 years ago from one today. The fact that we need to get out charts and tables to see if a change has occurred is evidence that the change has been minimal at best. Literally the approximate width of a thumbnail per decade in mean sea level change is what the real word data is showing. Not predicting, actual measured changes. I’m willing to bet that 100 years from now a pic of Alcatraz island will still look remarkably similar to the one that we see today. That doesn’t mean that we shouldn’t be doing a better job of preventing all forms of pollution. We absolutely should be doing more, but using poorly programmed computer models to frighten people into complying with crushing environmental regulations is equally evil.

Max tidal range is not equivalent to mean (average) sea level. If the mean sea level was to rise 10 feet, I don’t think our gangway would even reach the dock at high tide. You don’t need tide tables or even a seaman’s eye to recognize changes like that.

Hi Paul, The point of my blog is the Uncertainty of the projections

Paul, My post did not predict a 10 foot sea level rise. My post conclusion is “There remains, however, a significant amount of uncertainty regarding predicting future warming rates and thus sea level estimates for the next 50-100 years are problematic. Based on observed sea level trends since 1996, the best estimate for sea level rise by 2100 would be between 0.3 meters and 1.0 meters (1 foot and 3.3 feet) with the most likely outcome about 0.5 meters (1.64 feet).”

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For all the info I’ve seen, there has been only trivial rise in sea level over the last 100years.

Most of the estimates I’ve seen are on the order of a sea level rise of 6” to 36” over the next 100 years.

Up to 18” seems plausible. Less seems more likely.

I recall hearing that if all of the polar ice caps and glaciers melted that mean sea level would rise 14 feet. I have no idea how accurate that is.

The melting of ice that is already floating has no effect on sea level.

So the melt of the Arctic ice would not raise sea levels very much. The melting of the ground bearings and upland ice in the Antarctic is a different story.

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The main contributor in the Arctic re sea level is melting Greenland icecap. Melting ice from Greenland is currently estimated to contribute between 0.6 to 0.8 mm/yr to the overall sea level rise rate (about 2 inches by 2100). If the melt rate for Greenland ice doubled between now and 2100 then we would expect an additional 3 inches. Antarctica is not currently contributing to sea level rise, but may be reducing sea levels slightly

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Lots of variables are still unknown, making predictions quite unreliable. I read an article recently that was predicting that sea levels may change in a very unintuitive manner. Melting of ice sheets on land (Greenland/Antarctica) may cause the land mass to “rebound” upwards, causing local sea levels in places like Greenland to actually drop significantly (as the local land rises from less ice weight pressing it down on it). And sea levels at the equator to rise even more than recent projections as the melting ice from the polar regions migrates to the equatorial regions. I’m all for doing more “good” research by non biased researchers. However, that’s not what we have today. Accurate data from reliable sources that’s publicly available and funded by unbiased sources should be being done now. Most research that is being conducted today is confirming the biases of the people researching and funding them.

Rebound is called “glacial isostatic adjustment” and tends to occur at rates of 1-2 mm/yr

I thought that was a fairly well done thumbnail sketch of the issues. If you note, a significant portion of the article is dedicated to uncertainty, which is a theme here.
The interplay of geography and physical forces also plays a role that is rarely explored in pop media- ocean water distribution is uneven. That is, sea level is anything but level. Work done to model what sea level rise will do to things like seiches and the 2 global tidal waves (the bulge of water chasing the moon and its opposite across the world, via centrifugal and centripetal force) has been wildly inconclusive. The models are not developed.
What is known is that enormous volumes of water are kept inside these standing waves, and it is unknown if this will buffer, mitigate or amplify the effects of sea level rise. While we have sufficient understanding to appreciate the math involved (the proposed Canadian Passamaquoddy Bay tidal power project in the Gulf of Maine was cancelled for it’s potential to disrupt the seiche and flood Boston) no model yet predicts what will happen with standing waves.


FYI; It is not yr. 2100 yet.

Well, a humble & sceptical comment:
CO2 level in atmo IS rising and our contribute is certified.
Methane is also rising for several reasons And it’s more challenging.
Man’s footprint on earth ( fo’ long times I agree ) could bring at stakes our sheer survival.
So said, my opinion is: check out anomalies, search answers, of course be critical But keep
on mind every small sign must take us to great outbursts.
( too much computer models fogging our vision )

By the way thanks to Gruntledemployee, a clear picture.


One way to think about uncertainties, probabilities etc. is in terms of betting. What are you willing to bet on and how much?

For example the forecast here for tomorrow is for 6 - 10 inches of snow. Betting on exactly 8 inches (about 20 cm) is a bad bet, betting on 6-10 is a better bet, 4-12 inches better still.

As far as long-term vs short term; betting on what the high temp will be for the next 4th of July is not a good bet. Betting that the average temperature in July will be higher than the average temperature for this January would be a good bet.

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Maybe a look at:

will secure a bet…

GW my ass. I like the above answer to that.