Dear Dr. Singer,

Thank you for your excellent WSJ op-ed on sea-level!  I have a couple of comments on it.

First, all, or nearly all, of the supposed "acceleration" in sea-level rise actually occurred before the mid- or late-1920s. Many (though not all) sites saw a small measurable acceleration before 1930, which added between zero and 1.5 mm/year to the rate of sea-level rise, though it wasn't evident everywhere.

The most striking example was at PSMSL tide gauge number 1, Brest, France, which has more than 200 years of sea-level measurement data. Sea-level at Brest rose at a rate of 0.00 ±0.22 mm/year during the 19th century (1807-1900), but has risen at about 1½ mm/year since then.

Sea-level acceleration at Brest since 1900 = 0.00434 ±0.01175 mm/yr² (i.e., negligible and not even statistically significant):

https://www.sealevel.info/MSL_graph.php?id=brest&boxcar=1&boxwidth=3&c_date=1900/1-2019/12

Second, note that the supposed "1.8 mm/yr" rate of coastal sea-level rise is inflated by the addition of 0.3 mm/yr “GIA,” which is Prof. Richard Peltier’s model-derived estimate of the amount by which sinking of the ocean floor reduces measured sea-level rise. The actual average rate of coastal sea-level rise is only about 1.5 mm/year (about six inches per century).

Adding model-derived GIA to the global sea-level trend is useful for some purposes, but the sum is not “sea-level rise.” Rather, it is an estimate of what the rate of sea-level rise would be were it not for post-glacial sinking of the ocean floor.

In the words of Greg Goodman:

“it… means their “mean sea level” is now floating, phantom like, above the waves.”

Like a commenter over on Dr. Curry’s blog, I would call SLR+GIA “Fake SLR.”  Frederikse distinguishes the two more tactfully, by calling real SLR “geocentric sea level rise” and fake SLR “barystatic sea level rise.”

Real… er, “geocentric”… global sea-level rise is so slow that in many places it is dwarfed by vertical land motion, and/or coastal processes, like erosion and sedimentation.

In fact, the Nobel Committee meets at two such places: Oslo and Stockholm. At both of those locations sea-level is falling, rather than rising.

https://www.sealevel.info/MSL_graph.php?id=Oslo&boxcar=1&boxwidth=3

https://www.sealevel.info/MSL_graph.php?id=Stockholm&boxcar=1&boxwidth=3

Unfortunately for the Scandinavians, the rate of decline is not decreasing. So they have to keep dredging, to keep the harbors open.

At Skagway sea-level is falling >17 mm/year. Without the tiny reduction caused by global sea-level rise it would be slightly worse.

http://www.sealevel.info/MSL_graph.php?id=Skagway

And at Kushiro sea-level is rising 9 mm/year. Global sea-level rise is less than 20% of that.

http://www.sealevel.info/MSL_graph.php?id=Kushiro

Of course, both of those locations show zero acceleration, hence zero influence from anthropogenic carbon emissions — just like everywhere else.

Third, note that, contrary to a widespread misconception, sea-level rise due to thermal expansion does not necessarily affect sea-level at the shorelines, nor anywhere else, except locally, where the expansion occurs. Changes in the density of the upper layer of the deep ocean produce sea-level change which is strictly local, because gravity balances mass, not volume. So, for example, warming of the mid-Indian Ocean can affect sea-level measurements taken via satellite altimeter, but it does not affect the coasts, and should not be included in sea-level estimates used for coastal planning.

Floating ice is a more dramatic example of strictly-local steric sea-level rise. When the floating ice increases or melts, it has no effect on sea-level elsewhere.

Fourth, I agree with you that increased snow and ice accumulation on the Antarctic and Greenland ice sheets seems to be largely offsetting increased sea-level rise from other sources, such as melting ice sheets & glaciers.

Since precise measurements of CO2 began in 1958, CO2 levels have risen every year for fifty-nine consecutive years, from 315 ppmv in 1958 to 407 ppmv now, totaling a 29% increase, with no detectable effect on the rate of sea-level rise.

That is iron-clad, indisputable proof that CO2 emissions do not significantly effect sea-level.

That fact is surprising to many people, because they think that warming “simply must” cause accelerated sea-level rise, and the Earth’s climate has certainly warmed over the last century. Their confusion is usually because they’re only aware of three climate-related factors which affect sea-level: melting, glacier calving, and thermal expansion.

In fact, those aren’t even the most important.

There are at least eight factors which significantly affect global sea-level:

1. snowfall

2. sublimation of grounded ice

3. melting of grounded ice

4. glacier calving

5. thermosteric changes (thermal expansion)

6. vertical land movement, including post-glacial sinking of the ocean floor

7. groundwater extraction

8. water sequestration behind dams and in natural lakes

#5 on that list (thermosteric change / thermal expansion) is a special case, because thermal expansion of water in the upper layer of the open ocean (which is where most ocean warming occurs) causes strictly-local sea-level rise, only. Because gravity balances mass, not volume, such “sea-level rise” causes no net lateral flows of water, and doesn’t affect sea-level elsewhere. Thermal expansion in the upper layer of the open ocean causes sea-level rise which affects satellite altimetry measurements, but does not affect coastal sea-level.

#7, groundwater extraction, is anthropogenic, but unrelated to climate. It increases the rate of sea-level rise, and should be expected to cause a slight acceleration in sea-level rise, because rates of groundwater extraction are believed to be increasing.

#8, water sequestration in reservoirs and lakes, is also mostly anthropogenic, but it reduces the rate of sea-level rise. However, it also should be expected to cause a slight acceleration in sea-level rise, because most of the big dams were built and filled in the mid-20th century, and the rate of water sequestration has declined since then, but dam-building obviously is not climate-related.

#1 through #4 are the four factors which affect ice sheet mass balance in Greenland and Antarctica: snowfall, sublimation, melting, and glacier calving. The most important of those factors is snowfall. (If anyone reading this didn’t know that, it is probably because the sources you read only mention factors that cause ice mass loss, which means that you’ve been reading propaganda, rather than unbiased science.)

In both Greenland and Antarctica, snowfall is the most important of those four factors. In fact, in Antarctica, snowfall accumulation is approximately equal to the sum of the other three factors.

The magnitude and importance of snowfall on ice sheet mass balance (and thus sea-level) is illustrated by the story of Glacier Girl.

She’s a WWII Lockheed P-38 Lightning which was extracted in pieces from beneath 268 feet of accumulated ice and snow (mostly ice), fifty years after she made an emergency landing on the Greenland Ice Sheet.

Do the arithmetic and you’ll calculate an astonishing number: more than 5 feet of ice per year, which is equivalent to more than seventy feet of annual snowfall!

That ice and snow represents evaporated water, mostly from the Arctic and North Atlantic Oceans, which then fell as ocean-effect snow on the Greenland Ice Sheet.

The story of Glacier Girl is fascinating. You can read more about it here:
http://www.airspacemag.com/history-of-flight/glacier-girl-the-back-story-19218360/?all

and here:
http://p38assn.org/glacier-girl-recovery.htm

So, the key question is: what happens to snowfall in a warming climate?

The answer is that it increases, for two reasons.

First, it increases simply because warmer air holds more moisture. Every meteorologist knows that the biggest snowfalls occur when the temperature is not too far below freezing.

Second, a warmer climate should reduce sea-ice extent, increasing evaporation from the Arctic, North Atlantic, and Southern Oceans, and thereby increasing Lake/Ocean-Effect Snowfall (LOES) downwind. (Ice-covered water does not produce LOES.)

When additional snow falls on ice sheets and glaciers, in adds to ice mass accumulation and subtracts from sea-level.

Warmer temperatures do not necessarily melt ice sheets and raise sea-level. Where ice sheets or glaciers are near 0°C, or the ice is grounded below the ocean’s waterline, warmer temperatures can, indeed, accelerate melting. But most of Antarctica averages more than 40° below zero, so it is in no danger of melting from a few degrees of warming. Only in southern Greenland, on the Antarctic Peninsula, and where ice sheets are grounded below sea-level and in contact with the ocean, is significant melting even plausible.

So, we know that in a warming climate there are some factors which increase sea-level, and other factors which reduce sea-level. There’s no fundamental reason to suppose that either of those will dominate the other by a large margin.

We can, however, draw upon the historical record, to gain insight. At the best tectonically stable locations, sea-level has been rising at about 1½ mm/year (6 inches per century) since the 1920s or before, with no sign of significant acceleration due to rising CO2 levels.

Thank you for all you do, Dr. Singer, to bring sanity to the crazy issue of climate change!

Warmest regards,

Dave Burton
www.sealevel.info
M: 919-244-3316