Sea Level Denialism

For the purposes of providing evidence of a prominent climate denialist who denies that sea levels are rising, as mentioned in On Climate Denialism, I present Nils-Axel Mörner, retired paleogeophysics and geodynamics head from Stockholm University.  Along with believing that a period of cooling is imminent he also believes that sea-levels are going to decline rather than rise (which would make sense if we enter a period of cooling and ice coverage on land masses such as Antarctica and Greenland were to start building up again).  He further argues however that there is no (rapid) rise in the sea-level going on today.  It’s unclear what “rapid” means in this context – Mörner seems to vary his claim from no more than 1mm a year over a long period (since 1850 for example) to nothing (since 1970 or since 1992).

An argument along the same line was presented to me personally by my friend, JP, related to the readings at Fort Denison in Port Jackson (where Sydney Harbour is located).  The gist was more about the lack evidence of an accelerated rise since 1960 (in accordance with the “Hockey Stick” and which was raised in response to an article quoting the CSIRO).

JP sent me this home-made chart:

Fair enough.  It doesn’t really seem to be showing much of an increase, in terms of metres, perhaps 100mm over a period of 100 or so years.  There was also a complaint that the article referred to only mentions dates since 1993 which is coincidentally a low point, rather than since 1914 when measurements began.  I dug up another chart in reply:

The 1993 date relates to the beginning of dedicated sea level telemetry from satellites.  Note the chart is expressed in inches, not metres (a metre being slightly less than 40 inches).  It’s also showing the global average rather than readings at a single tide gauge.  According to NASA there doesn’t really appear to be much acceleration in sea-level rise since 1993, but the rise is nevertheless relentless (and there’s more significant acceleration over the longer period since 1880):

I am aware that looking at one data point (or one data collection station) out of context is fraught with danger and won’t necessarily tell us much about the global situation but indulge me for a moment.  I downloaded data from Fort Denison, and plotted 1993 to 2018 using a scatter diagram (note that others based on the same data set are mentioned in Sea Levels Rising):

That shows an increase of, in average, 3.6 mm per year or slightly higher than the global average – so the local data collection station output was representative of the global data after all.  The remaining question then is what did the IPCC AR5 (2013) projections look like (note projections, not predictions):

That black line at the end is 3.6mm/year, so it seems that while it’s a little lower than for RCP2.6’s central estimate, it still lies within the range of projections.  RCP2.6, by the way, is the mildest scenario in which radiative forcing peaks at 3 W/m² before 2100 and then declines.  Radiative forcing is a measure of the imbalance between energy into the climate and energy out.  Peaking at 3 W/m² is equivalent to peaking at 475 ppm CO2.  Currently we are at about 410 ppm CO2 with an annual increase of a bit over 2 ppm/year which means that, if we don’t start turning things around, we will exceed RCP2.6 just after 2050.  The next most lenient RCPs are RCP4.5 and RCP6.0, which have us hitting 4.5 or 6.0 W/m² before levelling out after 2150 – or 630 ppm and 800 ppm CO2.  At 2 ppm/year, with no change to our climate policies and practices, we will hit 620 ppm by 2130 and 800 ppm by 2215.

The trouble is that the rate at which the CO2 concentration is increasing is also increasing, so those dates are very conservative:

 

The positive news here is that the sea levels aren’t increasing as quickly as some projections were telling us they might but, on the other hand, they are increasing.

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I was going to address JP’s claims with respect to sea levels together with sea level-relate climate denial, but the article got too long, so I broke this part out, leaving the other section in Sea Levels Rising.