Difference between revisions of "Check: CO2 emissions fingerprint on sea rise-SUPPLEMENT"

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Here follows an extended analysis of tide gauges in moderate climates in which sea water is not much warmed by direct sunshine. Theoretically any effect from CO2 should be as strong on those locations as on other locations. Tide gauges readings of Cuxhaven, San francisco, New York, Sydney and Fremantle were averaged as shown below. This provides an average of three long term measurements in the Northern hemisphere and two in the Southern hemisphere.
 
Here follows an extended analysis of tide gauges in moderate climates in which sea water is not much warmed by direct sunshine. Theoretically any effect from CO2 should be as strong on those locations as on other locations. Tide gauges readings of Cuxhaven, San francisco, New York, Sydney and Fremantle were averaged as shown below. This provides an average of three long term measurements in the Northern hemisphere and two in the Southern hemisphere.
  
[[File:5 tide gauges.png|800px|thumb|center|5 tide gauge readings in moderate climates (5 yr average, [mm/yr])]]
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[[File:5 tide gauges.png|800px|thumb|center|'''5 tide gauge readings in moderate climates (5 yr average, [mm/yr])''']]
  
 
Also in this data set the recent sea rise average appears possibly significantly higher than before. The average of the period 1995-2018 is ca. 3 mm/yr. In comparison, 1935-1954 has an average of ca. 2.5 mm/yr. To be more specific, the extra increase of sea rise of ca. 0.5 mm/yr (note: 5 cm / century!) could be ascribed to the strongly increased CO<sub>2</sub> emissions but of course, it could easily be significantly more or less. Separating in Northern and Southern hemisphere is more revealing:
 
Also in this data set the recent sea rise average appears possibly significantly higher than before. The average of the period 1995-2018 is ca. 3 mm/yr. In comparison, 1935-1954 has an average of ca. 2.5 mm/yr. To be more specific, the extra increase of sea rise of ca. 0.5 mm/yr (note: 5 cm / century!) could be ascribed to the strongly increased CO<sub>2</sub> emissions but of course, it could easily be significantly more or less. Separating in Northern and Southern hemisphere is more revealing:

Revision as of 17:02, 24 January 2020

Has sea rise been accelerating due to increasing CO2 emissions? - supplement by Tim88 - Main article: Check:_CO2_emissions_fingerprint_on_sea_rise


Additional details on this update of Holgate's 2007 analysis of sea rise until 2003.

Differently from Holgate (he applied a complex intermediate step) we simply averaged the raw data for an approximately global estimation of average sea rise. Here are the results for the eight long term sea level gauges, with added trend plots for different time periods:

Average of 8 tide gauges with moving averages [mm/yr]

The here updated sea level gauge data set shows a higher rate of sea level rise over the last two decades than the period 1925-1960, but not significantly higher than the period 1925-1942. The 1995-2018 estimated rate of sea rise is only about 30% higher than in 1925-1960, and similar to 1925-1942 (see the little graphs). Even the rate of 1999-2018 is only about 20% higher compared to 1925-1942.

Moreover, the very long term trends of the European and American tide gauges (see main article and here below) do not have such apparent trend variations. The long-term apparent trend and trend changes can be interpreted as largely due to natural variations, in particular varying solar radiation and sinking land, as well as due to global dimming. Solar effects over the last hundred years are not well known. The solar activity of Hoyt and Schatten (updated) differs considerably from that of some other recent estimations. Accounting for both suggests that the period 1990-2018 likely had approximately the same or slightly more solar activity than the period 1925-1960.

Holgate discussed decadal variations but there also appears to be a 60 year cycle, which suggests that soon the global rate of sea rise may go down again.


Additional graphs and analysis

Here's a separate graph of San Francisco and Cuxhaven, averaged:

Average sea rise [mm/yr] in Cuxhaven and San Francisco with trends

We see no remarkable changes in trend between 1855-1900, 1900-1960 and even 1960-2018.

The “bumps” around 1983 and 2016 can be ascribed to the very strong 1982-’83 and 2015-’16 El Nino’s. For completeness, also the effect of the volcanic eruptions of Krakatau in 1883 and perhaps Santa Maria in 1902 are visible. Agung in 1963 and Pinatubo in 1991 are noteworthy but are not discernible in this graph. Note also that the old San Francisco data may be slightly inaccurate due to a shift in location in 1898; a correction results in an even more linear picture.

The recent, increased rates of sea rise are of the same order of magnitude as in an earlier period, instead of being 400% higher. If we wildly guess that the contribution in global sea rise due to carbon emissions amounted to up to 20-30% in the first two decades of this century, then up to about 1 mm/yr (or 10 cm/century) could be due to the current rate of increase of atmospheric CO2. However, it is then puzzling that such a high global change in sea rise is not detected in the measurements in northern countries. A factor could be that solar output variations are partly responsible. The direct warming of water from sun rays is much less in moderate climates due to less intensity as well as higher reflection from the water surface.

Here follows an extended analysis of tide gauges in moderate climates in which sea water is not much warmed by direct sunshine. Theoretically any effect from CO2 should be as strong on those locations as on other locations. Tide gauges readings of Cuxhaven, San francisco, New York, Sydney and Fremantle were averaged as shown below. This provides an average of three long term measurements in the Northern hemisphere and two in the Southern hemisphere.

5 tide gauge readings in moderate climates (5 yr average, [mm/yr])

Also in this data set the recent sea rise average appears possibly significantly higher than before. The average of the period 1995-2018 is ca. 3 mm/yr. In comparison, 1935-1954 has an average of ca. 2.5 mm/yr. To be more specific, the extra increase of sea rise of ca. 0.5 mm/yr (note: 5 cm / century!) could be ascribed to the strongly increased CO2 emissions but of course, it could easily be significantly more or less. Separating in Northern and Southern hemisphere is more revealing:

Three Northern hemisphere tide gauges, 3yr average.
1930-1955: 3.3 mm/yr. 2000-2018: 3.7 mm/yr
Two Southern hemisphere tide gauges, 3yr average.
1940-1955: 4.5 mm/yr. 1995-2018: 3.5 mm/yr^^

In the Southern hemisphere there appears to be an additional sea rise in recent decades as the curve seems to be coming loose from the linear trend line. However, Sydney plays a significant role in this, and apparently it receives water directly from more Northern, sun-warmed areas (East-Australian current). In other words, Sydney was inappropriate for inclusion. Looking for alternatives, for example Antofagasta in Chili actually shows a slightly inverse trend for recent years:

Antofagasta tide gauge, 3 yr average

Downloadable files:
File:SanFrancisco-Cuxhaven-sealevels.ods
File:Global-8-gauges.ods
File:Global-5-tide-gauges.ods
File:Cuxhaven-SanFrancisco-NewYork.ods
File:Sydney-Fremantle.ods
File:ANTOFAGASTA 2510.rlr.ods


Discussion: in the Forum you can give comments, suggestions and criticism