CovOps
 Location : Ether-Sphere
Job/hobbies : Irrationality Exterminator
Humor : Über Serious
 |  Subject: Special Report on Sea Level Rise  Tue Dec 04, 2018 9:24 pm | |
| Here are my conclusions:
Mean global sea level has risen at a slow creep for more than 150 years; since 1900, global mean sea level has risen about 7-8 inches. The implications of the highest values of projected sea-level rise under future climate change scenarios are profound, with far reaching socioeconomic and environmental implications. However, these projections are regarded as deeply uncertain and the highest of these projections strain credulity.
The IPCC and other assessment reports are framed around providing support for the hypothesis of human-caused climate change. As a result, natural processes of climate variability have been relatively neglected in these assessments. Arguments have been presented here supporting the important and even dominant role that natural processes play in global and regional sea level variations and change.
With regards to the four issues raised in the Introduction:
- Is the recent sea level rise (since 1993) of magnitude 3 mm/year unusual?
No, although this conclusion is conditional on the quality of the global sea level data. The available evidence shows the following:
- Sea level was apparently higher than present at the time of the Holocene Climate Optimum (~ 5000 years ago), at least in some regions.
- Tide gauges show that sea levels began to rise during the 19th century, after several centuries associated with cooling and sea level decline. Tide gauges also show that rates of global mean sea level rise between 1920 and 1950 were comparable to recent rates.
- Recent research has concluded that there is no consistent or compelling evidence that recent rates of sea level rise are abnormal in the context of the historical records back to the 19th century that are available across Europe.
Identifying a potential human fingerprint on recent sea level rise is confounded by the large magnitude of natural internal variability associated with ocean circulation patterns. There is not yet convincing evidence of a fingerprint on sea level rise associated with human-caused global warming:
- The slow emergence of fossil fuel emissions prior to 1950 did not contribute significantly to sea level rise observed in the 19th and early 20th centuries.
- The recent acceleration in mean global sea level rise (since 1995) is caused by mass loss from Greenland that appears to have been larger during the 1930’s, with both periods associated with the warm phase of the Atlantic Multidecadal Oscillation.
In many of the most vulnerable coastal locations, the dominant causes of local sea level rise are natural oceanic and geologic processes and land use practices. Land use and engineering in the major coastal cities have brought on many of the worst problems, notably landfilling in coastal wetland areas and groundwater extraction.
Local sea level in many regions will continue to rise in the 21st century – independent of global climate change.
Emissions scenario choice exerts a great deal of influence on predicted sea level rise after 2050. If RCP8.5 is rejected as an extremely unlikely or impossible scenario, then the appropriate range of sea level rise scenarios to consider for 2100 is 0.2–1.6 m. Values exceeding 2 feet are increasingly weakly justified. Values exceeding 1.6 m require a cascade of extremely unlikely to impossible events, the joint likelihood of which is arguably impossible.
Further, these values of sea level rise are contingent on the climate models predicting the correct amount of temperature increase. There are numerous reasons to think that the climate models are predicting too much warming for the 21st century, and hence the more extreme values of sea level rise (above 1 m) are arguably too high.
https://judithcurry.com/2018/11/27/special-report-on-sea-level-rise/#more-24504
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