Thread by @curryja

Twitter thread summarizing my report on Sea Level and Climate Change judithcurry.com/2018/11/27/spe…

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.

1. 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.

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. Rates of global mean sea level rise between 1920 and 1950 were comparable to recent rates.

There is no 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 in Europe.

2. Has recent global sea level rise been caused by human-caused global warming?

There is no 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.

Acceleration in 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.

3. To what extent is local sea level rise influenced by global sea level rise?

The dominant causes of local sea level are natural oceanic and geologic processes and land use practices, notably landfilling in coastal wetland areas and groundwater extraction.

4. How much will sea level rise in the 21st century?

Local sea level in many regions will continue to rise in the 21st century – independent of global climate change.

If RCP8.5 is rejected as borderline impossible, then the appropriate range of sea level rise scenarios to consider for 2100 is 0.2–1.6 m [8 inches to 5 feet], to account for worst case possibilities.

Values of 21st century sea level rise exceeding 2 feet are increasingly weakly justified. Values exceeding 5 feet require a cascade of extremely unlikely to impossible events, the joint likelihood of which is arguably impossible.

These values of sea level rise are contingent on the climate models predicting the correct amount of temperature increase. However, there are numerous reasons to think that the climate models are predicting too much warming for the 21st century.