What’s more, the second graph is not really just from tide gauge data; it’s from tide gauge data inflated by a +0.3 mm/yr GIA “adjustment,” to subtract off the rate by which the sinking ocean floor is hypothesized to reduce sea-level rise.
- Coastal planning and management
- Monitoring global climate change
Correctly estimating historical sea-level rise and representing global ocean heat uptake in climate models are both critical to projecting future climate change and its consequences. The largest uncertainty in projections of sea-level rise up to 2100 is the uncertainty in global mean sea level (GMSL) and thus improving estimates of GMSL rise (as well as regional variations in sea level) remains a high priority.
The fact that they were looking at global change, not local change, is why they allowed for glacial isostatic adjustment, and wrote:
Here, the ongoing response of the Earth to changes in surface loading following the last glacial maximum were removed from the tide-gauge records using the same estimate of glacial isostatic adjustment (GIA; Davis and Mitrovica 1996; Milne et al. 2001) as in our earlier study (Church et al. 2004).
John Church and Neil White know what they are doing. They tested for all sorts of things and added that they even tested for the impact of the changes in dam storage, writing:
We are currently attempting to more thoroughly evaluate the methodology and to improve the reconstruction so that it better represents the variability (Legresy et al., Workshop on Global and Regional Sea Level variability and change, Mallorca, Spain, June 2015).
I recommend these two Mitrovica talks, fascinating and eye opening.