New Kid on the Beach

I’m flattered.

After posting about three different reconstructions of global sea level since 1900, I happened upon another one, this time from Frederikse et al. It’s the latest, and the team of collaborators includes top researchers on this subject, some of whom were involved in previous reconstructions. What flatters me is that it agrees so well with my own reconstruction, better than it agrees other previous efforts. If the new one is the best there is (and it seems to be), then mine is impressively close.

Here’s how mine (in red) compares to that from Frederikse et al. in black:

I’ve offset my own estimates so that we both start from about the same level in the early 20th century. By the year 2018, my estimate shows about 10 mm less sea level rise than theirs, a small fraction of the total rise of around 200 mm (8 inches).

Here they are again, but with their trends estimated by a piecewise linear fit (PLF) with “knots” every 10 years, and I haven’t offset mine, so they don’t plot on top of each other:

And what do they say about the rate of sea level rise? I’ll do as before, and estimate it by two methods: fitting a lowess smooth, and fitting a PLF, both with an inherent time scale of about 10 years. Here’s what the lowess smooth says:

Here’s what the PLF says:

What do we conclude? The most important result, one we noted before in other sea level reconstructions, is that the most recent sea level rise is far faster than what we’ve seen before.

Not that sea level rise hasn’t been fast before. During the 1930s and 1940s, it rose at around 2.5 to 3 mm/yr, about the same rate (maybe more) we saw during the 1990s and 2000s. But during the 2010s, the rate doubled. According to the Frederikse data, it’s now a whopping 5.1-5.2 mm/yr.

Given the new reconstruction and the fact that it seems to be the best yet, I’ll revise my estimate, given in the last post, of how fast sea level is rising right now. I had said 4.5 mm/yr, between 3.5 and 5.5. I’ll now increase that estimate to 5 mm/yr, between 4 and 6.

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