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Bwyanfwanigan t1_j9y7fn4 wrote

Reply to comment by CrustalTrudger in How much do the different factors affect sea level rise? by Natural-Cap4008

Serious question. I've never understood how sea levels measured in the past can be compared to now that we are using satellites. Before satellites was there even a means of measuring global sea level? The same question has bothered me about climate measurements which in the past were not digital and inaccurate. Not a denier, just always wondered about this and never thought to ask.

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CrustalTrudger t1_j9yaht5 wrote

Global networks of tide gauges for the "historical" sea level, which gets us back relatively accurately to at least the late 1800s. There are a variety of geologic records of sea level which we can use to build sea level curves going back well beyond historical periods.

> The same question has bothered me about climate measurements which in the past were not digital and inaccurate

If you want a deep dive on this, starting with something like the 'physical science basis' product of the latest IPCC report would be a good start. The short version is that we can place individual temperature records into context with a vast numbers of proxy data that allow us to reconstruct temperature (e.g., oxygen isotopes, clumped isotopes, compound specific isotopes, tree rings, etc.) and climate modeling that all tell us effectively the same thing.

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racinreaver t1_ja0yw2v wrote

There's actually a lot of work that goes into cross-correlating data between different sorts of satellite measurements and different generations of similar technologies. For correlating to historical data, you can also always keep collecting the same kind of historical data.

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