You over-egg this graph with terms like 'real world', 'empirical' and 'incontrovertible'. To any numerate person looking at it it is clear that this graph mixes chalk and cheese. It is obvious when an instrumental record begins by the onset of noise in the signal in 1890.
A numerate person would actually bother to take a closer look at the graph, and find that the “noise” that you think you’re seeing after 1889 is simply depicting the far greater *frequency* of empirical measurements in recent times. Before 1890 we only have estimates of sea level on a one-data-point-per-decade frequency. But since 1890 we have monthly measurements, and since 1993 we have weekly measurements. So that’s not noise at all – those are the actual measurements of sea level: the data isn’t noisy, the ocean is (for example on a daily basis the sea level dramatically rises and falls with the tides on the scale of feet – if we didn’t average that out, the graph would look a whole lot “noisier” than this).
It is also clear from the reduction in noise when a different data set is put on the end around the 1990s.
From 1993 onward we have weekly data points based on a greater number of sea level instruments placed around the globe instead of the monthly data points using fewer instruments around the globe that we have from 1890-1992. This is described in the source papers, but it also makes perfect logical sense: the total global sea level will vary less than any small number of instrument readings which are obviously subject to localized variations in the sea level due to winds, local temperature and rainfall fluctuations affecting mountain drainage, and all manner of other localized factors.
Why did they not include the raw data for what appears before, rather than applying a smoothing filter?
They didn’t “smooth” anything out – that’s the data resolution we have available. They provide all of their source material references here so you can actually learn about this rather than just dreaming up facile arguments based on false assumptions:
Current & Historical Sea Levels Graph
Could it be because the noise level is enormous and they wish to mislead about its accuracy? If we take this at face value, oceanographers are apparently better able to tell what the sea level is when they do not take direct measurements. If so, why do they then corrupt their data by deferring to more direct measurements after 1890?
Again, you’ve misinterpreted the greater data point density for “noise.” Those aren’t error bars, those are empirical data points.
What is even more odd is that there is a pronounced upward trend as soon as the instrumental record begins--an enormous departure from the supposed behaviour of the sea level immediately preceding this and a very bizarre coincidence.
No actually the 1890s were pretty flat, until the turn of the century. Look closer:
And you think it’s “a very bizarre coincidence” that we started making instruments that can precisely measure things like sea level…at the dawn of the industrial age? You realize that scientific instruments are a product of industrialization right?
If we suppose that what occurs in the graph beforehand does indeed bear some relationship to the truth and is not merely guesswork dressed up as science fact
You should try reading the relevant paper about how they determined sea levels from 1890 to 3000 years ago, before suggesting that it’s “guesswork” – here it is:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4801270/pdf/pnas.201517056.pdf
The simplistic answer is that it is due to global warming due to man-made greenhouse gas emissions but in 1890, according to this webpage (CO₂ and other Greenhouse Gas Emissions), global CO2 emissions were only 1.31 billion tonnes whereas in 2015 they were 36.18 billion tonnes--a factor of 27 difference. If 1.31 billion tonnes was already an unsustainable and dangerous level of CO2 production initiating catastrophic sea rise, why are we all still alive now?
So you don’t believe in the global climate crisis…because it hasn’t killed us yet?
Here’s an overlay of global temperature and atmospheric CO2 concentration over the past century – perhaps you can notice a correlation:
Source:
The CO2/Temperature correlation over the 20th Century
On the other hand, if current levels of CO2 production are dangerous and lead to catastrophic sea rise, then that does not seem like it could also have been the reason in 1890, when CO2 production was very much less.
The sea level rise in 1890 was small because CO2 production was small, and today the sea level rise is happening much faster because CO2 production is much larger. How this could seem mysterious to anyone blows my mind – it’s a very simple and direct correlation which you can literally see with your own eyes.
The only obvious conclusion to draw from this graph is that it is inconclusive
You should stop using the word “obvious” because your entire argument about “noise” was entirely false, and therefore all of your conclusions based on that false premise are also false. So it would be more accurate to replace the word “obvious” with the word “wrong” and say:
“The only wrong conclusion to draw from this graph is that it is inconclusive”
as there is no obvious explanation for the behaviour it depicts.
It’s a graph of sea level rise – it doesn’t need to provide an explanation. But when you look for the explanation, it’s all over the internet (if you bother to look): rising global temperatures are being driven by a variety of radiative forcing mechanisms of which atmospheric CO2 concentration is the dominant factor:
Source:
The CO2/Temperature correlation over the 20th Century
There is also likely an awful lot of massaging of data and interpretation gone into its preparation.
“Likely” eh? So it’s
you who are guessing here. These scientists aren’t doing that – they’re making the best measurements possible using the evidence available, which anyone can see by simply reading their papers. If you can do better, then write your own paper so we can have an even more accurate data set (but I’ll forewarn you: every time somebody has come up with better methods for measuring factors like sea level and global temperature and CO2 concentration in the pre-industrial era, they’ve found that the new data set only reinforces our certainty about the on-going global warming and sea level rise crisis).
Regardless of any nitpicking that we may engage in here, the simple fact is that
the sharp upward rise in global sea levels that we see in that chart is an empirical fact, and well above any possible error bars that we might discover through future analyses.