Comment by gd1 | Hacker News Reader

Comment by gd1 | Hacker News Reader

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I will have one last go at explaining my position, as simply as I can.

I used the word 'unchanged' to indicate that the sea level in the Marshall Islands is unchanged. It is currently approximately where it was 23 years ago. This is a pretty common usage. If a stock trades up and down all day and ends where it started, you will hear people say 'it ended the day unchanged'. Or 'unch'. Sea levels in the Marshall Islands are currently 'unch'. Over a period of 23 years.

And make no mistake, I acknowledge the worldwide trend in sea level is upwards, the evidence of one tidal gauge doesn't trump the evidence of thousands of tidal gauges. And it has been upwards of course this entire interglacial.

Now, your example of a linear trend superimposed on a sinusoid is a good one. So let me say this, it's a pretty fucking pathetic linear trend if, 23 years later, the bottom of the sinusoid is still overlapping the starting point. The noise in the measurement, and the seasonality, is greater than the supposed trend. It's worth considering for example the coastline of Manhattan 100 years ago. This trend you speak of is utterly insignificant on a human timescale. We can literally grow land faster should we so desire. For example, consider the fact that many Pacific islands are growing due to sediment accumulation (http://www.bbc.co.uk/news/10222679), so weak is this trend. And yet, we're expected to sit here and swallow the premise of this article, the concept of 'climate refugees' and compensation...

So, I'll reply to your argument and then make a point about the meta argument.

1:

So either:

you believe that comparing a point-in-time value today to a point-in-time value 23 years ago is a legitimate way to talk about sea levels being 'unchanged' (it's not)

or

you believe that the ~10cm change in the average (over various periods) is a legitimately 'unchanged' mean, in that it lies with, say, a couple standard deviations around the mean and is therefore not indicative of a trend.

The second is a legitimate stance, so I'll respond to it: I'm pretty sure your intuition is misleading you badly here. First, note that the existence of the islands and their habitability depends on the high point, not the average or the current value (okay, that's my intuition at least). The high point in 1992-95 was about 1cm; the high point in 2012-2015 was about 20cm. [I chose those bounds to try to avoid the dip in 1998 that we may be entering again - not sure how to interpret that without more historical data.] Second, they only have about 180cm of leeway, so that's ~1/10th of the way there. On a scale of 0-180, I think a shift of about 20 over 23 years is significant.

Meta point:

The whole reason I initial responded to you was that you were badly failing to argue your point. You wrote a couple posts above "Why then did you explicitly call me out, and call me a crackpot, for not defending that claim? If you agree with it?". Do you not see the difference? I called you a crackpot precisely for not defending it, and just insisting it was true several times despite challenges. It has nothing to do at all with whether I agree with it. (I don't, actually, but as above - that seems to be a difference of interpretation. I would need more data to be confident either way though.)

What are you basing your numbers on? From a quick look at the raw data [1], I see the high point in the 1992-95 timeframe as 13.74cm (early 1995). The high point in 2012-15 was 21.55cm (mid 2012). This is a difference of 7.81cm. The standard deviation among yearly high points is 5.62cm across all years, so this is not even close to being a significant change. If you look at the top 5 yearly high points starting with the largest, they occurred in 2007 (26.76cm), 2011 (21.79cm), 2012 (21.55cm), 2010 (18.56cm), and 2014 (18.24cm). Note the 2014 value is over 8cm less than the one in 2007.

Look, I get that living right at sea level isn't exactly ideal, and these people might need help. But let's not make more of this than there is.

EDIT: Also note the big difference in granularity across years. Most complete years had 36-37 measurements. 1992 only had 2 and 1995 had only 31. Thus it's quite possible (even likely) that timeframe's real high point was considerably higher than what is recorded.

[1] http://sealevel.colorado.edu/cgi-bin/table.cgi?q=content%2Fi...

Ah, I didn't see that there was a table. I was eyeballing it and did a pretty bad job. I meant to go up to that peak a bit after the 94 marker. Not the point really, though. The point is that there's a visibly larger difference in the first few years compared to the last one, if we ignore one giant dip in each, which seems as though they're an external effect. But I really don't have a strong stance about the interpretation except to say that 'you can read it in multiple ways depending on how you do it'.

This seems to be quite a change from calling gd1 a crackpot simply because his or her interpretation differs from yours.

I never did that. I called him a crackpot because his defense of his opinion was insisting that it was true, switching datasets, and avoiding challenges. Those are crackpot behaviors. I invited him to do a better job defending his point. Haven't I explained that enough times by now?

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