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Comment by FreeInFlorida | Hacker News Reader

And yet, there has been no increase in the rate of sea level rise for as long as records have been kept.

Here's the sea level data for San Francisco, CA since Abraham Lincoln was President:

https://tidesandcurrents.noaa.gov/sltrends/sltrends_station....

Nice consistent trend going back 167 years. 1.94mm/year, +/- 0.19mm, for as long as we have been keeping records.

There is NO increase in the rate of sea level rise here, or anywhere in the US, that is above long-run trends going back to the start of record keeping. A quick glance at official government data will prove it. In fact, many West Coast stations (as well as Hawaii), show a decrease in sea level, due to continental rebound and volcanic rise.

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No increase in the rate does not mean no increase. Clearly there is an increase. You want a hockey stick? Wait for Greenland to melt. You may well live to see that.

Unless you build your house less than 18 inches above sea level, you will not live long enough to have the long-run trend in sea level rise affect where you live.

Humans have been dealing with and adapting to the natural rate of sea level rise for hundreds of years. Most of Florida, most of Manhattan, almost all of Louisiana, and many, many other highly-populated areas were uninhabitable swampland before we learned to master sea level and the slow, natural rise that has gone on for as long as we have been making scientific measurements.

This panic about rapidly rising seas is nonsense. No Pacific islands have "disappeared" due to sea level rise, nor have any Arctic or Alaskan villages -- those that have seen changes are due to subsidence, not rising seas.

If you want to attribute the 160-year record of slow, steady, 2-3mm/year (2-3cm/decade) natural rise in sea levels to some mysterious factor that has been in place since CO2 levels were below 300, let's hear your theory. Otherwise, there is nothing to be alarmed about.

"I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it."

Here in reality, I actually live on an island. And our 100-yr flood lines just got moved in, meaning 2000 houses that weren't considered at risk of flooding are now having to deal with flood insurance or lack thereof.

Whatever the reason for the change in flood zone lines -- less risk tolerance by the insurers, more accurate mapping, over-development, etc. -- it shouldn't be because of a change in the rate of sea level rise, because there isn't one.

You would still need to change floodlines if the ocean levels are constantly increasing, so I'm not sure what your point is with this post.

Yes, sea levels are constantly rising -- at exactly the same slow, steady, manageable rate they have been rising for as long as we have been measuring them.

Modifying flood insurance coverage maps isn't anything new, either, but any changes being made should not be blamed on an INCREASE in the rate of rise, because there is no INCREASE in the rate of rise.

As far as Greenland goes, this year is beating last year's immense gain in surface ice coverage (just past the middle of summer there), and is on track to do even better than 2016's 5th-biggest-on-record gain in surface ice coverage.

So far this season, Greenland is gaining about 50 gigatons PER DAY in ice -- and the rate of gain is INCREASING.

https://beta.dmi.dk/uploads/tx_dmidatastore/webservice/b/m/s...

https://beta.dmi.dk/en/groenland/maalinger/greenland-ice-she...

You can thank Hurricane Nicole for that, and if you're going to talk about it in specifics, you should also mention that this was a rare positive blip in a long-term trend of melting that goes back for decades.

Looking at the year over year data:

http://www.arctic.noaa.gov/Report-Card/Report-Card-2016/ArtM...

Greenland is losing ice at around 200Gt/year (this is also in your second link). And I don't see where you get the 50Gt/day gains. Unless the graph is lying, it's in Gt/day. Ranging from gains of about 12Gt to losses of about -8Gt over this past year. Quoting your source:

  Over the year, it snows more than it melts, but calving
  of icebergs also adds to the total mass budget of the ice
  sheet. Satellite observations over the last decade show
  that the ice sheet is not in balance. The calving loss is
  greater than the gain from surface mass balance, and
  Greenland is losing mass at about 200 Gt/yr.

It's all fine and dandy to link to data. It certainly makes your post look more legit. But when your links directly contradict your text you should either find other data, or reconsider your stated interpretation.

Greenland usually gains about 350-400 billion tons of ice over the summer, but this year, it gained 550 billion tons and is still gaining.

Temperatures in the center of Greenland's ice sheet never rose above -10C all summer, so it's hard to see how it could have lost any ice. Ice accumulation is nearly two standard deviations above the 1981-2010 mean for the same period, and it is very, very early in the season for such gains.

Both of Greenland's largest glaciers (Jakobshavn and Peterman) are growing at record rates, about 1km/year.

Icepacks and glaciers calve into the sea. That's what they do. It's Nature's way of moving the ice and snow away from the center and back into the ocean. If they didn't, the snowpack/ice would extend to the Equator, which is impossible, or the snowpack would be 5 miles high, which is not the case.

Unless I've misread your link, the 200Gt/year loss is the net between gain from snow and loss from calving. Your claim in your post was that Greenland was gaining 50Gt/day. This was not backed by your link. It literally isn't in there.

If it were true then the chart should show well in excess of 200Gt accumulated for this year so far, and it does not. In September they have so far accumulated 50Gt which is in line with previous years at this point.

Obviously there is an increase - but I think OPs point is that the steady increase has been going on since before we really burned fossil fuels. Wouldn't you expect an increase in the rate if our CO2 production was having a large effect on ocean levels?

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edit: In response to Jtsummers below, since HN thinks posting more than 3 times per day is too quick:

>If the radius of the balloon increases at a constant rate, the volume of the balloon is increasing at a much greater rate (specifically, proportional to the cube of the increase in radius).

Sure, but we're talking about a numerical value which moved ~20cm over the entire measurement time, compared to the balloon which is 1,270,000,000 cm in diameter. The effects that you mentioned are entirely negligible and probably even beyond the resolution of our measurements.

To maintain a constant in a single dimension (sea level), the rate of water volume increase must be increasing.

Consider by way of analogy a balloon. If the radius of the balloon increases at a constant rate, the volume of the balloon is increasing at a much greater rate (specifically, proportional to the cube of the increase in radius).

By reducing the discussion to merely the sea level, we are ignoring the fact that we must add increasingly large amounts of water to the oceans each year to maintain even a linear rate of growth of sea level.

It should also be noted that since the oceans are not in an arbitrarily deep cylinder, as the oceans rise they will also increase in spread (overtaking what is presently land). If the rate of water going into the oceans were constant, we should expect a sub-linear increase in sea level due to this as well.

EDIT: The only way to have both a constant increase in volume and a constant increase in sea level would be if the oceans stopped at their present boundaries and went straight up sheer walls. I rather doubt this is the case.

Click the time next to my post and you can post a reply to my comment directly even if the reply link doesn't appear.

The balloon was strictly meant as an analogy, but it is illustrative and establishes the upper bound on the rate of increase of water volume.

Regardless of that, showing a linear increase in sea level (constant rate) still necessarily implies a non-constant increase in water volume due to the shape of the "container" for the oceans. Our oceans are not bounded by sheer walls, so it must also be increasing in surface area (spread over land). If it is increasing in surface area and still increasing linearly in sea level [0], then the volume is growing at a super-linear rate. That means each year more water is going into the oceans than the prior year (on average, at least).

[0] One measure from San Francisco, of course, is not enough to demonstrate this as there will be lots of local variations due to many factors.

Thanks for the tip - the reply link did appear, but when I tried to submit my message, I got the 'You're posting too fast' page).

I agree with the logic of your statement - it is perfectly sound. My point was that for a large enough balloon and a small enough rate of increase, the effect will "look" linear(e.g. look at the domain [4.1,4.125] of e^x and determine if it is a linear or exponential function), and our instruments (probably) can't even begin to measure for the effects which you propose.

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