[hrothgar]

PassedOut, on 2015-March-16, 15:09, said:

C'mon now. Look at the globe.

The huge mass of ice on Antarctica pulls water toward it. Remember gravity? When the Antarctic ice sheets melt, the reduced mass reduces the gravitational pull.

I am pretty sure that sea level rise is higher towards the equator (spinning ellipses and all)

[billw55]

hrothgar, on 2015-March-16, 15:19, said:

I am pretty sure that sea level rise is higher towards the equator (spinning ellipses and all)

Some good data here: NOAA sea level trends

[Daniel1960]

PassedOut, on 2015-March-16, 14:46, said:

Sea level is rising at about 3.2 mm per year; you should have no trouble verifying that for yourself. If sea level had been rising at that rate since 1870, then the sea level in 1870 would have been much lower than actually measured. (I trust you can do those calculations yourself.)

If you know how tide gauges work, you will know that they cannot give readings high above actual water levels (to say nothing of the problems that incorrect readings in that direction would have caused for shipping).

Therefore the overall yearly increase since 1870 must be lower than 3.2 mm.

Therefore, the rise in sea level has accelerated.

That seems like a rather round about way of proving your point. The following shows the conclusions of two separate reports, both showing a long-term increase of ~2.5 mm/year, without any apparent acceleration since at least 1930:

http://www.climateda...SeaLevel-01.gif

[PassedOut]

Daniel1960, on 2015-March-16, 16:16, said:

That seems like a rather round about way of proving your point. The following shows the conclusions of two separate reports, both showing a long-term increase of ~2.5 mm/year, without any apparent acceleration since at least 1930:

http://www.climateda...SeaLevel-01.gif

More compactly then:

2.5 mm/year < 3.2 mm/year

Therefore, the rise in sea level has accelerated.

[hrothgar]

Daniel1960, on 2015-March-16, 16:16, said:

That seems like a rather round about way of proving your point. The following shows the conclusions of two separate reports, both showing a long-term increase of ~2.5 mm/year, without any apparent acceleration since at least 1930:

http://www.climateda...SeaLevel-01.gif

Yo ***** for brains, I'm going to quote from the article I posted a couple hours back since you obviously didn't bother to look at it...
I'm also going to post a really simple summary: You're cherry picking your data, asshole.

Quote

The keystone of the argument by Houston & Dean is the fact that a prominent global sea level reconstruction (Church & White 2006) shows no acceleration since 1930. Which raises the question: why 1930, given the sea level data set starts in 1870? The reason becomes immediately evident when looking at the acceleration starting from any arbitrary date (Fig. 1).


Figure 1. Acceleration of sea-level rise (i.e., twice the quadratic coefficient) from different starting years up to 2001 in the global tide gauge data set of Church and White (2006; red line with uncertainty band). Note that after ~1960 the calculation gets excessively ‘noisy’ because the time interval gets too short to robustly compute acceleration. I graphed this right away after reading the Houston & Dean paper, and a few days later Tamino independently came up with a similar plot – it’s the obvious thing to do. The blue line shows the same quantity from the sea-level hindcast of Vermeer & Rahmstorf (2009) computed from global temperature data.

Around 1930 we see a unique minimum in the acceleration curve – I will explain the cause of this shortly. Other start dates either before or after this minimum show positive acceleration. Picking 1930 for this analysis is thus a classic cherry-pick, and according to the authors that is no accident. They write in the paper: ‘Since the worldwide data of Church and White (2006)…appear to have a linear rise since around 1930, we analyzed the period 1930 to 2010.’ The interval was thus hand-picked to show a linear rise rather than acceleration.
- See more at: http://www.realclima...h.kNFjaebB.dpuf

[Daniel1960]

PassedOut, on 2015-March-16, 16:31, said:

More compactly then:

2.5 mm/year < 3.2 mm/year

Therefore, the rise in sea level has accelerated.

How did you come to that conclusion, if the rate of the tidal gauges did not change over that time period? Secondly, if the rate accelerated from prior to 1930 to afterwards, what caused the acceleration eight decades ago, which is not occurring today?

[Daniel1960]

PassedOut, on 2015-March-16, 16:31, said:

More compactly then:

2.5 mm/year < 3.2 mm/year

Therefore, the rise in sea level has accelerated.

For a more detailed analysis of measuring sea level, you may want to read the following:

http://www.climate.g...lobal-sea-level

From the IPCC graph, the green line shows a SLR of ~1.5 mm/yr from 1900-1930, 3.0 mm/yr from 1930-1960, 1.0 mm/yr from 1960-1990, and 2.5 mm/yr since. The yellow line shows no sea level rise from 1990-1930, a SLR of 3.5 mm/yr from 1930-1960, SLR of 1.0 mm/yr from 1960-1990, and 3.5 mm/yr since. The black line shows the least change, <1.0 mm/yr from 1900-1930, 2.0 mm/yr from 1930-1960, 1.5 mm/yr from 1960-1990, and 2.5 from 1990-present. Unfortunately, I was not able to discern the sources from the IPCC SPM. All three sources show an increase in SLR from the period 1900-1930 or 1960-1990 (IPCC reference period). However, the most recent period (1990-present) shows a similar rise to the earlier period 1930-1960. Whether you consider it an increase, depends on your fram of reference. To state that SLR has been accelerating since 1930 is contradicted by the IPCC graphic.

[PassedOut]

Daniel1960, on 2015-March-17, 05:24, said:

How did you come to that conclusion, if the rate of the tidal gauges did not change over that time period? Secondly, if the rate accelerated from prior to 1930 to afterwards, what caused the acceleration eight decades ago, which is not occurring today?

Sea level rise in the 1870s was about 1 mm/year, and now it is over 3 mm/year. Sea level rise has accelerated, and it is a complete waste of time to argue otherwise.

If someone multiplies two 4-digit numbers and gets a 9-digit result, we can definitely say that the result is wrong, and it is also a complete waste of time to argue otherwise. It is up to the person who did the incorrect calculation to find his or her error. And the learning process will help that person to avoid making similar errors in the future.

I do understand that you have a strong investment in your straight-line model of sea-level rise, but you can't confirm it by selecting just the portion of data that fits your model, while excluding the data that contradicts it. The answers to the questions you are asking can be found by looking at the article Richard linked to, and here: Sea-Level Acceleration Based on U.S. Tide Gauges and Extensions of Previous Global-Gauge Analyses. I have no way of knowing whether you've chosen not to read this material or just don't grasp it, but either way it is up to you to figure out where you are going wrong and to correct it for yourself.

If someone can't grasp that an increase in sea-level rise from 1 mm/year to 3 mm/year represents acceleration, I can't change that. If someone can't grasp that gravity affects the oceans, I can't change that either. No amount of discussion will help.

[Zelandakh]

When I drove out of my garage at 8am this morning I was travelling at 5mph. I drove to work on the motorway and am now approaching a red light at 30mph, breaking down to 20mph with the hope of coming to a stop before the white line. But...omg...I am now driving faster than I was at 8am so I must be accelerating! Help! My brakes are broken!

The point is that both sides of this are cherry-picking. To say that SLR is currently accelerating is not really supported. Nor is it correct to say that there is no increase in the rate of SLR over the longer (1870) time-scale. This sadly seems to have a lot more to do with politics than science. We have enough disinformation in this thread without adding to it.

[Daniel1960]

PassedOut, on 2015-March-17, 08:40, said:

Sea level rise in the 1870s was about 1 mm/year, and now it is over 3 mm/year. Sea level rise has accelerated, and it is a complete waste of time to argue otherwise.

If someone multiplies two 4-digit numbers and gets a 9-digit result, we can definitely say that the result is wrong, and it is also a complete waste of time to argue otherwise. It is up to the person who did the incorrect calculation to find his or her error. And the learning process will help that person to avoid making similar errors in the future.

I do understand that you have a strong investment in your straight-line model of sea-level rise, but you can't confirm it by selecting just the portion of data that fits your model, while excluding the data that contradicts it. The answers to the questions you are asking can be found by looking at the article Richard linked to, and here: Sea-Level Acceleration Based on U.S. Tide Gauges and Extensions of Previous Global-Gauge Analyses. I have no way of knowing whether you've chosen not to read this material or just don't grasp it, but either way it is up to you to figure out where you are going wrong and to correct it for yourself.

If someone can't grasp that an increase in sea-level rise from 1 mm/year to 3 mm/year represents acceleration, I can't change that. If someone can't grasp that gravity affects the oceans, I can't change that either. No amount of discussion will help.

I can see that you are steadfast in your refusal to see the data for what it is, but I will give it one last shot. First off, you are comparing apples to oranges (tidal gauges to satellite measurements). You cannot simple take a method used in 1870 and compare it to a completely different method used today. Second, the tidal gauges show an increase from 1870 to 1930. This shows an acceleration in the past. You can simply say that sea level rise is accelerating today, because it is higher than some time in the distant past, without examining what has occurred since. That is like saying sales of wrist watches are increasing, because more are sold today than in 1870. As shown, sea level rise today is similar to that measured 75 years ago.

I have no "investment" in any straight-line model. Indeed, my last post argues against such. This appears to be lost on you also. Although, even a straight line approach appears to be an improvement over two points, 145 years apart. Selectively choosing your two points, which satisfies your beliefs, and ignoring the rest, is anti-science at best, deliberated misinformation, at worst. Just because the data contradicts your closely-held beliefs, is no reason to exclude it from consideration.

[Daniel1960]

Zelandakh, on 2015-March-17, 11:09, said:

When I drove out of my garage at 8am this morning I was travelling at 5mph. I drove to work on the motorway and am now approaching a red light at 30mph, breaking down to 20mph with the hope of coming to a stop before the white line. But...omg...I am now driving faster than I was at 8am so I must be accelerating! Help! My brakes are broken!

The point is that both sides of this are cherry-picking. To say that SLR is currently accelerating is not really supported. Nor is it correct to say that there is no increase in the rate of SLR over the longer (1870) time-scale. This sadly seems to have a lot more to do with politics than science. We have enough disinformation in this thread without adding to it.

Excellent analogy. While the sea level rise did acelerate from the first measurements in 1870, there appears to be no acceleration today.

[PassedOut]

Daniel1960, on 2015-March-17, 11:31, said:

Excellent analogy. While the sea level rise did acelerate from the first measurements in 1870, there appears to be no acceleration today.

Yes, it is a good analogy, and now we are getting somewhere.

When Zelandakh steps on the gas, his car accelerates. When he steps on the brake, his car decelerates. The changes in speed can be predicted.

If you look at Figure 1 on this paper, you'll see the strong relationship between global temperatures and the changes in the rate of sea level rise. If the earth gets cooler, it's like stepping on the brakes. If the earth gets warmer, it's like stepping on the gas.

Of course there are more factors in play, and scientists are focusing on how to weight them properly. But sea levels are rising faster now because it's warmer than it was in the 1870s. We've stepped on the gas since the 1870s, even though we hit the brakes temporarily during the early 20th century.

If the earth continues to warm, we can expect the yearly increase in sea level to rise also, as it has done. But if we put on the brakes by cutting CO₂ emissions, we can reduce the rate of that increase.

[Al_U_Card]

Meanwhile, in the real (non-analogous) world, is [CO2] causing SLR? Are rising global temps? Is it a short or long-term problem?

A nice example of a century worth of temperature info from a 1000 km circle of the globe.




Hit the brakes...err give it the (greenhouse) gas.... or, well, nevermind...

[Daniel1960]

PassedOut, on 2015-March-17, 12:52, said:

Yes, it is a good analogy, and now we are getting somewhere.

When Zelandakh steps on the gas, his car accelerates. When he steps on the brake, his car decelerates. The changes in speed can be predicted.

If you look at Figure 1 on this paper, you'll see the strong relationship between global temperatures and the changes in the rate of sea level rise. If the earth gets cooler, it's like stepping on the brakes. If the earth gets warmer, it's like stepping on the gas.

Of course there are more factors in play, and scientists are focusing on how to weight them properly. But sea levels are rising faster now because it's warmer than it was in the 1870s. We've stepped on the gas since the 1870s, even though we hit the brakes temporarily during the early 20th century.

If the earth continues to warm, we can expect the yearly increase in sea level to rise also, as it has done. But if we put on the brakes by cutting CO₂ emissions, we can reduce the rate of that increase.

While it is possible that we have hit the brakes only temporarily, we cannot predict that sea level rise will accelerate in the future. SLR is directly related to glacial melt, and less so to ocean temperature. The expanding glaciers in the 19th century resulted in little increase in sea level, and possibly a decrease. Similarly, the expansion in the 1960s and 1970s had a similar effect. The warmer periods resulted in larger glacial melt, and consequently, higher rates of SLR.

So, can we agree that sea level rise has not been constant, has accelerated and decelerated over the measurement period, and is not accelerating currently?

[PassedOut]

Daniel1960, on 2015-March-17, 18:02, said:

While it is possible that we have hit the brakes only temporarily, we cannot predict that sea level rise will accelerate in the future. SLR is directly related to glacial melt, and less so to ocean temperature. The expanding glaciers in the 19th century resulted in little increase in sea level, and possibly a decrease. Similarly, the expansion in the 1960s and 1970s had a similar effect. The warmer periods resulted in larger glacial melt, and consequently, higher rates of SLR.

Sea level rise is half due to melting ice and half due to ocean warming, including 13% from the deepest oceans

Daniel1960, on 2015-March-17, 18:02, said:

So, can we agree that sea level rise has not been constant, has accelerated and decelerated over the measurement period, and is not accelerating currently?

Of course there have been many ups and downs over the years:

Quote

I haven't seen any current data, but considering how hot 2014 was, it seems unlikely to have broken the upward trend. Of course it's possible that Yellowstone will blow and that will do it for sure--but then we'll have other problems...

[Daniel1960]

The warmth in 2014 was mainly calculated to have occurred in the upper ocean. The air and land readings were not so high. This might enhance the thermal expansion portion, but reduce the glacial melt. There was likely no contribution from the polar regions. Annual differences are highly influenced by precipitation also. Look are you graph showing the drop associated with the heavy rain/snow years. Overall, there has been little change in recent years. The sattelite data has been showing the same trend since the beginning.

[PassedOut]

Daniel1960, on 2015-March-17, 18:02, said:

While it is possible that we have hit the brakes only temporarily, we cannot predict that sea level rise will accelerate in the future.

We certainly can. Let's go back to the paper that you referenced to support your own position on the matter: Upper limit for sea level projections by 2100

Quote

Figure 3. Projected global mean sea level rise by 2100 relative to 2000 for the RCP8.5 scenario and uncertainty. Vertical grey bars indicate the 5, 17, 50, 83, and 95th percentiles in the uncertainty distribution.

Even the 5^th percentile bar entails acceleration. And it's looking more and more like the median is a very conservative estimate of sea level rise by the year 2100.

[Al_U_Card]

PassedOut, on 2015-March-18, 07:16, said:

We certainly can. Let's go back to the paper that you referenced to support your own position on the matter: Upper limit for sea level projections by 2100


Even the 5^th percentile bar entails acceleration. And it's looking more and more like the median is a very conservative estimate of sea level rise by the year 2100.

From the abstract of that same paper.

An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise.

It's models all the way down (or up relative to SLR) and demonstrates the relative merit of such studies, RCP8.5 indeed.

[Daniel1960]

I used that paper to show that even those predicting accelration, have not shown acceleration in past sea level rises. Those predictions assume significant contributions from either Greenland if Antarctica. Those predictions are looking less and less likely. For the past 35 years (at least), the rate of sea level rise has been relatively unchanged around 3 mm/yr. Short of a major change, there appears to be no impetus for sea level to rise greater than 250 mm by 2100.

Just because I agree with past
measurements, does not mean I agree with their future predictions. If temperatures do not rise as much as they predict (2°C), then sea level will not approach those values. Currently, neither temperature, nor sea level us rising at their predicted rates. It may at some date in the future.

[PassedOut]

Al_U_Card, on 2015-March-18, 09:19, said:

From the abstract of that same paper.

An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise.

It's models all the way down (or up relative to SLR) and demonstrates the relative merit of such studies, RCP8.5 indeed.

Yes, they are honest about the uncertainties with respect to the upper 5% bar.

The point is, however, that even the lower 5% bar entails acceleration of sea level rise.