Sea Level rise is slowing down! Another failed proxy?

2 As and a B · Post by **2 As and a B** » 07 May 2011, 07:58

biffvernon wrote:Methinks the sea has already risen enough for the Inspector to find himself completely out of his depth.

Inconclusive

An Inspector Calls · Post by **An Inspector Calls** » 07 May 2011, 08:56

clv101 wrote:I don't follow you? The 1.3mm from the ice sheets is based on their mass balance - it is unequivocal that they are losing mass at an accelerating rate. Don't confuse steric sea level rise with eustatic sea level rise.

Why is it "unequivocal that they are losing mass at an accelerating rate"? If they are, then the rate of sea level rise should also trend upwards unequivocally. The graph shows quite the opposite - the sea level rise rate is decelerating. Yes, it's a short period, but then the claims of an observed acceleration are of similar short duration. Yes, it might be La Nina, but since they're 'working on the model' we'll have to wait and see. All in all, sea level rise doesn't seem such a smart proxy for global warming. Those lines drawn through Foodie's graphs are remarkably straight!!

Pepperman: what's
http://denialdepot.blogspot.com/2011/04 ... ature.html
got to do with the price of tea?

biffvernon · Post by **biffvernon** » 07 May 2011, 09:13

Pepperman wrote: It's very well done. The comments are brilliant too.

Poe's Law strikes again.

Post by **clv101** » 07 May 2011, 09:13

An Inspector Calls wrote:
clv101 wrote:I don't follow you? The 1.3mm from the ice sheets is based on their mass balance - it is unequivocal that they are losing mass at an accelerating rate. Don't confuse steric sea level rise with eustatic sea level rise.
Why is it "unequivocal that they are losing mass at an accelerating rate"? If they are, then the rate of sea level rise should also trend upwards unequivocally. The graph shows quite the opposite - the sea level rise rate is decelerating. Yes, it's a short period, but then the claims of an observed acceleration are of similar short duration. Yes, it might be La Nina, but since they're 'working on the model' we'll have to wait and see. All in all, sea level rise doesn't seem such a smart proxy for global warming. Those lines drawn through Foodie's graphs are remarkably straight!!

Two separate points, firstly both ice sheets are losing mass (equivalent to around 1.3mm/y eustatic) at accelerating rates - we know this through three independent measurements techniques of the ice sheets. That makes it unequivocal in my book and the literature.

Secondly, the series you linked to is measurement of sea level, which is affected by a whole bunch of processes (including a eustatic contribution from ice sheets). As I said above, the interannual variability seen correlates with ENSO, with the recent dip related to La Nina. Sea level rise is a fine proxy for temperature - you just need to know that there's a whole lot of other data as well as global average temperature in that series. It's perfectly possible for there to be less ice on land and more water in the sea, and for sea level to be lower from one year to the next.

An Inspector Calls · Post by **An Inspector Calls** » 07 May 2011, 09:20

clv101: both your arguments are circular.

If sea level is a fine proxy for temperature, why did the rate of rise not change in the period 1940-1970, when there was a period of cooling?

I'm not concerned here about observations of the ice sheets - these may, or may not, be melting at increasing/decreasing rates. The case in hand is can sea level rise rate provide a reliable indicator of any changes? Apparently, it can't. I would contend that this will always be the case because the annual melt volumes are so small compared to the volume of the oceans that detecting their bulk signal, let alone any changes in the rates, is immensely dfifficult.

biffvernon · Post by **biffvernon** » 07 May 2011, 12:15

The sea level rise round Japan on March the 11th was an a reliable indicator that Japan had dropped almost a metre.

RenewableCandy · Post by **RenewableCandy** » 07 May 2011, 15:15

RGR's new av is brilliant! D'you think he got the idea when it happened to him

?

vtsnowedin · Post by **vtsnowedin** » 08 May 2011, 00:43

An Inspector Calls wrote:Snip>> I would contend that this will always be the case because the annual melt volumes are so small compared to the volume of the oceans that detecting their bulk signal, let alone any changes in the rates, is immensely dfifficult.

I don't know about that. The ice tied up in Greenland and on Antarctica etc. is a large enough volume to give a considerable rise to sea level if a significant portion were to melt. But your right it is very difficult to measure in anything like real time which is why the extent of sea ice at summer minimums is a useful proxy. Not because floating ice melting causes any rise in sea level but as a massive unbiased thermometer that gives a reading on the adjacent land based glacial ice.

biffvernon · Post by **biffvernon** » 08 May 2011, 08:54

And here's a picture of our big proxy thermometer:

An Inspector Calls · Post by **An Inspector Calls** » 08 May 2011, 09:04

vtsnowedin wrote:
An Inspector Calls wrote:Snip>> I would contend that this will always be the case because the annual melt volumes are so small compared to the volume of the oceans that detecting their bulk signal, let alone any changes in the rates, is immensely dfifficult.
I don't know about that. The ice tied up in Greenland and on Antarctica etc. is a large enough volume to give a considerable rise to sea level if a significant portion were to melt. But your right it is very difficult to measure in anything like real time which is why the extent of sea ice at summer minimums is a useful proxy. Not because floating ice melting causes any rise in sea level but as a massive unbiased thermometer that gives a reading on the adjacent land based glacial ice.

This is a thread about sea level rise and why it's a poor proxy for global temperature.

An Inspector Calls · Post by **An Inspector Calls** » 08 May 2011, 09:11

biffvernon wrote:And here's a picture of our big proxy thermometer:

Of course, there's this one as well:

Post by **clv101** » 08 May 2011, 09:12

An Inspector Calls wrote:This is a thread about sea level rise and why it's a poor proxy for global temperature.

...or more accurately why the inspector mistakenly believes SLR to be a poor proxy.

An Inspector Calls · Post by **An Inspector Calls** » 08 May 2011, 09:23

clv101 wrote:
An Inspector Calls wrote:This is a thread about sea level rise and why it's a poor proxy for global temperature.
...or more accurately why the inspector mistakenly believes SLR to be a poor proxy.

And wherein clv101 has failed to make the case otherwise.

vtsnowedin · Post by **vtsnowedin** » 08 May 2011, 11:40

It was not my intention to drag the thread off topic nor to drag out the much chewed over ice charts. I was merely pointing out the sea level rise ,Or change, will be a lagging indicator not a leading indicator. Long before you can measure a sea level change in Plymouth Harbor, yours or mine, there will be other things that can be measured with some accuracy that will let us monitor and quantify what is happening. Perhaps satellite grid mapping of the elevations of the top of the snow pack across Greenland and Antarctic for example.

biffvernon · Post by **biffvernon** » 08 May 2011, 12:08

vtsnowedin wrote:Perhaps satellite grid mapping of the elevations of the top of the snow pack across Greenland and Antarctic for example.

It's being done. In fact that was the day job I had in mind that the inspector interpreted as running down to the high tide line to measure where exactly it is from day to day.