The sea level rise

  • Thread starter Andre
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  • #1
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There is a new paper about it, the results of the measurements of the GRACE satellites on the sea level changes.

http://sciences.blogs.liberation.fr/home/files/Cazenave_et_al_GPC_2008.pdf [Broken]

Good news.

From the IPCC 4th Assessment Report published in 2007, ocean thermal expansion contributed by ∼50% to the 3.1 mm/yr observed global mean sea level rise during the 1993–2003 decade, the remaining rate of rise being essentially explained by shrinking of land ice. Recently published results suggest that since about 2003, ocean thermal expansion change, based on the newly deployed Argo system, is showing a plateau while sea level is still rising, although at a reduced rate (∼2.5 mm/yr).
 
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  • #2
Xnn
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Very interesting.

If ocean thermal expansion has slowed, then that would mean it is not absorbing as much heat as it was previously. So, where is the heat going?

An interesting calculation would be to determine how much sea level would rise for a BTU going into thermal expansion compared to melting land based ice.
 
  • #3
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Very interesting.

If ocean thermal expansion has slowed, then that would mean it is not absorbing as much heat as it was previously. So, where is the heat going?
Yes, very interesting Andre. My first thought of 'where is the heat going?' was due to an increase in tidal deep-ocean overturning i.e. mixing with colder bottom waters. I have yet to read the report in full though.
 
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  • #4
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There is a new paper about it, the results of the measurements of the GRACE satellites on the sea level changes.

http://sciences.blogs.liberation.fr/home/files/Cazenave_et_al_GPC_2008.pdf [Broken]

Good news.
Why good news??

Afterall, the sea level is still rising.
 
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  • #5
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This seems a bit at odds with 'global warming science/theory' surely the rise should be accelerating? CO2 has increased year on year surely?

Measuring the rise might not be an accurate method of measurung temperatue though, it depends on the shape of the container (amongst other things).

Anyway it's been as cold this winter here as I can remember, it seems more like global cooling around these parts :smile:

I tend to be rather sceptical, measuring one variable in a highly complex system and making huge projections from that seems to be rather a rather poor method of prediction, indeed the expression 'waste of time' springs to mind!!

When you throw in another raft of simiilar predictions/assumptions, well.... I think our would have more success predicting the outcome of the lottery.
 
  • #6
Xnn
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This seems a bit at odds with 'global warming science/theory' surely the rise should be accelerating? CO2 has increased year on year surely?

Part of the problem is that it is very difficult to accurately measure changes in sea level over short periods of time. Afterall, the oceans are not perfectly flat. There are all types of waves along with tides and surges. Storms can also push water around and shifting weather patterns can lower levels in some areas while raising it in others. Land masses can also move up or down and even the continents themselves move a little from plate tectonics.

So, it is possible that the change in the trend is insignificant and instead our measurements are more accurate than before.

http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter5.pdf
 
  • #7
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Part of the problem is that it is very difficult to accurately measure changes in sea level over short periods of time. Afterall, the oceans are not perfectly flat. There are all types of waves along with tides and surges. Storms can also push water around and shifting weather patterns can lower levels in some areas while raising it in others. Land masses can also move up or down and even the continents themselves move a little from plate tectonics.

So, it is possible that the change in the trend is insignificant and instead our measurements are more accurate than before.

http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter5.pdf

Another way of reading that is that 'part of the problem is that most our data is unreliable'.
 
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  • #9
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Don't worry: Milankovitch cycle (earth's tilt, wobble and orbit shape) changes along with sunspot activity levels will insure another ice age soon enough....go get a suntan while you can.
 
  • #10
Gokul43201
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Don't worry: Milankovitch cycle (earth's tilt, wobble and orbit shape) changes along with sunspot activity levels will insure another ice age soon enough....
Really? How soon?
 
  • #11
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Don't worry: Milankovitch cycle (earth's tilt, wobble and orbit shape) changes along with sunspot activity levels will insure another ice age soon enough....

Really? How soon?
I would guess the best way to judge is to look at historical cycles....likely they will repeat for the eight hundred and twenty sixth time (I just made that up I don't know how many recorded cycles have good supporting evidence) again. Somehow earth gets into periods of significant ice and again remerges, without mankind even being present, all on its own...even without high C02 levels.
 
  • #12
mgb_phys
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This seems a bit at odds with 'global warming science/theory' surely the rise should be accelerating? CO2 has increased year on year surely?
It's a complex system as you say, so this rise might have increased mixing and brought colder denser water nearer the surface.

Measuring the rise might not be an accurate method of measurung temperatue though, it depends on the shape of the container (amongst other things).
True but sea level rise is the most worrying effect. A 0.4C change in temperature is not a big deal locally, but even a 1/2m rise in sea level is a big deal for a lot of cities like New York or London.

Anyway it's been as cold this winter here as I can remember, it seems more like global cooling around these parts :smile:
That's why it's better to call it climate change rather than global warming.
Here in the Pacific North West it's likely to mean more snow, a warmer Pacific means more evaporation so more clouds and a 0.4C temperature rise is still going to leave that water falling as snow. But inland, reduced cloud cover could mean colder temperatures for the midwest (only an example - not a detailed model)

I tend to be rather sceptical, measuring one variable in a highly complex system and making huge projections from that seems to be rather a rather poor method of prediction, indeed the expression 'waste of time' springs to mind!!
Dumping a few trillion watts of extra energy into a system is going to have an effect - predicting those effects and how they interact is tricky. But it is going to have an effect.
 
  • #13
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Gokul..thanks for posting:
Physics Forums Guidelines and Privacy Policy
See this thread for writing Math expressions using LaTeX.
Links to useful shortcuts: BB Code, Hotkeys and Smilies

I had not noticed those before.....
 
  • #14
Gokul43201
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I would guess the best way to judge is to look at historical cycles....likely they will repeat for the eight hundred and twenty sixth time (I just made that up I don't know how many recorded cycles have good supporting evidence) again. Somehow earth gets into periods of significant ice and again remerges, without mankind even being present, all on its own...even without high C02 levels.
You still haven't asnwered the question of "how soon?".

Is "soon enough" going to happen over the next few decades or centuries or millenia or many tens of millenia?
 
  • #16
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You still haven't asnwered the question of "how soon?".

Is "soon enough" going to happen over the next few decades or centuries or millenia or many tens of millenia?
Good question. This article explains.
 
  • #17
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Good question. This article explains.
Dissimilarly, this article explains that anthropogenic greenhouse gasses will delay coming ice ages, by something like half a million years.
 
  • #18
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Dissimilarly, this article explains that anthropogenic greenhouse gasses will delay coming ice ages, by something like half a million years.
I actually agree with your article. See my thread starter 'Did AGW Start Thousands of Years Ago?'
 

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