Cartographers kept busy

[An Inspector Calls]

Well if you read the posts on these pages, for which you are an administrator, you'd see that this point (about the sea being deposited on land as excess rain) has been raised and discussed previously, and I have been involved in those discussions.

Do try and keep up.

[kenneal - lagger]

I'll let readers decide if my comments were valid or not in the context of this particular thread, Inspector.

[An Inspector Calls]

lagger,

By all means.

But as to the pathetic allegation that I hadn't read the NASA news item, see here:
http://www.powerswitch.org.uk/forum/vie ... hp?t=18942

But sea level rise is supposed to be accelerating caused by global warming. clv101 can protest all he likes about the complexity of the record (which makes the observation a stupid proxy for global warming in the first place), but it's the CAGW camp that claims that sea level rise is a usable proxy.

http://www.wmo.int/pages/prog/wcrp/docu ... 080221.pdf
(Of course, these people were simply comparing the aggregate! Don't you love the straight line drawn through the last decade's records to prove that sea level rise is accelerating? Just a tad selective of start and end points, perhaps. Used to use that trick at school).

As I pointed out, Nasa says this is a blip, probably is, ( Bandidoz), but it does ruin this man's position:

http://thinkprogress.org/romm/2011/03/1 ... t-by-2050/

So it somewhat weakens the position of sea level as a proxy for global warming. Church's straight line is now ruined!

As for sea dropping because the water has been transferred to the land masses: since sea level's dropped by 6 mm, and the ratio sea:land area is 70:30, that means that the average depth (obviously, now possibly in groundwater) on land is 14 mm in a year. Does that seem plausible to everyone? Doesn't to me. And GRACE is reporting groundwater depletion.

Post dated Fri Aug 26, 2011 9:11 am

As I said, do keep up.

[eatyourveg]

Gosh Inspector, you do have a gift for making friends.

I suggest you contact that charm school first thing tomorrow morning and demand a refund.

[An Inspector Calls]

No need for that, Powerswitch is replete with affable, open-minded role models.

[kenneal - lagger]

I do apologise, Monsieur l'Inspecteur, that I didn't see the other thread but I do have a life and a couple of jobs so I do sometimes miss a thread. All us Administrators have jobs and lives, like most of the posters here, which is why there are quite a few of us to keep an eye on the goings on. I couldn't see where you had made those points in this thread.

I must pick you up on a mathematical point though. The graph in my post shows that sea level rise is increasing at a roughly linear rate, not that it is accelerating. For a graph to show an acceleration with a straight line one of the axes cannot be linear. Speed is in m/sec and acceleration is in m/sec/sec.

The article talks about an accelerating ice mass loss which is perfectly compatible with a linear increase in sea level because the shore line doesn't rise vertically, it slopes or even curves. So, assuming the density of the ice is constant, for every cubic metre of ice lost, more than a cubic metre of water is required to give a linear height increase because the area of the sea is increasing with every millimetre of height increase. Accelerating ice loss could even accompany a deceleration in the rate of sea level rise.

[An Inspector Calls]

I must pick you up on a mathematical point though. The graph in my post shows that sea level rise is increasing at a roughly linear rate, not that it is accelerating. For a graph to show an acceleration with a straight line one of the axes cannot be linear. Speed is in m/sec and acceleration is in m/sec/sec.

I think what you're trying to say is that to show acceleration of sea level rise the linear axis plot of sea level (ordinate) versus time (abscissa) must be supra linear. I would have thought we all knew that.

The article talks about an accelerating ice mass loss which is perfectly compatible with a linear increase in sea level because the shore line doesn't rise vertically, it slopes or even curves. So, assuming the density of the ice is constant, for every cubic metre of ice lost, more than a cubic metre of water is required to give a linear height increase because the area of the sea is increasing with every millimetre of height increase. Accelerating ice loss could even accompany a deceleration in the rate of sea level rise.

Err, yes, that's entirely possible. A good reason, then, not to try and use sea level rise as a proxy for global warming?

Except: for a constant ice melt rate, to lower the observed rate of rise of sea level by just 1 % in a year through ocean area expansion would require an expansion of 1 % during the year. (It's actually slightly more than 1 % as it's an inverse relationship). And you'd have to continue this ocean area increase by the same percentage every year to maintain that observed deceleration of sea level rise. For every ocean area increase, the percentage fall in land area would be about double that compound rate. So the required area of land inundation every year required to modify sea level rise rates is huge; 2 % drop in land area would flood ~3*10^6 sq km of land. I think we'd notice!

[clv101]

It's not really area changes we need to consider. The big factors to take account of are: ocean volume changes due to the elastic and viscous response to mass movement, geoid changes as these mass movements change the distribution of the gravitational field, the steric components of temperature and salinity that change non-uniformly and ocean currents.

The upshot of this is that looking at absolute sea level data from remote sensing platforms or tide gauges is useless without factoring in the above.

[An Inspector Calls]

Agreed.

And presumably melting land ice also plays a part?

Now try pulling that little lot apart to construct a global warming proxy.