Talk:Current sea level rise/Archives/2009/3

Melting ice caps lower sea level?

Just thinking out loud here, but since ice is less dense than water, when ice melts the water takes up less space than the ice did. Wouldn't the ice caps melting lower the sea level instead of raise it? —Preceding unsigned comment added by 68.43.151.226 (talk) 22:23, 15 April 2008 (UTC)

Yes for floating sea ice (eg Arctic Ocean). No for land-based icecaps (eg Greenland and Antarctic). Pterre (talk) 00:10, 16 April 2008 (UTC)

Actually I'm thinking out loud too - several complications including long-term isostatic rebound of the land after the weight of the ice has gone, continuing thermal expansion of the melt water, etc. But the main point is climate-related sea-level rise is mainly about land-based ice melting, not about floating ice melting, plus thermal expansion of the water already in the oceans. Pterre (talk) 00:18, 16 April 2008 (UTC)

For floating sea ice, melting is neutral to the sea level, since the part above the surface contributes also. People worry that ice that melts would stop reflecting sunlight, heating the ocean and melting more water. But even if a lot of arctic sea ice melts, that would not raise the sea level. Instead it would increase moisture, which would give more snow over Greenland, adding to its ice cap? The ongoing isostatic rebound in the subarctic areas (Canada, Scandinavia, Russia etc) should raise the sea level elsewhere shouldn't it? --BIL (talk) 08:20, 18 May 2008 (UTC)

Ok, isostatic rebound is a few mm per year over a small part of the ocean, so it should not contribute so much. --BIL (talk) 08:29, 18 May 2008 (UTC)

Melting sea-based ice caps actually cause a net rise in sea levels, but this is rather insignificant and partly due to the associated thermal expansion. ~AH1^(TCU) 18:21, 8 March 2009 (UTC)

Update on science

The issue of sea level rie was the lead topic at the climate congress, based on Stefan Rahmstorf's work. This predicted a rise of approx 1m which seems to be the current 'best guess' (I didn't hear much significant dissent at the meeting). I think the whilst the lead mentions this range, it suggests that this is not the most likely outcome. We should be firmer on the ~1m range.Andrewjlockley (talk) 08:25, 19 March 2009 (UTC)

I removed the addition, for the obvious reason. -Atmoz (talk) 16:43, 19 March 2009 (UTC)

Relaying a complaint

Shows a 10m sea level rise above present in the early Holocene (first part of the second panel)

Data driven plot of sea level rise. Note the x-axis is reversed from the first plot.

A scientist has written to me off-wiki to point out that the first plot at right is partially crap. It shows an approximately +10 m sea level excursion in the last 10 thousand years. No such global event occurred. A few locations near former ice sheets saw multi-meter swings due to crustal relaxation after the ice was removed, but the globe as a whole certainly did not have a large positive excursion. Compare to the second plot, which includes specific data on global sea level change from sites far from ice sheets.

He also complained that as a general matter our discussions on sea level often do a poor job of distinguishing between eustatic (i.e. global) sea level change and local changes due to crustal movement, such as occur in Scandinavia and Denmark. Dragons flight (talk) 00:35, 4 February 2009 (UTC)

Agreed. I've removed it. Its from a WP:RS (ncdc) but doesn't appear to have any info about how it was generated William M. Connolley (talk) 16:35, 4 February 2009 (UTC)

Regarding the distinction between local and eustatic sea level rise, perhaps the article should be moved to 'Current global sea level rise'? Although that's beginning to become quite wordy. It's probably worth making the distinction clearer, though. Martin (Smith609 – Talk) 01:38, 21 March 2009 (UTC)

New predictions

In march 2009, during the Kopenhagen conference, it was stated that the sea level rise would be higher; namely 1 meter by the end of this century. Info from science in action BBC podcoast march 12 2009 —Preceding unsigned comment added by 81.246.167.232 (talk) 11:51, 19 March 2009 (UTC)

2 for 1. I removed the addition, for the same obvious reason as above. -Atmoz (talk) 16:43, 19 March 2009 (UTC)

Stating facts is not a breach of WP:NOT#NEWS. What, therefore is the 'obvious reason'? The current lead suffers badly from being wrong.Andrewjlockley (talk) 08:38, 20 March 2009 (UTC)

It isn't clear that there was a great deal of new science from Copenhagen, or indeed any at all. Certainly, there was no assert that SLR *would* be 1m. Anyway, don't report press froth, certainly not podcasts, unless you enjoy being reverted. Papers, as usual, are welcomed. If you haven't seen the transcript of the closing plenary, it is available via this spam.

However, I do think we should revisit "Values for predicted sea level rise over the course of the next century typically range from 90 to 880 mm, with a central value of 480 mm": Current SLR is ~2-3 mm/yr. 90mm over the next century is absurdly low. And we should probably make it clearer that this "prediction" excludes ice sheet unexpectedness William M. Connolley (talk) 09:14, 20 March 2009 (UTC)

FWIW Rahmstorf's concluding slide said SLR "may well exceed" 1 m by 2100, not a definite statement that it would be 1 m or more. I agree that 90 mm is impossibly low but to my knowledge there's no documented consensus that the value be disregarded. (Anybody know which model came up with 90 mm?) Short Brigade Harvester Boris (talk) 16:33, 20 March 2009 (UTC)

If we're going to talk about ice sheets, I think that this would be a good place for the gravity work discussed at the Global Warming talk page. Although it's new work, calculating gravity, while complex, is pretty unambiguous, so if we can assume they didn't mess up (which I do: the 1st author is really good at this), I think that it would be an additional important consequence of "oops, there goes the ice sheet". Awickert (talk) 18:27, 20 March 2009 (UTC)

As far as I'm concerned, the Rahmstorf work reflects current state of the art. I cited the actual presentation not a secondary source, and I've gone to the climate congress office to ask for the full paper, if it's available. There really isn't any point this article worshipping various sources that are now known to be completely wrong. I'm all for being conservative, but I'd prefer the WP wasn't full of out-of-date science. Our first responsibility is to the truth.Andrewjlockley (talk) 09:56, 21 March 2009 (UTC)

"As far as I'm concerned" isn't good enough; you're not an authority with the recognized stature of IPCC. Short Brigade Harvester Boris (talk) 13:38, 21 March 2009 (UTC)

See WP:TRUTH. Vsmith (talk) 13:58, 21 March 2009 (UTC)

I'm not claiming to be an authority, I'm simply stating that Rahmstorf IS an authority. He was heavily involved in the IPCC process, and is now taking the very sensible step of pointing out that its results were wrong. I know the WP editors just luuuurve IPCC AR4, but sadly it's not actually right in this, and many other aspects.Andrewjlockley (talk) 02:03, 22 March 2009 (UTC)