Since we have such an active community of armchair oceanographers and spreadsheet Glaciologists here, I thought it would be useful to speak to the real thing, the people who actually spend time on the ocean, on the ice sheets, do the measurements, and come back to share that knowledge with us. I had just that opportunity at the American Geophysical conference in December.
I spoke to Josh Willis, Oceanographer with NASA at the Jet Propulsion Lab – Josh is one of best known young ocean scientists on the planet. He pointed me to the recent Kemp et al study of tidal marshes on the US East coast, which has produced a long record of sea level over the last 2000 years, complete with a very Hockey-stickish uptick during the last 200 or so.
Jason Box of the Byrd Polar Center at Ohio State was there, presenting evidence of acceleration in Greenland ice loss over the last 200 years.
His bottom line – “If we talk 10 years from now, my expectation is that Greenland will be losing roughly double what it is now.”
I round out the video with takes from old pros lead NASA scientist Jim Hansen and Admiral David Titley, the US Navy’s Chief Oceanographer.
For more, see my previous Sea Level video –
Kemp et al – Climate related sea-level variations over the past two millennia
Vermeer, Rahmsdorf -Global Sea Level Linked to Global Temperature
Skeptical Science – Is Sea Level Rise Accelerating?
Skeptical Science – Sea Level Hockey Stick
Real Climate: 2000 Years of Sea Level
Real Climate: Sea Level Rise Accelerating
Potsdam Institute for Climate Impact research – sea level pages
What about the Rahmstorf and Vermeer 2011 or Rahmstorf and Vermeer (2009). Simple clear and concise video.
Please read the papers you link to. According to R&V 2011, it is not possible to make claims for periods shorter than 40 years. Therefore we can’t tell if the sea level rise IS accelerating now.
Maurizio, if you read the caption to Figure 1 in R&V 2011, you see it says “We also show a conservative estimate of 2s uncertainty in the acceleration, which accounts for an autocorrelation of 40% at lag 1 y and uses uniformly weighted data” [my italics]. That’s the reason you cannot say anything for less than 40 years using this computation. It doesn’t consider that the altimetry data we’ve had for the last 18 years or so is vastly superior to anything based on tide gauges.
This altimetry data gives over 3 mm/yr, see
http://sealevel.colorado.edu/content/2011rel3-global-mean-sea-level-time-series-seasonal-signals-removed
The tide gauge data over the 20th century on the other hand (which are much poorer due to geographic sampling effects, but spanning a much longer time) give a “current sealevel trend of about 1.7 mm/y” as mentioned in the Houston and Dean (2011) paper that I’m sure you are familiar with…
…but no, this doesn’t establish that sea level rise has accelerated since last week 😉
See also the discussion in Section 3 in this new paper: http://www.springerlink.com/content/42822h838776m102/
(sorry, paywalled)
For those interested that haven’t seen it yet, this recent paper from the University of Copenhagen really illuminated the big picture for me. It seems that we can certainly make a big difference in the amount of additional sea level rise if we stabilize emissions sooner rather than later.
Abstract:
http://www.glaciology.net/Home/PDFs/Announcements/sealevelprojectionstoad2500withthercpscenarios
Press Release:
http://www.eurekalert.org/pub_releases/2011-10/uoc-slw101711.php
Wow, I just realized that if you put together the projections from the paper I linked above (Jevrejeva, Moore, Grinsted, 2011) with the (Kemp, et al, 2011) graph you get a very pronounced hockey stick.
I wonder how the IPCC AR5 report will feature these two pieces of evidence. Frankly, they together tell me that we have already induced a large jolt to the planet’s system, but there is still time to stabilize emissions and reduce the impact.
Dana1981 – seems that “now” means “as observed during the last 40 years”.
How many years of observation do we need before establishing if the acceleration has changed?
Hint: don’t answer before reading R&V 2011.
Maurizio, hint: don’t answer before reading and understanding R&V 2011 🙂
Thank you Anonymous.
Great stuff. If you want to hear more “straight talk on rising seas in a warming world” from Josh, visit Dot Earth, as well: http://j.mp/dotJosh
Andy Revkin is trolling Joe Romm http://www.youtube.com/watch?v=NJ81cFqYO3k
The Runaway Greenhouse Effect – James Hansen http://climateforce.net/2012/01/11/the-runaway-greenhouse-effect-james-hansen/
Anonymous (2): I’m not the one trying to divine accelerations of sea level rises from one year to the next 🙂
Good, that makes two of us… the point I am making is that over most of the period 1930-today, sea level rise has been roughly constant at 1.7 mm/y, as stated by Houston and Dean (and also evident from older papers by Wöppelman and others). I accept this conclusion as essentially valid, one of the few things that are right in this paper. But, for the period 1993 to today, we see that sea level rise has increased to over 3 mm/y, as witnessed by satellite altimetry, a superior observational technology. This result is solid, our mutual friend Nils-Axel Mörner notwithstanding 😉
So, somewhere along the way, the rate has gone up. And it must have happened not very long before 1993, otherwise you wouldn’t be able to draw a curve with near-zero ‘accleration’ for 1930-today (try it!).
BTW I am ‘Anonymous’… damn WordPress
Martin Vermeer
Exactly what are you trying to do Maurizio? Having seen your “sceptical” contributions in various places over a fair length of time, please could you state, honestly and fully, what your real motivation is?
Yup, I thought it was you Martin Vermeer, if only because you don’t come across as irritating as Rahmstorf (and yes, I’m a master at appearing irritating myself, mostly unwittingly).
What an appropriate family name you have!