Dating sediments using ragweed and nuclear fallout
The researchers determined the age of each chunk by carbon dating, possible because the sediment is rich in decomposed plant matter. They honed those estimates further by examining the chunks for the first signs of ragweed pollen, which settlers introduced to the area in 1720, and the cesium and lead fallout from atomic bomb testing in the 1950s.
Finally, Horton's team subtracted the annual rate of subsidence from the sea level rise pattern they reconstructed from the sediment samples. That left them with a record of the sea level caused by climate variations.
The technique isn't new, but the new study marks the longest continuous record produced from sediment samples, Horton said.
That understanding of the past will help scientists improve their models of future sea level rise, he said, by allowing them to test models' ability to simulate the known conditions of the past -- a technique known as "hindcasting."
"If you are tuning a model to just the 20th-century data, all you have is sea level rising," Horton said. "It's very hard to tune a model when it's just unidirectional."
Still, that doesn't mean the exact relationship between temperature and sea level rise evident in the salt marsh data will hold as climate change accelerates in the future, Miller cautioned.
The processes that drive the behavior of the world's ice sheets may be different in intensity or type than those that drove melting in the past, he said.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500
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10 Comments
Add CommentHow are they accounting for isostatic rebound and other elevation imapacting tectonic forces that could also effect sea-level? This is a complex interdiscipline area for study. This kind of ea level rise which has been going on since the end of the Ice Age,and which according to this report began accelerating in 1865, which is prior to the time when the large scale industrial use of petroleum became the hallmark of our modern era, so I'll be interested in reading what they think is going on, in all its complexity. Cheers.
Reply | Report Abuse | Link to thisAs a geologist I find this article more agenda driven based on 'science'. I caqn think of a half dozen reasons for the rise of ocean elevation. How do they isolate the rise in a particular location to 'climate change'?
Reply | Report Abuse | Link to thisClimatology continues to lose credibility as does the 'science' journalism of Scientific American.
@Geojelly Roll,
Reply | Report Abuse | Link to thisOK then what factor do you not think was addressed? In the publication of the Proceedings of the National Academies of Science they address such confounds as:
1. Glacial isostatic rebound.
2. Ocean Currents
3. Changes in the gravitational field (due to melting continental ice)
And so forth. Do you know what the "so forth's" are? Did you actually read the article before deciding to condemn the paper? Here is a link to the paper itself. It is a free download.
Climate related sea-level variations over the past two millennia: http://www.pnas.org/content/early/2011/06/13/1015619108.abstract
Want to debate the conclusion and methodology with author of the paper? Go here: 2000 Years of Sea Level (+update)
http://www.realclimate.org/index.php/archives/2011/06/2000-years-of-sea-level/
I look forward to a reasoned critique of the paper. Of course the one of the perquisites of a reasoned critique is that you have read the paper you critiqued.
Now I keep on seeing you claiming to be a geologist. So since you have made your supposed credentials central to the critique it is time that you share with us your peer reviewed work that relates to this topic.
geo has only one intent here, to try to sow the seeds of doubt in sciam readers. Well I doubt he is a geologist or any kind of scientist for that matter. I am more likely to believe he's a paid stooge for the Heritage Foundation. The only thing he forgot to add was that he is cancelling his subscription of ten years in protest. We've heard it all before.
Reply | Report Abuse | Link to thisWhy do you assume that because he has an opposing view to you,that he is a Stooge?
Reply | Report Abuse | Link to thisI am probably part of the conspiracy as well.
In this case it's a fairly well grounded assumption. If he were really a scientist, and really had a beef with what was written on science grounds he would have discussed it in that format rather than being intentionally vague. That's a rhetorical technique, not a dialogue.
Reply | Report Abuse | Link to thisHad he phrased it as simply an opinion without citing his position as a geologist and thereby commenting as an expert people would probably be a bit less suspicious. To put it bluntly, scientists are expected to provide evidence to support their opinions. This person claims to be a scientist and then engages in what amounts to obfuscating commentary. He makes no attempt to verify his credentials, cites no evidence to the contrary, and generally picks apart a paper on the basis of a short blurb about said paper in sciam.com without so much as providing a reason for his dissent that isn't addressed in the paper he apparently didn't read. Trent, asked for clarification and even, quite helpfully, provided the article and access to a venue in which this geologist (Of suspect provenance) could vent his spleen with the source. He is even giving the individual an opportunity to defend his statements. Odd, how he's made no attempt to do so.
Under the circumstances I'd say it's safe to say he's a stooge. Dissent, contrary to your apparent impression, is quite welcome in the sciences. In fact, peer review is part of the process for that very reason. Ideas are supposed to be questioned, but one does need to have reasons beyond just not liking them to back up one's point. Geojellyroll doesn't seem particularly inclined in dialogue or exchanging evidence. Which seems a bit unscientist like to me. I'm rather inclined to be suspicious of him as well under these circumstances.
@ Eboy,
Reply | Report Abuse | Link to thisI am not one for back slapping but that was one eloquent reply.
There is a superb reading list here for the scientifically literate layman
Reply | Report Abuse | Link to thishttp://suzukielders.wordpress.com/2011/06/01/climate-change-evidence-from-the-geological-record/
As a rabid anthropogenic global warming denier, I declare that this article is a load of...gurgle...bloop...glug...
Reply | Report Abuse | Link to thisHead for the hills, folks. The deniers are welcome to stay in the lowlands. Don't worry, we'll help you when the flood comes, but we may be unable to avoid a sardonic grin while doing it.
The East Coast shows no sea rise in a decade, but in fact quite a plunge:
Reply | Report Abuse | Link to thishttp://www.aviso.oceanobs.com/fileadmin/images/news/indic/msl/MSL_Map_J1_Global_IB_RWT_NoGIA_Adjust.png
World tide gauges show utterly no trend change in 150 years:
http://i.min.us/idFxzI.jpg