Coastal studies experts: “For coastal management purposes, a [sea level] rise of 7 feet (2 meters) should be utilized for planning major infrastructure”
Front-page NY Times piece on sea level rise gets it mostly right
The New York Times has a splashy front-page story on some of the latest research on sea level rise today. The graphics above make clear the paper gets a big part of the story right — the latest science says we are facing 3-6 feet of sea level rise this century.
Kudos to the NYT for featuring such an important story. Given that serious federal climate action is unlikely for years if not a decade or more, it is more incumbent on the media than ever to explain to the public what’s coming.
The story has its flaws, though. For some reason the media — and many scientists — seem constitutionally incapable of explaining that inaction makes things much worse, that inaction greatly increases the chances of the worst impacts. The NYT has usefully cited the work of Rahmstorf, but somewhat simplified and hence sanitized his graph:
Our current do-nothing or do-little path currently matches the A1F1 scenario (see “U.S. media largely ignores latest warning from climate scientists: “Recent observations confirm … the worst-case IPCC scenario trajectories (or even worse) are being realised” — 1000 ppm“), where the midpoint SLR projection is nearly 5 feet. That’s no surprise since the unrestricted emissions scenario can leads to a staggering warming where the ice is located (see M.I.T. doubles its 2095 warming projection to 10 °F — with 866 ppm and Arctic warming of 20 °F).
So it is a tad frustrating that the NYT buries this crucial point in the final two paragraphs of this long article:
Climate scientists note that while the science of studying ice may be progressing slowly, the world’s emissions of heat-trapping gases are not. They worry that the way things are going, extensive melting of land ice may become inevitable before political leaders find a way to limit the gases, and before scientists even realize such a point of no return has been passed.
“The past clearly shows that sea-level rise is getting faster and faster the warmer it gets,” Dr. Rahmstorf said. “Why should that process stop? If it gets warmer, ice will melt faster.”
The key point is that we are woefully prepared for what is likely to come:
“I think we need immediately to begin thinking about our coastal cities — how are we going to protect them?” said John A. Church, an Australian scientist who is a leading expert on sea level. “We can’t afford to protect everything. We will have to abandon some areas.”
Duh. Triage. It’s coming.
This NYT article give the answer to the question I posed Friday – AGU Climate Q&A Service won’t answer this Q: “Is current U.S. infrastructure adequate for sea level rise?” Is that prudent — or lame?
Key West and Galveston and probably New Orleans appear unsavable on our current emissions path, but what about Miami and Houston? I’ll do a post on that subject later.
What should people plan for? Obviously, it makes no sense to plan for the best case. Most people are highly risk averse and spend a considerable amount of money planning for worst-case scenarios — that’s why they buy fire insurance and catastrophic health insurance. Military and epidemiological planners routinely focus vast amounts of time and money around the worst-case scenarios.
Even if seas only rise, say 4 feet by 2100, then sea levels are likely to be rising 6 inches a decade or more at that point, probably for centuries, so again it makes little sense to plan for, say 2-3 feet of SLR, particularly when making big investments like, say, a new sewage treatment plant (or a major upgrade to an old one), which is going to last a very long time and not going to be easy to move.
As an aside, a 2009 study in Geophysical Research Letters found that “If Greenland’s ice melts at moderate to high rates, ocean circulation by 2100 may shift and cause sea levels off the northeast coast of North America to rise by about 12-20 inches (about 30-50 cm) more than in other coastal areas” (see here).
The NYT article notes:
One of the deans of American coastal studies, Orrin H. Pilkey of Duke University, is advising coastal communities to plan for a rise of at least five feet by 2100.
Since the NYT didn’t include a direct link to that claim or a direct quote, I went looking on Google, which turned up this op-ed piece from last November by Pilkey, “Rising sea levels: a strategy for N.C.“:
I have emailed Pilkey to find out the source of that discrepancy, but for now, I’m going with this as the headline quote.
I have three more issues with the article. First, while the gratuitous quotes from the anti-science disinformers were kept to a minimum, the NYT should at least try to quote disinformers with relevant expertise:
Global warming skeptics, on the other hand, contend that any changes occurring in the ice sheets are probably due to natural climate variability, not to greenhouse gases released by humans…
John R. Christy, a climatologist at the University of Alabama in Huntsville who is often critical of mainstream climate science, said he suspected that the changes in Greenland were linked to this natural variability, and added that he doubted that the pace would accelerate as much as his colleagues feared.
For high predictions of sea-level rise to be correct, “some big chunks of the Greenland ice sheet are going to have to melt, and they’re just not melting that way right now,” Dr. Christy said.
As the link the NYT provides makes clear, Christy has no publications in this area. His ‘expertise’ is in temperature trends and satellite measurements, but even there, how many times one has to be wrong before the media stops quoting you? (see “Should you believe anything John Christy and Roy Spencer say?“).
Second, the NYT asserts:
Certain measurements are so spotty for Antarctica that scientists have not been able to figure out whether the continent is losing or gaining ice.
In fact, while all such measurements have uncertainty, the literature is pretty clear that Antarctica has been losing mass in the past decade — at an accelerating rate, as Skeptical Science explains:
Figure 2 shows the ice mass changes in Antarctica for the period April 2002 to February 2009 (Velicogna 2009) . The blue line/crosses show the unfiltered, monthly values. The red crosses have seasonal variability removed. The green line is the best fitting trend.
Figure 2. Ice mass changes for the Antarctic ice sheet from April 2002 to February 2009. Unfiltered data are blue crosses. Data filtered for the seasonal dependence are red crosses. The best-fitting quadratic trend is shown as the green line (Velicogna 2009).
With the longer time series, a statistically significant trend now emerges. Not only is Antarctica losing land ice, the ice loss is accelerating at a rate of 26 Gigatonnes/yr2 (in other words, every year, the rate of ice loss is increasing by 26 Gigatonnes per year). It turns out that since 2006, East Antarctica has no longer been in mass balance but is in fact, losing ice mass (Chen 2009). This is a surprising result as East Antarctica has been considered stable because the region is so cold. This indicates the East Antarctic ice sheet is more dynamic than previously thought.
This is significant because East Antarctica contains much more ice than West Antarctica. East Antarctica contains enough ice to raise global sea levels by 50-60 metres while West Antarctica would contribute around 6-7 metres. The Antarctic ice sheet plays an important role in the total contribution to sea level. That contribution is continuously and rapidly growing.
I wrote about the Chen paper here (see Satellite data stunner: “Our data suggest that EAST Antarctica is losing mass…. Antarctica may soon be contributing significantly more to global sea-level rise”). The study begins, “Accurate quantification of Antarctic ice-sheet mass balance and its contribution to global sea-level rise remains challenging, because in situ measurements over both space and time are sparse,” and it concludes:
Our results suggest that over the WAIS [West Antarctic ice sheet] (especially the ASE [Amundsen Sea Embayment]) there is accelerated ice loss since around 2005 and/or 2006, with the EAIS showing correlated changes of the same sign in this period, attributed to increased ice loss over EAIS coastal regions in recent years. Using a simple linear projection for the period 2006–2009, Antarctic ice loss rate can be as large as -22089 Gt yr-1. These new GRACE estimates, on average, are consistent with recent InSAR fluxes but, in contrast to previous estimates, they indicate that as a whole, Antarctica may soon be contributing significantly more to global sea-level rise.
Yes, a recent paper has questioned the full magnitude of some of the GRACE ice losses, but many leading experts have in turn questioned that work. I suppose I will have to do a post on that.
Notwithstanding the NYT, the best science says that Antarctica is losing ice, and the ice loss is accelerating.
Third, one of the most puzzling statements in the entire piece is this:
The information problems are even more severe in Antarctica. Much of that continent is colder than Greenland, and its ice sheet is believed to be more stable, over all. But in recent years, parts of the ice sheet have started to flow rapidly, raising the possibility that it will destabilize in the same way that much of the world’s other ice has.
Notwithstanding the phrase “over all,” the WAIS has long been known it to be unstable, as the West Antarctic Ice Sheet Initiative explains at length here. As I wrote in the “high water” part of my book:
Perhaps the most important, and worrisome, fact about the WAIS is that it is fundamentally far less stable than the Greenland ice sheet because most of it is grounded far below sea level. The WAIS rests on bedrock as deep as two kilometers underwater. One 2004 NASA-led study found that most of the glaciers they were studying “flow into floating ice shelves over bedrock up to hundreds of meters deeper than previous estimates, providing exit routes for ice from further inland if ice-sheet collapse is under way.” A 2002 study in Science examined the underwater grounding lines–the points where the ice starts floating. Using satellites, the researchers determined that “bottom melt rates experienced by large outlet glaciers near their grounding lines are far higher than generally assumed.” And that melt rate is positively correlated with ocean temperature.
The warmer it gets, the more unstable WAIS outlet glaciers will become. Since so much of the ice sheet is grounded underwater, rising sea levels may have the effect of lifting the sheets, allowing more-and increasingly warmer-water underneath it, leading to further bottom melting, more ice shelf disintegration, accelerated glacial flow, and further sea level rise, and so on and on, another vicious cycle. The combination of global warming and accelerating sea level rise from Greenland could be the trigger for catastrophic collapse in the WAIS.
And the WAIS Initiative notes:
A final, disturbing extension of West Antarctic collapse is that a substantial portion of the much-larger East Antarctic ice sheet would likely drain through the gap in the Transantarctic Mountains now occupied by the West Antarctic ice sheet. This would only increase the eventual magnitude of the change in sea level, further exacerbating the calamity.
So we have a cascading effect from Greenland to WAIS to EAIS.
For the record, a 2009 study in Science found that sea level rise from a collapse of the WAIS would likely be 25% higher for North America than previously estimated:
The catastrophic increase in sea level, already projected to average between 16 and 17 feet around the world, would be almost 21 feet in such places as Washington, D.C., scientists say, putting it largely underwater. Many coastal areas would be devastated. Much of Southern Florida would disappear.
And the WAIS is already in danger now:
- Nature: “Dynamic thinning of Greenland and Antarctic ice-sheet ocean margins is more sensitive, pervasive, enduring and important than previously realized.”
- Large Antarctic glacier thinning 4 times faster than it was 10 years ago: “Nothing in the natural world is lost at an accelerating exponential rate like this glacier.”
So, yes, we can all hope that humanity somehow quickly becomes smart enough to stay at or below 450 ppm, and then returns to 350 ppm as quickly as possible, keeping overall sea level rise to below 3 feet this century. But prudent planners should plan on 5-7 feet of SLR over the next 100 years.
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