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Sea Level in the Year 3000: Why We Should Care

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Sometimes a new scientific result is so clearly important that the bottom line needs no explaining — a report showing how ocean acidification threatens food security around the world, for example, or one that ties melting ice in the Arctic to the threat of colder, snowier winters for the U.S.

But it’s tougher to see why anyone should care about the fact that sea level could rise by 3 and a half feet or higher . . . by the year 3000. Nevertheless, that’s what a study published on Tuesday in Environmental Research Letters says — and it is, believe it or not, an important result.

Here’s why: climate scientists have known for a long time that once you pump heat-trapping carbon dioxide into atmosphere by burning coal and oil, it stays there for a thousand years or more. Even if we reduced emissions to zero as of today, Earth would continue warming, and it would stay warm for many centuries to come.

Figure 3. Committed evolution of global sea-level and its components for the constant composition scenarios explained in the report .
Credit: H Goelzer et al 2012 Environ. Res. Lett.

This obviously isn’t going to happen, which makes the paper purely theoretical. Even so, it’s still a useful exercise to ask what the result would be, since it tells us how much climate disruption we’ve already committed to so far. Any greenhouse-gas emissions we create tomorrow, or next week, or over the next 10 years will be on top of that.

Some climate change is already visible in the form of higher seas, rising temperatures and an increase in droughts, heat waves and torrential rainstorms; more is already guaranteed by the emissions we’ve already created; and more still will come from inevitable future emissions.

And in fact, the scientists also ran simulations showing what future sea level rise will look like if we keep emitting gases over the rest of the century: if we don’t cut back at all, the ocean will eventually rise by about 20 feet, and if we cut back moderately, the number comes in at between 6 and a half and 13 feet.

The other thing that makes this study significant is that it’s the first (the researchers believe, anyway), to take all possible sources of sea level rise into account, including the expansion of ocean water as it warms and the melting of land ice from some 200,000 mountain glaciers as well as the ice caps that cover Greenland and Antarctica., a sea level rise analysis by Climate Central that allows you to navigate an interactive map tool and see areas below different amounts of sea level rise and flooding, down to neighborhood. 

The one drawback, however: ice can get into the sea two ways: by melting or by sliding. The computer model the scientists used in this case doesn’t factor in sliding. Over a thousand years, that makes no difference, since even if the ice didn’t slide at all, it would melt dramatically. Over the short term, however, sliding ice could drive sea level up relatively fast over the next century, even if the ultimate level would eventually end up the same.

With a millennium of lead time, it wouldn’t be such a big deal to rebuild cities further inland and get Earth’s population out of the way of rising seas. If the oceans rise 3 feet by the end of this century, as many scientists now expect, the job is drastically tougher.

Related coverage: 
Sea Level Rise: It Could Be Worse Than We Think 
Trillions at Stake in Sea Level Rise for 20 Global Port Cities 
Greenland Ice Sheet Melt Nearing Critical 'Tipping Point' 
Patagonian Glaciers Are Rapidly Melting, Report Finds  
All the World is a Melting Pot (of Glaciers)

« Climate in Context


By Robert Harmon (St. Augustine, Florida)
on October 2nd, 2012

I am a fairly new resident of Florida. Reading this article made me think of a book I read recently on the ancient, indigenous natives of Florida who were living in the state as far back as 12,000 years ago. Back then at the end of the last ice age so much water was “locked up” in ice that Florida was actually twice the size it is today, with all the other land masses around the world looking different as well. As the ice melted the sea level rose as much as 130 feet, reducing Florida to what it looks like at present. Now, I know the last ice age was a “natural” global phenomenon, but it’s informative to learn the scale of what the planet can do when tipping points are set in motion. To the extent mankind is at all accentuating the rhythms of our planet is dangerous folly.

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By john harkness (minneapolis, mn)
on October 2nd, 2012

I am one who does worry about long-term effects. Perhaps if we had been deeply concerned about long-term effects from the beginning, we would not be in the predicament we are in now. If methane hydrates release quickly, as some say they may/are, it would be very bad for us. But if they release slowly, it will still be very bad for the future of complex life on the planet, since it will extend heating by many millennia at least, and increase the total amount of heating considerably.

So thank you for this post, and no need, imvho, to defend it’s relevance.

OT—Trying to access the Climate Progress website, I get a warning that doing so may harm my computer. If anyone has a way to directly contact Joe Romm, he should be informed about that situation. (And if you could ask him to un-block me form posting there, that would be nice, too ‘-)

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By Daniel Bailey (Northern Michigan)
on October 3rd, 2012

Michael, it’s important to remember the limitations of the study (per internal discussions among the Skeptical Science author community):

1.  The authors hinge their best-case projection from the perspective of the year 2000, with CO2 concentration at what appears to be ~360ppm and following a predicted trend that’s clearly not going to happen; by the year 2012 where we sit the concentration is already off-scale for the “preferred model version,” meaning the “preferred model version” has no demonstrated connection to reality, is in fact demonstrated to be wrong from inception.  Plainly stated, the IPCC concentration scenario employed by the authors in the “preferred model version” was wrong and is useless for these purposes.

2.  Here’s a major problem with the paper - the Antarctic barely responds in the modelling, whereas in the real world Antarctica has shown very dynamic behaviour in every interglacial. The West Antarctic Ice Sheet has essentially disintegrated during interglacials, making it the largest contributor to sea level rise during previous interglacials.

3.  But the biggest problem in the paper is this: 
Uncertainties of the ice sheet projections also arise from poorly constrained physics in prescribing ice-sheet mass balance, basal sliding conditions, and the effects of oceanic erosion of ice shelves and calving fronts. Such limitations are thought to be less crucial for the Greenland ice sheet than for the Antarctic ice sheet, but were not investigated further with the current model setup.” 
The dominant mechanism for mass-loss in marine-terminating outlet glaciers, calving at the terminal front, was not investigated for the WAIS.  Thus, any attempt to use this paper to prosecute a claim of “It won’t be that bad” is simply appalling.

The study is an interesting proof-of-concept modeling exercise, but nothing more.

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By Arno.Arrak (Dix Hills NY 11746)
on October 6th, 2012

Looked up the original by Goelzer et al. article. They used four climate change scenarios: SRES B1, A1B, A2 and one more with constant atmospheric composition from the year 2000 onwards. The last one predicts a sea-level rise of 1.1 meters by the year 3000. The others involve various greenhouse gas stabilization ranges that give sea-level rises anywhere from 2.1 to 6.8 meters. The problem with all those models is the assumption that greenhouse warming from carbon dioxide has anything to do with it. Ferenc Miskolczi used NOAA weather balloon database that goes back to 1948 and discovered that the infrared transmittance of the atmosphere remained constant for 61 years. At the same time atmospheric carbon dioxide increased by 21.6 percent. This means that the addition of all this carbon dioxide to the atmosphere had no effect whatsoever of IR absorption by the atmosphere. And no absorption means no greenhouse effect, case closed. Let me put this differently: the enhanced greenhouse effect, the one alleged to be the cause of global warming, simply does not exist. This is an empirical observation of nature, not derived from any theory, and it overrides any calculations from theory that do not agree with it. Specifically, it overrides all predictions of warming based on the greenhouse effect. As to the extent of future sea level rise, we can use real sea level data to determine it. Chao, Yu, and Li found in 2008 that the existing sea-level rise had been linear for eighty years, with a slope of 2.46 millimeters per year. Something that has been linear that long is not about to change anytime soon. And accordingly we find that satellites today report a sea-level rise of approximately three millimeters per year, within the statistical error of that eighty year trend. Extrapolating this for a century gives us 24.6 centimeters, not twenty feet as Al Gore tells us in his Nobel Prize-winning movie. And for a millennium it becomes 2.46 meters which by chance is somewhere in the middle of their contorted SRES computational results. The other extreme hypotheticals that may involve rebuilding cities inland have no basis in climate science and can safely be ignored. The existing sea level rise is not even enough to present a problem to coral islands because the growth of corals has been able to keep up with it all along.

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By climatehawk1 (Norwich, VT 05055)
on October 7th, 2012

A noble effort, but I doubt most folks (who don’t already think global warming is a serious problem) will get past the headline.  Besides, Hansen and Sato are on record as saying we may get 5 meters of sea level rise this century: .

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