Yesterday NASA’s Jet Propulsion Laboratory published “The Anatomy of Glacial Ice Loss.” For the most part it’s an interesting, though not particularly revolutionary, discussion of the various forces that add to and subtract from glacial ice. Nothing wrong with that.
But its authors took the opportunity to insert a poison pill, a little bit of fearmongering, in a video caption:
Did you catch that little trick? “Combined, the two regions also contain enough ice, that if it were to melt all at once, would raise sea levels by nearly 215 feet ….”
Well, yes, but at what rate is the ice from the two regions melting, and at what rate can we, with any confidence, predict they’ll continue to melt, and over what period of time?
There is absolutely no chance of their melting “all at once”—barring, I suppose, Earth’s collision with some enormous asteroid that sends Earth careening into the Sun!
So, how fast is the ice melting?
For Greenland, about 0.1% of its ice mass per decade—1 percent per century.
For Antarctica, about 0.0045% per decade—1% in 2,200 years.
Combined, those contribute to sea-level rise of about 1 mm per year, i.e., 3.94 inches per century.
So, if the actual rate is about 3.94 inches (0.3283 foot) per century, how long would it take to raise sea level by 215 feet? The answer: 215 ft. / 0.3283 ft. per century = 654.889 centuries, or 65,488.9 years.
To be fair, glacial melt from Greenland and Antarctica isn’t the only contributor to sea-level rise. Thermal expansion and other factors also contribute, and some estimates put annual sea-level rise at around 11.81 inches per century, or about 3 times the rate I posited above.
So, let’s redo the calculations. How long, at that rate, would it take to raise sea level by 215 feet? A mere 21,829 years.
Now tell me, if JPL had made that clear, would anyone have taken seriously its saying that this makes “the study and understanding of [the melt in the two glacial regions] … crucial to our near-term adaptability,” or even to “our long term survival”?
No doubt the study is interesting. But it’s certainly not “crucial to our near-term adaptability” or “our long-term survival.”
Is there any reason to think humanity couldn’t survive a 215-foot rise in sea level spread over 21,,829 years, let alone 65,000? And if we define “near-term” as, say, 100 years, or 500, is there any reason to think our “adaptability” would be seriously threatened by 11.81 inches of sea-level rise in a century, let alone 3.94 inches? Or by 4.92 feet in five centuries, let alone 1.64 feet?
And for that matter, what reason have we to think this rate of glacial melt will continue that long into the future? We’re in the midst of a pleasant interglacial period now, but in terms of ice-age cycles, we’re due for the onset of another before long (perhaps in the next few centuries to a millennium?).