Visitor Put up by Willis Eschenbach
I used to be greeted this morning by a CNN headline saying “Important Atlantic Ocean present system is exhibiting early indicators of collapse, prompting warning from scientists“. YIKES! Be very afraid.
The CNN article opens by saying:
A vital system of ocean currents might already be heading in the right direction to break down, in line with a brand new report, with alarming implications for sea degree rise and world climate — main temperatures to plunge dramatically in some areas and rise in others.
Scary stuff, all proper. It’s referring to a examine in Science journal, Physics-based early warning sign reveals that AMOC is on tipping course.
It’s the resurrection of one other “tipping level” scare. And naturally, regardless of the title, slightly than being “physics-based” this examine is definitely “model-based”. It’s a examine of the Atlantic Meridional Overturning Present (AMOC). Right here’s what the AMOC appears to be like like.
Determine 1. The Atlantic Meridional Overturning Present (AMOC). Purple is floor currents, orange is descending, blue is deep return currents. Graph on the backside reveals the AMOC circulation measured at 26.5°N, in models of Sverdrups (abbreviated “Sv”, 1 Sv = 106 cubic meters per second)
Effectively, really, they do begin out with bodily measurements, viz:
Steady part measurements of the AMOC, out there since 2004 at 26°N from the RAPID-MOCHA array, have proven that the AMOC energy has decreased by a number of Sverdrups (1 Sv = 106 m3 s−1) from 2004 to 2012, and thereafter, it has strengthened once more.
Not talked about is that this enhance within the AMOC energy has continued up till the newest examine in 2018. So in the actual world, there’s no indication of any collapse within the AMOC. There’s no “tipping level” in sight, it’s really barely strengthening … go determine.
So why do they are saying there’s a doable tipping level that might result in a collapse?
A mannequin, after all. On this case, it’s the CESM, the Neighborhood Earth System Mannequin. What they did was to start out up the mannequin, then add modeled freshwater very step by step to the modeled North Atlantic, presumably simulating a melting of the Greenland ice or somesuch which could shut down the AMOC. Right here’s their description:
A quasi-equilibrium method is adopted by including a slowly various freshwater flux anomaly FH within the North Atlantic over the area between latitudes 20°N and 50°N. This freshwater flux anomaly is compensated over the remainder of the area, as proven within the inset of Fig. 1A. We linearly elevated the freshwater flux forcing with a charge of three × 10−4 Sv yr−1 till mannequin yr 2200, the place a most of FH = 0.66 Sv is reached.
And what did they discover? Effectively, they discovered that within the mannequin yr 1,758, which in our phrases is the yr 3782 AD, the AMOC fell off a cliff.
IMPENDING TIPPING POINT CATASTROPHE IN 3782 AD! EVERYONE PANIC!!!
Determine 2. Mannequin outcomes exhibiting AMOC tipping level. Determine 1A from the examine linked above.
Now when you observe my work, you’ll know that I typically ask essentially the most impertinent questions. So I bought to fascinated with one thing they didn’t point out of their examine … simply how a lot modeled recent water have they added?
Set off Warning: the following half includes that dreaded creature “math”, so when you’re allergic to math, simply skip to the final line of the daring part under …
To proceed with the mathiness, when the tipping level occurred in 3782 AD, they have been including 0.527 Sverdrups (“Sv”) of recent water (high scale, Determine 2). Which means on common over your entire interval, they have been including half of that, 0.264 Sverdrups.
Now, a Sverdrup is 1,000,000 cubic meters per second. So over the 1,758 mannequin years from the beginning as much as the tipping level, they’ve added a complete of:
0.264 Sv * 106 cubic meters per second/Sv * 1758 years * 31,556,926 seconds per yr / 109 cubic meters per cubic kilometer =
14,629,305 cubic kilometers of modeled recent water added.
Now, fourteen million cubic kilometers of water, that’s a really massive quantity. So let’s examine it to one thing that’s additionally very massive … say the overall quantity of water in your entire Greenland Ice Cap. Right here’s that comparability.
Determine 3. Comparability of the amount of water contained within the Greenland Ice Cap with the amount of freshwater added to the mannequin from the beginning of the run till the tipping level.
The thoughts boggles … like I stated, tipping is non-compulsory …
Not a lot else left to say about that. I’m reminded of two of Mark Twain’s quotes, viz:
The experiences of my loss of life are drastically exaggerated.
The Mississippi between Cairo and New Orleans was twelve hundred and fifteen miles lengthy 100 and seventy-six years in the past. . . . Its size is just 9 hundred and seventy-three miles at current. …
Within the area of 100 and seventy-six years the Decrease Mississippi has shortened itself 2 hundred and forty-two miles. That’s a median of a trifle over one mile and a 3rd per yr. Due to this fact, any calm particular person, who is just not blind or idiotic, can see that within the Previous Oolitic Silurian Interval, simply 1,000,000 years in the past subsequent November, the Decrease Mississippi River was upwards of 1 million 300 thousand miles lengthy, and caught out over the Gulf of Mexico like a fishing-rod.
And by the identical token any particular person can see that seven hundred and forty-two years from now the decrease Mississippi will probably be solely a mile and three-quarters lengthy, and Cairo and New Orleans can have joined their streets collectively, and be plodding comfortably alongside below a single mayor and a mutual board of aldermen.
There’s something fascinating about science. One will get such wholesale returns of conjecture out of such an insignificant funding of truth.
Right here in our redwood forest house close to the Northern California coast, the enormous storms of the Pineapple Categorical have rolled on by. Torrential rain, gale-force winds. We have been with out energy for 5 days, timber and energy poles down in all places. Our fossil-fueled generator labored like a champ … and after the storm, at this time is sunny. So I climbed onto the roof, cleaned the gutters, and washed the skylights. What’s to not like?
My best possible to all,
As Common: I ask people to cite the precise phrases they’re discussing, it avoids infinite misunderstandings.
My Different, Typically Controversial, Writings: My weblog is “Skating Beneath The Ice: A Journal of Diagonal Parking in a Parallel Universe“. And over on X, aka Twitter, I simply at this time bought my 10,000th follower … @weschenbach for these .
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