Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Saturday, February 27, 2021

Halting the conveyor

The Irish science historian James Burke, best known for his series Connections and The Day the Universe Changed, did a less-well-known two-part documentary in 1991 called After the Warming which -- like all of his productions -- approached the issue at hand from a novel angle.

The subject was anthropogenic climate change, something that back then was hardly the everyday topic of discussion it is now.  Burke has a bit of a theatrical bent, and in After the Warming he takes the point of view of a scientist in the year 2050, looking back to see how humanity ended up where they were by the mid-21st century.

Watching this documentary now, I have to keep reminding myself that everything he says happened after 1991 was a prediction, not a recounting of actual history.  Some of his scenarios were downright prescient, more than one of them down to the year they occurred.  The Iraq War, the catastrophic Atlantic hurricane barrage in 2005, droughts and heat waves in India, East Africa, and Australia -- and the repeated failure of the United States to believe the damn scientists and get on board with addressing the issue.  He was spot-on that the last thing the climatologists themselves would be able to figure out was the effect of climate change on the deep ocean.  He had a few misses -- the drought he predicted for the North American Midwest never happened, nor did the violent repulsion of refugees from Southeast Asia by Australia.  But his batting average still is pretty remarkable.

One feature of climate science he went into detail about, that beforehand was not something your average layperson would probably have known, was the Atlantic Conveyor -- known to scientists as AMOC, the Atlantic Meridional Overturning Circulation.  The Atlantic Conveyor works more or less as follows:

The Gulf Stream, a huge surface current of warm water moving northward along the east coast of North America, evaporates as it moves, and that evaporation does two things; it cools the water, and makes it more saline.  Both have the effect of increasing its density, and just south of Iceland, it reaches the point that it becomes dense enough to sink.  This sinking mechanism is what keeps the Gulf Stream moving, drawing up more warm water from the south, and that northward transport of heat energy is why eastern Canada, western Europe, and Iceland itself are as temperate as they are.  (Consider, for example, that Oslo, Norway and Okhotsk, Siberia are at the same latitude -- 60 degrees North.)

[Image is in the Public Domain courtesy of NASA/Goddard Space Flight Center]

Just about any high school kid, though, has heard about the Gulf Stream, usually in the context of the paths of sailing ships during the European Age of Exploration.  What many people don't know, however, is that if things warm up, leading to the melting of the Greenland Ice Sheets, it will cause a drastic drop in salinity at the north end of the Gulf Stream, making that blob of water too fresh to sink.

The result: the entire Atlantic Conveyor stops in its tracks.  No more transport of heat energy northward, putting eastern Canada and northwestern Europe into the deep freeze.  The heat doesn't just go away, though -- that would break the First Law of Thermodynamics, which is strictly forbidden in most jurisdictions -- it would just cause the south Atlantic to heat up more, boosting temperatures in the southeastern United States and northern South America, and fueling hurricanes the likes of which we've never seen before.

Back in 1991, this was all speculative, based on geological records from the last time something like that happened, on the order of thirteen thousand years ago.  The possibility was far from common knowledge; in fact, I think After the Warming was the first place I ever heard about it.

Well, score yet another one for James Burke.

A paper this week in Proceedings of the National Academy of Science describes research by Johannes Lohmann and Peter Ditlevsen of the University of Copenhagen indicating the that based on current freshwater output from the melting of Arctic ice sheets, that tipping point from "saline-enough-to-sink" to "not" might be too near to do anything about.  "These tipping points have been shown previously in climate models, where meltwater is very slowly introduced into the ocean," Lohmann said, in an interview with Gizmodo.  "In reality, increases in meltwater from Greenland are accelerating and cannot be considered slow."

The authors write -- and despite the usual careful word choice for scientific accuracy's sake, you can't help picking up the urgency behind the words:

Central elements of the climate system are at risk for crossing critical thresholds (so-called tipping points) due to future greenhouse gas emissions, leading to an abrupt transition to a qualitatively different climate with potentially catastrophic consequences...  Using a global ocean model subject to freshwater forcing, we show that a collapse of the Atlantic Meridional Overturning Circulation can indeed be induced even by small-amplitude changes in the forcing, if the rate of change is fast enough.  Identifying the location of critical thresholds in climate subsystems by slowly changing system parameters has been a core focus in assessing risks of abrupt climate change...  The results show that the safe operating space of elements of the Earth system with respect to future emissions might be smaller than previously thought.

The Lohmann and Ditlevsen paper is hardly the first to sound the alarm.  Five years ago, a paper in Nature described a drop in temperature in the north Atlantic that is precisely what Burke warned about.  In that paper, written by a team led by Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research, the authors write, "Using a multi-proxy temperature reconstruction for the AMOC index suggests that the AMOC weakness after 1975 is an unprecedented event in the past millennium (p > 0.99).  Further melting of Greenland in the coming decades could contribute to further weakening of the AMOC."

Once again, the sense of dismay is obvious despite being couched in deliberately cautious science-speak.

Even if the current administration in the United States explicitly says that addressing climate change is one of their top priorities, they're facing an uphill battle.  Baffling though it is to me, we are still engaged in fighting with people who don't even believe climate change exists, who understand science so little they're still at the "it was cold today, so climate change isn't happening" level of understanding.  (To quote Stephen Colbert, "And in other good news, I just ate dinner, so there's no such thing as world hunger.")  Besides outright stupidity (and apparent inability to read and comprehend scientific research), there's the added problem of elected officials being in the pockets of the fossil fuel industry, the money from which gives them a significant incentive for keeping the voting public ignorant about the issues.

Until we hit the tipping point Lohmann and Ditlevsen warn about.  At which point the effects will be obvious.

In other words, until it's too late.

If the Atlantic Conveyor shuts down, the results will no longer be arguable even by climate-change-denying knuckle-draggers like James "Senator Snowball" Inhofe.  The saddest part is that we were warned about this thirty years ago by a science historian in terms a layperson could easily understand, and -- in Burke's own words -- we sat on our hands.

And as with Cassandra, the character from Greek mythology who was blessed with the gift of foresight but cursed to have no one believe what she says, we'll only say, "Okay, I guess Burke and the rest were right all along" as the world's climate systems are collapsing around us.


 Many of us were riveted to the screen last week watching the successful landing of the Mars Rover Perseverance, and it brought to mind the potential for sending a human team to investigate the Red Planet.  The obstacles to overcome are huge; the four-odd-year voyage there and back, requiring a means for producing food, and purifying air and water, that has to be damn near failsafe.

Consider what befell the unfortunate astronaut Mark Watney in the book and movie The Martian, and you'll get an idea of what the crew could face.

Physicist and writer Kate Greene was among a group of people who agreed to participate in a simulation of the experience, not of getting to Mars but of being there.  In a geodesic dome on the slopes of Mauna Loa in Hawaii, Greene and her crewmates stayed for four months in isolation -- dealing with all the problems Martian visitors would run into, not only the aforementioned problems with food, water, and air, but the isolation.  (Let's just say that over that time she got to know the other people in the simulation really well.)

In Once Upon a Time I Lived on Mars: Space, Exploration, and Life on Earth, Greene recounts her experience in the simulation, and tells us what the first manned mission to Mars might really be like.  It makes for wonderful reading -- especially for people like me, who are just fine staying here in comfort on Earth, but are really curious about the experience of living on another world.

If you're an astronomy buff, or just like a great book about someone's real and extraordinary experiences, pick up a copy of Once Upon a Time I Lived on Mars.  You won't regret it.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

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