Lately I’ve been enjoying the EcoModernist Podcast interviews with the founders of ThorCon and Elysium. I’m a fan of Ed Pheil from Elysium industries, as he answered my many questions about his reactor in layman’s terms even I could understand. But ThorcCon is a whole other story. Thorcon make mass produced molten salt reactors (that cannot melt down, as they’re already a liquid) built in shipyards on boats.
They reckon one shipyard could build maybe 20 GW a year of small modular nukes, compared to sometimes taking 5 years to build a 1 GW land reactor! There’s the advantage of mass production, a 100 fold increase in build out speed. The ship just sails into a developing world nation bay somewhere, plugs into the grid for 10 years, and then unplugs for recycling! It’s so weird, because *normally* they’re after the longest lived BIG reactor to deliver power economically. I’ve been listening to discussions about nukes lasting 80 to 100 years! But even with the short-lived block construction of these small modular boat-nukes, and their vastly accelerated life cycles, they’re still going to deliver power cheaper than coal, possibly within 7 years to Indonesia. While they have all the SAFETY of molten salt reactors, they’re not breeder reactors. So cheap little Thorcon boat nukes could then sell their waste to Elysium, who would gladly buy it to burn in their breeder reactors. More on ThorCon and Elysium at Next Big Future.
Long story short — as CO2 adds to ocean acidity, it eats at various carbon deposits already in the oceans and makes the ocean more acidic. If we push it too far, various tiny shelled critters cannot make a strong and thick enough shell to sink to the ocean floor when they die, and will dissolve where they are in the upper oceans, making it more acidic. The geologic record shows a feedback loop that has in the past cascaded out of control and takes tens of thousands of years to recover.
Breaching a “carbon threshold” could lead to mass extinction
Carbon dioxide emissions may trigger a reflex in the carbon cycle, with devastating consequences, study finds.
Jennifer Chu | MIT News Office July 8, 2019
the brain, when neurons fire off electrical signals to their neighbors,
this happens through an “all-or-none” response. The signal only happens
once conditions in the cell breach a certain threshold.
Now an MIT researcher has observed a similar phenomenon in a completely different system: Earth’s carbon cycle.
Daniel Rothman, professor of geophysics and co-director of the Lorenz
Center in MIT’s Department of Earth, Atmospheric and Planetary
Sciences, has found that when the rate at which carbon dioxide enters
the oceans pushes past a certain threshold — whether as the result of a
sudden burst or a slow, steady influx — the Earth may respond with a
runaway cascade of chemical feedbacks, leading to extreme ocean
acidification that dramatically amplifies the effects of the original
This global reflex causes huge changes in the amount of carbon
contained in the Earth’s oceans, and geologists can see evidence of
these changes in layers of sediments preserved over hundreds of millions
Rothman looked through these geologic records and observed that over
the last 540 million years, the ocean’s store of carbon changed
abruptly, then recovered, dozens of times in a fashion similar to the
abrupt nature of a neuron spike. This “excitation” of the carbon cycle
occurred most dramatically near the time of four of the five great mass
extinctions in Earth’s history.
Scientists have attributed various triggers to these events, and they
have assumed that the changes in ocean carbon that followed were
proportional to the initial trigger — for instance, the smaller the
trigger, the smaller the environmental fallout.
But Rothman says that’s not the case. It didn’t matter what initially
caused the events; for roughly half the disruptions in his database,
once they were set in motion, the rate at which carbon increased was
essentially the same. Their characteristic rate is likely a property of
the carbon cycle itself — not the triggers, because different triggers
would operate at different rates.
What does this all have to do with our modern-day climate? Today’s
oceans are absorbing carbon about an order of magnitude faster than the
worst case in the geologic record — the end-Permian extinction. But
humans have only been pumping carbon dioxide into the atmosphere for
hundreds of years, versus the tens of thousands of years or more that it
took for volcanic eruptions or other disturbances to trigger the great
environmental disruptions of the past. Might the modern increase of
carbon be too brief to excite a major disruption?
According to Rothman, today we are “at the precipice of excitation,”
and if it occurs, the resulting spike — as evidenced through ocean
acidification, species die-offs, and more — is likely to be similar to
past global catastrophes.
“Once we’re over the threshold, how we got there may not matter,” says Rothman, who is publishing his results this week in the Proceedings of the National Academy of Sciences. “Once you get over it, you’re dealing with how the Earth works, and it goes on its own ride.”
A carbon feedback
In 2017, Rothman made a dire prediction:
By the end of this century, the planet is likely to reach a critical
threshold, based on the rapid rate at which humans are adding carbon
dioxide to the atmosphere. When we cross that threshold, we are likely
to set in motion a freight train of consequences, potentially
culminating in the Earth’s sixth mass extinction.
Rothman has since sought to better understand this prediction, and
more generally, the way in which the carbon cycle responds once it’s
pushed past a critical threshold. In the new paper, he has developed a
simple mathematical model to represent the carbon cycle in the Earth’s
upper ocean and how it might behave when this threshold is crossed.
Scientists know that when carbon dioxide from the atmosphere
dissolves in seawater, it not only makes the oceans more acidic, but it
also decreases the concentration of carbonate ions. When the carbonate
ion concentration falls below a threshold, shells made of calcium
carbonate dissolve. Organisms that make them fare poorly in such harsh
Shells, in addition to protecting marine life, provide a “ballast
effect,” weighing organisms down and enabling them to sink to the ocean
floor along with detrital organic carbon, effectively removing carbon
dioxide from the upper ocean. But in a world of increasing carbon
dioxide, fewer calcifying organisms should mean less carbon dioxide is
“It’s a positive feedback,” Rothman says. “More carbon dioxide leads
to more carbon dioxide. The question from a mathematical point of view
is, is such a feedback enough to render the system unstable?”
“An inexorable rise”
Rothman captured this positive feedback in his new model, which
comprises two differential equations that describe interactions between
the various chemical constituents in the upper ocean. He then observed
how the model responded as he pumped additional carbon dioxide into the
system, at different rates and amounts.
He found that no matter the rate at which he added carbon dioxide to
an already stable system, the carbon cycle in the upper ocean remained
stable. In response to modest perturbations, the carbon cycle would go
temporarily out of whack and experience a brief period of mild ocean
acidification, but it would always return to its original state rather
than oscillating into a new equilibrium.
When he introduced carbon dioxide at greater rates, he found that
once the levels crossed a critical threshold, the carbon cycle reacted
with a cascade of positive feedbacks that magnified the original
trigger, causing the entire system to spike, in the form of severe ocean
acidification. The system did, eventually, return to equilibrium, after
tens of thousands of years in today’s oceans — an indication that,
despite a violent reaction, the carbon cycle will resume its steady
This pattern matches the geological record, Rothman found. The
characteristic rate exhibited by half his database results from
excitations above, but near, the threshold. Environmental disruptions
associated with mass extinction are outliers — they represent
excitations well beyond the threshold. At least three of those cases may
be related to sustained massive volcanism.
“When you go past a threshold, you get a free kick from the system
responding by itself,” Rothman explains. “The system is on an inexorable
rise. This is what excitability is, and how a neuron works too.”
Although carbon is entering the oceans today at an unprecedented
rate, it is doing so over a geologically brief time. Rothman’s model
predicts that the two effects cancel: Faster rates bring us closer to
the threshold, but shorter durations move us away. Insofar as the
threshold is concerned, the modern world is in roughly the same place it
was during longer periods of massive volcanism.
In other words, if today’s human-induced emissions cross the
threshold and continue beyond it, as Rothman predicts they soon will,
the consequences may be just as severe as what the Earth experienced
during its previous mass extinctions.
“It’s difficult to know how things will end up given what’s happening
today,” Rothman says. “But we’re probably close to a critical
threshold. Any spike would reach its maximum after about 10,000 years.
Hopefully that would give us time to find a solution.”
“We already know that our CO2-emitting actions will have
consequences for many millennia,” says Timothy Lenton, professor of
climate change and earth systems science at the University of Exeter.
“This study suggests those consequences could be much more dramatic than
previously expected. If we push the Earth system too far, then it takes
over and determines its own response — past that point there will be
little we can do about it.”
This research was supported, in part, by NASA and the National Science Foundation.
Nice Aussie hipster video summarising how seaweed can prevent some climate change. 2:32 minutes.
(What they don’t show you is some seaweed farms specialising in bringing it back to biochar, and others would be grown just for carbon farming in the right currents to be cut, let loose, and sucked down and trapped at the bottom of the ocean for thousands of years.)
It’s 2 years old, but I found it quite moving. Climate scientists describe the personal burden of crunching the number themselves, knowing the outcomes, and coping with depression and the abuse from sceptics while living with this knowledge. In the failure of global policy to act, they’re preparing their own families for worst case scenarios, and have backup plans about where they are going to move.
Wow, what a surprise. The Adani corporation have promised that they really truly wuly studied the water impacts on a local desert oasis wetlands. The Queensland government just rolled over and accepted their findings. I mean, Adani hired someone who knew Powerpoint and everything! Due diligence met, apparently. Meanwhile, water scientists have been begging the government not to grant this until further studies have been done. Don’t be surprised if Australia loses another beautiful oasis to our quest for cheap but dirty coal, and probably some oasis-specific species with it. But hey? A big overseas corporation wants to! So I guess we just have to roll over and get on with it…. I mean, this is Australia right? No unreasonable request denied! (PS: Let’s also remember coal isn’t that cheap because you pay for it twice; once as electricity, then again as a public health bill!)