counters (u/counters)

counters commented on Earth is warming faster. Scientists are closing in on why (2024) economist.com/science-and... · Posted by u/andsoitis

red75prime · 23 days ago

Yeah, stratospheric seeding is mostly a stopgap measure that needs to be used in conjunction with other geoengineering and political projects that strive to reduce/reverse CO2 emissions.

counters · 23 days ago

And therein arises the "moral hazard" issue. There is a legitimate concern that geoengineering could abate some of the concern over climate change and lead to further delays to reduce GHG emissions. And this is a serious problem because while we might mask global temperature change with these Approaches, they don't help resolve issues like ocean acidification.

counters commented on Earth is warming faster. Scientists are closing in on why (2024) economist.com/science-and... · Posted by u/andsoitis

red75prime · 24 days ago

At least those show that a stratospheric injection doesn't persist for too long. 200 years of heightened volcanic activity was certainly a problem that eventually resolved itself.

counters · 23 days ago

The important, missing detail that breaks down this analogy is that we don't have a reference for a long period of vulcanism while anthropogenic emissions of greenhouse gases continue.

This is where the "termination shock" issue comes in. Given current CO2 emission rates, a 50 year geoengineering strategy would mask an additional 100-125 ppm of CO2 added to the atmosphere. If the geoengineering scheme was suddenly stopped, it's not entirely obvious what the response trajectory would be of the climate system.

counters commented on Earth is warming faster. Scientists are closing in on why (2024) economist.com/science-and... · Posted by u/andsoitis

FloorEgg · 24 days ago

Thank you for this response. Of those that replied to me, yours seems the most balanced and scientific, and I learned the most from. I wish more often people engaged on HN like you have here.

Given your expertise in this, I'm curious what your take is on CO2 capture, not in terms of economic viability, but in terms of climate risk...

For example, if we were to discover a process that removed CO2 from atmosphere and converted it into a product profitably such that there was an economic incentive/positive feedback loop to remove CO2.

My intuition is that if we removed the CO2 too quickly or too much of it we may have unwanted consequences, but if the rate was managed and we slowed down and stopped at a certain equilibrium, would this be a theoretically ideal way to address the problem?

counters · 24 days ago

Some things to consider.

First, what is "too quickly" with reference to CO2 removal from the atmosphere? At present, human civilization emits over 40 gigatons - or 40 trillion kilograms - of CO2 per year. And that increases the atmospheric burden by about 2.5 parts per million per year. So today, before you even start _reducing_ atmospheric CO2, you need to be sucking down at least 40 trillion kilograms of CO2. I struggle to imagine a scenario outside of total science fiction where that would be remotely possible.

Second, the equilibrium climate response to changes in greenhouse gas forcing take on the order of decades or centuries to realize. This is because the dynamics of the climate system are heavily buffered. For example, the ocean acts as a giant heat capacitor that slowly interchanges with the atmosphere. Were you to instantaneously halve the CO2 in the atmosphere, you'd likely see a pretty classic exponential decay in global average temperature (and other more nuanced responses); in the present climate, it's not clear we have already passed specific "tipping points" that would induce that hysteresis I described in the previous comment (in fact - one could read "climate tipping point" as a synonym for dynamical system hysteresis). Theoretically, one could try to "dial in" some particular equilibrium climate state, but it's not obvious over what timescale you'd have to intervene and what the cost of such an intervention would be.

The cool thing is none of this needs to be purely "theoretical." You could simulate all of this _today_ if you had a setup to run a global climate model. A "4X CO2" experiment where you branch from an equilibrium spin-up climate state and immediately apply a global quadrupling of CO2 has been a completely standard experiment as part of CMIP for over two decades. The opposite experiment is an established protocol for both the Carbon Dioxide Removal Intercomparison Project [1], which features an annual ramp down of CO2 at a 1% per year rate, and the Cloud Feedback Model Intercomparison Project [2], which features a more direct counterpart, with an abrupt decrease of atmospheric CO2 by 50%. There is a large body of literature discussing the results of these classes of experiments, but this is outside of my primary research focus and I can't turn you to particularly good papers off-hand. But they're easy enough to find.

[1]: https://www.geomar.de/en/cdrmip [2]: https://www.cfmip.org/experiments/cfmip3cmip6

counters commented on Earth is warming faster. Scientists are closing in on why (2024) economist.com/science-and... · Posted by u/andsoitis

rossjudson · 24 days ago

Neil Stephenson is predicting way too much of the future.

Tenses are hard. Again:

Stephenson predicted way too much of the present.

counters · 24 days ago

He has a knack for being scarily prescient. I didn't expect we would seriously be discussing geoengineering in the 2020's (I gave it until at least the early 2030's, given the technical complexity of building the actual delivery system for any planet-scale intervention), but here we are.

counters commented on Earth is warming faster. Scientists are closing in on why (2024) economist.com/science-and... · Posted by u/andsoitis

FloorEgg · 24 days ago

I'm no expert in this subject and I don't have any strong opinions on it. The point of this comment isn't to debate one side or the other.

That said, your comment stands out to me to be self-contradictory and unscientific (by way of being alarmist and not backing up an extraordinary claim ).

> Unknown second order effects

This sounds right.

> Nearest real world success is continuous low volume maritime dispersal which has completely different dispersal dynamics than high-altitude bursts, and the continuous low volume maritime dispersal is non-viable

Since I don't know a lot about this topic I'll take your word for it.

> No way to undo it once done

This doesn't sound quite right, my intuition says more likely "no known way to undo it once done".

> If humans can’t perpetually release aerosols — and I mean perpetually, for the next millions of years — then the global climate “snaps back” violently within weeks

Wait... So, to undo it all we have to do is stop doing it? Doesn't this contradict the statement right before it?

> almost certainly eradicates all known life in the entire universe

This statement makes me suspicious of the credibility of the rest. This is an extraordinary claim and I think deserves way more explanation if you want to convince anyone who doesn't already agree with you. It would be a lot easier to accept "decimates human civilization" than "eradicate all life on earth". Life is extremely resilient.

How exactly would it eradicate all life on earth?

counters · 24 days ago

> Wait... So, to undo it all we have to do is stop doing it? Doesn't this contradict the statement right before it?

It's not quite that simple.

The intuition that you're subtly relying on is the idea that the response or effect of one of these geoengineering treatments is linear. But unfortunately, that's not something you can assume about a dynamical system. In reality, the climate system can undergo certain types of hysteresis where "undoing" the forcing doesn't revert the initial perturbation, because you're suddenly on a different response curve. Probably the most famous example of this in climate dynamics is the way that the ice-albedo effect sets up a hysteresis in the trajectory towards a "snowball Earth" scenario. Apologies for the lack of links/references; Wiki has decent write-ups on this, and it's typically covered in the first chapter of a climate dynamics textbook.

The potential response to suddenly stopping a climate change mitigation strategy has a very well-popularized name: a "termination shock." In fact, Neal Stephenson used exactly this concept in his titular novel on the topic in 2021.

As a climate scientist, my mental model to better understand the risk of termination shocks and unintended consequences boils down to how fast the response of the climate system is. Marine brightening is "less risky" because the meteorological response to these interventions is extremely fast; a cloud-precipitation system will respond on the order of minutes to hours, and unless the intervention continues unabated, it will clean the air quickly, limiting the repsonse. Stratospheric aerosol injection is more complicated, but we have a very good analogue - very large scale volcanic eruptions like Mt Pinatubo. The response to these sorts of events is measured more on the timescale of 2-5 years, although knock-on effects (such as a shift towards more diffuse solar radiation reaching the surface, which has significant effects on terrestrial and oceanic biogeochemistry) could very much persist longer than that - and don't "snap back" nearly as quickly. A continuous, Pinatubo-like intervention would compound and introduce coupled atmosphere/ocean responses that could decade years or longer to fully play out. And that's _in addition_ to the near immediate (1-2 year) response in global average temperature, which would bounce back to most of the pre-intervention level very quickly.

These things are complex. There's a lot we don't know. But, there's also a lot we _do_ know. I would encourage anyone who does not have significant experience in climate dynamics to remain curious and avoid jumping to conclusions based on simple intuition; they're probably wrong.

counters commented on Earth is warming faster. Scientists are closing in on why (2024) economist.com/science-and... · Posted by u/andsoitis

red75prime · 24 days ago

Fortunately, we have volcanoes that were doing it in an uncontrolled manner for a long time. I think we have survived.

counters · 24 days ago

Well, the problem is that what we would need to geoengineer the climate would be equivalent to a continuous, yearly sequence of large volcanic eruptions. So the analogy starts to breakdown, because the handful of examples we have of these sorts of periods with high volcanic activity were actually pretty bad for civilization at the time:

1. 530's-540's Cluster - contemporaneous historical notes over both the far East and Western civilizations clearly illustrate widespread famine due to crop failures, most likely due to the cooling that this period sustained (sometimes called the "Little Antique Ice Age"). The famous Plague of Justinian also occurred in this period, and was likely exacerbated by famine. There's also the Norse "Fimbulwinter" mythos - a period preceding Gotterdamurang - likely inspired by this period.

2. 1250's-1280's Cluster - Suspected to have triggered the "Little Ice Age", and triggered contemporaneous crop failures in both South America and Europe. 1258 is known as one of the "Years Without A Summer."

3. 1808-1815 Tambora Cluster - Culprit behind the even more well-known "Year Without a Summer" in 1816, which produced one the more recent great famines in Western Europe in Switzerland. Agriculture-induced famines led to a wave of civil unrest across Europe.

So yeah - we obviously survived these periods. But I wouldn't exactly cite them as endorsements for any sort of geoengineering activity analogous to vulcanism.

counters commented on The U.S. Is Funding Fewer Grants in Every Area of Science and Medicine nytimes.com/interactive/2... · Posted by u/karakoram

gosub100 · 2 months ago

It can be proved by deduction based on the rate of increase in tuition

counters · 2 months ago

I didn't ask you to prove it. I asked why it wasn't already happening.

counters commented on The U.S. Is Funding Fewer Grants in Every Area of Science and Medicine nytimes.com/interactive/2... · Posted by u/karakoram

counters · 2 months ago

Legitimate question: why don't you think universities already do this? It's not exactly a novel idea.

counters commented on Contrails Map map.contrails.org/... · Posted by u/schaum

reactordev · 2 months ago

Finally some science, ok cool. So we're basing this on the baseline of no contrails what-so-ever. We measure the radiative photons? of the light refracting? through it and see it's long-wave radiation channeling properties scatter it rather than allow it through to relieve the earth's heat?

As for contrails, if they're likely to form in certain areas and not others, what's that coefficient? is it the moisture content? is it the jet fuel mixture? Since you say the Contrails program helps predict when these might occur, is that data being used to alter cruise paths?

It's been 20 years since I was a student at College so forgive me when I ask these questions. My grandfather flew bombers and my father flew fighters so I've known about exhaust and pollution from aircraft for a long time. I know the older aircraft pollute and the contrails from bombers (my grandfather had some stories) were an awful mix of frozen water vapor and diesel exhaust. Modern commercial jets are a lot more efficient.

Any route (with the exception of the SIDS and STARS) is charted across airways to the most direct route possible. Right?

counters · 2 months ago

> Finally some science, ok cool. So we're basing this on the baseline of no contrails what-so-ever. We measure the radiative photons? of the light refracting? through it and see it's long-wave radiation channeling properties scatter it rather than allow it through to relieve the earth's heat?

There are many different avenues you could pursue to estimate this, with different degrees of complexity and they all boil down to a radiative transfer calculation. You could start with an idealized, single-column model using a very simple approximation like a 2-stream approach, crudely parameterizing how a few bulk properties of a cloud in the column would influence the estimate of radiative balance at the top of the atmosphere. Such a model would let you explore a huge variety of factors.

To get more into the world of "real climate", you'd eventually scale up to an atmosphere model with a more complex 3D radiative transfer scheme, probably with more complex cloud microphysical representation and interactions with radiation. This still lets you do idealized experiments.

The next step up, you'd do what the DeepMind and Contrails teams have done, which is to use a standard Earth System Model ("climate model"). That just builds the complexity, and allows you to study realistic scenarios with counterfactuals (e.g. with or without additional contrail formation due to aviation). It's still going to be parameterized in some sense.

Ultimately, we'd look at real-world data top-of-atmosphere radiative estimates, which we conveniently measure from a variety of satellites (CERES would be the most well-known one). The problem is that we can't study the counter-factual very easily in the real world. We get a few isolated cases (like the aviation pause over CONUS after 9/11, or the global decrease in aviation during COVID), but there's so much inherent noise (from weather) that it's hard to infer any causality; you'd likely end up using that climate model from the last part to simulate the counterfactual in a weather scenario nudged to reproduce the real-world observations you have.

This would make a great Masters thesis, or maybe a slice of a PhD, but it's not much more complex than that.

> As for contrails, if they're likely to form in certain areas and not others, what's that coefficient? is it the moisture content? is it the jet fuel mixture? Since you say the Contrails program helps predict when these might occur, is that data being used to alter cruise paths?

It's the ambient thermodynamic and kinematic parameters. Namely, background water vapor and temperature, combined with local kinetic energy in the form of turbulence that you need to drive very local supersaturation. Given those parameters, different distributions of gases and particulates emitted from a jet engine may be more or less effective at nucleating ice - if the conditions are even right to do so.

It's worth pointing out that it's _very_ hard to capture these background conditions in weather models, hence why a major part of the DeepMind/Contrails project have been to use machine learning to try to constrain background circulation patterns most consistent with contrail develop as evidenced by high-resolution remote sensing and imagery. Some of the earliest work they did was to use these types of tools to generate data that allow us to better parameterize contrail formation in numerical weather/climate models, which is why they're able to turn this into a predictive and actionable problem.

Otherwise, there's an 80-year literature on this topic. I encourage you to read it. Kärcher's review paper in Nature in 2018 is a good starting point (https://www.nature.com/articles/s41467-018-04068-0).

> Any route (with the exception of the SIDS and STARS) is charted across airways to the most direct route possible. Right?

I'm not an expert in aviation route planning, but from personal experience I know that many other factors come into play with routing (namely avoiding weather, limiting time spent extremely remote / far away from airport or other infrastructure, traffic / network congestion, etc).

counters commented on Contrails Map map.contrails.org/... · Posted by u/schaum

wolttam · 2 months ago

There is also an immense amount of water vapour being produced by the combustion of a hydrocarbon.

counters · 2 months ago

Sure, but water vapor doesn't spontaneously transition to a liquid and accrete onto surfaces - there needs to be a super-saturation of water vapor, and given the temperatures of jet exhaust, that's not trivial to achieve. However, the super-saturation needed for water vapor to deposit onto surfaces as ice is much lower, hence the preference for ice crystal nucleation.