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Comment by piyh | Hacker News Reader

Reducing sunlight to slow warming seems like the most desperate move with unintended consequences. The planet has evolved for billions of years with a constant amount of sunlight. Greenhouse gas sequestering is the most direct reaction to a Greenhouse gas problem.

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Except it hasn't. Solar irradiance has steadily increased over billions of years, and fluctuates regularly with the solar cycle. I'm not saying that this couldn't have unexpected consequences, but you can't start from the premise that solar irradiance has always been constant.

From the perspective of users of solar energy on Earth, wouldn't an increase over billions of years appear constant? My intuition tells me that evolution is much faster than that, and any fluctuations due to solar cycle dynamics would already be mitigated as expected by the same process, if it is indeed so regular.

What I was getting as is that you can't start with a false claim to make a convincing argument. I didn't see what the expected reduction is from the MIT research, but if it falls within known effects of the solar cycle, Milankovitch cycles, and recorded volcanic activity it's less risky than stating that it's a change that the earth has never seen.

Even attempting it is disastrous, either way.

The only winning move is to shut down every attempt at such distraction. We know what we must do. The only thing remaining is to do that.

Not my area of expertise, can you please share reasoning as to why reflecting sunlight is disastrous. also please share evidence that attempting multiple strategies is guaranteed to lead to failure or is even probabilistically worse than only relying on current trends of attempting to decrease co2 emissions

Simple: reflecting sunlight does nothing to remove CO2 from the atmosphere, or to reduce the amount going into the atmosphere. The CO2 is the problem, not the temperature. The temperature is a measure of the CO2 problem. Force the temperature, and it ceases to become an accurate measure.

As CO2 continues to build up, ocean pH decreases, reflecting increasing acidification. As pH decreases, the base of the ocean food chain begins to collapse. When the ocean food chain collapses, the main protein source for much of humanity vanishes. Global war follows, and civilization collapse. Slightly lower temperature is unnoticed.

> The CO2 is the problem, not the temperature.

So all the experts who talk about the 2 degree celsius goal did set the goal on the wrong measure? Please be more convincing than just restating your previous hypothesis.

As far as I understand the situation, the increased average temperature is the problem. Not because every day would be exactly n degrees warmer/hotter, but because it leads to way more variance in the atmosphere, i.e. storms, hot and cold extreme wheather etc. The CO2 itself might also induce problems. But they do not dominate the situation.

Failing to control CO2 leads inexorably to global collapse of civilization, regardless of temperature.

Civilization would also collapse as a consequence of extreme temperature.

Temperature increase is easier to limit, but redirecting resources to limiting temperature accelerates CO2 increase, thus collapse from that.

Directing resources to reducing CO2 also limits temperature rise.

Each dollar directed to intervention A is a dollar not directed to intervention B.

Extreme fever can kill the patient. Plunging the patient in ice water cuts fever, but fails to save the patient. Antibiotics may take longer to reduce fever, but offers the possibility of saving the patient.

But betting everything on one horse, company, or intervention is rarely a good strategy. I think Nicolas Nassim Taleb makes compelling arguments in his books, starting from the Black Swan.

Money is fungible. Money spent on a non-solution is money not spent on a solution.

Higher temperatures is the FIRST and WORST problem. Mitigating the damage already done would be very nice.

We still need the energy transition though.

Higher temperature is unpleasant. Famine kills.

Higher temperatures lead to famine, and also directly to death, and ecosystem collapse.

Solar variation is pretty significant and fast. Milankovitch cycles are upwards of 10% solar radiation change as fast as 5 or 10k years.

https://en.m.wikipedia.org/wiki/Milankovitch_cycles

how long did it take to change in the past though? Seems this would cause the change to occur quickly vs. over millions of years.

10-15 % change in radiation over 10k years is pretty common for earth.

Nuclear winters occur somewhat regularly in earth’s history, usually after a very large volcano erupted but also sometimes after a large asteroid strikes. Unless I’m mistaken the last such natural nuclear winter was after the Pinatubo eruption in 1991, which caused a small but significant global cooling effect of 0.5˚C between 1991 and 1993.

Volcanoes of the same scale happen around every 50 to 100 years, but larger ones with more sever global cooling effects happen every 1000 or so years. Every 50 000 years we can expect a mega-colossal super volcano. The Youngest Toba eruption over 70 kya caused a nuclear winter for over 5 years with an accompanying cooling which lasted possibly for another 1000 years.

Even though these events are natural and happen regularly, they are usually devastating for the life on earth, usually with several species going extinct as a result. There are theories that the Toba eruption almost wiped out all of the human races and created a “bottleneck” in our evolution.

So evidence suggests that a quick dimming event range from being insignificant to catastrophic for the life on earth. There is for sure a reason for caution here.

It also changes with snow cover. More snow means more reflection, meaning cooler temperatures. A reason the Earth spends such long periods in ice ages. We are still coming out of the last one.

The net solar flux hasn't changed. What you are talking about is increased albedo in specific areas. This is lowering solar flux globally. How will this effect agriculture? Plant life? Ocean life in twilight zones?

This is radically dangerous, and is only being proposed because we refuse let extractive industries die or change our lifestyles even slightly.

> "This is radically dangerous, and is only being proposed because we refuse let extractive industries die or change our lifestyles even slightly."

So much exactly this… I hear people talk so much about how intelligent and adaptive humans are, and how we're sure to survive almost anything because of that adaptability and intelligence, but then comes time to change something small to actually adapt to a big deal situation (like climate change for one example among many) and nearly all of humanity bands together to fight against even the tiniest change in how we do things, because apparently "the way it's always been done" is by far the best (even when it's provably wrong or bad). I truly hate humanity at this point because of this (among many other quite valid reasons I won't go into here). The Universe will be a better place when we're all gone.

> The Universe will be a better place when we're all gone.

No, it won't.

That seems on par with claiming global warming is no big deal because the earth has been warmer or cooler at some point in the past. Those billions of years are irrelevant.

Not to mention one of the risks that they mention seems pretty disastrous:

>One of the most serious potential risks of solar geoengineering is termination shock. If we were to use solar geoengineering to suppress global temperatures, but we didn't do anything about CO2 emissions, and if for some reason you were to stop suddenly, all of the solar geoengineering, then those temperatures would suddenly spike back up. And that would mean that human and natural systems had less time to adapt to the new conditions.

So if it works for awhile, and then for some reason stops working, we end up shocking every system on earth. I appreciate that the scientists are hammering "we need more research" but I don't think we are capable of identifying all of the catastrophic failure modes.

I think this argument really suffers from the fact that aerosols from the burning of fossil fuels is currently suppressing the full amount of warming we should be experiencing given the composition of the atmosphere. In other words, we're already masking some of the warming and as we move globally off coal we're going to see warming spike.

Source: https://insideclimatenews.org/news/15092021/global-warming-j...

It sounds like you're making an argument for slowly decreasing the aerosols from fossil fuels, so that we avoid the risk of termination shock, rather than an argument for adding more risk to termination shock by adding space bubbles.

My point is that we will have to do some sort of solar management given the fact that we are currently doing it without even putting any thought into it.

Arguably we are currently experiencing a "termination shock" given the move away from coal and other fossil fuels to clean energy. But honestly I don't even understand what "termination shock" really means. Does it matter if removing aerosols happens over the course of a decade or a century when the rise itself is the issue, not the speed of which it happens. 10 years or 100 years is too soon for any ecosystem or species.

False. Soot increases solar absorption. Cutting coal has multiple desirable effects.

We did do that experiment once before. We grounded the entire US air fleet following 9/11.

https://globalnews.ca/news/2934513/empty-skies-after-911-set...

https://www.wired.com/2002/05/hot-on-the-contrails-of-weathe...

https://edition.cnn.com/2002/TECH/science/08/07/contrails.cl...

https://www.bbc.co.uk/sn/tvradio/programmes/horizon/dimming_...

> NARRATOR: For 15 years Travis had been researching an apparently obscure topic, whether the vapour trails left by aircraft were having a significant effect on the climate. In the aftermath of 9/11 the entire US fleet was grounded, and Travis finally had a chance to find out.

> ...

> DR DAVID TRAVIS: We found that the change in temperature range during those three days was just over one degrees C. And you have to realise that from a layman's perspective that doesn't sound like much, but from a climate perspective that is huge.

> NARRATOR: One degree in just three days no one had ever seen such a big climatic change happen so fast. This was a new kind of climate change. Scientists call it Global Dimming. Two years ago most of them had never even heard of it, yet now they believe it may mean all their predictions about the future of our climate could be wrong. The trail that would lead to the discovery of Global Dimming began 40 years ago, in Israel with the work of a young English immigrant called Gerry Stanhill. A trained biologist, Gerry got a job helping to design irrigation schemes. His task was to measure how strongly the sun shone over Israel.

The thing with contrails (and we can turn it up by running rich) is that we have seen that we can turn this on (and off) relatively fast (days).

Further reading: https://en.wikipedia.org/wiki/Global_dimming

RE "constant amount of sunlight", this is actually untrue. The suns energy output is increasing roughly 10% per billion years. So it's actually never been stronger. It also means that we have much less habitable time on earth than we thought

> 10% per billion years

So it's about 0.000029% more since humans have evolved?

Sea has risen 100 meters in last 20,000 year.

An annual sunlight increase of 0.00000001 % is close enough to "constant" to make no difference. And I didn't even bother with compounding, so the real number is even smaller. It's dwarfed by other solar cycles, and those are dwarfed by the near-doubling of CO2 in our atmosphere.

I'm not automatically against geo-engineering approaches, but we do need to consider them desperate moves compared to the reduction of the GHGs

Indeed. The amount of photosynthesis going on is proportional to inbound sunlight. So you might be able to reduce the temperature of the planet in this way but you will also reduce the amount of photosynthesis happening.

And with less photosynthesis happening, less CO2 is being absorbed from the atmosphere.

Depends where you reduce it though. Theres not a ton of photosynthesis happening in the middle of the REALLY brutal deserts and reducing some sunlight would also reduce the heat and maybe increase plant life and photosynthesis. Thats assuming you can control it that granularly though.

A shield at Langrangian L1 can't be very selective, it would basically shade the whole planet.

If the bubbles can be coated, then the filtered spectrum can be influenced. Eg if 20-300Thz is filtered out, then we only lose heat that’s probably not really useful to plants.

Yes, this would be ideal (although I've rarely seen light measured like that - isn't wavelength almost always used?) If you could have a bandpass filter allowing in ~400-700nm light that would be kind of awesome - definitely a have-your-cake-and-eat-it-too moment. (of course with our luck there will be some process we need that we don't know about that requires the rest of the spectrum too)

Is it? This assumes the the vast majority of plant growth is limited by sunlight, not nutrients, water, or anything else.

Geoengineering in general is a high risk. But one aspect of this form of geoengineering, unlike pumping something into the atmosphere, is that it can be reversed quickly.

> unlike pumping something into the atmosphere, is that it can be reversed quickly

Isn't that a fundamental claim made by those who support pumping sulfur dioxide into the upper atmosphere, however? That if you stop pumping, it quickly degrades and the atmosphere returns to baseline?

No, it means that temperature shoots up even faster than before. Meanwhile, the distraction from fixing the root cause brings disaster earlier.

Solar luminosity goes up 1% every 100 million years roughly.

One of the main claimed benefits is that this is easily reversible, if it goes badly.

If it goes badly, reversing it makes it even worse.

And going badly is guaranteed, because CO2 would continue on up, and the ocean ecosystem would collapse. There are quite dramatic fossil records of such events.

But civilization would collapse first, so there is that.

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