Solar geoengineering thread

AN/AWW-14(V)

AN/AWW-14(V)

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Solar geoengineering — putting aerosols into the atmosphere to reflect sunlight and reduce global warming — is not a fix-all for climate change but it could be one of several tools to manage climate risks. A growing body of research has explored the ability of solar geoengineering to reduce physical climate changes. But much less is known about how solar geoengineering could affect the ecosystem and, particularly, agriculture.

Now, research from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) finds that solar geoengineering may be surprisingly effective in alleviating some of the worst impacts of global warming on crops.

The research, a collaboration with the Norwegian Research Centre and the Bjerknes Centre for Climate Research, the Norwegian University of Science and Technology, the National Center for Atmospheric Research in Boulder, Seoul National University and the Chinese Academy of Sciences, is published in Nature Food.

“Research on solar geoengineering must address whether or not it is effective at reducing human impacts of climate change,” said David Keith, the Professor of Applied Physics at SEAS and Professor of Public Policy at the Harvard Kennedy School. “Our paper helps fill that gap by using the best crop model yet embedded in a climate model to examine the potential impact of solar geoengineering on agricultural yields.”

The team looked at three types of solar geoengineering — stratospheric aerosol injection, marine sky brightening, and cirrus cloud thinning — and their impact on the global yield of maize, sugarcane, wheat, rice, soy and cotton in a business-as-usual future where emissions continue at their current levels.

In such a future, the most effective way to protect crops against the worst effects of global climate change is to reduce the surface temperature. The researchers found that all three potential solar geoengineering methods have a strong cooling effect that would benefit crop yields.

Previous research suggested that cooling temperatures brought on by stratospheric aerosol injection may also lead to less rainfall, which could result in yield loss for rainfed crops. But these studies didn’t look at one of the most important ecological factors in crop transpiration and productivity — humidity.

“Relative humidity or vapor pressure deficit has stronger control on plant water use and crop productivity than precipitation,” said Yuanchao Fan, a Fellow in the Harvard Solar Geoengineering Research Program and first author of the paper. “We found that in a cooler world under multiple scenarios, except cirrus cloud thinning, there will be higher relative humidity, which will alleviate water stress for rainfed crops. Our model shows that the change in precipitation resulting from all three solar geoengineering methods would, in fact, have very little effect on crops.”


The researchers compared how agricultural productivity is affected by solar geoengineering and emissions reductions. The researchers found that while emissions reductions have strong cooling and humidity benefits, they may have a smaller benefit for crop yields than solar geoengineering because the reduction of CO2 fertilization reduces the productivity of most crops compared with solar geoengineering that achieves the same temperature reduction. The finding highlights the need to combine emissions reductions with other tools, including increasing the use of nitrogen fertilization and changes to land use.

“Climate risks cannot be resolved with any single tool; even if emissions were eliminated tomorrow the world’s most vulnerable will still suffer from climate change,” said Keith. “Policymakers need to consider how emissions cuts might be supplemented by specific local adaptations to help farmers reduce the impacts of climate on agriculture, and by global actions such as carbon removal and solar geoengineering.”

Model shows solar geoengineering may be surprisingly effective in alleviating impacts of global warming on crops

Research offers better understanding of solar geoengineering’s effect on agriculture
www.seas.harvard.edu www.seas.harvard.edu
 
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Scientists Say We Need to Look Into Solar Geoengineering Now—Before It’s Too Late

With the pace of emissions reductions looking unlikely to prevent damaging climate change, controversial geoengineering approaches are gaining traction. But aversion to even studying such a drastic option makes it hard to have a sensible conversation, say researchers.

Geoengineering refers to large-scale interventions designed to alter the Earth’s climate system in response to global warming. Some have suggested it may end up being a crucial part of the toolbox for tackling global warming, given that efforts to head off warming by reducing emissions seem well behind schedule.

One major plank of geoengineering is the idea of removing excess CO2 from the atmosphere, either through reforestation or carbon capture technology that will scrub emissions from industrial exhausts or directly from the air. There are limits to nature-based CO2 removal, though, and so-called “negative emissions technology” is a long way from maturity.

The other option is solar geoengineering, which involves deflecting sunlight away from the Earth by boosting the reflectivity of the atmosphere or the planet’s surface. Leading proposals involve injecting tiny particles into the stratosphere, making clouds whiter by spraying sea water into the atmosphere, or thinning out high cirrus clouds that trap heat.

In theory, this could reduce global warming fairly cheaply and quickly, but interfering with the Earth’s climate system carries unpredictable and potentially enormous risks. This has led to widespread opposition to even basic research into the idea. Earlier this year, a test of the approach by Sweden’s space agency was cancelled following concerted opposition.

But this lack of research means policymakers are flying blind when weighing the pros and cons of the approach, researchers write in a series of articles in the latest issue of Science. They outline why research into the approach is necessary and how social science in particular can help us better understand the potential trade-offs.

In an editorial, Edward A. Parson from the University of California, Los Angeles, notes that critics often point to the fact that solar geoengineering is a short-term solution to a long-term problem that is likely to be imperfect and whose effects could be uneven and unjust. More importantly, if solar geoengineering becomes acceptable to use, we may end up over-relying on it and putting less effort into emissions reductions or carbon removal.

This point is often used to argue that solar geoengineering can never be acceptable, and therefore research into it isn’t warranted. But Parson argues that both the potential harms and benefits of solar geoengineering are currently hypothetical due to a lack of research.

Rejecting an activity due to unknown harms might be justified in extreme circumstances and when the alternative is acceptable, he writes. But the alternative to solar geoengineering is potentially catastrophic climate change—unless we drastically ramp up emissions reductions and removals, which is far from a sure thing.

Part of the rationale for preventing solar geoengineering research is that it will drive socio-political lock-in that makes its deployment more likely. But Parson points out that rather than preventing its deployment, blocking research into solar geoengineering may actually lead to less-informed, more dangerous deployments by desperate policymakers further down the line.

One way to overcome some of the resistance to research in this area might be to make the debate around it more constructive, writes David W Keith from Harvard University in a policy paper. And the best way to do that is to disentangle the technical, political, and ethical aspects of the debate.

Appraising the pros and cons of solar geoengineering involves many different fields, from engineering to climate science to economics. But often, experts in one of these areas will give an overall judgment on the technology despite not being in a position to assess critical aspects of it.

Therefore, experts should make sure to disaggregate their judgments into those that are based on their expertise and those that aren’t, says Keith. He also provides a taxonomy of concerns on which expert opinion would be useful, including the physical risks posed by solar geoengineering, the potential that it could be deployed unjustly, the possibility it could be weaponized, and the idea that it could prove a slippery slope to “climate enhancement.”

Making this debate more informed won’t only involve more studies into the technicalities of solar geoengineering. There also needs to be an expansion in social science research to assess what the benefits and drawbacks might be and where they will fall, write the authors of a second policy paper.

While rough estimates put the cost of implementing solar geoengineering at five billion dollars a year, the authors point out that this only covers engineering. Making sound decisions around deployment will also require detailed measures of the physical and socioeconomic impacts of solar geoengineering to assess its benefits and costs, both in different areas and over different timescales.

Unless the world develops a coordinated approach to deploying solar geoengineering, it will also be important to study the options and incentives that will govern the decisions of state or non-state actors to deploy it. This could give insights into the potential triggers for unilateral deployment and what might be done to discourage it.

Whether these calls for more research will be heeded is uncertain, but momentum does seem to be building. And given our lackluster progress on heading off climate change, it may be unwise to take any of our cards off the table.

singularityhub.com

Scientists Say We Need to Look Into Solar Geoengineering Now—Before It's Too Late

Solar geoengineering involves deflecting sunlight away from the Earth by boosting the reflectivity of the atmosphere or the planet’s surface.
singularityhub.com singularityhub.com
 
stratospheric aerosol injection is exciting technology, I think midscale practical experiment (may be one hundred flights of modify KC-135 USAF tanker) is to be start right now
 
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I vote for a spaceborne shield, even if it would be no small feat. Main advantage: it doesn't touch (or wreck) the biosphere proper. In case of dust or small reflectors at a libration point: if something wrong happens, then let them just float away.
 
AN/AWW-14(V) said:
Archibald said:
I vote for a spaceborne shield, even if it would be no small feat.
Click to expand...
It's seems not much easier than colonization of the Moon
Click to expand...
Yes, and? We should have colonized the moon *years* ago. The tech and industrial base that would ahve allowed for luanr colonization, industrialization and economic explotation would make solar shields fairly trivial. Instead of simple mirrors, plop tens of thousands of square kilometers of PV arrays made on and launched from the moon into the Lagrange point between the Earth and the sun. Not only shield Earth from the sun, but convert a small fraction of that deflected sunlight into enough microwave power to allow us to shut off every last environmentally damaging natural gas, coal, wind and hydro power plant.
 
Aerosols need to be off the table for two reasons-acid rain...and the threat of volcanism adding even more to the mix and freezing us out. ONLY space-based answers please. The sun dims-we reflect more light TO Earth, or block same. Unlike fusion, dyson harrop cables might stop another Carrington event. SPSS is a three-fer. The Space Show had a guest on the subject Tuesday.
 
Orionblamblam said:
AN/AWW-14(V) said:
Archibald said:
I vote for a spaceborne shield, even if it would be no small feat.
Click to expand...
It's seems not much easier than colonization of the Moon
Click to expand...
Yes, and? We should have colonized the moon *years* ago. The tech and industrial base that would ahve allowed for luanr colonization, industrialization and economic explotation would make solar shields fairly trivial. Instead of simple mirrors, plop tens of thousands of square kilometers of PV arrays made on and launched from the moon into the Lagrange point between the Earth and the sun. Not only shield Earth from the sun, but convert a small fraction of that deflected sunlight into enough microwave power to allow us to shut off every last environmentally damaging natural gas, coal, wind and hydro power plant.
Click to expand...

Yes. I'm loving it (as would said McDonald).
The Moon is very poor in resources, except
- aluminum
- silicon
- oxygen
(Everything else - REEs, PGMs, He3, Thorium - is a pipe dream.)
These three at least are abundant in the regolith.

All right then, let's work from the three resources above.

Aluminum + silicon = solar arrays

Aluminum + oxygen = SSTLE (Single Stage To Lunar Escape)
- rockets to boost the local solar arrays out of the Moon surface and indeed, to a libration point: either the five Earth-Moon or the five Sun-Earth points.

To me it is the one and only lunar industrialization / resources scheme that makes any sense.
- There are plans for lunar rovers scooping regolith at the front and churning solar arrays at the rear.
- that scheme bring together solar power (for a lunar base), SBSP (Space Based Solar Power, from the Moon to GEO it is slightly easier),and a global warming spaceshield. In a step-by-step approach: solar arrays to SBSP, then SBSP giant structures to the anti-GW spaceborne shield...
 
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Acid rain results from these sprays. Ban aerosols—and you force them to become space advocates.

Same with the medical community and disease research. Force that off world too…at least to contain any lab accidents with surety.
 

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