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Whiter than white: could brightening clouds reduce symptoms of climate change?

Marine cloud brightening: it’s a concept that has been floated in climate engineering discussions for some time. But what are the moral implications of this geoengineering technology, and how likely is…

Brightening and increasing a cloud’s longevity would help reduce the effects of global warming. karindalziel/Flickr

Marine cloud brightening: it’s a concept that has been floated in climate engineering discussions for some time. But what are the moral implications of this geoengineering technology, and how likely is it to be implemented?

What is cloud brightening?

Cloud brightening is the idea that we could increase a cloud’s albedo (reflectivity) to reflect a greater amount of radiation away from the earth, thus producing a cooling effect. This is one of several ideas for geoengineering (climate engineering); a means of reducing the symptoms of climate change.

Cloud brightening involves seeding clouds with a fine spray of saltwater, which encourages cloud micro-droplets to form. Unlike cloud seeding, where large droplets form and produce a rain shower, the droplets in cloud brightening are smaller and remain in the sky as “white cloud”. The micro-droplets scatter incoming radiation, and increase the longevity of the cloud.

Cloud brightening produces micro-droplets that reflect more sunlight. NASA image by Robert Simmon http://earthobservatory.nasa.gov/Features/Aerosols/page4.php

This method would be most effective on clouds over the ocean. Clouds over land already contain small particles of dust and pollution, so the introduction of saltwater aerosol would have little effect.

Cloud brightening falls into the category of geoengineering techniques known as solar radiation management (SRM), together with stratospheric aerosols, space mirrors, and painting roofs white. All of these techniques focus on reducing the amount of radiation reaching the earth’s surface. The other category of geoengineering techniques is carbon dioxide removal (CDR), which involves taking carbon dioxide out of the atmosphere and trapping it in storage.

The cause vs the symptoms

Climate engineering techniques do not address the true cause of the problem of climate change – carbon dioxide emissions. They only have the potential to partially manage some of the symptoms at best. For example, solar radiation management methods do nothing to address the symptom of ocean acidification, and the maximum cooling effect that cloud brightening can achieve is limited.

This is one of the arguments against pursuing geoengineering. Surely we should focus our efforts on mitigation, rather than a partial fix?

The answer to this is “absolutely”. Climate engineering is risky and full of uncertainty, and will impact the entire world’s population.

But then what is the motivation for the research that is occurring in the USA and UK into geoengineering methods?

This answer is more nuanced, and is based on the timescales that are involved in mitigation and climate change. Even if we stopped increasing our emissions from today, CO₂ levels in the atmosphere would continue to rise for hundreds of years. Reaching a ‘tipping point’ in the climate may be unavoidable. How likely is it that we will be able to reduce our emissions quickly enough to avoid the worst effects of climate change?

We base our future predictions on climate modelling, which is validated against past observations. There is much scientific uncertainty, but current predictions indicate that we will see significant climate impacts in the future.

Research into the feasibility, risks and impacts of climate engineering has begun. This research may lead us to conclude that some (or even all) geoengineering techniques are simply not viable. The development times for the most-promising technologies are currently estimated to be between decades and centuries.

At some stage in the future, climate engineering, with all its shortcomings, may offer a better way forward than living with the effects of extreme climate change.

Get-out-of-jail-free card

Some argue that climate engineering is a “get-out-of-jail-free card” to carbon emitters. Others prefer to call it an “insurance policy” for the earth. Will consideration of climate engineering lessen political will for reducing CO₂ emissions? (This is known as the “moral hazard” argument.)

Does climate engineering offer an easy way out?

Climate engineering is clearly not a desirable course of action. It offers no freebies or rewards.

There are few proponents of geoengineering at present. Discussion of this technology often acts as to raise awareness of the urgency of the climate situation, thus increasing resolve to reduce emissions.

What is clear however, is that the first publicised outdoor test of a climate-engineering technology will place a marker in the political and scientific landscape.

Testing cloud brightening

In a recent paper, University of Washington atmospheric physicist Rob Wood describes a possible outdoor test of cloud brightening. This test is yet to receive funding support.

The first stage of Wood’s experiment involves testing the seawater-spraying technology, by examining the properties of the sprayed particles and their dispersion in the wind. The second stage of the test measures the effect of an aerosol plume on a cloud, and the third stage would look at the effect of 5-10 plumes arranged in a line.

Much like the SPICE balloon test, the experiment would test the feasibility of the spraying technology. Unlike SPICE, the experiment would also involve monitoring the effect of introduced particles on the atmosphere.

The same governance and intellectual property issues that led to the cancellation of the SPICE test also apply to cloud brightening. In view of this funding of a cloud brightening test would be a controversial and symbolic move.

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24 Comments sorted by

  1. Brad Hut

    Go-for

    Call the Science cops & lock these Mad Scientists up.
    This "...cooling effect." will warmup the Planet. Outlaw "geoengineering"
    So there is a term for these Evil-Doers "Geoengineer" lock-up your Daughters.

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  2. Ian Donald Lowe

    Seeker of Truth

    "Cloud brightening involves seeding clouds with a fine spray of saltwater, which encourages cloud micro-droplets to form."
    There is the great evil in this proposal, right there. Turning rainwater into salt water will destroy life! This is an evil, destructive concept and all geoengineering projects, including those in progress at this point in time must be stopped. Stop poisoning our atmosphere and our rainwater and our land you evil, vile, disgusting animals!

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    1. Roger Dargaville

      Research Fellow, Energy Research Institute at University of Melbourne

      In reply to Ian Donald Lowe

      Ian Lowe - Please keep it civil - I don't think that's the kind of response we promote here. And it's a bit over the top - rain droplets form around a cloud condensation nuclei which is often a sea salt particle. So rain water already has salt in it.

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    2. Ian Donald Lowe

      Seeker of Truth

      In reply to Roger Dargaville

      I don't care what you think Roger, I am sick of hearing about the poisons (aluminium particles, Sulhpur-dioxide, etc.) that are being sprayed into our atmosphere and the use of HAARP technology to 'alter' our weather. When these 'people' start playing God with my life, then I believe I have every right to make an angry response. It is the human response to a real threat.
      You say rainwater has salt in it, if that is so, that is not natural. Salt will not evaporate, salt does not naturally enter the stratosphere. It may be there as a result of pollutants but that is a direct result of the actions of large corporations and they should be stopped as well.
      Fresh drinking water, untainted by pollutants, is one of the basic fundamental requirements of all life. Stop messing with our water. Stop trying to destroy life. I am sick of all of the lies and deception and destruction. Just stop!

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    3. Roger Dargaville

      Research Fellow, Energy Research Institute at University of Melbourne

      In reply to Ian Donald Lowe

      Ian - I appreciate you don't like the idea of geoengineering. I don't like it either, but I would rather it was researched so we understand why we shouldn't do it.

      Salt aerosols do occur naturally as the wind blows over the ocean surface. They are in very small concentrations so it barely registers in fresh water supplies. Rainwater in fact has lots of natural impurities in it - collect some rain water and observe the residue left behind when it evaporates.

      Hope that helps alleviate some of your fears.

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    4. David Arthur

      resistance gnome

      In reply to Ian Donald Lowe

      Ian, it would have been good had you begun your search for truth a couple of decades ago, when scientists began voicing alarm (it had previously only been concern) about anthropogenic recycling of geosequestered carbon to the atmosphere.

      Had you begun your search for the truth back then, you would have recognised the veracity of the cause of the scientists' concern. You may have helped forestall the emergence of suicidal activism among the world's Right-Wing loons, reflected in Karl Rove's…

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    5. Gerard Dean

      Managing Director

      In reply to Roger Dargaville

      Mr Dargaville

      Alleviate my fears? The only fear I have is that the crazies continue research into whitening clouds. Let's follow on from my simple arithmetic (comment below) to show that placing a 1 millimetre lay of salt water over the 50% cloud coverage of the earth would take more than 2 billion, I stress, 2 thousand, million Jumbo Jet flights

      Even reducing the coverage to 1% of the earth's cloud cover with a 1 micron spray,( 0.000001 metre thick or 1/600th of the length of visible light) of sea water would take more than 20,000 Jumbo Jet flights.

      So, assuming that each Jumbo flight uses 30 tonnes of fuel, it will take 600,000 tonnes of fossil based JetA1 fuel to spray a 1 MICRON layer of salt water over 1% of the earth's clouds.

      Sheer, absolute, unadulterated, total, madness.

      My only joy in this sad event is knowing that we, the Australian taxpayer, are paying for this drivel.

      Gerard Dean

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    6. David Arthur

      resistance gnome

      In reply to Gerard Dean

      Mr Dean, ever since you found out that the grade of fuel used by jet aircraft is called "Jet A1", you have bandied the phrase "Jet A1" into EVERY SINGLE CONVERSATION to which you have contributed. Matter of fact, it's about the only thing you ever contribute.

      Rest assured that technologists are labouring away on replacing fossil-based liquid fuels with biofuels, thereby making redundant your major contribution to these discussions. Perhaps you could make it a point to keep others apprised of developments in biofuel technology.

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    7. Mike Hansen

      Mr.

      In reply to Gerard Dean

      "Even reducing the coverage to 1% of the earth's cloud cover with a 1 micron spray,( 0.000001 metre thick or 1/600th of the length of visible light) of sea water would take more than 20,000 Jumbo Jet flights."

      Gerard has not heard of wind even though his posts are usually examples of extreme flatulence.

      Gerard - this is the problem when you post without reading or understanding the article.

      "The proposed technology being investigated by SPICE involves a fibre-reinforced hose, held up by a helium balloon. Reflective droplets would be pumped up the hose, and sprayed out 20 kilometres above the earth’s surface.

      Predictions show that if five to ten of these hose-balloon systems were deployed around the world, they could provide a global mean cooling effect of 2°C. That’s a significant amount of global cooling."
      https://theconversation.edu.au/geo-engineering-why-research-something-we-never-want-to-use-3684

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    8. Gerard Dean

      Managing Director

      In reply to David Arthur

      Mr Arthur,

      Are you seriously saying that in 2022, "... people will be demanding geoengineering, despite all its risks"

      My simple maths above clearly illustrated that even to whiten a tiny fraction of the earth's clouds with a sub-microscopic 1 micron of salt water would take 20,000 jumbo flights to deliver the load.

      It would take world's entire industrial output to make enough Jumbo Jets and JetA1 fuel to deliver a practical mist of saltwater to a fraction of the clouds.

      It would mean no more overseas jet flights for you or your family or the author of the article.

      It is so stupid, it is sad.

      Gerard Dean

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    9. David Arthur

      resistance gnome

      In reply to Gerard Dean

      Mr Dean, there are several forms of geoengineering.

      You may be interested in a Perspective published in Nature Climate Change August 2012: Pope et al, "Stratospheric aerosol particles and solar-radiation
      management", doi:10.1038/nclimate1528. Work referred to in this Perspective was focussed on TiO2 precisely because of its UV-interactability.

      A relatively cheap form of geoengineering in 2022 might be for the nuclear-armed nations of the world to get rid of their remaining weapons by turning…

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    10. Gerard Dean

      Managing Director

      In reply to Mike Hansen

      Oh dear, dear me, Mr Hansen

      I checked out the Conversation article you linked too above. It describes that we could spray water from a halft a dozen balloons at 20,000 metres altitude to cool the earth's atmosphere by 2 deg C.

      So I did the maths.

      Hose diameter: 1 inch internal diameter
      Hose water volume and weight: 9,800 Kg (20,000 metres X cross sectional area of hose)
      Hose type: Hydraulic. 4 Kg weight per metre (Chosen because water column pressure at ground level would be 17,000…

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    11. Mike Hansen

      Mr.

      In reply to Gerard Dean

      "Do you really think it is a good idea, Mr Hansen?"

      No I don't.

      We need to reduce our fossil fuel usage now, not hold out hope for some geoengineering fix in the future. Leave aside the engineering required and the possible side effects, this solution is only temporary and does not solve the other aspects of AGW like ocean acidification.

      BTW Gerard. No mocking from me when you actually read the article and respond to it rather than setting up a strawman to knock down.

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  3. Michael James

    Research scientist

    "Climate engineering is clearly not a desirable course of action. "

    Really?

    What if the Arctic Sea Ice continues to diminish or disappear entirely, with the predicted disastrous disruption of the Gulf Stream and subsequent effects on North America and worse, Europe. (Where much of the world's grain is grown, thus consequences for the entire world. Not to mention political destabilization and a dozen other unpredictable outcomes.)

    So, what if cloud brightening over the north polar sea could reverse this effect just the bit necessary to prevent the disastrous and self-catalyzing melting?

    Seriously, the author is saying no research should be done on this approach?

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    1. helen stream

      teacher

      In reply to Michael James

      Michael James:

      Why do you suppose warmists completely ignore the fact that some of the world’s most prominent climate scientists find, from their research, that at least 50% of the Arctic warming, and much of the glacier melt---and the melt of the permafrost is due , not to CO2, but to black carbon[ soot] most of which is produced by the burning of biomass in China, India, Indonesia, other parts of Asia and Brazil?

      ‘Washington, DC, July 29, 2010 – Reducing emissions of black carbon, the dark…

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    2. Mike Hansen

      Mr.

      In reply to helen stream

      According to Jacobson, the contribution of soot (black carbon) to global warming is 16%. You made the 50% claim up.
      http://www.stanford.edu/group/efmh/jacobson/PDFfiles/0710LetHouseBC1.pdf

      Even the people you quote disagree with your claims
      “It is important to emphasize that BC reduction can only help delay and not prevent unprecedented climate changes due to CO2 emissions.” (Ramanathan and Carmichael. Global and regional climate changes due to black carbon. Nature Geoscience (2008) vol. 1 (4…

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  4. Murray Webster

    Forestry-Ecology Consultant/Contractor

    To any climate scientists out there... it occurred to me that warmer sea surface temperature would mean more cloud - like the LaNina we have had over the last couple of years. If the global warming increased sea surface temperature would that increase cloud and therefore sunlight reflectance? and hence less warming of the earths surface?? I guess this has been accounted for in the modellig

    Once we start climate engineering, then we will have a new weapon in geopolitical conflict.... Russia might do quite well economically out of a thawing tundra and China could open up new agriculture in mongolia, all the while increasing aridity and decreasing agricultural productivity in the US

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  5. Ian Rainbow

    Analytical Chemist

    At the risk of exacerbating some of the wilder statements decrying geo-engineering on this page I do want to ask some questions about the process proposed for cloud whitening. Injection of seawater into the upper atmosphere where the salts may be expected to nucleate water droplets to form seems reasonable and indeed rather like cloud seeding with sodium iodide. Looking at the composition of seawater, it contains a lot of sodium chloride, somewhat less sodium bromide and a variety of other salts…

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    1. David Arthur

      resistance gnome

      In reply to Ian Rainbow

      Ian, you're discussing chemistry, which is a pretty sure way of engendering no replies other than from other people who have at least studied some chemistry. [I find this quite curious, since it is not possible to understand the mechanism of the greenhouse effect without understanding a little atmospheric chemical physics].

      I hadn't previously given a thought to possible consequences of increasing tropospheric chloride; on first reflection, it may be plausible that some of this chloride could pass the tropopause to the stratosphere, where it could be photo-oxidised to chlorine and hence catalyse ozone destruction.

      You may be interested in a Perspective published in Nature Climate Change August 2012: Pope et al, "Stratospheric aerosol particles and solar-radiation
      management", doi:10.1038/nclimate1528. Work referred to in this Perspective was focussed on TiO2 precisely because of its UV-interactability.

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  6. Gerard Dean

    Managing Director

    So let me get this straight Kirsty!

    You want us to use heavy lift jet aircraft to burn millions of litres of irreplaceable fossil based JetA1 fuel to fly and spray millions of tonnes of sea water on top of clouds so they go whiter to stop climate change that is caused by burning fossil fuels, including JetA1 fuel.

    Earth's surface area 510,072,000 square kilometres. Assume 50% cloud cover = 255,036,000 square kilometres. Fine spray = 1 mm depth of water. Amount of water required to place fine…

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    1. Mike Hansen

      Mr.

      In reply to Gerard Dean

      Gerard - In your rush to construct your arithmetic fantasy, it is clear you did not bother to read Kirsty's article.

      Here are some quotes from Kirsty that you obviously missed.
      "Surely we should focus our efforts on mitigation, rather than a partial fix? The answer to this is “absolutely”. Climate engineering is risky and full of uncertainty, and will impact the entire world’s population."
      "Climate engineering is clearly not a desirable course of action. It offers no freebies or rewards."

      Gerard - I know you do not get paid to write your drivel - to you it is a natural follow on from you getting your politics and climate science from Andrew Bolt.

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  7. David Arthur

    resistance gnome

    Thanks for this article, Dr Kuo.

    It is certainly true that "Even if we stopped increasing our emissions from today, CO₂ levels in the atmosphere would continue to rise for hundreds of years"; boreal cryosphere thawing has already advanced to being a net emitter of methane and CO₂, so that atmospheric greenhouse gas concentrations are starting to increase independent of human influence.

    To begin the process of restoring the climate to conditions which prevailed throughout the Holocene (the…

    Read more
  8. David Arthur

    resistance gnome

    Thanks for this article, Dr Kuo.

    It is certainly true that "Even if we stopped increasing our emissions from today, CO₂ levels in the atmosphere would continue to rise for hundreds of years"; boreal cryosphere thawing has already advanced to being a net emitter of methane and CO₂, so that atmospheric greenhouse gas concentrations are starting to increase independent of human influence.

    To begin the process of restoring the climate to conditions which prevailed throughout the Holocene (the…

    Read more