Cooling: Solar Radiation Management
(Geo-Engineering)
The biggest form of geo-engineering is adding vast amounts of CO2 to the air.
That causes huge damages, most of them delayed,
Embedded Files
The graph of energy intensity (density) radiated to space by Earth, on the vertical axis, correponds to frequency on the bottom (wavelength on the top). Less is radiated to space in the absorption bands of the principal greenhouse gases (GHGs). The principal atmospheric infrared window thru GHGs is 10 to 12 µm. 320 K, the top "curve", = 47°C = 117°F. 22°C MODTRAN Model with Tropical setting = 295 K = 72°F.
Albedo (reflectivity) loss feedbacks dominate current and especially future planetary warming.
To survive, this requires action to reverse thiis loss (planetary darkening). Methods to do this are shown in the two figures below.
Solar Radiation Modification - A Last Resort, but for How Much Longer? 0426.rtf - The danger is that ever larger amounts of stratospheric aerosols would clump together, providing ever less marginal benefit, for a perhaps too modest upper limit on direct cooling from this #1 method. There are also issues in scaling up a fleet of airplanes to ferry aerosols all the way up to the stratosphere.
Chapter 3 - Planetary Darkening – When the World Stops Shining 0526.rtf
Source is here. See also other chapters.
The figures below show the increase in absrobed solar radiation over time and space. The left graph shows that, over 20 years, Earth has absorbed more solar radiation - it has been getting darker (less reflective) - over the 3 major ocean basins. Especially over the North Pacififc and North Atlantic. Changes over land are not shown.
The right graph shows sulfate concentrations (which reflect some sunlight back into space) over the ocesns before 2020.
Clouds
Clouds reflect lots of sunlight (roughly 68 Watts / square meter) back into space, for Earth's major cooling effect.
Cooling Methods - Types with details
summary by Ron Baiman, Mike McCracken et al.
summary by Gene Fry
An HPAC member's take on relative effectiveness of 9 methods to cool the planet (atmosphere mostly). Marine Cloud Brightening is rated top, followed by atmospheric methane oxidation.
Below are potential temperature trajectories that use solar radiation management, combined with CO2 removal (and of course ending CO2 emissions, by 2050 except for 2035 peak), to hold atmospheric warming to survivable levels.
Worst Case:
No Peak,
4.5° by 2100
Best Case:
2.45° Peak in 2050,
1.4° in 2100
for $10-30 million / year
In most locations, the modeled impact of solar geo-engineering (stratospheric aerosol injection (SAI) in particular) is to reduce mortality, compared to doing nothing to cool Earth off.
The death rate without SAI is 14 times that when using SAI.
Below, as above, SAI = Stratospheric Aerosol Injection (what major volcanic eruptions do) and MCB = Marine Cloud Brightening. CH4 is Methane, the leading Well Mixed Greenhouse Gas after CO2.
2023-26 Articles
2023-26 Articles
The 3 Levers That Could Stabilize the Climate 0726.rtf - Decarbonization, CO2 Removal, and Solar Radiation Management
Stratospheric Aerosol Injection Might Make Flights Smoother 0726.rtf
Scientists Are Looking at Marine Cloud Brightening to Squash El Niño Heat 0726.rtfWood Ice Seed for Sea Ice Generation 0225.rtf1st Experiment to Thicken Arctic Ice with Seawater Shows Promise — But 0726.rtfAtmospheric Scrubbing Could Reduce Cooling Effects of Stratospheric Aerosol Injections 0626.rtfTermination Shock’ - Trust Our Expert Warnings on Geo-engineering’s Planetary Risks 0626.rtfCan Some Very Tiny Particles Cool the Planet? Stardust Solutons Says Yes. 0526.rtf - It has developed a calcium carbonate core (CaCO3) wrapped in a silica shell, in a micro size, for injection into the stratosphere, after some years of testing and pilot injections. It will be much kinder to the stratospheric ozone layer than sulfate iinjections (what major vocanic eruptions do).Solar Geo-Engineering Isn’t a Moral Hazard - It’s a Moral Imperative 0426.rtfMarine Cloud Brightening Could Offset Warming from Less Air Pollution 0226.rtfBan on Vital Geo-Engineering Research Would Be Catastrophic Mistake 0126.rtfHow We Can Safely Experiment with Reflecting Sunlight Away from Earth 0126.rtfWildfire Smoke Lofted Miles High Could Have Cooling Effect on Earth's Climate 1225.rtfClmate Hot Takes for 2025 - 1225.rtf - This article / opinion begins "Scientific evidence in 2025 showed global warming accelerating faster than expected, while emissions continued to rise and climate policy lagged dangerously behind physical reality.... "It is unlikely that any future 3-year average will drop below [1.5°C].... "The projections of continuing high emissions - and the weakening of the carbon sinks in forests and in soils and permafrost - means we are likely to exceed 3°C of warming. “We are potentially headed towards 3°C of warming by 2100 if we carry on with the policies we have at the moment,” says IPCC Chair Professor Jim Skea." "5 years ago the late Professor Will Steffen argued that: “Given the momentum in both the Earth and human systems, and the growing difference between the ‘reaction time’ needed to steer humanity towards a more sustainable future, and the ‘intervention time’ left to avert a range of catastrophes in both the physical climate system (e.g., melting of Arctic sea ice) and the biosphere (e.g. loss of the Great Barrier Reef), we are already deep into the trajectory towards collapse.”" Farther on, the article says "At least 2 organizations are now either deploying atmospheric cooling techniques at small scale (makesunsets.com) or actively testing solar radiation management techniques (stardustsolutions.com), so the cooling governance debate is no longer an abstract one.UK scientists are launching outdoor geo-engineering experiments as part of a £50 million government-funded program run by Advanced Research and Invention Agency (ARIA).
In May, Cambridge hosted the Arctic Repair Conference 2025, a pioneering conference hosted by the Center for Climate Repair, in association with the University of the Arctic. Its focus on innovative climate engineering techniques was designed to combat the rapid changes taking place in the Arctic. The podcaster Nate Hagens asked “Will we artificially cool the planet?” The science and politics of geo-engineering, and scientists published a call for more climate intervention research.
Co-Ordinated Solar Geo-Engineering Can Lower Temperature Cheaply, Save Lives 1125.rtfGlobal Cooling Startup Raises $60 Million to Test Sun-Reflecting Technology 1025.rtfA Responsible Way to Cool the Planet 0925.rtf - by David Keith, a pioneer of CO2 removal AND stratospheric aerosol injection (SAI). Trees Alone Won’t Save Us – They Have Less Potential to Fix Climate than Hoped. 0925.rtf - Trees are darker than other vegetation.Scientists Warn against Plans to Artificially Cool Polar Regions 0925.rtf - The scientists said media interest in the proposals far outstrips their practicality and distracts from the need to invest in adaptation and decarbonization, which they say could reverse warming trends in a matter of decades. [In this, they are mistaken. Equilibrium warming for current CO2 levels is some 5°C above 1880 baseline. Decarbonization alone will not reverse warming trends nearly that soon, or keep a livable climate.]Cooling Isn’t Plan B – It’s How Plan A Succeeds 0825.rtf - how cooling supports stopping emissions and removing the CO2 we have already put in the airGeo-Engineering- a Bad Idea Whose Time Has Come? 0825.rtfMan-Made Clouds That Could Help Save the Great Barrier Reef 0725.rtfUnexpected Failure of Regional Marine Cloud Brightening in a Warmer World 0625.rtfComparing the Benefits and Risks of Solar Geo-Engineering - Keith & Harding 0625.rtf - Injecting sulfate aerosols in the stratosphere reduces mortality risk from heat, but increases risks from air pollution and ozone loss. The reduction in mortality by doing cooling—a benefit—is roughly 10 times larger than the increase in mortality from air pollution and ozone loss. The paper builds on recent work by Greenstone and Eastham, in collaboration with Vecchi and Yang. From another perspective, the benefit is 40 times the harm.UK Funds 5 Geo-Engineering Trials to Combat Global Warming 0625.rtfArctic Winter High-Latitude Seasonal Stratospheric Aerosol Injection 0525.rtfNew Technologies Are Helping to Re-grow Arctic Sea Ice 0425.rtf - Similar to diagram above, water from below sea ice would be added to the top of sea ice. A company is now working to do this, in situ on the Arctic Ocean,Impact of Solar Geoengineering on Temperature-Attributable Mortality 1224.rtf - with David Keith as 3rd author. Mean outcome of simulations of mortality from climate change, with and without stratospheric aerosol injection (SAI). The study, in the case of +2.5°C warming and 1.0°C of SAI cooling, finds that mortality is 13 x as great without SAI as with it. However, the error bounds are large. More research and preparation is needed. [The background is that loss of reflectivity (darkening, a.k.a. albedo loss) contributed more than twice as much warming as greenhouse gases over 2000-2024. Most of the darkening was due to cloud cover loss over the oceans (from 60% to 53% over the oceans over 1984-2019).]Solar Geo-Engineering Could Save Up to 400,000 Lives per Year 1224.rtf - one take on the above study.Plan to Refreeze the Arctic Sea Ice Is Seeing Promising Results 1224.rtfGlobal Warming Is Speeding Up. Another Reason to Consider Geo-Engineering 1224.rtf“EU Should Ban Space Mirrors and Other Solar Geoengineering” 1224.rtfThwaites Glacier Melting Faster than Expected. Use Giant Submarine Curtains? 1124.rtf - Preventing more land ice melt will prevent a bit of Earth darkening (albedo loss), which can slow warming. It might give a little breathing room to stop putting carbon in the air and remove what we have already put in.Silicon Valley’s Elite Pour Money Into Blotting Out the Sun 1024.rtfDiamond Dust in Stratosphere Could Cool Earth Better than Other Substances 1024.rtfNow May Be the Time to Experiment with Mother Nature - Carefully! 0824.rtfCloud Brightening over Oceans may Stave Off Climate Change, but with Risk 0824.rtfThe Mirror Roofs Cooling Homes in Freetown, Sierra Leone 0824.rtfWhy Spraying Sulfur into the Sky is Not Crazy 0624.rtfClick for moreProf. David Keith Has a Plan to Cool Earth. There’s Growing Interest. 0824.rtfClimate Engineering off US Coast Could increase Heat Waves in Europe 0624.rtfEnvironmental Defense Fund to Study Effects of Artificially Cooling Earth 0624.rtfDimming the Sun to Cool the Earth - Is Solar Geo-Engineering the Future? 0524.rtfAutonomous Solar-Powered Catamarans to Enhance Marine Cloud Brightening 0524.rtfCloud Cover Is Easier to Affect than Previously Thought 0524.rtfHumans Might Need to Re-Engineer the Climate 0424.rtf - Washington Post editorialGeo-Engineering Could Save the Ice Sheets – but Only if We Start Soon 0424.rtfRadical Experiment Shows Cloud Brightening May Be Climate’s White Knight 0424.rtfAMR’s Technical Solution to Cool Global Climate by 0.5-1.0°C within 20-25 Years 0424.rtfCloud Engineering Could Be More Effective against Global Warming than Previously Thought 0424.rtWarming Is Getting Worse. So They Just Tested a Way to Deflect the Sun. 0424.rtfHow Cloud Brightening Might Save the Great Barrier Reef 0424.rtfWarming Is Getting Worse. So They Just Tested a Way to Deflect the Sun. 0424.rtfNOAA Calls for Urgent Investigation into Carbon Removal and Brightening Earth 0324.rtfGeo-Engineering Faces Backlash over Regulatory Gaps and Unknown Risks 0324.rtfPumping Seawater over Frozen Ocean to Save the Arctic's Sea Ice 0324.rtfWill a Dutch Startup’s Plan to Restore Arctic Sea Ice Work? 0224.rtfDehydrate the Stratosphere to Curb Global Warming? 0224.rtfCould a Giant Parasol in Outer Space Help Solve the Climate Crisis? 0224.rtfHow ‘Cooling Glass’ Could Reflect Solar Radiation Back into Space 0124.rtfWhat Are Main Global Solar Radiation Modification (SRM) Technologies? Why? 0923.rtfStratospheric Aerosol Injection (SAI) in the North Warms Ocean at Antarctic Ice Shelves, but SAI in the South Cools Them 0623.rtfExperts Call for Global Moratorium on Efforts to Geo-Engineer Climate 0923.rtfWhat You Need to Know about Reflecting Sunlight to Cool Earth 0823.rtf - emphasis on most developed method, imitating volcanoes by injecting aerosols into the stratosphereSolar Geo-Engineering — Climate Solution or Pandora's Box? 0723.rtfChinese Scientists Are Trying to Shield Melting Glaciers From the Sun 0723.rtfWhite House Cautiously Opens Door to Blocking Sun’s Rays to Cool Earth 0723.rtfEU Looks into Blocking Out the Sun, as Climate Efforts Falter 0623.rtfHow Does Albedo Affect Climate? 0423.rtfSpies Worry that a Sun-Blocking ‘Climate Solution’ Could Trigger War 0223.rtfStudy Reflecting Sunlight to Cool Earth before Climate Change Gets Much Worse, Urge 60 Scientists 0223.rtfWhy Billionaires Are Obsessed with Blocking Out the Sun 0223.rtfGeorge Soros Sees Arctic Threat to Civilization Survival, Wants Geo-Engineering 0223.rtfSolar Radiation Management – Key Climate Solution or Path to Catastrophe? 0223.rtfSimple Graph Shows Why We Must Study Ways to Reflect Sunlight to Cool Earth 0123.rtfStartup Offers Stratospheric Geo-engineering as a Service 1222.rtfCan Geoengineering Fix the Climate? 100s of Scientists Say Not So Fast. 1222.rtfWhite House Pushes Ahead Research to Cool Earth by Reflecting Back Sunlight 1022.rtfWhat Could We Do Specifically to Cool the Arctic? 0822.rtfCan This Ice-Making Submarine Save The Arctic? 0622.rtfDimming the Sun Could Expose 1 Billion More People to Malaria 0422.rtf - by decreasing the area that is too hot for malariaWeird Ideas to Fix the Climate Crisis Might Be All We Have 1021.rtfWhat’s the Least Bad Way to Cool the Planet?1021.rtfOpponents of Geo-Engineering Misunderstand Humanity’s Choices 0621.rtfNational Academy of Scientists Supports Reflecting the Sun’s Rays 0321.rtfWe Must Start Refreezing the Arctic Ocean Very Soon to Save Our Megacities 0121.rtfAs Earth Warms Faster, Scientists Eye Solar Radiation Management to Cool Off 0121.rtfAs Climate Disasters Pile Up, Solar Radiation Management Plan Gains Traction 1020.rtfScientists Trial Cloud Brightening Equipment to Shade, Cool Great Barrier Reef 0420.rtfHeat the Arctic to Cool the Earth, Some Scientists Say 1219.rtf - so sea ice disappears, allowing heat from ocean below to escape into space. How does that interact with albedo change from light ice to dark water?Pumping Seawater atop Sea Ice to Refreeze Arctic Sea Ice Isn't the Best Idea 1219.rtfCan Arctic 'Ice Management' Combat Climate Change? 1219.rtfAncient Upheavals Show How to Geo-Engineer a Stable Climate 0619.rtf - in-depth (for news article) review of paleoclimate relevant to today, and of geo-engineering methods, both CO2 removal and soalr radiation management.Geo-Engineer the Planet? More Scientists Now Say It Must Be an Option 0519.rtfPlan to Artificially Cool Earth's Climate Could Be Safe, Study Finds 0319.rtfSolar Radiation Management May Not Cool the Oceans, Study Says 1018.rtfGeo-Engineering Problem - Dimming the Sky Won’t Save the World’s Harvests 0818.rtfThe Best Way to Shade Earth 0718.rtf - Inject sulfates (into stratosphere) in sub-tropics to mid-latitudes, not near the equator.2 Audacious Plans for Saving the World’s Ice Sheets 0518.rtfCould Sprinkling Sand Save the Arctic's Shrinking Sea Ice? 0418.rtfDeveloping Nations to Study Ways to Dim Sunshine, Slow Warming 0418.rtfWhat on Earth? Why Climate Change Skeptics Are Backing Geo-Engineering 0318.rtf“Can We Refreeze the Arctic?”, Scientists Are Beginning to Ask 0318.rtfCase against Geo-Engineering 1117.pdf - 80pp4 Radical Plans to Save Civilization from Climate Change 0917.rtf - merely a quick summary: 3 are SRM, 1 CDR.
carbon vacuums (CDR), salt-spraying ships (clouds), sparkle-blasting ballons (stratospheric sulfates), and super-sized space mirrorsScientists Want to Give the Atmosphere an Antacid to Relieve Climate Change 1216.rtf - calcium carbonates intead of sulfatesOcean Warming due to Plankton Collapse 0616.rtfScientists Dim Sunlight, Suck Up CO2 to Cool Planet 0717.rtfA Cirrus Cloud Climate Dial? 0717.rtfShould We Geo-Engineer Earth to Halt Warming? Scientists Say Maybe 0717.rtfUS Scientists Launch World's Biggest Solar Geo-Engineering Study 0317.rtfCould a £400 Billion Plan to Refreeze the Arctic before the Ice Melts Really Work? 0217.rtfWhite House Urges Research on Geo-Engineering to Combat Global Warming 0117.rtf
carbon vacuums (CDR), salt-spraying ships (clouds), sparkle-blasting ballons (stratospheric sulfates), and super-sized space mirrorsScientists Want to Give the Atmosphere an Antacid to Relieve Climate Change 1216.rtf - calcium carbonates intead of sulfatesOcean Warming due to Plankton Collapse 0616.rtfScientists Dim Sunlight, Suck Up CO2 to Cool Planet 0717.rtfA Cirrus Cloud Climate Dial? 0717.rtfShould We Geo-Engineer Earth to Halt Warming? Scientists Say Maybe 0717.rtfUS Scientists Launch World's Biggest Solar Geo-Engineering Study 0317.rtfCould a £400 Billion Plan to Refreeze the Arctic before the Ice Melts Really Work? 0217.rtfWhite House Urges Research on Geo-Engineering to Combat Global Warming 0117.rtf
Earth is getting darker, which makes it absorb more heat, and thus warm up. Warming is not just from greenhouse gases. However, the changing albedo was initiated by adding greenhouse gases, which were the trigger.
At right, observe that the dark forest (mesic savanna) reflects less sunlight than the semi-arid savanna or the aird savanna. The more arid conditions will have a net cooling effect, other things equal.
2 methods reviewed: stratospheric aerosol injection and marine cloud brightening
2016 Articles and earlier
2016 Articles and earlier
Scientists Want to Give the Atmosphere an Antacid to Relieve Climate Change 1216.rtf - calcium carbonates intead of sulfatesGeo-Engineering to Alter Climate Moves Closer to Reality 1016.rtfOcean Warming due to Plankton Collapse 0616.rtf - The fewer plankton make correspondingly less dimethyl sulfide, which serve as important cloud condensation nuclei to form cooling cloouds near the ocean surface.Geo-Engineer Polar Glaciers to Slow Sea-Level Rise 0318.rtf - Make them whiter, or thicker.Sea Level Rise? Can We Pump Quadrillions of Tons of Seawater 2 Miles High? 0316.rtfMassive Tree Farms, Soil Carbon Sequestration May Be Really Bad Climate Ideas 0216.rtfCould Bright, Foamy Wakes from Ocean Ships Combat Global Warming? 0116.rtfNanostructure and Nanonet Solar Cells, CCS, SRM Could Slow Climate Change 1215.rtfCould the Smell of the Sea Help Cool a Warming Planet? 0815.rtfGeo-Engineering Will Not Save Ocean Life from Centuries of Acidification 0815.rtfCloud Brightening Experiment Tests Tool to Slow Climate Change 0715.rtf‘Last Ditch’ Climate Change Remedies Olivine & Biochar Remove CO2 from Air 0615.rtfWhitening Arctic Ocean Surface to Reflect Sunlight into Space Will Fail 0415.rtfWarning over Aerosol Climate Fix 0415.rtfScientists Urge Global ‘Wake-up Call' to Deal with Climate Change 0215.rtfPlanet Reboot - Fighting Climate Change With Geo-Engineering 1214.rtfGeo-Engineering - Climate Fixes ‘Could Harm Billions' 1114.rtfMany Experts Say Technology Can't Fix Climate Change 1114.rtfIf You Start Geo-Engineering to Halt Global Warming, Don't Stop 1213.rtfClimate Engineering- Minor Potential, Major Side Effects 0214.rtfEarth-Cooling Schemes May Devastate, Need Global Sign-off 0313.rtf - Solar Radiation Management, chiefly sulfates in the stratosphere - spread droughts and deserts to new areasGeo-Engineering Responses to Rapidly Shrinking Arctic Ice Cap 0213.rtf Let's Play God- Experiments That Might Save (or Destroy) the World 1013.rtfIPCC Climate Report Puts Geo-Engineering in the Spotlight 1013.rtfGeo-Engineering Methods.pdfSowing Stratosphere with Sulfates.pdfEarth-Cooling Schemes May Devastate, Need Global Sign-off 0313.rtf - Solar Radiation Management, chiefly sulfates in the stratosphere - spread droughts and deserts to new areasOverview of Geo-Engineering 1112.rtf - introduction to amounts (efficacy) and costs, for 12 methodsSulfates in Stratosphere Geo-Engineering Can Disrupt Rainfall Patterns 0612.rtfCentral Intelligence Agency Studies Geo-Engineering 0713.rtfGeo-Engineering Responses to Rapidly Shrinking Arctic Ice Cap 0213.rtfGet Cirrus in the Fight Against Climate Change 0113.rtfAltering Clouds to Fight Climate Change 0113.rtfAlgae Farming for Climate Change a Big Waste of Money 1212.rtfOverview of Geo-Engineering 1112.rtfGeo-Engineering Interest Grows 1110.rtfGeo-Engineering Poses Drought Risk 0809.rtfThe Radiative Forcing Potential of Different Climate Geo-Engineering Options 0809.rtfGeo-Engineering to Slow Warming 1106.rtf - 5 methods discussed or mentioned
The figure shows 4 types of SRM and 5 types of CO2 removal. Some methods are not shown, especially for CO2 removal, notably organic farming for soils. Also CH4 removal, notably by iron salt aerosols.
SRM shown includes mirrors, aerosols, reflective crops, and cloud seeding.
CO2 removal shown includes foresting, artificial trees, biochar, ocean iron fertilization, and carbonate addition. Accelerated rock weathering, a major method, is not shown, nor is use of ocean biology.
Add to the diagram storing carbon in soils, via (1) rapid (~1 week / small pasture) rotation grazing, (2) no-till farming, especially organic farming, and (3) biochar.
LIke foresting, these requires large land areas, but they (especially grazing) work much better in dry areas, which will grow some grass but few or no trees. Like foresting, these are already being used, at negligible cost. Moreover, soils generally store more carbon per acre than standing biomass (e.g., forests), especially toward the poles. (But near the equator, standing biomass stores much more than the soil there, except in peatlands.)
Section Map: Reversing Climate Change
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