Climate engineering

Climate engineering (or geoengineering) has been used as an umbrella term for both carbon dioxide removal and solar radiation management, when applied at a planetary scale.{{rp|168}} However, these two methods have very different geophysical characteristics, which is why the Intergovernmental Panel on Climate Change no longer uses this term.{{rp|168}} This decision was communicated in around 2018, see for example the Special Report on Global Warming of 1.5 °C.{{Cite book |url=https://www.cambridge.org/core/product/identifier/9781009157940/type/book |title=Global Warming of 1.5°C: IPCC Special Report on impacts of global warming of 1.5°C above pre-industrial levels in context of strengthening response to climate change, sustainable development, and efforts to eradicate poverty |date=2022 |publisher=Cambridge University Press |isbn=978-1-009-15794-0 |edition=1 |doi=10.1017/9781009157940.008}}{{rp|550}}

According to climate economist Gernot Wagner the term geoengineering is "largely an artefact and a result of the term's frequent use in popular discourse" and "so vague and all-encompassing as to have lost much meaning".{{Rp|page=14}}

Specific technologies that fall into the climate engineering umbrella term include:{{rp|30}}

• Carbon dioxide removal
• Biochar: Biochar is a high-carbon, fine-grained residue that is produced via pyrolysis{{cite journal |author=Dominic Woolf |author2=James E. Amonette |author3=F. Alayne Street-Perrott |author4=Johannes Lehmann |author5=Stephen Joseph |date=August 2010 |title=Sustainable biochar to mitigate global climate change |journal=Nature Communications |volume=1 |issue=5 |pages=56 |bibcode=2010NatCo...1...56W |doi=10.1038/ncomms1053 |issn=2041-1723 |pmc=2964457 |pmid=20975722}}
• Bioenergy with carbon capture and storage (BECCS): the process of extracting bioenergy from biomass and capturing and storing the carbon, thereby removing it from the atmosphere.{{cite journal |last1=Obersteiner |first1=M. |year=2001 |title=Managing Climate Risk |journal=Science |volume=294 |issue=5543 |pages=786–7 |doi=10.1126/science.294.5543.786b |pmid=11681318 |s2cid=34722068}}
• Direct air capture and carbon storage: a process of capturing carbon dioxide directly from the ambient air (as opposed to capturing from point sources, such as a cement factory or biomass power plant) and generating a concentrated stream of {{CO2}} for sequestration or utilization or production of carbon-neutral fuel and windgas.
• Enhanced weathering: a process that aims to accelerate the natural weathering by spreading finely ground silicate rock, such as basalt, onto surfaces which speeds up chemical reactions between rocks, water, and air. It also removes carbon dioxide ({{CO2}}) from the atmosphere, permanently storing it in solid carbonate minerals or ocean alkalinity.{{Cite web |date=2018-02-19 |title=Guest post: How 'enhanced weathering' could slow climate change and boost crop yields |url=https://www.carbonbrief.org/guest-post-how-enhanced-weathering-could-slow-climate-change-and-boost-crop-yields |url-status=live |archive-url=https://web.archive.org/web/20210908204350/https://www.carbonbrief.org/guest-post-how-enhanced-weathering-could-slow-climate-change-and-boost-crop-yields |archive-date=2021-09-08 |access-date=2021-11-03 |website=Carbon Brief |language=en}} The latter also slows ocean acidification.
• Solar Radiation Management
• Marine cloud brightening: a proposed technique that would make clouds brighter, reflecting a small fraction of incoming sunlight back into space in order to offset anthropogenic global warming.{{Cite book |author=Committee on Geoengineering Climate: Technical Evaluation and Discussion of Impacts |url=http://www.nap.edu/catalog.php?record_id=18988 |title=Climate Intervention: Reflecting Sunlight to Cool Earth |author2=Board on Atmospheric Sciences and Climate |author3=Ocean Studies Board |author4=Division on Earth and Life Studies |author5=National Research Council |publisher=National Academies Press |year=2015 |isbn=978-0-309-31482-4 |access-date=2016-10-21 |archive-url=https://web.archive.org/web/20191214192318/http://www.nap.edu/catalog.php?record_id=18988 |archive-date=2019-12-14 |url-status=live}}
• Mirrors in space (MIS): satellites that are designed to change the amount of solar radiation that impacts the Earth as a form of climate engineering. Since the conception of the idea in 1923, 1929, 1957 and 1978 (Hermann Oberth) and also in the 1980s, space mirrors have mainly been theorized as a way to deflect sunlight to counter global warming and were seriously considered in the 2000s.{{Cite book |last=Oberth |first=Hermann |date=1984 |orig-date=1923 |title=Die Rakete zu den Planetenräumen |language=german |publisher=Michaels-Verlag Germany |pages=87–88}}{{Cite book |last=Oberth |first=Hermann |title=ways to spaceflight |pages=177–506 |url=https://archive.org/details/nasa_techdoc_19720008133 |via=archiv.org |publisher=NASA |access-date=21 December 2017 |language=en |date=1970 |orig-year=1929}}{{Cite book |last=Oberth |first=Hermann |date=1957 |title=Menschen im Weltraum |language=german |publisher=Econ Duesseldorf Germany |pages=125–182}}{{Cite book |last=Oberth |first=Hermann |date=1978 |title=Der Weltraumspiegel |language=german |publisher=Kriterion Bucharest}}{{Cite web |last=Kaufman |first=Rachel |date=August 8, 2012 |title=Could Space Mirrors Stop Global Warming? |url=https://www.livescience.com/22202-space-mirrors-global-warming.html |access-date=2019-11-08 |work=Live Science |language=en}}{{Cite journal |last1=Sánchez |first1=Joan-Pau |last2=McInnes |first2=Colin R. |date=2015-08-26 |title=Optimal Sunshade Configurations for Space-Based Geoengineering near the Sun-Earth L1 Point |journal=PLOS ONE |volume=10 |issue=8 |pages=e0136648 |bibcode=2015PLoSO..1036648S |doi=10.1371/journal.pone.0136648 |issn=1932-6203 |pmc=4550401 |pmid=26309047 |doi-access=free}}
• Stratospheric aerosol injection (SAI): a proposed method to introduce aerosols into the stratosphere to create a cooling effect via global dimming and increased albedo, which occurs naturally from volcanic eruptions.{{Cite journal |last1=Crutzen |first1=P. J. |year=2006 |title=Albedo Enhancement by Stratospheric Sulfur Injections: A Contribution to Resolve a Policy Dilemma? |journal=Climatic Change |volume=77 |issue=3–4 |pages=211–220 |bibcode=2006ClCh...77..211C |doi=10.1007/s10584-006-9101-y |doi-access=free}}

The following methods are not termed climate engineering in the latest IPCC assessment report in 2022{{rp|6–11}} but are included under this umbrella term by other publications on this topic:{{Cite web |title=Chapter 2 : Land–Climate interactions: Special Report on Climate Change and Land |url=https://www.ipcc.ch/srccl/chapter/chapter-2/ |access-date=2023-10-20}}

• Passive daytime radiative cooling: technology that increases the Earth's solar reflectance and thermal emittance in the atmospheric window.{{Cite journal |last1=Zevenhovena |first1=Ron |last2=Fält |first2=Martin |date=June 2018 |title=Radiative cooling through the atmospheric window: A third, less intrusive geoengineering approach |url=https://www.sciencedirect.com/science/article/abs/pii/S0360544218304936 |journal=Energy |volume=152 |page=27 |bibcode=2018Ene...152...27Z |doi=10.1016/j.energy.2018.03.084 |quote=An alternative, third geoengineering approach would be enhanced cooling by thermal radiation from the Earth's surface into space. |via=Elsevier Science Direct}}{{Cite journal |last1=Wang |first1=Tong |last2=Wu |first2=Yi |last3=Shi |first3=Lan |last4=Hu |first4=Xinhua |last5=Chen |first5=Min |last6=Wu |first6=Limin |date=2021 |title=A structural polymer for highly efficient all-day passive radiative cooling |journal=Nature Communications |volume=12 |issue=365 |page=365 |doi=10.1038/s41467-020-20646-7 |pmc=7809060 |pmid=33446648 |quote=One possibly alternative approach is passive radiative cooling—a sky-facing surface on the Earth spontaneously cools by radiating heat to the ultracold outer space through the atmosphere’s longwave infrared (LWIR) transparency window (λ ~ 8–13 μm).}}{{Cite journal |last1=Chen |first1=Meijie |last2=Pang |first2=Dan |last3=Chen |first3=Xingyu |last4=Yan |first4=Hongjie |last5=Yang |first5=Yuan |year=2022 |title=Passive daytime radiative cooling: Fundamentals, material designs, and applications |journal=EcoMat |volume=4 |doi=10.1002/eom2.12153 |s2cid=240331557 |quote=Passive daytime radiative cooling dissipates terrestrial heat to the extremely cold outer space without using any energy input or producing pollution. It has the potential to simultaneously alleviate the two major problems of energy crisis and global warming. |doi-access=free}}
• Ground-level albedo modification: increasing Earth's albedo by modifying objects on the Earth's surface. Examples include planting light-colored plants to help with reflecting sunlight back into space.{{Cite journal |last1=Wang |first1=Zhuosen |last2=Schaaf |first2=Crystal B. |last3=Sun |first3=Qingsong |last4=Kim |first4=JiHyun |last5=Erb |first5=Angela M. |last6=Gao |first6=Feng |last7=Román |first7=Miguel O. |last8=Yang |first8=Yun |last9=Petroy |first9=Shelley |last10=Taylor |first10=Jeffrey R. |last11=Masek |first11=Jeffrey G. |last12=Morisette |first12=Jeffrey T. |last13=Zhang |first13=Xiaoyang |last14=Papuga |first14=Shirley A. |date=2017-07-01 |title=Monitoring land surface albedo and vegetation dynamics using high spatial and temporal resolution synthetic time series from Landsat and the MODIS BRDF/NBAR/albedo product |journal=International Journal of Applied Earth Observation and Geoinformation |language=en |volume=59 |pages=104–117 |doi=10.1016/j.jag.2017.03.008 |issn=1569-8432 |pmc=7641169 |pmid=33154713|bibcode=2017IJAEO..59..104W }}
• Glacier stabilization: interventions to slow down or prevent sea level rise caused by the collapse of notable marine-terminating glaciers, such as Jakobshavn Glacier in Greenland or Thwaites Glacier and Pine Island Glacier in Antarctica. It may be possible to bolster some glaciers directly,{{Cite journal |last1=Wolovick |first1=Michael J. |last2=Moore |first2=John C. |date=20 September 2018 |title=Stopping the flood: could we use targeted geoengineering to mitigate sea level rise? |url=https://tc.copernicus.org/articles/16/397/2022/ |journal=The Cryosphere |volume=12 |issue=9 |pages=2955–2967 |language=en |doi=10.5194/tc-12-2955-2018 |doi-access=free |bibcode=2018TCry...12.2955W }} but blocking the flow of ever-warming ocean water at a distance, allowing it more time to mix with the cooler water around the glacier, is likely to be far more effective.{{Cite journal |last1=Wolovick |first1=Michael |last2=Moore |first2=John |last3=Keefer |first3=Bowie |date=27 March 2023 |title=Feasibility of ice sheet conservation using seabed anchored curtains |url=https://academic.oup.com/pnasnexus/article/2/4/pgad103/7087219 |journal=PNAS Nexus |volume=2 |issue=3 |pages=pgad053 |language=en |doi=10.1093/pnasnexus/pgad053 |pmid=37007716 |pmc=10062297 }}{{Cite journal |last1=Wolovick |first1=Michael |last2=Moore |first2=John |last3=Keefer |first3=Bowie |date=27 March 2023 |title=The potential for stabilizing Amundsen Sea glaciers via underwater curtains |url=https://academic.oup.com/pnasnexus/article/2/4/pgad103/7087219 |journal=PNAS Nexus |volume=2 |issue=4 |pages=pgad103 |language=en |doi=10.1093/pnasnexus/pgad103 |pmid=37091546 |pmc=10118300 }}{{Cite web|title=The radical intervention that might save the "doomsday" glacier|url=https://www.technologyreview.com/2022/01/14/1043523/save-doomsday-thwaites-glacier-antarctica/|access-date=2022-01-14|website=MIT Technology Review|language=en}}
• Ocean geoengineering (adding material such as lime or iron to the ocean to affect its ability to sequester carbon dioxide).

{{excerpt|carbon dioxide removal|paragraphs=1-2}}

File:SPICE_SRM_overview.jpg

{{excerpt|Solar geoengineering|paragraphs=1-2|file=no}}

Enhancing the solar reflectance and thermal emissivity of Earth in the atmospheric window through passive daytime radiative cooling has been proposed as an alternative or "third approach" to climate engineering{{Cite journal |last1=Wang |first1=Tong |last2=Wu |first2=Yi |last3=Shi |first3=Lan |last4=Hu |first4=Xinhua |last5=Chen |first5=Min |last6=Wu |first6=Limin |date=2021 |title=A structural polymer for highly efficient all-day passive radiative cooling |journal=Nature Communications |volume=12 |issue=365 |page=365 |doi=10.1038/s41467-020-20646-7 |pmid=33446648 |pmc=7809060 |quote=One possibly alternative approach is passive radiative cooling—a sky-facing surface on the Earth spontaneously cools by radiating heat to the ultracold outer space through the atmosphere’s longwave infrared (LWIR) transparency window (λ ~ 8–13 μm). }} that is "less intrusive" and more predictable or reversible than stratospheric aerosol injection.{{Cite journal |last=Munday |first=Jeremy |date=2019 |title=Tackling Climate Change through Radiative Cooling |journal=Joule |volume=3 |issue=9 |pages=2057–2060 |doi=10.1016/j.joule.2019.07.010 |quote=A reduction in solar absorption is usually proposed through the injection of reflective aerosols into the atmosphere; however, serious concerns have been raised regarding side effects of these forms of geoengineering and our ability to undo any of the climatic changes we create. |s2cid=201590290|doi-access=free |bibcode=2019Joule...3.2057M }}

{{excerpt|Passive daytime radiative cooling|paragraphs=1-2}}File:A technofix for the climate- Marine geoengineering.webm

{{Main|Carbon sequestration#Sequestration techniques in oceans}}Ocean geoengineering involves modifying the ocean to reduce the impacts of rising temperature. One approach is to add material such as lime or iron to the ocean to increase its ability to support marine life and/or sequester {{Chem|CO|2}}. In 2021 the US National Academies of Sciences, Engineering, and Medicine (NASEM) requested $2.5 billion funds for research in the following decade, specifically including field tests.{{Cite web |last=Voosen |first=Paul |date=16 December 2022 |title=Ocean geoengineering scheme aces its first field test |url=https://www.science.org/content/article/ocean-geoengineering-scheme-aces-its-first-field-test |access-date=2022-12-19 |website=www.science.org |language=en}}

Another idea is to reduce sea level rise by installing underwater "curtains" to protect Antarctic glaciers from warming waters, or by drilling holes in ice to pump out water and heat.{{Cite news |last=Richter |first=Hannah |date=12 July 2024 |title=To avoid sea level rise, some researchers want to build barriers around the world's most vulnerable glaciers |url=https://www.science.org/content/article/avoid-sea-level-rise-some-researchers-want-build-barriers-around-world-s-most |work=Science magazine}}

{{Main|Carbon sequestration#Adding bases to neutralize acids|Ocean acidification#Carbon removal technologies which add alkalinity}}

Enriching seawater with calcium hydroxide (lime) has been reported to lower ocean acidity, which reduces pressure on marine life such as oysters and absorbs {{Chem|CO|2}}. The added lime raised the water's pH, capturing {{Chem|CO|2}} in the form of calcium bicarbonate or as carbonate deposited in mollusk shells. Lime is produced in volume for the cement industry. This was assessed in 2022 in an experiment in Apalachicola, Florida in an attempt to halt declining oyster populations. pH levels increased modestly, as {{Chem|CO|2}} was reduced by 70 ppm.

A 2014 experiment added sodium hydroxide (lye) to part of Australia's Great Barrier Reef. It raised pH levels to nearly preindustrial levels.

However, producing alkaline materials typically releases large amounts of {{Chem|CO|2}}, partially offsetting the sequestration. Alkaline additives become diluted and dispersed in one month, without durable effects, such that if necessary, the program could be ended without leaving long-term effects.

{{Main|Ocean fertilization}}

Enhancing the natural marine sulfur cycle by fertilizing a small portion with iron—typically considered to be a greenhouse gas remediation method—may also increase the reflection of sunlight.{{Cite journal |last1=Wingenter |first1=Oliver W. |last2=Haase |first2=Karl B. |last3=Strutton |first3=Peter |last4=Friederich |first4=Gernot |last5=Meinardi |first5=Simone |last6=Blake |first6=Donald R. |last7=Rowland |first7=F. Sherwood |date=8 June 2004 |title=Changing concentrations of CO, CH₄, C₅H₈, CH₃Br, CH₃I, and dimethyl sulfide during the Southern Ocean Iron Enrichment Experiments |journal=Proceedings of the National Academy of Sciences of the United States of America |language=en |volume=101 |issue=23 |pages=8537–8541 |bibcode=2004PNAS..101.8537W |doi=10.1073/pnas.0402744101 |issn=0027-8424 |pmc=423229 |pmid=15173582 |doi-access=free}}{{cite journal |last1=Wingenter |first1=Oliver W. |last2=Elliot |first2=Scott M. |last3=Blake |first3=Donald R. |date=November 2007 |title=New Directions: Enhancing the natural sulfur cycle to slow global warming |url=https://escholarship.org/uc/item/3t2791f1 |url-status=live |journal=Atmospheric Environment |volume=41 |issue=34 |pages=7373–5 |bibcode=2007AtmEn..41.7373W |doi=10.1016/j.atmosenv.2007.07.021 |s2cid=43279436 |archive-url=https://web.archive.org/web/20200813061020/https://escholarship.org/uc/item/3t2791f1 |archive-date=13 August 2020 |access-date=18 September 2020}} Such fertilization, especially in the Southern Ocean, would enhance dimethyl sulfide production and consequently cloud reflectivity. This could potentially be used as regional SRM, to slow Antarctic ice from melting.{{Citation needed|date=November 2020}} Such techniques also tend to sequester carbon, but the enhancement of cloud albedo also appears to be a likely effect.

{{excerpt|Iron fertilization|paragraphs=1|file=no}}

Another 2022 experiment attempted to sequester carbon using giant kelp planted off the Namibian coast. Whilst this approach has been called ocean geoengineering by the researchers it is just another form of carbon dioxide removal via sequestration. Another term that is used to describe this process is blue carbon management and also marine geoengineering.

File:Wolovick2018_Thwaites_sill_timelines.png

{{excerpt|Thwaites Glacier#Engineering options for stabilization|paragraphs=1,2|file=no}}

{{See also|Solar radiation modification#Scientific uncertainties and risks}}

Interventions at large scale run a greater risk of unintended disruptions of natural systems, alongside a greater potential for reducing the risks of warming. This raises a question of whether climate interventions might be more or less damaging than the climate damage that they offset.

Matthew Watson, of the University of Bristol, led a £5m research study into the potential adverse effects of climate engineering and said in 2014, "We are sleepwalking to a disaster with climate change. Cutting emissions is undoubtedly the thing we should be focusing on but it seems to be failing. Although geoengineering is terrifying to many people, and I include myself in this, [its feasibility and safety] are questions that have to be answered".{{Cite news |last=Carrington |first=Damian |date=2014-11-26 |title=Reflecting sunlight into space has terrifying consequences, say scientists |url=https://www.theguardian.com/environment/2014/nov/26/geoengineering-could-offer-solution-last-resort-climate-change |access-date=2019-11-08 |work=The Guardian |language=en-GB |issn=0261-3077}} University of Oxford Professor Steve Rayner is also worried about the adverse effects of climate engineering, especially the potential for people to be too positive about the effects and stop trying to slow the actual problem of climate change. Though, he says there is a potential reason to doing climate engineering: "People decry doing [climate engineering] as a band aid, but band aids are useful when you are healing".

Climate engineering may reduce the urgency of reducing carbon emissions, a form of moral hazard.{{cite news |last=Adam |first=David |date=1 September 2008 |title=Extreme and risky action the only way to tackle global warming, say scientists |work=The Guardian |url=https://www.theguardian.com/environment/2008/sep/01/climatechange.scienceofclimatechange2 |url-status=live |access-date=2009-05-23 |archive-url=https://web.archive.org/web/20190806230902/https://www.theguardian.com/environment/2008/sep/01/climatechange.scienceofclimatechange2 |archive-date=2019-08-06}} Also, some approaches would have only temporary effects, which implies rapid rebound if they are not sustained.{{cite web |year=2009 |title=Geoengineering |url=http://www.irgc.org/geoengineering |url-status=dead |archive-url=https://web.archive.org/web/20091203132630/http://www.irgc.org/geoengineering |archive-date=2009-12-03 |access-date=2009-10-07 |publisher=International Risk Governance Council}} The Union of Concerned Scientists points to the concern that the use of climate engineering technology might become an excuse not to address the root causes of climate change.{{Cite web |date=Dec 4, 2020 |title=What Is Solar Geoengineering? |url=https://www.ucsusa.org/resources/what-solar-geoengineering |website=The Union of Concerned Scientists}} However, several public opinion surveys and focus groups reported either a desire to increase emission cuts in the presence of climate engineering, or no effect.{{Cite journal |last1=Kahan |first1=Dan M. |last2=Jenkins-Smith |first2=Hank |last3=Tarantola |first3=Tor |last4=Silva |first4=Carol L. |last5=Braman |first5=Donald |date=2015-03-01 |title=Geoengineering and Climate Change Polarization Testing a Two-Channel Model of Science Communication |journal=The Annals of the American Academy of Political and Social Science |volume=658 |issue=1 |pages=192–222 |doi=10.1177/0002716214559002 |issn=0002-7162 |s2cid=149147565}}{{Cite journal |last1=Wibeck |first1=Victoria |last2=Hansson |first2=Anders |last3=Anshelm |first3=Jonas |date=2015-05-01 |title=Questioning the technological fix to climate change{{Snd}} Lay sense-making of geoengineering in Sweden |url=http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119732 |journal=Energy Research & Social Science |volume=7 |pages=23–30 |doi=10.1016/j.erss.2015.03.001|bibcode=2015ERSS....7...23W }}{{Cite journal |last1=Merk |first1=Christine |last2=Pönitzsch |first2=Gert |last3=Kniebes |first3=Carola |last4=Rehdanz |first4=Katrin |last5=Schmidt |first5=Ulrich |date=2015-02-10 |title=Exploring public perceptions of stratospheric sulfate injection |journal=Climatic Change |volume=130 |issue=2 |pages=299–312 |bibcode=2015ClCh..130..299M |doi=10.1007/s10584-014-1317-7 |issn=0165-0009 |s2cid=154196324}} Other modelling work suggests that the prospect of climate engineering may in fact increase the likelihood of emissions reduction.{{Cite journal |last=Reynolds |first=Jesse |date=2015-08-01 |title=A critical examination of the climate engineering moral hazard and risk compensation concern |journal=The Anthropocene Review |volume=2 |issue=2 |pages=174–191 |doi=10.1177/2053019614554304 |bibcode=2015AntRv...2..174R |issn=2053-0196 |s2cid=59407485}}{{Cite journal |last=Morrow |first=David R. |date=2014-12-28 |title=Ethical aspects of the mitigation obstruction argument against climate engineering research |journal=Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences |volume=372 |issue=2031 |pages=20140062 |bibcode=2014RSPTA.37240062M |doi=10.1098/rsta.2014.0062 |issn=1364-503X |pmid=25404676 |doi-access=free}}{{Cite journal |last=Urpelainen |first=Johannes |date=2012-02-10 |title=Geoengineering and global warming: a strategic perspective |journal=International Environmental Agreements: Politics, Law and Economics |volume=12 |issue=4 |pages=375–389 |doi=10.1007/s10784-012-9167-0 |bibcode=2012IEAPL..12..375U |issn=1567-9764 |s2cid=154422202}}{{Cite journal |last=Moreno-Cruz |first=Juan B. |date=2015-08-01 |title=Mitigation and the geoengineering threat |journal=Resource and Energy Economics |volume=41 |pages=248–263 |doi=10.1016/j.reseneeco.2015.06.001|bibcode=2015REEco..41..248M |hdl=1853/44254 |hdl-access=free }}

Climate engineering also raises moral questions about the relationship between humans and their environment, and under what conditions humans have the right to deliberately change the climate. Some religious traditions express views on the relationship between humans and their surroundings that either encourage or discourage explicit actions to affect climate, depending on the objective. For example, using climate engineering to stabilize temperatures may be seen as an example of stewardship and therefore encouraged. Conversely, climate engineering may be discouraged if is perceived as human overconfidence and hubris.{{cite journal |last1=Clingerman |first1=F. |last2=O'Brien |first2=K. |year=2014 |title=Playing God: why religion belongs in the climate engineering debate |journal=Bulletin of the Atomic Scientists |volume=70 |issue=3 |pages=27–37 |bibcode=2014BuAtS..70c..27C |doi=10.1177/0096340214531181 |s2cid=143742343}}

{{See also|Solar radiation modification#Governance and policy issues}}

Governance issues relating to carbon dioxide removal are distinct from those surrounding CE. The key governance problem for carbon dioxide removal (as with emissions reductions) is making sure actors do enough of it (minimizing "free riders"), whereas the key governance issue for CE is making sure actors do not do it too much (managing "free drivers").{{cite journal |last1=Weitzman |first1=Martin L. |year=2015 |title=A Voting Architecture for the Governance of Free-Driver Externalities, with Application to Geoengineering |url=http://nrs.harvard.edu/urn-3:HUL.InstRepos:17368469 |url-status=live |journal=The Scandinavian Journal of Economics |volume=117 |issue=4 |pages=1049–1068 |doi=10.1111/sjoe.12120 |archive-url=https://web.archive.org/web/20200609205824/https://dash.harvard.edu/handle/1/17368469 |archive-date=2020-06-09 |access-date=2019-01-30 |s2cid=2991157}}

No universally agreed framework for the regulation of CE activity or research has been established. Scholars at the Oxford Martin School at Oxford University proposed a set of principles to guide climate engineering research and use. The short version is:{{Cite journal |last1=Rayner |first1=S. |last2=Heyward |first2=C. |last3=Kruger |first3=T. |last4=Pidgeon |first4=N. |last5=Redgwell |first5=C. |last6=Savulescu |first6=J. |year=2013 |title=The Oxford Principles |journal=Climatic Change |volume=121 |issue=3 |pages=499–512 |bibcode=2013ClCh..121..499R |doi=10.1007/s10584-012-0675-2 |s2cid=55553948}}

• Regulate as a public good.
• Public participation in decision-making
• Disclose research and open publication of results
• Independent assessment of impacts
• Governance before deployment

These principles were endorsed by the House of Commons of the United Kingdom Science and Technology Select Committee on "The Regulation of Geoengineering".{{Cite web |author=Oxford Geoengineering Programme |title=Oxford Geoengineering Programme // History of the Oxford Principles |url=http://www.geoengineering.ox.ac.uk/oxford-principles/history/ |url-status=live |archive-url=https://web.archive.org/web/20160304040635/http://www.geoengineering.ox.ac.uk/oxford-principles/history/ |archive-date=2016-03-04 |access-date=2016-02-03 |website=www.geoengineering.ox.ac.uk}}{{Cite news |date=March 31, 2010 |title=We all want to change the world |newspaper=The Economist |url=https://www.economist.com/science-and-technology/2010/03/31/we-all-want-to-change-the-world |url-status=live |url-access=subscription |access-date=October 19, 2019 |archive-url=https://web.archive.org/web/20191019142946/https://www.economist.com/science-and-technology/2010/03/31/we-all-want-to-change-the-world |archive-date=October 19, 2019}}

The Asilomar International Conference on Climate Intervention Technologies was convened to identify and develop risk reduction guidelines for climate intervention experimentation.{{cite web |title=Conference Home |url=http://climateresponsefund.org/index.php?option=com_content&view=article&id=137&Itemid=81 |url-status=dead |archive-url=https://web.archive.org/web/20121016101517/http://climateresponsefund.org/index.php?option=com_content&view=article&id=137&Itemid=81 |archive-date=2012-10-16 |access-date=2012-09-06 |publisher=Climateresponsefund.org}}

The Parties to the Convention on Biological Diversity made three decisions on what they termed "climate-related geo-engineering." A decision in 2010 called on countries to refrain from "climate-related geo-engineering activities that may affect biodiversity" until they are governed, are scientifically justified, and associated risks have been considered.{{Cite web |last=Unit |first=Biosafety |title=COP Decision |url=https://www.cbd.int/decision/cop/?id=12299 |url-status=live |archive-url=https://web.archive.org/web/20210607152529/https://www.cbd.int/decision/cop/?id=12299 |archive-date=2021-06-07 |access-date=2021-06-07 |website=www.cbd.int |language=en}} Some critics describe this as a "de facto moratorium,"{{Cite journal |last1=Herkenrath |first1=Peter |last2=Harrison |first2=Jeremy |date=January 2011 |title=The 10th meeting of the Conference of the Parties to the Convention on Biological Diversity – a breakthrough for biodiversity? |journal=Oryx |language=en |volume=45 |issue=1 |pages=1–2 |doi=10.1017/S0030605310001663 |issn=0030-6053 |doi-access=free}} but the Secretariat of the Convention on Biological Diversity calls it a “non-binding normative framework.”{{Cite book |url=https://www.worldcat.org/oclc/889257942 |title=Geoengineering in relation to the Convention on biological diversity : technical and regulatory matters. |date=2012 |first=Phillip |last=Williamson |first2=Ralph |last2=Bodle |publisher=Secretariat of the Convention on Biological Diversity |isbn=978-9292254292 |location=Montréal, Québec |oclc=889257942}} Legal scholars Scott and Reynolds separately reject this characterization.{{Cite journal |last=Scott |first=Karen |date=2013-01-01 |title=International Law in the Anthropocene: Responding to the Geoengineering Challenge |url=https://repository.law.umich.edu/mjil/vol34/iss2/2 |url-status=live |journal=Michigan Journal of International Law |volume=34 |issue=2 |pages=309–358 |issn=1052-2867 |archive-url=https://web.archive.org/web/20210611114000/https://repository.law.umich.edu/mjil/vol34/iss2/2/ |archive-date=2021-06-11 |access-date=2021-06-11}}{{Cite journal |last1=Reynolds |first1=Jesse L. |last2=Parker |first2=Andy |last3=Irvine |first3=Peter |date=December 2016 |title=Five solar geoengineering tropes that have outstayed their welcome: Five solar geoengineering tropes |url=http://doi.wiley.com/10.1002/2016EF000416 |journal=Earth's Future |language=en |volume=4 |issue=12 |pages=562–568 |doi=10.1002/2016EF000416|s2cid=36263104 }} The 2016 decision called for "more transdisciplinary research and sharing of knowledge among appropriate institutions is needed in order to better understand the impacts."{{Cite web |title=Convention on Biological Diversity |url=https://www.cbd.int/decisions/cop/13/14 |url-status=live |archive-url=https://web.archive.org/web/20210225075601/https://www.cbd.int/decisions/cop/13/14 |archive-date=2021-02-25 |access-date=2021-06-07 |website=Convention on Biological Diversity |language=en}}

A large 2018 study used an online survey to investigate public perceptions of six climate engineering methods in the United States, United Kingdom, Australia, and New Zealand.{{Cite journal |last1=Carlisle |first1=Daniel P. |last2=Feetham |first2=Pamela M. |last3=Wright |first3=Malcolm J. |last4=Teagle |first4=Damon A. H. |date=2020-04-12 |title=The public remain uninformed and wary of climate engineering |url=https://eprints.soton.ac.uk/440717/1/Thepublic_remain_uninformed.pdf |url-status=live |journal=Climatic Change |language=en |volume=160 |issue=2 |pages=303–322 |bibcode=2020ClCh..160..303C |doi=10.1007/s10584-020-02706-5 |issn=1573-1480 |archive-url=https://web.archive.org/web/20210614062101/https://eprints.soton.ac.uk/440717/1/Thepublic_remain_uninformed.pdf |archive-date=2021-06-14 |access-date=2021-05-18 |s2cid=215731777}} Public awareness of climate engineering was low; less than a fifth of respondents reported prior knowledge. Perceptions of the six climate engineering methods proposed (three from the carbon dioxide removal group and three from the solar radiation modification group) were largely negative and frequently associated with attributes like 'risky', 'artificial' and 'unknown effects'. Carbon dioxide removal methods were preferred over solar radiation modification. Public perceptions were remarkably stable with only minor differences between the different countries in the surveys.{{Cite journal |last1=Wright |first1=Malcolm J. |last2=Teagle |first2=Damon A. H. |last3=Feetham |first3=Pamela M. |date=February 2014 |title=A quantitative evaluation of the public response to climate engineering |url=https://www.nature.com/articles/nclimate2087 |url-status=live |journal=Nature Climate Change |language=en |volume=4 |issue=2 |pages=106–110 |bibcode=2014NatCC...4..106W |doi=10.1038/nclimate2087 |issn=1758-6798 |archive-url=https://web.archive.org/web/20200728153000/https://www.nature.com/articles/nclimate2087 |archive-date=2020-07-28 |access-date=2020-05-22}}

Some environmental organizations (such as Friends of the Earth and Greenpeace) have been reluctant to endorse or oppose solar radiation modification, but are often more supportive of nature-based carbon dioxide removal projects, such as afforestation and peatland restoration.{{cite news |last=Parr |first=Doug |date=1 September 2008 |title=Geo-engineering is no solution to climate change |work=Guardian Newspaper |location=London |url=https://www.theguardian.com/environment/2008/sep/01/climatechange.scienceofclimatechange1 |url-status=live |access-date=2009-05-23 |archive-url=https://web.archive.org/web/20180820234933/https://www.theguardian.com/environment/2008/sep/01/climatechange.scienceofclimatechange1 |archive-date=2018-08-20}}

{{See also|Solar radiation modification#Research funding}}

Several organizations have investigated climate engineering with a view to evaluating its potential, including the US Congress,{{cite web |last=Bullis |first=Kevin |title=U.S. Congress Considers Geoengineering |url=http://www.technologyreview.com/view/416187/us-congress-considers-geoengineering/ |url-status=live |archive-url=https://web.archive.org/web/20130126213315/http://www.technologyreview.com/view/416187/us-congress-considers-geoengineering/ |archive-date=26 January 2013 |access-date=26 December 2012 |work=MIT Technology Review|date=6 November 2009 }} the US National Academy of Sciences, Engineering, and Medicine,{{Cite web |title=Climate Intervention Reports » Climate Change at the National Academies of Sciences, Engineering, and Medicine |url=https://nas-sites.org/americasclimatechoices/other-reports-on-climate-change/2015-2/climate-intervention-reports/ |url-status=live |archive-url=https://web.archive.org/web/20160729015758/http://nas-sites.org/americasclimatechoices/other-reports-on-climate-change/2015-2/climate-intervention-reports/ |archive-date=2016-07-29 |access-date=2015-11-02 |website=nas-sites.org}} the Royal Society,{{cite press release |title=Stop emitting CO2 or geoengineering could be our only hope |url=http://royalsociety.org/Stop-emitting-CO2-or-geoengineering-could-be-our-only-hope/ |date=28 August 2009 |publisher=The Royal Society |access-date=14 June 2011 |archive-date=24 June 2011 |archive-url=https://web.archive.org/web/20110624054716/http://royalsociety.org/Stop-emitting-CO2-or-geoengineering-could-be-our-only-hope/ |url-status=live}} the UK Parliament,{{cite web |date=March 2009 |title=Geo-engineering research |url=https://researchbriefings.files.parliament.uk/documents/POST-PN-327/POST-PN-327.pdf |access-date=2022-09-11 |work=Postnote |publisher=Parliamentary Office of Science and Technology}} the Institution of Mechanical Engineers,{{cite web |title=Geo-engineering{{Snd}} Giving us the time to act? |url=http://www.imeche.org/Libraries/Key_Themes/IMechEGeoengineeringReport.sflb.ashx |url-status=dead |archive-url=https://web.archive.org/web/20110722191723/http://www.imeche.org/Libraries/Key_Themes/IMechEGeoengineeringReport.sflb.ashx |archive-date=2011-07-22 |access-date=2011-03-12 |publisher=I Mech E}} and the Intergovernmental Panel on Climate Change.

In 2009, the Royal Society in the UK reviewed a wide range of proposed climate engineering methods and evaluated them in terms of effectiveness, affordability, timeliness, and safety (assigning qualitative estimates in each assessment). The key recommendations reports were that "Parties to the UNFCCC should make increased efforts towards mitigating and adapting to climate change, and in particular to agreeing to global emissions reductions", and that "[nothing] now known about geoengineering options gives any reason to diminish these efforts".{{cite report |url=http://royalsociety.org/uploadedFiles/Royal_Society_Content/policy/publications/2009/8693.pdf |title=Geoengineering the Climate: Science, Governance and Uncertainty |author=Working group |date=2009 |publisher=The Royal Society |location=London |page=1 |isbn=978-0-85403-773-5 |id=RS1636 |access-date=2011-12-01 |archive-url=https://web.archive.org/web/20140312031514/http://royalsociety.org/uploadedfiles/royal_society_content/policy/publications/2009/8693.pdf |archive-date=2014-03-12 |url-status=live}} Nonetheless, the report also recommended that "research and development of climate engineering options should be undertaken to investigate whether low-risk methods can be made available if it becomes necessary to reduce the rate of warming this century".

In 2009, a review examined the scientific plausibility of proposed methods rather than the practical considerations such as engineering feasibility or economic cost. The authors found that "[air] capture and storage shows the greatest potential, combined with afforestation, reforestation and bio-char production", and noted that "other suggestions that have received considerable media attention, in particular, "ocean pipes" appear to be ineffective".{{cite journal |last=Lenton |first=T.M. |author2=Vaughan, N.E. |year=2009 |title=The radiative forcing potential of different climate geoengineering options |url=http://www.atmos-chem-phys.net/9/5539/2009/acp-9-5539-2009.html |url-status=live |journal=Atmospheric Chemistry and Physics |volume=9 |issue=15 |pages=5539–5561 |bibcode=2009ACP.....9.5539L |doi=10.5194/acp-9-5539-2009 |archive-url=https://web.archive.org/web/20191214043800/https://www.atmos-chem-phys.net/9/5539/2009/acp-9-5539-2009.html |archive-date=2019-12-14 |access-date=2009-09-04 |doi-access=free}} They concluded that "[climate] geoengineering is best considered as a potential complement to the mitigation of {{co2}} emissions, rather than as an alternative to it".

The IMechE report examined a small subset of proposed methods (air capture, urban albedo and algal-based {{co2}} capture techniques), and its main conclusions in 2011 were that climate engineering should be researched and trialed at the small scale alongside a wider decarbonization of the economy.

In 2015, the US National Academy of Sciences, Engineering, and Medicine concluded a 21-month project to study the potential impacts, benefits, and costs of climate engineering. The differences between these two classes of climate engineering "led the committee to evaluate the two types of approaches separately in companion reports, a distinction it hopes carries over to future scientific and policy discussions."{{Cite press release |title=Climate Intervention Is Not a Replacement for Reducing Carbon Emissions; Proposed Intervention Techniques Not Ready for Wide-Scale Deployment |url=http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=02102015 |website=NEWS from the national academies |date=Feb 10, 2015 |access-date=2015-11-24 |archive-date=2015-11-17 |archive-url=https://web.archive.org/web/20151117032144/http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=02102015 |url-status=live}}{{Cite book |author=National Research Council |title=Climate Intervention: Reflecting Sunlight to Cool Earth |date=2017 |publisher=The National Academies Press |isbn=978-0-309-31482-4 |doi=10.17226/18988}} Ebook: {{ISBN|978-0-309-31485-5}}.{{Cite book |author=National Research Council |url=https://www.nap.edu/catalog/18805/climate-intervention-carbon-dioxide-removal-and-reliable-sequestration |title=Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration |date=2015 |isbn=978-0-309-30529-7 |language=en |doi=10.17226/18805 |access-date=2018-08-20 |archive-url=https://web.archive.org/web/20180821031740/https://www.nap.edu/catalog/18805/climate-intervention-carbon-dioxide-removal-and-reliable-sequestration |archive-date=2018-08-21 |url-status=live}} The resulting study titled Climate Intervention was released in February 2015 and consists of two volumes: Reflecting Sunlight to Cool Earth{{Cite book |author=National Research Council |url=https://www.nap.edu/catalog/18988/climate-intervention-reflecting-sunlight-to-cool-earth |title=Climate Intervention: Reflecting Sunlight to Cool Earth |year=2015 |publisher=National Academies Press |isbn=978-0-309-31482-4 |language=en |access-date=2018-08-20 |archive-url=https://web.archive.org/web/20191214192318/http://www.nap.edu/catalog.php?record_id=18988 |archive-date=2019-12-14 |url-status=live}} and Carbon Dioxide Removal and Reliable Sequestration.{{Cite book |author=National Research Council |url=https://www.nap.edu/catalog/18805/climate-intervention-carbon-dioxide-removal-and-reliable-sequestration |title=Climate Intervention: Carbon Dioxide Removal and Reliable Sequestration |year=2015 |publisher=National Academies Press |isbn=978-0-309-30529-7 |language=en |access-date=2018-08-20 |archive-url=https://web.archive.org/web/20180821031740/https://www.nap.edu/catalog/18805/climate-intervention-carbon-dioxide-removal-and-reliable-sequestration |archive-date=2018-08-21 |url-status=live}}

In June 2023 the US government released a report that recommended conducting research on stratospheric aerosol injection and marine cloud brightening.{{Cite web |last=Hanley |first=Steve |date=2023-07-03 |title=US & EU Quietly Begin To Discuss Geoengineering |url=https://cleantechnica.com/2023/07/03/us-eu-quietly-begin-to-discuss-geoengineering/ |access-date=2023-07-06 |website=CleanTechnica |language=en-US}}

As of 2024 the Coastal Atmospheric Aerosol Research and Engagement (CAARE) project was launching sea salt into the marine sky in an effort to increase cloud "brightness" (reflective capacity). The sea salt is launched from the USS Hornet Sea, Air & Space Museum (based on the project's regulatory filings).{{Cite web |title=Marine Cloud Brightening Program studies clouds, aerosols and pathways to reduce climate risks |url=https://environment.uw.edu/news/2024/04/marine-cloud-brightening-program-studies-clouds-aerosols-and-pathways-to-reduce-climate-risks |access-date=2024-04-08 |website=College of the Environment |language=en-US}}

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