Climate engineering
Deliberate and large-scale intervention in Earth's climate system From Wikipedia, the free encyclopedia
Climate engineering (or geoengineering, climate intervention[1]) is the intentional large-scale alteration of the planetary environment to counteract anthropogenic climate change.[2][3] The term has been used as an umbrella term for carbon dioxide removal, weather as a weapon, reduction of pole ice and solar radiation modification when applied at a planetary scale.[4]: 168 However, these two processes have very different characteristics, and are now often discussed separately.[4]: 168 [5] Carbon dioxide removal techniques remove carbon dioxide from the atmosphere, and are part of climate change mitigation. Solar radiation modification is the reflection of some sunlight (solar radiation) back to space to cool the earth.[6] Some publications include passive radiative cooling as a climate engineering technology. The media tends to also use climate engineering for other technologies such as glacier stabilization, ocean liming, and iron fertilization of oceans. The latter would modify carbon sequestration processes that take place in oceans.
Some types of climate engineering are highly controversial due to the large uncertainties around effectiveness, side effects and unforeseen consequences.[7] Interventions at large scale run a greater risk of unintended disruptions of natural systems, resulting in a dilemma that such disruptions might be more damaging than the climate damage that they offset.[8] However, the risks of such interventions must be seen in the context of the trajectory of climate change without them.[9][8][10]
History and terminology
Geoengineering has been used as an umbrella term for both large-scale CDR and SRM.[4]: 168 However, these two methods have distinct geophysical characteristics, which is why the Intergovernmental Panel on Climate Change no longer uses this term.[4]: 168 [5][11]: 550 More recently, large-scale mechanical and engineering approaches to slow the loss of polar and alpine ice have received attention and could satisfy common definitions of geoengineering. Other terms include climate engineering and climate intervention.
Several organizations have investigated geoengineering with a view to evaluating its potential, including the US National Academies of Sciences, Engineering, and Medicine,[12][13] the Royal Society,[2] and the UN Educational, Scientific and Cultural Organization (UNESCO).[14]
Methods
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Perspective
Carbon dioxide removal
Carbon dioxide removal (CDR) is a process in which carbon dioxide (CO2) is removed from the atmosphere by deliberate human activities and durably stored in geological, terrestrial, or ocean reservoirs, or in products.[17]: 2221 This process is also known as carbon removal, greenhouse gas removal or negative emissions. CDR is more and more often integrated into climate policy, as an element of climate change mitigation strategies.[18][19] Achieving net zero emissions will require first and foremost deep and sustained cuts in emissions, and then—in addition—the use of CDR ("CDR is what puts the net into net zero emissions" [20]). In the future, CDR may be able to counterbalance emissions that are technically difficult to eliminate, such as some agricultural and industrial emissions.[21]: 114
CDR includes methods that are implemented on land or in aquatic systems. Land-based methods include afforestation, reforestation, agricultural practices that sequester carbon in soils (carbon farming), bioenergy with carbon capture and storage (BECCS), and direct air capture combined with storage.[21][22] There are also CDR methods that use oceans and other water bodies. Those are called ocean fertilization, ocean alkalinity enhancement,[23] wetland restoration and blue carbon approaches.[21] A detailed analysis needs to be performed to assess how much negative emissions a particular process achieves. This analysis includes life cycle analysis and "monitoring, reporting, and verification" (MRV) of the entire process.[24] Carbon capture and storage (CCS) are not regarded as CDR because CCS does not reduce the amount of carbon dioxide already in the atmosphere.Solar radiation modification
Solar radiation modification (SRM) (or solar geoengineering or solar radiation management), is a group of large-scale approaches to reduce global warming by increasing the amount of sunlight (solar radiation) that is reflected away from Earth and back to space. Among the potential methods, stratospheric aerosol injection (SAI) is the most-studied,[25]: 350 followed by marine cloud brightening (MCB); others such as ground- and space-based methods show less potential or feasibility and receive less attention. SRM could be a supplement to climate change mitigation and adaptation measures,[26]: 1489 but would not be a substitute for reducing greenhouse gas emissions.[27] SRM is a form of climate engineering or geoengineering, and might be able to prevent some kinds of tipping.[28]
Scientific studies, based on evidence from climate models, have consistently shown that SRM could reduce global warming and many effects of climate change.[29][30][31] However, because warming from greenhouse gases and cooling from SRM would operate differently across latitudes and seasons, a world where global warming would be reduced by SRM would have a different climate from one where this warming did not occur in the first place. SRM would therefore pose environmental risks, as would a warmed world without SRM. Confidence in the current projections of how SRM would affect regional climate and ecosystems is low.[26]: 1491–1492Glacial geoengineering
Glacial geoengineering is a set of proposed geoengineering that focus on slowing the loss of glaciers, ice sheets, and sea ice in polar regions and, in some cases, alpine areas. Proposals are motivated by concerns that feedback loops—such as ice-albedo loss, accelerated glacier flow, and permafrost methane release—could amplify climate change and trigger climate tipping points.[32][33]
Proposed glacial geoengineering methods include regional or local solar radiation management, thinning cirrus clouds to allow more heat to escape, and deploying mechanical or engineering structures to stabilize ice. Specific strategies under investigation are stratospheric aerosol injection focused on polar regions,[34] marine cloud brightening,[35] surface albedo modification with reflective materials,[36] basal interventions such as draining subglacial water or promoting basal freezing,[33] and ice shelf protection measures including seabed curtains.[37]
Glacial geoengineering is in the early research stage and many proposals face major technical, environmental, and governance challenges.[35] Supporters argue that targeted interventions could help stabilize ice sheets, slow sea-level rise, and reduce the risk of passing irreversible thresholds in the climate system. At the same time, experts caution that the effectiveness of these methods remains highly uncertain and that interventions could produce unintended side effects.[33] Glacial geoengineering is generally considered a possible complement to, not a replacement for, efforts to reduce greenhouse gas emissions.[34][35]Governance
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Perspective
Most governance issues relating geoengineering are specific to the category or the specific method. Nevertheless, a couple of international governance instruments have addressed geoengineering collectively.
The Conference of Parties to the Convention on Biological Diversity have made several decisions regarding "climate related geoengineering." That of 2010 established "a comprehensive non-binding normative framework"[38]: 106 for "climate-related geoengineering activities that may affect biodiversity," requesting that such activities be justified by the need to gather specific scientific data, undergo prior environmental assessment, be subject to effective regulatory oversight.[39]: 96–97 [40]: 161–162 The Parties' 2016 decision called for "more transdisciplinary research and sharing of knowledge... in order to better understand the impacts of climate-related geoengineering."[40]: 161-162 [41]
The parties to the London Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter and its associated London Protocol have addressed "marine geoengineering." In 2013, the parties to the London Protocol adopted an amendment to establish a legally binding framework for regulating marine geoengineering, initially limited to ocean fertilization and requiring assessment and permitting before any activity proceeds. This amendment has not yet entered into force due to insufficient ratifications. In 2022, the parties to both agreements acknowledged growing interest in marine geoengineering, identified four techniques for priority review, and encouraged careful assessment of proposed projects under existing guidelines while considering options for further regulation. In 2023, they cautioned that these techniques could pose serious environmental risks, highlighted scientific uncertainty about their effects, urged strict application of assessment frameworks, and called for broader international cooperation.[42] Their work is supported by the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection of the International Maritime Organization.
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References
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