Climate engineering or commonly geoengineering, is the deliberate and large-scale intervention in the Earth's climate system.The main categories of climate engineering are solar geoengineering and carbon dioxide removal. Solar geoengineering, or solar radiation modification, would reflect some sunlight (solar radiation) back to space to limit or reverse human-caused climate change. Carbon dioxide removal refers to removing carbon dioxide gas from the atmosphere and sequestering it for long periods of time. The difference between the two is sometimes described as solar geoengineering modifying the planet's shortwave radiation budget and carbon dioxide removal modifying its longwave radiation budget.
Climate engineering approaches are sometimes viewed as potential complementary options for limiting climate change or its impacts, alongside reducing greenhouse gas emissions and adaptation.There is substantial agreement among scientists that solar geoengineering and carbon dioxide removal cannot substitute for reducing emissions. Given that all types of measures for addressing climate change have economic, political, or physical limitations, some climate engineering approaches might eventually be used as part of an ensemble of responses, which could have the objective of climate restoration.
Although there are the large uncertainties over effectiveness and side effects and unforeseen consequences, most experts argue that the risks of such interventions must be seen in the context of risks of dangerous climate change.Interventions at large scale may run a greater risk of disrupting natural systems resulting in a dilemma that those approaches that could prove highly cost-effective in addressing extreme climate risk, might themselves cause substantial risk. Some have suggested that the concept of engineering the climate could reduce political and public pressure for emissions reduction, which could exacerbate overall climate risks; others assert that the threat of climate engineering could spur emissions cuts.
Solar geoengineering would deflect sunlight away from the Earth, or by increasing the reflectivity (albedo) of the atmosphere or the Earth's surface. These methods are not a substitute for climate change mitigation because they would not reduce greenhouse gas concentrations in the atmosphere, and thus would not address ocean acidification caused by carbon dioxide.In general, solar geoengineering projects presently appear able to take effect rapidly and reversible in their direct climatic effects. The US National Academy of Sciences, Engineering, and Medicine states in a 2021 report: "The available research indicates that SG could reduce surface temperatures and potentially ameliorate some risks posed by climate change (e.g., to avoid crossing critical climate “tipping points”; to reduce harmful impacts of weather extremes)."
Solar geoengineering methodsmay include:
Solar geoengineering requires relatively large scale implementation in order to impact the Earth's climate. The least costly proposals are estimated at tens of billions of US dollars annually in direct deployment costs. [ citation needed ] Solar geoengineering may pose novel significant risks such as regional climate disruptions.This is low enough that it might be in the interests of several single countries to implement them unilaterally.
Carbon dioxide removal (sometimes known as negative emissions technologies or greenhouse gas removal) includes methods that directly remove such gases from the atmosphere and those promote natural processes that drawdown and sequester carbon dioxide.Some methods overlap with carbon capture and storage. Carbon dioxide removal may not be considered to be climate engineering by all commentators because it is not necessarily large scale. Techniques in this category include:
Many of the IPCC model projections to keep global mean temperature rise below 1.5 and 2 °C are based on assume large-scale deployment of carbon dioxide removal. Most carbon dioxide removal methods are presently expensive. Carbon dioxide removal techniques are typically slow to act, expensive, and entail risks that are relatively familiar, such as the risk of carbon dioxide leakage from underground storage formations. Carbon dioxide removal, like greenhouse gas emissions reductions, have impacts proportional to their scale. In other words, these techniques would not be "implemented" in the same sense as solar geoengineering ones.
Climate engineering would represent a large-scale, intentional effort to modify the climate. It would differ from activities such as burning fossil fuels, as those change the climate inadvertently. Intentional climate change is often viewed differently from a moral standpoint.It raises questions of whether humans have the right to change the climate deliberately, and under what conditions. For example, there may be an ethical distinction between climate engineering to minimize global warming and doing so to optimize the climate. Furthermore, ethical arguments often confront larger considerations of worldview, including individual and social-religious commitments. This may imply that discussions of climate engineering should reflect on how religious commitments might influence the discourse. For many people, religious beliefs are pivotal in defining the role of human beings in the wider world. Some religious communities might claim that humans have no responsibility in managing the climate, instead of seeing such world systems as the exclusive domain of a Creator. In contrast, other religious communities might see the human role as one of "stewardship" or benevolent management of the world. The question of ethics also relates to issues of policy decision-making. For example, the selection of a globally agreed target temperature is a significant problem in any climate engineering governance regime, as different countries or interest groups may seek different global temperatures.
One of the lesser focused aspects of climate engineering is the role it can play in global inequality (Environmental Justice). Emissions are largely concentrated in a relatively few companies.In not addressing the issue or changing practices to emit less, they directly receive benefit from the damage they cause to the climate. In a similar way, wealthier nations have far greater emissions than their poorer counterparts. However, it is poorer nations who will be unable to pay the costly fees for the adaptation and mitigation needed to meet the challenges of climate change. Simply put, wealthy nations have the most to give and poorer nations have the most to lose. Climate engineering has the potential to address inequality by putting the burden on those who benefit from the emissions rather than sharing the burden with those who have little responsibility and who are doomed to suffer the most.
Some environmental organizations have been reluctant to endorse or oppose (such as Friends of the Earthand Greenpeace ) solar geoengineering but are often more supportive of some nature-based carbon dioxide removal projects, such as afforestation and peatland restoration. Some commentators appear fundamentally opposed. The ETC Group has called for a moratorium on climate engineering techniques.
It has been argued that regardless of the economic, scientific, and technical aspects, the difficulty of achieving concerted political action on global warming requires other approaches.Those arguing political expediency say the difficulty of achieving meaningful emissions cuts and the effective failure of the Kyoto Protocol demonstrate the practical difficulties of achieving carbon dioxide emissions reduction by the agreement of the international community. However, others point to support for climate engineering proposals among think tanks with a history of opposition to emissions reductions as evidence that, rather than climate engineering being a solution to the difficulties of emissions reductions, the prospect of climate engineering is being used as part of an argument to stall emissions reductions in the first place.
The existence of such techniques may reduce the political and social impetus to reduce carbon emissions.This has generally been called a potential moral hazard, although risk compensation may be a more accurate term. This concern causes many environmental groups and campaigners to be reluctant to advocate or discuss climate engineering for fear of reducing the imperative to cut greenhouse gas emissions. However, several public opinion surveys and focus groups have found evidence of either assertions of a desire to increase emission cuts in the face of climate engineering, or of no effect. Other modelling work suggests that the threat of climate engineering may in fact increase the likelihood of emissions reduction.
Climate engineering opens up various political and economic issues. The governance issues characterizing carbon dioxide removal compared to solar geoengineering are largely distinct. As a result of these differing characteristics, the key governance problem for carbon dioxide removal (as with emissions reductions) is making sure actors do enough of it (the so-called "free rider problem"), whereas the key governance issue for solar geoengineering is making sure actors do not do it too early or too much (sometimes called the "free driver" problem).
Domestic and international governance vary by the proposed climate engineering method. There is presently a lack of a universally agreed framework for the regulation of climate engineering activity or research. Scholars at the Oxford Martin School at Oxford University proposed a set of voluntary principles, which may guide climate engineering research and use. The short version of the 'Oxford Principles'is:
These principles have been endorsed by the House of Commons of the United Kingdom Science and Technology Select Committee on "The Regulation of Geoengineering",and have been referred to by authors discussing the issue of governance.
The Asilomar International Conference on Climate Intervention Technologies was convened to identify and develop risk reduction guidelines for climate intervention experimentation.
The Parties to the Convention on Biological Diversity have made three decisions on what they call "climate-related geo-engineering." That in 2010 called on countries to refrain from "climate-related geo-engineering activities that may affect biodiversity" until these are governed, they are scientifically justified, and associated risks have been considered.Some critics of climate engineering call this a "de facto moratorium," but the Secretariat of the Convention on Biological Diversity calls it a “non-binding normative framework.” and many legal scholars reject this characterization. The 2016 decision called for "more transdisciplinary research and sharing of knowledge among appropriate institutions is needed in order to better understand the impacts."
A large 2018 study investigated public perceptions of six climate engineering methods, with an online survey in the United States, United Kingdom, Australia, and New Zealand.The findings were also compared against similar 2012 survey in Australia and New Zealand. Public awareness of climate engineering was low with less than a fifth of respondents reporting prior knowledge. Perceptions of the six climate engineering methods were largely negative and frequently associated with attributes like 'risky', 'artificial' and 'unknown effects'. Carbon dioxide removal methods were preferred over solar geoengineering. Public perceptions were remarkably stable with only minor differences between the different countries in the 2018 and 2012 surveys.
In a 2017 focus group study conducted by the Cooperative Institute for Research in Environmental Sciences (CIRES) in the United States, Japan, New Zealand, and Sweden, participants were asked about carbon sequestration options, reflection proposals such as with space mirrors, or brightening of clouds, and their majority responses could be summed up as follows:
Moderators floated then the idea of a future "climate emergency" such as rapid environmental change. The participants felt that mitigation and adaptation to climate change were strongly preferred options in such a situation, and climate engineering was seen as a last resort.Some extremists have proposed that there are secret government actions implementing geoengineering on a large scale, affecting weather to produce winter, or cooling, or large fires, or other detrimental effects. There is no evidence to substantiate these unorthodox claims.
Most of what is known about the suggested techniques are based on laboratory experiments, observations of natural phenomena, and computer modeling techniques. Some proposed climate engineering methods employ methods that have analogs in natural phenomena such as stratospheric sulfur aerosols and cloud condensation nuclei. As such, studies about the efficacy of these methods can draw on information already available from other research, such as that following the 1991 eruption of Mount Pinatubo. However, comparative evaluation of the relative merits of each technology is complicated, especially given modeling uncertainties and the early stage of engineering development of many proposed climate engineering methods.
Several organizations have investigated climate engineering with a view to evaluating its potential, including the US Congress, CO
2 capture techniques), and its main conclusions were that climate engineering should be researched and trialed at the small scale alongside a wider decarbonization of the economy.
The Royal Society review examined 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 report 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".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 a 2009 review study, Lenton and Vaughan evaluated a range of proposed climate engineering techniques. CO
2 emissions, rather than as an alternative to it".
In October 2011, a Bipartisan Policy Center panel issued a report urging immediate researching and testing in case "the climate system reaches a 'tipping point' and swift remedial action is required."
The US National Academy of Sciences, Engineering, and Medicine conducted 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."The resulting study titled Climate Intervention was released in February 2015 and consists of two volumes: Reflecting Sunlight to Cool Earth and Carbon Dioxide Removal and Reliable Sequestration. According to their brief about the study:
Climate intervention is no substitute for reductions in carbon dioxide emissions and adaptation efforts aimed at reducing the negative consequences of climate change. However, as our planet enters a period of changing climate never before experienced in recorded human history, interest is growing in the potential for deliberate intervention in the climate system to counter climate change... Carbon dioxide removal strategies address a key driver of climate change, but research is needed to fully assess if any of these technologies could be appropriate for large-scale deployment. Albedo modification strategies could rapidly cool the planet's surface but pose environmental and other risks that are not well understood and therefore should not be deployed at climate-altering scales; more research is needed to determine if albedo modification approaches could be viable in the future.
A space sunshade or sunshield is a parasol that diverts or otherwise reduces some of the sun's radiation, preventing them from hitting a spacecraft or planet and thereby reducing its insolation, which results in reduced heating. Light can be diverted by different methods. First proposed in 1989, the original space sunshade concept involves putting a large occulting disc, or technology of equivalent purpose, between the Earth and Sun.
Planetary engineering is the application of technology for the purpose of influencing the global environments of a planet. Its objectives usually involve increasing the habitability of other worlds or mitigating decreases in habitability to Earth.
Technogaianism is a bright green environmentalist stance of active support for the research, development and use of emerging and future technologies to help restore Earth's environment. Technogaians argue that developing safe, clean, alternative technology should be an important goal of environmentalists.
Climate change mitigation consists of actions to limit global warming and its related effects. This involves reductions in human emissions of greenhouse gases (GHGs) as well as activities that reduce their concentration in the atmosphere.
Carbon sequestration is the long-term removal, capture, or sequestration of carbon dioxide from the atmosphere to slow or reverse atmospheric CO
2 pollution and to mitigate or reverse climate change. Carbon dioxide is naturally captured from the atmosphere through biological, chemical, and physical processes. These changes can be accelerated through changes in land use and agricultural practices, such as converting crop and livestock grazing land into land for non-crop fast growing plants. Artificial processes have been devised to produce similar effects, including large-scale, artificial capture and sequestration of industrially produced CO
2 using subsurface saline aquifers, reservoirs, ocean water, aging oil fields, or other carbon sinks, bio-energy with carbon capture and storage, biochar, ocean fertilization, enhanced weathering, and direct air capture when combined with storage.
The terraforming of Venus is the hypothetical process of engineering the global environment of the planet Venus in such a way as to make it suitable for human habitation. Terraforming Venus was first proposed in a scholarly context by the astronomer Carl Sagan in 1961, although fictional treatments, such as The Big Rain of The Psychotechnic League by novelist Poul Anderson, preceded it. Adjustments to the existing environment of Venus to support human life would require at least three major changes to the planet's atmosphere:
The Virgin Earth Challenge was a competition offering a $25 million prize for whoever could demonstrate a commercially viable design which results in the permanent removal of greenhouse gases out of the Earth's atmosphere to contribute materially in global warming avoidance. The prize was conceived by Richard Branson, and was announced in London on 9 February 2007 by Branson and former US Vice President Al Gore. However, the prize was never awarded. In 2019, Virgin quietly took the prize website offline, after keeping 11 finalists suspended in expectation for 8 years. Al Gore had withdrawn from the jury earlier and commented that "He was not part of the decision to discontinue the contest.".
This is a list of climate change topics.
Kenneth Caldeira is an American atmospheric scientist. His areas of research include ocean acidification, climate effects of trees, intentional climate modification, interactions in the global carbon cycle/climate system, and sustainable energy.
Solar geoengineering, or solar radiation modification (SRM) is a proposed type of climate engineering in which sunlight would be reflected back to space to limit or reverse human-caused climate change. Most methods would increase the planetary albedo (reflectivity), for example with stratospheric aerosol injection. Although most techniques would have global effects, localized protective or restorative methods have also been proposed to protect natural heat reflectors including sea ice, snow, and glaciers.
Stratospheric sulfur aerosols are sulfur-rich particles which exist in the stratosphere region of the Earth's atmosphere. The layer of the atmosphere in which they exist is known as the Junge layer, or simply the stratospheric aerosol layer. These particles consist of a mixture of sulfuric acid and water. They are created naturally, such as by photochemical decomposition of sulfur-containing gases, e.g. carbonyl sulfide. When present in high levels, e.g. after a strong volcanic eruption such as Mount Pinatubo, they produce a cooling effect, by reflecting sunlight, and by modifying clouds as they fall out of the stratosphere. This cooling may persist for a few years before the particles fall out.
Marine cloud brightening also known as marine cloud seeding and marine cloud engineering is a proposed solar radiation management climate engineering technique that would make clouds brighter, reflecting a small fraction of incoming sunlight back into space in order to offset anthropogenic global warming. Along with stratospheric aerosol injection, it is one of the two solar radiation management methods that may most feasibly have a substantial climate impact. The intention is that increasing the Earth's albedo, in combination with greenhouse gas emissions reduction, carbon dioxide removal, and adaptation, would reduce climate change and its risks to people and the environment. If implemented, the cooling effect is expected to be felt rapidly and to be reversible on fairly short time scales. However, technical barriers remain to large-scale marine cloud brightening. There are also risks with such modification of complex climate systems.
Carbon dioxide removal (CDR), also known as greenhouse gas removal, is a process in which carbon dioxide gas is removed from the atmosphere and sequestered for long periods of time – in the context of net zero greenhouse gas emissions targets, CDR is increasingly integrated into climate policy. CDR methods are also known as negative emissions technologies, and may be cheaper than preventing some agricultural greenhouse gas emissions.
Bio-geoengineering is a form of climate engineering which seeks to use or modify plants or other living things to modify the Earth's climate.
Stratospheric aerosol injection is a proposed method of solar geoengineering to reduce human-induced climate change. This would introduce aerosols into the stratosphere to create a cooling effect via global dimming, which occurs naturally from volcanic eruptions. It appears that stratospheric aerosol injection, at a moderate intensity, could counter most changes to temperature and precipitation, take effect rapidly, have low direct implementation costs, and be reversible in its direct climatic effects. The Intergovernmental Panel on Climate Change concludes that it "is the most-researched [solar geoengineering] method, with high agreement that it could limit warming to below 1.5°C." However, like other solar geoengineering approaches, stratospheric aerosol injection would do so imperfectly and other effects are possible, particularly if used in a suboptimal manner.
David W. Keith is the Gordon McKay Professor of Applied Physics for Harvard University's Paulson School of Engineering and Applied Sciences (SEAS) and Professor of Public Policy for the Harvard Kennedy School at Harvard University. Early contributions include development of the first atom interferometer and a Fourier-transform spectrometer used by NASA to measure atmospheric temperature and radiation transfer from space. A specialist on energy technology, climate science, and related public policy, and a pioneer in carbon capture and storage, Keith is a founder and board member of Carbon Engineering.
Biosequestration is the capture and storage of the atmospheric greenhouse gas carbon dioxide by continual or enhanced biological processes.
Space mirrors are man-made 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 the 1980s, space mirrors have mainly been theorized as a way to deflect sunlight to counter global warming and was seriously considered in the 2000s.
Carbon rift is a theory attributing the input and output of carbon into the environment to human capitalistic systems. This is a derivative of Karl Marx's concept of metabolic rift. In practical terms, increased commodity production demands that greater levels of carbon dioxide (or CO2) be emitted into the biosphere via fossil fuel consumption. Carbon rift theory states that this ultimately disrupts the natural carbon cycle and that this "rift" has adverse effects on nearly every aspect of life. Many of the specifics regarding how this metabolic carbon rift interacts with capitalism are proposed by Brett Clark and Richard York in a 2005 article titled "Carbon Metabolism: Global capitalism, climate change, and the biospheric rift" in the journal Theory and Society. Researchers such as Jean P. Sapinski of the University of Oregon claim that, despite increased interest in closing the carbon rift, it is projected that as long as capitalism continues, there is little hope of reducing the rift.
Direct air capture (DAC) is a process of capturing carbon dioxide (CO
2) 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 CO
2 for sequestration or utilization or production of carbon-neutral fuel and windgas. Carbon dioxide removal is achieved when ambient air makes contact with chemical media, typically an aqueous alkaline solvent or functionalized sorbents. These chemical media are subsequently stripped of CO2 through the application of energy (namely heat), resulting in a CO2 stream that can undergo dehydration and compression, while simultaneously regenerating the chemical media for reuse.