Climate engineering
Climate engineering (or geoengineering) is an umbrella term for both carbon dioxide removal and solar radiation modification, when applied at a planetary scale.[1]: 168 However, these two processes have very different characteristics. For this reason, the Intergovernmental Panel on Climate Change no longer uses this overarching term.[1]: 168 [2] Carbon dioxide removal approaches are part of climate change mitigation. Solar radiation modification is reflecting some sunlight (solar radiation) back to space.[3] All forms of climate engineering cannot be standalone solutions to climate change, but need to be coupled with other forms of climate change mitigation.[4] Some publications place passive radiative cooling into the climate engineering category. This technology increases the Earth's thermal emittance.[5][6][7] The media tends to use climate engineering also 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.
"Geoengineering" redirects here. For other uses, see Geoengineering (disambiguation).
Some types of climate engineering are highly controversial due to the large uncertainties around effectiveness, side effects and unforeseen consequences.[8] However, the risks of such interventions must be seen in the context of the trajectory of climate change without them.[9][10]
According to climate economist Gernot Wagner, the term geoengineering is "so vague and all-encompassing as to have lost much meaning".[8]: 14
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.[1]: 168 However, these two methods have very different geophysical characteristics, which is why the Intergovernmental Panel on Climate Change no longer uses this term.[1]: 168 [2] This decision was communicated in around 2018, see for example the "Special Report on Global Warming of 1.5 °C".[11]: 550 Specific technologies that fall into the "climate engineering" umbrella term include:[12]: 30
The following methods are not termed climate engineering in the latest IPCC assessment report in 2022[1]: 6–11 but are included under this umbrella term by other publications on this topic:[24][8]
Society and culture[edit]
Public perception[edit]
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.[12] 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.[12][81]
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.[70][82]
History[edit]
Several organizations have investigated climate engineering with a view to evaluating its potential, including the US Congress,[83] the US National Academy of Sciences, Engineering, and Medicine,[84] the Royal Society,[85] the UK Parliament,[86] the Institution of Mechanical Engineers,[87] and the Intergovernmental Panel on Climate Change. The IMechE report examined a small subset of proposed methods (air capture, urban albedo and algal-based CO2 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.[87]
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 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".[88] 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".[88]
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".[89] 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".[89]
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."[90][91][92] The resulting study titled Climate Intervention was released in February 2015 and consists of two volumes: Reflecting Sunlight to Cool Earth[93] and Carbon Dioxide Removal and Reliable Sequestration.[94]
In June 2023 the US government released a report that recommended conducting research on stratospheric aerosol injection and marine cloud brightening.[95]
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).[96]