Editing Planetary engineering (section)

== Climate engineering ==
{{Main|Climate engineering}}
[[File:MarsTransitionV.jpg|thumb|Impression of the hypothetical phrases of the terraforming of Mars]]
[[Climate engineering]] is a form of planetary engineering which involves the process of deliberate and large-scale alteration of the Earth's climate system to combat climate change.<ref name=":4">{{Cite web|title=What is Climate Engineering?|url=https://www.ucsusa.org/resources/what-climate-engineering|access-date=27 October 2021|website=Union of Concerned Scientists|language=en|archive-date=27 October 2021|archive-url=https://web.archive.org/web/20211027225649/https://www.ucsusa.org/resources/what-climate-engineering|url-status=live}}</ref> Examples of geoengineering are carbon dioxide removal (CDR), which removes carbon dioxide from the atmosphere, and [[solar radiation modification]] (SRM) to reflect solar energy to space.<ref name=":4" /><ref>{{Cite web|date=9 May 2018|title=Explainer: Six ideas to limit global warming with solar geoengineering|url=https://www.carbonbrief.org/explainer-six-ideas-to-limit-global-warming-with-solar-geoengineering|access-date=1 November 2021|website=Carbon Brief|language=en|archive-date=1 November 2021|archive-url=https://web.archive.org/web/20211101225428/https://www.carbonbrief.org/explainer-six-ideas-to-limit-global-warming-with-solar-geoengineering|url-status=live}}</ref> [[Carbon dioxide removal]] (CDR) has multiple practices, the simplest being [[reforestation]], to more complex processes such as [[direct air capture]].<ref name=":4" /><ref>{{Cite web|title=Effectively removing {{CO2}} from the atmosphere|url=https://www.sciencedaily.com/releases/2021/08/210813100255.htm|access-date=27 October 2021|website=ScienceDaily|language=en|archive-date=27 October 2021|archive-url=https://web.archive.org/web/20211027230911/https://www.sciencedaily.com/releases/2021/08/210813100255.htm|url-status=live}}</ref> The latter is rather difficult to deploy on an industrial scale, for high costs and substantial energy usage would be some aspects to address.<ref name=":4" />

Examples of SRM include [[stratospheric aerosol injection]] (SAI) and [[marine cloud brightening]] (MCB).<ref name=":4" /> When a volcano erupts, small particles known as [[aerosol]]s proliferate throughout the atmosphere, reflecting the sun's energy back into space.<ref name=":4" /><ref name=":5">{{Cite web|title=Volcanoes Can Affect Climate|url=https://www.usgs.gov/natural-hazards/volcano-hazards/volcanoes-can-affect-climate|access-date=1 November 2021|website=USGS|archive-date=31 October 2021|archive-url=https://web.archive.org/web/20211031123358/https://www.usgs.gov/natural-hazards/volcano-hazards/volcanoes-can-affect-climate|url-status=live}}</ref> This results in a cooling effect, and humanity could conceivably inject these aerosols into the stratosphere, spurring large-scale cooling.<ref name=":4" /><ref name=":5" />

[[File:ShipTracks.jpg|thumb|Visible ship tracks in the Northern Pacific, on 4 March 2009. On an overcast day, the clouds look uniform. However, NASA MODIS images' sensor reveals long, skinny trails of brighter clouds hidden within. As ships travel across the ocean, pollution in the ships' exhaust create more cloud drops that are smaller in size, resulting in even brighter clouds.]]
One proposal for MCB involves spraying a vapor into low-laying sea clouds, creating more cloud condensation nuclei.<ref name=":3">{{Cite web|title=Proposed Geoengineering Technologies|url=https://www.geoengineeringmonitor.org/technologies/|access-date=3 November 2021|website=Geoengineering Monitor|language=en-US|archive-date=3 November 2021|archive-url=https://web.archive.org/web/20211103232453/https://www.geoengineeringmonitor.org/technologies/|url-status=live}}</ref> This would in theory result in the cloud becoming whiter, and reflecting light more efficiently.<ref name=":3" />