Carbon Removal technologies seek to remove carbon dioxide from the atmosphere. Solar Geoengineering technologies aim to reflect back more solar radiation, to
**Solar Radiation Modification (SRM) refers to deliberate, large-scale actions intended to decrease global average surface temperatures by increasing the reflection of sunlight away from the Earth.** Proposed SRM methods involve the use of aerosols (small particles) or other materials to increase the reflectivity of the atmosphere, clouds, or Earth’s surface. **Long-term protection of Earth’s climate and oceans requires substantial reductions in emissions and atmospheric concentrations of CO2 and other GHGs. SRM is not considered a substitute for climate mitigation efforts, which include decarbonization and GHG emission cuts.** SRM research is being conducted as a response to growing concerns that the pace of CO2 emissions reductions and CDR technology development is not sufficient to avoid severe impacts of climate change in the next decades. **Many of the processes most important for understanding SRM approaches—such as those that control the formation of clouds and aerosols—are among the most uncertain components of the climate system.** Climate models differ in simulating large-scale aerosol climate effects, including on surface temperatures, due to variations in how aerosol processes, atmospheric transport and mixing, and physics are represented.
Space-based geoengineering involves the use of space-based devices to reflect or block sunlight, thereby reducing the amount of solar energy reaching the Earth.
This approach involves reflecting sunlight back into space while allowing Earth's infrared radiation to escape, thereby controlling climate change.
Solar geoengineering (SG) refers to a set of methods aimed at cooling the Earth in order to counteract the warming effects of increases in greenhouse gases (
For example, geoengineering includes the removal of carbon dioxide from the atmosphere (also called Carbon Dioxide Removal – CDR) through methods such as direct air capture and storage, ocean iron fertilization, or ocean alkalinity enhancement. These activities are referred to as **Solar Geoengineering** or **Solar Radiation Modification (SRM).** Most proposed solar radiation modification techniques involve adding material to the atmosphere to increase the amount of incoming sunlight reflected back to space. Marine solar radiation management (mSRM) techniques, on the other hand, involve adding materials to ocean waters, sea ice, or the lower atmosphere to increase the amount of solar radiation reflected at or near the ocean's surface to limit surface warming or sea ice melt. * *Marine Cloud Brightening (MCB)* – adding particles, such as sea spray, to the lower atmosphere (near the surface) to increase the reflectivity of clouds over the ocean. Another subset of geoengineering activities intends to cool the Earth by intentionally modifying the concentration of certain gases in the atmosphere, including carbon dioxide.
However, research shows that using solar geoengineering could indirectly lower the amount of CO2 in the atmosphere by stemming permafrost melt, reducing energy-sector emissions and causing changes to the carbon-cycle feedback. Aerosol injection could have an edge on other proposed forms of solar geoengineering because it would not require a large technological leap to become a reality, Jones says:. These brighter clouds would reflect away more sunlight, says Prof Douglas MacMartin, an engineering researcher from Cornell University, who contributed to the US House of Representatives’ hearing on geoengineering. Earlier this month, MacMartin, Keith and Prof Katharine Ricke, a climate scientist from the University of California, San Diego, published a research paper exploring how solar geoengineering – via releasing aerosols into the stratosphere – could be used as part of an “overall strategy” for limiting global warming to 1.5C, which is the aspirational target of the Paris Agreement. However, the researchers point out that using solar geoengineering to hold global warming to 1.5C would not have the same environmental effect as reaching the target using mitigation.
A lot of these proposed solutions almost sound like they’re out of a science fiction novel and you may have heard of them as “geoengineering.” This can include reflecting the sun’s energy back into space, filtering the solar energy reaching the Earth’s surface or capturing greenhouse gases from the atmosphere. The oversupply of heat already in the deep ocean, paired with changes in ocean surface temperature caused by SRM, could influence weather patterns, ocean currents and the supply of nutrients essential to ocean plant and animal life in ways that are difficult to predict. Changes in the amount or quality of solar radiation reaching the ocean because of SRM could alter photosynthesis by marine algae and other plants, with unknown follow-on effects for the marine food web and for the carbon cycle. Decisions about SRM will involve both atmospheric and oceanic governance. The NASEM study highlights just how much we need to learn still about climate intervention methods like SRM.