page_title: Climate engineering
section_title: Solar radiation management
hierarchical_section_title: Climate engineering / Proposed strategies / Solar radiation management
caption_attribution_description: English: Estimated change in annual mean sea surface pH between the pre-industrial period (1700s) and the present day (1990s). Δ pH here is in standard pH units. Calculated from fields of dissolved inorganic carbon and alkalinity from the Global Ocean Data Analysis Project (GLODAP) climatology and temperature and salinity from the World Ocean Atlas (2005) climatology using Richard Zeebe's csys package. It is plotted here using a Mollweide projection (using MATLAB and the M_Map package). Note that the GLODAP climatology is missing data in certain oceanic provinces including the Arctic Ocean, the Caribbean Sea, the Mediterranean Sea and the Malay Archipelago.
context_page_description: Climate engineering or climate intervention, commonly referred to as geoengineering, is the deliberate and large-scale intervention in the Earth's climate system, usually with the aim of mitigating the adverse effects of global warming. The most prominent subcategory of climate engineering is solar radiation management. Solar radiation management attempts to offset the effects of greenhouse gases by causing the Earth to absorb less solar radiation. Almost all research into solar radiation management has to date consisted of computer modelling or laboratory tests, and an attempt to move to outdoor experimentation has proven controversial. A 2014 paper in Nature found that among a variety of climate engineering subcategories: afforestation, ocean upwelling, ocean iron fertilization, and ocean alkalinization, only solar radiation management was able to stabilize global temperatures to pre-industrial levels.
  Some methods of greenhouse gas removal, such as ocean iron fertilization, are forms of climate engineering. Ocean iron fertilization has been investigated in small-scale research trials. These experiments have proven controversial.
context_section_description: Solar radiation management (SRM) techniques would seek to reduce sunlight absorbed (ultra-violet, near infra-red and visible).  This would be achieved by deflecting 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 problems such as the ocean acidification caused by CO₂. In general, solar radiation management projects presently appear to be able to take effect rapidly and to have very low direct implementation costs relative to greenhouse gas emissions cuts and carbon dioxide removal. Furthermore, many proposed SRM methods would be reversible in their direct climatic effects. While greenhouse gas remediation offers a more comprehensive possible solution to global warming, it does not give instantaneous results; for that, solar radiation management is required.
  Solar radiation management methods may include:
  Surface-based: for example, protecting or expanding polar sea ice and glaciers, including the use of insulating blankets or artificial snow, using pale-colors for roofing materials and other man-made surfaces (i.e. roadways and exterior paints), attempting to change the oceans' brightness, growing high-albedo crops, or by distributing hollow glass beads in selected areas to increase ice coverage and lower temperatures.
  Troposphere-based: for example, marine cloud brightening, which would spray fine sea water to whiten clouds and thus increase cloud reflectivity.
  Upper atmosphere-based: creating reflective aerosols, such as stratospheric sulfate aerosols, specifically designed self-levitating aerosols, or other substances.
  Space-based: space sunshade – obstructing solar radiation with space-based mirrors, dust, etc.
caption: Change in sea surface pH caused by anthropogenic CO2 between the 1700s and the 1990s. This ocean acidification will still be a major problem unless atmospheric CO2 is reduced.
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