What Could Go Wrong!
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.
Even though the importance of aerosols for the formation of clouds is, in general, well understood, many uncertainties remain. In fact, the latest IPCC report considers aerosol-cloud interactions as one of the current major challenges in climate modeling in general. In particular, the number of droplets does not increase proportionally when more aerosols are present and can even decrease, in effect speeding up global warming. Extrapolating the effects of particles on clouds observed on the microphysical scale to the regional, climatically relevant scale, is not straightforward. There is some potential for changes to rainfall and amounts of rain, although modeling suggests that the changes are likely less than those for stratospheric aerosol injection and considerably smaller than for continued man made global warming caused by fossil fuels.
The costs of marine cloud brightening remain largely unknown. One academic paper implied annual costs of approximately 5 billion annually. Estimates of how much money it would take to end global climate change range between $300 billion and $50 trillion over the next two decades or spend 4.5 trillion to give every person and business in the USA free solar power to power homes and vehicles with enough left over to sell to Canada and Mexico forever!
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