Marine cloud whitening involves making clouds brighter or whiter so that they can reflect more sunlight and solar radiation back towards space. This reflection will result in less heat being absorbed into the Earth's atmosphere and will combat the challenges of climate change. Clouds over marine environments, like the ocean, are thought to be easiest to brighten.
Although it is a smart idea in theory, how smart is it in practice? Scientists propose that the clouds can be sprayed with aerosols that will act as a 'condensation nuclei' in clouds. The aerosols also contain particles of sea salt and this mixture is thought to encourage water particles to merge and therefore lead to brighter and thicker clouds. On top of this, the same merging happens within pollution particles, meaning that pollutants will not be a problem when spraying the aerosols.
This theory is yet to be performed on a large scale, and virtually all assessments have been derived from models. Because of this, scientists are still unsure on how effective it will be and if there could be any damaging side effects.
There has been contradictory results from tests, including the idea that cloud brightening could effect precipitation patterns and therefore effect vegetation and food production. Another study showed decreases in temperature in one region, but increases in another, making the practice of cloud brightening less equitable. One of the only physical experiments was small-scale in Alameda, California, where after a month of testing, the experiment was put to a halt after a public meeting voted to stop it.
Due to the lack of real-world experiments and evidence that cloud brightening is effective, it is not clear whether or not it could be a good mechanism to address climate change. With ever prevalent speculation towards climate change, it is difficult to continue experiments without wider support.