Burning fossil fuels releases CO2 which warms the planet but it also releases tiny pollution particles which have a cooling effect. This effect can be seen in satellite images, which show whiter clouds trailing behind polluting ships when they pass under certain clouds. Cloud droplets can only form around tiny seed particles, so these tracks form as ships add more tiny particles to clouds, meaning the clouds form a greater number of smaller droplets, making them more reflective. 

Cloud Brightening is a proposal to artificially brighten clouds by spraying sea-salt particles up from the surface of the ocean. This idea won’t work in all regions, but researchers are actively studying its potential to cool the great barrier reef and to slow the melting of the Arctic.

There are large uncertainties around this idea and field tests will be needed to determine whether it would actually work. There are also concerns that while it would cool the areas where it was applied, it might also shift patterns of rainfall in nearby regions. A better understanding of the potential and risks around cloud brightening will be essential to informing discussions around its use.

During the Crisis stage, you may ignore a Loss of Arctic Sea Ice or Thawing Permafrost result on the Planetary Effects die.
You may take this action once per round for each Geoengineering tag in this card's stack.

• Marine cloud brightening  (Wikipedia)

• What is marine cloud brightening? (Great Barrier Reef Foundation)

• Contact your political representatives to urge international rules and scrutiny about the test or use of risky technologies such as these.

• Study atmospheric or climate science and you might be able to contribute to our understanding of this idea.