In the race against climate change, scientists at Harvard University propose that dimming sunlight could cool down the planet.

But what does that mean? The ambitious project involves launching a huge balloon into the stratosphere, carrying 600kg of calcium carbonate - or chalk, which would be sprayed 12 miles above the Earth’s surface.

Scientists will then monitor how the dust particles interact with the atmosphere. It’s a process known as solar geoengineering.

The chalk would, in theory, reflect sunlight and in turn slow global warming. Some experts predict the sky would also shift from blue to white during daylight hours.