If you look up, you’re more likely than not to see some kind of cloud cover. Up to 70 percent of Earth’s land mass is covered with clouds at any given time, according to NASA’s Earth Observatory.

Participants can use the GLOBE Observer app to identify and report on those clouds and atmospheric visibility in their backyards. They are asked to time their observations to coincide with satellite flyovers, helping NASA scientists clear up questions about clouds the satellites have a hard time identifying.

Participants can report on everything from surface conditions to the sky’s cover and visibility, and the app helps walk them through figuring out which types of clouds are above them.

NASA wants to collect at least 20,000 cloud observations during the challenge.

Another way to participate is through NASA GLOBE Cloud Gaze. Participants use the Zooniverse platform to look at existing sky photographs and identify cloud types and things such as smoke plumes.

All that ground-up data has a purpose: to give scientists a more robust understanding of clouds and their effect on climate.

Clouds can warm the atmosphere by trapping heat from the Earth’s surface. But they can also cool it by shielding the planet from the sun’s intense rays. The height and type of the clouds matters when it comes to Earth’s energy balance; high-level clouds reflect some solar radiation back into the space, but trap some heat in the atmosphere and bounce it back down toward Earth. Low-hanging clouds tend to cool Earth’s surface.