The Warming Influence of Clouds

At a surface level understanding, the answer may seem obvious. On a day with clouds and sun, it generally feels cooler when the clouds are blocking the sun's rays, versus when full sunshine is reaching the ground. However, when it comes to the full energy budget of the globe, the question of what net effect that clouds will have on the future climate of the Earth is only now coming into clearer focus. In new research from scientists at Imperial College London and the University of East Anglia, they found that it is very likely (probability of more than 97.5%) that clouds will amplify future climate warming.

The type, altitude, and thickness of clouds all play a role in determining what effect, either cooling or warming that particular clouds provide. A lower altitude, blanket-like deck of stratus clouds will have a net cooling effect as they tend to block the incoming solar radiation. However, thin, high-altitude clouds would still allow most of the sun's radiation to reach the ground, and would also trap the longwave radiation that the Earth emits in return, thereby amplifying the greenhouse effect.

In order to investigate the role of clouds on the energy budget at a global scale, the researchers analyzed cloud cover data from satellites along with observations of temperature, humidity, and wind. Then, in order to deduce the patterns between these observations and the global satellite imagery, the team relied on computer artificial intelligence.

97.5% was the probability they found that clouds will amplify any future climate warming. In an earlier study, one of the main reasons for this net warming effect is the projected reduction in low-altitude marine stratus clouds which have the aforementioned net cooling effect. Also, as the temperature profile of the atmosphere is expected to become more unstable in the future, this would also work to erode these cooling decks of marine stratus clouds by promoting low-level air to rise, allowing more atmospheric mixing, and allowing more sunshine through a broken cloud deck.