The Climate Wild Card
At any give time, clouds cover about 70% of our planet. As you might expect, this has a huge influence on all kinds of things, from the global weather patterns you see here to Earth’s climate, including our planet’s overall temperature.
Energy, in the form of solar radiation from the Sun, is constantly beating down on Earth. This energy is either reflected away or taken in and then radiated back into space as heat. If the Earth is to remain at the same temperature, the planet has to return to space as much energy as it receives from the sun.
Clouds influence this energy exchange in both directions—by reflecting away some incoming solar radiation and insulating the planet by absorbing some of the outgoing heat.
All of Earth’s clouds combined reflect more energy than they absorb and have an overall cooling effect. That means if our planet were completely cloudless, it would be about 22 degrees (F) warmer than it is now.
But not all clouds are equal. Some types are better reflectors while others are better absorbers. For example, low, dense layers, like these stratus clouds, reflect more energy than they absorb and tend to have an overall cooling effect. High, wispy formations, like these cirrus clouds, absorb more energy than they reflect and have an overall warming effect.
But clouds not only affect temperature, they’re also affected by temperature. With the level of greenhouse gases in the atmosphere expected to continue to skyrocket, Earth’s temperature is predicted to rise as well. This is sure to influence the types, numbers, and locations of clouds that form.
Now, the burning question for climate scientists is, how will clouds respond as the planet warms? Could we see an increase in reflecting clouds, which would help to slow the global warming trend? Or will there be an increase in absorbing clouds, which could dramatically speed up the warming?
In fact, if cirrus clouds increase significantly, it's potentially far worse than previous predictions, with some estimates suggesting that in the next few centuries, polar regions could heat up by as much as 25 degrees, melting ice sheets and raising ocean levels by as much as 6 feet. So, the role clouds might play in climate change is not just an interesting scientific question, it’s one that’s critical to our planet’s future. And it’s one that scientists want to answer as soon as possible.
ARCHIVAL MATERIAL CREDITS
“Earth from Space” Darlow Smithson and WGBH Education Foundation
National Park Service
Steven Bedard, Writer/Producer
Anna Rothschild, Animator/Editor/Narrator
Scorekeepers Music Library, Music