There are many things we still don’t understand about our rapidly warming planet. To find the answers, scientists are urging us to look at the clouds. These seemingly harmless, fluffy formations of tiny water particles have a surprisingly large bearing in predicting how our climate is changing.
“To make things as simple as possible, clouds can be distinguished between low and high clouds,” says Paulo Ceppi, researcher and lecturer in Climate Science at the Grantham Institute for Climate Change, Imperial College London. “Low clouds mostly affect the amount of reflected sunlight, creating what I would call a parasol effect. High clouds also reflect sunlight away from the planet’s surface, but at the same time, they have a large greenhouse effect by acting as an insulating blanket.”
Clouds play a part in the global radiation balance or ‘global energy budget’. This is what ultimately drives climate change, Ceppi continues. When the amount of CO2 and other greenhouse gases increase in the atmosphere, it makes it harder for the planet to emit radiation to space.
“It's a bit like a bathtub. If you have less water flowing out than what's flowing in, it means the water level will have to rise. And the same thing happens to Earth’s temperature – it will keep rising as long as there's an imbalance.”
Clouds are studied by using satellites, weather balloons, simulations and even sailor’s logs to collect data that’s used in climate change models and projections. In January 2022, NASA launched a citizen science data challenge called GLOBE Cloud Challenge: Clouds in a Changing Climate. The aim of the data challenge was to collect cloud data from people around the globe through The GLOBE Program to better understand how and why the climate is changing.
“Clouds are one of the key players in understanding how the climate is changing,” says Marilé Colón Robles, Cloud Project Scientist for NASA GLOBE Clouds. “Cloud observations made by people provide us with data that satellites might miss. Matching human observations with satellite data provides a complete picture of what’s happening with the clouds.”
Matching human observations with satellite data provides a complete picture of what’s happening with the clouds.
In the Cloud Challenge, participants were asked to observe the sky and the type of clouds they saw before logging them in The GLOBE Program’s GLOBE Observer app. The data collected was compared with satellite data obtained at about the same time and location. Around 49 000 satellite-matched observations [more than double to the original goal] were submitted during the one-month challenge period. More than 3600 participants from 89 countries from all seven continents provided photos to the GLOBE Program’s database.
“It takes a lot of money to organise a research project that’s usually conducted in a small area. The Cloud Challenge was worldwide and gave people the chance to make a difference on a global scale,” Colón Robles explains. “We even received observations from Antarctica from people on expedition trips.”
The data will be used in various ways to create research papers and studies that will include climate models. Photographs submitted by participants are also included in the NASA GLOBE CLOUD GAZE project in the Zooniverse online platform where citizen scientists can continue to interpret what they see in the clouds. There’s a lot of information that can still be extracted, and made available to researchers, according to Colón Robles.
“People around the world are reporting how the climate is changing. We hear of thunderstorms in Alaska, which is something unheard of in those latitudes. And in places like Saudi Arabia, people don't see clouds anymore at all. These observations are critical, and they give people the power to express to their communities how things are changing,” Colón Robles adds.
As global warming continues, the amount of cloud cover and the thickness and height of clouds is expected to change. “Scientists call this the cloud feedback – changes in clouds that can amplify or dampen climate change,” Ceppi explains. “Climate models don’t always accurately simulate cloud processes, and that’s why different models produce varied results.”
This means more cloud data is needed for accurate climate projections.
There’s actually very little margin left until we reach the 1.5-degree threshold of global warming.
So, how worried should we be about the greenhouse effect produced by clouds? In a 2021 study, Ceppi and his colleague Peer Nowack performed a new analysis of global satellite observations of clouds, discovering that clouds have a moderately amplifying effect. But when it comes to the uncertainty of cloud data in climate projections and issues such as carbon budgets, it’s the timespan that counts.
“There’s actually very little margin left until we reach the 1.5-degree threshold of global warming. If you're worried about the world breaking that level, then clouds are perhaps not that important.”
But the higher we go in terms of warming levels, the larger the uncertainty due to poorly understood cloud feedback. On this level, cloud data is essential, Ceppi thinks.
“Climate change won’t end in 2050, or at 1.5 degrees. We have a responsibility towards future generations, and we need to know how things will change in the long term as well.”