14 DAY TRIAL // For some time, climatologists have counted clouds as part of the natural phenomena and processes that contribute to cooling the planet. Now, a computational study demonstrates that summer thunderstorm clouds actually contribute to warming the atmosphere, especially in polluted environments.
In a paper published in the May 10 issue of the esteemed scientific journal Geophysical Research Letters, investigators at the US Department of Energy's (DOE) Pacific Northwest National Laboratory (PNNL) say that pollution and clouds interact in a very unfavorable way.
One of the questions that this investigation raises is by how much the newly-discovered effect offsets the positive, cooling effect that other clouds have. In order to answer this, scientists will have to introduce the new discovery in existing climate models, and see how their conclusions change.
Thunderstorm clouds can be easily recognized by their anvil-shaped tops. When these atmospheric structures develop over areas with high levels of pollution, they tend to become stronger, more intense, and last for longer periods of time.
During the night, they trap a lot of heat under their tops, contributing to heating the atmosphere over that specific region. The conclusions of the new study were presented by PNNL climate researcher Jiwen Fan, in a statement. The expert was also the lead author of the GRL paper.
“Global climate models don't see this effect because thunderstorm clouds simulated in those models do not include enough detail. The large amount of heat trapped by the pollution-enhanced clouds could potentially impact regional circulation and modify weather systems,” Fan explains.
Climatologists admit that clouds are the main unknown in atmospheric studies. Their actions and movement patterns cannot be predicted with great accuracy, and they produce mixed effects on temperatures. Further studies are needed to understand Earth's cloud system.
“Those numbers for the warming are very big, but they are calculated only for the exact day when the thunderstorms occur. Over a longer time-scale such as a month or a season, the average amount of warming would be less because those clouds would not appear everyday,” Fan says.
The new investigation was supported by the DOE Office of Science.