Cirrus Cloud Formation Influenced By Human Activity, Pollution: A Study

Cirrus clouds, the thin wisps of vapor known to cover nearly one-third of the globe, are largely formed around mineral dust and metallic aerosols, according to a study that took place over nine years and included an interdisciplinary team from Massachusetts Institute of Technology (MIT) and the National Oceanic and Atmospheric Administration (NOAA), among other places.

Knowing this, according to Dan Cziczo, an associate professor of atmospheric chemistry at MIT, will better enable scientists to more fully understand the climatic implications of the clouds in the future.

To collect the data, the team used instruments mounted to the nose of a plane, including a single particle mass spectrometer and a particle collector.

The plane was then flown through cirrus clouds, allowing ice particles to flow through a specialized inlet where they then thawed and left a kernel that could be analyzed onboard in order to identify both size and composition.

According to Cziczo, while mineral dust is often regarded as a natural substance, agriculture, transportation and industrial processes point to the ability of humans to actually change the clouds.

In fact, some global-modeling studies, the scientist said, predict higher dust concentrations in the future due to desertification, land-use change and changing rainfall patterns all due to human activity.

As further evidence of the influence people have on cirrus cloud formation, Cziczo reports that, as a team, they found relatively high levels of lead, zinc and copper.

“These things are very strange metal particles that are almost certainly from industrial activities, such as smelting and open-pit burning of electronics,” he said.

The team observed very little biological particles, however, including bacteria and fungi or even back carbon emitted from cars and smokestacks.

Knowing this, according to NOAA's Karl Froyd, is crucial in developing accurate climate change models.

“There’s been a lot of research efforts spent on looking at how these particle types freeze under various conditions,” he said. “Our message is that you can ignore those, and can instead look at mineral dust at as the dominant driving force for the formation of this type of cloud.”

Funding for the study came from NASA and the National Science Foundation.