Thank you for your comment. Yes — clouds and aerosols are big unknowns, and there is active work being done on both here at UCAR in the National Center for Atmospheric Research (NCAR), at NASA and other government labs, and in the universities. Not just with computer models, but with satellites (including the new Cloudsat and CALIPSO satellites), observations from aircraft, and from on the ground. The GLOBE sun photometer developed by you and David Brooks is still playing a part in this research — so students are playing a part, too.

Also, there is research that has shown that contrails have contribute to the mix. When the air is humid at jet level, contrails stick around, spread out, and if you watch long enough, turn into layers of clouds. GLOBE contrail observations are helping us to understand better what is going on there.

On a side note, it is ironic that you mentioned Steve Schneider’s work from the early 1970s. He was the “it is getting colder” NCAR person I was referring to in the last blog!

Best Wishes,

Peggy

The big unknown is the role of clouds and aerosols. Consider that while carbon dioxide has been steadily rising year after year, major northern hemispheric cooling occurred from the 1940s to the 1970s. A paper in the journal SCIENCE even predicted the possibility that increasing aerosols in the atmosphere might “…trigger an ice age!” (Rasool and Schneider, 1971.) Was the cooling caused by increased particulate matter from power plants, factories and forest fires? Did changes in cloud cover play a role?

This is where GLOBE can provide serious scientific data, for the gradual decline in particulate matter over various regions may result in a rise in temperature. Moreover, an increase in low cloud cover can cause cooling and an increase in high cloud cover can cause warming. GLOBE cloud observations and measurements of temperature, optical depth and column water vapor can provide vital clues about what’s happening to the climate.

Forrest M. Mims III
http://www.forrestmims.org