NASA-2014USA: Scientists suspect refrigerant manufacturing plants may have cleaned up their act after seeing a sudden drop in atmospheric concentrations of HCFC133a, a precursor of R134a.

HCFC133a, the main component in the manufacture of R134a, was first identified last year as one of four previously undetected ozone-depleting gases in the atmosphere. Concentrations of the gas, which were rising rapidly, have now suddenly dropped.

New measurements show that after a rapid increase of the compound in the atmosphere of the northern hemisphere from 0.13ppt in 2000 to 0.50ppt in 2013, the concentration suddenly dropped to about 0.44ppt by early 2015. This drop in concentration is said to be equivalent to a 50% decline in global emissions from 3,000 tonnes in 2011 to about 1,500 tonnes in 2014.

“That change tells us a lot,” said Martin Vollmer of the Swiss Federal Laboratories for Materials Science and Technology and the lead author on a new paper reporting the findings, which has been accepted for publication in the AGU journal Geophysical Research Letters.

“If the compound was being installed in a refrigerator or as foam in seat cushions, it would be leaking out slowly over time and the concentration in the atmosphere would not have changed so quickly, he said. “So this has to be something that humans have immediate control of,” Vollmer said.

Vollmer and his colleagues suspect that the source of HCFC133a is the mass production of R134a.

“That’s most likely the biggest source of HCFC133a currently,” Vollmer said. “But it’s not known how much leaks out. We expected HCFC133a to grow rapidly in the atmosphere because of the enormous and growing global demand and production of HFC134a, but we found the opposite. One of our speculations is that there are one, two or three factories that have been grossly emitted HCFC133a but were cleaned up.”