Ozone depleting substance to be on rise

A study published (6 November 2014) in Nature reports of a recent increase in atmospheric hydrogen chloride (HCl), a signature of the presence of ozone-destroying chemicals. The study shows that this unexpected increase has occurred in the Northern hemisphere since 2007, as a result of a temporary but prolonged anomaly in atmospheric circulation. This circulation change has led to a transient reversal in the decline of HCl which would be expected under the Montreal Protocol.

HCl relative rates of change for eight NDACC sites.

Figure 1. HCl relative rates of change for eight NDACC sites. The panels provide the rates of change (%/year) either for the 1997-2007 (1999-2007 for Thule and Izana, 1998-2007 for Tsukuba) or 2007-2011 time period. The rates of change were derived from the FTIR and GOZCARDS observational data sets and from the two SLIMCAT simulated time series (see legend for colour code). The error bars correspond to the 2-σ level of uncertainty. (Click to view larger image.)

Read the full press release, or view a summary of the research findings.

Short title: 
Unexpected Reversal of Northern Hemisphere Stratospheric Chlorine Burden
HCl rates




ACOM | Atmospheric Chemistry Observations & Modeling