Freshly published research using satellite data has shown that levels of ozone in the lower stratosphere (between 10 and 20 km from the Earth’s surface) are dropping, in a trend that is reportedly consistent with climate change model predictions. Atmospheric Chemistry and Physics published the research led by Dr William Ball at the PMOD World Radiation Centre in Switzerland, using data from a range of satellites over a variety of time periods. Concurrently, ozone levels in the troposphere (closest to the Earth’s surface, below the lower stratosphere) are increasing, and this has led to some speculation that there may be more mixing between the two layers, especially as overall concentrations of ozone in the atmosphere as a whole have been relatively even. Scientists are unsure, however, of the mechanism at play, with another idea being that the higher levels of ozone in the troposphere are being created by NOx released from fossil fuel combustion, as NOx is known to promote the formation of ozone. Further ideas are volcanic activity releasing ozone-destroying sulphur compounds into the lower stratosphere, and ‘very short-lived substances’ (mostly bromine compounds produced by seaweed and the ocean’s phytoplankton) finding their way into the lower stratosphere because of the increased mixing between the troposphere and stratosphere, which has come from higher average global temperatures.