The long-term evolution of ozone and temperature in the upper stratosphere

We use long-term records of ozone and temperature from multiple ground- and space-based

instruments to investigate the long-term evolution of ozone and temperature in the upper

stratosphere since the 1980s. Over the two decades from 1980 to 2000, chlorine induced ozone

depletion and increasing CO2 have resulted in reduced short-wave heating and increased long-

wave cooling. Both anthropogenic influences have been working in the same direction, producing

an observed cooling of the upper stratosphere. Over the last decade, however, chlorine has

started to decrease, and constant or even slightly increasing ozone has been observed, while

CO2 is increasing steadily. Now increased heating due to increasing ozone is competing with

increased cooling expected from continuing CO2 increase. Good comprehensive long-term records

of temperature in the upper stratosphere are scarce, but the available data show little or no

temperature decline over the last decade. This might be expected from the beginning recovery of

ozone, but chemistry climate model simulations indicate that the upper stratospheric cooling

trend from CO2 should prevail. These model predictions are at odds with the current

observational record, albeit with little statistical significance at this time.

At the meeting we will present updated ozone- and temperature records from ground- and space-based

instruments, and will discuss the observed evolution.