Geoengineering and Ozone

The idea of geoengineering solutions to future climate change risks really appeals to me. Images of futuristic ships spraying aerosols into the stratosphere, reflective balloons ascending and man made clouds forming all sound like science fiction coming to fruition. However, with developing scientific knowledge and engineering capabilities, the need for research into testing and validating geoengineering methods along with their uncertainties and side effects are hugely important.

Simone Tilmes et al 2009 investigated the impact of geoengineered aerosols using a coupled chemistry climate model that predicted atmospheric changes from 2020 to 2050. Based on the injection of liquid sulphate aerosols (similar to that produced by volcanic eruptions) Tilmes et al assumed a constant stratospheric distribution. Of particular interest to me was their results in relation to projected ozone depletion.

The conclusion of the research was that the introduction of sulphate aerosols led to the increase of heterogeneous reactions in the stratosphere. In turn this caused the enhancement of the ozone depleting chlorine cycle over Antarctica. It was predicted that compared to a baseline scenario, the geo-engineering method resulted in delaying the recovery of the Antarctic ozone hole by 20-30 years.

Furthermore, models suggested Arctic ozone depletion rates would be larger than currently observed between 2040-2050 due to a modelled increase in the strength of the polar vortex (briefly explained in my blog The basics of ozone depletion). In addition to this, a predicted one to two fold increase in ozone depletion in the northern hemisphere could be expected.

Although the study did find an overall cooling of the troposphere with this geoengineering method it is clear from the issues arising with ozone depletion that problems may outweigh the benefits. When an increase of UV rays and delaying of the recovery of the ozone hole is considered there is certainly much for policy makers to ponder when addressing the issue of geo-engineering climate. In relation to the “Anthropocene” as a whole, this is certainly a stark example of problems we will encounter through man's role as “Stewards of the Earth System” described by Will Steffen et al.