Criegee biradicals, invisible chemical intermediates, are powerful oxidizers of pollutants such as nitrogen dioxide and sulfur dioxide produced by combustion and can naturally clean up the atmosphere. Sounds like fiction, right? These chemical intermediates were first postulated by Rudolf Criegee in the 1950s but researchers now say that they have been detected and with further research could play a major role in off-setting climate change.

The detection of the Criegee biradical and measurement of how fast it reacts was made possible by an apparatus that uses light from a third-generation synchrotron facility at the Lawrence Berkeley National Laboratory’s Advanced Light Source. The intense, tunable light from the synchrotron allowed researchers to discern the formation and removal of different isomeric species – molecules that contain the same atoms but arranged in different combinations.

The researchers found that the Criegee biradicals react more rapidly than first thought and will accelerate the formation of sulphate and nitrate in the atmosphere. These compounds will lead to aerosol formation and ultimately to cloud formation with the potential to cool the planet.

In the last 100 years, Earth's average surface temperature has increased by up to 0.8 °C with about two thirds of the increase occurring over just the last three decades, though the last three decades were the first to have accurate measurements. Regardless of the accuracy of temperature measurement in the past, scientists agree that future global warming should be limited to below 2.0 °C (3.6 °F). 

Dr Carl Percival, Reader in Atmospheric Chemistry at The University of Manchester and one of the authors of the paper in Science, believes there could be significant research possibilities arising from the discovery of the Criegee biradicals.  “Criegee radicals have been impossible to measure until this work carried out at the Advanced Light Source. We have been able to quantify how fast Criegee radicals react for the first time. Our results will have a significant impact on our understanding of the oxidising capacity of the atmosphere and have wide ranging implications for pollution and climate change. The main source of these Criegee biradicals does not depend on sunlight and so these processes take place throughout the day and night.”

Professor Dudley Shallcross, Professor in Atmospheric Chemistry at The University of Bristol, added, “A significant ingredient required for the production of these Criegee biradicals comes from chemicals released quite naturally by plants, so natural ecosystems could be playing a significant role in off-setting warming."

Citation: Oliver Welz, John Savee, David Osborn, Subith Vasu, Carl Percival, Dudley Shallcross and Craig Taatjes, 'Direct Kinetic Measurements of Criegee Intermediate (CH2OO) Formed by Reaction of CH2I with O2', Science January 2012