What’s on : Lectures

Atmospheric Chemistry in the 21st Century

Lectures
Date
5 Apr 2016
Start time
7:30 PM
Venue
Tempest Anderson Hall
Speaker
Prof Lucy Carpenter

Event Information

A lecture by Professor Lucy Carpenter, Wolfson Atmospheric Chemistry Laboratory, Department of Chemistry, University of York

Atmospheric chemistry is a relatively new science; the discovery of reactive components in the atmosphere and the chemical reactions that control them occurred in the 20th century.    From the development of the spectrophotometer and the first measurements of total column ozone by Dobson in 1924, atmospheric chemists now have a myriad of tools to probe the atmosphere, from satellite instruments for global monitoring, airborne drones to capture chemistry from the surface to the stratosphere, miniaturized sensors for networked observations, and highly complex computer models capable of simulating thousands of chemical species and reactions.   This level of information is required to address the major challenges of atmospheric chemistry today, which are to understand and predict the very large impact human activities have on the state of the atmosphere, to describe the relationships and feedbacks between chemistry and climate, and to understand the exchange processes between the surface and the atmosphere. Professor Lucy Carpenter will describe how she and her colleagues search for large scale changes in atmospheric composition and have discovered some key feedbacks between surface ocean chemistry and gaseous pollutants.

Member’s report

Interactions between the atmosphere and the oceans play a key role in regulating the composition of the atmosphere, and climate. The part played by the major greenhouse gases, carbon dioxide and methane, is quite well understood. Many substances, released by human activity, are present in the atmosphere in minuscule amounts but may nevertheless have major effects. Very sophisticated methods now make it possible to measure such trace gases at concentrations as low as a few parts per trillion (~1/1,000,000,000), enabling an understanding of atmospheric chemistry never before possible.

Lucy Carpenter guided us through some of the insights she and her team have been developing into the complexities of atmospheric chemistry. Ozone, a form of oxygen, in the upper atmosphere absorbs ultraviolet radiation, protecting the living world beneath. Human-generated CFCs react with ozone and destroy it, and over a number of years dangerously reduced this protective layer. Rapid international action to reduce CFC emissions turned the tide, and over a period of decades the protective ozone layer has largely recovered.

But the ozone story is much more complex than this. Although upper atmosphere ‘good’ ozone is beneficial, at ground level it is harmful. This ‘bad’ ozone has trebled over the last century or so.  Much of the work of Professor Carpenter’s lab is devoted to teasing out the dynamics of surface ozone, and its interactions with the ocean, and with human emissions, particularly nitrogen oxides (Nox) and volatile organic compounds (VOCs). The surface of the ocean is critical: ozone is broken down here, by substances produced by microscopic algae as well as by reacting with VOCs. Understanding these interactions is critically important.

Such atmospheric complexity can be understood only by deploying sensitive instruments worldwide, and using phenomenal computer power to elucidate the interactions, and to predict future changes – as well as to develop effective remedial action.

Enthralling insights into an exciting and important field of research.

Peter Hogarth