Dr Ryan Hossaini

NERC Research Fellow

Research Interests

Ryan's research examines long-term changes in the chemistry and composition of Earth’s atmosphere and how such changes may influence climate. This involves the development and application of state-of-the-art numerical models, run on supercomputers, which simulate the past, present and future state of the atmosphere. His recent work has focussed on:

  • Non-Montreal Protocol Ozone-Depleting Substances (ODSs). Despite production of many long-lived ODSs (e.g. CFCs) being controlled by the UN Montreal Protocol and its amendments, ozone depletion remains a persistent environmental issue. Our research examines trends in the atmosphere abundance of so-called Very Short-Lived Substances (VSLS) – a class of ODSs not controlled by the Protocol – whose emissions have been increasing in recent years. Our recent Nature Comms. paper highlighted the increasing threat to stratospheric ozone from anthropogenic VSLS emissions. See also recent Nature review on ozone layer recovery.
  • Ozone Chemistry-Climate Interactions. In the stratosphere, ozone prevents damaging levels of UV radiation reaching Earth’s surface. Ozone also absorbs terrestrial IR radiation and is therefore a greenhouse gas. Changes in can ozone exert a significant and complex influence on climate. This research seeks to understand chemical drives of ozone changes, particularly in the climate-relevant upper troposphere/lower stratosphere, and the radiative implications. See our recent Nature Geoscience paper on the efficiency of halogenated VSLS at influencing climate through ozone loss in the lower stratosphere.
  • Tropospheric Chlorine Impacts. Chlorine atoms are highly reactive in the troposphere and are therefore a potentially important atmospheric oxidant, influencing the lifetime of greenhouse gases (e.g. methane) and a range of volatile organic compounds. Despite this, the tropospheric abundance of chlorine atoms is very poorly known. Our work seeks to understand processes governing the release and recycling of chlorine in the troposphere and we are building models to simulate and provide insight into such processes.
  • Data-Driven Clustering Methods for Climate Science. This work is supported by the EPSRC to explore the use of clustering in the analysis of large climate model datasets from model intercomparison projects. Our recent work has shown that clustering can potentially provide powerful insight into such data, and may help characterise areas of uncertainty across models.

  • Atmosphere, Climate and Pollution