Prof Nick Hewitt

Professor

EMISSIONS OF BIOGENIC REACTIVE TRACE GASES AND THEIR ROLES IN THE EARTH SYSTEM

 

The biosphere is by far the largest source of reactive trace gases to the Earth’s atmosphere. They provide protection against abiotic and biotic stresses and allow plant-to-plant and plant-to-insect communication. Some of these compounds are highly reactive in the gas phase, and some are emitted in enormous, but unknown, quantities. The combination of high reactivity and large mass emission rates means these compounds play major roles in the physics and chemistry of the atmosphere. They mediate in the formation of ozone, hydroxyl and other oxidants, so controlling the oxidizing capacity of the atmosphere, which in turn controls the lifetime of methane and other radiatively-active “greenhouse” gases. They also form secondary organic aerosol (SOA) particles, which can directly influence the radiative balance of the atmosphere. SOA may activate cloud condensation nuclei (CNN), and by modifying cloud formation and properties can have indirect effects on climate. As well as their effects on radiative forcing, both ozone and aerosol particles have detrimental effects on human health and ecosystem functioning, and hence bVOCs play a role not only in the Earth’s climate system but also in air quality.

My research on bVOCs spans scales from the cell to the globe and includes both experimental and modelling work. Recently I was PI of a large NERC consortium studying the role of bVOCs in atmospheric composition and chemistry above a tropical rain forest in Malaysia (the “OP3” project – see OP3 special issue in ACP and other papers, including our 2009 paper in PNAS) and I now am preparing for a two new projects. In the first we will be measuring isoprene fluxes in Amazonia over 12 months. In the second (also funded by NERC) we are developing the ability to measure hydrocarbon fluxes from the surface to the atmosphere at the landscape scale using a mass spectrometer on a light airplane (the NERC ARSF Dornier 228).

CLIMATE-SOCIETY FEEDBACKS AND THE AVOIDANCE OF CLIMATE CHANGE

I have become very interested in how both individual actions and societal choices might influence atmospheric composition and hence climate. Having discovered the work of William Jevons and his paradox (his 1865 book “The Coal Question” is available on the web) I have recently begun collaborating with Andy Jarvis at Lancaster on climate–society feedbacks and the avoidance of climate change. We show that effective climate mitigation will require establishing a meaningful climate-society feedback to arrest the growth in global CO2 emissions through decarbonising global primary energy sources. In our current joint work we are exploring how the global energy system and CO2 emissions have co-evolved. I have also recently attempted to quantify the influence of realistic dietary choices on greenhouse gas emissions.

 

I am a Royal Society Wolfson Research Merit Award holder.