Personal

I am Professor of Atmospheric Chemistry at Lancaster University. I hold a Royal Society Wolfson Research Merit Award. I am a Fellow of the Royal Society of Chemistry.

RESEARCH

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, including volatile organic compounds, to the Earth’s atmosphere. Biogenic volatile organic compounds 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. I was PI of a large NERC consortium project studying the role of bVOCs in atmospheric composition and chemistry above a tropical rain forest in Malaysia (the “OP3” project – see the OP3 special issue in the journal Atmospheric Chemistry and Physics and other papers, including our 2009 paper in PNAS and our 2011 paper in Nature Geoscience).

Recently we have begun to study the effects of biofuel cultivation on atmospheric composition in the mid-latitudes as well as in tropical regions (see our 2013 paper in Nature Climate Change). We have also studied the effects of vegetation on urban air quality (see our 2012 paper in Environmental Science and Technology).

Current work in the area of biosphere-atmosphere interactions includes measuring isoprene fluxes from a forest canopy in Amazonia using tower-based disjunct virtual eddy covariance and developing an airborne flux measuring capability that we hope we will be able to use over tropical forests.

NERC’s BAe 146 Facility for Airborne Atmospheric Measurements (FAAM) passing the Bukit Atur Global Atmosphere Watch station in Danum Valley, Malaysia during the OP3 project in 2008 (photo: Martin Irwin).

Ground level ozone concentrations estimated using a box model of atmospheric chemistry for the rainforest and oil palm landscapes in Malaysia (see Hewitt et al., 2009, PNAS for details.

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 now collaborate with Andy Jarvis at Lancaster on understanding the behaviour of global energy use and CO₂ emissions. In our first joint paper (Nature Climate Change, 2012) 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. We are currently studying the global energy network and its behaviour. As a small side-line I have also recently attempted to quantify the influence of realistic dietary choices on greenhouse gas emissions (see 2012 paper in Energy Policy).

Teaching at Lancaster

ENV231. INTRODUCTION TO ATMOSPHERIC COMPOSITION (2^nd year module)

ENV332. AIR QUALITY AND CLIMATE (3^rd year module)

ENV457. AIR QUALITY AND CLIMATE (4^th year module)

Meetings recently organised

Co-convener and chair, Workshop, “BVOC emissions models and their applications”, Lancaster, 2011

Chair and convener, Workshop “Forest fluxes and climate change”, Kuala Lumpur, 2007

Co-chair and co-convener, Royal Society Discussion meeting on “The biogeochemistry of trace gases and their role in climate change”, London, 2006

SELECTED publications (since 2008) (please contact me for PFDs or for a full publication list)

· Impacts of biofuel cultivation on mortality and crop yields (2013) K Ashworth, O. Wild and C.N. Hewitt, Nature Climate Change doi: 10.1038/nclimate1788

· Climate-society feedbacks and the avoidance of dangerous climate change (2012) A.J. Jarvis, D.T. Leedal and C.N. Hewitt, Nature Climate Change, 2, 668 – 671 doi:10.1038/nclimate1586

· Scenario archetypes: Converging rather than diverging themes (2012) D. Hunt, R. Lombardi, S. Atkinson, A. Barber, M. Barnes, C. Boyko, J. Brown, J. Bryson, D. Butler, S. Caputo, M. Cesario, R. Coles, R. Cooper, R. Farmani, M. Gaterell, J. Hale, C. Hales, C.N. Hewitt, L. Jankovic, I. Jefferson, J. Leach, A.R. MacKenzie, F. Memon, T.A.M. Pugh, J. Sadler, C. Weingartner, D. Whyatt, C. Rogers, Sustainability, 4, 740 - 772 doi:10.3390/su40x000

· The effectiveness of green infrastructure for improvement of urban air quality (2012) T.A.M. Pugh, A.R. MacKenzie, J.D. Whyatt and C.N. Hewitt, Environmental Science and Technology, 46, 7692 – 7699 doi: 10.1021/es300826w

· Impacts of near-future cultivation of biofuel feedstocks on atmospheric composition and local air quality (2012) K Ashworth, G. Folberth, C.N. Hewitt and O. Wild, Atmospheric Chemistry and Physics, 12, 919 – 939

· A Lagrangian model of air-mass photochemistry and mixing using a trajectory ensemble: the Cambridge Tropospheric Trajectory model of Chemistry And Transport (CiTTyCAT) version 4.2 (2012) T. A. M. Pugh, M. Cain, J. Methven, O. Wild, S. R. Arnold, E. Real, K. S. Law, K. M. Emmerson, S. M. Owen, J. A. Pyle, C. N. Hewitt and A. R. MacKenzie, Geoscientific Model Development, 5, 193 – 221, doi:10.5194/gmd-5-193-2012

· The relative greenhouse gas impacts of realistic dietary choices (2012) M. Berners-Lee, C. Hoolohan, H. Cammack and C.N. Hewitt, Energy Policy, 43, 184 – 190, doi 10.1016/j.enpol.2011.12.054

· Atmospheric chemistry and physics in the atmosphere of a developed megacity (London): an overview of the REPARTEE experiment and its conclusions (2012) R.M. Harrison, M. Dall’Osto, D.C.S. Beddows, A.J. Thorpe, J. Allan, H. Coe, J. Dorsey, M. Gallagher, C. Martin, J. Whitehead, P. Williams, A.K. Benton, R.L. Jones, J. Langridge, S. Ball, B. Langford, C.N. Hewitt, B. Davison, D. Martin, K. Petersson, S.J. Henshaw, I.R. White, D.E. Shallcross, J.F. Barlow, T. Dunbar, F. Davies, E. Nemitz, G. Phillips and C. Helfter, Atmospheric Chemistry and Physics, 12, 3065 - 3114

· Ground-level ozone influenced by circadian control of isoprene emissions, C.N. Hewitt, K. Ashworth, A. Boynard, A. Guenther, B. Langford, A.R. MacKenzie, P.K. Misztal, E. Nemitz, S.M. Owen, M. Possell, T.A.M. Pugh, A.C. Ryan and O. Wild (2011) Nature Geoscience, 4, 671 – 674, doi:10.1038/ngeo1271

· Isoprene emissions from plants are mediated by atmospheric CO₂ concentrations (2011) M. Possell and C.N. Hewitt, Global Change Biology, 17, 1595 – 1610

· Direct ecosystem fluxes of volatile organic compounds from oil palms in South-East Asia (2011) P. K. Misztal, E. Nemitz, B. Langford, C. F. Di Marco, G. J. Phillips, C. N. Hewitt, A. R. MacKenzie, S. M. Owen, D. Fowler, M. R. Heal, and J. N. Cape, Atmospheric Chemistry and Physics, 11, 8995 - 9017

· Quantification of VOC emission rates from the biosphere (2011) C. N. Hewitt, T. Karl, B. Langford, S.M. Owen and M. Possell, Trends in Analytical Chemistry, 30, 937 – 944, doi 10.1016/j.trac.2011.03.008

· The impact of local surface processes in Borneo on atmospheric composition at wider spatial scales: coastal processes, land use change and air quality (2011) J. A. Pyle, N. J. Warwick, N. R. P. Harris, M. R. Abis, A. Archibald, M. J. Ashfold, K. Ashworth, M. P. Barkley, G. D. Carver, K. Chance, J. Dorsey, D. Fowler, S. Gonzi, B. Gostlow, C.N. Hewitt, T. P. Kurosu, J. D. Lee, B. Langford, G. Mills, S. Moller, A.R. MacKenzie, A. J. Manning, P. Misztal, M. S. M. Nadzir, E. Nemitz, H. Newton, L. M. O’Brien, S. Ong, D. Oram, P. I. Palmer, L. K. Peng, S. M. Phang, R. Pike, T. A. M. Pugh, N. A. Rahman, A. D. Robinson, J. Sentian, A. A. Samah, U. Skiba, H. E. Ung, S. E. Yong and P. Young, Philosophical Transactions of the Royal Society of London B, 366, 3210 – 3224, doi:10.1098/rstb.2011.0060

· Effects of land use on surface–atmosphere exchanges of trace gases and energy in Borneo: comparing fluxes over oil palm plantations and a rainforest (2011) D. Fowler, E. Nemitz, P. Misztal, C. Di Marco, U. Skiba, J. Ryder, C. Helfter, J.N Cape, S.M. Owen, j. Dorsey, M. W. Gallagher, M. Coyle, G. Phillips, B. Davison, B. Langford, A.R. MacKenzie, J. Muller, J. Siong, C. Dari-Salisburgo, P. Di Carlo, E. Aruffo, F. Giammaria, J. A. Pyle and C.N. Hewitt, Philosophical Transactions of the Royal Society of London B, 366, 3196 – 3209, doi:10.1098/rstb.2011.0055

· The atmospheric chemistry of trace gases and particulate matter emitted by different land uses in Borneo (2011) A.R. MacKenzie, B. Langford, T.A.M. Pugh, N. Robinson, P.K. Misztal, D.E. Heard, J. D. Lee, A. C. Lewis, C. E. Jones, J. R. Hopkins, G. Philips, P. S. Monks, A. Karunaharan, K. E. Hornsby, V. Nicolas-Perea, H. Coe, A. M. Gabey, M. W. Gallagher, L.K. Whalley, P. M. Edwards, M. J. Evans, D. Stone, T. Ingham, R. Commane, K. L. Furneaux, J. McQuaid, E. Nemitz, Yap Kok Seng, D. Fowler, J. A. Pyle, and C.N. Hewitt, Philosophical Transactions of the Royal Society of London B, 366, 3177 – 3195, doi: 10.1098/rstb.2011.0053

· The influence of small-scale variations in isoprene concentrations on atmospheric chemistry over a tropical rainforest (2011) T.A.M. Pugh, A.R. MacKenzie, B. Langford, P.K. Misztal and C.N. Hewitt, Atmospheric Chemistry and Physics 11, 4121-4134

· Isoprene synthesis in plants: lessons from a transgenic tobacco model (2011) C. Vickers, M. Possell, J. Laothawornkitkul, A. Ryan, C.N. Hewitt and P. Mullineaux, Plant Cell and Environment DOI: 10.1111/j.1365-3040.2011.02303.x

· Modelling chemistry in the nocturnal boundary layer above tropical rainforest and a generalised effective nocturnal deposition velocity for sub-ppbv NOx conditions (2010) T.A.M. Pugh, J. Ryder, A.R. MacKenzie, S.J. Moller, J.D. Lee and C.N. Hewitt, Journal of Atmospheric Chemistry, 65, 89 – 110, doi:10.1007/s10874-011-9183-4

· Effects of fosmidomycin on plant photosynthesis as measured by gas exchange and chlorophyll fluorescence (2010) M. Possell, A. Ryan, C. Vickers, P. Mullineaux and C.N. Hewitt, Photosynthesis Research, 104, 49-59, doi 10.1007/s11120-009-9504-5

· Large estragole fluxes from oil palms in Borneo (2010) P. K. Misztal, S. M. Owen, A. B. Guenther, R. Rasmussen, C. Geron, P. Harley, G.J. Phillips, A. Ryan, D.P. Edwards, C.N. Hewitt, E. Nemitz, J. Siong, M.R. Heal, and J.N. Cape, Atmospheric Chemistry and Physics, 10, 4343-4358

· Fluxes and concentrations of volatile organic compounds from a south-east Asian tropical rainforest (2010) B. Langford, P. Misztal, D. Davison, C. Helfter, T.A.M. Pugh, A.R. MacKenzie and C.N. Hewitt, Atmospheric Chemistry and Physics, 10, 8391 - 8412

· Oxidant and particle photochemical processes above a south-east Asian tropical rain forest (the OP3 project): introduction, rationale, location characteristics, tools and overview (2010) C. N. Hewitt, J. D. Lee, A. R. MacKenzie, M. P. Barkley, N. Carslaw, G. D. Carver, N. A. Chappell, H. Coe, C. Collier, R. Commane, F. Davies, B. Davison, P. DiCarlo, C. F. Di Marco, J. R. Dorsey, P. M. Edwards, M. J. Evans, D. Fowler, K. L. Furneaux, M. Gallagher, A. Guenther, D. E. Heard, C. Helfter, J. Hopkins, T. Ingham, M. Irwin, C. Jones, A. Karunaharan, B. Langford, A. C. Lewis, S. F. Lim, S. M. MacDonald, A. S. Mahajan, S. Malpass, G. McFiggans, G. Mills, P. Misztal, S. Moller, P. S. Monks, E. Nemitz, V. Nicolas-Perea, H. Oetjen, D. E. Oram, P. I. Palmer, G. J. Phillips, R. Pike, J. M. C. Plane, T. Pugh, J. A. Pyle, C. E. Reeves, N. H. Robinson, D. Stewart, D. Stone, L. K. Whalley, and X. Yang, Atmospheric Chemistry and Physics, 10, 169 - 199

· Sensitivity of isoprene emissions from the terrestrial biosphere to 20th century changes in atmospheric CO₂ concentration, climate, and land use (2010) J. Lathière, C. N. Hewitt, and D. J. Beerling, Global Biogeochemical Cycles, 24, GB1004, doi:10.1029/2009GB003548

· Fluxes and concentrations of volatile organic compounds above central London, UK (2010) B. Langford, E. Nemitz, E. House, G. Phillips, D. Famulari, B. Davison, J. R. Hopkins, A. C. Lewis, and C.N. Hewitt, Atmospheric Chemistry and Physics, 10, 627-645

· Nitrogen management is essential to prevent tropical oil palm plantations from causing ground level ozone pollution (2009) C.N. Hewitt, A. MacKenzie, P. Di Carlo, C. Di Marco, J. Dorsey, M. Evans, D. Fowler, M. Gallagher, J. Hopkins, C. Jones, B. Langford, J. Lee, A.C. Lewis, S. Lim, J. McQuaid, P. Misztal, S. Moller, P.S. Monks, E. Nemitz, D. Oram, S. Owen, G. Phillips, T. Pugh, J.A. Pyle, C. Reeves, J. Ryder, J. Siong, U. Skiba and D. Stewart, Proceedings of the National Academy of Sciences of the United States of America, 106, 18447 – 18451, doi: 10.1073/pnas.0907541106

· Biogenic volatile organic compounds in the Earth system: a Tansley Review (2009) J. Laothawornkitkul, J.E. Taylor, N.D. Paul and C. N. Hewitt, New Phytologist, 183, 27 – 51, doi: 10.1111/j.1469-8137.2009.02859.x

· Isoprene emission deters plant herbivory (2008) J. Laothawornkitkul, C. Vickers, M. Possell, N. Paul, J. Taylor, P. Mullineaux and C.N. Hewitt, Plant, Cell and Environment, 31, 1410-1415

· The effect of trade between China and the UK on national and global carbon dioxide emissions (2008) Y. Li and C.N. Hewitt, Energy Policy, 36, 1907 - 1914