Nicola Carslaw



I was appointed as a Lecturer in the Department of Environment and Geography in November 2000, became Senior Lecturer in 2008, and then promoted to Reader in October 2014. My research interests are in the general fields of atmospheric and indoor air chemistry. My work focuses on using detailed chemical models to try and understand the chemical processing that occurs both indoors and outdoors. Through gaining an understanding of such processes, abatement policies can be based on sound scientific principles. I am a member of the editorial board of Atmospheric Environment, as well as of the UK Indoor Environment Group Committee and an EU working Group on Reactive Indoor Air Chemistry.


Senior Lecturer Department of Environment and Geography, University of York
PhD East Anglia
MSc East Anglia
BSc East Anglia



Mace Head, Eire

My major research activity is in the numerical modelling of atmospheric chemistry, both outdoors in the boundary layer, but also in the indoor environment. The outdoor modelling work is often in support of highly instrumented field campaigns, which have taken place in urban areas such as Birmingham and downwind of London in the UK, as well as more remote areas such as Cape Grim, Tasmania and Mace Head on the west coast of Eire. More recently, we have been involved in the OP3 project in Malaysia. During such field campaigns, the atmosphere is sampled by a number of ground-based and sometimes aircraft-based instruments, to determine the concentrations of many important atmospheric species.

Cape Grim, Tasmania

The field measurements, carried out in conjunction with both national and international partners, provide a wide range of input data for the models. The models can then be used to gain insight into atmospheric chemistry processes and once validated, used to predict future events.

Evening Standard cover - 2003 heat wave 'Gasping'

We currently work on a number of projects related to field campaigns, such as the NERC-funded TORCH (Tropospheric ORganic CHemistry Experiment) programme, which took place in July and August of 2003 at Writtle in Essex. Coincidentally, the south of England was subjected to an intense heat-wave during this period, with record temperatures of 38°C. The heat-wave was associated with high concentrations of atmospheric pollutants and it has been estimated that around 800 excess deaths were caused by the high concentrations of ozone and particulate matter (Stedman, J.R., Atmospheric Environment, 38, 1087-1090, 2004). The heat wave received much publicity at the time.

The TORCH campaign enabled us to model the complex chemistry that occurs in the atmosphere downwind of urban areas. In particular, we are interested in the key reactions driving the radical chemistry as an urban plume ages. Using our detailed chemical model, we have been able to reproduce the OH concentrations made by a dedicated instrument over most days of the campaign (Emmerson et al., 2007).

Further analysis has enabled us to learn much about chemical processing during such conditions and work in this area is still ongoing.

Using data from the NERC SOAPEX II (Southern Ocean Atmospheric Photochemistry EXperiment II) and NAMBLEX (North Atlantic Marine Boundary Layer EXperiment) programmes, we have been able to investigate the chemistry of clean air in the marine boundary layer (see Sommariva et al., 2004, 2006; Haggerstone et al., 2005). Again, the emphasis is on understanding radical chemistry. In particular, we are investigating new ways to represent the heterogeneous loss of HOX radicals in a chemical model. For instance, the figure below shows various model predictions of HO2 and the measurements. With subsequently more detailed treatments of HO2 loss onto aerosol surfaces in the model (from T1 to T4), the model predictions become much closer to the measured values (Haggerstone et al., 2005).

The project "Oxidant and particle photochemical processes above a South-East Asian tropical rain forest" (OP3) is a three year scientific research project funded by the Natural Environment Research Council, for the period from 1 October 2007 to 30 September 2010. The overall goal of the project is to provide a better understanding of the interactions that exist between natural forests and the Earth's climate system. It has the following specific objectives:

i. to understand how emissions of reactive trace gases from a tropical rain forest mediate the regional scale production and processing of oxidants and particles, and

ii. to better understand the impact of these processes on local, regional and global scale atmospheric composition, chemistry and climate.

The field elements of the project were based at the Bukit Atur Global Atmospheric Watch research station in Sabah, Malaysia and at the nearby Danum Valley Field Centre (the latter seen below from the research aircraft).

Danum Valley Field Centre

Measurements were made of emission rates of compounds from the forest canopy and of atmospheric chemical composition, both ground based and from the aircraft. Simon Malpass is a NERC-funded PhD student in my group, using these data in models that simulate the local chemistry to try and understand the atmospheric processing in this part of the world. As much of the region is currently being converted from native rainforest to palm oil plantations, it is essential that we try and understand what human perturbations can do to a natural environment such as this one.

My other research focus is on indoor air chemistry. Despite the fact that people in the developed world spend around 90% of their time indoors, there are no regulations for indoor air quality and relatively little is known about it. Most of the work in this area is driven by model predictions as there are relatively few indoor air measurements when compared to outdoors. My main contribution to this field to date has been to develop a new detailed chemical model for indoor air, using the expertise I have gained through my modelling work in the outdoor atmosphere (Carslaw, 2007). Unlike previous models for indoor air, it considers the chemical breakdown of each indoor species explicitly, rather than lumping species together, or working on a subset of the chemistry as has been the tendency in the past. More latterly, I have been adding the reactions that form particles in indoor environments.

The new model has produced some surprising results. The first is that despite the absence of sunlight indoors, there are still appreciable quantities of the OH radical indoors - comparable to outdoors at night-time or in winter, but about a factor of ten lower than summer outdoor concentrations.

The OH found indoors is produced largely through reactions of ozone with terpenes (found commonly in paints, fragrances, cleaning products and furnishing to name but a few). These reactions also produce fine particles indoors, which are a major concern for health. The particles indoors are predicted to contain nitrated and organic material and may adversely change the toxicological properties of the particles (e.g. see Oberdorster, G., Phil. Trans. R. Soc. Lond. A., 2000, 358, 2719-2740. Kavouras et al., EST, 1999, 33, 1028-1037).

In the coming months, the model will be used to elucidate further features of the chemical processing indoors.


Large consortium proposal for ~£2M, co-I (£69,460)
OP3 - Oxidant and particle photochemical processes above a south-east Asian tropical rain forest: NE/D002117/1
Anniversary lectureship, University of York
Environment and health: understanding the drivers of indoor air chemistry
Case studentship with City of York council (£62,109)
Local and regional contributions to NO2 concentrations in urban areas of the UK: NER/S/A/2004/12479
Large consortium proposal for £878,352, co-I (£75,123)
TORCH - Tropospheric Organic CHemistry Experiment: NER/T/S/2002/00498


Current students

2007-2010 Simon Malpass Oxidant and particle photochemical processes above a South-East Asian tropical rain forest

Recent students

2001-2005 Anne-Louise Haggerstone (Jointly supervised with Dr. Lucy Carpenter in the Department of Chemistry) Modelling radical chemistry during the SOAPEX campaign
2004-2007 Emily Westmoreland (NERC CASE student with City of York Council) Local and regional contributions to NO2 concentrations in the city of York



  • Current Topics in Environmental Science (year 1)
  • Climate Change: Science, Observations and Impacts (year 2)
  • Current Issues in Atmospheric Science (year 3)
Carslaw, Nicola

Contact details

Dr Nicola Carslaw
Department of Environment and Geography
University of York
YO10 5NG

Tel: 01904 324777