Depletion of stratospheric ozone allows larger doses of harmful solar ultraviolet (UV) radiation to reach the surface leading to increases in skin cancer and cataracts in humans and other impacts, such as crop damage. Ozone also affects the Earth's radiation balance and, in particular, ozone depletion in the lower stratosphere (LS) exerts an important climate forcing. While most long-lived ozone-depleting substances (ODSs, e.g. chlorofluorocarbons, CFCs) are now controlled by the United Nations Montreal Protocol and their abundances are slowly declining, there remains significant uncertainty surrounding the rate of ozone layer recovery. Although signs of recovery have been detected in the upper stratosphere and the Antarctic, this is not the case for the lower stratosphere at middle and low latitudes. In fact, contrary to expectations, ozone in this extrapolar lower stratosphere has continued to decrease (by up to 5% since 1998). The reason(s) for this are not known, but suggested causes include changes in atmospheric dynamics or the increasing abundance of short-lived reactive iodine and chlorine species. We will investigate the causes of this ongoing depletion using comprehensive modelling studies and new targeted observations of the short-lived chlorine substances in the lower stratosphere. While the Montreal Protocol has controlled the production of long-lived ODSs, this is not the case for halogenated very short-lived substances (VSLS, lifetimes <6 months), based on the belief that they would not be abundant or persistent enough to have an impact. Recent observations suggest otherwise, with notable increases in the atmospheric abundance of several gases (CH2Cl2, CHCl3), due largely to growth in emissions from Asia. A major US aircraft campaign based in Japan in summer 2021 will provide important new information on how these emissions of short-lived species reach the stratosphere via the Asian Summer Monsoon (ASM). UEA will supplement the ACCLIP campaign by making targeted surface observations in Taiwan and Malaysia which will help to constrain chlorine emissions. The observations will be combined with detailed and comprehensive 3-D modelling studies at Leeds and Lancaster, who have world-leading expertise and tools for the study of atmospheric chlorine and iodine. The modelling will use an off-line chemical transport model (CTM), ideal for interpreting observations, and a coupled chemistry-climate model (CCM) which is needed to study chemical-dynamical feedbacks and for future projections. Novel observations on how gases are affected by gravitational separation will be used to test the modelled descriptions of variations in atmospheric circulation. The CTM will also be used in an 'inverse' mode to trace back the observations of anthropogenic VSLS to their geographical source regions. The models will be used to quantify the flux of short-lived chlorine and iodine species to the stratosphere and to determine their impact on lower stratospheric ozone trends. The impact of dynamical variability will be quantified using the CTM and the drivers of this determined using the CCM. The model results will be analysed using the same statistical models used to derive the decreasing trend in ozone from observations, including the Dynamical Linear Model (DLM). Overall, the results of the model experiments will be synthesised into an understanding of the ongoing decrease in lower stratospheric ozone. This information will then be used to make improved future projections of how ozone will evolve, which will feed through to the policy-making process (Montreal Protocol) with the collaboration of expert partners. The results of the project will provide important information for future international assessments e.g. WMO/UNEP and IPCC reports.

The science behind climate change has been established, and now the mitigation of climate change has become a political puzzle. We need to act quickly to mitigate the worst impacts of climate change, and so this project is designed to find and then share effective policy solutions that can be used across society. Until very recently, attempted solutions for climate change were 'top down': for example, the United Nations organised annual conferences, and those countries responsible for producing the most greenhouse gases dominated these negotiations. However, this approach for dealing with climate change has failed to generate effective change quickly enough, and academics are looking for new governance solutions for this most pressing and significant of issues. Increasingly, scholars argue that we need to be improving policy-making the local level, and empowering a wide range of people take a lead in responding to climate change. In particular, they argue we need 'polycentric governance'. Polycentric governance involves businesses, NGOs and government agencies working independently of each other, while also overlapping and coordinating with one another, as part of complex, multi-level networks. The outcome should be that no individual group or organisation is solely responsible for mitigating climate change, and so every 'node' in the network is encouraged to fulfil its part without fearing being exploited by others. Yet, despite growing support amongst academics for polycentric governance, there is limited research into how these networks can be created, or whether they even have a positive impact in mitigating climate change. This research project seeks to address that lack of knowledge by pursuing two research objectives. First, the project will explain how and why polycentric models are developed, by analysing three key factors: the role of the European Union; the impact of a country's national governance model, such as the presence of federalism; and a city's status as a country's capital or not. To do so, the project will map out the interconnecting networks of different groups and individuals within six city regions in Germany, Sweden and the UK. These three countries were similarly ambitious towards climate change in the early 2010s, and the six city regions have been carefully selected to be as similar as possible, while also showing differences in the three key factors under exploration. Second, the project will then determine how and why these different city regions' polycentric practices affect the creation of ambitious climate change policies. This goal will be achieved by analysing the climate policy documents of a wide range of actors within each city region, as well as interviewing key individuals. Here, a useful extra outcome of the research will be the ability to explore how changes in the UK's political landscape during the Brexit negotiations have influenced local climate change policy too. Having then analysed how and why different governance models shape the ambitiousness of local climate policy, guidance will be created for policy-makers across Western Europe. This advice will inform policy-makers about which types of governance initiatives are most effective for helping to create more ambitious climate policy. The advice will seek to improve climate policy at the local level, and it will be designed with multiple audiences in mind, depending on whether policy-makers and practitioners work at the local, national or European level. As a result, this project aims to help every level of governance to be more effective at mitigating climate change. Finally, this project will also seek to inform and empower citizens about how they can effect change themselves, by sharing the results of the study via a wide range of media outlets, pitching a TV programme on the topic, and by giving several public lectures.

Over the past few months, we have laid the groundwork for the ReproHum project (summarised in the 'pre-project' column in the Work Plan document) with (i) a study of 20 years of human evaluation in NLG which reviewed and labelled 171 papers in detail, (ii) the development of a classification system for NLP evaluations, (iii) a proposal for a shared task for reproducibility of human evaluation in NLG, and (iv) a proposal for a workshop on human evaluation in NLP. We have built an international network of 20 research teams currently working on human evaluation who will actively contribute to this project (see Track Record section), making combined contributions in kind of over £80,000. This pre-project activity has created an advantageous starting position for the proposed work, and means we can 'hit the ground running' with the scientifically interesting core of the work. In this foundational project, our key goals are the development of a methodological framework for testing the reproducibility of human evaluations in NLP, and of a multi-lab paradigm for carrying out such tests in practice, carrying out the first study of this kind in NLP. We will (i) systematically diagnose the extent of the human evaluation reproducibility problem in NLP and survey related current work to address it (WP1); (ii) develop the theoretical and methodological underpinnings for reproducibility testing in NLP (WP2); (iii) test the suitability of the shared-task paradigm (uniformly popular across NLP fields) for reproducibility testing (WP3); (iv) create a design for multi-test reproducibility studies, and run the ReproHum study, an international large-scale multi-lab effort conducting 50+ individual, coordinated reproduction attempts on human evaluations in NLP from the past 10 years (WP4); and (v) nurture and build international consensus regarding how to address the reproducibility crisis, via technical meetings and growing our international network of researchers (WP5).

The unique research capability of the Global Hawk, with ultra-long flights possible in the upper troposphere and lower stratosphere, provides a major new opportunity to advance atmospheric science. In response to the NERC/STFC/NASA collaborative initiative, we have assembled an experienced UK team that proposes to execute a research programme covering fundamental science and technology development, which, by working with the Global Hawk, will radically enhance our future research capabilities. The Tropical Tropopause Layer (TTL) is a crucial region for chemistry/climate interactions. Building on work we have already done in this area , we will collaborate with NASA's ATTREX programme to study the TTL over the Pacific Ocean and South East Asia, with new measurements and analysis. We will address fundamental questions related to atmospheric composition, radiation and transport. The TTL controls the transport of water vapour, the crucial radiative gas, into the stratosphere; we will advance understanding of the role of sub-visible cirrus in water vapour processes. The TTL is also the main route by which very short-lived halogen species, which represent a large uncertainty in future stratospheric ozone evolution, enter the stratosphere. We will improve knowledge of the budgets of these gases and of their chemical transformation and transport through the TTL, including the role of convective transport into the TTL and the subsequent routes for transport from the TTL to the lower stratosphere. Improving representation of these processes in global chemistry/climate models is a key aim. In order to study these processes, The FAAM BAe-146 will be deployed in Guam in Jan/Feb 2014. It will fly coordinated flights with the Global Hawk which will make measurements in the same period in the TTL over the West Pacific. Detailed involvement in all phases of the collaborative missions with ATTREX will enhance the UK potential for future research using the Global Hawk, including advanced capability in mission planning and methodologies for complex, real-time data analysis. The aircraft measurements will be interpreted in conjunction with ground-based and balloon-based measurements of very short-lived halogen species and ozone, using a complementary group of regional high resolution models, global composition models and a global cirrus model. We will develop and test two new instruments and new software for the payload/mission-scientist interface, which are ideally suited for the capabilities of the Global Hawk. One new instrument will allow quantification in the TTL of the important physical properties of sub- and super-micron sized particles, allowing new information about clouds and radiation. We will develop a new short-wave IR spectrometer to measure greenhouse (CO2, CH4, and H2O) and other (CO) gases in the lower atmosphere by remote sensing, taking advantage of the very long flights in the upper troposphere and lower stratosphere. Both instruments will be flight-tested in CAST. As well as addressing the specifics of this call, CAST addresses the central vision of the Technology theme: "to engage scientists, technologists, computer specialists and engineers working both within the NERC community and outside it, identifying that in many cases it will only be through developing new partnerships that the most challenging innovations in technology can be enabled" (http://www.nerc.ac.uk/research/themes/tap/documents/tap-technologies-2009.pdf). CAST brings new technology expertise in machine learning into the NERC community and strengthens the links between NERC scientists and the technology groups at Hertfordshire and the Astronomy Technology Centre.

The oceans cover ~70% of the Earth's surface. The lowest part of the atmosphere over the oceans, the marine boundary layer (MBL), is subject to fluxes of sea spray aerosol and gases from the ocean and is linked to the free troposphere (FT) by vertical mixing in convective events but also by large scale mixing events such as frontal passages or tropical easterly waves. Most greenhouse gases (such as carbon dioxide, CO2, nitrous oxide, N2O) have atmospheric lifetimes of hundreds or thousands of years but others, notably methane, CH4, and tropospheric ozone, O3, have much shorter lifetimes (~9 years and weeks, respectively), largely because they have chemical sinks in the troposphere. Together they account for about 30% of the global radiative forcing of all greenhouse gases. Under most conditions, the MBL acts as a sink for O3 due to the low concentrations of NOx; furthermore about 25% of the tropospheric CH4 destruction occurs in the tropical MBL and a further 35% in the tropical marine free troposphere, hence the atmosphere above the (tropical) oceans is a very important region for atmospheric chemistry. The atmospheric oxidation capacity ("self-cleansing" capacity) is to a large extent determined by the hydroxyl radical (OH), O3 and their budgets and cycling; globally most tropospheric OH is found in the tropics. Therefore a quantitative understanding of the composition and chemistry of the marine atmosphere is crucial to examine the atmospheric oxidative capacity and climate forcing. This project will use a regional three-dimensional model (WRF-Chem) to study meteorological and chemical processes in the marine atmosphere. The model results will be compared to data from recent field campaigns in the East Pacific (TORERO, EqPOS) and from the North Atlantic (Cape Verde Atmospheric Observatory and Bermuda). By comparing model results with field data we will be able to see if the processes, sources and chemical reactions that are included in the model are sufficient to explain the data or if modifications and improvements to the reaction mechanism, emissions inventories or details of physical parameterisations will have to be made. Once these improvements have been made and the model is capable of reproducing the data, we will then be able to quantify lifetimes and budgets of important compounds such as ozone and the toxic mercury and to transfer our results to other ocean regions and to inform global models including Earth System models. This project aims to quantitatively describe the underlying processes and not to simply optimise the fit to observational data by unphysical adjustments in the model.