With the Kigali Amendment coming into force in 2019, the Montreal Protocol on Substances that Deplete the Ozone Layer has entered a major new phase in which the production and use of hydrofluorocarbons (HFCs) will be controlled in most major economies. This landmark achievement will enhance the Protocol's already-substantial benefits to climate, in addition to its success in protecting the ozone layer. However, recent scientific advances have shown that challenges lie ahead for the Montreal Protocol, due to the newly discovered production of ozone-depleting substances (ODS) thought to be phased-out, rapid growth of ozone-depleting compounds not controlled under the Protocol, and the potential for damaging impacts of halocarbon degradation products. This proposal tackles the most urgent scientific questions surrounding these challenges by combining state-of-the-art techniques in atmospheric measurements, laboratory experiments and advanced numerical modelling. We will: 1) significantly expand atmospheric measurement coverage to better understand the global distribution of halocarbon emissions and to identify previously unknown atmospheric trends, 2) combine industry models and atmospheric data to improve our understanding of the relationship between production (the quantity controlled under the Protocol), "banks" of halocarbons stored in buildings and products, and emissions to the atmosphere, 3) determine recent and likely future trends of unregulated, short-lived halocarbons, and implications for the timescale of recovery of the ozone layer, 4) explore the complex atmospheric chemistry of the newest generation of halocarbons and determine whether breakdown products have the potential to contribute to climate change or lead to unforeseen negative environmental consequences, 5) better quantify the influence of halocarbons on climate and refine the climate- and ozone-depletion-related metrics used to compare the effects of halocarbons in international agreements and in the design of possible mitigation strategies. This work will be carried out by a consortium of leaders in the field of halocarbon research, who have an extensive track record of contributing to Montreal Protocol bodies and the Intergovernmental Panel on Climate Change, ensuring lasting impact of the new developments that will be made.

The invention and spread of farming around the world was one of the most important events in human history, and it continues to shape our existence today. Understanding this process is one of the keys to understanding human civilization, yet despite decades of study, fundamental questions regarding why, where and how it occurred, and what were its early consequences for humankind remain unanswered. The bones of early domestic animals and their wild ancestors are commonly found at archaeological sites and they hold important clues to many of these questions. New scientific techniques including the use of genetics and statistical analyses of the shapes of these ancient bones are beginning to provide unique insights into the biology of the domestication process itself, as well as new ways of tracking its spread as farmers moved into new areas. One of the most momentous journeys made by early farmers was firstly from mainland East Asia into Island Southeast Asia, and then into the Pacific. This movement is traditionally thought to have begun by a linguistically related group known as the Austronesians. Evidence from studies of languages, pottery, and human gut bacteria suggest that farmers in Taiwan began heading south, reaching the Philippines before continuing on towards the island of New Guinea. From there, a culturally distinct group known as Lapita headed east into the Pacific. These were the ancestors of the Polynesians who went onto colonize the most remote islands on Earth. When farmers migrate, they take with them not just their agricultural tools and their plants, but also their domestic animals as well. When we investigated the genetic signatures of archaeological pigs throughout Island Southeast Asia, we expected the evidence to show that the route pigs took to reach the Pacific mirrored that of the humans. After all, pigs could not have swum across the open ocean to reach the islands of West Polynesia. What we found, however, strongly suggested that the pigs associated with the Lapita expansion did not come from Taiwan, as the people seem to have, but originated instead in Vietnam, then travelling along the islands of Sumatra and Java before reaching New Guinea. The assumption at the heart of the Out-of-Taiwan model holds that all of the individual elements of the farming package first originated in Taiwan, and that each of the elements should tell the same story. The contradiction between the pig data and the human evidence implies that the story of the Pacific colonization was a great deal more complex than previously imagined. By adding to and extending our previous work on pigs to include dogs and chickens, we plan to unravel these complexities. We will start by examining archaeological remains from sites across the region from two different perspectives. By employing newly developed techniques to quantify shape changes (called geometric morphometrics), we will be able to identify diagnostic signatures that will enable us to pinpoint the origins of the ancestors of the examined sample. In addition, we will extract DNA from the archaeological material and compare the genetic sequences with a global database. The combination of these techniques will also us not only to acquire two different kinds of data from the same specimen, but also to compare the evidence from each and trace the signatures through time space. We will also collect and analyze modern pig, dog, and chicken samples from throughout the region to ascertain their genetic diversity. This element of the study will enable us to ask questions about the relationships between modern and ancient specimens, and the degree of hybridization between different waves of incoming domestic animals. Overall we aim to reconstruct a detailed map of the migration of early farmers into the Pacific, allowing us to obtain answers to a series of longstanding questions, and insights into the origins of agriculture, human migration, and civilization.

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.

Economies in South East Asia are developing rapidly leading to rapidly growing emissions of a variety of important chemicals including halocarbon compounds that can impact the ozone layer and nutrients and contaminants that can alter ocean biological processes. These emissions are carried towards the Pacific Ocean mixing with dust from the Asian deserts. The subsequent deposition of this material can impact on ocean productivity and the transport of ozone damaging chemicals southwards allows them to enter the equatorial region with rapid transfer to the stratosphere with attendant threats to stratospheric ozone. A recently developed Taiwanese sampling station offers an ideal location to study this Asian outflow as it starts its journey and hence to better understand its current and potential future impacts in the region and globally. This grant aims to develop links between a leading UK research group and colleagues in Taiwan in preparation for a major grant application for fields studies in this region.

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