This proposal will develop new methodology for summarising the spatial information obtained from analysing multiple time series of spatial trajectories. The project will involve adapting recent methodology by the applicants for the analysis of single time series trajectories, to develop the coherent analysis of multiple trajectories observed in a given spatial region. From these advances, summaries of regional spatial structure will be proposed, as well as methods for assessing the uncertainty inherent to such summaries. In particular, as a testbed, such will be implemented for regional sets of oceanographic observations from the Global Drifter Program, which contributes to providing deeper understanding of ocean circulation and its impact on climate change. The main scope of this proposal is therefore to test the feasibility of aggregate statistical analysis of the spatial information contained in multiple sets of trajectory observations. It is an ambitious research project which, if successful, would open the door to a wide set of applications such as ecology, oceanography and traffic management.

Imagine a severe weather event occurs, causing devastating impacts to a particular region. One question that is repeatedly asked to climate scientists by politicians, disaster responders, recovery planners and journalists is about the role of climate change in causing or affecting the event. The direct cause of the devastation is the unusual weather but, in many cases, climate change will have made the event more likely, more severe, or potentially both. In those cases, the devastation may be partly or even mostly due to the change in climate. In some cases, the worst consequences may be due to the vulnerability of those living in the region, or a combination of many different factors which will reflect past and current decisions on a variety of levels. Understanding whether climate change has made the event more damaging is important. Wealthier nations have caused the world to warm, but poorer nations have experienced some of the most damaging consequences. International climate negotiations are discussing the issue of 'loss and damage' - whether and how those mainly responsible for climate change should compensate those who experience the worst consequences. This project will aid those discussions by providing answers to key questions about how the consequences of extreme weather events have already changed and how those consequences may change further in future, and by placing those events within their specific contexts of vulnerability. We will develop a new methodology to answer questions about the severity of extreme weather events - how have the consequences of a particular weather situation been made worse by climate change? If the same weather situation had occurred in the climate that we had 100years ago, would it have been less damaging? What about if the weather situation happens again in the future? These are well-defined questions, but we cannot easily answer them yet. As an example, we might expect that more rain would fall today in a severe storm than if the same storm had occurred 100 years ago, potentially making the consequences worse. But, how much more rain? And, beyond the direct meteorological consequences, what about the effects on river flows and people? We will also use these same concepts in reverse by applying them to extreme events that occurred several decades ago to examine how their consequences would be different today in a warmer world. This project will consider many different types of extreme weather event, including heavy rainfall, windstorms, heatwaves and droughts, and examine the consequences of those weather events for society, including damage to property and flooding. Importantly, we will identify the additional impacts of a particular weather event which are due to living in a warmer world, directly addressing the critical issue of losses and damages caused by climate change. We will also build narratives of plausible worst-case events to inform decision making on adapting to our warming world.

The Atlantic Meridional Overturning Circulation (AMOC) is a system of ocean currents that circulate water around the Atlantic Ocean. It is a vital part of the Earth's climate system, playing a significant role in regulating global climate and weather patterns. We need to Continuously observe the AMOC for several reasons: 1. Understanding Climate Change: Continuous observations of the AMOC help scientists better understand how climate change affects the ocean's circulation and heat transport. By continuously monitoring the AMOC, researchers can identify changes in its intensity, speed, and location, which can help them make more accurate predictions about future changes in the climate. 2. Improving Climate Models: Continuous observations of the AMOC help improve climate models by providing data to validate and refine model predictions. This information can help scientists make more accurate projections about the effects of climate change on various aspects of the Earth's ecosystem, such as sea levels, ocean acidity, and weather patterns. 3. Detecting Abrupt Changes: Abrupt changes in the AMOC could have significant impacts on the Earth's climate and weather patterns. Continuous monitoring of the AMOC can help scientists detect such changes early, allowing for timely intervention and mitigation strategies to be put in place. 4. Understanding Ecosystems: The AMOC plays a critical role in regulating oceanic ecosystems, and continuous observations can help researchers better understand how changes in the AMOC affect marine life, such as plankton, fish, and other organisms. 5. Predicting Extreme Weather Events: The AMOC has a significant impact on weather patterns, and continuous monitoring can help researchers make more accurate predictions about extreme weather events, such as hurricanes, floods, and droughts. Overall, continuous observations of the AMOC are essential for understanding the Earth's climate system and its impact on various aspects of our planet, including the environment, ecosystems, and human societies. By continuously observing the AMOC, we can improve our understanding of the Earth's climate system, and better predict and prepare for the effects of climate change. The AMOC has been observed at 26N between Florida and Africa since 2004. This is heavily reliant on tall moorings in the water and research ships to collect the data and replace the moorings. In this programme, we will exploit new technologies to design a fit-for-purpose sustainable AMOC observing system at substantially lower cost than at present and deliver data back via satellite. This will allow us to deploy an optimised lower-cost 26N AMOC observing system from 2027.

The chemistry of the troposphere (lowest ~12 km of the atmosphere) plays a critical role in climate change, air quality degradation and biogeochemical cycling. Our understanding of the complexity of tropospheric chemistry has developed immensely over the last decades. One of the more recent developments is halogen (Cl, Br, I) chemistry. Halogen atom processes can fundamentally challenge current perspectives of tropospheric (and stratospheric) chemistry, and the uncertainty in the science generates impacts on air pollution and climate predictions. Restricted observational constraints, coupled to a lack of suitable modelling tools, translate into large uncertainties in (the few) calculations of the impact of halogens on regional or global scales, and their role in modifying the response of the Earth system to anthropogenic perturbations. Together with collaborators, we have shown that reactive halogens play a significant and pervasive role in determining the composition of the troposphere. Of the halogens, iodine has the most profound impact on tropospheric ozone (O3) cycling, and significantly modifies the atmospheric response to anthropogenic perturbations. We identified that the reaction between O3 and iodide (I-) at the ocean surface drives the majority of atmospheric iodine emissions and showed that this process has resulted in a tripling of atmospheric iodine in some regions over the latter half of the 20th century due to increased anthropogenic O3, meaning that iodine-driven O3 loss is more active now than in the past. However, simulations of the impacts of halogens through the 21st century have so far made no account of any potential changes in surface ocean I-, due to a lack of mechanistic understanding. Our team have constructed the first model of marine iodine cycling and find that the surface iodide distribution is impacted primarily by biological productivity, nitrification rates, mixed layer depth and advection. Indeed, under the scenario where nitrification rates are reduced by up to 44% in the next 20 - 30 years due to ocean acidification, the model predicts a doubling of surface [I-] in some regions (due to decreased bacterial I- oxidation).This result indicates a new coupling between climate-induced oceanographic changes and atmospheric air quality and climate, and suggests the need for an integrated approach to fully understand the impacts of iodine. Translating knowledge of [I-] into predictions of sea-air iodine emissions and their resulting impacts on the atmosphere is also highly uncertain due to a lack of measurements at environmentally representative concentrations and complex additional dependencies of iodine fluxes, over and above on [O3] and [I-], on water-side turbulent mixing and on surfactants/organic material. I-SEA is a multidisciplinary collaboration between atmospheric and marine scientists and geochemists from leading Earth System science institutes. We propose to bring new technology and ideas to address major uncertainties in the biogeochemical cycling of iodine in order to address our key hypothesis, that global change will drive significant changes in atmospheric iodine emissions over the coming century which will impact on air quality and climate. Ultimately the project will provide transformative new knowledge of the feedbacks between environmental change and the impact of reactive halogens on air quality, ecosystems and climate change.

We are all aware of how carbon emissions are leading to concern about a warming of the planet. In our view, the climate response to carbon emissions can be divided into the following stages: 1. Past and on going increases in atmospheric CO2 are leading to a global warming of up to 0.6C over the last 50 years. The regional variability is though much larger than this global signal. 2. Continuing emissions are increasing atmospheric CO2 and driving a heat flux into the ocean, leading to ocean warming. The amount of warming is sensitive to the carbon emission scenario, as well as the rate of carbon uptake by the ocean and terrestrial system. 3. The regional distribution of warming and carbon drawdown is sensitive to how the ocean interior takes up heat and carbon, involving the transfer of surface properties into the thermocline and deep ocean. 4. In the future, after emissions cease may be after many hundreds of years, the atmosphere and ocean will approach an equilibrium with each other. At this point, the final atmospheric CO2 and the amount of climate warming is simply related to cumulative sum of all the previously carbon emitted. One of the key findings of the latest IPCC report is how climate model projections suggest that global warming varies nearly linearly with cumulative carbon emissions. This response is not fully explained or understood, in terms of the essential underlying mechanisms or why different climate models reveal a different amount of warming to each other. We have established a new theory to explain how surface warming varies in time with carbon emissions. The aim of the proposal is to investigate the climate warming in the following manner: (i) apply our new theory of how surface warming compares to cumulative carbon emissions, modified from an equilibrium response by the transient uptake of heat and carbon by the ocean and terrestrial systems; (ii) conduct diagnostics of how the ocean is taking up heat, examining how the ocean is ventilated in terms of volumetric changes in ocean density classes; (iii) develop ocean ventilation experiments with a range of ocean and climate models on timescales of decades to a thousand years, designed to explore the extent that the ocean uptake of heat and carbon are similar to each other, and assess their partly compensating effects on how surface warming links to carbon emissions; (iv) compare with and analyse diagnostics of state of the art climate models, integrated for a century, including climate models driven by emissions, terrestrial uptake of heat and carbon, and radiative forcing from non-CO2 greenhouse gases and aerosols. Our new theoretical framework has the potential to provide (i) improved understanding of the mechanisms controlling the relationship between surface warming and carbon emissions, particularly focusing on the role of the ocean; (ii) traceability between different ocean and climate models, identifying clearly which factors are leading to different climate responses; (iii) reconcile Earth System model investigations over a wider parameter regime with IPCC class climate models. This study is relevant for policy makers interested in different energy policies, and a link to end users is provided via the collaboration with the Hadley Centre and NOAA GFDL. The study emphases the importance of engaging with the wider public by developing 4 targeted short and accessible videos on the climate problem, emphasising our new viewpoint.