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A new report highlights the extent that housing developers fail to deliver on their ecological commitments. Kiera Chapman, Postdoctoral Research Fellow, Faculty of English, University of Oxford Malcolm Tait, Professor of Planning, School of Geography, University of Sheffield Licensed as Creative Commons – attribution, no derivatives.

An alkaline world: a new assessment of the global chemical climate for PM2.5 formation and nitrogen and sulphur deposition

The reduction of atmospheric reactive nitrogen (Nr) and sulfur (Sr) species is a key objective for air quality control policies as they contribute to the formation of PM2 .5, which has significant effects on human health and climate, and their deposition affects ecosystem productivity. The chemical climate for Nr and Sr pollution has undergone dramatic changes in the past two decades. Therefore, it is necessary to update our understanding of global Nr and Sr chemistry and investigate their mitigation under current atmospheric conditions. Since a range of emission sources and atmospheric chemical and physical processes contribute to Nr and Sr concentrations, atmospheric chemistry transport models (ACTMs) are essential tools to identify the key processes controlling their impacts and effective mitigation. In this talk, I will present my research on global modelling of Nr and Sr species using the EMEP MSC -W ACTM coupled with WRF meteorology. Firstly, I will introduce the model-measurement comparisons of reduced nitrogen (RDN), oxidized nitrogen (OXN), and oxidized sulfur (OXS) species covering 10 monitoring networks worldwide that measure surface concentrations and wet deposition. Secondly, I will summarize our global analysis of current Nr and Sr gas-aerosol partitioning and regional budgets. This analysis quantitatively demonstrates that successful control of SO2  and NOx emissions has resulted in atmospheric NH3  excess in many areas, leading to a new significance of alkaline air, with adverse impacts on ecosystems. Finally, I will present our work that quantifies the sensitivities of emissions reductions for mitigating PM2 .5 and N and S deposition. This work highlights a global picture of the effectiveness of NH3 , NOx, and SOx emissions reductions for mitigating both concentrations and deposition of Nr and Sr pollutants.

• Speaker: Dr Yao Ge, Yusuf Hamied Department of Chemistry, University of Cambridge
• Tuesday 18 March 2025, 11:00-12:00
• Venue: Chemistry Dept, Unilever Lecture Theatre and Zoom.
• Series: Centre for Atmospheric Science seminars, Chemistry Dept.; organiser: Dr Megan Brown.

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Climate policy: why is it needed and how to make it work

Abstract not available

• Speaker: Sanna Markkanen (CISL)
• Monday 27 January 2025, 13:00-14:00
• Venue: MR3, CMS.
• Series: Quantitative Climate and Environmental Science Seminars; organiser: Bethan Wynne-Cattanach.

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Could stratospheric aerosol injection produce meaningful global cooling without novel aircraft?

Stratospheric aerosol injection (SAI) is a proposed method of cooling the planet and reducing the impacts of climate change by adding a layer of small particles to the high atmosphere where they would reflect a fraction of incoming sunlight. While it is likely that SAI could reduce global temperature, it has many serious risks and would not perfectly offset climate change. For SAI to be effective, injection would need to take place in the stratosphere. The height of the transition to the stratosphere decreases with latitude, from around 17km near the equator to 8km near the poles. The required injection height would therefore also decrease for higher latitude injection. In this talk, I will present simulations of SAI in an earth system model, UKESM , which quantify how impacts would vary with the injection location and timing, focusing on low-altitude high-latitude injection strategies. Our results suggest that SAI could meaningfully cool the planet even if limited to using existing large jets and injecting at around 13km altitude, if this injection is in the high latitudes during spring and summer. However, relative to a more optimal deployment with novel aircraft at 20km, this strategy requires three times more sulphur dioxide injection and so would strongly increase some side-effects.

• Speaker: Alistair Duffey, PhD Student at University College London, Earth Sciences
• Tuesday 04 February 2025, 11:00-12:00
• Venue: Chemistry Dept, Unilever Lecture Theatre and Zoom.
• Series: Centre for Atmospheric Science seminars, Chemistry Dept.; organiser: Yao Ge.

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Madagascar tops the list globally in terms of the percentage of plant species endemic to a single island. Julian Schrader, Lecturer in Plant Ecology, Macquarie University Licensed as Creative Commons – attribution, no derivatives.