Date: 30th September 2025, Tuesday (11:00am – 12:00pm)
Presenter: Zeyuan Hu (NVIDIA)
Topic: Toward Stable and Skillful Hybrid Climate Simulations with Machine-Learning-based Subgrid Parameterizations

Abstract:
Modern climate projections often suffer from inadequate spatial and temporal resolution due to computational limitations, resulting in inaccurate representations of sub-grid processes. The Multiscale Modeling Framework (MMF, also known as super-parameterization) addresses this by embedding a kilometer-resolution cloud-resolving model within each atmospheric column of a host climate model, replacing traditional convection and cloud parameterizations. Machine learning (ML) offers a unique opportunity to make MMF more accessible by emulating the embedded cloud-resolving model and reducing its substantial computational cost. In this talk, we first introduce ClimSim-Online, a large-scale dataset and framework designed for developing hybrid physics-ML climate simulations. Building on the existing ClimSim dataset, ClimSim-Online provides a containerized, reproducible workflow enabling ML researchers to design, train, and evaluate hybrid climate models. We then present a stable hybrid model capable of integrating for at least 5 years with near operational-level complexity, including coarse-grid geography, seasonality, explicit cloud condensate and wind predictions, and land coupling. Our model demonstrates skillful online performance, achieving a 5-year zonal mean tropospheric temperature bias within 2K, water vapor bias within 1 g/kg, and a precipitation RMSE of 0.96 mm/day. Key factors contributing to our model’s performance include an expressive U-Net architecture and physical thermodynamic constraints for microphysics. These constraints help mitigate unrealistic cloud formation, enabling realistic multi-year cloud condensate climatology. Lastly, we share insights from the LEAP–ClimSim Kaggle competition, in which participants applied novel ML techniques to fit the ClimSim dataset. We evaluate the top solutions in terms of their impact on online hybrid simulations and discuss key lessons learned. Despite advances in architectures and physical constraints, our online diagnostics reveal persistent biases in certain regions, highlighting the need for innovative strategies to further optimize online performance.

Speaker Profile:
Dr Zeyuan Hu is a research scientist at the AI for weather/climate team at NVIDIA Research. He obtained his PhD in atmospheric science from Harvard University, where he worked on cloud-resolving atmospheric simulations and AI for climate studies.

Date: 7th October 2025, Tuesday (11:00am – 12:00pm)
Presenter: Kashyapa Athreyas (CCRS)
Topic: Satellites, earth observation and weather

Abstract:
Weather affects all being on earth in their daily life. We try to predict weather to safeguard our life, interests and activities. We need to observe in order to gather enough information based on which, we predict the weather. In the recent decades, the importance of global coupling in the atmosphere is recognised not only internally, but also with ocean, surface and solar events. Satellites provide a good platform to observe global events on a regular basis. In this talk, I will go though the basics of earth observation from satellites, few of the instruments relevant to weather research that I have worked with. Thereafter, I will discuss some of the atmospheric studies I have been involved in such as, 1) inter-hemispheric coupling during the sudden stratospheric warming events, 2) gravity waves characterisation generated from thunderstorms in SEA region, and 3) estimation of latent heat of thunderstorms using satellite data.

Speaker Profile:
Kashyapa Athreyas is a Research Scientist at CCRS. He completed his Bachelor’s degree in Aerospace Engineering in 2011 at the University of Liverpool, UK, followed by a two-year joint European Master’s degree in Space Technology with a specialization in Systems and Control at Luleå University of Technology, Sweden, and Czech Technical University, Prague. He earned his PhD in 2018 from Nanyang Technological University (NTU), Singapore. Before joining CCRS in September 2025, he worked at NTU’s Satellite Research Centre, where he served as lead mission and systems engineer for four satellites, including two Earth observation missions, and contributed to several middle atmospheric coupling projects. His research interests include data assimilation, satellite remote sensing, atmospheric coupling, and machine learning–driven modelling.

Date: 14th October 2025, Tuesday (11:00am – 12:00pm)
Presenter: Trina Ng (CCRS)
Topic: What do we really know about sea-level rise in Singapore and Southeast Asia?

Abstract:
Global mean sea level (GMSL) has risen by over 20 cm since 1900, with the rate of rise accelerating in recent decades. While the contributions from thermal expansion and glacier melt are well understood, major uncertainties in the Antarctic ice sheet remain that drive the projected range of future GMSL widely. These gaps are critical for Southeast Asia, where dense population and economies are highly exposed. Singapore, in particular, has identified sea-level riser as an existential threat. In this talk, I will present local and regional projections of relative sea-level (RSL) rise for Singapore and Southeast Asia, highlighting both confident components of RSL rise and major gaps in our knowledge. The roles of regional ocean dynamics, ice sheet processes and vertical land motion in shaping future sea level in this region will be examined.

Speaker Profile:
Ms Trina Ng is a Research Scientist in the Department of Climate Research at Centre for Climate Research Singapore. She has a Masters of Science in Geophysics from Imperial College London, and has recently submitted her PhD thesis at Nanyang Technological University and awaiting defense. Her research focuses on understanding the drivers of relative sea-level change in Singapore and Southeast Asia, with a particular emphasis on how ocal and regional processes influence future projections. At CCRS, she leads the development of national sea-level projections that are directly relevant to national adaptation strategies, bridging scientific research with policy applications.

Date: 21st October 2025, Tuesday (11:00am – 12:00pm)
Presenter: Emma Ramsay (NTU)
Topic: Cooling Singapore and beyond

Abstract:
Urban overheating is one of the most pressing challenges facing tropical cities, with significant implications for health, equity, ecosystems, and overall livability. The Cooling Singapore 2.0 project is an integrated, multi-disciplinary project untangling the complexities of heat risks in Singapore at the intersection of science and policy. This talk will share insights from the Cooling Singapore 2.0 project and explore how these findings can inform action beyond Singapore’s borders. Key themes include the use of accessible and low-cost technologies to understand heat risks at local scales; approaches for monitoring and evaluating adaptation strategies; the role of nature-based solutions in cooling and resilience; and the importance of community engagement and cross-sector collaboration.

Speaker Profile:
Dr Emma Ramsay is a Lee Kuan Yew Postdoctoral Fellow at Nanyang Technological University, Singapore. Her research focuses on urban heat stress and climate adaptation. Working closely with decision-makers and local communities, she leads several collaborative research projects which aim to enhance climate resilience in Southeast Asian cities. She is a Lead Author on the Intergovernmental Panel on Climate Change (IPCC) Special Report on Climate Change and Cities. Prior to joining NTU, Emma earned her PhD at Monash University, Australia where she investigated climate-health challenges in urban informal settlements.

Date: 28th October 2025, Tuesday (11:00am – 12:00pm)
Presenter: Linda Yanti Sulistiawati (NUS)
Topic: Introduction to Climate Change Law

Abstract:
From Kyoto to Paris, climate change law has been discussed and contested. The talk will give a general understanding of climate change law including its actors, organizations, and stakeholders. It will provide an introduction to climate change in international environmental law, introduction to stakeholders in climate change law, key cases in climate change, and an introduction to developments in international law.

Speaker Profile:
Linda is a Senior Research Fellow at APCEL and also an Associate Professor of Law in Universitas Gadjah Mada, Indonesia. She received her doctorate in 2013 (honorary mentioned) from University of Washington School of Law, supported by the Fulbright PhD Presidential Program. She focuses on international environmental law issues, such as climate change, REDD+, marine plastic pollution, land issues and customary (adat) issues. Linda was a member of the delegation leading Indonesia’s negotiations of the Paris Agreement on Climate Change. Linda is a lead author of the Intergovernmental Panel on Climate Change’s Sixth Assessment Report and the Special Report on Cities and Climate Change. At APCEL, Linda focuses on comparative climate change law and policy in ASEAN.