Ignacio Lopez-Gomez
Ignacio Lopez-Gomez is a research scientist at Google Research. His research focuses on the development of AI-based weather and climate models, with an emphasis on extreme events and environmental risks. He holds a PhD in Environmental Science & Engineering from Caltech, where he developed a model of atmospheric turbulence, convection and clouds for climate models.
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Regional climate risk assessment from climate models using probabilistic machine learning
Rob Carver
Tapio Schneider
John Anderson
Fei Sha
Nature Machine Intelligence (2026)
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Accurate, actionable climate information at kilometer scales is crucial for robust natural hazard risk assessment and infrastructure planning. Simulating the impact of climate at these resolutions remains intractable, forcing reliance on downscaling, either physics-based or statistical methods which transform climate simulations from coarse to impact-relevant resolutions. It is essential to comprehensively capture the interdependency among climate processes of interest. However, current approaches, either lack the desired scalability or are bespoke to specific types of hazards. We introduce GenFocal, a step change in paradigm. GenFocal is a computationally efficient, general-purpose, end-to-end probabilistic, generative framework that gives rise to full probabilistic characterizations of complex climate processes interacting at fine spatiotemporal scales. When employed to assess risk in the present climate, GenFocal more faithfully projects the risk of extremes than state-of-the-art approaches including one recommended by the US Fifth National Climate Assessment. GenFocal produces plausible tracks of tropical cyclones, providing accurate statistics of their genesis and evolution, even when they are absent from the corresponding climate simulations. GenFocal also shows compelling results that are consistent with the literature on projecting climate impact in an extended time frame (five decades to one century). In short, GenFocal transforms the numerical computation into statistical knowledge bases that can be efficiently queried, thus opening up new possibilities of assessing the impacts of future climates at the spatio-temporal scales relevant to local and regional communities. We believe this work, as a starting point, establishes generative AI technology as an effective and potent paradigm for modeling complex, high-dimensional multivariate statistical correlations that have deterred precise quantification of climate risks associated with hazards such as wildfires, extreme heat, tropical cyclones, and flooding; thereby enabling the evaluation of adaptation strategies for affected populations and the built environment.
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A probabilistic framework for learning non‐intrusive corrections to long‐time climate simulations from short‐time training data
Benedikt Barthel
Rob Carver
Fei Sha
Themistoklis Sapsis
Journal of Advances in Modeling Earth Systems (2026)
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Despite advances in high performance computing, accurate numerical simulations of global atmospheric dynamics remain a challenge. The resolution required to fully resolve the vast range scales as well as the strong coupling with—often not fully-understood—physics renders such simulations computationally infeasible over time horizons relevant for long-term climate risk assessment. While data-driven parameterizations have shown some promise of alleviating these obstacles, the scarcity of high-quality training data and their lack of long-term stability typically hinders their ability to capture the risk of rare extreme events. In this work we present a general strategy for training variational (probabilistic) neural network models to non-intrusively correct under-resolved long-time simulations of turbulent climate systems. The approach is based on the paradigm introduced by Barthel Sorensen et al. (2024, https://doi.org/10.1029/2023ms004122) which involves training a post-processing correction operator on under-resolved simulations nudged toward a high-fidelity reference. Our variational framework enables us to learn the dynamics of the underlying system from very little training data and thus drastically improve the extrapolation capabilities of the previous deterministic state-of-the art—even when the statistics of that training data are far from converged. We investigate and compare three recently introduced variational network architectures and illustrate the benefits of our approach on an anisotropic quasi-geostrophic flow. For this prototype model our approach is able to not only accurately capture global statistics, but also the anistropic regional variation and the statistics of multiple extreme event metrics—demonstrating significant improvement over previously introduced deterministic architectures.
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Dynamical-generative downscaling of climate model ensembles
Tapio Schneider
John Anderson
Fei Sha
Proceedings of the National Academy of Sciences, 122 (2025), e2420288122
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Regional high-resolution climate projections are crucial for many applications, such as agriculture, hydrology, and natural hazard risk assessment. Dynamical downscaling, the state-of-the-art method to produce localized future climate information, involves running a regional climate model (RCM) driven by an Earth System Model (ESM), but it is too computationally expensive to apply to large climate projection ensembles. We propose an approach combining dynamical downscaling with generative AI to reduce the cost and improve the uncertainty estimates of downscaled climate projections. In our framework, an RCM dynamically downscales ESM output to an intermediate resolution, followed by a generative diffusion model that further refines the resolution to the target scale. This approach leverages the generalizability of physics-based models and the sampling efficiency of diffusion models, enabling the downscaling of large multimodel ensembles. We evaluate our method against dynamically downscaled climate projections from the Coupled Model Intercomparison Project 6 (CMIP6) ensemble. Our results demonstrate its ability to provide more accurate uncertainty bounds on future regional climate than alternatives such as dynamical downscaling of smaller ensembles, or traditional empirical statistical downscaling methods. We also show that dynamical-generative downscaling results in significantly lower errors than popular statistical downscaling techniques, and captures more accurately the spectra, tail dependence, and multivariate correlations of meteorological fields. These characteristics make the dynamical-generative framework a flexible, accurate, and efficient way to downscale large ensembles of climate projections, currently out of reach for pure dynamical downscaling.
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Pushing the Frontiers in Climate Modeling and Analysis with Machine Learning
Veronika Eyring
William D. Collins
Pierre Gentine
Elizabeth A. Barnes
Marcelo Barriero
Tom Beucler
Marc Bocquet
Christopher S. Bretherton
Hannah M. Christiansen
Katherine Dagon
David John Gagne
David Hall
Dorit Hammerling
Stephan Hoyer
Fernando Iglesias-Suarez
Marie C. McGraw
Gerald A. Meehl
Maria J. Molina
Claire Monteleoni
Michael Pritchard
David Rolnick
Jakob Runge
Philip Stier
Oliver Watt-Meyer
Katja Weigel
Rose Yu
Laure Zanna
Nature Climate Change, 14 (2024), 916–928
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Climate and Earth system models are important tools to understand and project climate change. Due to their complexity, they are limited in their horizontal resolutions, and some processes remain uncertain. Machine Learning (ML) together with short km-scale simulations and Earth observations provide new opportunities to reduce long-standing systematic errors and to improve projection capability. In this Perspective, we argue that ML should be fully exploited to (a) develop hybrid ML/physics Earth system models with greater fidelity, (b) to improve detection, attribution, and forecasting of extremes, and (c) to advance climate model analysis and understanding of the Earth system. We further discuss how tackling key ML challenges such as generalization, physical constraints, uncertainty quantification, explainable artificial intelligence, causal inference, and benchmarks can help achieve these goals. This effort will require bringing together ML and climate scientists, while also leveraging the private sector, to accelerate progress towards desperately-needed actionable climate science.
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SEEDS: Emulation of Weather Forecast Ensembles with Diffusion Models
Robert Carver
Fei Sha
John Anderson
Science Advances, 10 (2024), eadk4489
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Probabilistic forecasting is crucial to decision-making under uncertainty about future weather. The dominant approach is to use an ensemble of forecasts to represent and quantify uncertainty in operational numerical weather prediction. However, generating ensembles is computationally costly. In this paper, we propose to generate ensemble forecasts at scale by leveraging recent advances in generative artificial intelligence. Our approach learns a data-driven probabilistic diffusion model from the 5-member ensemble GEFS reforecast dataset. The model can then be sampled efficiently to produce realistic weather forecasts, conditioned on a few members of the operational GEFS forecasting system. The generated ensembles have similar predictive skill as the full GEFS 31-member ensemble, evaluated against ERA5 reanalysis, and emulate well the statistics of large physics-based ensembles. We also apply the same methodology to developing a diffusion model for generative post-processing: the model directly learns to correct biases present in the emulated forecasting system by leveraging reanalysis data as labels during training. Ensembles from this generative post-processing model show greater reliability and accuracy, particularly in extreme event classification. In general, they are more reliable and forecast the probability of extreme weather more accurately than the GEFS operational ensemble. Our models achieve these results at less than 1/10th of the computational cost incurred by the operational GEFS system.
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Global extreme heat forecasting using neural weather models
Amy McGovern
Jason Hickey
Artificial Intelligence for the Earth Systems, 2 (2023), e220035
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Heatwaves are projected to increase in frequency and severity with global warming. Improved warning systems would help reduce the associated loss of lives, wildfires, power disruptions, and reduction in crop yields. In this work, we explore the potential for deep learning systems trained on historical data to forecast extreme heat on short, medium and subseasonal time scales. To this purpose, we train a set of neural weather models (NWMs) with convolutional architectures to forecast surface temperature anomalies globally, 1 to 28 days ahead, at ~200-km resolution and on the cubed sphere. The NWMs are trained using the ERA5 reanalysis product and a set of candidate loss functions, including the mean-square error and exponential losses targeting extremes. We find that training models to minimize custom losses tailored to emphasize extremes leads to significant skill improvements in the heatwave prediction task, relative to NWMs trained on the mean-square-error loss. This improvement is accomplished with almost no skill reduction in the general temperature prediction task, and it can be efficiently realized through transfer learning, by retraining NWMs with the custom losses for a few epochs. In addition, we find that the use of a symmetric exponential loss reduces the smoothing of NWM forecasts with lead time. Our best NWM is able to outperform persistence in a regressive sense for all lead times and temperature anomaly thresholds considered, and shows positive regressive skill relative to the ECMWF subseasonal-to-seasonal control forecast after 2 weeks.
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