About

Stephan A. Fueglistaler is a Professor of Geosciences at Princeton University. He serves as the Director of the Atmospheric and Oceanic Sciences (AOS) and the Cooperative Institute for Modeling the Earth System (CIMES). His research group focuses on Climate Science, with a particular emphasis on atmospheric dynamics and their implications for climate variability and change. As a faculty member in the Department of Geosciences, he contributes to advancing understanding in climate science through research and leadership roles. His work is recognized within the university community, and he is actively involved in mentoring graduate students and leading research initiatives related to climate and atmospheric sciences.

Research topics

• Atmospheric sciences
• Environmental science
• Meteorology
• Geology
• Climatology
• Physics
• Geography
• Ecology
• Biology
• Oceanography

Selected publications

• An Analytical Model for Spatially Varying Clear-Sky CO2 Forcing

  Journal of Climate · 51 citations

  Senior authorCorresponding
  • Atmospheric sciences
  • Climatology
  • Environmental science

  Clear-sky CO2 forcing is known to vary significantly over the globe, but the state dependence that controls this is not well understood. Here we extend the formalism of Wilson and Gea-Banacloche to obtain a quantitatively accurate analytical model for spatially varying instantaneous CO2 forcing, which depends only on surface temperature Ts, stratospheric temperature, and column relative humidity (RH). This model shows that CO2 forcing can be considered a swap of surface emission for stratospheric emission, and thus depends primarily on surface–stratosphere temperature contrast. The strong meridional gradient in CO2 forcing is thus largely due to the strong meridional gradient in Ts. In the tropics and midlatitudes, however, the presence of H2O modulates the forcing by replacing surface emission with RH-dependent atmospheric emission. This substantially reduces the forcing in the tropics, introduces forcing variations due to spatially varying RH, and sets an upper limit (with respect to Ts variations) on CO2 forcing that is reached in the present-day tropics. In addition, we extend our analytical model to the instantaneous tropopause forcing, and find that this forcing depends on Ts only, with no dependence on stratospheric temperature. We also analyze the τ = 1 approximation for the emission level and derive an exact formula for the emission level, which yields values closer to τ = 1/2 than to τ = 1.

  DOI

• Anomalous energy fluxes and feedback parameter over the course of ENSO events

  2026-02-21

  articleOpen accessSenior author

  Internal variability may provide constraints on the global temperature response to forcing. Previous work showed that ENSO induces atmospheric stratification anomalies that lead to tropical low cloud anomalies not correlated with mean temperature. Here, we expand this argument. We discuss the physical processes leading to a canonical evolution of the global feedback parameter over the course of an ENSO event, $\lambda_\mathrm{ENSO}(\tau)$, where $\tau$ is the ENSO phase, and $\lambda_\mathrm{ENSO}(\tau)$ differs from the feedback parameter observed in typical CO$_2$ forcing experiments. During the growth phase of El~Niño, the heat flux from the tropical Pacific into the atmosphere is amplified by a net gain at the top of the atmosphere (an apparent runaway state), and heat is primarily redistributed among tropical ocean basins. During the peak phase, the static stability anomaly rapidly decays, and only in the decay phase does the climate system lose heat to space.

  PublisherOA PDFDOI

• Has agricultural irrigation masked intense warming in the central United States?

  2026-03-13

  articleOpen accessCorresponding

  Since the 1980s, the central United States and southern-central Canada have experienced a notable lack of high temperature extremes, with many temperature record highs from the 1930s Dust Bowl period still standing. By contrast, atmospheric general circulation models (AGCMs) forced with observed sea surface temperatures consistently simulate exceptional warming over the central US during this period. What accounts for this discrepancy between observed and simulated temperature trends? We use ensembles of coupled and atmosphere-only climate model experiments to disentangle the influences of remote sea surface temperatures and local land-atmosphere interactions on historical temperature change in the central United States. Tropical Pacific teleconnections strongly impact central US temperatures: coupled general circulation models, which cannot reproduce observed trends in the tropical Pacific SST gradient, produce a moderate central US warming trend that is closer to observations than AGCMs prescribed with observed SSTs. Comparing seasonal latent and sensible heat fluxes in these experiments, we describe the central role of turbulent exchanges at the land surface on temperature trends. In a heavily irrigated area whose climate is known to be sensitive to changes in soil moisture, our results point to a possible role for agricultural irrigation in alleviating historical heat extremes, and in explaining the large difference between models and observations. We highlight the importance of understanding model-data discrepancies in tropical SST patterns and local land temperatures for predicting future climate extremes in the central US.

  PublisherDOI

• Surface Warming Patterns, Cloud Feedbacks, and Inter-basin Energy Redistribution During ENSO

  2026-03-13

  articleOpen accessSenior author

  Internal variability, particularly ENSO, plays a critical role in modulating global warming on interannual to decadal timescales. Its canonical surface temperature signature is well characterized, but the complex and non-linear relation between surface temperature and top-of-atmosphere (TOA) radiative response requires attention. Here, we use coupled atmosphere-ocean simulations to diagnose the energy redistribution and radiative feedbacks across ENSO phases. During the growth phase of El Niño, boundary-layer destabilization enhances ocean-atmosphere heat exchange in the tropical Pacific, while a positive net TOA flux anomaly amplifies surface warming, contrary to the canonical feedback perspective. This excess energy is transported poleward and zonally, with remote ocean basins exhibiting shallow heat uptake. At the El Niño peak, rapid atmospheric stabilization increases low-level cloudiness and shortwave reflection, while the subsequent decay phase is marked by net radiative cooling to space. In parallel, we find that high cloud fraction and upper-tropospheric humidity evolve in an anticorrelated manner across the tropics and extratropics. These changes are not directly tied to boundary-layer stability, and their opposing regional signatures largely cancel in the global mean. Notably, tropical drying and cloud loss co-occur with increased precipitation. Our findings clarify the role of ENSO in Earth's radiative variability and highlight key differences from CO2-forced warming.

  PublisherDOI

• No “Wet Gets Wetter” in Kilometer‐Scale Mock‐Walker Circulations

  AGU Advances · 2026-02-01

  articleOpen accessSenior author

  Abstract Many climate model simulations and limited observations indicate that regions of tropical ascent and precipitation contract in response to surface warming. This response has well‐studied implications for the width of the zonal‐ and annual‐mean Intertropical Convergence Zone, but its applicability to zonally asymmetric circulations such as the Pacific Walker circulation remains unknown. Here, we investigate the impact of warming on the area of large‐scale ascent in kilometer‐scale, mock‐Walker simulations with both fixed and interactive surface temperatures. Contrary to the “wet‐gets‐wetter” and “upped‐ante” paradigms of precipitation change, the simulations show a “wet‐gets‐drier” response to warming in which the ascent region becomes larger and, on average, drier. We attribute these changes to rapid circulation weakening, which limits the transport of moisture into the ascent region. To meet the growing moisture demand for precipitation, local evaporation within the ascent region must increase rapidly, and the ascent region expands to draw moisture from a larger surface area. We link the slowdown of the circulation to increases in gross moist stability driven by a previously unknown mechanism. Central to this mechanism are changes in the vertical structure of the circulation, which features two vertically stacked overturning cells reminiscent of some tropical convergence zones. These results challenge long‐held paradigms of tropical precipitation change and show that the vertical structure of tropical circulations can play a critical role in the hydrological response to warming.

  PublisherOA PDFDOI

• Understanding tropical cyclone frequency biases in a global storm resolving model

  2026-02-07

  article

  Global storm resolving models (GSRMs) provide an excellent testbed for understanding the role of small-scale processes in tropical cyclogenesis. In this study, we assess tropical cyclone (TC) genesis and frequency in the Geophysical Fluid Dynamics Laboratory’s eXperimental System for High‐resolution prediction on Earth‐to‐Local Domains version 2021 (X-SHiELD v2021). Compared to observations, X-SHiELD produces significantly fewer TCs, albeit with realistic representations of both the number of pre-TC disturbances (TC seeds) and the mean state relative to ERA5. We find that the TC seed-to-TC transition rate is underestimated in X-SHiELD because the spin-up of TC seed vortex is inefficient. The inefficient TC seed spin-up in X-SHiELD is associated with a weaker-than-observed low-level inflow, which is coupled to mesoscale ascent near the center that is too weak and too top-heavy. The biases in vertical velocity are associated with a dry bias at low levels, which is caused by the overly active shallow convection scheme. Our results underscore the importance of subgrid scale processes, particularly low level mixing through shallow convection, in the representation of TC genesis process even in kilometer scale models.

  PublisherDOI

• Assessing Earth's Energy Imbalance Trend in the Early 21st Century in Two High‐Resolution Coupled Models

  Geophysical Research Letters · 2026-04-30

  articleOpen accessSenior author

  Abstract Satellite observations since 2001 show an increasing Earth's energy imbalance (EEI) at the top of the atmosphere of 0.45 W m −2 dec −1 , a trend understated in coupled climate models. We assess the 2001–2024 EEI trend in historical simulations of two high‐resolution coupled models, CM4X, a revised version of CM4.0, and CESM‐HR, a high‐resolution version of CESM1, each with 10 realizations. The ensemble‐mean EEI trends in CM4X and CESM‐HR capture only 25% and 55% of the observed trend, respectively, due to underestimated shortwave trends in the tropics and Southern Hemisphere extratropics. CESM‐HR exhibits twice the intramodel variability in EEI and surface warming trends than CM4X, and biases in EEI trends are not linked to warming‐pattern differences. One CESM‐HR realization matches the observed EEI trend but via strong Antarctic offshore polynyas absent from observations. These results highlight the potentially critical influence of sea‐ice processes on near‐term climate projections in high‐resolution models.

  PublisherDOI

• Detecting changes in large-scale metrics of climate in short integrations of a global storm-resolving model of the atmosphere

  Environmental Research Climate · 2025-05-08

  articleOpen accessSenior author

  Abstract Recent advances have allowed for integration of global storm resolving models (GSRMs) to a timescale of several years. These short simulations are sufficient for studying aggregated statistics of short-timescale and small spatial-scale phenomena; however, it is questionable what we can learn from these integrations about the large-scale climate response to perturbations. To address this question, we use the response of X-SHiELD (a GSRM) to uniform sea surface temperature warming and CO 2 increase in two-year integrations and compare it to similar CMIP experiments. Specifically, we assess the statistical meaning of having two years in one model outside the spread of another model or model ensemble. This is of particular interest because X-SHiELD shows a distinct response of the global-mean precipitation to uniform warming and the northern hemisphere jet shift response to isolated CO 2 increase. To estimate the probability of X-SHiELD’s and the CMIP models having different means, we take the approach of Bayesian inference. We derive a posterior distribution for the differences in the mean between X-SHiELD and the CMIP models taking into account the X-SHiELD values for the global-mean precipitation response to uniform warming and the response of the norther hemisphere jet latitude to isolated CO 2 increase. We find that the most probable value for the difference between X-SHiELD and the CMIP mean is larger than one standard deviation, representing both internal variability and inter-model spread of the CMIP models. We also find that there is an important base-state dependence for some large-scale metrics that, when taken into account, can qualitatively change the interpretation of the results. We note that a year-to-year comparison is meaningful due to the use of prescribed sea-surface-temperature simulations.

  PublisherDOI

• Robust Projections of Changing Precipitation Evenness in a Warming Climate

  Geophysical Research Letters · 2025-04-30 · 3 citations

  articleOpen accessSenior author

  Abstract Global warming is expected to increase global mean precipitation by 2%–4%/K, but this increase may be uneven, leading to more flooding but also droughts. Utilizing the Gini index, a metric frequently used in economics, we analyze the evenness of precipitation distribution locally and globally from daily to annual‐mean timescale in CMIP6 global warming simulations. Spatial evenness of daily precipitation decreases over land and ocean, tropics and extratropics. Changes in temporal evenness of local‐daily precipitation show a complex geographic pattern. However, particularly over land, we show that a simple theoretical scaling explains this complexity to result from increased precipitation intensity scaling at about the Clausius‐Clapeyron rate, and a local balance between changes in annual‐mean precipitation and dry‐day fraction. These results provide a novel perspective on the relation between global constraints on the hydrological cycle to regional precipitation changes independent of changes in the geographic distribution of precipitation.

  PublisherDOI

• Detecting Changes in Large-Scale Metrics of Climate in Short Integrations of a Global Storm-Resolving Model of the Atmosphere

  2025-03-31

  preprintOpen accessSenior author
  PublisherOA PDFDOI

Recent grants

• Collaborative Research: Using SOCRATES Datasets to Improve Simulations of Clouds, Aerosols and their Climate Impacts

  NSF · $236k · 2017–2021

• Analysis of Cirrus Clouds and Atmospheric Humidity with Cloud Resolving Numerical Model Calculations

  NSF · $443k · 2014–2018

Frequent coauthors

• Thomas Peter

  ETH Zurich

  38 shared

• Yi Zhang

  Courant Institute of Mathematical Sciences

  31 shared

• B. P. Luo

  25 shared

• Isaac M. Held

  Princeton University

  19 shared

• Peter Haynes

  17 shared

• Maximilien Bolot

  17 shared

• Spencer K. Clark

  NOAA Geophysical Fluid Dynamics Laboratory

  17 shared

• Linjiong Zhou

  Princeton University

  16 shared

Labs

• The Fueglistaler Research GroupPI

Education

• PhD, D-USYS

  ETH Zurich

  2002