
Simone TilmesNSF National Center for Atmospheric Research
Simone Tilmes
PhD
About
414
Publications
78,092
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
18,953
Citations
Introduction
Additional affiliations
April 2005 - present
Publications
Publications (414)
Large and moderate volcanic eruptions significantly impact Earth's atmosphere by releasing sulphur emissions, thereby affecting atmospheric dynamics and QBO. Using the ECHAM6-HAMMOZ model, we show the impact of eruptive volcanoes on the tropical stratosphere and Quasi-biennial oscillation (QBO) from 2001 to 2013. Our simulations with volcanoes, whe...
It is increasingly evident that maintaining global warming at levels below those agreed in the legally binding international treaty on climate change. i.e., the Paris Agreement, is going to be extremely challenging using conventional mitigation techniques. While future scenarios of climate change frequently include extensive use of terrestrial and...
In this work, we apply the GFDL Earth System Model (GFDL‐ESM4.1) to explore the climate responses to a stratospheric aerosol injection (SAI) scenario that aims to restrict global warming to 2.0°C above pre‐industrial levels (1850–1900) under the CMIP6 overshoot scenario (SSP5‐34‐OS). Simulations of this SAI scenario with the CESM Whole Atmosphere C...
A new Stratospheric Aerosol Intervention (SAI) experiment has been designed for the Chemistry- Climate Modeling Initiative (CCMI-2022) to assess the impacts of SAI on stratospheric chemistry and dynamical responses and inter-model differences using a constrained setup with a prescribed stratospheric aerosol distribution and fixed sea-surface temper...
The 2022 Hunga volcanic eruption injected a significant amount of water vapor and a moderate amount of sulfur dioxide into the stratosphere causing observable responses in the climate system. We have developed a model-observation comparison project to investigate the evolution of volcanic water and aerosols, and their impacts on atmospheric dynamic...
This study characterizes the spatial and vertical nature of aerosol hygroscopicity in Southeast Asia and relates it to aerosol composition and sources. Aerosol hygroscopicity via the light scattering hygroscopic growth factor, f(RH), is calculated from the amplification of PM5 aerosol (Dp < 5 μm) scattering measurements from < 40 % to 82 % relative...
While the dominant role of halogens in Arctic ozone loss during spring has been widely studied in the last decades, the impact of sea-ice halogens on surface ozone abundance over the northern hemisphere (NH) mid-latitudes remains unquantified. Here, we use a state-of-the-art global chemistry-climate model including polar halogens (Cl, Br, and I), w...
With surface temperatures already reaching unprecedented highs, resulting in significant adverse consequences for societies and ecosystems, there is an increasing call to expand research into climate interventions, including Stratospheric Aerosol Intervention (SAI). However, research and dissemination are currently fragmented and would benefit from...
The South Asian summer monsoon (SAM) bears significant importance for agriculture, water resources, economy, and environmental aspects of the region for more than 1.5 billion people. To minimize the adverse impacts of global warming, Stratospheric Aerosol Intervention (SAI) has been proposed to lower surface temperatures by reflecting a portion of...
Marine cloud brightening (MCB) is a geoengineering proposal to cool atmospheric temperatures and reduce climate change impacts. As large-scale approaches to stabilize global mean temperatures pose governance challenges, regional interventions may be more attractive near term. Here we investigate the efficacy of regional MCB in the North Pacific to...
Solar radiation modification (SRM) aims to artificially cool the Earth, counteracting warming from anthropogenic greenhouse gases by increasing the reflection of incoming sunlight. One SRM strategy is stratospheric aerosol injection (SAI), which mimics explosive volcanoes by injecting aerosols into the stratosphere. There are concerns that SAI coul...
A growing number of general circulation models are adapting interactive sulfur and aerosol schemes to improve the representation of relevant physical and chemical processes and associated feedbacks. They are motivated by investigations of climate response to major volcanic eruptions and potential solar geoengineering scenarios. However, uncertainti...
This study aims to assess the impact of Stratospheric Aerosol Injection (SAI) on the coastal upwelling in the northern Gulf of Guinea based, on upwelling index computation and using the Community Earth System Model from the Geoengineering Large Ensemble (GLENS) project. GLENS project targets not only maintaining the global temperature but also the...
This is the second of two papers in which we study the dependency of the impacts of stratospheric sulfur injections on the model and injection strategy used. Here, aerosol optical properties from simulated stratospheric aerosol injections using two aerosol models (modal scheme M7 and sectional scheme SALSA), as described in Part 1 , are implemented...
Sedimentary records indicate that atmospheric dust has increased substantially since preindustrial times. However, state-of-the-art global Earth system models (ESMs) are unable to capture this historical increase, posing challenges in assessing the impacts of desert dust on Earth’s climate. To address this issue, we construct a globally gridded dus...
The Geoengineering Model Intercomparison Project (GeoMIP) has proposed multiple model experiments during phases 5 and 6 of the Climate Model Intercomparison Project (CMIP), with the latest set of model experiments proposed in 2015. With phase 7 of CMIP in preparation and with multiple efforts ongoing to better explore the potential space of outcome...
Following the Hunga Tonga–Hunga Ha'apai (HTHH) eruption in January 2022, stratospheric ozone depletion was observed at Southern Hemisphere mid‐latitudes and over Antarctica during the 2022 austral wintertime and springtime, respectively. The eruption injected sulfur dioxide and unprecedented amounts of water vapor into the stratosphere. This work e...
Mitigating global warming through stratospheric aerosol injection (SAI), which aims to reproduce the cooling effects of tropical volcanoes on surface climate, is emerging as a potential strategy for limiting near–surface global warming to around 1.5–2◦C above pre–industrial levels. However, knowledge of how the stratospheric circulation will respon...
Sulfur‐based stratospheric aerosol intervention (SAI) can cool the climate, but also heats the tropical lower stratosphere if done with injections at low latitudes. We explore the role of this heating in the climate response to SAI, by using mechanistic experiments that remove the effects of longwave absorption of sulfate aerosols above the tropopa...
Chemistry Climate Models (CCMs) are essential tools for characterizing and predicting the role of atmospheric composition and chemistry in Earth's climate system. This study demonstrates the use of airborne in situ observations to diagnose the representation of chemical composition and transport by CCMs. Process‐based diagnostics using dynamical an...
Desert dust is an important atmospheric aerosol that affects the Earth's climate, biogeochemistry, and air quality. However, current Earth system models (ESMs) struggle to accurately capture the impact of dust on the Earth's climate and ecosystems, in part because these models lack several essential aeolian processes that couple dust with climate a...
Water storage plays a profound role in the lives of people across the Middle East and North Africa (MENA) as it is the most water-stressed region worldwide. The lands around the Caspian and Mediterranean seas are simulated to be very sensitive to future climate warming. Available water capacity depends on hydroclimate variables such as temperature...
Stratospheric Aerosol Geoengineering (SAG) is proposed to offset global warming; however, the use of this approach can an impact on the hydrological cycle. We used simulations from Coupled Model Intercomparison Project (CMIP5) and Geoengineering Model Intercomparison Project (G3 simulation) to analyze the impacts of SAG on precipitation (P) and to...
The Hunga Tonga‐Hunga Ha'apai (HTHH) volcanic eruption in January 2022 injected unprecedented amounts of water vapor (H2O) and a moderate amount of the aerosol precursor sulfur dioxide (SO2) into the Southern Hemisphere (SH) tropical stratosphere. The H2O and aerosol perturbations have persisted during 2022 and early 2023 and dispersed throughout t...
Plain Language Summary
The injection of reflective aerosols, or their precursors, into the lower stratosphere (Stratospheric Aerosol Injection, SAI) has been proposed as a temporary measure to offset some of the adverse impacts of climate change whilst atmospheric concentrations of greenhouses are being stabilized and, ultimately, reduced. The impa...
This is the second of two papers where we study the dependency of the impacts of stratospheric sulfur injections on the used model and injection strategy. Here, aerosol optical properties from simulated stratospheric aerosol injections using two aerosol models (modal scheme M7 and sectional scheme SALSA), as described in Part 1, are implemented con...
The Hunga Tonga Hunga‐Ha'apai (HTHH) volcanic eruption on 15 January 2022 injected water vapor and SO2 into the stratosphere. Several months after the eruption, significantly stronger westerlies, and a weaker Brewer‐Dobson circulation developed in the stratosphere of the Southern Hemisphere and were accompanied by unprecedented temperature anomalie...
We implemented the Community Aerosol and Radiation Model for Atmospheres (CARMA) in both the high- and low-top model versions of the Community Earth System Model Version 2 (CESM2). CARMA is a sectional microphysical model, which we use for aerosol in both the troposphere and stratosphere. CARMA is fully coupled to chemistry, clouds, radiation, and...
The Multi-Scale Infrastructure for Chemistry and Aerosols Version 0 (MUSICAv0) is a new community modeling infrastructure that enables the study of atmospheric composition and chemistry across all relevant scales. We develop a MUSICAv0 grid with Africa refinement (∼ 28 km × 28 km over Africa). We evaluate the MUSICAv0 simulation for 2017 with in si...
Near-term in-plume ozone depletion was observed for about 10 d by the Aura Microwave Limb Sounder (MLS) right after the January 2022 Hunga Tonga–Hunga Ha'apai (HTHH) eruption. This work analyzes the dynamic and chemical causes of this ozone depletion. The results show that the large water injection (∼ 150 Tg) from the HTHH eruption, with ∼ 0.0013 T...
The Geoengineering Model Intercomparison Project (GeoMIP) has proposed multiple model experiments during the phases 5 and 6 of the Climate Model Intercomparison Project (CMIP), with the latest set of model experiment proposed in 2015. With phase 7 of CMIP in preparation, and with multiple efforts ongoing to better explore the potential space of out...
Estimates of ground-level ozone concentrations have been improved through data fusion of observations and atmospheric chemistry models. Our previous global ozone estimates for the Global Burden of Disease study corrected for bias uniformly across continents and then corrected near monitoring stations using the Bayesian Maximum Entropy (BME) framewo...
Stratospheric aerosol intervention (SAI) is a proposed strategy to reduce the effects of anthropogenic climate change. There are many temperature targets that could be chosen for a SAI implementation, which would regionally modify climatically relevant variables such as surface temperature, precipitation, humidity, total solar radiation and diffuse...
Among the physical processes controlling aerosol vertical profiles, in‐cloud wet removal is of utmost importance while its representation in global climate models (GCMs) is crude. In this study, we implement into the Community Atmosphere Model version 6 (CAM6) a physically‐based aerosol wet removal parameterization scheme that explicitly treats aer...
The Middle East and North Africa (MENA) region is the dustiest region in the world, and understanding the projected changes in the dust concentrations in the region is crucial. Stratospheric aerosol injection (SAI) geoengineering aims to reduce global warming by increasing the reflection of a small amount of the incoming solar radiation to space, h...
Marine cloud brightening is a solar geoengineering1–3 proposal to cool atmospheric temperatures and reduce some impacts of climate change. To-date, modeling studies of solar geoengineering have primarily focused on large-scale schemes with objectives of stabilizing or mediating changes in global mean temperature4–7. However, these global proposals...
Simulating whole atmosphere dynamics, chemistry, and physics is computationally expensive. It can require high vertical resolution throughout the middle and upper atmosphere, as well as a comprehensive chemistry and aerosol scheme coupled to radiation physics. An unintentional outcome of the development of one of the most sophisticated and hence co...
Sulfate aerosol in the stratosphere is an important climate driver, causing solar dimming in the years after major volcanic eruptions. Hence, a growing number of general circulation models are adapting interactive sulfur and aerosol schemes to improve the representation of relevant chemical processes and associated feedbacks. However, uncertainties...
Following the Hunga Tonga–Hunga Ha’apai (HTHH) eruption in January 2022, stratospheric ozone depletion was observed in the Southern Hemisphere mid-latitudes and Antarctica during the 2022 austral wintertime and springtime. This eruption injected sulfur dioxide and unprecedented amounts of water vapor into the stratosphere. This work examines and qu...
Chemistry transport models (CTMs) are essential tools for characterizing and predicting the role of atmospheric composition and chemistry in Earth’s climate system. This study demonstrates the use of airborne in situ observations to diagnose the representation of atmospheric composition by global CTMs. Process-based diagnostics are developed which...
Water storage plays a profound role in the lives of people across the Middle East and North Africa (MENA) as it is the most water stressed region worldwide. The lands around the Caspian and Mediterranean Seas are simulated to be very sensitive to future climate warming. Available water capacity depends on hydroclimate variables such as temperature...
Stratospheric aerosol injection (SAI) of reflective sulfate aerosols has been proposed to temporarily reduce the impacts of global warming. In this study, we compare two SAI simulations which inject at different altitudes to provide the same amount of cooling, finding that lower‐altitude SAI requires 64% more injection. SAI at higher altitudes cool...
The Community Earth System Model (CESM) community has been providing versatile modeling options, with simple to complex chemistry and aerosol schemes in a single model, in order to support the broad scientific community with various research interests. While different model configurations are available in CESM and these can be used for different fi...
Reactive halogens (X + XO, X = I, Br or Cl) catalytically destroy a fraction of tropospheric ozone under present‐day (PD) conditions, however, their distribution and potential impact on tropospheric ozone under pre‐industrial (PI) conditions remain largely unexplored. This study uses the Community Atmosphere Model with Chemistry (CAM‐Chem) to inves...
Model intercomparison studies often report a large spread in simulation results, but quantifying the causes of these differences is hindered by the fact that several processes contribute to the model spread simultaneously. Here we use the Multi‐Scale Infrastructure for Chemistry and Aerosols (MUSICA) version 0 to investigate the model resolution de...
Observational evidence shows the ubiquitous presence of ocean-emitted short-lived halogens in the global atmosphere1–3. Natural emissions of these chemical compounds have been anthropogenically amplified since pre-industrial times4–6, while, in addition, anthropogenic short-lived halocarbons are currently being emitted to the atmosphere7,8. Despite...
In-plume ozone depletion was observed for about ten days by Microwave Limb Sounder (Aura/MLS) right after the January 2022 Hunga Tonga-Hunga Ha’apai (HTHH) eruption. This work analyzes the dynamic and chemical causes of this ozone depletion. The results show that the large water injection (~150 Tg) from the HTHH eruption, with ~0.0013 Tg injection...
Single Forcing Large Ensembles are a relatively new tool for quantifying the contributions of different anthropogenic and natural forcings to the historical and future projected evolution of the climate system. This study introduces a new single forcing large ensemble with the Community Earth system Model version 2 which can be used to separate the...
Desert dust is an important atmospheric aerosol that affects the Earth's climate, biogeochemistry, and air quality. However, current Earth system models (ESMs) struggle to accurately capture the impact of dust on the Earth’s climate and ecosystems, in part because these models lack several essential aeolian processes that couple dust with climate a...
The impacts of Stratospheric Aerosol Injection (SAI) on the atmosphere and surface climate depend on when and where the sulfate aerosol precursors are injected, as well as on how much surface cooling is to be achieved. We use a set of CESM2(WACCM6) SAI simulations achieving three different levels of global mean surface cooling and demonstrate that...
We investigate the potential impact of stratospheric aerosol intervention (SAI) on the spatiotemporal behavior of large-scale climate teleconnection patterns represented by the North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), El Niño–Southern Oscillation (ENSO) and Atlantic Multidecadal Oscillation (AMO) indices using simulation...
In contrast to the general stratospheric ozone recovery following international agreements, recent observations show an ongoing net ozone depletion in the tropical lower stratosphere (LS). This depletion is thought to be driven by dynamical transport accelerated by global warming, while chemical processes have been considered to be unimportant. Her...
We quantify future changes in wildfire burned area and carbon emissions in the 21st century under four Shared Socioeconomic Pathways (SSPs) scenarios and two SSP5-8.5-based solar geoengineering scenarios with a target surface temperature defined by SSP2-4.5 – solar irradiance reduction (G6solar) and stratospheric sulfate aerosol injections (G6sulfu...
The Geoengineering Model Intercomparison Project (GeoMIP) is a coordinating framework, started in 2010, that includes a series of standardized climate model experiments aimed at understanding the physical processes and projected impacts of solar geoengineering. Numerous experiments have been conducted, and numerous more have been proposed as “test-...
We implemented the Community Aerosol and Radiation Model for Atmospheres (CARMA) in both the high and low-top model versions of the Community Earth System Model Version 2 (CESM2). CARMA is a sectional microphysical model, which we use for aerosol in both the troposphere and stratosphere. CARMA is fully coupled to chemistry, clouds, radiation, and t...