Climate Projections Very Likely Underestimate Future Volcanic Forcing and Its Climatic Effects

Standard climate projections represent future volcanic eruptions by a constant forcing inferred from 1850 to 2014 volcanic forcing. Using the latest ice-core and satellite records to design stochastic eruption scenarios, we show that there is a 95% probability that explosive eruptions could emit more sulfur dioxide (SO2) into the stratosphere over 2015–2100 than current standard climate projections (i.e., ScenarioMIP). Our simulations using the UK Earth System Model with interactive stratospheric aerosols show that for a median future eruption scenario, the 2015–2100 average global-mean stratospheric aerosol optical depth (SAOD) is double that used in ScenarioMIP, with small-magnitude eruptions (<3 Tg of SO2) contributing 50% to SAOD perturbations. We show that volcanic effects on large-scale climate indicators, including global surface temperature, sea level and sea ice extent, are underestimated in ScenarioMIP because current climate projections do not fully account for the recurrent frequency of volcanic eruptions of different magnitudes

Research data supporting "Climate Projections Very Likely Underestimate Future Volcanic Forcing and its Climatic Effects"

This dataset contains research data that supports the publication "Climate Projections Very Likely Underestimate Future Volcanic Forcing and its Climatic Effects". This dataset contains (1) 1000-member of stochastic future eruption scenarios from 2015 to 2100, generated from resampling historical eruption records from ice-cores and satellites; and (2) annual time series data of climate variables output from the UKESM-VPLUME modelling framework. The data variables include global mean surface temperature (in K), global mean stratospheric aerosol optical depth, global net radiative forcing at the top-of-the-atmosphere (in W/m²), global ocean heat content (in J), global precipitation (in mm/day), global sea level (in m), global sea ice extent (in km²), and the Atlantic Meridional Overturning Circulation at 26ºN (in Sv). The stochastic scenarios are stored in HDF5 format. The annual time series data of each variable is stored as a zip file, which contains the data files for 8 different eruption scenarios (NOVOLC, CONST VOLC, VOLC2.5, VOLC50-1, VOLC50-2, VOLC50-1S, VOLC50-2S, VOLC98) in netcdf format. In each data file, annual data of the above listed climate variables (3 ensemble members) are included. Please refer to the publication for details of the eruption scenarios

Importance of sulfate radical anion formation and chemistry in heterogeneous OH oxidation of sodium methyl sulfate, the smallest organosulfate

Abstract. Organosulfates are important organosulfur compounds present in atmospheric particles. While the abundance, composition, and formation mechanisms of organosulfates have been extensively investigated, it remains unclear how they transform and evolve throughout their atmospheric lifetime. To acquire a fundamental understanding of how organosulfates chemically transform in the atmosphere, this work investigates the heterogeneous OH radical-initiated oxidation of sodium methyl sulfate (CH3SO4Na) droplets, the smallest organosulfate detected in atmospheric particles, using an aerosol flow tube reactor at a high relative humidity of 85 %. Aerosol mass spectra measured by a soft atmospheric pressure ionization source (Direct Analysis in Real Time, DART) coupled with a high-resolution mass spectrometer showed that neither functionalization nor fragmentation products are detected. Instead, the ion signal intensity of the bisulfate ion (HSO4−) has been found to increase significantly after OH oxidation. We postulate that sodium methyl sulfate tends to fragment into a formaldehyde (CH2O) and a sulfate radical anion (SO4•−) upon OH oxidation. The formaldehyde is likely partitioned back to the gas phase due to its high volatility. The sulfate radical anion, similar to OH radical, can abstract a hydrogen atom from neighboring sodium methyl sulfate to form the bisulfate ion, contributing to the secondary chemistry. Kinetic measurements show that the heterogeneous OH reaction rate constant, k, is (3.79 ± 0.19) × 10−13 cm3 molecule−1 s−1 with an effective OH uptake coefficient, γeff, of 0.17 ± 0.03. While about 40 % of sodium methyl sulfate is being oxidized at the maximum OH exposure (1.27 × 1012 molecule cm−3 s), only a 3 % decrease in particle diameter is observed. This can be attributed to a small fraction of particle mass lost via the formation and volatilization of formaldehyde. Overall, we firstly demonstrate that the heterogeneous OH oxidation of an organosulfate can lead to the formation of sulfate radical anion and produce inorganic sulfate. Fragmentation processes and sulfate radical anion chemistry play a key role in determining the compositional evolution of sodium methyl sulfate during heterogeneous OH oxidation. </jats:p

Effects of Relative Humidity and Particle Phase Water on the Heterogeneous OH Oxidation of 2‑Methylglutaric Acid Aqueous Droplets

Organic aerosols can exist as aqueous droplets, with variable water content depending on their composition and environmental conditions (e.g., relative humidity (RH)). Recent laboratory studies have revealed that oxidation kinetics in highly concentrated droplets can be much slower than those in dilute solutions. However, it remains unclear whether aerosol phase water affects the formation of reaction products physically and/or chemically. In this work, we investigate the role of aerosol phase water on the heterogeneous chemistry of aqueous organic droplets consisting of 2-methylglutaric acid (2-MGA), measuring the reaction kinetics and the reaction products upon heterogeneous OH oxidation over a range of RH. An atmospheric pressure soft ionization source (direct analysis in real time, DART) coupled with a high-resolution mass spectrometer is used to obtain real-time molecular information on the reaction products. Aerosol mass spectra show that the same reaction products are formed at all measured RH. At a given reaction extent of the parent 2-MGA, the aerosol composition is independent of RH. These results suggest the aerosol phase water does not alter reaction mechanisms significantly. Kinetic measurements find that the effective OH uptake coefficient, γ_eff, decreases with decreasing RH below 72%. Isotopic exchange measurements performed using aerosol optical tweezers reveal water diffusion coefficients in the 2-MGA droplets to be 3.0 × 10^–13 to 8.0 × 10^–13 m² s^–1 over the RH range of 47–58%. These values are comparable to those of other viscous organic aerosols (e.g., citric acid), indicating that 2-MGA droplets are likely to be viscous at low humidity. Smaller γ_eff at low RH is likely attributed to the slower diffusion of reactants within the droplets. Taken together, the observed relationship between the γ_eff and RH is likely attributed to changes in aerosol viscosity rather than changes in reaction mechanisms

Disproportionate impacts of the COVID-19 pandemic on early career researchers and disabled researchers in volcanology

Peer reviewed: TrueThe COVID-19 pandemic has brought unprecedented challenges to researchers worldwide, and extensive studies have demonstrated that its impacts since March 2020 have been unequal, including across research discipline, gender, and career status. In 2023, as we navigate the post-pandemic times, questions persist regarding potential disparities and enduring effects faced by volcanology researchers, whose activities range from field work in remote areas to laboratory experiments and numerical modelling. In this study, we explore the multifaceted impacts of the pandemic on volcanology researchers through an online survey distributed globally from January to March 2023. Our survey findings reveal that a considerable fraction of volcanology researchers (44%–62%) face longer-term challenges from the pandemic that continue to impact their research, with a notably higher proportion among early career researchers (62%) and researchers with disabilities (76%). In addition, over half (52%) of all surveyed researchers indicated that they had left or considered leaving academia due to pandemic-related factors. A significantly higher proportion of disabled researchers (56%–70%) had left or considered leaving academia compared to researchers without disabilities (42%). Our findings underscore the pandemic’s long-lasting and disproportionate impacts on early career and disabled volcanology researchers. We emphasis the need for concerted efforts by research organisations and funding bodies to mitigate the pandemic’s enduring impacts, and stress the importance of making conferences accessible to support disabled researchers’ participation. As the pandemic’s long-lasting impacts ripple across the broader scientific community, the insights from this research can be used for fostering equitable practices and shaping policies beyond volcanology to other research disciplines

Disproportionate impacts of the COVID-19 pandemic on early career researchers and disabled researchers in volcanology

The COVID-19 pandemic has brought unprecedented challenges to researchers worldwide, and extensive studies have demonstrated that its impacts since March 2020 have been unequal, including across research discipline, gender, and career status. In 2023, as we navigate the post-pandemic times, questions persist regarding potential disparities and enduring effects faced by volcanology researchers, whose activities range from field work in remote areas to laboratory experiments and numerical modelling. In this study, we explore the multifaceted impacts of the pandemic on volcanology researchers through an online survey distributed globally from January to March 2023. Our survey findings reveal that a considerable fraction of volcanology researchers (44%–62%) face longer-term challenges from the pandemic that continue to impact their research, with a notably higher proportion among early career researchers (62%) and researchers with disabilities (76%). In addition, over half (52%) of all surveyed researchers indicated that they had left or considered leaving academia due to pandemic-related factors. A significantly higher proportion of disabled researchers (56%–70%) had left or considered leaving academia compared to researchers without disabilities (42%). Our findings underscore the pandemic’s long-lasting and disproportionate impacts on early career and disabled volcanology researchers. We emphasis the need for concerted efforts by research organisations and funding bodies to mitigate the pandemic’s enduring impacts, and stress the importance of making conferences accessible to support disabled researchers’ participation. As the pandemic’s long-lasting impacts ripple across the broader scientific community, the insights from this research can be used for fostering equitable practices and shaping policies beyond volcanology to other research disciplines.</jats:p

Chemical Transformation of Methanesulfonic Acid and Sodium Methanesulfonate through Heterogeneous OH Oxidation

Methanesulfonic acid (CH₃SO₃H, MSA) is one of the major organosulfur acids formed from the photochemical oxidation of dimethyl sulfide (DMS) produced by oceanic phytoplankton. MSA can react with metal halides (e.g., sodium chloride) in ambient aerosols to form methanesulfonate salts (e.g., sodium methanesulfonate, CH₃SO₃Na). While the formation processes of MSA and its salts are reasonably well understood, their subsequent chemical transformations in the atmosphere are not fully resolved. MSA and its salts accumulate near the aerosol surface due to their surface activities, which make them available to heterogeneous oxidation at the gas–aerosol interface by oxidants such as hydroxyl (OH) radicals. In this work, the compositional changes of aerosol comprised of MSA and its sodium salt (CH₃SO₃Na) are measured following heterogeneous OH oxidation. An aerosol flow tube reactor is coupled with a soft atmospheric pressure ionization source (Direct Analysis in Real Time, DART) and a high-resolution mass spectrometer at a relative humidity (RH) of 90%. DART-aerosol mass spectra reveal that MSA and CH₃SO₃Na can be detected as methanesulfonate ion (CH₃SO₃^–) with minimal fragmentation in the negative ionization mode. Kinetic measurements show that OH oxidation with MSA and CH₃SO₃Na has an effective OH uptake coefficient of 0.45 ± 0.14 and 0.20 ± 0.06, respectively, revealing that MSA reacts with OH radical faster than its sodium salt. One possibility for the difference in reactivity of these two compounds is that CH₃SO₃Na is more hygroscopic than MSA. The increase in the coverage of water molecules at the surface of CH₃SO₃Na might reduce the reactive collision probability between CH₃SO₃^– and OH radicals, resulting in a smaller reaction rate. MSA and CH₃SO₃Na dissociate to form CH₃SO₃^–, which tends to fragment into formaldehyde (HCHO) and a sulfite radical (SO₃^•–) upon oxidation. Formaldehyde partitions back to the gas phase owing to its high volatility, and SO₃^•– can initiate a series of chain reactions involving various inorganic sulfur radicals and ions in the aerosol phase. Overall, the fragmentation and SO₃^•–-initiated chemistry are the major processes controlling the chemical evolution of MSA and its sodium salt aerosols during heterogeneous OH oxidation

Higher Estimated Net Endogenous Acid Production May Be Associated with Increased Prevalence of Nonalcoholic Fatty Liver Disease in Chinese Adults in Hong Kong

<div><p>Nonalcoholic fatty liver disease (NAFLD) has been associated with reduced growth hormone levels and signaling. Such hormonal changes also occur in metabolic acidosis. Since mild metabolic acidosis can be diet induced, diet-induced acid load may constitute a nutritional factor with possible influence on NAFLD development. This study explored whether a higher diet-induced acid load is associated with an increased likelihood of NAFLD. Apparently healthy Chinese adults (330 male, 463 female) aged 19-72 years were recruited through population screening between 2008 and 2010 in a cross-sectional population-based study in Hong Kong. Estimated net endogenous acid production (NEAP) was calculated using Frassetto’s method and potential renal acid load (PRAL) was calculated using Remer’s method based on dietary data from a food frequency questionnaire. NAFLD was defined as intrahepatic triglyceride content at >5% by proton-magnetic resonance spectroscopy. Possible advanced fibrosis was defined as liver stiffness at >7.9 kPa by transient elastography. Multivariate logistic regression models were used to examine the association between each measure of dietary acid load and prevalent NAFLD or possible advanced fibrosis with adjustment for potential anthropometric and lifestyle factors. 220 subjects (27.7%) were diagnosed with NAFLD. Estimated NEAP was positively associated with the likelihood of having NAFLD after adjustment for age, sex, body mass index, current drinker status and the presence of metabolic syndrome [OR (95% CI) = 1.25 (1.02-1.52), <i>p</i> = 0.022]. The association was slightly attenuated but remained significant when the model was further adjusted for other dietary variables. No association between PRAL and NAFLD prevalence was observed. Both estimated NEAP and PRAL were not associated with the presence of possible advance fibrosis. Our findings suggest that there may be a modest association between diet-induced acid load and NAFLD. More studies are needed to ascertain the link between diet-induced acid load and NAFLD and to investigate the underlying mechanisms.</p></div

Diet-Quality Scores and Prevalence of Nonalcoholic Fatty Liver Disease: A Population Study Using Proton-Magnetic Resonance Spectroscopy

<div><p>Dietary pattern analysis is an alternative approach to examine the association between diet and nonalcoholic fatty liver disease (NAFLD). This study examined the association of two diet-quality scores, namely Diet Quality Index-International (DQI-I) and Mediterranean Diet Score (MDS) with NAFLD prevalence. Apparently healthy Chinese adults (332 male, 465 female) aged 18 years or above were recruited through a population screening between 2008 and 2010 in a cross-sectional population-based study in Hong Kong. DQI-I and MDS, as well as major food group and nutrient intakes were calculated based on dietary data from a food frequency questionnaire. NAFLD was defined as intrahepatic triglyceride content at ≥5% by proton-magnetic resonance spectroscopy. Multivariate logistic regression models were used to examine the association between each diet-quality score or dietary component and prevalent NAFLD with adjustment for potential lifestyle, metabolic and genetic factors. A total of 220 subjects (27.6%) were diagnosed with NAFLD. DQI-I but not MDS was associated with the prevalence of NAFLD. A 10-unit decrease in DQI-I was associated with 24% increase in the likelihood of having NAFLD in the age and sex adjusted model (95% CI: 1.06–1.45, <i>p</i> = 0.009), and the association remained significant when the model was further adjusted for other lifestyle factors, metabolic and genetic factors [OR: 1.26 (95% CI: 1.03–1.54), <i>p</i> = 0.027]. Multivariate regression analyses showed an inverse association of the intake of vegetables and legumes, fruits and dried fruits, as well as vitamin C with the NAFLD prevalence (<i>p</i><0.05). In conclusion, a better diet quality as characterized by a higher DQI-I and a higher consumption of vegetables, legumes and fruits was associated with a reduced likelihood of having NAFLD in Hong Kong Chinese.</p></div