Uncertainty in aerosol–cloud radiative forcing is driven by clean conditions Atmospheric Chemistry and Physics DOI 10.5194/acp-23-4115-2023 21 April 2023 The impact of aerosols on clouds is one of the largest uncertainties in the human forcing of the climate. Aerosol can increase the concentrations of droplets in clouds, but observational and model studies produce widely varying estimates of this effect. We show that these estimates can be reconciled if only polluted clouds are studied, but this is insufficient to constrain the climate impact of aerosol. The uncertainty in aerosol impact on clouds is currently driven by cases with little aerosol. Read more
Natural marine cloud brightening in the Southern Ocean Atmospheric Chemistry and Physics DOI 10.5194/acp-23-1677-2023 13 March 2023 The number of cloud droplets per unit volume is a significantly important property of clouds that controls their reflective properties. Computer models of the Earth’s atmosphere and climate have low skill at predicting the reflective properties of Southern Ocean clouds. Here we investigate the properties of those clouds using satellite data and find that the cloud droplet number and cloud albedo in the Southern Ocean are related to the oceanic phytoplankton abundance near Antarctica. Read more
Product distribution, kinetics, and aerosol formation from the OH oxidation of dimethyl sulfide under different RO2 regimes Atmospheric Chemistry and Physics DOI 10.5194/acp-22-16003-2022 20 February 2023 The atmospheric oxidation of dimethyl sulfide (DMS) is a major natural source of sulfate particles in the atmosphere. However, its mechanism is poorly constrained. In our work, laboratory measurements and mechanistic modelling were conducted to comprehensively investigate DMS oxidation products and key reaction rates. We find that the peroxy radical (RO2) has a controlling effect on product distribution and aerosol yield, with the isomerization of RO2 leading to the suppression of aerosol yield. Read more
Estimating emissions of methane consistent with atmospheric measurements of methane and δ13C of methane Atmospheric Chemistry and Physics DOI 10.5194/acp-22-15351-2022 6 February 2023 Atmospheric methane (CH4) has been growing steadily since 2007 for reasons that are not well understood. Here we determine sources of methane using a technique informed by atmospheric measurements of CH₄ and its isotopologue 13CH4. Measurements of 13CH4 provide for better separation of microbial, fossil, and fire sources of methane than CH4 measurements alone. Compared to previous assessments such as the Global Carbon Project, we find a larger microbial contribution to the post-2007 increase. Read more
The evolution and dynamics of the Hunga Tonga–Hunga Ha’apai sulfate aerosol plume in the stratosphere Atmospheric Chemistry and Physics DOI 10.5194/acp-22-14957-2022 30 January 2023 The long-duration atmospheric impact of the Tonga eruption in January 2022 is a plume of water and sulfate aerosols in the stratosphere that persisted for more than 6 months. We study this evolution using several satellite instruments and analyse the unusual behaviour of this plume as sulfates and water first moved down rapidly and then separated into two layers. We also report the self-organization in compact and long-lived patches. Read more
The climate impact of hydrogen-powered hypersonic transport Atmospheric Chemistry and Physics DOI 10.5194/acp-22-14323-2022 18 January 2023 Very fast aircraft can travel long distances in extremely short times and can fly at high altitudes (15 to 35 km). These aircraft emit water vapour, nitrogen oxides, and hydrogen. Water vapour emissions remain for months to several years at these altitudes and have an important impact on temperature. We investigate two aircraft fleets flying at 26 and 35 km. Ozone is depleted more, and the water vapour perturbation and temperature change are larger for the aircraft flying at 35 km. Read more
Not all types of secondary organic aerosol mix: two phases observed when mixing different secondary organic aerosol types Atmospheric Chemistry and Physics DOI 10.5194/acp-22-13783-2022 11 January 2023 The number of condensed phases in mixtures of different secondary organic aerosol (SOA) types determines their impact on air quality and climate. Here we observe the number of phases in individual particles that contain mixtures of two different types of SOA. We find that SOA mixtures can form one- or two-phase particles, depending on the difference in the average oxygen-to-carbon (O/C) ratios of the two SOA types that are internally mixed within individual particles. Read more
Opinion: Coordinated development of emission inventories for climate forcers and air pollutants Atmospheric Chemistry and Physics DOI 10.5194/acp-22-13201-2022 2 January 2023 Emissions into the atmosphere of greenhouse gases (GHGs) and air pollutants, quantified in emission inventories, impact human health, ecosystems, and the climate. We review how air pollutant and GHG inventory activities have historically been structured and their different uses and requirements. We discuss the benefits of increasing coordination between air pollutant and GHG inventory development efforts, but also caution that there are differences in appropriate methodologies and applications. Read more
Cloud adjustments from large-scale smoke–circulation interactions strongly modulate the southeastern Atlantic stratocumulus-to-cumulus transition Atmospheric Chemistry and Physics DOI 10.5194/acp-22-12113-2022 14 December 2022 Smoke from southern Africa blankets the southeast Atlantic from June-October, overlying a major transition region between overcast and scattered clouds. The smoke affects Earth’s radiation budget by absorbing sunlight and changing cloud properties. We investigate these effects in regional climate and large eddy simulation models based on international field campaigns. We find that large-scale circulation changes more strongly affect cloud transitions than smoke microphysical effects in our case. Read more
Bayesian assessment of chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC) and halon banks suggest large reservoirs still present in old equipment Atmospheric Chemistry and Physics DOI 10.5194/acp-22-11125-2022 16 November 2022 Halocarbons contained in equipment continue to be emitted after production has ceased. These “banks” must be carefully accounted for in evaluating compliance with the Montreal Protocol. We extend a Bayesian model to the suite of regulated chemicals subject to banking. We find that banks are substantially larger than previous estimates, and we identify banks by chemical and equipment type whose future emissions will contribute to global warming and delay ozone-hole recovery if left unrecovered. CFC), hydrochlorofluorocarbon (HCFC) and halon banks suggest large reservoirs still present in old equipment">Read more
