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Experiments on sulphuric acid nucleation in low oxygen atmospheres were done in order to investigate the role of nucleation in the Archean atmosphere. Nucleation initiated by photolysis of SO 2 and subsequent reaction between atomic O and SO 2 was measured with a PSM and a separate CPC. The parameters were < 10 ppm O 2 with varying levels of SO 2 (4 levels from 40 to 105 ppb), RH (3 levels from 0 to 51%), UV light (254 nm, 4 levels from 55 to 100% power), and ionization (2 levels: Background (∼ 3 cm −3 s −1 ) and increased w. gamma sources (∼ 42 cm −3 s −1 )). We find that nucleation is possible under these conditions and that the measured formation rates correlate positively with all varied parameters. This suggests that the sulphuric acid nucleation system could have played a role in the Archean atmosphere. • Aerosol particles could be nucleated with very little oxygen on Ancient Earth. • Sulphuric acid could be formed through photolysis of sulphur dioxide. • Sensitivity to relative humidity, UV levels, SO2, and ionization was tested. [ABSTRACT FROM AUTHOR]

We review the long-term climate variations during the last 540 million years (Phanerozoic Eon). We begin with a short summary of the relevant geological and geochemical datasets available for the reconstruction of long-term climate variations. We then explore the main drivers of climate that appear to explain a large fraction of these climatic oscillations. The first is the long-term trend in atmospheric CO 2 due to geological processes, while the second is the atmospheric ionization due to the changing galactic environment. Other drivers, such as albedo and geographic effects, are of secondary importance. In this review, we pay particular attention to problems that may affect the measurements of temperature obtained from oxygen isotopes, such as the long-term changes in the concentration of δ 18 O seawater., (© 2022 The Authors. Annals of the New York Academy of Sciences published by Wiley Periodicals LLC on behalf of New York Academy of Sciences.)

Atmospheric ionization produced by cosmic rays has been suspected to influence aerosols and clouds, but its actual importance has been questioned. If changes in atmospheric ionization have a substantial impact on clouds, one would expect to observe significant responses in Earth's energy budget. Here it is shown that the average of the five strongest week-long decreases in atmospheric ionization coincides with changes in the average net radiative balance of 1.7 W/m[Formula: see text] (median value: 1.2 W/m[Formula: see text]) using CERES satellite observations. Simultaneous satellite observations of clouds show that these variations are mainly caused by changes in the short-wave radiation of low liquid clouds along with small changes in the long-wave radiation, and are almost exclusively located over the pristine areas of the oceans. These observed radiation and cloud changes are consistent with a link in which atmospheric ionization modulates aerosol's formation and growth, which survive to cloud condensation nuclei and ultimately affect cloud formation and thereby temporarily the radiative balance of Earth., (© 2021. The Author(s).)