An ice core record from the Guliya ice cap on the Qinghai-Tibetan Plateau provides evidence of regional climatic conditions over the last glacial cycle. 36CI data suggest that the deepest 20 meters of the core may be more than 500,000 years old. The 6180 change across Termination I is -5.4 per mil, similar to that in the Huascarhn (Peru) and polar ice cores. Three Guliya interstadials (Stages 3,5a, and 5c) are marked by increases in 6180 values similar to that of the Holocene and Eemian (-124,000 years ago). The similarity of this pattern to that of CH, records from polar ice cores indicates that global CH, levels and the tropical hydrological cycle are linked. The Late Glacial Stage record contains numerous 200-year oscillations in S180 values and in dust, NH,+, and NO,-levels.

Many open questions exist about the importance of different sources of carbonaceous aerosol, which is a substantial contributor to the global aerosol budget and, therefore, to climate change and human mortality. In this work, 14C was determined in elemental carbon (EC) and different organic carbon (OC) fractions from ambient urban aerosols with aerodynamic diameter <10 μm collected in Zurich (Switzerland). This enabled a more detailed source attribution of the carbonaceous aerosol mass than is possible with other currently available methods. The three major sources, fossil fuel, wood combustion (both anthropogenic emissions), and biogenic emissions, were quantified, making specific regulatory air quality management measures possible. EC originates nearly exclusively from fossil fuel usage during summer, whereas biomass‐burning emissions become substantial during winter with ∼25%, even though this source contributes only marginally to the local energy consumption. For OC, biogenic sources are dominant in summer with ∼60%, where secondary organic aerosol prevails. Wood combustion accounts for up to ∼41% of OC in winter. Fossil fuels represent ∼30% of OC throughout the year.

The origin of two large peaks in the atmospheric radiocarbon (14C) concentration at AD 774/5 and 993/4 is still debated. There is consensus, however, that these features can only be explained by an increase in the atmospheric 14C production rate due to an extraterrestrial event. Here we provide evidence that these peaks were most likely produced by extreme solar events, based on several new annually resolved 10Be measurements from both Arctic and Antarctic ice cores. Using ice core 36Cl data in pair with 10Be, we further show that these solar events were characterized by a very hard energy spectrum with high fluxes of solar protons with energy above 100 MeV. These results imply that the larger of the two events (AD 774/5) was at least five times stronger than any instrumentally recorded solar event. Our findings highlight the importance of studying the possibility of severe solar energetic particle events.

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