Conveners
3.1 Extreme events and worst-case scenarios (chair Agnieszka Gil-Świderska)
- Florian Mekhaldi (Stockholm U., SE)
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Nicolas Brehm (ETH, CH)11/06/2026, 13:45Invited review
The Sun is the primary energy source of the Earth system, and variations in solar activity can significantly influence climate. While direct observations of solar activity, such as sunspot records, extend back only about 400 years, cosmogenic radionuclides produced by cosmic rays and preserved in tree rings and ice cores provide valuable proxies for reconstructing solar variability over...
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Jian Wang (University of Groningen, NL)11/06/2026, 14:05Solicited
Annual-resolution ¹⁴C records from tree rings have become powerful proxies for detecting extreme solar behaviour, including short-lived cosmic-ray enhancements related to solar energetic particle (SEP) events and variations in solar magnetic activity. A recent study compiling an annually resolved ¹⁴C record from 1–970 CE, based on five new and three existing tree-ring series measured at the...
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Fusa Miyake (Nagoya U., JP)11/06/2026, 14:25Solicited
Cosmogenic nuclides used to detect past solar energetic particle (SEP) events are tree-ring $^{14}$C, and ice-core $^{10}$Be, and $^{36}$Cl. These nuclides serve as key proxies for reconstructing SEP events. To date, multiple extreme SEP events, including the 774 CE event, have been identified from these cosmogenic nuclide records. The magnitudes of these events are estimated to be several...
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Sergey Koldobskiy (University of Oulu)11/06/2026, 14:45
Extreme solar particle events (ESPEs) are caused by rare, enormously intense solar eruptions and can produce globally detectable spikes in tree-ring radiocarbon ($^{14}$C), known as Miyake events, which serve as precise chronological tie-points and indicators of extreme solar activity. After production, radiocarbon is subjected to the complex carbon cycle, including large- scale atmospheric...
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Chitradeep Saha (University of Reading, UK)11/06/2026, 14:57
Long-term solar magnetic variability governs the space climate conditions. These variations also modulate the galactic cosmic ray influx reaching Earth and subsequently regulate the production of cosmogenic isotopes in the Earth's atmosphere. By harnessing the multi-millennial records of these radio-isotope proxies archived in various natural terrestrial reservoirs, such as tree rings and ice...
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Joonas Uusitalo (Helsinki U., FI)11/06/2026, 15:09
Rapid increases in atmospheric radiocarbon ($^{14}$C), known as Miyake events, have been identified across multiple time periods, with Solar Proton Events (SPEs) considered the most probable cause. Among these, the ~660 BC event stands out due to its apparently prolonged rise time compared to other confirmed events such as AD 774–775 and AD 993–994, prompting hypotheses ranging from double...
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Irina Panyushkina (University of Arizona, US)11/06/2026, 15:21
Instrumental observations of extreme solar eruptions are short, restricting their linkages to paleoevents (e.g. Miyake events) derived from cosmogenic $^{14}$C, $^{36}$Cl and $^{10}$Be isotopes of ice cores and tree rings. This constrains estimates of their long-term frequency and probability. The strongest solar proton event (SPE) recorded by ground-level enhancement occurred on 23 February...
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Timothy Jull (University of Arizona, US)11/06/2026, 15:33
Rapid spikes observed in the tree-ring $^{14}$C record are caused by extreme solar proton storms or high-energetic particles events. Six of these “Miyake” events have been confirmed with 10Be in ice cores at 774 CE, 993 CE, 664 BCE, 5259 BCE, 7176 BCE, and 12450 BCE. There are also a number of $^{14}$C excursions attributed to solar effects that are not yet confirmed by other cosmogenic...
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