Ultra-high-precision measurements of carbon-14 and its application for space weather and space climate research

This paper reviews recent progress in high-precision carbon-14 measurements in tree rings and their importance for accurately reconstructing past solar activity cycles as well as extreme solar and galactic cosmic-ray events. While measurements with conventional precision of accelerator mass spectrometry have provided valuable insights into long-term solar variability and have contributed to the discovery of candidates for extremely intense solar proton events in the past, their limited precision often blurs short-term signals. High-precision analyses, on the other hand, enable us not only to resolve the 11-year solar cycle more clearly, but also to disentangle transient cosmic-ray events, including candidates for extreme solar proton events, from the background solar cycle modulation. Without achieving such precision, transient signals may be smeared into the cycle variability, leading to uncertainties in the reconstruction of solar cycle properties themselves. Moreover, improved precision dramatically increases the number of detectable transient events, opening a new window into the occurrence frequency and intensity distribution. By reviewing our recent high-precision datasets alongside related archives, we demonstrate how this methodological advance enhances our understanding of both the cyclic and sporadic components of solar activity. This article is part of the Theo Murphy meeting issue 'Radiocarbon and cosmic radiation events'.