Rather than reverting to a dedicated paleoclimate chapter, knowledge about pre-industrial climate should be further integrated with other lines of evidence throughout the next assessment reports by the Intergovernmental Panel on Climate Change.

Here we present summer snowline altitude (SLA) time series for 269 Arctic glaciers. Between 1984 and 2022, SLAs rose ∼ 150 m, equating to a ∼ 127 m shift per 1 °C of summer warming. SLA is most strongly correlated with annual temperature variables, highlighting their dual effect on ablation and accumulation processes. We show that SLAs are rising fastest on low-elevation glaciers and that > 50 % of the studied glaciers could have SLAs that exceed the maximum ice elevation by 2100.

We report aspartic and glutamic acid racemization analyses on Neogloboquadrina pachyderma and Cibicidoides wuellerstorfi from the Arctic Ocean (AO). The rates of racemization in the species are compared. Calibrating the rate of racemization in C. wuellerstorfi for the past 400 ka allows the estimation of sample ages from the central AO. Estimated ages are older than existing age assignments (as previously observed for N. pachyderma), confirming that differences are not due to taxonomic effects.

Accurately dating ocean cores is challenging because the radiocarbon age of water masses varies substantially. We identify ash fragments from eruptions more than 4000 km from their source and use these time markers to develop a new age–depth model for an ocean core in Placentia Bay, North Atlantic. Our results show that the radiocarbon age of waters masses in the bay varied considerably during the last 10 000 years and highlight the potential of using ultra-distal ash deposits in this region.

The Commission on Tephrochronology (COT), formed in 1961, comprises geoscientists who characterize, map, and date tephra (volcanic ash) layers and use them as stratigraphic linking and dating tools in geological, palaeoenvironmental, and archaeological research. We review COT's origins and growth and show how its leadership and activities – hosting meetings, supporting ECRs, developing new analytical and dating methods, and publishing volumes – have strongly influenced tephrochronology globally.