Abrupt climate change

Climate change is the greatest socio-economic force of the 21st Century, creating uncertainty and threatening basic societal foundations. Ice-core geochemistry suggests that, in the geologically recent past, mean temperatures in the North Atlantic region repeatedly jumped as much as 10°C within years to decades (well within a human lifespan). Today, greenhouse gas emissions are upsetting Earth's radiative balance, driving an overall warming the rate and uniformity of which are unprecedented in at least the last two millennia. Yes, climate change will reshape life on Earth in the coming decades, but how exactly how - and how rapidly - is less clear. Studying past episodes of abrupt climate upheaval is arguably our best bet for anticipating future change and understanding the mechanisms at play. 

My initiation into abrupt climate change occurred in 2010, one beer-fuelled, speculation-filled night in the Lamont Library with Aaron Putnam. Shortly thereafter, Aaron and I, along with fellow UMaine grad student Kurt Rademaker, headed over to Scotland to date the demise of the late-glacial ice cap centred over the Highlands. Thus began a line of inquiry that continues today. As the eastern branch of the great UMaine glacial-geology family tree, my team is mapping glacial deposits in Ireland, Scotland, and mainland Europe, and using cosmogenic beryllium-10 surface-exposure dating to date the climate events those deposits represent. Snowline reconstructions and glacier-climate modelling then allow us to establish the sign and magnitude of those events. 


Collaborators: Brenda Hall, Aaron Putnam, Hal BornsGeorge Denton, & Tom Lowell (UMaine), Kurt Rademaker (Texas A&M), Margaret Jackson (Trinity College Dublin), Steve Barker (Cardiff University), Ruza Ivanovicz (Leeds), Colin Bunce (Galway), Frederik Schenk (Stockholm)

Students/Postdocs/RAsAnouck Roignot, Adrienne ForemanPaulo Rodriguez, Becky Hedderman (Galway), Allie Balter-Kennedy & Holly Thomas (UMaine)

Funded by grants from the Dan & Betty Churchill Foundation and Golden Foundation (UMaine), Gary C. Comer Science & Education Foundation, Global Climate Change Foundation, National Geographic/ Waitt Foundation, American Philosophical Society, Geological Survey Ireland, and Research Ireland.


Related Publications 

Hall, B., Lowell, T., Bromley, G., et al., 2025. Rapid deglaciation of eastern Maine, northeastern North America, during Heinrich Stadial 1. Quaternary Science Reviews 363, p.109444. 

Foreman, A.C., Bromley, G. et al., 2025. Thinning and retreat of the temperate Connemara ice centre, Ireland, during Heinrich Stadial 1 constrained with cosmogenic 10Be dating. Geomorphology 475, 109661. 

Bromley, G., et al., 2023. Lateglacial shifts in seasonality reconcile conflicting North Atlantic temperature signals. J. Geophysical Research. Earth Surface, 128(1). Featured in EOS Editor Highlights

Foreman, A., Bromley, G., et al., 2022. A 10Be-dated record of glacial retreat in Connemara, Ireland, following the Last Glacial Maximum and implications for regional climate. Palaeo, Palaeo, Palaeo 592, p.110901

Bromley, G., et al., 2020 The Berlin moraine complex of northern New Hampshire: Age and implications for interstadial ice sheet dynamics and climate. Quaternary Research 1-14. doi:10.1017/qua.2019.66. 

Bromley, G., et al., 2018. Interstadial rise and Younger Dryas demise of Scotland's last ice fields. Palaeoceanography & Paleoclimatology 33, 412–429. 

Hall, B.L., Borns, H.W., Bromley, G. et al., 2017. Age of the Pineo Ridge System: Implications for behavior of the Laurentide Ice Sheet in eastern Maine, U.S.A., during the last deglaciation. Quat. Sci. Rev. 169, 344–356

Bromley, G. et al., 2016. Comment on 'Was Scotland deglaciated during the Younger Dryas?' by Small and Fabel (2016). Quat. Sci. Rev. 152, 203–206

Bromley, G. et al., 2015. Late glacial fluctuations of the Laurentide Ice Sheet in the White Mountains of Maine and New Hampshire, U.S.A. Quat. Res. 83, 522-530

Bromley, G. et al., 2014. Younger Dryas Deglaciation Of Scotland Driven By Warming Summers. PNAS 111, 6215-6219