Tropical palaeoclimate

Spanning 23.5◦N–23.5◦S latitude, the tropics are the single largest climate zone on Earth and the primary source of heat and water vapour for our climate system. Because of this, the tropics have the potential to propagate climatic perturbations rapidly and globally. Rather than a passive by-stander to global change, we increasingly view the tropics as both the heat engine of Earth's climate and the source of abrupt, large-scale shifts. But how to connect the dots? 

For the last two decades, I have been working in the tropical Andes (Peru since 2005, Colombia since 2012), where my colleagues and I use relict moraines to reconstruct tropical Late Pleistocene climate change. This programme involves geomorphic mapping, snowline reconstruction, and in situ cosmogenic nuclide surface-exposure dating (helium-3 in volcanic areas, beryllium-10 in crystalline areas). So far, this work has helped establish (1) that both the timing and magnitude of the Last Glacial Maximum in the tropics were broadly synchronous with events at higher latitudes, (2) that high-magnitude deglaciation dominated Heinrich Stadial 1, as at higher latitudes of both hemispheres, (3) and that the pronounced late-glacial readvance of tropical glaciers (and thus atmospheric cooling) coincided with the Antarctic Cold Reversal, while the subsequent Younger Dryas was a period of resumed warming. At present, we are also working on improving the accuracy of cosmogenic nuclide production rates in the Andes, which is very nerdy but oh so exciting. meanwhile, Drew Gorin's 2024 paper in Science reports the findings of a collaborative project for which I contributed samples from the Colombian Andes

Collaborators: Meredith Kelly (Dartmouth), Brenda Hall & Alice Doughty (Umaine), Kurt Rademaker (Texas A&M), Sergio Restrepo-Moreno (UNal, Medellín), Daniel Ruiz Carrascal (EAFIT, Medellín), Claire Todd (CSU, San Bernardino), Margaret Jackson (Trinity College Dublin), Joerg Schaefer & Gisela Winckler (Lamont-Doherty Earth Observatory)

Students/Postdocs: Peter Strand & Scott Braddock (UMaine), Santiago Noriega Londoñ (EAFIT), Matt Hegland & Matt Schmidt (Pacific Lutheran University), Peter Galloway (Dartmouth), Ezequiel De Jesùs Ferro-Palacios & Marvin Mosquera-Palacios (UNal)

Funded by grants from the Gary C. Comer Science & Education Foundation, the U.S. National Science Foundation (GLD grant 2022727,  P2C2 1003471), and the Columbia University Institute for Latin American Studies (ILAS).

Related Publications 

Herbert, J.N., Bromley, G.R., et al., 2025. Paleoclimatic implications of glacial fluctuations in the Sierra Nevada del Cocuy, northern Andes, Colombia, during the Lateglacial and Holocene. Quaternary Science Reviews 363, p.109458

Gorin, A.L., Shakun, J.D., Jones, A.G., Kennedy, T.M., Marcott, S.A., Goehring, B.M., Zoet, L.K., Jomelli, V., Bromley, G.R., et al., 2024. Recent tropical Andean glacier retreat is unprecedented in the Holocene. Science 385, 517-521.

Bromley, G.R.M., et al., 2016. A cosmogenic 10Be chronology for the local last glacial maximum and termination in the Cordillera Oriental, southern Peruvian Andes: Implications for the tropical role in global climate. Quat. Sci. Rev. 148, 54–67.  

Bromley, G.R.M., et al., 2011. Late Pleistocene snowline fluctuations at Nevado Coropuna (15S), southern Peruvian Andes. J. Quat. Sci. 26, 305-317.

Bromley, G.R.M., et al., 2011. Glacier fluctuations in the southern Peruvian Andes during the late-glacial period, constrained with cosmogenic 3He. J. Quat. Sci. 26, 37-46.

Bromley, G.R.M., et al., 2009. Relative timing of last glacial maximum and late glacial events in the tropical Andes. Quaternary Science Reviews 28, 2514-2526.

Glacial geologist maps clues to global climate change from the Andes Mountains (Medill School of Journalism)

Climate in the Peruvian Andes: From Early Humans to Modern Challenges (Columbia Climate School)