Title: The space-time structure of climate variability

Authors: Thomas Laepple

Affiliations: Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung & MARUM–Center for Marine Environmental Sciences and Faculty of Geosciences, University of Bremen, Bremen, Germany.

Abstract: Since 2016, the PAGES CVAS (Climate Variability Across Scales) working group has been dedicated to unraveling climate variability across different spatial and temporal scales. While climate variability spans a wide range of scales, the decadal to millennial timescales are particularly significant. At these scales, natural variability overlaps with anthropogenic forcing, influencing our understanding of the industrial era and future climate projections. Paleoclimate records reveal strong variability at these longer timescales that cannot be fully explained by low-frequency orbital forcing. Further, many climate models appear to underestimate centennial to millennial variability, particularly on regional scales—suggesting potential deficiencies in internal variability, responses to external forcing, or inaccuracies in paleoclimate-based variability estimates. A deeper understanding of climate variability also emerges from its spatial structure. Observations and physical principles indicate an intrinsic link between temporal and spatial scales: fast variations, like weather, are regionally confined, whereas slower phenomena, such as glacial-interglacial cycles are globally coherent. While models suggest a strong reduction in the climate system’s degrees of freedom over longer timescales, many proxy records point to persistent regional variations even at centennial to millennial scales. However, proxies provide only indirect representations of climate variability and also contain non-climatic signals with distinct spatial and temporal structures. Understanding and accounting for these influences is crucial for accurately reconstructing the space-time structure of climate variability. In this presentation, I will discuss recent advances in understanding the origins and spatial-temporal structure of both proxy-based and climate variability, along with their implications for refining future climate projections.

Biography: Thomas Laepple is a Professor of Earth System Diagnostics at the University of Bremen and MARUM – Center for Marine Environmental Sciences, and a research group leader at the Alfred Wegener Institute, Helmholtz Center for Polar and Marine Research in Potsdam, Germany.
He received his Ph.D. in Physics in 2009. Following a research stay as Feodor Lynen Fellow at Harvard University, he led a Helmholtz Young Investigator research group at the Alfred Wegener Institute and was awarded a prestigious ERC Starting Grant in 2017. He is an active member of the PAGES CVAS (Climate Variability Across Scales) initiative, which he led from 2020 to 2023. His current research interest lies in the quantitative synthesis and explanation of paleoclimate data with a focus on sediment and ice-cores. By bridging the gap between geological data and climate models, his working group develops a quantitative approach to using paleoclimate observations to reconstruct climate variability and to constrain estimates of future climate change.