Oliver Elison Timm

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Introduction
Publications
I have research interests in two broad categories: Paleoclimate and impacts of future climate change on regional climate and environments.

I began studying past climate changes during my PhD using indirect climate records found in tree rings, ice cores and tropical corals. I analyzed these paleoclimate proxies to reconstruct the North Atlantic Oscillation variability covering the last 400 years. I have been involved in paleoclimate reconstructions with focus on the tropical climates including El Niño-Southern Oscillation (ENSO) and Indian Ocean SST variability.

Accurate quantitative assessment of climate variability during the pre-industrial centuries is crucial for understanding long-term climate changes in the next decades to centuries. Key questions that motivate my research are:

(1) How stable were the natural modes of variability during the pre-industrial times, and what is their natural range of variability?
(2) How can we identify and reconstruct modes of large-scale climate variability from individual and multiple proxy records?
(3) What were the drivers of past climate variations?

During my research at the International Pacific Research Center in Hawai‘i, I investigated the physical processes behind climate changes during glacial-interglacial cycles of the late Pleistocene- Holocene epoch. In particular, the Milankovitch theory of glacial cycles became the center of my research activities. For these time scales (of the order of 10,000-100,000 years), paleoclimate modelers frequently rely on Earth System Models of Intermediate Complexity (EMICs). EMICs are effective and comprehensive tools to analyze the response of the Earth’s climate system to external forcing and to identify primary feedback mechanisms in the climate system.

I apply and further develop the model LOVECLIM to study the evolution of the Northern Hemisphere ice sheets in response to orbital and greenhouse gas forcing. In my research, the cross-validation of model results and proxy data is an important component in order to test hypothesis on past climate changes. Among others, I have studied past changes in monsoon climates, changes in the Atlantic Meridional Overturning Circulation, and the linkage between the climates of Antarctica/Southern Ocean and the northern hemisphere.

Currently, my paleoclimate research is focusing on the dynamics of large continental ice-sheets in the Northern Hemisphere during the last glacial cycles. Central questions motivating this research are:

(1) What are the main external forcing factors for glacial inceptions and terminations?
(2) What feedbacks between ice-sheets, ocean and atmosphere play a crucial role during growth phases and termination phases of the glacial cycles?
(3) How sensitive is the Earth’s climate system in response to greenhouse gas forcing and orbitally-driven insolation changes?

Besides the paleoclimate research, I am interested in the regional aspects of projected future climate changes. While I was working in Hawai‘i, I centered my attention on the tropical Pacific and the Hawaiian Islands. My motivation for this research activity is on the one hand the scientific challenge to obtain more detailed and robust information about regional changes; on the other hand, I see in regional climate change studies a valuable contribution to an informed decision making process at stake-holders levels, with the opportunity to engage in transdisciplinary communications.

I am working on improved methods that will build capacities towards a combined statistical-dynamical downscaling approach, which can improve the confidence in high-resolution downscaled climate change scenarios.