Identifying New Community-Driven Science Themes for NSF's Support of Paleoclimate Research Proceedings of a Workshop (2021) / Chapter Skim
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Understanding Past Climate Forcings and Sensitivity
Understanding Past Climate Forcings and Sensitivity
Pages 11-24
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From page 11... ...
During this workshop session, participants were asked to consider the drivers of past climate change with a focus on the knowns and the unknowns of climate forcings. The session featured panelists who spoke to various forcings of climate variability, including greenhouse gas, volcanic and aerosol, paleogeographic, and orbital forcings.
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From page 12... ...
disagreements, developing a more uniform proxy theory in some cases, and utilizing detailed databases like paleo-CO2 to conduct sensitivity studies and reconstructions from the same locations to compare different proxy records. There are also large data gaps in the Cenozoic record for CO2, and it could be useful to develop data from multiple proxies during the long-term transitions between major climate shifts.
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From page 13... ...
making it challenging to characterize their global distribution over time using proxy records. Similarly, for past climates, knowing the aerosol radiative forcing is
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Workshop participants discussed the importance of particle size distribution and composition for quantifying aerosol forcing, and suggested integrating modern observations, modeling, and assimilation of proxy data. Participants in the breakout session described how better constraints on the quantity and composition of aerosols emitted to the atmosphere during volcanic eruptions, as well as constraints on the timing and forcing of marine and terrestrial eruption events, could be useful.
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From page 15... ...
Volcanic eruptions, a climate forcing, can release large amounts of sulphur dioxide into the atmosphere, and in the upper atmosphere, oxidation can produce sulfuric acid aerosols that can cool the climate for several years. Oxygen isotopes in volcanic tephra preserved in the geologic record can be used to investigate the influence of super volcanic eruptions on the ozone layer (Martin and Bindeman, 2009)
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Orbital Forcing In the orbital forcing breakout discussion moderated by Lorraine Lisiecki, University of California, Santa Barbara, and Zhengyu Liu, Ohio State University, participants explained how orbital forcing can be leveraged to better understand climate feedbacks and identify thresholds and tipping points because the forcing is known, eliminating one source of uncertainty. Remaining research questions include understanding the signatures of orbital forcing, both the global and regional impacts, and the seasonal and spatial variations.
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From page 17... ...
This technique can be applied to paleoclimate records in order to develop global, three-dimensional reconstructions of past climates (e.g., Steiger et al., 2013; Valler et al., 2020)
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RECONSTRUCTING GLOBAL CLIMATE CHANGE AND CLIMATE SENSITIVITY This session shifted focus from understanding climate forcings to assessing the impacts of climate change on a global scale. The session included a panel and breakout discussions on the knowns and unknowns of reconstructing global climate change and climate sensitivity, including connections to policy.
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From page 19... ...
As examples, predictions of sea-level rise and global temperatures are being assessed by models that have been constrained by past climate. Paleoclimate can provide external constraints that reduce the spread of uncertainty across models and can directly impact future projections and future policy through work on climate sensitivities.
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From page 20... ...
There is a lack of land sediment records that would serve as counterparts to marine records in order to understand climate sensitivity and land-sea contrasts. Discussions in the climate sensitivity breakout session, moderated by Cristi Proistosescu, University of Illinois, and Dan Lunt, University of Bristol, focused on a need to quantify proxy uncertainties when translating localized records to global quantities used to characterize climate sensitivity, and participants suggested data assimilation as one approach forward.
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From page 21... ...
. In the ocean temperatures breakout session, moderated by Aradhna Tripati, University of California, Los Angeles, participants discussed how multi-proxy approaches and proxy intercomparisons can be used to identify a robust temperature signal, necessary to understand thermal history and equilibrium climate sensitivity.
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From page 22... ...
While much of this work has been used to understand the climate system during the past millennium, there is an opportunity to use these tools to look father back in time. Participants in the climate sensitivity breakout session discussed how more simulations before the historical record can be used to constrain climate models and climate sensitivities.
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From page 23... ...
. Blue bars indicate when there are well-developed ice sheets (solid lines)
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