Overview

Paleoclimate science aims to understand how Earth’s climate has varied over time by integrating a broad range of evidence from the natural and human world. Over the last decades, paleoclimate research has advanced understanding of the magnitudes, rates, and drivers of past climate variability on a range of timescales, providing a baseline and understanding for use in assessing current and future climate variability and change. These advances reflect progress in developing and understanding new proxies—indirect indicators of past climates preserved in climate archives—as well as in integrating these proxy records with numerical models.

The National Academies of Sciences, Engineering, and Medicine convened a workshop on June 21-23, 2021, to identify potential future paleoclimate research directions that will help advance the understanding of past, current, and future change in the Earth’s climate system. Using broad community input that was collected through an online questionnaire, workshop participants discussed gaps in current understanding of past climate variability and processes and new research strategies and technological capabilities that could practically be undertaken to effectively fill these knowledge gaps.

The Paleo Perspectives on Climate Change (P2C2) program of the National Science Foundation (NSF) has advanced proxy development, data-model comparisons, and synthesis work to understand Earth’s climate system in the past and facilitated interdisciplinary collaboration that has contributed to the growth of the field of paleoclimate research. Research questions that have driven the P2C2 program over the past decade remain relevant to informing understanding of current and future climate states. Workshop participants highlighted potential opportunities for the P2C2 program to be refined and broadened to advance understanding of past climate variability and processes that can inform the public and decision makers about the future.

Workshop discussions highlighted both emerging areas of research and relevant questions that the community is currently trying to address. Participants described an interest in shifting attention from global and annual spatiotemporal scales to more specific regional and seasonal scales, in part to make policy-relevant connections to the local impacts of climate change. Emerging scientific areas of interest included hydroclimate during past warm periods; connections between the biosphere, marine, and terrestrial ecosystems; and the carbon cycle. These research questions indicate the importance of also understanding large-scale processes in combination with the interest in shorter temporal and smaller spatial scales. Remaining questions

crucial to the understanding of the high latitudes and their feedbacks in the climate system include the nature of past ice-sheet extent and the dynamics of glacial-interglacial cycles. Focusing on obtaining data from areas historically devoid of data—for example, the Pacific, Southern Ocean, and Antarctica—offers opportunities to advance understanding of these questions. Workshop participants acknowledged that while the paleoclimate record holds no perfect, single analog for the future given the current and predicted rate and magnitude of change, there is value in studying both warm and cold climates in the past. To make paleoclimate research more relevant to the nexus of science and decision making, participants shared ideas focusing on human-relevant timescales, extreme events, and the connections between climate and life that could be placed in local contexts.

Tools and strategies to advance these new research directions were also an essential part of the workshop discussions. With respect to proxies, participants discussed better understanding of the types of information that proxies record, such as disentangling temperature and carbon dioxide (CO₂) records that may be recording interdependent information. In addition to developing new proxies and improving spatiotemporal coverage of records, participants described how devoting resources to modern process studies and ground truthing existing proxies could be useful. Sample and data archiving and sharing were also discussed, and the lack of community infrastructure was noted as a potential barrier to the accessibility of paleoclimate records. There was interest among some participants in putting resources behind building community databases that would serve as dynamic resources and facilitate synthesis work, instead of relying on the current volunteer-based model. Participants also looked toward new statistical tools, such as data assimilation, to use models and data together and at ways to use data-model comparisons to constrain uncertainty and inform future climate change.

Issues around belonging, accessibility, justice, equity, diversity, and inclusion were central to the workshop discussions on advancing paleoclimate research questions. In addition to strategies around skillset and equity-minded training, and tracking metrics for progress to enhance diversity and inclusion in the paleoclimate field (particularly for early career researchers), discussions also centered on knowledge coproduction. Some participants suggested that programmatic and financial support for efforts to engage and establish long-term relationships with local communities may be necessary in order to inform the development of new science questions.