NSF’s P2C2 program has played a pivotal role in advancing paleoclimate research for over a decade. The workshop underscored the relevance of the current P2C2 solicitation (Box 1)—for example, in the frequency of such themes as past warm periods, abrupt change, and data-model comparisons, highlighted in the current solicitation. There is still more to be learned about the past climate system from the current themes in light of new analytical tools and modeling capabilities, advanced over the past decade, in part because of the P2C2 program. Rather than an entirely new reimagining of these science themes, workshop participants offered feedback on ways the solicitation could be refined and broadened to be as inclusive as possible of the highly interdisciplinary scientific community the program has already fostered.
Participants highlighted the interest of the community in translating the global emphasis of paleoclimate research into regional connections. The attention to regional scales is motivated by the interest in making policy connections to explore regional vulnerabilities to climate change—for example, to understand extreme events, such as drought and wildfires. A focus on regional scales would involve more records at different resolutions to elucidate these connections. In addition, participants suggested targeting questions at the interface of climate and life to link paleoclimate research to the life-support system that society cares about and needs. Compared to what the community has been focused on in the past decade, workshop participants discussed moving away from focusing on the Atlantic basin, expanding understanding of the deep ocean beyond AMOC, and examining other glacial-interglacial cycles beyond the LGM. With respect to modes of variability, monsoons came up more frequently than ENSO. While participants focused less attention on climate sensitivity, there was more energy around understanding the nature of climate forcings—for example, while aerosol forcing is the least understood, there may be great promise to gain understanding about present forcing from preindustrial aerosols.
Hydroclimate, particularly during past warm periods, emerged as a robust new theme that participants were interested in exploring. Connections between the atmosphere and biosphere and ecosystem processes were also new themes that were repeatedly raised throughout the workshop. From the marine perspective, there was interest in better understanding paleoproductivity and incorporating marine biogeochemical models into paleoclimate work, as well as improving reconstructions of vegetation cover and the representation of terrestrial ecosystems in models. Relatedly, with
respect to the carbon cycle, while researchers are able to reconstruct concentrations of atmospheric CO2, participants stressed that there remain unanswered questions about carbon sources and sinks in the past, including as part of the methane cycle. In order to advance these research questions, taking a broader perspective to understand large-scale processes would also be critical.
Participants paid much attention to the ways the paleoclimate community can develop geologic models for a no-analog future, leveraging data from the past to better understand, for example, fires, permafrost thaw, and carbon release in a warming climate. However, some important regions and processes remain under-studied, they pointed out, including the Pacific and Southern Oceans. There was also discussion around focusing on the Antarctic and Southern Ocean processes, including questions about ocean heat and carbon storage. Also discussed was the leveraging of information from warmer intervals and targeting intervals (e.g., beyond the last 3 million years) for focused community efforts on data collection and modeling to fill in dynamical gaps that limit the utility of models of future climate states. Additionally, with respect to the cryosphere, participants described a desire for more attention towards understanding the nonlinear responses of ice sheets, past ice-sheet extent, interactions between the solid earth and ice sheets, and mechanistic models for glacial-interglacial cycles. Interest in better understanding past extreme events in order to inform present and future climate and communicate with the public and decision makers was also a repeated theme.
Proxies were a central part of workshop discussions. Many participants recognized that there is a need to improve systematic and mechanistic understanding of proxies, including the detailed biological grounding of proxies needed to make robust interpretations of the past. Many questions were raised about how well proxies are understood and what processes are being imprinted in paleoclimate archives. For example, the chemistry of calcite shells of benthic foraminifera, thought to be reliable temperature proxies, may be recording circulation changes and not temperature; calcite proxies are affected by kinetic affects. Given this uncertainty, participants discussed the importance of modern process studies, ground truthing for proxies, and using high-fidelity records to inform studies deeper in time. To advance many research avenues, participants discussed the potential utility of developing new proxies and calibrating these proxies, particularly with respect to examining the influence of seasonal bias. The participants’ discussions suggested the community does not think that the current P2C2 solicitation explicitly accommodates proxy development, calibration, or work to better understanding proxies.
In addition to proxies, participants discussed other types of tools that may be necessary to advance new research directions. There was a lot of discussion
around data, and participants shared thoughts on FAIR [findable, accessible, interoperable, reusable] data principles, and the importance of putting dedicated resources towards building community databases that are dynamic for current and future data and sample archiving. Building and maintaining databases would not only be important for combining and sharing paleoclimate data, but also for enhancing community efforts to do synthesis work including data intercomparisons and sensitivity analyses. Over the past 10 years, advances in data-model comparisons have allowed for quantitative evaluations of how data inform models, how models inform data, and how to blend the two through statistical methods such as data assimilation. Moving forward, some members of the paleoclimate science community are instead asking: What can be done with model-data comparisons to constrain future uncertainty and inform future climate change? Participants emphasized the importance of a hierarchy of models—including those of higher resolution used to explore regional changes and those of lower resolution that incorporate more processes and simulate longer time scales—to advance understanding of the magnitudes, rates, and drivers of past climate change on a range of time-scales. There was also a lot of discussion around data assimilation, but to make advancements, spatial and temporal gaps would likely need to be addressed, and well as the understanding of model and data priors.
In order to facilitate better paleoclimate research, issues of belonging, accessibility, justice, equity, diversity, and inclusion came up frequently throughout the workshop, as well as during the asynchronous session. In particular, there was a great deal of discussion around knowledge coproduction, in which part of the scientific endeavor is developed in collaboration with local communities. Many participants recognized the importance of reaching out to communities early in the process of developing research questions, as well as the need for sustained outreach over long periods of time to build relationships, and dedicated resources to support these efforts. It would be beneficial if P2C2 could help facilitate knowledge coproduction rather than simply stipulating that it should be done. Participants also suggested that trainings in data analysis and modeling could help to attract and retain a diverse workforce and early career researchers and provide skills applicable outside of academia.
The enthusiastic participation of the scientific community during the workshop indicated there are a rich set of unanswered research questions and ways that the paleoclimate community can contribute to understanding of past and future climate change. Paleoclimate research is a part of the broader field of climate science, exemplified by the way IPCC AR6 integrates knowledge gained through paleoclimate research about the climate system throughout the landmark report. NSF’s P2C2 program has facilitated and supported critical
advances in understanding of the Earth system in the past and has informed projections about the climate system in the future. Moving forward, many of the current P2C2 science themes remain relevant, and there is an opportunity for the program to expand, bridging the scales of large-scale synthesis and individual records, both of which will help to continue scientific advances.