tions of the end-Paleocene (~55 Ma), mid to late Cretaceous (~120 to 90 Ma), end-Triassic (~200 Ma), and Late Paleozoic (~300 to 251.2 Ma)—all periods associated with the massive release of greenhouse gases to the atmosphere—reveal dramatic changes in oceanic conditions and terrestrial climates. These changes brought about extensive restructuring of marine and terrestrial ecosystems that in many cases involved mass extinctions. These deep-time records also reveal that some of the feedbacks in the climate system may be unique to warmer worlds—and thus are not archived in more recent paleoclimate records—and accordingly might be expected to become increasingly relevant with continued warming. In particular, long-term feedbacks that are typically active on millennial scales are likely to become important at the human timescale, leading to substantial and abrupt (years to centuries) climate modifications. Reconstructions of past climates show that civilization has evolved in an anomalously stable period unrepresentative of the climate system’s natural variability. Therefore, refining current understanding of climate dynamics (e.g., the range, rates, and magnitudes of feedbacks and change) during past periods of global warming, particularly times associated with epic deglaciations, is critical for assessing future risks. Improved understanding of climate dynamics will also aid efforts to mitigate the impact of continued warming on regional hydroclimates and water resources, ice sheet and sea level stability, and the health of marine and terrestrial ecosystems. Exciting research opportunities to help accomplish this task exist in the untapped potential of the deep-time geological record.

This report identifies a six-element research agenda designed to describe past climate variability and to better constrain how Earth’s climate system has responded to episodes of changing greenhouse gas levels. The knowledge gained by this scientific agenda will be important for addressing questions regarding the projected rise in atmospheric CO2 and the societal implications of this rise. The report also describes the research infrastructure necessary for successful implementation of the deep-time paleoclimatology agenda, as well as an education and outreach strategy designed to broaden our collective understanding of the unique perspective that the full range of the geological record provides for future climate change.

Improved Understanding of Climate Sensitivity and CO2-Climate Coupling

Determining the sensitivity of Earth’s mean surface temperature to increased greenhouse gas levels in the atmosphere is a key requirement for estimating the likely magnitude and effects of future climate change. The current understanding of climate sensitivity, defined on the basis of

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