Understanding Earth's Deep Past Lessons for Our Climate Future (2011) / Chapter Skim
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6 Conclusions and Recommendations
6 Conclusions and Recommendations
Pages 138-148
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From page 138... ...
In this context, the magnitude and rate of the present greenhouse gas increase place the climate system in what could be one of the most severe increases in radiative forcing of the global climate system in Earth history. To fully evaluate climate forcing feedbacks and tipping points that may characterize Earth's future, and to better understand climate change impacts and recovery, it is necessary to examine the records from past warm periods when there were similar magnitudes and rates of greenhouse gas forcing.
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From page 139... ...
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.
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From page 140... ...
Consequently, the mechanisms and feedbacks in the modern climate system that have controlled tropical and polar surface temperatures -- ultimately leading to the existing relatively high pole-to-equator thermal gradient -- may not operate in warmer worlds. A decreased latitudinal gradient in the future, which would almost certainly be associated with polar sea ice and continental ice sheet losses, would change atmospheric wind patterns and, in turn, ocean circulation -- all having potential detrimental effects through teleconnections (Hay, 2010)
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From page 141... ...
To fully exploit such deep-time archives will require radiometrically constrained and spatially resolved marine, paralic, and terrestrial records for both high and low latitudes. In addition, improved methods for deconvolving tempera ture and seawater δ18O from proxy records are needed, as well as targeted efforts to couple land-ice component models with complex global climate models that are capable of integrating the atmospheric hydrological cycle.
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From page 142... ...
Understanding Tipping Points and Abrupt Transitions to a Warmer World Studies of past climates and climate models show that Earth's climate system does not respond linearly to gradual CO2 forcing, but rather responds by abrupt change as it is driven across climatic thresholds. Modern climate is changing very rapidly, and there is a possibility that Earth will soon pass thresholds that will lead to even more rapid changes in Earth's environments.
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From page 143... ...
Despite exponential advances in the development of paleoclimate proxies over the past two decades, the precision and accuracy of existing organic and mineral paleotemperature and paleo-CO2 proxies are compromised by their calibrations to extant analogues, by incompletely understood biological and environmental controls on geochemical signatures, and/or by their sensitivity to postdepositional alteration. Moreover, paleobarometer proxies are limited to CO2, and there is a need for the existing very limited complement of proxies for estimating past terrestrial climatic conditions to be expanded and refined.
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From page 144... ...
A transectbased deep-time drilling program designed to identify, prioritize, drill, and sample key paleoclimate targets -- involving a substantially expanded continental drilling program and additional support for the existing sci entific ocean drilling program -- is a high priority for implementing the recommended research agenda. Although scientific ocean drilling has provided much of the basis for what is presently known about Neogene climate dynamics and ocean-climate linkages, there is still a pressing need for high-resolution sections that carry clear signals of orbital forcing in older parts of the record, particularly the Paleogene and Cretaceous.
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From page 145... ...
To that end, a markedly enhanced effort in deep-time paleoclimate modeling involving development of higher-resolution modules, improved parameterization of conditions relevant to future climate, and an emphasis on paleoclimate model intercomparisons and "next-generation" datamodel comparisons is a fundamental component of the proposed research agenda. An increase in model spatial resolution will be required to capture smaller-scale features and regional climate changes comparable in scale to the spatially resolved geological data that can be obtained through con tinental drilling and proxy development.
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From page 146... ...
Establishing the scientific collaboration, cross-disciplinary syntheses, widespread and open data exchange, cross-training of scientists and students, and dedicated and focused outreach activities required to address the research agenda described in this report will require the development of natural observatories for team-based studies of important paleoclimate time slices, incorporating climate and geochemical models; capabilities for the development, calibration, and testing of highly precise and accurate paleoclimate proxies; and the continued development of digital databases to store proxy data and facilitate multiproxy and record comparisons across all spatial and temporal scales. Such broad-based and interdisciplinary cultural and technological infrastructure will require acceptance and endorsement by both the scientific community and the funding agencies that support deep-time paleoclimatology and paleobiology-paleoecology studies.
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From page 147... ...
Immediate opportunities to illustrate "deep-time paleoclimatology in action" to the general public abound, whether the irreversible impact of past major climate changes on life, extreme glacia tions and catastrophic deglaciations, or the mysteries of the ocean. The scientific community needs to proactively pursue pathways to the public provided by various multimedia opportunities.
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From page 148... ...
It is the deep-time climate record that has revealed feedbacks in the climate system that are unique to warmer worlds -- and thus are not archived in more recent paleoclimate records -- and that might be expected to become increasingly relevant with continued warming. It is the deep-time record that has revealed the thresholds and tipping points in the climate sys tem that have led to past abrupt climate change, including amplified warming, substantial changes in continental hydro climate, catastrophic ice sheet collapse, and greatly accelerated sea level rise.
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