Expert Report

Understanding the Earth's Deep Past: Lessons for Our Climate Future (2011)

Each report is produced by a committee of experts selected by the Academy to address a particular statement of task and is subject to a rigorous, independent peer review; while the reports represent views of the committee, they also are endorsed by the Academy. Learn more on our expert consensus reports.

A better understanding of how Earth will respond to future climate change could be gained by looking tens of millions of years back into Earth's past, this National Research Council report finds. Without a reduction in emissions, by the end of this century atmospheric carbon dioxide is projected to increase to levels that Earth has not experienced for more than 30 million years. Critical insights to understanding how Earth's atmosphere, oceans, and ecosystems would function in this high carbon dioxide environment are contained in the records of warm periods and major climate transitions from Earth's geological past. This report assesses current knowledge on climate in Earth's deep past and provides a research agenda for an improved understanding of earth system processes during the transition to a warmer world.

Key Messages

  • Increases in atmospheric carbon dioxide levels have the potential to drive Earth towards a warmer climate state, characterized by much higher global temperatures and little or no ice at Earth's poles.
  • Insight into how Earth's climate and ecosystems will respond to increased atmospheric carbon dioxide levels lie in Earth's geological record. Data gathered from rocks could allow scientists to reconstruct warm periods and major climate transitions in Earth's ancient past. Although these past climate events are not exact analogues of the climate of the future, information about past warm climates -- and particularly abrupt global warming events -- would provide information on how Earth's processes, such as the circulation of the atmosphere and ocean, ice sheets, sea level, ocean acidification, and ecosystems, might operate under warm conditions.
  • Data from Earth's deep past could also yield information on the "tipping points" for climate change -- the threshold of greenhouse gas accumulation in the atmosphere at which abrupt climate change will occur.
  • This report sets out a high-priority research agenda that identifies six research initiatives to better understand the insights offered by Earth's deep-time record into the response of earth systems to potential future climate change. Research directions include gaining a better understanding of the sensitivity of climate to increased atmospheric carbon dioxide, how much sea-level will rise as the ice sheets melt, and the resilience of ecosystems to climate change.
  • Implementing the research agenda will require the development of infrastructure and tools. For example, efforts are needed to refine existing indicators of past climates, and to develop new sources of data. Interdisciplinary collaborations of scientists and climate modelers will be needed to produce better reconstructions of climate conditions in Earth's ancient past.