Focus 3 - Rationale and Goals


Humanity is currently carrying out a global-scale experiment in climate modification. By significantly and rapidly changing the forcing by greenhouse gases out of the envelope of late Quaternary conditions, we tested the response of the system. The consequences of such an experiment were the result of interactions between components of the Earth System. Therefore, we needed to learn about these interactions, in particular about the non-linear and threshold responses that may exist. The impacts of the experiment were felt as a result of regional changes in the pattern of precipitation and temperature. We therefore had an urgent need to understand how global-scale changes are imprinted in individual regions and why.

The past provides numerous examples in which changes in forcing at the global scale have occurred, and others where a redistribution of climate patterns appears to have occurred in the absence of global-scale forcing, either because of a change in the spatial and seasonal pattern of forcing, or because of internal changes in the system. We can use the past to diagnose the patterns of change that occur under different scenarios. More specifically, by investigating how changes in different components of the Earth System, and different regions, were related in the past, we can test and improve the process understanding required for predictive models. Additionally, we can investigate whether the system has exhibited rapid changes, and possibly threshold behavior.


The goals of this focus were addressed under four topics:

1. Variability of the Hydrological cycle

- To unravel the mechanisms causing variations in both the global and regional monsoon systems.

- To identify and understand teleconnections between global- and regional-scale monsoon variations and other components of the climate system.

- To disentangle the processes leading to shifts in the position of the ITCZ at interdecadal-to-millennial timescales.

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2. Rapid Climate Change

- Combine well-dated records of centennial to millennial-scale oceanographic and climatic change during the Holocene, the last glacial period, and previous interglacials using both bipolar and global comparisons of data with rigorous quality and age control.

- Use data compilations to assess hypotheses on the drivers and effects of past MOC changes to inform assessments of the possibility of such changes in the future and of their potential impacts.

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3. Interglacial Climate Variability

- Combine well-dated records of multiple glacial cycles over at least the ice core era (800 kyr), with the particular goal of understanding the spatial pattern and temporal trends within interglacials.

- Constrain the extent of changes in sea level and ice-sheet extent in past interglacials (in collaboration with Focus 1 and PALSEA2).

- Determine the variability at multi-annual to millennial timescales within warmer interglacials.

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4. Paleoperspectives on Ocean Biogeochemistry

- Compile proxy evidence for past global changes in the oceanic N and Fe cycles during rapid climate transitions and to unravel the mechanisms causing the variations.

- Quantify the response of marine organisms and ecosystems to acidification and their feedback on atmospheric CO2 using paleoceanographic records of historic acidification, as well as examples from high CO2 worlds in Earth history.

- Compile proxy data on marine productivity at glacial-interglacial and shorter timescales to assess the overall efficiency of the marine biological pump under different climatic boundary conditions.

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