Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - GC2.0 (Global Change 2.0: Unlocking the past for a clearer future)

Teaser

The project involves combining palaeoenvironmental and palaeoclimate observations with modelling in order to quantify terrestrial responses to past climate changes and thereby enhance our understanding of processes that affect the future.

Summary

The project involves combining palaeoenvironmental and palaeoclimate observations with modelling in order to quantify terrestrial responses to past climate changes and thereby enhance our understanding of processes that affect the future.

Work performed

A major effort has been spent on developing new palaeoenvironmental data sets, including pollen data of past vegetation changes and isotopic data that documents past changes in the hydrological cycle. The project has also led to the development of new approaches to translate palaeoenvironmental records into quantitative climate reconstructions. Given the importance of access to state-of-the-art palaeoclimate simulations to the project, considerable time has been spent of developing protocols for these experiments within the framework of the Palaeoclimate Modelling Intercomparison Project. Access to new data sets and new climate-model simulations has allowed analyses of key enigmas in the palaeoclimate record, most particularly mid-continental aridity and monsoon development. The vegetation and charcoal data sets have also been used to quantify important feedbacks to the climate system. Forward modelling is an important way of relating palaeoclimate simulations and palaeoenvironmental observations. The recognition that existing models of vegetation, tree growth and fire are inadequate for this purpose has led to involvement in data collection and analysis that is feeding into the development of new models of vegetation productivity, tree growth and fire. Progress in each of these areas is documented (see below) through publications, and in many cases the generation of new public-access data sets for use by the wider community. Finally, project members have been active in promoting and publicising the results from the project through workshops and presentations in international conferences.


Areas of progress
1. Development of protocols for palaeoclimate experiments (publications 1, 5, 16, 24)
2. Development of palaeoenvironmental data sets (publications 4, 6, 8, 13, 19; data sets 1, 3, 4, 5,)
3. Quantitative palaeoclimate reconstructions (publications 14, 21, 22, 26; data sets 6, 7, 8, 9)
4. Analyses of palaeoclimate (publications 2, 10)
5. Use of palaeoclimate data to quantify feedbacks (publications 7, 15)
6. Development of new model of productivity and tree growth, including modern trait analyses, for palaeoclimate applications (publications 9, 11, 17, 25; data set 2)
7. Development and application of tree growth model (publications 3, 18, 20)
8. Fire analyses (publications 12, 23)

Final results

Global Change 2.0: Unlocking the past for a clearer future

The project will exploit two important resources: databases of palaeoenvironmental and climatic information that can be interrogated to document changes in the past, and outputs from ensembles of climate-model simulations that can be used to explore the consequences of changes in climate forcing. Much of my work in the past 18 months has been dedicated to ensuring that these resources are available and expanded. Specifically:

1) I have contributed to the design and documentation of the palaeoclimate experiments that will be run by the Palaeoclimate Modelling Intercomparison Project (PMIP) as part of the suite of simulations being run by the Coupled Model Intercomparison Project (CMIP6) for the forthcoming Assessment Report of the Intergovernmeneal Panel on Climate Change (IPCC). This has lead to two publications: Kageyama et al., 2018, Geoscientific Model Development, and Otto-Bleisner et al., 2017, Geoscientific Model Development.
2) I have continued work on improving the coverage of vegetation reconstructions for past epochs, including compiling new data for the Eastern Mediterranean-Black Sea-Caspian Corridor (EMBSECBIO). This regional database has been published (Harrison, S.P. and Marinova, E., 2017. EMBSeCBIO modern pollen biomisation. University of Reading Dataset. http://dx.doi.org/10.17864/1947.109.), tests of the biomisation procedure have been successfully completed and a paper documenting these tests has been published (Marinova et al., 2017, Journal of Biogeography). I have also successfully reconstructed the African Pollen Database, which was not publicly accessible, and incorporated this within the global vegetation data set. The global vegetation reconstructions for the modern period have been used as one source of evidence for reconstructing potential natural vegetation (Hengl et al., 2018, PeerJPreprints 6:e26811v1) showing the value of these data sets to other communities. The machine-learning interpolation methodology used in this paper could be applied to provide palaeovegetation maps from site data, which would be useful for experiments to look at land-surface feedbacks to climate.
3) I have launched a new international initiative to compile isotope data globally from speleothem records. Speleothem isotope records provide a record of changes in climate (precipitation, temperature), which in some cases can provide information on climate variability with better than decadal resolution. SISAL (Speleothem Isotopes Synthesis and AnaLysis) has been officially recognized as a working group of the Past Global Changes (PAGES) programme and includes nearly 200 scientists worldwide. We have held two workshops so far, partially funded from my ERC grant, and have created a first version of the database with more than 100 records. The database has been archived (Atsawawaranunt, K., Harrison, S.P., Comas Bru, L., 2018. SISAL database Version 1.0. University of Reading Dataset. http://dx.doi.org/10.17864/1947.139) and will be made public on acceptance of the paper documenting this work (Atsawawanunt et al., 2018, Earth System Science Data Discussions). The SISAL group is now working on a series of analyses of these data, which will be presented at a third working group meeting to be held in Morocco in September 2018.
4) The ACER pollen database, which will be used in this project to reconstruct vegetation and climate changes through intervals of extremely rapid climate change during the last glacial period, has been published (Sánchez Goñi et al., 2017, Earth System Science Data).

The project is framed around four major challenges:
(1) How does vegetation respond to rapid climate change and what are the consequences of this response for climate?
(2) To what extent does increasing CO2 enhance tree growth or competitive fitness, and how does this translate into changes in ecosystems and ecosystem services?
(3) How does the terrestrial biosphere respond to c