Since the industrial revolution the concentration of atmospheric CO2 has increased. This potent greenhouse gas is already causing demonstrable climate change. Important insights into exactly how the climate will change in the future in response to increased greenhouse emissions can be gained from looking into the past to those time periods that were warmer than today.
1. What is the sensitivity of the climate system to CO2 forcing? – how hot will it get in the future?
2. What is the relationship between CO2, ice-volume and sea level? – how high will sea level rise as the major ice sheets melt in the future?
How do we do it?
We use cutting edge analytical techniques to measure the chemical and boron isotopic composition of the calcium carbonate shells of single celled organisms called foraminifera.
These animals lived in the ancient ocean and their shells now make up deep ocean sediments. Such sediments represent a continuous archive of ancient climate that stretches back continuously for up to 65 million years.
From the chemical and isotopic signals locked up in the shells of these animals we can reconstruct ocean pH (and hence atmospheric CO2 ), ice volume (and hence sea-level) and water temperature (and hence climate).
Hain, M.P., Foster, G.L., CHalk, T.B. (2018) Robust constraints on past climate forcing by CO2 from novel boron isotope proxy systematics, Paleoceanography and Paleoclimatology, 33, doi:10.1029/2018PA003362.
Foster, G.L. Hull, P., Lunt, D.J., Zachos, J.C. (2018) Placing our current "hyperthermal" in the context of rapid climate change in our geological. Philosophical Transactions of the Royal Society A, 376 20170086; doi: 10.1098/rsta.2017.0086
Sosdian, S.M., Greenop, R. Hain, M.P., Foster, G.L., Pearson. P.N. and Lear C.H. (2018) Constraining the evolution of Neogene ocean carbonate chemistry using the boron isotope pH proxy, Earth and Planetary Science Letters, 248, 362-376, doi:10.1016/j.epsl.2018.06.017. (Neogene data here and here, Pliocene data here)
Goodwin, P, Katavouta, A., Rouseenov, V.M., Foster, G.L., Rohling, E.J., Williams, R.G. (2018) Pathways to 1.5 and 2 oC warming based on observational and geological constraints, Nature Geoscience, 11, 102-107. doi:10.1038/s41561-017-0054-8
Chalk, T.B., Hain, M.P., Foster, G.L., Rohling, E.J., Sexton, P., Badger, M.P.S., Cherry, S., Hasenfratz, A., Haug, G., Jaccard, S., Martinez-Garcia, A., Palike, H., Pancost, R.D., Wilson, P.A. (2017) Causes of ice-age intensification across the Mid-Pleistocene Transition, Proceedings of the National Academy of Sciences, doi:10.1073/pnas.1702143114. Data here
Rohling, E. J., Marino, G., Foster, G. L., Goodwin, P. A., Von der Heydt, A. S., & Köhler, P. (2017). Comparing climate sensitivity, past and present. Annual Review of Marine Science. DOI: 10.1146/annurev-marine-121916-063242
Gutjahr, M., Ridgwell, A., Sexton, P. F., Anagnostou, E., Pearson, P. N., Pälike, H., ... Foster, G. L. (2017). Very large release of mostly volcanic carbon during the Paleocene-Eocene Thermal Maximum. Nature, 548, 573-577. DOI: 10.1038/nature23646. Supplementary Table S1, Supplementary Table S2. (a piece in The Conversation, on the radio, The Guardian).
Anagnostou, E., John, E.H., Edgar, K.M., Foster, G.L., Ridgwell, A., Inglis, G.N., Pancost, R.D., Lunt, D.J., Pearson, P.N. (2016) Changing atmospheric CO2 concentration was the primary driver of early Cenozoic climate. Nature, 533, 380-384, (doi:10.1038/nature17423)
Lunt, D.J., Farnsworth, A., Loptson, C., Foster, G.L., Markwick, P., O'Brien, C.L., Pancost, R.D., Robinson, S.A., Wrobel, N. (2016) Palaeogeographic controls on climate and proxy interpretation Climate of the Past 11, 5683-5725, doi:10.5194/cp-12-1181-2016
Inglis, Gordon N., Farnsworth, Alexander, Lunt, Daniel, Foster, Gavin L., Hollis, Christopher J., Pagani, Mark, Jardine, Phillip E., Pearson, Paul N., Markwick, Paul, Galsworthy, Amanda M. J., Raynham, Lauren, Taylor, Kyle. W. R. and Pancost, Richard D. (2015) Descent toward the Icehouse: Eocene sea surface cooling inferred from GDGT distributions. Paleoceanography, Early View (doi:10.1002/2014PA002723). click here for data.
Martínez-Botí, M.A., Foster, G.L., Chalk, T.B., Rohling, E.J., Sexton, P.F., Lunt, D.J., Pancost, R.D., Badger, M.P.S. and Schmidt, D.N. (2015) Plio-Pleistocene climate sensitivity evaluated using high-resolution CO2 records. Nature, 518, (7537), 49-54. (doi:10.1038/nature14145).