Terrestrial uptake due to cooling responsible for low atmospheric CO2 during the Little Ice Age
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Date
2016-03-07
Journal Title
Journal ISSN
Volume Title
Publisher
Antarctic Climate and Ecosystems Cooperative Research Centre
Abstract
Models of future carbon cycle-climate changes predict a large range in atmospheric CO2, mainly because of uncertainties in the response of the land carbon cycle to the future temperature increase. The Little Ice Age (LIA, 1500-1750 AD) CO2 decrease is the most significant pre-industrial atmospheric change over the last millennia and has been used to derive the climate sensitivity of the global carbon cycle (δ). While a recent study confirms that pre-industrial CO2 variations were caused by changes in land carbon stores, there are open questions about the size of the atmospheric LIA CO2 decrease reconstructed from ice cores, and about what caused the land to sequester CO2. To quantify the size of the LIA CO2 decrease, we have produced new CO2 measurements from DML ice, that support the DSS LIA CO2 decrease as a real atmospheric feature. To partition the contribution of ocean and land, we have measured the δ 13C-CO2, showing that the cause of the CO2 drop was uptake by the terrestrial biosphere. To identify whether the land uptake was caused by temperature, or by a decline in farming due to pandemics, we have simulated the effect of a temperature
perturbation on atmospheric Carbonyl Sulfide (COS). In agreement with the previously published positive COS anomaly, our results indicate that Global Primary Productivity (GPP) decreased during the LIA, ruling out the early anthropogenic land use change hypothesis as the dominant cause of increased terrestrial carbon storage. This allows us to obtain a new, more coherent estimation of δ in the range -10/-60 Pg of C K-1.
Description
Keywords
Carbon dioxide, Little Ice Age, Climatic change, Carbon cycle, Biosphere, Paleoclimatology
Citation
Rubino, M., Etheridge, D.M., Trudinger, C.M., Allison, C.E., Rayner P.J., Enting, I., Mulvaney, R., Steele, L.P., Langenfelds, R.L., Sturges, W.T., Curran, M.A.J. & Smith, A.M. (2016). Terrestrial uptake due to cooling responsible for low atmospheric CO2 during the Little Ice Age. Paper presented at IPICS 2016, International Partnerships in Ice Core Sciences, Second Open Science Conference, 7-11 March 2016, Hobart, Tasmania.