Pliocene and Eocene provide best analogs for near-future climates

K. D. Burke, J. W. Williams, M. A. Chandler, A. M. Haywood, D. J. Lunt, and B. L. Otto-Bliesner
PNAS December 26, 2018 115 (52) 13288-13293; first published December 10, 2018 https://doi.org/10.1073/pnas.1809600115

  1. Edited by Noah S. Diffenbaugh, Stanford University, Stanford, CA, and accepted by Editorial Board Member Robert E. Dickinson November 6, 2018 (received for review June 29, 2018)

Article Figures & SI

Figures

  • Fig. 1.
    Fig. 1.

    Temperature trends for the past 65 Ma and potential geohistorical analogs for future climates. Six geohistorical states (red arrows) of the climate system are analyzed as potential analogs for future climates. For context, they are situated next to a multi-timescale time series of global mean annual temperatures for the last 65 Ma. Major patterns include a long-term cooling trend, periodic fluctuations driven by changes in the Earth’s orbit at periods of 104–105 y, and recent and projected warming trends. Temperature anomalies are relative to 1961–1990 global means and are composited from five proxy-based reconstructions, modern observations, and future temperature projections for four emissions pathways (Materials and Methods). Pal, Paleocene; Mio, Miocene; Oli, Oligocene.

  • Fig. 2.
    Fig. 2.

    Time series of the closest geohistorical climatic analogs for projected climates, 2020–2280 CE (MD). Colored lines indicate the proportion of terrestrial grid cells for each future decade with the closest climatic match to climates from six potential geohistorical climate analogs: Early Eocene, Mid-Pliocene, LIG, Mid-Holocene, preindustrial, and historical for RCP8.5 (A) and RCP4.5 (B). No LIG simulation from GISS was available at the time of analysis.

  • Fig. 3.
    Fig. 3.

    Projected geographic distribution of future climate analogs (RCP8.5). Future climate analogs for 2020, 2050, 2100, and 2200 CE according to the ensemble median. Geohistorical periods are rank ordered according to global mean annual temperature as follows: preindustrial, historical, Mid-Holocene, LIG, Pliocene, and Eocene, with no analog placed at the end due to the prevalence of no-analog climates in the warmest and wettest portion of climate space (Fig. 4). Hence, a projected future location matched to Pliocene, Eocene, and no analog in the three ESMs would be identified as Eocene in the ensemble median.

  • Fig. 4.
    Fig. 4.

    Projected future climate space by closest analog (RCP 8.5). (Upper) DJF vs. JJA temperature space. (Lower) DJF vs. JJA precipitation space. Each point represents a terrestrial grid location from the model ensemble for the specified decade in the RCP8.5 projection. Points are color coded according to the geohistorical climate from which their closest analog sources. Box-and-whisker plots show the data range, median, and first and third quartiles for two time periods: the specified decade (black) and 2020 CE for reference (gray).

Related Data

Data supplements

  • Supporting Information

    • Download Appendix (PDF)
    • Download Movie_S01 (GIF) - CCSM Climate Analog Animation (RCP8.5). This animation shows the spatial distribution of future climate analogs under RCP8.5 for CCSM. Each decade from 2020 to 2280 CE is shown, and locations are color-coded according to the reference geohistorical state from which their closest climatic analog was sourced.
    • Download Movie_S02 (GIF) - HadCM Climate Analog Animation (RCP8.5). This animation shows the spatial distribution of future climate analogs under RCP8.5 for HadCM. Each decade from 2020 to 2280 CE is shown, and locations are color-coded according to the reference geohistorical state from which their closest climatic analog was sourced.
    • Download Movie_S03 (GIF) - GISS Climate Analog Animation (RCP8.5). This animation shows the spatial distribution of future climate analogs under RCP8.5 for GISS. Each decade from 2020 to 2280 CE is shown, and locations are color-coded according to the reference geohistorical state from which their closest climatic analog was sourced. No simulation of the Last Interglacial was available for GISS at time of publication.
    • Download Movie_S04 (GIF) - CCSM Climate Analog Animation (RCP4.5). This animation shows the spatial distribution of future climate analogs under RCP4.5 for CCSM. Each decade from 2020 to 2280 CE is shown, and locations are color-coded according to the reference geohistorical state from which their closest climatic analog was sourced.
    • Download Movie_S05 (GIF) - HadCM Climate Analog Animation (RCP4.5). This animation shows the spatial distribution of future climate analogs under RCP4.5 for HadCM. Each decade from 2020 to 2280 CE is shown, and locations are color-coded according to the reference geohistorical state from which their closest climatic analog was sourced.
    • Download Movie_S06 (GIF) - GISS Climate Analog Animation (RCP4.5). This animation shows the spatial distribution of future climate analogs under RCP4.5 for GISS. Each decade from 2020 to 2280 CE is shown, and locations are color-coded according to the reference geohistorical state from which their closest climatic analog was sourced. No simulation of the Last Interglacial was available for GISS at time of publication.
    • Download Movie_S07 (GIF) - Median Climate Analog Animation (RCP8.5). This animation shows the spatial distribution of future climate analogs under RCP8.5 for the ensemble median. Each decade from 2020 to 2280 CE is shown, and locations are color-coded according to the reference geohistorical state from which their closest climatic analog was sourced.
    • Download Movie_S08 (GIF) - Median Climate Analog Animation (RCP4.5). This animation shows the spatial distribution of future climate analogs under RCP4.5 for the ensemble median. Each decade from 2020 to 2280 CE is shown, and locations are color-coded according to the reference geohistorical state from which their closest climatic analog was sourced.

Related Data

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Pliocene and Eocene provide best analogs for near-future climates
K. D. Burke, J. W. Williams, M. A. Chandler, A. M. Haywood, D. J. Lunt, B. L. Otto-Bliesner
Proceedings of the National Academy of Sciences Dec 2018, 115 (52) 13288-13293; DOI: 10.1073/pnas.1809600115
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