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Supplemental Material forInternal Variability and Regional Climate Trends in an Observational Large
Ensemble
Karen A. McKinnon and Clara Deser
Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, Colorado© Copyright 2018 American Meteorological Society
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Figure S1: As in Fig. 1, but for JJA. The spatial pattern and temporal behavior of ENSO,
PDO, and AMO, and their surrogates. Modes 1 and 3 collectively explain ENSO and PDO,
while Mode 2 represents the AMO. First row: The sea surface temperature pattern associated with each mode. Second row: The time series of each mode (thick black line), andfour example surrogates (thin gray lines). Each surrogate is offset in the vertical by threeunits for visual clarity. Third row: The power spectra of each mode (thick black line) andits 95% confidence interval (light gray shading, outlined by thin black lines). The 95% rangeof the spectra for the surrogate time series is shown in the dark gray shading. See text fordetails.

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Figure S2: As in Fig. 2, but for JJA. Contribution of ENSO, PDO, and AMO to interannualDJF temperature variability estimated over 1921-2014. Modes 1 and 3 collectively explain
ENSO and PDO, while Mode 2 represents the AMO. Right column: The sensitivity of JJA
temperature to the three dominant SST modes (see Fig. S1) estimated via linear regression.
Stippling indicates an insignificant relationship using a False Discovery Rate of 10%; p-values
at each gridbox are estimated using a two-sided t-test. Left column: Power spectra forthree representative gridboxes, indicated by the location of the stars in the maps. In allcases, there is a clear separation of timescales between the inferred forced trend (red) andthe residual anomalies (teal).

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Figure S3: As in Fig. S2, but for precipitation.

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Figure S4: The ratio of interannual standard deviations of (top) temperature, (middle)
precipitation, and (bottom) sea level pressure for (left) DJF and (right) JJA from the NCAR
CESM1 Large Ensemble during 2015-2064 compared to 1965-2014. Interannual variability
is estimated after first removing the ensemble mean, and estimates are pooled across the40 ensemble members. Regions where there is an insignificant difference between the twoperiods are stippled. P-values at each gridbox are calculated using an F-test, and the fieldwide significance is based on a False Discovery Rate of 10%.

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Figure S5: Trend variability in the Observational Large Ensemble (OLENS), the NCAR
CESM1 Large Ensemble (LENS), and validation of the OLENS methodology for DJF sea
level pressure (SLP). (a) The standard deviation of 50-year (1965-2014) linear SLP trends
across the 1000 members of OLENS. (b) The standard deviation of 50-year linear SLP trends
across the 40 members of LENS. (c) The fractional error of the bootstrapping methodology,
estimated as the standard deviation of 50-year linear SLP trends in LENS minus the standard
deviation of 50-year linear SLP trends estimated from bootstrapping members of LENS,
normalized by the bootstrap-based estimate. (d) The fractional difference between LENSand OLENS-based estimates of the standard deviation of 50-year linear SLP trends, i.e.
(a - b)/(b). Stippling indicates locations where the difference is insignificant using a False
Discovery Rate of 10%; p-values are estimated at each gridbox as the probability that thedifference between LENS and the bootstrapped observations could occur from bootstrapping
individual members of LENS
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Figure S6: As in Fig. 4, but for JJA.

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Figure S7: As in Fig. 5 but for JJA.

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Figure S8: As in Fig. S5, but for JJA.

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Figure S9: Ensemble-mean linear trends from the NCAR CESM1 Large Ensemble (LENS)in JJA temperature (top row) and precipitation (bottom row) for the past (left column,1965-2014) and next (right column, 2015-2064) 50 years. Trends in SLP are indicated bycontours, with a contour interval of 1hPa/50 years, beginning with contours of ±0.5 hPa/50
years.

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Figure S10: Ensemble-mean linear trends from 37 CMIP5 models in DJF temperature (toprow) and precipitation (bottom row) for the past (left column, 1965-2014) and next (rightcolumn, 2015-2064) 50 years. Trends in SLP are indicated by contours, with a contour
interval of 1hPa/50 years, beginning with contours of ±0.5 hPa/50 years.

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Figure S11: As in Fig. S10 but for JJA.

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Figure S12: The regression maps of JJA temperature (top row), precipitation (bottom row),and SLP (contours) trends onto the first two normalized principal components of 50-year(1965-2014) JJA SLP trends across the Observational Large Ensemble. Contour interval
is 0.5hPa/50 years, and the zero contour is suppressed. SLP principal components arecalculated separately for each hemisphere (poleward of 10◦ ), but are shown on the same mapfor conciseness. The fraction of variance explained by the first two principal components is
17% and 12% in the Northern Hemisphere (41% and 12% in the Southern Hemisphere).

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Figure S13: Range of 50-year JJA temperature trends from the Observational Large Ensemble for the (top) past (1965-2014) and (bottom) future (2015-2064). The left and right panels
show the trend maps that accompany the 10th and 90th percentiles, respectively, of the NH
extratropical (30-90N) land-average trends. The 10th and 90th percentile JJA temperature
trends for the past (future) are 1.18◦ C/50 years and 1.53◦ C/50 years (3.39◦ C/50 years and3.74◦ C/50 years), respectively.

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Figure S14: As in Fig. S13, but for precipitation. The 10th and 90th percentile Northern Hemisphere extratropical land JJA precipitation trends for the past (future) are 0.26mm/mo/50 years and 2.56 mm/mo/50 years (2.27 mm/mo/50 years and 4.58 mm/mo/50years), respectively.

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Figure S15: The signal to noise ratio (SNR) in the Observational Large Ensemble for 50-year
trends in the past (left column, 1965-2014) and future (right column, 2015-2064) for JJA(first row) temperature and (second row) precipitation. SNR is estimated as the magnitudeof the ensemble mean 50-year trend normalized by the standard deviation of trends acrossthe ensemble.

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Figure S16: As in Fig. 12, but using the ensemble mean from 37 CMIP5 models as an
estimate of the forced trend.

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Figure S17: As in Fig. S16, but for JJA.

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