Fig 1.
Atlantic multidecadal oscillation (AMO) 1935–2013.
The AMO is the difference between the North Atlantic sea surface temperature (SST) and its trend line (slope equal to 0.0026 K yr−1 for 1856–2013). The annual measurements (black dotted line) are smoothed with a 13-year centered moving average filter (black solid line). The sinusoid (red dashed line) is a least squares fit to the moving average. The data are from the NOAA Earth System Research Laboratory (ESRL) AMO website, http://www.esrl.noaa.gov/psd/gcos_wgsp/Timeseries/AMO/.
Fig 2.
Pacific decadal oscillation (PDO) 1935–2013.
The PDO is the leading principal component of the North Pacific monthly sea surface temperature. The annual measurements (black dotted line) are smoothed with a 13-year centered moving average filter (black solid line). The sinusoid (red dashed line) is a least squares fit to the moving average. The data are from the University of Washington's PDO website, http://jisao.washington.edu/pdo/.
Fig 3.
Contiguous U.S. atmospheric temperature history 1902–2013.
The black dotted line is the annual atmospheric temperature time series (°C). The black solid line is the 13-year centered moving average. The 1935–2013 trend line is in red. The data are from the NCDC website, http://www.ncdc.noaa.gov/cag/time-series/us.
Fig 4.
Contiguous U.S. NCDC climate regions.
The figure shows the approximate locations of the climate regions and is intended only for illustrative purposes. An accurate map showing the exact locations of the climate regions is available at http://www.ncdc.noaa.gov/monitoring-references/maps/us-climate-regions.php.
Fig 5.
Measured and calculated contiguous U.S. temperature change.
The black solid line is the 13-year centered moving average atmospheric temperature (°C) from Fig 3 (truncated at 2007 because of the 13-year moving average). The red solid line is calculated by combining the monotonic and oscillatory (AMO) modes. The slope of the monotonic mode is 0.0089 K yr-1 and the amplitude of the oscillatory mode (AMO) is 0.75 K. The correlation between the measured and calculated curves is 0.98.
Fig 6.
Monotonic mode slopes and oscillatory mode amplitudes.
The slope of the monotonic mode (K yr-1×102) is taken from the trend line of each temperature time series and the oscillatory mode peak-to-peak amplitude (K) is that required to maximize the correlation of the temperature time series with the calculated curve of temperature vs. time. The climate mega-regions are shown by the colors.
Fig 7.
Correlations of the regional temperature time series with monotonic, oscillatory, and combined modes.
This bar chart shows the correlations of temperature time series for individual climate regions with the monotonic, oscillatory, and combined modes. The climate mega-regions are shown by the colors.
Fig 8.
Contributions of the monotonic and oscillatory modes to the 1980–2000 contiguous U.S. regional temperature increases.
The stacked bars show the contributions (K) of the monotonic and oscillatory modes for each climate region. The inset numbers are the percent of the total temperature increase attributable to the oscillatory mode. The climate mega-regions are shown by the colors.
Fig 9.
Contiguous U.S. climate mega-regions.
The three mega-regions are shown relative to the approximate locations of the NCDC contiguous U.S. climate regions. Within the NR&P climate region the location of the boundary separating the Northwestern and Central mega-regions is unclear and is, accordingly, left undrawn.