Transcript The Influence of Climate Modes on Changes in the Rate of Warming

The Influence of Climate Modes
on Changes in the Rate of
Warming of Global SST.
Semyon A. Grodsky, Thomas M. Smith, and James A. Carton
*Department of Atmospheric and Oceanic Science, University of Maryland,
College Park, MD 20742
*NOAA/NESDIS/STAR/SCSD, and CICS/ESSIC, University of Maryland,
College Park, College Park, Maryland
Annual ERSST.v3b anomaly from 1880-2009 from
60°S and 60°N.
Warm anomaly during 1940’s is due to relative increase of US
ship measurements (mainly engine room intake, ERI) relative to
UK ship measurements (primarily uninsulated bucket). ERI data is
biased warm.
A large discontinuity in the mid-twentieth century in observed global-mean surface
temperature, by Thompson,D.W.J., et al, Nature, 2008
Are alternative explanations of the
mid-century warming available?
Global SST anomaly from the 3 major SST reconstructions
Are alternative explanations of the
mid-century warming available?
Detrended global SST anomaly (degC)
Are alternative explanations of the
mid-century warming available?
Detrended global SST anomaly (degC) after removing the
ENSO impacts
Are alternative explanations of the
mid-century warming available?
Detrended global SST anomaly (degC) with the AMO index
overlain
Atlantic Multidecadal Oscillation Index (AMO)
Are alternative explanations of the midcentury warming available?
• Caveats
• AMO is based on the reconstructed SST
that includes possible bias due to ship
intake measurements
• But, if the bias is due to ship intake, the
Pacific (primarily area of US Navy during
WWII) should be biased warm while the
Atlantic (primarily area of UK Navy) should
be biased cold.
Spatial patterns and time series of the two leading EOFs of the
annually average de-trended non-ENSO anomalous SST
Conclusions
• Leading EOFs of detrended, non-ENSO
anomalous SST don’t resemble noisy patterns
typical of instrumental bias.
• Warm Pacific/cold Atlantic pattern, expected
from the mid 20th century observation shift
(switch in relative contribution of US/UK navy
observations), is not dominant.
• The two decadal SST modes, AMO and PDO,
explain about 60% of multidecadal changes in
the warming rate of global SST. The leading
mode, AMO, explains more than 50%.