El Niño and Southern Oscillation (ENSO) is the most prominent year-to-year climate fluctuation on Earth, alternating between anomalously warm (El Niño) and cold (La Niña) sea surface temperature (SST) conditions in the tropical Pacific. ENSO exerts its impacts on remote regions of the globe through atmospheric teleconnections, affecting extreme weather events worldwide. However, these teleconnections are inherently nonlinear and sensitive to ENSO SST anomaly patterns and amplitudes. In addition, teleconnections are modulated by variability in the oceanic and atmopsheric mean state outside the tropics and by land and sea ice extent. The character of ENSO as well as the ocean mean state have changed since the 1990s, which might be due to either natural variability or anthropogenic forcing, or their combined influences. This has resulted in changes in ENSO atmospheric teleconnections in terms of precipitation and temperature in various parts of the globe. In addition, changes in ENSO teleconnection patterns have affected their predictability and the statistics of extreme events. However, the short observational record does not allow us to clearly distinguish which changes are robust and which are not. Climate models suggest that ENSO teleconnections will change because the mean atmospheric circulation will change due to anthropogenic forcing in the 21st century, which is independent of whether ENSO properties change or not. However, future ENSO teleconnection changes do not currently show strong intermodel agreement from region to region, highlighting the importance of identifying factors that affect uncertainty in future model projections.
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We acknowledge the World Climate Research Programme’s Working Group on Coupled Modeling, which is respon sible for CMIP, and we thank the climate modeling groups for producing and making available their model outputs. The ERSST.v4 data set is from https:// www.ncdc.noaa.gov/data-access/mari-neocean-data/extended-reconstructed-sea-surface-temperature-ersst-v4 and the CPC Merged Analysis of Precipitation (CMAP) version is from https://www.esrl.noaa.gov/psd/data/ gridded/data.cmap.html. The NCEP and NCAR global reanalysis atmospheric variables can also be obtained from Earth System Research Laboratory (http://www.errl.noaa.gov/psd/data/ gridded/data.ncep.reanlaysis.html). The OLR data set is obtained from https:// www.esrl.noaa.gov/psd/map/clim/olr. shtml. S. W. Y. is supported by the Korea Meteorological Administration Research and Development Program under grant KMIPA2015-2112. Wenju Cai is supported by Earth System and Climate Change Hub of the Australia National Environmental Science Programme, and Centre for Southern Hemisphere Oceans Research, an international collaboration between CSIRO and Qingdao National Laboratory for Marine Sciences and Technology. B. Dewitte acknowledges supports from FONDECYT (1151185) and from LEFE-GMMC. Dietmar Dommenget is supported by ARC Centre of Excellence for Climate System Science (CE110001028). This is PMEL contribution 4735.
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