ENSO Atmospheric Teleconnections and Their Response to Greenhouse Gas Forcing

Abstract

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.

Causal Links on Interannual Timescale Between ENSO and the IOD in CMIP5 Future Simulations

“…Overall, the result shown here indicates a more likely significant ENSO teleconnection on tropical IO and the IOD, especially regarding the western part of tropical IO, during the 2006–2100 period. The weak ENSO teleconnection found in several models might be due to the change of mean atmospheric circulation caused by anthropogenic forcing (Yeh et al, ). Other study (Ham et al, ) found that the weakening of ENSO‐IOD connection in recent decades (i.e., the 2000s and 2010s) is related to changes of ENSO spatial patterns.…”

Pacific and Atlantic multidecadal variability relations to the El Niño events and their effects on the South American rainfall

“…Our results confirm Yeh et al . () findings on the EN events of the 1982–2016 period, which they classified as of the EP (CP) type before (after) 1998. Indeed, the 1982–1997 and 1998–2016 periods overlap, respectively, the CAMO/WPDO and WAMO/CPDO mean states.…”

ENSO's Changing Influence on Temperature, Precipitation, and Wildfire in a Warming Climate

“…While climate anomalies in North America of similar general character are common during La Niña, the intensity of these anomalies was again highly unusual. A wide range of processes can potentially alter observed anomalies during any individual event, and therefore, these episodes do not provide a definitive basis for attributing changes in the strength of ENSO or its teleconnections, a challenge that relates to both the evaluation of events in nature (e.g., Seager et al, ; Yeh et al, ) and models (Deser et al, ; Guilyardi et al, ). They do, however, raise questions regarding the role a warming climate may have had on both these and even more recent ENSO‐related extremes in California (Swain et al, ; Williams et al, , ; Yoon, Wang, Gillies, Hipps, et al, ) and other regions (Herrera & Ault, ; Wang, Huang, et al, ; Williams et al, ).…”