1,100 Year El Niño/Southern Oscillation (ENSO) Index Reconstruction Li, J.; Xie, S.-P.; Cook, E.R.; Huang, G.; D'Arrigo, R.D.; Liu, F.; Ma, J.; Zheng, X.-T. Li, J. Xie, S.-P. Cook, E.R. Huang, G. D'Arrigo, R.D. Liu, F. Ma, J. Zheng, X.-T. Atmospheric and Oceanic Circulation Patterns Reconstruction ENSO earth science/paleoclimate/climate reconstructions|tree ring (age,null,null,year Common Era,null,climate reconstructions|tree ring,null,null,N,null) earth science/paleoclimate/climate reconstructions|tree ring (El Nino Southern Oscillation Index,null,null,dimensionless,null,climate reconstructions|tree ring,smoothed,principal component analysis,N,smooth: 21 year running biweight) earth science/paleoclimate/climate reconstructions|tree ring (El Nino Southern Oscillation Index,null,null,dimensionless,null,climate reconstructions|tree ring,filtered,principal component analysis,N,filter: 9 year Lanczos highpass) earth science/paleoclimate/reconstructions (Tropical Pacific>LATITUDE >LONGITUDE ) The El Niño/Southern Oscillation (ENSO) is the dominant mode of interannual climate variability on Earth, alternating between anomalously warm (El Niño) and cold (La Niña) conditions in the tropical Pacific at intervals of 2-8 years. The amplitude of ENSO variability affects the occurrence and predictability of climate extremes around the world, but our ability to detect and predict changes in ENSO amplitude is limited by the fact that the instrumental record is too short to characterize its natural variability. Here we use the North American Drought Atlas - a database of drought reconstructions based on tree-ring records - to produce a continuous, annually resolved record of ENSO variability over the past 1,100 years. Our record is in broad agreement with independent, ENSO-sensitive proxy records in the Pacific and surrounding regions. Together, these records indicate that ENSO amplitude exhibits a quasi-regular cycle of 50-90 years that is closely coupled to the tropical Pacific mean state. Anomalously warm conditions in the eastern Pacific are associated with enhanced ENSO variability, consistent with model simulations. The quasi-periodic ENSO amplitude modulation reported here offers a key observational constraint for improving models and their prediction of ENSO behaviour linked to global warming. STUDY NOTES: An index of canonical ENSO variability for the past 1,100 years, derived from the first principal component of tree-ring based North America Drought Atlas (NADA). This index comprises interannual ENSO variability only, as a 9-year Lanczos highpass filter was applied on time series at each NADA grid point. A 21-year running biweight variance was calculated to measure changes in ENSO amplitude. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Li, J. Investigator : Xie, S.-P. Investigator : Cook, E.R. Investigator : Huang, G. Investigator : D'Arrigo, R.D. Investigator : Liu, F. Investigator : Ma, J. Investigator : Zheng, X.-T. 2011-05-16 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/11194 https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/enso-li2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/enso-li2011.xls https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/enso-li2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/enso-li2011.xls English https://www.ncdc.noaa.gov/paleo/study/11194 https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/enso-li2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/enso-li2011.xls Li, J., S.-P. Xie, E.R. Cook, G. Huang, R. D'Arrigo, F. Liu, J. Ma, and X.-T. Zheng. 2011. Interdecadal modulation of El Niño amplitude during the past millennium. Nature Climate Change, Vol. 1, Issue 2, pp. 114-118, May 2011 doi:10.1038/nclimate1086 START YEAR: 900 AD * END YEAR: 2002 AD 145 -20 -80 20