Living Blended Drought Atlas (LBDA) Version 2 - recalibrated reconstruction of United States Summer PMDI over the last 2000 years Gille, E.P.; Wahl, E.R.; Vose, R.S.; Cook, E.R. Gille, E.P. Wahl, E.R. Vose, R.S. Cook, E.R. Palmer Drought Index Reconstruction drought 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 (Palmer Modified Drought Index,null,null,dimensionless,Jun-Aug,climate reconstructions|tree ring,null,null,N,null) earth science/paleoclimate/climate reconstructions|tree ring (latitude,null,null,degree north,null,climate reconstructions|tree ring,null,null,N,null) earth science/paleoclimate/climate reconstructions|tree ring (longitude,null,null,degree east,null,climate reconstructions|tree ring,null,null,N,null) earth science/paleoclimate/reconstructions (Continental United States>LATITUDE >LONGITUDE ) IPCC Assessment Report 4 model projections suggest that the subtropical dry zones of the world will both dry and expand poleward in the future due to greenhouse warming. The US Southwest is particularly vulnerable in this regard and model projections indicate a progressive drying there out to the end of the 21st century. At the same time, the USA has been in a state of drought over much of the West for about 10 years now. While severe, this turn of the century drought has not yet clearly exceeded the severity of two exceptional droughts in the 20th century. So while the coincidence between the turn of the century drought and projected drying in the Southwest is cause for concern, it is premature to claim that the model projections are correct. At the same time, great new insights into past drought variability over North America have been made through the development of the North American Drought Atlas from tree rings. Analyses of this drought atlas have revealed past megadroughts of unprecedented duration in the West, largely in the Medieval period about 1000 years ago. A vastly improved Living Blended Drought Atlas (LBDA) for North America now under develop- ment reveals these megadroughts in far greater detail. The LBDA indicates the occurrence of the same Medieval megadroughts in the West and similar-scale megadroughts in the agriculturally and commercially important Mississippi Valley. Possible causes of these megadroughts and their implications for the future are discussed. STUDY NOTES: The half degree gridded Jun-Aug PMDI reconstructions from Cook et al. (2010) were recalibrated using the Global Historical Climatology Network (GHCN) 5km grid PMDI data. The 5km data were first upscaled to match the original half-degree grid. The recalibration was performed using a kernel density distribution mapping (KDDM) technique outlined in McGinnis et al. (2015) using an R-package provided by Seth McGinnis. We used a 50-year recalibration period covering 1929-1978 CE. We also adjusted each grid point's mean PMDI value for the recalibration period to be zero to avoid importing wet or dry bias into the recalibration. The recalibrated data set covers the continental United States just as the GHCN instrumental data does. Since instrumental data was used for 1979–2005 CE in the Cook dataset, recalibration applied only to the years 0–1978 CE. The 1979-2017 instrumental years were filled in using data from NCEI's GHCN 5km instrumental PMDI data. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Gille, E.P. Investigator : Wahl, E.R. Investigator : Vose, R.S. Investigator : Cook, E.R. 2017-08-03 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/22454 https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/nclimgrid_pmdi-2017.nc https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/images/ https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_rowyears_2017.txt https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_template.txt https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_cols_2017.txt https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_kddm_pmdi_2017.nc https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/nclimgrid_pmdi-2017.nc https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/images/ https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_rowyears_2017.txt https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_template.txt https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_cols_2017.txt https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_kddm_pmdi_2017.nc English https://www.ncdc.noaa.gov/paleo/study/22454 https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/nclimgrid_pmdi-2017.nc https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/images/ https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_rowyears_2017.txt https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_template.txt https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_pmdi_kddm_cols_2017.txt https://www1.ncdc.noaa.gov/pub/data/paleo/drought/LBDP-v2/lbda-v2_kddm_pmdi_2017.nc Cook, E.R., Seager, R., Heim, R.R., Vose, R.S., Herweijer, C., and Woodhouse, C.2010Megadroughts in North America: Placing IPCC projections of hydroclimatic change in a long-term paleoclimate contextJournal of Quaternary Science25148-6110.1002/jqs.1303 START YEAR: 0 AD * END YEAR: 2017 AD -124 24 -68 50