Northern Hemisphere Extratropical 1000 Year Temperature Reconstruction Christiansen, B.; Ljungqvist, F.C. Christiansen, B. Ljungqvist, F.C. Air Temperature Reconstruction temperature earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,null,degree Celsius,null,climate reconstructions,anomalized,regression analysis,N,simple linear regression) earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,null,degree Celsius,null,climate reconstructions,anomalized,null,N,Thin blue curves in Figs. 9 and 14 (upper panel)) earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,null,degree Celsius,null,climate reconstructions,anomalized|smoothed,null,N,Thick red curve in Fig. 14 (upper panel) 50 year smoothed plus bias) earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,percentile,degree Celsius,null,climate reconstructions,anomalized|smoothed,null,N,97.5th percentile; Dashed red curve in Fig. 14 (upper panel); 50 year smoothed) earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,null,degree Celsius,null,climate reconstructions,anomalized|smoothed,null,N,Thick blue curves in Figs. 9 and 14 (upper panel); 50 year smooth) earth science/paleoclimate/climate reconstructions (age,null,null,year Common Era,null,climate reconstructions,null,null,N,null) earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,percentile,degree Celsius,null,climate reconstructions,anomalized|smoothed,null,N,2.5th percentile; Dashed red curve in Fig. 14 (upper panel) 50 year smoothed) earth science/paleoclimate/reconstructions (Northern Hemisphere Extratropics>LATITUDE >LONGITUDE ) A new multiproxy reconstruction of the Northern Hemisphere extratropical mean temperature over the last millennium is presented. The reconstruction is performed with a novel method designed to avoid the underestimation of low-frequency variability that has been a general problem for regression-based reconstruction methods. The disadvantage of this method is an exaggerated high-frequency variability. The reconstruction is based on a set of 40 proxies of annual to decadal resolution that have been shown to relate to the local temperature. The new reconstruction shows a very cold Little Ice Age centered around the 17th century with a cold extremum (for 50-yr smoothing) of about 1.1 K below the temperature of the calibration period, AD 1880-1960. This cooling is about twice as large as corresponding numbers reported by most other reconstructions. In the beginning of the millennium the new reconstruction shows small anomalies in agreement with previous studies. However, the new temperature reconstruction decreases faster than previous reconstructions in the first 600 years of the millennium and has a stronger variability. The salient features of the new reconstruction are shown to be robust to changes in the calibration period, the source of the local temperatures, the spatial averaging procedure, and the screening process applied to the proxies. An ensemble pseudoproxy approach is applied to estimate the confidence intervals of the 50-yr smoothed reconstruction showing that the period AD 1500-1850 is significantly colder than the calibration period. STUDY NOTES: 1000 year temperature reconstruction for the Northern Hemisphere extratropical region (30°N-90°N) by the LOC method. The new LOC method reconstructs the local temperatures at the locations of the proxies. The reconstruction is based on one-dimensional linear regression with the local temperature as the independent variable and the proxy as the dependent variable. The local reconstructed temperatures are then averaged to get the NH mean temperature. While this method preserves low-frequency variability, the drawback is an exaggerated high-frequency variability. This adverse effect can be dampened by temporal averaging and decreases with the number of (independent) proxies. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Christiansen, B. Investigator : Ljungqvist, F.C. 2011-12-21 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/12355 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2011/christiansen2011.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2011/christiansen2011.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2011/christiansen2011.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2011/christiansen2011.txt English https://www.ncdc.noaa.gov/paleo/study/12355 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2011/christiansen2011.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2011/christiansen2011.txt Christiansen, B. and F.C. Ljungqvist. 2011. Reconstruction of the Extratropical NH Mean Temperature over the Last Millennium with a Method that Preserves Low-Frequency Variability. Journal of Climate, Vol. 24, Issue 23, pp. 6013-6034, December 2011. doi: http://dx.doi.org/10.1175/2011JCLI4145.1 START YEAR: 1000 AD * END YEAR: 2000 AD -180 30 180 90