Northern Hemisphere Extratropical 2000 Year Temperature Reconstruction Christiansen, B.; Ljungqvist, F.C. Christiansen, B. Ljungqvist, F.C. Air Temperature Reconstruction Little Ice Age (LIA) Medieval Warm Period earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,percentile,degree Celsius,null,climate reconstructions,anomalized|smoothed,null,N,97.5th percentile; anomalized wrt 1880-1960 AD; dashe red curve in Fig 5; 50 year smooth) earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,null,degree Celsius,null,climate reconstructions,anomalized,null,N,anomalized wrt 1880-1960 AD; thin black curve in Fig 5) earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,null,degree Celsius,null,climate reconstructions,anomalized|smoothed,null,N,anomalized wrt 1880-1960 AD; thick red curve in Fig 5; 50 year smooth plus bias) earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,percentile,degree Celsius,null,climate reconstructions,anomalized|smoothed,null,N,2.5th percentile; anomalized wrt 1880-1960 AD; dashe red curve in Fig 5; 50 year smooth) earth science/paleoclimate/climate reconstructions (temperature,multiple proxies,null,degree Celsius,null,climate reconstructions,anomalized|smoothed,null,N,anomalized wrt 1880-1960 AD; thick black curve in Fig 5; 50 year smooth) earth science/paleoclimate/climate reconstructions (age,null,null,year Common Era,null,climate reconstructions,null,null,N,null) earth science/paleoclimate/reconstructions (Northern Hemisphere Extratropics>LATITUDE >LONGITUDE ) We present two new multi-proxy reconstructions of the extra-tropical Northern Hemisphere (30-90°N) mean temperature: a two-millennia long reconstruction reaching back to 1AD and a 500-yr long reconstruction reaching back to 1500 AD. The reconstructions are based on compilations of 32 and 91 proxies, respectively, of which only little more than half pass a screening procedure and are included in the actual reconstructions. The proxies are of different types and of different resolutions (annual, annual-to-decadal, and decadal) but all have previously been shown to relate to local or regional temperature. We use a reconstruction method, LOCal (LOC), that recently has been shown to confidently reproduce low-frequency variability. Confidence intervals are obtained by an ensemble pseudo-proxy method that both estimates the variance and the bias of the reconstructions. The two-millennia long reconstruction shows a well defined Medieval Warm Period, with a peak warming ca. 950-1050AD reaching 0.6°C relative to the reference period 1880-1960 AD. The 500-yr long reconstruction confirms previous results obtained with the LOC method applied to a smaller proxy compilation; in particular it shows the Little Ice Age cumulating in 1580-1720AD with a temperature minimum of -1.0°C below the reference period. The reconstructed local temperatures, the magnitude of which are subject to wide confidence intervals, show a rather geographically homogeneous Little Ice Age, while more geographical inhomogeneities are found for the Medieval Warm Period. Reconstructions based on different subsets of proxies show only small differences, suggesting that LOC reconstructs 50-yr smoothed extra-tropical NH mean temperatures well and that low-frequency noise in the proxies is a relatively small problem. STUDY NOTES: 2000 year and 500 year temperature reconstructions for the Northern Hemisphere extratropical region (30°N-90°N) by the LOC method. The 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 reconstruction method, LOC, is expected to catch the 50-year smoothed variability well, it exaggerates high-frequency variability. Hence, users are recommended to use the 50Yr-smoothed values for both the 2000-year long and 500-year long reconstructions. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Christiansen, B. Investigator : Ljungqvist, F.C. 2012-04-19 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/12902 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2012/christiansen2012.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2012/christiansen2012.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2012/christiansen2012.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2012/christiansen2012.txt English https://www.ncdc.noaa.gov/paleo/study/12902 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2012/christiansen2012.xls https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/christiansen2012/christiansen2012.txt Christiansen, B. and F.C. Ljungqvist. 2012. The extra-tropical Northern Hemisphere temperature in the last two millennia: reconstructions of low-frequency variability. Climate of the Past, Vol. 8, pp. 765-786. www.clim-past.net/8/765/2012/ doi:10.5194/cp-8-765-2012 START YEAR: 0 AD * END YEAR: 1973 AD -180 30 180 90