Fennoscandia 1100 Year Summer Sunshine Reconstruction Gagen, M.; Zorita, E.; McCarroll, D.; Young, G.H.F.; Grudd, H.; Jalkanen, R.; Loader, N.J.; Robertson, I.; Kirchhefer, A.J. Gagen, M. Zorita, E. McCarroll, D. Young, G.H.F. Grudd, H. Jalkanen, R. Loader, N.J. Robertson, I. Kirchhefer, A.J. Other Reconstruction 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 (surface downwelling shortwave radiation,delta 13C,95% confidence interval lower bound,hour,Jul-Aug,climate reconstructions|tree ring,smoothed,null,N,hour per day; smoothed with 9-year centralized moving average) earth science/paleoclimate/climate reconstructions|tree ring (surface downwelling shortwave radiation,delta 13C,null,hour,Jul-Aug,climate reconstructions|tree ring,smoothed,null,N,hour per day; smoothed with 9-year centralized moving average) earth science/paleoclimate/climate reconstructions|tree ring (surface downwelling shortwave radiation,delta 13C,95% confidence interval upper bound,hour,Jul-Aug,climate reconstructions|tree ring,smoothed,null,N,hour per day; smoothed with 9-year centralized moving average) earth science/paleoclimate/climate reconstructions|tree ring (surface downwelling shortwave radiation,delta 13C,null,hour,Jul-Aug,climate reconstructions|tree ring,smoothed,null,N,hour per day; smoothed with 30-year running mean) earth science/paleoclimate/reconstructions (LaanilaSS>LATITUDE 68.5>LONGITUDE 27.5) Cloud cover is one of the most important factors controlling the radiation balance of the Earth. The response of cloud cover to increasing global temperatures represents the largest uncertainty in model estimates of future climate because the cloud response to temperature is not well constrained. Here we present the first regional reconstruction of summer sunshine over the past millennium, based on the stable carbon isotope ratios of pine tree rings from Fennoscandia. Comparison with the regional temperature evolution reveals the Little Ice Age (LIA) to have been sunny, with cloudy conditions in the warmest periods of the Medieval at this site. A negative shortwave cloud feedback is indicated at high latitude. A millennial climate simulation suggests that regionally low temperatures during the LIA were mostly maintained by a weaker greenhouse effect due to lower humidity. Simulations of future climate that display a negative shortwave cloud feedback for high-latitudes are consistent with our proxy interpretation. STUDY NOTES: Reconstruction of summer sunshine over the past 1100 years, based on the stable carbon isotope ratios of pine tree rings from Fennoscandia. Data are presented as 9-year smoothed estimate of July and August average daily sunshine hours at Laanila, Finland, 68°30'N, 27°30'E. Details on 9-yr Smoothing The sub-fossil chronology was built using eight cohorts of trees of increasing calendar age. The 5-year-pool method (Boettger et al., 2009) was used to target the multi-decadal and lower frequency climate information of interest without recourse to time consuming annual sampling. Blocks, each containing five rings, were offset by one year between each of five trees per cohort. Using this method, when each block value for each tree is averaged across each year, the final chronology approximates a 9-year centralized moving average and does not retain the inter-annual signal such that the series is produced by physical smoothing using the block cutting system. We supplemented this 5-year 'offset pooling' method with an additional step for checking the absolute d13C value at cohort joins to encourage low frequency signal retention. Where cohorts meet, the mean absolute d13C value was checked, for a short overlap period, via a series of 8 join-points. At each join-point a much larger number of trees (average n=16, Table SM1) were analyzed over a single 5-yr block. The offset between the raw d13C chronology and the 'true' mean at the join-points was small (average 0.1‰ with a standard deviation of 0.4‰). Details on calculation of error bars The total error on the chronology (Figure Supporting Material 2) represents the square root of the sum of 'raw' error (sigma1 the 95% confidence limit calculated from the average and standard deviation of 5 trees for each data point, in raw form, non join point corrected) and the 95% confidence limit on each join-point (sigma2). The total error thus was calculated as: Total error = sqrrt ((sigma1e2) + (sigma2e2)) NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Gagen, M. Investigator : Zorita, E. Investigator : McCarroll, D. Investigator : Young, G.H.F. Investigator : Grudd, H. Investigator : Jalkanen, R. Investigator : Loader, N.J. Investigator : Robertson, I. Investigator : Kirchhefer, A.J. 2011-10-14 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/12217 https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/europe/fennoscandia2011sunshine.xls https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/europe/fennoscandia2011sunshine.txt https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/europe/fennoscandia2011sunshine.xls https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/europe/fennoscandia2011sunshine.txt English https://www.ncdc.noaa.gov/paleo/study/12217 https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/europe/fennoscandia2011sunshine.xls https://www1.ncdc.noaa.gov/pub/data/paleo/treering/reconstructions/europe/fennoscandia2011sunshine.txt Gagen, M., E. Zorita, D. McCarroll, G.H.F. Young, H. Grudd, R. Jalkanen, N.J. Loader, I. Robertson, and A. Kirchhefer. 2011. Cloud response to summer temperatures in Fennoscandia over the last thousand years. Geophys. Res. Lett., 38, L05701, doi:10.1029/2010GL046216 START YEAR: 886 AD * END YEAR: 2001 AD 27.5 68.5 27.5 68.5