North America and Europe Holocene Gridded Temperature Reconstructions Marsicek, J.P.; Shuman, B.N.; Bartlein, P.J.; Shafer, S.; Brewer, S. Marsicek, J.P. Shuman, B.N. Bartlein, P.J. Shafer, S. Brewer, S. Air Temperature Reconstruction earth science/paleoclimate/climate reconstructions|pollen (temperature,null,null,degree Celsius,coldest month,climate reconstructions|pollen,anomalized|averaged,null,N,averaged to century mean; anomalies relative to the mean of 1450-1950 AD) earth science/paleoclimate/climate reconstructions|pollen (temperature,null,null,degree Celsius,annual,climate reconstructions|pollen,anomalized|averaged,null,N,averaged to century mean; North America) earth science/paleoclimate/climate reconstructions|pollen (temperature,null,null,degree Celsius,annual,climate reconstructions|pollen,anomalized|averaged,null,N,averaged to century mean; Europe) earth science/paleoclimate/climate reconstructions|pollen (longitude,null,null,degree east,null,climate reconstructions|pollen,null,null,N,null) earth science/paleoclimate/climate reconstructions (age,null,null,year Common Era,null,climate reconstructions,null,null,N,null) earth science/paleoclimate/climate reconstructions|pollen (temperature,null,null,degree Celsius,annual,climate reconstructions|pollen,anomalized|averaged,null,N,averaged to century mean; Northern Hemisphere) earth science/paleoclimate/climate reconstructions|pollen (growing degree days,null,null,kelvin day,null,climate reconstructions|pollen,anomalized|averaged,null,N,averaged to century mean; growing degree days above a 5 degree Celsius base as anomalies relative to the mean of 1450-1950 AD) earth science/paleoclimate/climate reconstructions|pollen (latitude,null,null,degree north,null,climate reconstructions|pollen,null,null,N,null) earth science/paleoclimate/reconstructions (Europe>LATITUDE >LONGITUDE ) (North America>LATITUDE >LONGITUDE ) Cooling during most of the past two millennia has been widely recognized and has been inferred to be the dominant global temperature trend of the past 11,700 years (the Holocene epoch). However, long-term cooling has been difficult to reconcile with global forcing, and climate models consistently simulate long-term warming. The divergence between simulations and reconstructions emerges primarily for northern mid-latitudes, for which pronounced cooling has been inferred from marine and coastal records using multiple approaches. Here we show that temperatures reconstructed from sub-fossil pollen from 642 sites across North America and Europe closely match simulations, and that long-term warming, not cooling, defined the Holocene until around 2,000 years ago. The reconstructions indicate that evidence of long-term cooling was limited to North Atlantic records. Early Holocene temperatures on the continents were more than two degrees Celsius below those of the past two millennia, consistent with the simulated effects of remnant ice sheets in the climate model Community Climate System Model 3 (CCSM3). CCSM3 simulates increases in 'growing degree days' - a measure of the accumulated warmth above five degrees Celsius per year - of more than 300 kelvin days over the Holocene, consistent with inferences from the pollen data. It also simulates a decrease in mean summer temperatures of more than two degrees Celsius, which correlates with reconstructed marine trends and highlights the potential importance of the different subseasonal sensitivities of the records. Despite the differing trends, pollen- and marine-based reconstructions are correlated at millennial-to-centennial scales, probably in response to ice-sheet and meltwater dynamics, and to stochastic dynamics similar to the temperature variations produced by CCSM3. Although our results depend on a single source of palaeoclimatic data (pollen) and a single climate-model simulation, they reinforce the notion that climate models can adequately simulate climates for periods other than the present-day. They also demonstrate that amplified warming in recent decades increased temperatures above the mean of any century during the past 11,000 years. STUDY NOTES: Gridded, pollen-based climate reconstructions (mean annual temperature, growing degree days, and mean temperature of the coldest month) for North America and Europe over the Holocene. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Marsicek, J.P. Investigator : Shuman, B.N. Investigator : Bartlein, P.J. Investigator : Shafer, S. Investigator : Brewer, S. 2018-02-01 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/22992 https://www1.ncdc.noaa.gov/pub/data/paleo/reconstructions/marsicek2018/ https://www1.ncdc.noaa.gov/pub/data/paleo/reconstructions/marsicek2018/ English https://www.ncdc.noaa.gov/paleo/study/22992 https://www1.ncdc.noaa.gov/pub/data/paleo/reconstructions/marsicek2018/ Jeremiah Marsicek, Bryan N. Shuman, Patrick J. Bartlein, Sarah L. Shafer, Simon Brewer2018Reconciling divergent trends and millennial variations in Holocene temperaturesNature55492-9610.1038/nature25464https://www.nature.com/articles/nature25464 START YEAR: 11000 cal yr BP * END YEAR: 0 cal yr BP -170 25 40 70