• Energy Research

<p><span>The forest expansion in the Northern Hemispheric extra-tropics during the deglaciation, i.e. the last some 22,000 years, starts earlier and occurs much faster in our model simulation using the MPI-ESM 1.2 than in the recently published synthesis of biome reconstructions by Cao et al. (2019). As a result, the simulated Northern Hemisphere maximum in forest cover is reached at 11ka in the model, whereas </span><span>the </span><span>forest </span><span>distribution</span><span> peaks substantially later (at 7ka in the spatial mean) in the reconstructions. The model-data mismatch is largest in Asia, particularly in Siberia and the East Asian monsoon margin. The simulated temperature trend is in line with pollen-independent temperature reconstructions for Asia. Since the simulated vegetation adapt to the </span><span>simulated </span><span>climate within decades, the temporal model-data mismatch with respect to the forest cover may indicate that pollen records are not in equilibrium with climate on multi-millennial timescales. </span></p><p><span>Our study has some far-reaching consequences. Pollen-based vegetation and climate reconstructions are commonly used to evaluate Earth System Models against past climate states, but to what extent the reconstructed vegetation is in equilibrium with the climate at the reconstructed time slice is still a matter of discussion. </span><span>Our results raise the question on which time-scales pollen-based reconstructions are reliable. </span><span>Although, it is so far not possible to identify the causes of the mismatch between our simulations and the reconstruction, we suggest critical re-assessment of pollen-based climate reconstructions.</span><span> Last, but not least, our</span><span> results may also point to a much slower response of forest biomes to current and future ongoing climate changes </span><span>than Earth System Models currently predict.</span></p><p> </p><p><span>References: </span></p><p>Cao, X., Tian, F., Dallmeyer, A. and Herzschuh, U.: Northern Hemisphere biome changes (>30°N) since 40 cal ka BP and their driving factors inferred from model-data comparisons, Quat. Sci. Rev., 220, 291–309, doi:10.1016/j.quascirev.2019.07.034, 2019.</p>

AbstractThe progress of science is tied to the standardization of measurements, instruments, and data. This is especially true in the Big Data age, where analyzing large data volumes critically hinges on the data being standardized. Accordingly, the lack of community‐sanctioned data standards in paleoclimatology has largely precluded the benefits of Big Data advances in the field. Building upon recent efforts to standardize the format and terminology of paleoclimate data, this article describes the Paleoclimate Community reporTing Standard (PaCTS), a crowdsourced reporting standard for such data. PaCTS captures which information should be included when reporting paleoclimate data, with the goal of maximizing the reuse value of paleoclimate data sets, particularly for synthesis work and comparison to climate model simulations. Initiated by the LinkedEarth project, the process to elicit a reporting standard involved an international workshop in 2016, various forms of digital community engagement over the next few years, and grassroots working groups. Participants in this process identified important properties across paleoclimate archives, in addition to the reporting of uncertainties and chronologies; they also identified archive‐specific properties and distinguished reporting standards for new versus legacy data sets. This work shows that at least 135 respondents overwhelmingly support a drastic increase in the amount of metadata accompanying paleoclimate data sets. Since such goals are at odds with present practices, we discuss a transparent path toward implementing or revising these recommendations in the near future, using both bottom‐up and top‐down approaches.