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  • 1. Brandefelt, J.
    et al.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Naslund, J. -O
    Strandberg, Gustav
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Voelker, A. H. L.
    Wohlfarth, B.
    A coupled climate model simulation of Marine Isotope Stage 3 stadial climate2011Ingår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 7, nr 2, s. 649-670Artikel i tidskrift (Refereegranskat)
  • 2. Brigode, Pierre
    et al.
    Brissette, Francois
    Nicault, Antoine
    Perreault, Luc
    Kuentz, Anna
    SMHI, Samhälle och säkerhet.
    Mathevet, Thibault
    Gailhard, Joel
    Streamflow variability over the 1881-2011 period in northern Quebec: comparison of hydrological reconstructions based on tree rings and geopotential height field reanalysis2016Ingår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 12, nr 9, s. 1785-1804Artikel i tidskrift (Refereegranskat)
  • 3. Gaillard, M. -J
    et al.
    Sugita, S.
    Mazier, F.
    Trondman, A. -K
    Brostrom, A.
    Hickler, T.
    Kaplan, J. O.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Kokfelt, U.
    Kunes, P.
    Lemmen, C.
    Miller, P.
    Olofsson, J.
    Poska, A.
    Rundgren, M.
    Smith, B.
    Strandberg, Gustav
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Fyfe, R.
    Nielsen, A. B.
    Alenius, T.
    Balakauskas, L.
    Barnekow, L.
    Birks, H. J. B.
    Bjune, A.
    Bjorkman, L.
    Giesecke, T.
    Hjelle, K.
    Kalnina, L.
    Kangur, M.
    van der Knaap, W. O.
    Koff, T.
    Lageras, P.
    Latalowa, M.
    Leydet, M.
    Lechterbeck, J.
    Lindbladh, M.
    Odgaard, B.
    Peglar, S.
    Segerstrom, U.
    von Stedingk, H.
    Seppa, H.
    Holocene land-cover reconstructions for studies on land cover-climate feedbacks2010Ingår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 6, nr 4, s. 483-499Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The major objectives of this paper are: (1) to review the pros and cons of the scenarios of past anthropogenic land cover change (ALCC) developed during the last ten years, (2) to discuss issues related to pollen-based reconstruction of the past land-cover and introduce a new method, REVEALS (Regional Estimates of VEgetation Abundance from Large Sites), to infer long-term records of past land-cover from pollen data, (3) to present a new project (LANDCLIM: LAND cover - CLIMate interactions in NW Europe during the Holocene) currently underway, and show preliminary results of REVEALS reconstructions of the regional land-cover in the Czech Republic for five selected time windows of the Holocene, and (4) to discuss the implications and future directions in climate and vegetation/land-cover modeling, and in the assessment of the effects of human-induced changes in land-cover on the regional climate through altered feedbacks. The existing ALCC scenarios show large discrepancies between them, and few cover time periods older than AD 800. When these scenarios are used to assess the impact of human land-use on climate, contrasting results are obtained. It emphasizes the need for methods such as the REVEALS model-based land-cover reconstructions. They might help to fine-tune descriptions of past land-cover and lead to a better understanding of how long-term changes in ALCC might have influenced climate. The REVEALS model is demonstrated to provide better estimates of the regional vegetation/land-cover changes than the traditional use of pollen percentages. This will achieve a robust assessment of land cover at regional- to continental-spatial scale throughout the Holocene. We present maps of REVEALS estimates for the percentage cover of 10 plant functional types (PFTs) at 200 BP and 6000 BP, and of the two open-land PFTs 'grassland' and 'agricultural land' at five time-windows from 6000 BP to recent time. The LANDCLIM results are expected to provide crucial data to reassess ALCC estimates for a better understanding of the land suface-atmosphere interactions.

  • 4.
    Schimanke, Semjon
    et al.
    SMHI, Forskningsavdelningen, Oceanografi.
    Meier, Markus
    SMHI, Forskningsavdelningen, Oceanografi.
    Kjellström, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Strandberg, Gustav
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Hordoir, Robinson
    SMHI, Forskningsavdelningen, Oceanografi.
    The climate in the Baltic Sea region during the last millennium simulated with a regional climate model2012Ingår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 8, nr 5, s. 1419-1433Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Variability and long-term climate change in the Baltic Sea region is investigated for the pre-industrial period of the last millennium. For the first time dynamical down-scaling covering the complete millennium is conducted with a regional climate model in this area. As a result of changing external forcing conditions, the model simulation shows warm conditions in the first centuries followed by a gradual cooling until ca. 1700 before temperature increases in the last centuries. This long-term evolution, with a Medieval Climate Anomaly (MCA) and a Little Ice Age (LIA), is in broad agreement with proxy-based reconstructions. However, the timing of warm and cold events is not captured at all times. We show that the regional response to the global climate anomalies is to a strong degree modified by the large-scale circulation in the model. In particular, we find that a positive phase of the North Atlantic Oscillation (NAO) simulated during MCA contributes to enhancing winter temperatures and precipitation in the region while a negative NAO index in the LIA reduces them. In a second step, the regional ocean model (RCO-SCOBI) is used to investigate the impact of atmospheric changes onto the Baltic Sea for two 100 yr time slices representing the MCA and the LIA. Besides the warming of the Baltic Sea, the water becomes fresher at all levels during the MCA. This is induced by increased runoff and stronger westerly winds. Moreover, the oxygen concentrations in the deep layers are slightly reduced during the MCA. Additional sensitivity studies are conducted to investigate the impact of even higher temperatures and increased nutrient loads. The presented experiments suggest that changing nutrient loads may be more important determining oxygen depletion than changes in temperature or dynamic feedbacks.

  • 5.
    Strandberg, Gustav
    et al.
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Kjellstrom, Erik
    SMHI, Forskningsavdelningen, Klimatforskning - Rossby Centre.
    Poska, A.
    Wagner, S.
    Gaillard, M. -J
    Trondman, A. -K
    Mauri, A.
    Davis, B. A. S.
    Kaplan, J. O.
    Birks, H. J. B.
    Bjune, A. E.
    Fyfe, R.
    Giesecke, T.
    Kalnina, L.
    Kangur, M.
    van der Knaap, W. O.
    Kokfelt, U.
    Kunes, P.
    Latalowa, M.
    Marquer, L.
    Mazier, F.
    Nielsen, A. B.
    Smith, B.
    Seppa, H.
    Sugita, S.
    Regional climate model simulations for Europe at 6 and 0.2 k BP: sensitivity to changes in anthropogenic deforestation2014Ingår i: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 10, nr 2, s. 661-680Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study aims to evaluate the direct effects of anthropogenic deforestation on simulated climate at two contrasting periods in the Holocene, similar to 6 and similar to 0.2 k BP in Europe. We apply We apply the Rossby Centre regional climate model RCA3, a regional climate model with 50 km spatial resolution, for both time periods, considering three alternative descriptions of the past vegetation: (i) potential natural vegetation (V) simulated by the dynamic vegetation model LPJ-GUESS, (ii) potential vegetation with anthropogenic land use (deforestation) from the HYDE3.1 (History Database of the Global Environment) scenario (V + H3.1), and (iii) potential vegetation with anthropogenic land use from the KK10 scenario (V + KK10). The climate model results show that the simulated effects of deforestation depend on both local/regional climate and vegetation characteristics. At similar to 6 k BP the extent of simulated deforestation in Europe is generally small, but there are areas where deforestation is large enough to produce significant differences in summer temperatures of 0.5-1 degrees C. At similar to 0.2 k BP, extensive deforestation, particularly according to the KK10 model, leads to significant temperature differences in large parts of Europe in both winter and summer. In winter, deforestation leads to lower temperatures because of the differences in albedo between forested and unforested areas, particularly in the snow-covered regions. In summer, deforestation leads to higher temperatures in central and eastern Europe because evapotranspiration from unforested areas is lower than from forests. Summer evaporation is already limited in the southernmost parts of Europe under potential vegetation conditions and, therefore, cannot become much lower. Accordingly, the albedo effect dominates in southern Europe also in summer, which implies that deforestation causes a decrease in temperatures. Differences in summer temperature due to deforestation range from -1 degrees C in south-western Europe to +1 degrees C in eastern Europe. The choice of anthropogenic land-cover scenario has a significant influence on the simulated climate, but uncertainties in palaeoclimate proxy data for the two time periods do not allow for a definitive discrimination among climate model results.

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