| 1. |
- Githumbi, Esther, et al.
(författare)
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Holocene quantitative pollen-based vegetation reconstructions in Europe for climate modelling: LandClim II
- 2019
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Konferensbidrag (refereegranskat)abstract
- Understanding land use and land cover (LULC) change through time is an important aspect when attempting to interpret human-environment interactions through time. Palaeoenvironmental techniques have been crucial in bridging this gap by providing information that has been used to estimate climate change, vegetation change, sea level change etc. through time using a variety of proxies. Producing quantitative land-cover reconstructions has been an aim and a challenge with several methods attempted during the decades. In this project, we use the REVEALS model has been tested and validated in several regions of the world.We use REVEALS-based quantitative reconstructions of vegetation change to investigate the biogeochemical and biogeophysical forcings of land-cover change on climate. In the first phase of this project, LandClim I, quantitative vegetation reconstructions were produced for Europe (Mediterranean area excluded) focusing on five time windows of the Holocene between 6ka BP and present. The results from a regional climate model showed that the impact of the reconstructed LULC between 6 ka and 0.2 ka BP via biogeophysical forcing varied geographically and seasonally. We present the REVEALS quantitative pollen-based vegetation reconstruction from the ongoing second phase of the project LandClim II “Quantification of the biogeophysical and biogeochemical forcings from anthropogenic deforestation on regional Holocene climate in Europe”. This reconstruction covers entire Europe and is transient over the Holocene with a time resolution of 500 years between 11.2 and 0.7ka BP, and 100 to 300 years from 0.7ka BP to modern time.
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| 2. |
- Kjellström, Erik, et al.
(författare)
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Simulated climate conditions in Europe during the Marine Isotope Stage 3 stadial
- 2010
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Ingår i: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 39:2, s. 436-456
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Tidskriftsartikel (refereegranskat)abstract
- State-of-the-art climate models were used to simulate climate conditions in Europe during Greenland Stadial (GS) 12 at 44 ka BP. The models employed for these simulations were: (i) a fully coupled atmosphere-ocean global climate model (AOGCM), and (ii) a regional atmospheric climate model (RCM) to dynamically downscale results from the global model for a more detailed investigation of European climate conditions. The vegetation was simulated off-line by a dynamic vegetation model forced by the climate from the RCM. The resulting vegetation was then compared with the a priori vegetation used in the first simulation. In a subsequent step, the RCM was rerun to yield a new climate more consistent with the simulated vegetation. Forcing conditions included orbital forcing, land-sea distribution, ice-sheet configuration, and atmospheric greenhouse gas concentrations representative for 44 ka BP. The results show a cold climate on the global scale, with global annual mean surface temperatures 5 degrees C colder than the modern climate. This is still significantly warmer than temperatures derived from the same model system for the Last Glacial Maximum (LGM). Regional, northern European climate is much colder than today, but still significantly warmer than during the LGM. Comparisons between the simulated climate and proxy-based sea-surface temperature reconstructions show that the results are in broad agreement, albeit with a possible cold bias in parts of the North Atlantic in summer. Given a prescribed restricted Marine Isotope Stage 3 ice-sheet configuration, with large ice-free regions in Sweden and Finland, the AOGCM and RCM model simulations produce a cold and dry climate in line with the restricted ice-sheet configuration during GS 12. The simulated temperature climate, with prescribed ice-free conditions in south-central Fennoscandia, is favourable for the development of permafrost, but does not allow local ice-sheet formation as all snow melts during summer.
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| 3. |
- Strandberg, Gustav, et al.
(författare)
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Regional climate model simulations for Europe at 6 and 0.2 k BP : sensitivity to changes in anthropogenic deforestation
- 2014
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Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 10:2, s. 661-680
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Tidskriftsartikel (refereegranskat)abstract
- 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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