Article

Climate change between the mid and late Holocene in northern high latitudes – Part 2: Model-data comparisons

Climate of the Past (Impact Factor: 3.38). 09/2010; 6(5). DOI: 10.5194/cp-6-609-2010
Source: DOAJ

ABSTRACT

The climate response over northern high latitudes to the mid-Holocene orbital forcing has been investigated in three types of PMIP (Paleoclimate Modelling Intercomparison Project) simulations with different complexity of the modelled climate system. By first undertaking model-data comparison, an objective selection method has been applied to evaluate the capability of the climate models to reproduce the spatial response pattern seen in proxy data. The possible feedback mechanisms behind the climate response have been explored based on the selected model simulations. Subsequent model-model comparisons indicate the importance of including the different physical feedbacks in the climate models. The comparisons between the proxy-based reconstructions and the best fit selected simulations show that over the northern high latitudes, summer temperature change follows closely the insolation change and shows a common feature with strong warming over land and relatively weak warming over ocean at 6 ka compared to 0 ka. Furthermore, the sea-ice-albedo positive feedback enhances this response. The reconstructions of temperature show a stronger response to enhanced insolation in the annual mean temperature than winter and summer temperature. This is verified in the model simulations and the behaviour is attributed to the larger contribution from the large response in autumn. Despite a smaller insolation during winter at 6 ka, a pronounced warming centre is found over Barents Sea in winter in the simulations, which is also supported by the nearby northern Eurasian continental and Fennoscandian reconstructions. This indicates that in the Arctic region, the response of the ocean and the sea ice to the enhanced summer insolation is more important for the winter temperature than the synchronous decrease of the insolation.

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    • "Despite substantial inter-model uncertainty (Rogelj et al., 2012), great emphasis has been placed on detecting novel climates relative to current conditions that might pose substantial challenges for species and ecosystem adaptation (Williams et al., 2007; Beaumont et al., 2011). Similarly , several efforts have been undertaken to understand differences between the early 20th-century climate and the climates of the Quaternary period in general (Pickett et al., 2004; MacDonald et al., 2008a; Willis et al., 2010; Zhang et al., 2010). These climate reconstructions have been used to explain the responses of biota to climate variation in the past (Benito Garzón et al., 2007; Terry et al., 2011; Willis & MacDonald, 2011). "
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    ABSTRACT: To analyse global patterns of climate during the mid-Holocene and conduct comparisons with pre-industrial and projected future climates. In particular, to assess the exposure of terrestrial biomes and ecoregions to climate-related risks during the Holocene–Anthropocene transition starting at the pre-industrial period. Terrestrial ecosystems of the Earth. We calculated long-term climate differences (anomalies) between the mid-Holocene (6 ka cal bp, mH), pre-industrial conditions and projections for 2100 (middle-strength A1B scenario) using six global circulation models available for all periods. Climate differences were synthesized with multivariate statistics and average principal component loadings of temperature and precipitation differences (an estimate of climate-related risks) were calculated on 14 biomes and 766 ecoregions. Our results suggest that most of the Earth's biomes will probably undergo changes beyond the mH recorded levels of community turnover and range shifts because the magnitude of climate anomalies expected in the future are greater than observed during the mH. A few biomes, like the remnants of North American and Euro-Asian prairies, may experience only slightly greater degrees of climate change in the future as compared with the mH. In addition to recent studies that have identified equatorial regions as the most sensitive to future climate change, we find that boreal forest, tundra and vegetation of the Equatorial Andes could be at greatest risk, since these regions will be exposed to future climates that are well outside natural climate variation during the Holocene. The Holocene–Anthropocene climate transition, even for a middle-strength future climate change scenario, appears to be of greater magnitude and different from that between the mH and the pre-industrial period. As a consequence, community- and biome-level changes due to of expected climate change may be different in the future from those observed during the mH.
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    • "Changes in insolation have been shown in previous modelling studies to have an impact on the surface climate (see Braconnot et al., 2007a, 2007b). These impacts can also be seen in the proxy data evidence (for example see Zhang et al., 2010, which includes a model/proxy data comparison for Northern Hemisphere high latitudes). However, a limited number of palaeoclimate studies for the mid Holocene have sought to corroborate field evidence with model outputs in New Zealand, one of few locations in the Southern Hemisphere with abundant terrestrial proxy data (McGlone et al., 1993). "
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    • "with increasing global mean temperature (e.g., Wallace and Osborn, 2002), whereas the seasonal temperature cycle tends to be stronger in the MH than in the PI (Zhang et al., 2010). As mentioned earlier, the beach ridges found on the northeastern coast of Greenland indicates the presence of open water and sufficiently long fetch for waves to develop (Funder et al., 2011; Jakobsson et al., 2010). "
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    Full-text · Article · Apr 2013 · Climate of the Past
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