The analysis of possible regional climate changes over Europe as simulated by ten regional climate models within the context of PRUDENCE requires a careful investigation of possible systematic biases in the models. The purpose of this paper is to identify how the main model systematic biases vary across the different models.Two fundamental aspects of model validation are addressed here: the ability to simulate i) the longterm (30 or 40 years) mean climate and ii) the inter-annual variability. The analysis concentrates on near-surface air temperature and precipitation over land and focuses mainly on winter and summer.In general, there is a warm bias with respect to the CRU data set in these extreme seasons and a tendency to cold biases in the transition seasons. In winter the typical spread (standard deviation) between the models is 1K. During summer there is generally a better agreement between observed and simulated values of inter-annual variability although there is a relatively clear signal that the modeled temperature variability is larger than suggested by observations, while precipitation variability is closer to observations. The areas with warm (cold) bias in winter generally exhibit wet (dry) biases, whereas the relationship is the reverse during summer (though much less clear, coupling warm (cold) biases with dry (wet) ones). When comparing the RCMs with their driving GCM, they generally reproduce the large-scale circulation of the GCM though in some cases there are substantial differences between regional biases in surface temperature and precipitation.4

The spruce bark beetle Ips typographus is one of the major insect pests of mature Norway spruce forests. In this study, a model describing the temperature-dependent thresholds for swarming activity and temperature requirement for development from egg to adult was driven by transient regional climate scenario data for Sweden, covering the period of 1961-2100 for three future climate change scenarios (SRES A2, A1B and B2). During the 20th century, the weather supported the production of one bark beetle generation per year, except in the north-western mountainous parts of Sweden where the climate conditions were too harsh. A warmer climate may sustain a viable population also in the mountainous part; however, the distributional range of I. typographus may be restricted by the migration speed of Norway spruce. Modelling suggests that an earlier timing of spring swarming and fulfilled development of the first generation will significantly increase the frequency of summer swarming. Model calculations suggest that the spruce bark beetle will be able to initiate a second generation in South Sweden during 50% of the years around the mid century. By the end of the century, when temperatures during the bark beetle activity period are projected to have increased by 2.4-3.8 1C, a second generation will be initiated in South Sweden in 63-81% of the years. The corresponding figures are 16-33% for Mid Sweden, and 1-6% for North Sweden. During the next decades, one to two generations per year are predicted in response to temperature, and the northern distribution limit for the second generation will vary. Our study addresses questions applicable to sustainable forest management, suggesting that adequate countermeasures require monitoring of regional differences in timing of swarming and development of I. typographus, and planning of control operations during summer periods with large populations of bark beetles.

No abstract

The boreal and boreo-nemoral forests in Europe, which occur in northern and northeastern Europe, are dominated by 2 coniferous species, Norway spruce Picea abies (L.) Karst. being economically the most important one. Forestry is of major economic importance in this region. Forestry planning and climate change scenarios are based on similar (long-term) timescales, i.e. between 70 and 120 yr. Within the EU project 'Modelling the Impact of Climate Extremes' (MICE), we have used 'present day ' runs (1961-1990) and future scenarios (2070-2100, emission scenarios A2 and B2 from the Special Report on Emissions Scenarios [SRES]) of the HadRM3 regional climate model to study and model direct and indirect effects of changing climate on Norway spruce in Sweden and northern Europe. According to our results, extreme climate events like spring temperature backlashes and summer drought will increase in frequency and duration. In combination with a raised mean temperature, climate extremes will negatively precondition trees (i.e. increase their susceptibility) to secondary damage through pests and pathogens. Decreased forest vitality also makes stands more susceptible to windthrow. Storm damage is discussed based on a 100 yr storm damage record for Sweden. Marginally increased frequencies and windspeeds of storms may cause disproportionate increases in windthrow. Increased economic hazards can be expected from a combination of the increased volumes of wind-thrown timber, and a greater likelihood of additional generations of spruce bark beetle Ips typographus (further encouraged by the increase in fallen timber), as a result of a changing climate with warmer summers.