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[1] Trends in soil temperature are important, but rarely reported, indicators of climate change. On the basis of the soil temperature data from 30 climate stations across Canada during 1958-2008, trends in soil temperatures at 5, 10, 20, 50, 100, and 150 cm depths were analyzed, together with atmospheric variables, such as air temperature, precipitation, and depth of snow on the ground, observed at the same locations. There was a significant positive trend with soil temperatures in spring and summer means, but not for the winter and annual means. A positive trend with time in soil temperature was detected at about two-thirds of the stations at all depths below 5 cm. A warming trend of 0.26-0.30°C/decade was consistently detected in spring (March-April-May) at all depths between 1958 and 2008. The warming trend in soil temperatures was associated with trends in air temperatures and snow cover depth over the same period. A significant decreasing trend in snow cover depth in winter and spring was associated with increasing air temperatures. The combined effects of the higher air temperature and reduced snow depth probably resulted in an enhanced increasing trend in spring soil temperatures, but no significant trends in winter soil temperatures. The thermal insulation by snow cover appeared to play an important role in the response of soil temperatures to climate change and must be accounted for in projecting future soil-related impacts of climate change.

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Climate change studies have oft en focused on individual forage species although legume-grass mixtures are predominant on dairy farms in northern areas of North America. We assessed the eff ect of (i) future climate conditions (temperature and precipitation) and elevated atmospheric CO 2 concentration ([CO 2 ]), separately and together, on yield of alfalfa (Medicago sativa L.) and timothy (Phleum pratense L.), grown alone or in mixture, and (ii) an adaptation strategy (timing and number of harvests) on future yield and nutritive value of an alfalfa-timothy mixture. Forage dry matter (DM) yield and nutritive value for two contrasting climate areas in eastern Canada were simulated with the Integrated Farm System Model over two future periods (2020-2049 and 2050-2079) using three climate models and two representative concentration pathways (RCP 4.5 and 8.5) of greenhouse gas emissions. Under projected future climate and without adaptation, annual forage yield of both species and the mixture increased in the colder area and decreased in the warmer area. In both areas, fi rst-cut yield increased due to faster growing degree-day accumulation, while regrowth yield decreased due to greater water and temperature stresses. Under elevated [CO 2 ], annual yield and the alfalfa percentage in the mixture increased. When combining climate change and elevated [CO 2 ], yield increased, except with the more drastic scenario (RCP 8.5, 2050(RCP 8.5, -2079 in the warmer area, and forage nutritive value was reduced. With adaptation, the mixture yield was increased from 5 to 35%, while nutritive value was generally maintained under all future scenarios, mostly because of additional cuts.

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A set of agroclimatic indices representing Canadian climatic conditions for field crop production are analyzed for long-term trends during 1895–2007. The indices are categorized for three crop types: cool season, warm season, and overwintering. Results indicate a significant lengthening of the growing season due to a significantly earlier start and a significantly later end of the growing season. Significant positive trends are also observed for effective growing degree-days and crop heat units at most locations across the country. The occurrence of extremely low temperatures has become less frequent during the nongrowing season, implying a more favorable climate for overwinter survival. In addition, the total numbers of cool days, frost days, and killing-frost days within a growing season have a decreasing trend. This means that crops may also be less vulnerable to cold stress and injury during the growing season. Extreme daily precipitation amounts and 10-day precipitation totals during the growing season have been increasing. Significant trends associated with increased availability of water during the growing season are identified by the standardized precipitation index and seasonal water deficits. The benefit of the increased precipitation may have been offset by an upward trend in evaporative demand; however, this would depend on the amount of growth and productivity resulting from increased actual evapotranspiration.

Abstract. Signatures of the North Atlantic Oscillation (NAO) are widely detected in climatic variability, particularly in the extratropical latitudes surrounding the North Atlantic Ocean. However, it is still controversial whether the NAO is the most important pattern of nonseasonal variability of atmospheric circulation related to precipitation over Europe. This paper is an attempt to contribute to this issue. The spatial modes of nonseasonal variability of monthly fields of mean sea level pressure (MSLP) over the northeastern Atlantic and western Europe and precipitation over Europe are investigated mainly by using principal component analysis. The relationships between the two fields are studied via canonical correlation analysis (CCA). The data sets used refer to the period from 1911 to 1990. The most important spatial mode of MSLP is the NAO pattern, its corresponding principal component being closely related to the NAO index. Interestingly however, the NAO pattern seems to be responsible only for the second empirical orthogonal function in precipitation, while the most important spatial mode of precipitation corresponds to the third EOF of MSLP (North Sea pattern). Furthermore, the second EOF of MSLP (Scandinavian pattern) is highly associated with the third EOF of precipitation. Significant pairs of canonical patterns between the MSLP and precipitation fields obtained from canonical correlation analysis are coherent with the conclusions above. These results can potentially be used to assess possible changes of precipitation over Europe due to increasing greenhouse gases based on the variability of MSLP simulated by general circulation models.