Pentti Pirinen

Large Impacts of Climatic Warming on Growth of Boreal Forests since 1960

Boreal forests are sensitive to climatic warming, because low temperatures hold back ecosystem processes, such as the mobilization of nitrogen in soils. A greening of the boreal landscape has been observed using remote sensing, and the seasonal amplitude of CO2 in the northern hemisphere has increased, indicating warming effects on ecosystem productivity. However, field observations on responses of ecosystem productivity have been lacking on a large sub-biome scale. Here we report a significant increase in the annual growth of boreal forests in Finland in response to climatic warming, especially since 1990. This finding is obtained by linking meteorological records and forest inventory data on an area between 60° and 70° northern latitude. An additional increase in growth has occurred in response to changes in other drivers, such as forest management, nitrogen deposition and/or CO2 concentration. A similar warming impact can be expected in the entire boreal zone, where warming takes place. Given the large size of the boreal biome – more than ten million km2– important climate feedbacks are at stake, such as the future carbon balance, transpiration and albedo.

New gridded daily climatology of Finland: Permutation‐based uncertainty estimates and temporal trends in climate

Long-term time series of key climate variables with a relevant spatiotemporal resolution are essential for environmental science. Moreover, such spatially continuous data, based on weather observations, are commonly used in, e.g., downscaling and bias correcting of climate model simulations. Here we conducted a comprehensive spatial interpolation scheme where seven climate variables (daily mean, maximum, and minimum surface air temperatures, daily precipitation sum, relative humidity, sea level air pressure, and snow depth) were interpolated over Finland at the spatial resolution of 10 × 10 km2. More precisely, (1) we produced daily gridded time series (FMI_ClimGrid) of the variables covering the period of 1961–2010, with a special focus on evaluation and permutation-based uncertainty estimates, and (2) we investigated temporal trends in the climate variables based on the gridded data. National climate station observations were supplemented by records from the surrounding countries, and kriging interpolation was applied to account for topography and water bodies. For daily precipitation sum and snow depth, a two-stage interpolation with a binary classifier was deployed for an accurate delineation of areas with no precipitation or snow. A robust cross-validation indicated a good agreement between the observed and interpolated values especially for the temperature variables and air pressure, although the effect of seasons was evident. Permutation-based analysis suggested increased uncertainty toward northern areas, thus identifying regions with suboptimal station density. Finally, several variables had a statistically significant trend indicating a clear but locally varying signal of climate change during the last five decades.

Corrosion of Reinforcement in Existing Concrete Façades

The most common degradation mechanism causing the need to repair concrete facades in Finland, is the corrosion of reinforcement due to carbonation and the small cover depths of the reinforcement. During the last almost 20 years the repair of concrete facades and balconies has been very active and this work has produced a great deal of information about the actual condition of those repaired buildings. This active condition assessment and repair work have produced an extensive and growing information base, which can be used, for example, for anticipating the upcoming repair need of concrete structures. For this purpose the data is gathered from 947 concrete buildings, which includes the distribution of different kinds of states of damage and the interdependence between the damage and other factors. The carbonation of concrete has widely advanced in the facades made in 1970s or earlier. The corrosion of reinforcement has been possible approximately last 20–30 years in those facades. Despite insufficient cover depths of concrete and far advanced carbonation of concrete, visually seen corrosion damage are relative rare. Corrosion damage appear mostly on facades, which get more rain. In Finland those are upper parts of southern and western facades.