Rajmund Przybylak

Long-term temperature trends and variability on Spitsbergen: the extended Svalbard Airport temperature series, 1898-2012

One of the few long instrumental records available for the Arctic is the Svalbard Airport composite series that hitherto began in 1911, with observations made on Spitsbergen, the largest island in the Svalbard Archipelago. This record has now been extended to 1898 with the inclusion of observations made by hunting and scientific expeditions. Temperature has been observed almost continuously in Svalbard since 1898, although at different sites. It has therefore been possible to create one composite series for Svalbard Airport covering the period 1898–2012, and this valuable new record is presented here. The series reveals large temperature variability on Spitsbergen, with the early 20th century warming as one striking feature: an abrupt change from the cold 1910s to the local maxima of the 1930s and 1950s. With the inclusion of the new data it is possible to show that the 1910s were colder than the years at the start of the series. From the 1960s, temperatures have increased, so the present temperature level is significantly higher than at any earlier period in the instrumental history. For the entire period, and for all seasons, there are positive, statistically significant trends. Regarding the annual mean, the total trend is 2.6°C/century, whereas the largest trend is in spring, at 3.9°C/century. In Europe, it is the Svalbard Archipelago that has experienced the greatest temperature increase during the latest three decades. The composite series may be downloaded from the home page of the Norwegian Meteorological Institute and should be used with reference to the present article.

Temporal and spatial variation of surface air temperature over the period of instrumental observations in the Arctic

A detailed analysis of the spatial and temporal changes in mean seasonal and annual surface air temperatures over the period of instrumental observations in the Arctic is presented. In addition, the role of atmospheric circulation in controlling the instrumental and decadal-scale changes of air temperature in the Arctic is investigated. Mean monthly temperature and temperature anomalies data from 37 Arctic, 7 sub-Arctic and 30 grid-boxes were used for analysis. The presented analysis shows that the observed variations in air temperature in the real Arctic (defined on the basis of climatic as opposed to other criteria, e.g. astronomical or botanical) are in many aspects not consistent with the projected climatic changes computed by climatic models for the enhanced greenhouse effect. The highest temperatures since the beginning of instrumental observation occurred clearly in the 1930s and can be attributed to changes in atmospheric circulation. The second phase of contemporary global warming (after 1975) is, at most, weakly marked in the Arctic. For example, the mean rate of warming for the period 1991–1995 was 2–3 times lower in the Arctic than the global average. Temperature levels observed in Greenland in the last 10–20 years are similar to those observed in the 19th century. Increases of temperature in the Arctic are more significant in the warm half-year than in the cold half-year. This seasonal pattern in temperature change confirms the view that positive feedback mechanisms (e.g. sea-ice–albedo–temperature) as yet play only a small role in enhancing temperature in the Arctic. Hypotheses are presented to explain the lack of warming in the Arctic after 1975. It is shown that in some parts of the Arctic atmospheric circulation changes, in particular in the cold half-year, can explain up to 10–50% of the temperature variance. For Arctic temperature, the most important factor is a change in the atmospheric circulation over the North Atlantic. The influence of atmospheric circulation change over the Pacific (both in the northern and in the tropical parts) is significantly lower. Copyright

Recent air-temperature changes in the Arctic

Abstract A detailed analysis of the spatial and temporal changes in mean seasonal and annual surface air temperature (SAT) in the Arctic is presented mainly for the period 1951–2005. Mean seasonal and annual homogenized and complete series of SAT from up to 35 Arctic stations were used in the analysis. The focus in this paper is on the 11 years 1995–2005, a period which saw dramatic warming in the Arctic (>1˚C for annual values in relation to the 1951–90 mean). An abrupt rise in SAT occurred in the mid-1990s and was most pronounced in autumn and winter (>2˚C). The greatest warming in the period 1995–2005 occurred in the Pacific and Canadian regions (>1˚C), while the lowest was in the Siberian region (0.82˚C). This period has been the warmest since at least the 17th century. In particular, 2005 was an exceptionally warm year (>2˚C in relation to the 1951–90 mean) and was warmer than 1938, the warmest year in the 20th century. The seasonal and annual trends of the areally averaged Arctic SAT for the periods 1936–2005, 1951–2005 and 1976–2005 are positive, with the exception of winter and autumn for the first period. The majority of trends calculated for the last two periods are statistically significant. While there are varying opinions about the forces driving the present warming, it seems likely that the marked rise in SAT in the mid-1990s (mainly from 1994 to 1995) was caused by (i) a set of natural factors, (ii) non-linear effects of greenhouse-gas loading, or (iii) the combined effect of these two groups of factors.

Diurnal temperature range in the Arctic and its relation to hemispheric and Arctic circulation patterns

The changes of atmospheric circulation patterns in the Northern Hemisphere and in the Arctic for the period 1939–1990 were investigated. For this purpose, the seasonal and annual frequencies of occurrence of W, E and C macrotypes according to the Vangengeim–Girs typology and groups of synoptic processes in the Arctic (A, B, W, G, D and K) according to the Dydina classification have been computed. Spatial and seasonal patterns of the mean diurnal temperature range (DTR) in the Arctic are presented, based on the data from 33 Arctic stations for the period 1951–1990. The relationships between the DTR in the Arctic and the atmospheric circulation changes in the Northern Hemisphere and in the Arctic have been investigated. The seasonal mean DTR for each macrotype of circulation and group of circulation was calculated using daily data from ten Arctic stations for the period 1951–1990. These stations represent all climatic regions and subregions identified by the authors of Atlas Arktiki (1985. Glavnoye Upravlenye Geodeziy i Kartografiy, Moskva, p. 204). In addition, the correlation coefficients between DTR in the Arctic and both the North Atlantic Oscillation Index (NAO) and the Zonal Index (ZI) have been computed. Statistically significant changes of atmospheric circulation in the Northern Hemisphere (mainly in low and moderate latitudes) since the mid-1970s, which are also reported by other researchers, have been confirmed. In the Arctic, the atmospheric circulation has also undergone changes in recent decades; however, these changes are significantly smaller. Both the annual and the seasonal mean DTR values have been found to be the highest in the centre of the southernmost parts of the Canadian and Russian Arctic and the lowest in the Norwegian Arctic. Based on the seasonal means, four types of annual course of the DTR in the Arctic have been identified. The results pertaining to the relationship between DTR and atmospheric circulation provide some evidence that, in recent decades, both the large-scale changes of the atmospheric circulation in the Northern Hemisphere and its changes in the Arctic have led to the damping of the cool half-year DTR in the Arctic. Copyright

Tree rings of Scots pine (Pinus sylvestris L.) as a source of information about past climate in northern Poland

Scots pine (Pinus sylvestris) is a very common tree in Polish forests, and therefore was widely used as timber. A relatively large amount of available wood allowed a long-term chronology to be built up and used as a source of information about past climate. The analysis of reconstructed indexed values of mean temperature in 51-year moving intervals allowed the recognition of the coldest periods in the years 1207–1346, 1383–1425, 1455–1482, 1533–1574, 1627–1646, and 1694–1785. The analysis of extreme wide and narrow rings forms a complementary method of examining climatic data within tree rings. The tree ring widths, early wood and late wood widths of 16 samples were assessed during the period 1581–1676. The most apparent effect is noted in the dry summer of 1616. According to previous research and our findings, temperature from February to March seems to be one of the most stable climatic factors which influenced pine growth in Poland. Correlation coefficients in the calibration and validation procedure gave promising results for temperature reconstruction from the pine chronology.

Spatial and Temporal Changes in Extreme Air Temperatures in the Arctic Over the Period 1951–1990

A detailed analysis of the spatial and temporal changes in mean seasonal and annual daily maximum (Tmax) and minimum (Tmin) air temperatures and diurnal temperature range (DTR) in the Arctic over the period 1951‐1990 is presented. This analysis is preceded by a description of the spatial distributions of the mean seasonal and annual 40-year extreme temperatures (i.e. Tmax and Tmin). The rate of decrease of the mean Arctic Tmin is about twice as weak as the rate for Tmax in the period 1951‐1990. As a result, a decrease in DTR is observed. Not all areas of the Arctic, however, show such tendency, e.g. large parts of the Canadian Arctic do not. The increases in DTR here are more common in summer than in winter. The decrease in DTR is related partly to increases in cloud cover, especially in the warm half-year when solar radiation is present in the Arctic. On the contrary, in the cool half-year (mainly during polar night) the day-to-day changes of temperature, governed at this time by very variable atmospheric circulation, have a greater impact than the cloudiness. The increase in variability of Tmax and Tmin has not occurred in the most recent decades. No evidence of any greenhouse warming in the Arctic over the period 1951‐1990 is seen. Most of the Tmax and Tmin trends are not statistically significant. 1997 by the Royal Meteorological Society, Int. J. Climatol. 17: 615‐634, 1997

Climate Change in Poland in the Past Centuries and its Relationship to European Climate: Evidence from Reconstructions and Coupled Climate Models

We investigate the winter temperature and precipitation evolution over Poland over the last half millennium in comparison with the European average in reconstructions/instrumental data and in the ECHO-G and HadCM3 models and discuss the physical processes behind those variations. Results indicate very good agreement between European land and Polish winter temperatures in reconstructions and in the models. Colder winter conditions were found within the ‘Little Ice Age’ and temperatures at the turn of the twenty first century are very likely the warmest in the context of the past. The strong agreement between Polish winter temperature and European mean conditions is of major interest since some of the longest European proxy information stem from Poland and therefore can improve European temperature reconstructions significantly. Precipitation results indicate that reconstructions over Poland agree well with those of the rest of Europe, though the agreement is poorer between the reconstruction and the models. The role of the large-scale atmospheric circulation dynamics/forcing connected with the observed Polish winter temperature/precipitation changes is investigated in the reconstructions and in the model world. The most important atmospheric circulation pattern for winter temperature variability is the North Atlantic Oscillation (NAO). The Scandinavian (SCAND) and to a lesser degree also the NAO and East Atlantic/Western Russia (EA/WRUS) are of relevance for winter precipitation variations in Poland. Canonical Correlation Analysis (CCA) results show that the leading circulation modes responsible for dry/wet and warm/cold Polish winter conditions are in good agreement in the reconstructions and models. These results suggest that the models are able to reproduce the links in instrumental and proxy data and also that the large- to regional-scale relationships are robust during the last centuries. The stability of the large- to regional-scale links is relevant for downscaling approaches and also for palaeoclimate reconstructions.

Air temperature variations and gradients along the coast and fjords of western Spitsbergen

Daily temperature measurements from six meteorological stations along the coast and fjords of western Spitsbergen have been digitized and quality controlled in a Norwegian, Russian and Polish collaboration. Complete daily data series have been reconstructed back to 1948 for all of the stations. One of the stations monthly temperature series has previously been extended back to 1898 and is included in this study. The long-term series show large temperature variability on western Spitsbergen with colder periods in the 1910s and 1960s and warmer periods in the 1930s, 1950s and in the 21st century. The most recent years are the warmest ones in the instrumental records. There is a positive and statistically significant trend in the annual times series for all of the stations; however, the strongest warming is seen in winter and spring. For the period 1979–2015, the linear trends range from 1.0 to 1.3°C/decade for the annual series and from 2.0 to 2.3°C/decade in winter. Threshold statistics demonstrate a decrease in the number of cold days per year and an increase in the number of warm days. A decreasing inter-annual variability is observed. In winter, spring and autumn, the stations in the northernmost areas of west Spitsbergen and in the innermost parts of Isfjorden are the coldest ones. In summer, however, the southernmost station is the coldest one.

DAILY MINIMUM AND MAXIMUM AIR TEMPERATURE IN POLAND IN THE YEARS 1951–2005

In this study grid data of daily maximum and minimum air temperatures taken from the NCEP/NCAR reanalysis for the territory of Poland for the years 1951–2005 have been used as a basis for an analysis of the spatial distribution of daily maximum and minimum air temperature, the frequency of characteristic days and the variability of these parameters in the period analysed. The results obtained were then compared to the variability in atmospheric circulation in Europe, described by the North Atlantic Oscillation (NAO) index.

Resilience, rapid transitions and regime shifts: Fingerprinting the responses of Lake Żabińskie (NE Poland) to climate variability and human disturbance since AD 1000:

Rapid ecosystem transitions and adverse effects on ecosystem services as responses to combined climate and human impacts are of major concern. Yet few long-term (i.e. >60 years) quantitative observational time series exist, particularly for ecosystems that have a long history of human intervention. Here, we combine three major environmental pressures (land use, nutrients and erosion) with quantitative summer and winter climate reconstructions and climate model simulations to explore the system dynamics, resilience and the role of disturbance regimes in varved eutrophic Lake Żabińskie (NE Poland) since AD 1000. The comparison between these independent sources of information allows us to establish the coherence and points of disagreements between such data sets. We find that climate reconstructions capture noticeably natural forced climate variability, while internal variability is the dominant source of variability during most parts of the last millennium at the regional scale, precisely at which climate models seem to underestimate forced variability. Using different multivariate analyses and change point detection techniques, we identify ecosystem changes through time and shifts between rather stable states and highly variable ones. Prior to AD 1600, the lake ecosystem was characterised by high stability and resilience against observed natural climate variability. During this period, the anthropogenic fingerprint was small; the lake ecosystem was buffered against the combined human and natural disturbance. In contrast, lake–ecosystem conditions started to fluctuate across a broad range of states after AD 1600. The period AD 1745–1886 represents the phase with the strongest human disturbance of the catchment–lake ecosystem. During that time, the range of natural climate variability did not increase. Analyses of the frequency of change points in the multi-proxy data set suggest that the last 400 years were highly variable and increased vulnerability of the ecosystem to the anthropogenic disturbances. This led to significant rapid ecosystem transformations.