Above-average Temperatures Research Articles

Sensitivity of Nothofagus dombeyi tree growth to climate changes along a precipitation gradient in northern Patagonia, Argentina

Recent variations in climate appear to induce similarities in the responses of N. dombeyi growth along its entire distribution, supporting global convergence in tree growth responses to climate changes. Understanding forest responses to climate variations is urgently needed for anticipating changes in forest composition and biodiversity. We use twelve tree-ring chronologies from Nothofagus dombeyi, the dominant tree at mesic-to-humid sites, to characterize climate–growth relationships along the west-to-east precipitation gradient in Nahuel Huapi National Park, Argentina. A principal components analysis indicates that a large proportion of common variance in tree growth reflects regional-scale influences of climate. Correlation functions between climate and tree-ring indexes show that the critical factor regulating tree growth is spring–summer water deficit induced by above-average temperature and reduced precipitation during the growing season. At high elevations, however, tree growth appears to be less sensitive to water deficit but comparatively more sensitive to warmer conditions. Temporal trends in climate–tree growth relationships supported the occurrence of a dominant large-scale climatic response, but also identify changes in climate–growth relationships over time, primarily at wet and high-elevation sites. These variations in climate–growth relationships are interpreted as a convergence process to similar patterns in tree growth across the entire precipitation gradient, as wet–cool conditions at high-elevation sites turned to be less frequent due to drier and warmer years during the late twentieth century. Sampling along environmental gradients provides a comprehensive view of the potential range of responses of tree growth to climate which is not recorded using traditional dendrochronological sampling at marginal, more climate-sensitive sites. The recent changes in the relationships between climate and growth highlight the vulnerability of N. dombeyi to climate changes across its entire range of distribution in Argentina.

Temperature alters food web body-size structure.

The increased temperature associated with climate change may have important effects on body size and predator-prey interactions. The consequences of these effects for food web structure are unclear because the relationships between temperature and aspects of food web structure such as predator-prey body-size relationships are unknown. Here, we use the largest reported dataset for marine predator-prey interactions to assess how temperature affects predator-prey body-size relationships among different habitats ranging from the tropics to the poles. We found that prey size selection depends on predator body size, temperature and the interaction between the two. Our results indicate that (i) predator-prey body-size ratios decrease with predator size at below-average temperatures and increase with predator size at above-average temperatures, and (ii) that the effect of temperature on predator-prey body-size structure will be stronger at small and large body sizes and relatively weak at intermediate sizes. This systematic interaction may help to simplify forecasting the potentially complex consequences of warming on interaction strengths and food web stability.

Tree-ring inferred annual mean temperature variations on the southeastern Tibetan Plateau during the last millennium and their relationships with the Atlantic Multidecadal Oscillation

We present two tree-ring chronologies for the southeastern Tibetan Plateau (TP), established by applying the signal-free regional curve standardization and standard dendrochronological methodologies to a set of ring-width series of Tibetan juniper. The relationship between tree growth and climate shows that temperature variability in the previous year is the primary factor controlling tree growth at the upper portion of the forest belt. Accordingly, we developed a mean annual temperature reconstruction covering the period A.D. 984–2009 and explaining 50 % of the instrumental variance. The spatial correlation patterns suggest that our temperature reconstruction is a reasonable proxy for temperature change over the TP. At long time scales, the temperature reconstruction shows similar warm-cold patterns to those in temperature records from other regions of the TP, indicating that decadal and multidecadal temperature variations were generally synchronous across the TP during the past millennium. The periods 1140–1350 and 1600–1800 were common warm and cold episodes over the TP, respectively. Comparison of our reconstruction with four Northern Hemisphere (NH) temperature series indicates that temperature changes on the southeastern TP have generally followed the NH temperature patterns during the past millennium. Our results also suggest that temperature variability over the TP is affected by the Atlantic Multidecadal Oscillation (AMO), with the warm (cool) phases of the AMO associated with above-average (below-average) temperatures over the TP.

Adapting Urban Water Systems to a Changing Climate: Lessons from the Millennium Drought in Southeast Australia

Feature pubs.acs.org/est Adapting Urban Water Systems to a Changing Climate: Lessons from the Millennium Drought in Southeast Australia Stanley B. Grant,* ,†,‡ Tim D. Fletcher, ⊥ David Feldman, § Jean-Daniel Saphores, †,§ Perran L. M. Cook, # Mike Stewardson, ‡ Kathleen Low, † Kristal Burry, ∇ and Andrew J. Hamilton ∥ Department of Civil and Environmental Engineering, E4130 Engineering Gateway, University of California, Irvine, Irvine, California 92697-2175, United States Department of Infrastructure Engineering, Melbourne School of Engineering, Engineering Block D, The University of Melbourne, Parkville 3010, Victoria, Australia Department of Planning, Policy, and Design, 300G Social Ecology I, University of California, Irvine, Irvine, California 92697-7075, United States Department of Agriculture and Food Systems, The University of Melbourne, 940 Dookie−Nalinga Road, Dookie College, Victoria 3647, Australia Melbourne School of Land and Environment, The University of Melbourne, Burnley Campus, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia Water Studies Centre, School of Chemistry, Monash University, Victoria 3800, Australia Melbourne School of Land and Environment, The University of Melbourne, Parkville Campus, 207 Bouverie Street, Victoria 3052, Australia the way Melburnians source and use their water resources and discuss what these changes may portend for other large cities in water-scarce and climate-change-vulnerable regions of the world, in particular, the Southwest region of the United States. MELBOURNE’S WATER SUPPLY Melbourne sources most of its water from protected stream catchments located in uninhabited mountain ash (Eucalyptus regnans) forests to the north and northeast of the city (Figure 1). Runoff from these protected catchments flows by gravity into ten harvesting reservoirs and, from there, through a network of aqueducts and pipelines to storage reservoirs where it is distributed, after minimal treatment, to local service reservoirs. Since the first harvesting reservoir was built in the mid-1800s, Melbourne’s protected catchments have provided the city with a safe, low-energy, and mostly reliable source of high quality drinking water. However, they have also left the city vulnerable to water shortages during periods of very low precipitation. 5 To buffer against water shortages, Melbourne recently invested in various water supply augmentation schemes, including an interbasin transfer pipeline (the North−South or Sugarloaf Pipeline) and the largest desalination plant in the Southern Hemisphere (the Wonthaggi Desalination Plant) (Figure 1). These two projects were built at a capital cost of approximately AU$700 million 6 and AU$6 billion, 7 respec- tively, and can deliver annually up to 75 and 150 GL of water to Melbourne; combined, that equates to about 40% of the city’s present day municipal water demand. However, since their completion in 2010 (Sugarloaf Pipeline) and 2012 (Wonthaggi Desalination Plant), neither A LONG HISTORY OF DROUGHT IN MELBOURNE Australia is the world’s driest inhabited continent, and its population is one of the most urban. As of 2010, 89% of Australia’s 21 million inhabitants lived in urban areas. 1 Finding adequate water resources to sustain Australia’s cities is an ongoing challenge. 2 Nowhere is that more apparent than in Melbourne, a coastal city of approximately 4 million people located on the country’s southeastern coast. Over its 166-year history, Melbourne has experienced eight major droughts. The most recent one, known as the Millennium Drought, started in 1997 and lasted more than a decade. By 2009, below-average precipitation and above-average temperatures drained the city’s drinking-water reservoirs and stoked bush fires, including the “Black Saturday” fire that damaged 30% of the city’s water supply catchment and claimed 173 lives. 3 The Millennium Drought also altered public perceptions about global climate change, water conservation, and water-use behaviors, and energized city managers and politicians to adopt a wide range of approaches for augmenting water supplies and conserving water resources, although the contribution of climate change to the Millennium drought, while plausible, remains unproven. 4 In this paper, we explore how the Millennium Drought changed © 2013 American Chemical Society Special Issue: Design Options for More Sustainable Urban Water Environment Published: May 3, 2013 dx.doi.org/10.1021/es400618z | Environ. Sci. Technol. 2013, 47, 10727−10734

Climate variability and outbreaks of infectious diseases in Europe.

Several studies provide evidence of a link between vector-borne disease outbreaks and El Niño driven climate anomalies. Less investigated are the effects of the North Atlantic Oscillation (NAO). Here, we test its impact on outbreak occurrences of 13 infectious diseases over Europe during the last fifty years, controlling for potential bias due to increased surveillance and detection. NAO variation statistically influenced the outbreak occurrence of eleven of the infectious diseases. Seven diseases were associated with winter NAO positive phases in northern Europe, and therefore with above-average temperatures and precipitation. Two diseases were associated with the summer or spring NAO negative phases in northern Europe, and therefore with below-average temperatures and precipitation. Two diseases were associated with summer positive or negative NAO phases in southern Mediterranean countries. These findings suggest that there is potential for developing early warning systems, based on climatic variation information, for improved outbreak control and management.

Fine root standing stock and production in young beech and spruce stands

AbstractFine roots (defined by a maximum diameter of 2 mm) and assimilatory organs are the compartments which rotate carbon much faster than any other tree part. We focused on quantification of fine roots in young European beech and Norway spruce trees growing under the same ecological conditions. Standing stock of fine roots was estimated by soil coring during 2009 - 2012. Fine root production was established by the in-growth bag method. Standing stock and productions of fine roots were comparable in both tree species. The quantity of fine root biomass (at a soil depth of 0 -50 cm) varied inter-annually between 6.08 and 7.41 t per ha in the beech and from 5.10 to 6.49 t per ha in the spruce stand. Annual production of fine roots (soil depth of 0 - 30 cm) was between 1.11 and 1.63 t ha-1 in beech and between 0.95 and 1.54 t.ha-1 in spruce. We found that fine root standing stock at the beginning of each growing season was related to climatic conditions in the previous year. Annual fine root production was influenced by the climatic situation of the current year. In general, a maximum standing stock of fine roots as well as a relatively slow fine root turnover is expected in young forest stands. Whereas production of fine roots prevailed over mortality in a favorable year (sufficiency of precipitations and slightly above-average temperatures in 2010), there was a reverse situation in an unfavorable year (drought episodes in 2011). We concluded that although both forest types represented contrasting turnovers of assimilatory organs (once a year and once in 5 years in beech and spruce respectively), fine root turnover rates were very similar (approx. once per four years).

Tree-ring derived Little Ice Age temperature trends from the central British Columbia Coast Mountains, Canada

Most glaciers in the British Columbia Coast Mountains reached their maximum Holocene extent during the Little Ice Age. Early- and late-Little Ice Age intervals of expansion and retreat fluctuations describe a mass-balance response to changing climates. Although existing dendroclimatic records provide insights into these climatic fluctuations over the last 400yr, their short durations prohibit evaluation of early-Little Ice Age climate variability. To extend the duration of these records, submerged coarse woody debris salvaged from a high-elevation lake was cross-dated to living chronologies. The resulting chronology provides the opportunity to reconstruct a regional June–July air-temperature anomaly record extending from AD1225 to 2010. The reconstruction shows that the intervals AD1350–1420, 1475–1550, 1625–1700 and 1830–1940 characterized distinct periods of below-average June–July temperature followed by periods of above-average temperature. Our reconstruction provides the first annually resolved insights into high-elevation climates spanning the Little Ice Age in this region and indicates that Little Ice Age moraine stabilization corresponds to persistent intervals of warmer-than-average temperatures. We conclude that coarse woody debris submerged in high-elevation lakes has considerable potential for developing lengthy proxy climate records, and we recommend that researchers focus attention on this largely ignored paleoclimatic archive.

Cold and Hot Periods Associated with Dry Conditions over the Canadian Prairies

Dry conditions and droughts are a normal feature of the Canadian Prairie climate. A common perception is that these periods of below-normal precipitation are always associated with above-average temperatures. Using a core region centred near Edmonton, Alberta, this study incorporates gridded temperature and precipitation information for the period 1900–2009 to quantify how often cold, as well as hot, dry conditions occurred. Shorter-term records of atmospheric circulation, upper-air soundings and surface cloud-related variables are then used to examine some of the factors leading to these conditions. Using drought criteria based on the Standardized Precipitation Index, 15 month-long anomalously cold, dry periods were identified; this is about an order of magnitude less than the number of hot, dry periods. Cold periods generally occurred in the late spring and occurred within some of the major droughts affecting the region. The cold periods were linked with the advection of cold, dry air from the north, whereas hot periods were somewhat attributable to air descending the eastern flank of the Western Cordillera. To understand drought fully, all conditions leading to the persistent lack of precipitation need to be considered including those instances with cold temperatures. RÉSUMÉ [Traduit par la redaction] Les conditions sèches et les sécheresses représentent un phénomène normal dans les Prairies. Il est communément admis qu'au cours de ces périodes caractérisées par des précipitations inférieures à la normale, les températures sont invariablement supérieures à la moyenne. Dans notre étude, qui porte sur une région centrale près d'Edmonton en Alberta, nous intégrons les données maillées sur les températures et les précipitations entre 1900 et 2009 afin de quantifier la fréquence à laquelle les conditions sèches par temps froid autant que par temps chaud se sont présentées. Nous nous servons ensuite des enregistrements à court terme de la circulation atmosphérique, d'observations en altitude et de variables de surface liées aux nuages afin d'examiner quelques facteurs responsables de ces conditions. Au moyen de critères de sécheresse établis en fonction de l'Indice des précipitations normales, nous avons établi qu'il y a eu 15 périodes de sécheresse de durée d'un mois par temps anormalement froid, ce qui est inférieur au nombre de périodes de sécheresse par temps chaud. Les périodes froides ont généralement eu lieu à la fin du printemps, pendant quelques-unes des grandes sécheresses qui ont frappé la région. Ces périodes étaient reliées à l'advection de l'air froid et sec provenant du nord; en revanche, les périodes chaudes étaient dans une certaine mesure attribuables à l'air descendant sur le flanc est de la Cordillère nord-américaine. Pour bien comprendre le phénomène des sécheresses, il faut tenir compte de toutes les conditions qui expliquent l'absence persistante de précipitations, y compris les occurrences avec temps froid.

옥상녹화에 의한 전기화재 감소효과에 관한 연구

As cities of modern society is developed into high-density areas, they are confronted with several problems. Those problems could be divided into two ways. One is above-average temperatures caused by pollution and the other is the energy depletion. That is the reality we are confronted with. Heat Island, one of the phenomenons of above-average temperatures in cities by reducing greenbelt, occurs and the amount of energy used for air conditioning and heating also increases. In this study, we confirmed the correlation between energy saving effects and frequency of electrical fire as a result of the study on how energy saving effects depending on the temperature change of buildings influence the electrical fire, one of the causes of fire.

Biologically effective rate of saflufenacil/dimethenamid-p in soybean (Glycine max)

Miller, R. T., Soltani, N., Robinson, D. E., Kraus, T. E. and Sikkema, P. H. 2012. Biologically effective rate of saflufenacil/dimethenamid- in soybean (Glycine max). Can. J. Plant Sci. 92: 517–531. A total of five field studies were conducted over a 2-yr period (2009, 2010) at three Ontario locations to determine the biologically effective rate of saflufenacil/dimethenamid-p applied preemergence (PRE) for the control of annual weeds in soybean. The rate of saflufenacil/dimethenamid-p required for the control of annual weeds was influenced by environmental conditions. With adequate moisture and above-average temperatures in 2010, between 224 and 374 g a.i. ha-1 of saflufenacil/dimethenamid-p was required for 80% control of common ragweed, common lamb's quarters, and green foxtail 4 wk after treatment (WAT). In contrast, below-average temperatures and excessive moisture in 2009 resulted in higher rates of saflufenacil/dimethenamid-p being necessary for the same level of weed control. Pigweed species were l...

Biologically effective rate of saflufenacil/dimethenamid-p in soybean (Glycine max)

Miller, R. T., Soltani, N., Robinson, D. E., Kraus, T. E. and Sikkema, P. H. 2012. Biologically effective rate of saflufenacil/dimethenamid- in soybean ( Glycine max ). Can. J. Plant Sci. 92: 517–531. A total of five field studies were conducted over a 2-yr period (2009, 2010) at three Ontario locations to determine the biologically effective rate of saflufenacil/dimethenamid-p applied preemergence (PRE) for the control of annual weeds in soybean. The rate of saflufenacil/dimethenamid-p required for the control of annual weeds was influenced by environmental conditions. With adequate moisture and above-average temperatures in 2010, between 224 and 374 g a.i. ha−1 of saflufenacil/dimethenamid-p was required for 80% control of common ragweed, common lamb's quarters, and green foxtail 4 wk after treatment (WAT). In contrast, below-average temperatures and excessive moisture in 2009 resulted in higher rates of saflufenacil/dimethenamid-p being necessary for the same level of weed control. Pigweed species were least affected by environmental conditions after application at 4 WAT with only 245 g a.i. ha−1 required for 80% control in both years. By 11 WAT, 320 g a.i. ha−1 or less of saflufenacil/dimethenamid-p was required to achieve 80% control of these species in 2010, while 845 g a.i. ha−1 or more was needed in 2009 for equivalent control. The potential of saflufenacil/dimethenamid-p as a set-up treatment prior to a postemergence (POST) glyphosate application was also examined. Excellent full season control of all weed species was achieved with saflufenacil/dimethenamid-p applied PRE followed by glyphosate POST. However, there was no difference in yield when saflufenacil/dimethenamid-p was followed by glyphosate POST compared with a single glyphosate POST application.

Annual increments of juniper dwarf shrubs above the tree line on the central Tibetan Plateau: a useful climatic proxy

Dendroclimatology is playing an important role in understanding past climatic changes on the Tibetan Plateau. Forests, however, are mainly confined to the eastern Tibetan Plateau. On the central Tibetan Plateau, in contrast, shrubs and dwarf shrubs need to be studied instead of trees as a source of climate information. The objectives of this study were to check the dendrochronological potential of the dwarf shrub Wilson juniper (Juniperus pingii var. wilsonii) growing from 4740 to 4780 m a.s.l. and to identify the climatic factors controlling its radial growth. Forty-three discs from 33 stems of Wilson juniper were sampled near the north-eastern shore of the Nam Co (Heavenly Lake). Cross-dating was performed along two directions of each stem, avoiding the compression-wood side as far as possible. A ring-width chronology was developed after a negative exponential function or a straight line of any slope had been fit to the raw measurements. Then, correlations were calculated between the standard ring-width chronology and monthly climate data recorded by a weather station around 100 km away. Our study has shown high dendrochronological potential of Wilson juniper, based on its longevity (one individual was 324 years old), well-defined growth rings, reliable cross-dating between individuals and distinct climatic signals reflected by the ring-width variability. Unlike dwarf shrubs in the circum-arctic tundra ecosystem which positively responded to above-average temperature in the growing season, moisture turned out to be growth limiting for Wilson juniper, particularly the loss of moisture caused by high maximum temperatures in May-June. Because of the wide distribution of shrub and dwarf shrub species on the central Tibetan Plateau, an exciting prospect was opened up to extend the presently existing tree-ring networks far up into one of the largest tundra regions of the world.

Temperature variability at Dürres Maar, Germany during the Migration Period and at High Medieval Times, inferred from stable carbon isotopes of <i>Sphagnum</i> cellulose

Abstract. This paper presents a high resolution reconstruction of local growing season temperature (GST) anomalies at Dürres Maar, Germany, spanning the last two millennia. The GST anomalies were derived from a stable carbon isotope time series of cellulose chemically extracted from Sphagnum leaves (δ13Ccellulose) separated from a kettle-hole peat deposit of several metres thickness. The temperature reconstruction is based on the Sphagnum δ13Ccellulose/temperature dependency observed in calibration studies. Reconstructed GST anomalies show considerable centennial and decadal scale variability. A cold and presumably wet phase with below-average temperature is reconstructed between the 4th and 7th century AD which is in accordance with the so called European Migration Period, marking the transition from the Late Roman Period to the Early Middle Ages. At High Medieval Times, the amplitude in the reconstructed temperature variability is most likely overestimated; nevertheless, above-average temperatures are obvious during this time span, which are followed by a temperature decrease. On the contrary, a pronounced Late Roman Climate Optimum, often described as similarly warm or even warmer as medieval times, could not be detected. The temperature signal of the Little Ice Age (LIA) is not preserved in Dürres Maar due to considerable peat cutting that takes place in the first half of the 19th century. The local GST anomalies show a remarkable agreement to northern hemispheric temperature reconstructions based on tree-ring datasets and are also in accordance with climate reconstructions on the basis of lake sediments, glacier advances and retreats, and historical datasets. Most notably, e.g., during the Early Middle Ages and at High Medieval Times, temperatures were neither low nor high in general. Rather high frequency temperature variability with multiple narrow intervals of below- and above-average temperatures at maximum lasting a few decades are reconstructed. Especially the agreements between our estimated GST anomalies and temperature reconstructions derived from tree-ring chronologies indicate the great potential of Sphagnum δ13Ccellulose time series from peat deposits for palaeoclimate research. This is particularly the case, given that a quantitative δ13Ccellulose/temperature relationship has been found for several Sphagnum species. Although the time resolution of Sphagnum δ13Ccellulose datasets certainly wouldn't reach the annual resolution of tree-ring data, reconstructions of past temperature variability on the basis of this proxy hold one particular advantage: often due to relatively high peat accumulation rates, especially in kettle-hole bogs accumulated on temperate latitudes over periods of up to several millennia, they allow extending temperature reconstructions based on tree-ring series into the past to enhance our knowledge of natural climate variability during the Holocene.

Circulation and surface controls on the lower tropospheric air temperature field of the Arctic

[1] Characteristics of the 925 hPa Arctic air temperature field are evaluated with respect to controls by horizontal temperature advection, vertical motion, and characteristics of the underlying land and ocean surface. The highest winter mean temperatures in the Arctic, found in the Norwegian and Barents seas, are maintained primarily by cold horizontal advection countered by diabatic heating, the latter linked to open ocean waters. By comparison, temperatures over the central Arctic Ocean are primarily maintained by warm advection and diabatic cooling. Depending on the region, vertical motion opposes (notably off the east coast of Greenland) or reinforces forcing by advection. For summer, cold advection over snow-free land is countered by diabatic warming. This contrasts sharply with the Arctic Ocean, where warm advection and (locally) downward vertical motion combine to oppose pronounced diabatic cooling, the latter linked to surface melt and heat uptake in the ocean mixed layer. Prominent temperature anomalies in all seasons accompany onshore and offshore flow. For example, summer northerlies, blowing off the Arctic Ocean, yield cold anomalies over northern Eurasia extending far inland from the coast. While onshore winter westerlies yield above-average temperatures over northwestern Eurasia and the Barents and Kara seas, easterlies yield cold anomalies in the same regions. The most recent decade (2000–2009) has seen positive temperature anomalies over most of the Arctic for northerlies, easterlies, southerlies, and westerlies and for all seasons. Influences of recent shifts in atmospheric circulation, reduced sea ice extent, and rising sea surface temperature are prominent, especially for winter and autumn.

Impact of two different types of El Nino events on the Amazon climate and ecosystem productivity

Aims The Amazon basin plays an important role in the global carbon budget. Interannual climate variability associated with El Nino can affect the Amazon ecosystem carbon balance. In recent years, studies have suggested that there are two different types of El Ninos: eastern-Pacific (EP) El Nino and central-Pacific (CP) El Nino. The impacts of two types of El Nino on the Amazon climate and Amazon ecosystem are analyzed in the study. Methods A composite method has been applied to highlight the common features for the EPand CP-El Nino events using observational data, IPCC-AR4 model output. Potential impacts of the two different types of El Nino on ecosystem carbon sequestration over the Amazon have been investigated using a process-based biogeochemical model, the Biome–BioGeochemical Cycles model (Biome–BGC). Important Findings Below-normal rainfall is observed year round in northern, central and eastern Amazonia during EP-El Nino years. During CP-El Nino years, negative rainfall anomalies are observed in most of the Amazon during the austral summer wet season, while there is average or above-average precipitation in other seasons. EPand CP-El Nino events produce strikingly different precipitation anomaly pattern in the tropical and subtropical Andes during the austral fall season: wetter conditions prevail during EP-El Nino years and drier conditions during CP-El Nino years. Temperatures are above-average year round throughout tropical South America during EP-El Nino events, especially during austral summer. During CP-El Nino events, average or slightly above-average temperatures prevail in the tropics, but these temperatures are less extreme than EP year’s temperature except in austral fall. These precipitation and temperature anomalies influence ecosystem productivity and carbon sequestration throughout the Amazon. Using the Biome–BGC model, we find that net ecosystem production (NEP) in the EP-El Nino years is below average, in agreement with most previous studies; such results indicate that the Amazon region acts as a net carbon source to the atmosphere during EP-El Nino years. In the CP-El Nino years, NEP does not differ significantly from its climatological value, suggesting that the Amazon forest remains a carbon sink for the atmosphere. Thus, even if CP-El Nino events increase in frequency or amplitude under global warming climate as predicted in some Global Climate Models, the Amazon rainforest may remain a carbon sink to the atmosphere during El Nino years in the near future.

Plant species’ range shifts in mountainous areas—all uphill from here?

Species from many different habitats are responding to recent climate change. Mountainous areas are of particular interest as they provide pronounced gradients and have experienced above-average temperature increases. Data from the beginning of the 20th century of both the upper and lower range limits of plants of the European Alps were updated a century later and analyzed in order to identify common trends and deviating patterns of shifts at opposing ends of species’ ranges. At the upper limit, there was a strong trend towards an increase in species richness per summit, including 33 species that were recorded for the first time on any of the investigated summit areas. The species experienced a consistent upward shift exceeding 100 elevational meters, and 49 out of the 125 investigated species shifted upwards to a present altitude which is higher than any reported occurrence in the region one century ago. The response at the lower range limit was more heterogeneous and suggests species-specific differences in responsiveness and response patterns. With this approach of the combined analysis of upper and lower range limits along elevational gradients, it is possible to identify candidate species that might not keep pace with climate change, and thus, might face an increased risk of extinction with continued global warming.

The Application of the Cluster Analysis in Recognizing Weather Patterns Conducive to Large and Small Crops of Mid-late Onion Cultivars (Allium cepa L.) in Poland

This study uses 40 years valuable of data (1966-2005) obtained by the Polish Research Centre for Cultivar Testing and the Polish Institute of Meteorology and Water Management to recognize weather conditions conducive to large and small crops of onion (Allium cepa L.), more specifically-its mid-late cultivars cultivated in Poland. We found three clusters of agrometeorological conditions, determining different sizes of onion crops. Cluster no. 1 included observations which were characterized by large onion crops (45.9 t ha-1 for the total crop and 44.7 t ha-1 for the commercial crop) and cluster no. 3 was characterized by a small crop (respectively 26.2 and 24.8 t ha-1). Large crops were favored by the following weather patterns: during sowing-end of emergence, above-average sunshine duration (8.1 h) and above-average air temperature (13.0oC); in end of emergence-beginning of leaf bending-average sunshine duration (7.4 h), average soil temperature (18.7oC) and air temperature (16.8oC) and above-average rainfall, described by the coefficient of rainfall (2.8 mm); in beginning of leaf bending-harvest-soil temperature (17.3oC) and air temperature (16.0oC) lower than a long-term average. Temperatures of soil and air that are higher than a long-term average, especially in the period sowing-end of emergence, with a parallel stable level of rainfall, may cause a reduction in onion crops in Poland.

Observations of particle growth at a remote, Arctic site

Observations of particle size distributions suggest that particles grow significantly just above the snow surface at a remote, Arctic site. Measurements were made at Summit, Greenland (71.38°N and 31.98°W) at approximately 3200 m above sea level. No new particle formation was observed locally, but growth of ultrafine particles was identified by continuous evolution of the geometric mean diameter (GMD) during four events. The duration of the growth during events was between 24 and 115 h, and calculated event-average growth rates (GR) were 0.09, 0.30, 0.27, and 0.18 nm h −1 during each event, respectively. Four-hour GR up to 0.96 nm h −1 were observed. Events occurred during below- and above-average temperatures and were independent of wind direction. Correlation analysis of hourly-calculated GR suggested that particle growth was limited by the availability of photochemically produced precursor gases. Sulfuric acid played a very minor role in particle growth, which was likely dominated by condensation of organic compounds, the source of which was presumably the snow surface. The role of boundary layer dynamics is not definite, although some mixing at the surface is necessary for the observation of particle growth. Due to the potentially large geographic extent of events, observations described here may provide a link between long-range transport of mid-latitude pollutants and climate regulation in the remote Arctic.

Assessment of the value of tropospheric ozone concentration dependingon meteorological conditions as exemplified by the Widuchowa station (North-West Poland).

kalbarczyk r., kalbarczyk e.: Assessment of the value of tropospheric ozone concentration depending on meteorological conditions as exemplified by the Widuchowa station (north-West Poland). ekologia (Bratislava), vol. 29, no. 4, p. 398-411, 2010. The aim of the work was to find the temporal distribution of tropospheric ozone in connection with the course of meteorological conditions by night and daytime according to months, days and, next, hours and wind direction and to isolate a weather complex which was accompanied by the highest concentration of o3. The foundation of the study was hourly values of o3 concentration in 2005–2008, and hourly data on five meteorological elements (total solar radiation, air temperature, relative air humidity, atmospheric pressure and direction and velocity of wind) in April 2006, from the Widuchowa station located at the Polish–German border in north-West Poland. The effect of meteorological conditions on ozone concentration values was determined with the use of Pearson’s correlation analysis and cluster analysis. The highest mean concentration of ozone, out of the 48 analysed months in 2005–2008, was recorded in April 2006, by daytime, with the wind coming from westerly, easterly, south-westerly and southerly directions. The following weather situation was conducive to the highest o3 concentrations, amounting, on average, to about 127 μg.m -3: above-average mean total solar radiation (about 237 W.m-2), above-average mean air temperature (11.5°C), below-average relative air humidity (about 52%), above-average atmospheric pressure (about 1016 hPa) and above-average mean wind velocity (2.4 m.s-1).

Development of temperatures in the Kingdom of Bahrain from 1947 to 2005

A new look is focused in this study on the analysis of mean temperatures for Bahrain, as observed at its International Airport for the 59 years extending from 1947 to 2005. The temporal trends indicate significant warming of the dry-season temperatures of 0.166°C decade−1. In particular, the summer months of May to July and October demonstrate statistically significant trends of 0.172 to 0.247°C decade−1. There is a tendency for the wet season months to show both decreases and increases in their temperatures though the temporal trends are not significant. The decade of 1991-2000 emerged as a period of conspicuous warming as well as increase in the occurrence of unusual mean temperatures and the number of months per year with above-average temperature. No significant trend in intraannual and intraseasonal temperature variabilities is discerned, but the wet season shows predominantly higher within-season variability in temperatures as compared to the dry season. Further analyses have been carried out on the available extreme temperature data for the period 1981-2005 in an attempt to search for a possible source of climatic and/or non-climatic factors, such as intensifying desertification and rapid urbanization. By and large, the rates of diurnal temperature ranges have increased due to significantly higher rates of increasing maximum in comparison to increasing minimum temperatures. The warming rate of the overall dry season during the day is seven times that during night. However, the nocturnal temperature for the overall wet season has warmed significantly at a rate more than three times that of the overall dry season. There is a sufficient evidence that sources of rapid urbanization around the area of records seem to be a major contributor to the observed rates of temperature. Both the urbanization and the effect of the large water body of the Gulf surrounding the Island of Bahrain seem to have offset the effect of desertification on temperature changes.