Night Warming Research Articles

Effects of experimental warming and nitrogen fertilization on soil microbial communities and processes of two subalpine coniferous species in Eastern Tibetan Plateau, China

This study aimed at predicting how sub-alpine coniferous ecosystems respond to global changes in the Eastern Tibetan Plateau by understanding soil microbial communities and activities, as well as variation in the quality and quantity of soil organic matter. An experiment was conducted to examine soil microbial communities and their related soil processes in rhizospheric soil of two coniferous species that were exposed to two levels of temperature (unwarmed and infrared heater warming) and two levels of nitrogen (unfertilized and 25 g N m−2 a−1) from April 2007. Four-year night warming alone slightly affected the phospholipid fatty acid contents of the microbial community. However, the combination of nitrogen addition and soil warming significantly affected soil microbial composition while reducing the biomass of major microbial groups and the activities of most enzymes, especially in Abies faxoniana plots. The combination of warming and nitrogen addition increased soil labile C and N pools in Picea asperata plots and was beneficial for soil recalcitrant C, as well as for labile and total C and N pools in A. faxoniana plots. Results indicated that future warming will slightly affect soil microbial communities and their related soil processes. However, warming combined with high nitrogen deposition will significantly constrain soil microbial biomass and enzyme activities, consequently increasing soil C and N pools in sub-alpine coniferous forests of this region.

Effects of night warming on spruce root around non-growing season vary with branch order and month

Background and aims The Root is an important plant organ and has high heterogeneity; how it responds to global warming is yet to be answered. This study examined the growth and physiological responses of fine roots to warming around the non-growing season.

Night warming on hot days produces novel impacts on development, survival and reproduction in a small arthropod

An asymmetric increase in night-time temperatures (NTs) on hot days is one of the main features of global climate change. But the biological effects of an increased night-time temperature combined with high daytime temperature are unclear. We used six thermal regimens to simulate NTs on hot days and investigated the effects of night warming on life-history traits of the English grain aphid Sitobion avenae. Experimental temperatures fluctuated in continuous diurnal cycles, increasing from 27 °C to a maximum 35 °C and then declining to 27 °C gradually before further dropping to different minima (13, 16, 19, 21, 23 or 25 °C) representing NTs. When compared to expectations based on constant temperatures, night warming raised the optimum temperature for development by 3 °C, in contrast to results from experiments where temperature variability was altered symmetrically or in a parallel manner. Night warming also reduced aphid survival under heat from 75% to 37% and depressed adult performance by up to 50%. Overall, night warming exacerbated the detrimental effects of hot days on the intrinsic rate of population increase, which was predicted to drop by 30% when night-time minimum temperatures exceeded 20 °C. Our novel findings on development challenge the 'Kaufmann effect', suggesting this is inapplicable to night warming likely to be encountered in nature. Although many average temperature models predict increasing pest outbreaks, our results suggest that outbreaks of some species might decrease due to the effects of night warming on population dynamics.

三种增温情景对入侵植物空心莲子草形态可塑性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 三种增温情景对入侵植物空心莲子草形态可塑性的影响 DOI: 10.5846/stxb201306101575 作者: 作者单位: 成都理工大学,成都理工大学,成都理工大学,成都理工大学 作者简介: 通讯作者: 中图分类号: 基金项目: Three warming scenarios differentially affect themorphological plasticity of an invasive herb Alternanthera philoxeroides Author: Affiliation: Chengdu University of Technology,Chengdu University of Technology,Chengdu University of Technology,Chengdu University of Technology Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:虽然国内外已对克隆植物的表型可塑性开展了大量研究，但是气候变暖对克隆植物，尤其是入侵性克隆植物形态可塑性的影响及其可能的生态学意义研究仍然有限。通过设置白天增温、夜间增温和全天增温3种方式，通过切断或不切断匍匐茎处理，探讨入侵植物空心莲子草（Alternanthera philoxeroides）形态特征对不同气候变暖情景的响应。研究发现：夜间增温2 ℃条件下，切断匍匐茎连接显著降低空心莲子草匍匐茎总长度和平均分株长度;白天增温和全天增温2 ℃对匍匐茎切断和连接组的空心莲子草的匍匐茎总长和平均分株长影响不显著;3种增温方式对空心莲子草的分蘖数均无显著影响。这些结果表明：空心莲子草对增温具有较高的耐受性，并对不同增温方式采取不同的响应策略;夜间增温可能通过光合补偿效应增加其匍匐茎的长度和平均分株长从而促进其水平方向的扩展以占据更加有利的生境，增强其入侵能力;白天和全天增温对整个克隆片段匍匐茎形态几乎无影响。 Abstract:Phenotypic plasticity may be one of the crucial factors determining the success of plant invasions in diverse habitats, particularly for those very noxious species with low genetic diversity such as Alternanthera philoxeroides in China. Although phenotypic responses of clonal plants to different light intensities, soil water or soil nutrient availabilities have been extensively studied in the past decades, little is known about how climate warming affects morphological plasticity of plants, particularly invasive plant species. Climate warming is among the serious threats to biodiversity and ecosystem functions, thereby raising concerns over its ecological consequences. Increasing evidence suggests that climate warming is asymmetric and the magnitude of nighttime minimum air temperature may increase greater than that of daytime maximum air temperature. Recent studies have shown that climate warming is likely to have significant effects on plant photosynthesis and respiration. Consequently, it is necessary to understand how terrestrial plants respond to differential warming scenarios, which can help us better predict their response under these conditions. We conducted a simulated warming experiment at Chengdu in which the invasive clonal herb Alternanthera philoxeroides was subjected to each of the eight combinations consisting of serving stolons (i.e. serving and intact stolons) and simulated warming (i.e. day-warming, night-warming, daily warming, and control treatment). This experiment lasted three months. At the end of the experiment the morphological traits of all experimental materials were determined. Overall warming treatment increased air temperature by about 2 ℃, and the warming magnitude was variable depending on specific weather conditions. Our central object was to test how A. philoxeroides plants responded to different warming treatments morphologically. Across all three warming treatments, physically severed connection significantly suppressed the growth of A. philoxeroides fragments primarily through reducing the total stolon length and average stolon length per ramet. In contrast, simulated warming per se did not exhibit significant effects on these indices mentioned above. When the three warming treatments were considered separately, they had contrasting consequences for the morphological traits of A. philoxeroides. Specifically, day-warming and daily-warming did not confer significant impacts on both severed and connected fragments in terms of total stolon length and average stolon length; night warming significantly elongated the total stolon length and average ramet length of A. philoxeroides with connected stolons, but did not affect those of A. philoxeroides with connected stolons; all the three warming scenarios did not affect ramet numbers of both fragments. These findings are relatively preliminary, but they have some potential implications. First, our results suggest that A. philoxeroides fragments may have strong tolerance to the 2 ℃ warming and differentially respond to these projected warming scenarios. Second, for A. philoxeroides fragments commonly growing in disturbed habitats, night-warming may facilitate their growth and clonal integration through photosynthetic overcompensation, thereby enhancing their invasion by rapidly spatial expanding along the horizontal direction and occupying favorable habitats. Third, day-warming and daily warming may have no obvious impacts on the morphological characteristics of those fragments of A. philoxeroides. Finally, modeling plant responses to climate warming should consider warming timing. Additionally, these findings also provide an initial indication that more efforts should be paid to uncover response patterns of plants to different warming scenarios and how these responses influence community composition and structure, and ecosystem functions. 参考文献 相似文献 引证文献

The Effects of Warming-Shifted Plant Phenology on Ecosystem Carbon Exchange Are Regulated by Precipitation in a Semi-Arid Grassland

BackgroundThe longer growing season under climate warming has served as a crucial mechanism for the enhancement of terrestrial carbon (C) sink over the past decades. A better understanding of this mechanism is critical for projection of changes in C cycling of terrestrial ecosystems.Methodology/Principal FindingsA 4-year field experiment with day and night warming was conducted to examine the responses of plant phenology and their influences on plant coverage and ecosystem C cycling in a temperate steppe in northern China. Greater phenological responses were observed under night than day warming. Both day and night warming prolonged the growing season by advancing phenology of early-blooming species but without changing that of late-blooming species. However, no warming response of vegetation coverage was found for any of the eight species. The variances in species-level coverage and ecosystem C fluxes under different treatments were positively dependent upon the accumulated precipitation within phenological duration but not the length of phenological duration.Conclusions/SignificanceThese plants' phenology is more sensitive to night than day warming, and the warming effects on ecosystem C exchange via shifting plant phenology could be mediated by precipitation patterns in semi-arid grasslands.

Day and night warming have different effect on root lifespan

Abstract. Roots are key components of C cycling in terrestrial ecosystems and play an important role in the regulation of response of terrestrial ecosystems to global climate warming, which is predicted to occur with greater warming magnitudes at night than during daytime across different regions on the Earth. However, there has been no detailed study to investigate the effect of asymmetrical warming on root dynamics at the level of terrestrial ecosystems. To understand the effects of day and night warming on root lifespan in the semiarid temperate steppe in northern China, a field study with a full factorial design including control, day warming, night warming and continuous warming was conducted using modified rhizotron technique during three growing seasons in 2007–2009. Our results show that day, night and continuous warming had different effects on longevity of roots born in spring, summer and autumn, and that day warming significantly prolonged overall lifespan for the roots born in the three growing seasons, while night warning had no effect on overall lifespan. Day and night warming had different effects on root non-structural carbohydrate content, suggesting that allocation of photoassimilate may account for the differential responses of root lifespan to day and night warming. These results differ from other processes associated with ecosystems C cycle such as total ecosystem productivity, net ecosystem productivity and soil respiration. Our findings highlight that it is essential to incorporate the differential effects of day and night warming on root dynamics into simulating and predicting the responses and feedbacks of terrestrial ecosystems C cycling to global warming.

Physical connection decreases benefits of clonal integration in Alternanthera philoxeroides under three warming scenarios

Physical connection between ramets usually allows clonal plants to perform better but can have the opposite effects in some cases. Clonal integration and the effects of climate warming have been extensively studied, but to date little is known about how climate warming affects the benefits of clonal integration. We conducted a field experiment in which Alternanthera philoxeroides segments with connected and severed stolons were subject to four climate regimes (ambient, day warming, night warming and daily warming), and measured final biomass, number of ramets and total length of stolons. Across the three warming treatments, temperature rise suppressed growth of clonal fragments with connected stolons but increased growth of fragments with severed stolons; temperature rise affected the biomass of distal ramets but not proximal ramets, and had similar effects on the numbers of proximal and distal ramets. When the three warming treatments were considered separately, they had contrasting consequences for the benefits of clonal integration. Specifically, when fragments were exposed to day and night warming, physical connection evened out the advantages of clonal integration that occur under ambient conditions; when fragments were exposed to daily warming, physical connection led to smaller clonal plants. These findings suggest that physical connection between ramets may be disadvantageous to overall performance of A.philoxeroides fragments under climate warming, and also indicate that the net consequences of daily warming outweigh those of day or night warming.

Soil microbial community changes and their linkages with ecosystem carbon exchange under asymmetrically diurnal warming

The greater increase in daily minimum temperature than daily maximum temperature has been widely observed at global scale. A growing body of evidence suggests that this asymmetrically diurnal warming has great impacts on aboveground ecological processes. However, little is known about the effect of the asymmetrically diurnal warming on belowground biotic organisms. This study was conducted as part of a field manipulative experiment with day (6:00 a.m.–6:00 p.m.), night (6:00 p.m.–6:00 a.m.) and diurnal warming (24 h) in a temperate steppe, to assess shifts in soil microbial community composition and physiology in response to asymmetrically diurnal warming. Our results show that contrasting hydro-thermal conditions of the two experimental years (2006–2007) reshaped microbial community structure and modified C use patterns in the grassland ecosystem. Consistent with our hypothesis, day and night warming had different effects on some specific microbial groups and microbial C utilization potential. Significant reductions in the relative proportion of total bacteria, gram-positive bacteria and arbuscular mycorrhizal fungi and microbial C utilization potential, were observed under conditions of night warming only. The close association of microbial C utilization patterns with ecosystem C exchange and coupled responses of plant and microbe to night warming highlight physiological continuity in plant–microbe–soil system.

Short-term effects of night warming and nitrogen addition on soil available nitrogen and microbial properties in subalpine coniferous forest, Western Sichuan, China.

Aims The subalpine coniferous forest in eastern Qinghai-Tibet Plateau provides a natural laboratory for studying effects of climate change on terrestrial ecosystems. Research on responses of soil nitrogen availability and microbial properties to experimental warming and nitrogen addition can provide insights into their C resource/sink function under future climates. Methods We used an infrared heater combined with nitrogen addition to determine the short-term influences of two level of air temperature (ambient and warmed) and nitrogen addition (0 and 25 g N·m·a) on soil chemical properties, available nitrogen and microbial biomass. Important findings The warming manipulation increased mean air temperature and soil temperature at 5-cm depth by 1.93 and 4.19 °C, respectively, and the temperature increment was larger in summer and winter. Warming generally had no significant effects on soil pH, organic C, total N and microbial biomass, but it decreased soil ammonium nitrogen and increased nitrate nitrogen content. The warming effect was reduced with time. Nitrogen addition significantly increased available nitrogen and microbial biomass, but decreased soil pH, acidifying the soil. Compared with individually warming or adding nitrogen, the interaction of the two factors significantly increased organic C, available N and microbial biomass. Results suggest that soil nitrogen availability and microbial properties were sensitive to N status. Although soil nitrogen availability and microbial properties may adapt to temperature increase to some extent, the interaction of the warming and nitrogen addition significantly changed their response mode. Therefore, nitrogen deposition and multiple factors have interacting effects on the ecosystem and these should be further studied in this region. 陈智等: 夜间增温和施氮对川西亚高山针叶林土壤有效氮和微生物特性的短期影响 1255 doi: 10.3773/j.issn.1005-264x.2010.11.002

System Design of Free Air Temperature Increased (FATI) for Field Nighttime Warming Experiment and Its Effects on Rice-Wheat Cropping System

There is evident asymmetry in climate warming between daytime and nighttime with the highest warming rate occur-ring at nighttime. Since there are high uncertainties in the projecting of climate warming effects on crop production using crop models,it is essential to design a reliable field warming system to study the responses of crop production system to nighttime warming in field. Therefore,based on existing field warming facilities in the world,we designed a rice-wheat warming system in Nanjing,Jiangsu province,the first facility of Free Air Temperature Increased (FATI) for crop production in China,to study the effects of nighttime warming on crop growing duration and yields during 2006–2009. The results showed that the warming effect of this facility was significant and well-distributed within 2 m × 2 m area. In sunny,rainy and cloudy days,the night temperatures on the field surface within the 4 m2 warming area were increased by 2.4℃ ,2.3℃ ,and 2.1℃ on average on the tested turfgrass land. At the vertical dimension,the night temperatures of 5 cm underground,ground surface,40 cm aboveground,and 90 cm aboveground were enhanced by 1.2 ℃,2.2 ℃,0.7 ℃,and 2.3 ℃ on average. In the rice growing period,the night temperatures of 5 cm underground,field surface,the middle part of crop community and the canopy were 0.7℃,0.6℃,1.0℃,and 1.6℃ higher compared to the un-warming plots,respectively. In the winter-wheat growing period,the increments were 1.2℃,1.5℃ ,1.8℃ ,and 1.9 ℃,respectively. During the whole crop growing period,the trends of diurnal change of the above temperatures in warming plots were all similar with those in the un-warming plots. The distributed characteristics of soil moisture in wheat field were not significantly changed under this warming facility but with a slightly decreasing trend. The decrements of soil moisture in the 0–25 cm soil layers were all within the scale of 0.99–1.62 percentage points with no significant difference compared to the un-warming control. Under this warming facility,rice and wheat growing stages were significantly changed,and the durations of rice and wheat from the sowing date to the initial heading date were shortened by 2.5 d and 11.5 d respectively. Nighttime warming reduced rice yield by 4.51%,but increased wheat yield by 18.30% on average. Although,there existed significant differences in the warming rates among different stages of crop growing by using the warming facility,evident seasonal discrepancy of warming rates also often occurred in the real fields under climate warming situation. Therefore,the above results suggest that this night warming facility meets with the temperature characteristics of climate warming and can be used for studies on the responses of crop production system to nighttime warming.

Impacts of day versus night warming on soil microclimate: Results from a semiarid temperate steppe

One feature of climate warming is that increases in daily minimum temperature are greater than those in daily maximum temperature. Changes in soil microclimate in response to the asymmetrically diurnal warming scenarios can help to explain responses of ecosystem processes. In the present study, we examined the impacts of day, night, and continuous warming on soil microclimate in a temperate steppe in northern China. Our results showed that day, night, and continuous warming (approximately 13 W m − 2 with constant power mode) significantly increased daily mean soil temperature at 10 cm depth by 0.71, 0.78, and 1.71 °C, respectively. Night warming caused greater increases in nighttime mean and daily minimum soil temperatures (0.74 and 0.99 °C) than day warming did (0.60 and 0.66 °C). However, there were no differences in the increases in daytime mean and daily maximum soil temperature between day (0.81 and 1.13 °C) and night (0.81 and 1.10 °C) warming. The differential effects of day and night warming on soil temperature varied with environmental factors, including photosynthetic active radiation, vapor-pressure deficit, and wind speed. When compared with the effect of continuous warming on soil temperature, the summed effects of day and night warming were lower during daytime, but greater at night, thus leading to equality at daily scale. Mean volumetric soil moisture at the depth of 0–40 cm significantly decreased under continuous warming in both 2006 (1.44 V/V%) and 2007 (0.76 V/V%). Day warming significantly reduced volumetric soil moisture only in 2006, whereas night warming had no effect on volumetric soil moisture in both 2006 and 2007. Given the different diurnal warming patterns and variability of environmental factors among ecosystems, these results highlight the importance of incorporating the differential impacts of day and night warming on soil microclimate into the predictions of terrestrial ecosystem responses to climate warming.

Impact of inter- and intra-annual variation in weather parameters on mass balance and equilibrium line altitude of Naradu Glacier (Himachal Pradesh), NW Himalaya, India

Glaciers in Himalaya have been studied with respect to their mass balance to assess their response, if any, to global warming. Naradu glacier in the Baspa Valley of Himachal Pradesh is one such glacier that has been studied in the backdrop of the impact of inter- and intra-annual variation in weather parameters on the health of glaciers. The trends in seasonal and monthly mean temperatures from 1994 to 2003 show an interesting shift of peak summer (late August-September) and winter seasons (February-March). The data also suggest night warming during summer (June, August, and September) and winter (November, January, April), and cooling during peak summer seasons (July) and very cold during winter (December, February, March). The fluctuation in ELA, snout position and surface ablation of Naradu glacier is attributed to variation in albedo of rock debris and valley walls from season to season and year to year.

Effects of diurnal warming on soil respiration are not equal to the summed effects of day and night warming in a temperate steppe

Abstract. The magnitude of daily minimum temperature increase is greater than that of daily maximum temperature increase under climate warming. This study was conducted to examine whether changes in soil respiration under diurnal warming are equal to the summed changes under day and night warming in a temperate steppe in northern China. A full factorial design with day and night warming was used in this study, including control, day (06:00 a.m.–06:00 p.m., local time) warming, night (06:00 p.m.–06:00 a.m.) warming, and diurnal warming. Day warming showed no effect on soil respiration, whereas night warming significantly increased soil respiration by 7.1% over the 3 growing seasons in 2006–2008. The insignificant effect of day warming on soil respiration could be attributable to the offset of the direct positive effects of increased temperature by the indirect negative effects via aggravating water limitation and suppressing ecosystem C assimilation. The positive effects of night warming on soil respiration were largely due to the stimulation of ecosystem C uptake and substrate supply via overcompensation of plant photosynthesis. Changes in both soil respiration (+20.7 g C m−2 y−1) and GEP (−2.8 g C m−2 y−1) under diurnal warming are smaller than their summed changes (+40.0 and +24.6 g C m−2 y−1, respectively) under day and night warming. Our findings that the effects of diurnal warming on soil respiration and gross ecosystem productivity are not equal to the summed effects of day and night warming are critical for model simulation and projection of climate-carbon feedback.

Estimating plant competition coefficients and predicting community dynamics from non-destructive pin-point data: a case study with Calluna vulgaris and Deschampsia flexuosa

A method is proposed for estimating plant competition coefficients and predicting the dynamics of herb and grassland plant communities from non-destructive pin-point measurements. The method is applied to inter-specific competition in a natural heathland community with relatively few interacting species. The study shows that the dynamics of the heathland plant community may be thought of as essentially a two-species system of Calluna vulgaris and Deschampsia flexuosa. There were significant competitive interactions between C. vulgaris and D. flexuosa. D. flexuosa affected both the cover and compactness of C. vulgaris individuals as a function of the compactness the previous year, whereas C. vulgaris significantly affected only the compactness of D. flexuosa. There was a significant negative effect of drought on the compactness of both C. vulgaris and D. flexuosa individuals, whereas night warming had no significant effects on either species. The predicted long-term outcome of the competitive interaction between C. vulgaris and D. flexuosa was that of unstable equilibrium, where the more dominant of the two will outcompete the other. However, when both species are found at relatively high plant covers the two species are predicted to co-exist for a long time period relatively to the time scale of the ageing process of C. vulgaris. Direct analyses of the inter-specific competitive interactions in natural plant communities with non-destructive measurements can provide important new insight into the processes that determine the composition of plant communities.

Developmental Instability and Gas Exchange Responses of a Heathland Shrub to Experimental Drought and Warming

The effects of predicted climatic changes on the physiological stress of bilberry (Vaccinium myrtillus L.) were investigated in a field experiment in a heathland of northern Wales (U.K.). In the experiment, drought was increased during the growing season by excluding precipitation, and night warming was created by reducing heat loss. To assess physiological stress, leaf size and leaf fluctuating asymmetry (FA) as integrative measures of stress during leaf development and leaf gas exchange as a classical instantaneous method to detect physiological stress, were measured. Since leaf FA increased with increasing size, comparisons of asymmetries were made for relative rather than absolute asymmetry. Relative leaf FA was calculated as the absolute difference between leaf size (area or width) of left and right halves, corrected for trait size. Drought treatment increased the relative leaf area FA in 2000 and not in 1999, in agreement with a stronger treatment in 2000. Conversely, the warming treatment decreased the relative leaf area FA in 1999 and not in 2000, coinciding with the lower minimum temperatures in the growing season of 1999. Differences in water availability and temperature between years were related with changes in the relative leaf area FA, which were consistent with the treatment effects. In contrast, leaf gas exchange rates and leaf size showed no significant response to the environmental manipulations, although there was a slight decrease of photosynthetic values and leaf size in drought treatments in both years. Leaf FA therefore appeared to be a more sensitive indicator of physiological stress than leaf size or gas exchange measurements. Our results indicate that a future increase in the severity of drought during the growing season will increase physiological stress of V. myrtillus, whereas warming will decrease physiological stress during leaf development because of the alleviation of temperature constraints.

Climate Change and Large‐Area Corn Yield in the Southeastern United States

AbstractThere is concern about the negative effects that a possible trace‐gas‐induced climate change will have on crop yields. This study determines the effect of climate change already observed on large‐area corn yield (Zea mays L.) in the southeastern USA. Our multiple regression models differ from most previous large‐area models in two important respects. First, we modeled simultaneously the technological trend and the climate. This is required because of the warming of Southeastern nights during the past 50 yr. Second, we used maximum and minimum temperatures, rather than average temperature. Our results generally associate yield reductions with increases in daytime temperatures during the month of corn pollination. In the Middle and Upper South, increased yield is associated with warming of nighttime temperatures during mid‐season. A trace‐gas‐induced warming should produce minimal change in maximum temperatures. Because projections of future climate generally indicate more night warming than day warming, our results argue that Southeastern corn yield will either change very little or may increase slightly beyond the increase normally expected from technological advancement.

Global Warming: A Reduced Threat?

Issues associated with global warming are analyzed focusing on global and hemispheric temperature histories and trace gas concentrations; artificial warming from urban heat islands; high-latitude and diurnal temperatures; recent climate models; direct effects on vegetation of an increase in carbon dioxide; and compensatory cooling from other industrial products. Data obtained indicate that anthropogenerated sulfate emissions are mitigating some of the warming, and that increased cloudiness as a result of these emissions will further enhance night, rather than day, warming. It is noted that the sulfate emissions are not sufficient to explain all of the night warming. The sensitivity of climate to anthropogenerated aerosols, and the general lack of previously predicted warming, could drastically alter the debate on global warming in favor of less expensive policies. 61 refs.

Apparent diurnal variations of arctic stratospheric temperatures

The diurnal variations of radiosonde temperature data for Narsarssuak (BW‐1) Greenland, from 1946–1948 are inspected and compared with data for Thule, Alert, Eureka and Resolute. Observations were taken at BW‐1 at local noon and midnight. In winter and spring the stratospheric temperatures there show a tendency for the difference, noon minus midnight, to diminish or even become negative. Similar patterns for apparent night warming in the lower stratosphere are found also at the other stations. The eight years of more recent and reliable arctic data which now exist should be made available to help determine the reality of this anomaly. Adiabatic semi‐diurnal vertical motions required to produce the observed night warming amount to 1 or 2 cm/sec. It is suggested that atmospheric tides may be a contributing cause.