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Possible artifacts of data biases in the recent global surface warming hiatus
Much study has been devoted to the possible causes of an apparent decrease in the upward trend of global surface temperatures since 1998, a phenomenon that has been dubbed the global warming \"hiatus.\" Here, we present an updated global surface temperature analysis that reveals that global trends are higher than those reported by the Intergovernmental Panel on Climate Change, especially in recent decades, and that the central estimate for the rate of warming during the first 15 years of the 21st century is at least as great as the last half of the 20th century. These results do not support the notion of a \"slowdown\" in the increase of global surface temperature.
Journal Article
سيد الأشباح كارل ماركس : (قراءة معاصرة)
يتناول شتاينفيلد بالحديث تكرارا ومرارا التطور الحالي للرأسمالية ممزوجة بمهارة مع قراءة دقيقة للنصوص الأصلية- وتحليل المكاتبات الخاصة بالتشخيصات والتوقعات الماركسية. لقد تغير الوضع بشكل جذري بالنسبة لأوروبا وغيرها من المناطق الغنية فيذكر : \"في أغلب الأحيان يكفي تتبع مسارات الإنتاج للسلع الاستهلاكية حتى البداية حيث نقطة الانطلاق كي نقابل الوجه المظلم من الثروة العالمية. وبالطبع يشعر المحظوظون من لهم فرصة عمل في مجالات الازدهار والرفاهية، أنهم لم يعودا بالضرورة يستغلون (من قبل صاحب العمل) : قد يكون لدى المستخدم في مرحلة ما فكرة أن رب العمل يكسب من ناتج عمله أكثر مما يكسبه هو نفسه. في هذه الحالة سيقوم المستخدم بتحديد تطلعه لزيادة أجر العمل في ظل الشروط المحددة مسبقا. لكنه بذلك لا يفلت من الاستغلال بالطبع، فعلى الأقل بالنسبة للكثير من الناس، يكون الاستغلال محجوبا من خلال حرية الاختيار\".
Book
Percentile indices for assessing changes in heavy precipitation events
Many climate studies assess trends and projections in heavy precipitation events using precipitation percentile (or quantile) indices. Here we investigate three different percentile indices that are commonly used. We demonstrate that these may produce very different results and thus require great care with interpretation. More specifically, consideration is given to two intensity-based indices and one frequency-based index, namely (a) all-day percentiles, (b) wet-day percentiles, and (c) frequency indices based on the exceedance of a percentile threshold. Wet-day percentiles are conditionally computed for the subset of wet events (with precipitation exceeding some threshold, e.g. 1 mm/d for daily precipitation). We present evidence that this commonly used methodology can lead to artifacts and misleading results if significant changes in the wet-day frequency are not accounted for. Percentile threshold indices measure the frequency of exceedance with respect to a percentile-based threshold. We show that these indices yield an assessment of changes in heavy precipitation events that is qualitatively consistent with all-day percentiles, but there are substantial differences in quantitative terms. We discuss the reasons for these effects, present a theoretical assessment, and provide a series of examples using global and regional climate models to quantify the effects in typical applications. Application to climate model output shows that these considerations are relevant to a wide range of typical climate-change applications. In particular, wet-day percentiles generally yield different results, and in most instances should not be used for the impact-oriented assessment of changes in heavy precipitation events.
Journal Article
Atmospheric Pollutant Dispersion over Complex Terrain: Challenges and Needs for Improving Air Quality Measurements and Modeling
Pollutant dispersion processes over complex terrain are much more complicated than over flat areas, as they are affected by atmospheric interactions with the orography at different spatial scales. This paper reviews recent findings and progress in this field, focusing on both experimental and modeling perspectives. It highlights open questions and challenges to our capability for better understanding and representing atmospheric processes controlling the fate of pollutants over mountainous areas. In particular, attention is focused on new measurement techniques for the retrieval of spatially distributed turbulence information and air quality parameters, and on challenges for meteorological and dispersion models to reproduce fine-scale processes influenced by the orography. Finally, specific needs in this field are discussed, along with possible directions for future research efforts.
Journal Article
التسامح بين شرق وغرب : دراسات في التعايش والقبول بالآخر
يتناول كتاب \"التسامح بين شرق وغرب : دراسات في التعايش والقبول بالآخر\" والذي قام بتأليفه \"سمير الخليل\" وترجمه \"إبراهيم العريس\" في حوالي (127) صفحة من القطع المتوسط موضوع (التسامح بين الشرق والغرب)،اعتبار التسامح في البلدان الديمقراطية أمرا مسلما به، إذ ينظر إلى الفرد مهما اختلف شكلا وسلوكا ولغة، بعين القبول، كما يتوقع منه أن يفعل الشيء نفسه. فإذا ظهر أي ضغط يهدد بتغيير هذا الموقف، اعتبر الأمر خرقا ينطوي على تدمير لحرية الفرد. فنحن نتسامح مع الآخرين ونقبل ما يفعلونه، ما دام إن ذلك لا يرتب أضرارا تصيب المجتمع وأفراده. ذلك إن الاختلاف لا يخلق موقفا يقود إلى التعصب والتقوقع، أما التسامح فمسؤولية حضارية وواحد من حقوق الإنسان. ولئن أدى التقوقع إلى الحؤول دون الاندماج في المجتمع الغريب، يبقى لافتا للنظر أن تخلو الثقافة العربية، السياسي منها والاجتماعي، من مقولة التسامح كلمة وممارسة. لقد لعبت الأيديولوجيات النضالية والقيم السلفية أدوارها في طرد التسامح من حياتنا وثقافتنا. هذا الكتاب يطل على مسألة في العالم الغربي وعند العرب سواء بسواء.
BOOK
Interannual variability of terpenoid emissions in an alpine city
Terpenoid emissions above urban areas are a complex mix of biogenic and anthropogenic emission sources. In line with previous studies we found that summertime terpenoid fluxes in an alpine city were dominated by biogenic sources. Inter-seasonal emission measurements revealed consistency for monoterpenes and sesquiterpenes but a large difference in isoprene between the summers of 2015 and 2018. Standardized emission potentials for monoterpenes and sesquiterpenes were 0.12 nmol m−2 s−1 and 3.0×10-3 nmol m−2 s−1 in 2015 and 0.11 nmol m−2 s−1 and 3.4×10-3 nmol m−2 s−1 in 2018, respectively. Observed isoprene fluxes were almost 3 times higher in 2018 than in 2015. This factor decreased to 2.3 after standardizing isoprene fluxes to 30 ∘C air temperature and photosynthetic active radiation (PAR) to 1000 µmol m−2 s−1. Based on emission model parameterizations, increased leaf temperatures can explain some of these differences, but standardized isoprene emission potentials remained higher in 2018 when a heat wave persisted. These data suggest a higher variability of interannual isoprene fluxes than for other terpenes. Potential reasons for the observed differences such as emission parameterization, footprint changes, water stress conditions, and tree trimming are investigated.
Journal Article
Deciphering anthropogenic and biogenic contributions to selected non-methane volatile organic compound emissions in an urban area
The anthropogenic and biogenic contributions of isoprene, monoterpenes, sesquiterpenes and methanol in an urban area were estimated based on direct eddy covariance flux observations during four campaigns between 2018 and 2021. While these compounds are typically thought to be dominated by biogenic sources on regional and global scales, the role of potentially significant anthropogenic emissions in urban areas has been recently debated. Typical fluxes of isoprene, monoterpenes and sesquiterpenes were on the order of 0.07 ± 0.02, 0.09 and 0.003 nmol m−2 s−1 during spring. During summer, emission fluxes of isoprene, monoterpenes and sesquiterpenes were higher on the order of 0.85 ± 0.09, 0.11 and 0.004 nmol m−2 s−1. It was found that the contribution of the anthropogenic part is strongly seasonally dependent. For isoprene, the anthropogenic fraction can be as high as 64 % in spring but is typically very low < 18 % during the summer season. For monoterpenes, the anthropogenic fraction was estimated to be between 43 % in spring and less than 20 % in summer. With values of 2.8 nmol m−2 s−1 in spring and 3.2 nmol m−2 s−1 in summer, methanol did not exhibit a significant seasonal variation of observed surface fluxes. However, there was a difference in emissions between weekdays and weekends (about 2.3 times higher on weekdays in spring). This suggests that methanol emissions are likely influenced by anthropogenic activities during all seasons.
Journal Article
Changes in Intense Precipitation over the Central United States
In examining intense precipitation over the central United States, the authors consider only days with precipitation when the daily total is above 12.7 mm and focus only on these days and multiday events constructed from such consecutive precipitation days. Analyses show that over the central United States, a statistically significant redistribution in the spectra of intense precipitation days/events during the past decades has occurred. Moderately heavy precipitation events (within a 12.7–25.4 mm day−1range) became less frequent compared to days and events with precipitation totals above 25.4 mm. During the past 31 yr (compared to the 1948–78 period), significant increases occurred in the frequency of “very heavy” (the daily rain events above 76.2 mm) and extreme precipitation events (defined as daily and multiday rain events with totals above 154.9 mm or 6 in.), with up to 40% increases in the frequency of days and multiday extreme rain events. Tropical cyclones associated with extreme precipitation do not significantly contribute to the changes reported in this study. With time, the internal precipitation structure (e.g., mean and maximum hourly precipitation rates within each preselected range of daily or multiday event totals) did not noticeably change. Several possible causes of observed changes in intense precipitation over the central United States are discussed and/or tested.
Journal Article