• Energy Research

The well-documented energy balance dynamics within forest ecosystems are poorly implemented in studies of the biophysical effects of forests. This results in limitations to the accurate quantification of forest cooling/warming on local air temperature. Taking into consideration the forest air space, this study proposes a three-layered (canopy, forest air space and soil [CAS]) land surface energy balance model to simulate air temperature within forest spaces (Taf) and subsequently to evaluate its biophysical effects on forest cooling/warming, i.e., the air temperature gradient (∆Ta) between the Taf and air temperature of open spaces (Tao) (∆Ta = Taf - Tao). We test the model using field data for 23 sites across 10 cities worldwide; the model shows satisfactory performance with the test data. High-latitude forests show greater seasonal dynamics of ∆Ta, generating considerable cooling of local air temperatures in warm seasons but minimal cooling or even warming effects during cool seasons, while low-latitude tropical forests always exert cooling effects with less interannual variability. The interannual dynamics of ∆Ta are significantly related to the seasonality of solar geometry and canopy leaf phenology. The differences between forest canopy temperature (Tc) and Tao, which are the two most important terms attributed by the CAS model in impacting Taf, explain a large part of forest cooling and warming (May-July: R2 = 0.35; November-January: R2 = 0.51). The novel CAS model provides a feasible way to represent the energy balance within forest ecosystems and to assess its impacts on local air temperatures globally.

The 2015/16 El Niño brought severe drought and record-breaking temperatures in the tropics. Here, using satellite-based L-band microwave vegetation optical depth, we mapped changes of above-ground biomass (AGB) during the drought and in subsequent years up to 2019. Over more than 60% of drought-affected intact forests, AGB reduced during the drought, except in the wettest part of the central Amazon, where it declined 1 y later. By the end of 2019, only 40% of AGB reduced intact forests had fully recovered to the predrought level. Using random-forest models, we found that the magnitude of AGB losses during the drought was mainly associated with regionally distinct patterns of soil water deficits and soil clay content. For the AGB recovery, we found strong influences of AGB losses during the drought and of γ . γ is a parameter related to canopy structure and is defined as the ratio of two relative height (RH) metrics of Geoscience Laser Altimeter System (GLAS) waveform data—RH25 (25% energy return height) and RH100 (100% energy return height; i.e., top canopy height). A high γ may reflect forests with a tall understory, thick and closed canopy, and/or without degradation. Such forests with a high γ ( γ ≥ 0.3) appear to have a stronger capacity to recover than low- γ ones. Our results highlight the importance of forest structure when predicting the consequences of future drought stress in the tropics.

Although it's well known that the carbon intensity from passenger transport of cities varies widely, few studies assessed the disparities of that in city-level and its underlying factors due to the limited availability of data, and thus developed effective strategies for different types of cities. This study is the first to present a comprehensive inventory of emissions from passenger transport on road for 360 cities in mainland China for 2018, based on the data from 5 transport modes and evaluated by combining distance-based and top-down fuel-based methods. In 2018, passenger transport on road in China emitted 1076 MtC. A large portion of CO2 emissions was identified in the southern and eastern coastal areas and capital cities. GDP, population, and policy were the major factors determining the total CO2 emissions, but not carbon intensity. Clustering analysis of carbon intensity and 9 socio-economic predictors, using a tree-based regression model, clustered the 360 cities into 6 groups and showed that higher carbon intensities occurred in both affluent city groups with a high active population share and less affluent city groups with a low population density but high density of trip destinations. Forward-and-backward stepwise multiple regression analysis indicated that constructing a compact city is more effective for city groups with a high income and high active population share. Enhancing land-use mixed degree is more critical for city groups with a high income and low active population share, while shortening travel distance by intensifying infrastructure construction is more important for the less affluent city groups.

AbstractThe extreme dry and hot 2015/16 El Niño episode caused large losses in tropical live aboveground carbon (AGC) stocks. Followed by climatic conditions conducive to high vegetation productivity since 2016, tropical AGC are expected to recover from large losses during the El Niño episode; however, the recovery rate and its spatial distribution remain unknown. Here, we used low‐frequency microwave satellite data to track AGC changes, and showed that tropical AGC stocks returned to pre‐El Niño levels by the end of 2020, resulting in an AGC sink of Pg C year−1 during 2014–2020. This sink was dominated by strong AGC increases ( Pg C year−1) in non‐forest woody vegetation during 2016–2020, compensating the forest AGC losses attributed to the El Niño event, forest loss, and degradation. Our findings highlight that non‐forest woody vegetation is an increasingly important contributor to interannual to decadal variability in the global carbon cycle.

To limit global temperature rise, scientists have proposed significant potentials for climate change mitigation from protecting and managing natural systems. However, depending on the time taken for technology deployment and natural carbon gain, actual mitigation can be dramatically delayed, and total mitigation by 2030 or 2050 can be more than halved compared to the estimated potential. Delayed or lack of action on implementation would push back the timeline to reduce greenhouse gas emissions, largely undermining the Paris goals. Launching actions now and learning from past experience can help deliver climate mitigation and sustainable development goals.

En tant que l'un des plus grands émetteurs de gaz à effet de serre au monde, la Chine s'est fixé l'objectif ambitieux d'atteindre le pic de carbone et la neutralité carbone. Par conséquent, il est crucial de quantifier l'ampleur et la tendance des sources et des puits de dioxyde de carbone atmosphérique (CO2), et de suivre les progrès de la Chine vers ces objectifs. À l'aide d'ensembles de données et de modèles de pointe, cette étude a estimé de manière exhaustive les émissions anthropiques de CO2 provenant de l'énergie, des processus industriels et de l'utilisation des produits, ainsi que des déchets, des sources naturelles et des puits de CO2 pour toute la Chine au cours de la période 1980-2021. Pour reconnaître les différences entre les différentes méthodes d'estimation des émissions de gaz à effet de serre, les estimations sont comparées aux inventaires nationaux de gaz à effet de serre (INGES) de la Chine pour 1994, 2005, 2010, 2012 et 2014. Les émissions anthropiques de CO2 en Chine ont été multipliées par 7,39 entre 1980 et 2021, passant à 12,77 Gt CO2 a-1. Tout en bénéficiant de projets écologiques (par exemple, le Three Norths Shelter Forest System Project), le puits de carbone terrestre en Chine a atteint 1,65 Gt de CO2 a-1 en moyenne entre 2010 et 2021, soit près de 15,81 fois celui du puits de carbone des années 1980. En moyenne, les écosystèmes terrestres de la Chine ont compensé 14,69 % ± 2,49 % des émissions anthropiques de CO2 jusqu'en 2010-2021. Deux régions administratives de niveau provincial de la Chine, Xizang et Qinghai, ont atteint la neutralité carbone selon nos estimations, mais près de la moitié des régions administratives de la Chine ont des compensations de puits de carbone terrestres de moins de 10% des émissions anthropiques de CO2. Cette étude a indiqué un niveau élevé de cohérence entre les NGHGI et divers ensembles de données utilisés pour estimer les émissions de CO2 d'origine fossile, mais a révélé des différences notables pour les puits de carbone terrestres. Les estimations futures des puits de carbone terrestres des NGHGI doivent être vérifiées de toute urgence avec des modèles basés sur les processus qui intègrent les processus complets du cycle du carbone. Como uno de los mayores emisores de gases de efecto invernadero del mundo, China se ha fijado el ambicioso objetivo de alcanzar el pico de carbono y la neutralidad de carbono. Por lo tanto, es crucial cuantificar la magnitud y la tendencia de las fuentes y sumideros de dióxido de carbono atmosférico (CO2), y monitorear el progreso de China hacia estos objetivos. Utilizando conjuntos de datos y modelos de vanguardia, este estudio estimó exhaustivamente las emisiones antropogénicas de CO2 de la energía, los procesos industriales y el uso de productos, y los desechos junto con las fuentes naturales y los sumideros de CO2 para toda China durante 1980-2021. Para reconocer las diferencias entre los diversos métodos de estimación de las emisiones de efecto invernadero, las estimaciones se comparan con los Inventarios Nacionales de Gases de Efecto Invernadero (GEI) de China para 1994, 2005, 2010, 2012 y 2014. Las emisiones antropogénicas de CO2 en China han aumentado 7,39 veces desde 1980 a 12,77 Gt CO2 a-1 en 2021. Si bien se beneficia de proyectos ecológicos (por ejemplo, Three Norths Shelter Forest System Project), el sumidero de carbono terrestre en China ha alcanzado un promedio de 1.65 Gt CO2 a-1 entre 2010 y 2021, que es casi 15.81 veces mayor que el sumidero de carbono en la década de 1980. En promedio, los ecosistemas terrestres de China compensaron el 14,69% ± 2,49% de las emisiones antropogénicas de CO2 entre 2010 y 2021. Según nuestras estimaciones, dos regiones administrativas a nivel provincial de China, Xizang y Qinghai, han logrado la neutralidad de carbono, pero casi la mitad de las regiones administrativas de China tienen compensaciones de sumideros de carbono terrestres de menos del 10% de las emisiones antropogénicas de CO2. Este estudio indicó un alto nivel de consistencia entre los INGH y varios conjuntos de datos utilizados para estimar las emisiones fósiles de CO2, pero encontró diferencias notables para los sumideros de carbono terrestres. Las estimaciones futuras de los sumideros de carbono terrestre de los GEI deben verificarse urgentemente con modelos basados en procesos que integren los procesos integrales del ciclo del carbono. باعتبارها واحدة من أكبر الدول المسببة لانبعاثات غازات الدفيئة في العالم، وضعت الصين لنفسها هدفًا طموحًا يتمثل في تحقيق ذروة الكربون وحياد الكربون. لذلك، من الأهمية بمكان تحديد حجم واتجاه مصادر ومصارف ثاني أكسيد الكربون في الغلاف الجوي (CO2)، ومراقبة تقدم الصين نحو هذه الأهداف. باستخدام أحدث مجموعات البيانات والنماذج، قدرت هذه الدراسة بشكل شامل انبعاثات ثاني أكسيد الكربون البشرية المنشأ من الطاقة والعمليات الصناعية واستخدام المنتجات والنفايات جنبًا إلى جنب مع المصادر الطبيعية ومصارف ثاني أكسيد الكربون في جميع أنحاء الصين خلال الفترة 1980-2021. للتعرف على الاختلافات بين الطرق المختلفة لتقدير انبعاثات غازات الدفيئة، تتم مقارنة التقديرات بقوائم الجرد الوطنية لغازات الدفيئة في الصين للأعوام 1994 و 2005 و 2010 و 2012 و 2014. زادت انبعاثات ثاني أكسيد الكربون البشرية المنشأ في الصين بمقدار 7.39 مرة من عام 1980 إلى 12.77 جيجا طن من ثاني أكسيد الكربون في عام 2021. مع الاستفادة من المشاريع البيئية (على سبيل المثال، مشروع نظام غابات المأوى في الشمال)، بلغ بالوعة الكربون في الصين 1.65 جيجا طن من ثاني أكسيد الكربون في المتوسط خلال الفترة 2010-2021، وهو ما يقرب من 15.81 ضعف بالوعة الكربون في الثمانينيات. في المتوسط، عوضت النظم الإيكولوجية الأرضية في الصين 14.69 ٪ ± 2.49 ٪ من انبعاثات ثاني أكسيد الكربون البشرية المنشأ خلال الفترة 2010-2021. حققت منطقتان إداريتان على مستوى المقاطعة في الصين، شيزانغ وتشينغهاي، حيادية الكربون وفقًا لتقديراتنا، ولكن ما يقرب من نصف المناطق الإدارية في الصين لديها تعويضات بالوعة الكربون الأرضية أقل من 10 ٪ من انبعاثات ثاني أكسيد الكربون البشرية المنشأ. أشارت هذه الدراسة إلى وجود مستوى عالٍ من الاتساق بين مؤشرات الغازات الدفيئة الوطنية ومجموعات البيانات المختلفة المستخدمة لتقدير انبعاثات ثاني أكسيد الكربون الأحفوري، ولكنها وجدت اختلافات ملحوظة في بالوعات الكربون الأرضية. هناك حاجة ماسة إلى التحقق من التقديرات المستقبلية لأحواض الكربون الأرضية الخاصة بالمصارف الصحية الوطنية من خلال النماذج القائمة على العمليات التي تدمج عمليات دورة الكربون الشاملة. As one of the world's largest emitters of greenhouse gases, China has set itself the ambitious goal of achieving carbon peaking and carbon neutrality. Therefore, it is crucial to quantify the magnitude and trend of sources and sinks of atmospheric carbon dioxide (CO2), and to monitor China's progress toward these goals. Using state-of-the-art datasets and models, this study comprehensively estimated the anthropogenic CO2 emissions from energy, industrial processes and product use, and waste along with natural sources and sinks of CO2 for all of China during 1980-2021. To recognize the differences among various methods of estimating greenhouse emissions, the estimates are compared with China's National Greenhouse Gas Inventories (NGHGIs) for 1994, 2005, 2010, 2012, and 2014. Anthropogenic CO2 emissions in China have increased by 7.39 times from 1980 to 12.77 Gt CO2 a-1 in 2021. While benefiting from ecological projects (e.g., Three Norths Shelter Forest System Project), the land carbon sink in China has reached 1.65 Gt CO2 a-1 averaged through 2010-2021, which is almost 15.81 times that of the carbon sink in the 1980s. On average, China's terrestrial ecosystems offset 14.69% ± 2.49% of anthropogenic CO2 emissions through 2010-2021. Two provincial-level administrative regions of China, Xizang and Qinghai, have achieved carbon neutrality according to our estimates, but nearly half of the administrative regions of China have terrestrial carbon sink offsets of less than 10% of anthropogenic CO2 emissions. This study indicated a high level of consistency between NGHGIs and various datasets used for estimating fossil CO2 emissions, but found notable differences for land carbon sinks. Future estimates of the terrestrial carbon sinks of NGHGIs urgently need to be verified with process-based models which integrate the comprehensive carbon cycle processes.