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• Higher latitudes regions will witness a high soil NO 3 – production. • Frequent freeze–thaw process may accelerate the soil NO 3 – production. • Soil NO 3 – may reach 18 mg/l concentration during winter only in future. Winter season is characterized by lowering of air temperature and soil temperature, and deceleration of soil nitrogen cycle. Despite low soil temperature, soil NO 3 – is found on the soil surface and in the streams of temperate and higher latitude regions towards the end of winter season. With the rise in global air temperature, the soil temperature is expected to warm up accordingly. Plausible effects of future soil temperature changes in affecting the production and movement of soil NO 3 – within a vertical profile were studied in the present paper. Four Representative Concentration Pathways (RCP) scenarios were considered to estimate the effects of change in air temperature on soil temperature at different depths within a vertical profile and on the soil nitrate status. Since winter season is known to have low to no soil nitrate utilization (due to microbial inactivity and low utilization by biomass), plausible effects of winter warming in the future decades were studied. The occurrence and movement of soil NO 3 – during winter, raises a concern regarding the future warming climate's response. Long-term records from Hubbard Brook Experimental Forest, New Hampshire, USA, were used for observation, calibration, and validation purposes. Non-linear relationship between air temperature, soil moisture, soil temperature, and soil NO 3 – status at different soil depths, were assessed using support vector regression (SVR) models. Soil temperature and soil NO 3 – status at different soil depths were predicted using SVR models, under the four different RCP scenarios. The projections under different RCP scenarios suggested - significant production of soil NO 3 – during winter (approx. 18 mg/l by the year 2095 under a "business as usual" scenario), and movement of soil NO 3 – towards soil surface before the beginning of plant-growing season. [ABSTRACT FROM AUTHOR]

Scaling up of observed point data to estimate regional carbon fluxes is an important issue in the context of the global terrestrial carbon cycle. In this study, the authors proposed a new model to scale up the eddy covariance data to estimate regional carbon fluxes using satellite-derived data. Gross primary productivity (GPP) and ecosystem respiration (RE) were empirically calculated using the normalized difference vegetation index (NDVI) and land surface temperature (LST) from the Moderate Resolution Imaging Spectroradiometer (MODIS). First, the model input is evaluated by comparing with the field data, then established and tested the model at the point scale, and then extended it into a regional scale. At the point scale, the empirical model could reproduce the seasonal and interannual variations in the carbon budget of the mature black spruce forests in Alaska and Canada sites, suggesting that seasonality of the NDVI and LST could explain the carbon fluxes and that the model is robust within mature black spruce forests in North America. Regional-scale analysis showed that the total GPP and RE between 2003 and 2006 were 1.76 ± 0.28 and 1.86 ± 0.26 kg CO2 m−2 yr−1, respectively, in mature black spruce forests in Alaska, indicating that these forests were almost carbon neutral. The authors' model analysis shows that the proposed method is effective in scaling up point observations to estimate the regional-scale carbon budget and that the mature black spruce forests increased in sink strength during spring warming and decreased in sink strength during summer and autumn warming. [ABSTRACT FROM AUTHOR]

The article discusses a study which examined current methane emission and its controlling factors on Alaskan tundra, as well as spatial and temporal differences in methane flux. The study was conducted from mid-June through the end of August 1993 in Barrow, Alaska, while at Happy Valley it was conducted between early June and late August 1995. A gradient method based on the Monin-Obukhov similarity theory was used in this study to determine methane flux. Results of the study showed that 1.85 parts per million (ppm) was the average methane concentration at Happy Valley, while the atmospheric methane concentration at Barrow Station was less than 1.85ppm. Included is a chart showing seasonal changes of daily amount of methane flux and soil temperatures.

Climate change is expected to adversely impact crop productivity and forest stocks of the planet, which will pose food security challenges and complicate carbon mitigation goals. This paper asks in what ways warming temperatures may affect the ability of REDD+ programs to sequester carbon and support rural livelihoods. An example from the forest-rich central Himalayan region of India is used for modeling the implications of crop productivity decline on land use change decisions. Local communities derive their livelihoods through multiple avenues including forestry and farming. When faced with warming-led declining crop productivity, communities may find it attractive to enroll farmland into REDD+ programs. However, a reduced biomass growth rate due to increasing temperatures and declining precipitation would also lower the benefits from REDD+ participation, thereby delaying the timing of irreversible land use decisions. Results suggest that while higher carbon prices and declining crop incomes incentivize early farmland conversion into forests, a lower biomass growth rate discourages REDD+ enrolment. If communities are allowed fuelwood harvesting from forests, it could make land enrollment into REDD+ more attractive, leading to early conversion. However, the value of fuelwood to the communities plays a crucial role in determining the timing of REDD+ participation. When fuelwood is less scarce, warming will delay enrollment into REDD+ schemes. Whereas, when fuelwood is valuable to the community, early afforestation becomes an attractive option. • A model of land use under REDD+ where warming causes crop and biomass losses. • explores attractiveness of REDD+ to forest communities of Uttarakhand in India. • warming led crop productivity loss prompts early enrolment of farmland into REDD+. • biomass growth rate decline due to warming delays REDD+ participation. • higher fuelwood scarcity and lower farm incomes promote early afforestation. [ABSTRACT FROM AUTHOR]

Even with ever-increasing societal interest in tornado activities engendering catastrophes of loss of life and property damage, the long-term change in the geographic location and environment of tornado activity centers over the last six decades (1954–2018), and its relationship with climate warming in the U.S., is still unknown or not robustly proved scientifically. Utilizing discriminant analysis, we show a statistically significant geographic shift of U.S. tornado activity center (i.e., Tornado Alley) under warming conditions, and we identify five major areas of tornado activity in the new Tornado Alley that were not identified previously. By contrasting warm versus cold years, we demonstrate that the shift of relative warm centers is coupled with the shifts in low pressure and tornado activity centers. The warm and moist air carried by low-level flow from the Gulf of Mexico combined with upward motion acts to fuel convection over the tornado activity centers. Employing composite analyses using high resolution reanalysis data, we further demonstrate that high tornado activities in the U.S. are associated with stronger cyclonic circulation and baroclinicity than low tornado activities, and the high tornado activities are coupled with stronger low-level wind shear, stronger upward motion, and higher convective available potential energy (CAPE) than low tornado activities. The composite differences between high-event and low-event years of tornado activity are identified for the first time in terms of wind shear, upward motion, CAPE, cyclonic circulation and baroclinicity, although some of these environmental variables favorable for tornado development have been discussed in previous studies. [ABSTRACT FROM AUTHOR]

Paris Agreement's 1.5 °C or 2.0 °C global warming targets call for human concerns on warming climate on human society and environment in general. Here we analyzed spatiotemporal patterns and related impacts of precipitation extremes on human society across China using NEX-GDDP (NASA Earth Exchange Global Daily Downscaled Projections) dataset. We found increasing trends of almost all extreme precipitation indices except consecutive dry duration (CDD). Additional 0.5 °C warmer climate from 1.5 °C to 2.0 °C global warming targets can double increase of extreme precipitation indices. Specifically, the increase of Rx5day (Max 5-day precipitation amount) is from 3.98% to 7.63%, the increase of R95pTOT (precipitation in very wet days) is from 19.41% to 34.42% and the increase of PRCPTOT (annual total wet-day precipitation) is from 3.89% to 8.23%, showing that additional 0.5 °C warmer climate can potentially increase flood risks across China. While, we also found regional differences in responses of extreme precipitation to warming climate. Extreme precipitation in the Qinghai Tibet Plateau, the Western Arid and semiarid zone and in the lower Yangtze River basin is in higher sensitivity to warming climate. Constraint of temperature increase of below 1.5 °C but not 2.0 °C will avoid 4.34% to 73.96% impacts of extreme precipitation on human society. It is particularly important for China since that more than half of territory of China is under exposure to high flood and drought disasters. Unlabelled Image • We made first attempt to quantify changes in seasonal extreme precipitation in a 1.5 °C/2.0 °C warmer climate in China. • We found double increase of extreme precipitation in an addition 0.5 °C warmer climate. • We found intensified precipitation processes reflected by shorter return period of extreme precipitation event. [ABSTRACT FROM AUTHOR]

Maintaining high double rice productivity in China is very important for ensuring the food security of China. However, the double rice production system is sensitive to changes in both climate and management practices. Previous studies showed that rice production has been negatively impacted by global warming without considering the changes of cultivars and management practices. However, cultivar improvements and the impact of cultivar change must not be ignored in any assessment. In the current study, we combined data analysis with crop modeling to investigate the impacts of changes in climate and cultivars on rice productivity at three different double rice sites (Nanchang, Hengyang, and Gaoyao) in China. The results showed a warming trend at the study sites during 1981–2009, and the temperature increase rates (maximum, average, and minimum temperatures) in the late rice growing season were larger than in the early rice growing season. Global warming has led to a reduction in the length of the rice growth period. Adopting new rice cultivars may partially mitigate the declining trend of the growing duration and grain yield, but it would not completely compensate for the negative impact observed in double rice regions. In general, the changes in cultivars prolonged the growing duration by increasing the basic vegetative phase and the photoperiod formation phase. The main reasons for yield improvement were the increase in the percentage of filled grains for early rice and the increase in grain number per spike for late rice. In the face of future warming, breeding efforts are necessary for producing new cultivars that are resilient to the negative impacts of future climate change on agriculture. [ABSTRACT FROM AUTHOR]