Abstract: The biogeochemical sulfur cycle is intimately linked to the cycles of carbon, iron, and oxygen, and plays an important role in global climate via weathering reactions and aerosols. However, many aspects of the modern budget of the global sulfur cycle are not fully understood. We present new S measurements on sulfate from more than 160 river samples from different geographical and climatic regions—more than 46% of the world's freshwater flux to the ocean is accounted for in this estimate of the global riverine sulfur isotope budget. These measurements include major rivers and their tributaries, as well as time series, and are combined with previously published data to estimate the modern flux-weighted global riverine S as 4.4 ± 4.5‰ (V-CDT), and 4.8 ± 4.9‰ when the most polluted rivers are excluded. The sulfur isotope data, when combined with major anion and cation concentrations, allow us to tease apart the relative contributions of different processes to the modern riverine sulfur budget, resulting in new estimates of the flux of riverine sulfate due to the oxidative weathering of pyrites (1.3 ± 0.2 Tmol S/y) and the weathering of sedimentary sulfate minerals (1.5 ± 0.2 Tmol S/y). These data indicate that previous estimates of the global oxidative weathering of pyrite have been too low by a factor of two. As pyrite oxidation coupled to carbonate weathering can act as a source of CO2 to the atmosphere, this global pyrite weathering budget implies that the global CO2 weathering sink is overestimated. Furthermore, the large range of sulfur isotope ratios in modern rivers indicates that secular changes in the lithologies exposed to weathering through time could play a major role in driving past variations in the S value of seawater.

Abstract: Gradual warming and changes in extreme weather patterns associated with human induced climate change are altering the range distributions of species. However, species responses to climate change are predicted to be more strongly affected by extreme events than by changes in mean values. As a result, measuring species' responses to extreme events in addition to the mean changes in climate are necessary to predict species range limits under future conditions. This study examines the impacts of a cold spell in southern Florida on native and an introduced oil-collecting bees by examining the bees' interactions with two native plants species. Our results provide evidence of differential impacts from an extreme cold event on a native, subtropical bee vs. an introduced, tropical bee. Specifically, the cold spell had little impact on the abundance of the native bee, while the abundance of the introduced, tropical bee was negatively impacted. Our findings demonstrate that extreme cold spells are important climate change-related phenomena that can have strong impacts on tropical species distributions and abundances, especially at the threshold of their thermal tolerances. Our approach also provided a rare opportunity to examine these impacts on multiple interacting species, which provides a more realistic assessment of the potential impacts of climate change.

Abstract: BACKGROUND: Air pollution is increasingly recognized as a risk factor for acute exacerbation of chronic obstructive pulmonary disease (COPD). Changing climate and weather patterns can modify the levels and types of air pollutants. For example, dust outbreaks increase particulate air pollution. OBJECTIVE: This paper examines the effect of Saharan dust storms on the concentration of coarse particulate matter in Miami, and its association with the risk of acute exacerbation of COPD (AECOPD). METHODS: In this prospective cohort study, 296 COPD patients (with 313 events) were followed between 2013 and 2016. We used Light Detection and Ranging (LIDAR) and satellite-based Aerosol Optical Depth (AOD) to identify dust events and quantify particulate matter (PM) exposure, respectively. Exacerbation events were modeled with respect to location- and time-lagged dust and PM exposures, using multivariate logistic regressions. MEASUREMENTS AND MAIN RESULTS: Dust duration and intensity increased yearly during the study period. During dust events, AOD increased by 51% and particulate matter </=2.5 microm in aerodynamic diameter (PM2.5) increased by 25%. Adjusting for confounders, ambient temperature and local PM2.5 exposure, one-day lagged dust exposure was associated with 4.9 times higher odds of two or more (2+ hereto after) AECOPD events (odds ratio = 4.9; 95% CI = 1.8-13.4; p < 0.001). Ambient temperature exposure also showed a significant association with 2+ and 3+ AECOPD events. The risk of AECOPD lasted up to 15 days after dust exposure, declining from 10x higher on day 0 to 20% higher on day 15. CONCLUSIONS: Saharan dust outbreaks observed in Miami elevate the concentration of PM and increase the risk of AECOPD in COPD patients with recurring exacerbations.

Abstract: A multiscale atmospheric/oceanic model system with unified physics, the Global/Regional Integrated Model system (GRIMs) has been created for use in numerical weather prediction, seasonal simulations, and climate research projects, from global to regional scales. It includes not only the model code, but also the test cases and scripts. The model system is developed and practiced by taking advantage of both operational and research applications. This article outlines the history of GRIMs, its current applications, and plans for future development, providing a summary useful to present and future users.

Abstract: Climate variability leads to economic and food security risks throughout the world because of its major influences on agriculture. Accurate forecasts of climate 3-6 months ahead of time can potentially allow farmers and others in agriculture to make decisions to reduce unwanted impacts or take advantage of expected favorable climate. However, potential benefits of climate forecasts vary considerably because of many physical, biological, economic, social, and political factors. The purpose of this study was to estimate the potential economic value of climate forecasts for farm scale management decisions in one location in the Southeast USA (Tifton, GA; 31 degrees 23'N; 83 degrees 31'W) for comparison with previously-derived results for the Pampas region of Argentina. The same crops are grown in both regions but at different times of the year. First, the expected value of tailoring crop mix to El Nino-Southern Oscillation (ENSO) phases for a typical farm in Tifton was estimated using crop models and historical daily weather data. Secondly, the potential values for adjusting management of maize (Zea maize L.) to different types of climate forecasts (perfect knowledge of (a) ENSO phase, (b) growing season rainfall categories, and (c) daily weather) were estimated for Tifton and Pergamino, Argentina (33 degrees 55'S; 60 degrees 33'W). Predicted benefits to the farm of adjusting crop mix to ENSO phase averaged from US$ 3 to 6 ha-1 over all years, depending on the farmer's initial wealth and aversion to risk. Values calculated for Argentina were US$ 9-15 for Pergamino and up to US$ 35 for other locations in the Pampas. Varying maize management by ENSO phase resulted in predicted forecast values of US$ 13 and 15 for Tifton and Pergamino, respectively. The potential value of perfect seasonal forecasts of rainfall tercile on maize profit was higher than for ENSO-based forecasts in both regions (by 28% in Tifton and 70% in Pergamino). Perfect knowledge of daily weather over the next season provided an upper limit on expected value of about US$ 190 ha-1 for both regions. Considering the large areas of field crop production in these regions, the estimated economic potential is very high. However, there are a number of challenges to realize these benefits. These challenges are generally related to the uncertainly of climate forecasts and to the complexities of agricultural systems.

Abstract: A preliminary investigation into the impact of dropsonde observations from the Global Hawk (GH) on tropical and extratropical forecasts is performed using the National Centers for Environmental Prediction (NCEP) Global Data Assimilation System (GDAS). Experiments are performed during high-impact weather events that were sampled as part of the NOAA Unmanned Aerial Systems (UAS) Sensing Hazards with Operational Unmanned Technology (SHOUT) field campaigns in 2016: 1) three extratropical systems in February 2016 and 2) Hurricanes Matthew and Nicole in the western Atlantic. For these events, the benefits of GH observations under a satellite data gap scenario are also investigated. It is found that the assimilation of GH dropsondes reduces the track error for both Matthew and Nicole; the improvements are as high as 20% beyond 60 h. Additionally, the localized dropsondes reduce global forecast track error for four tropical cyclones by up to 9%. Results are mixed under a satellite gap scenario, where only Hurricane Matthew is improved from assimilated dropsondes. The improved storm track is attributed to a better representation of the steering flow and atmospheric midlevel pattern. For all cases, dropsondes reduce the root-mean-square error in temperature, relative humidity, wind, and sea level pressure by 3%-8% out to 96 h. Additional benefits from GH dropsondes are obtained for precipitation, with higher skill scores over the southeastern United States versus control forecasts of up to 8%, as well as for low-level parameters important for severe weather prediction. The findings from this study are preliminary and, therefore, more cases are needed for statistical significance.

Abstract: Carbonate mineral weathering coupled with aquatic photosynthesis on the continents, herein termed coupled carbonate weathering (CCW), represents a current atmospheric CO2 sink of about 0.5 Pg C/a. Because silicate mineral weathering has been considered the primary geological CO2 sink, CCW's role in the present carbon cycle has been neglected. However, CCW may be helping to offset anthropogenic atmospheric CO2 increases as carbonate minerals weather more rapidly than silicates. Here we provide an overview of atmospheric CO2 uptake by CCW and its impact on global carbon cycling. This overview shows that CCW is linked to climate and land-use change through changes in the water cycle and water-born carbon fluxes. Projections of future changes in carbon cycling should therefore include CCW as linked to the global water cycle and land-use change.

Abstract: Frost, extreme high temperatures, dry spells, and other weather extremes influence crop development, often causing major variations in yield from one season to the next. Selected growth stages such as flowering and grain filling are particularly sensitive to temperature and/or precipitation extremes and farmers are often unable to manage this risk. Crop simulation models have matured into powerful tools for identifying strategies in fully utilizing scarce natural resources under variable climate conditions. However, the use of crop models often requires expert knowledge and an extensive number of input datasets. Combining the power of Internet, computing technology, and web-based decision-support tools is becoming increasingly popular in situations where these requirements cannot be met. The objective of this study is to develop a simple decision-support tool that combines freely available information with the functionality of complex crop models in a user friendly interface for real-time assessment of soil, plant, and weather information. The resulting tool is intended to be used ahead of the growing season by producers, and it enables the estimation and minimization of the likelihood of extreme weather events during critical stages of crop development.