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1. Improved global wetland carbon isotopic signatures support post-2006 microbial methane emission increase

   https://doi.org/10.1038/s43247-022-00488-5  

   Oh, Youmi; Zhuang, Qianlai; Welp, Lisa R.; Liu, Licheng; Lan, Xin; Basu, Sourish; Dlugokencky, Edward J.; Bruhwiler, Lori; Miller, John B.; Michel, Sylvia E.; et al (December 2022, Communications Earth & Environment)

   Abstract Atmospheric concentrations of methane, a powerful greenhouse gas, have strongly increased since 2007. Measurements of stable carbon isotopes of methane can constrain emissions if the isotopic compositions are known; however, isotopic compositions of methane emissions from wetlands are poorly constrained despite their importance. Here, we use a process-based biogeochemistry model to calculate the stable carbon isotopic composition of global wetland methane emissions. We estimate a mean global signature of −61.3 ± 0.7‰ and find that tropical wetland emissions are enriched by ~11‰ relative to boreal wetlands. Our model shows improved resolution of regional, latitudinal and global variations in isotopic composition of wetland emissions. Atmospheric simulation scenarios with the improved wetland isotopic composition suggest that increases in atmospheric methane since 2007 are attributable to rising microbial emissions. Our findings substantially reduce uncertainty in the stable carbon isotopic composition of methane emissions from wetlands and improve understanding of the global methane budget. 

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2. Biocrust carbon exchange varies with crust type and time on Chihuahuan Desert gypsum soils

   https://doi.org/10.3389/fmicb.2023.1128631  

   Hoellrich, Mikaela R.; James, Darren K.; Bustos, David; Darrouzet-Nardi, Anthony; Santiago, Louis S.; Pietrasiak, Nicole (May 2023, Frontiers in Microbiology)

   Introduction In dryland systems, biological soil crusts (biocrusts) can occupy large areas of plant interspaces, where they fix carbon following rain. Although distinct biocrust types contain different dominant photoautotrophs, few studies to date have documented carbon exchange over time from various biocrust types. This is especially true for gypsum soils. Our objective was to assess the carbon exchange of biocrust types established at the world’s largest gypsum dune field at White Sands National Park. Methods We sampled five different biocrust types from a sand sheet location in three different years and seasons (summer 2020, fall 2021, and winter 2022) for carbon exchange measurements in controlled lab conditions. Biocrusts were rehydrated to full saturation and light incubated for 30 min, 2, 6, 12, 24, and 36 h. Samples were then subject to a 12-point light regime with a LI-6400XT photosynthesis system to determine carbon exchange. Results Biocrust carbon exchange values differed by biocrust type, by incubation time since wetting, and by date of field sampling. Lichens and mosses had higher gross and net carbon fixation rates than dark and light cyanobacterial crusts. High respiration rates were found after 0.5 h and 2 h incubation times as communities recovered from desiccation, leveling off after 6 h incubation. Net carbon fixation of all types increased with longer incubation time, primarily as a result of decreasing respiration, which suggests rapid recovery of biocrust photosynthesis across types. However, net carbon fixation rates varied from year to year, likely as a product of time since the last rain event and environmental conditions preceding collection, with moss crusts being most sensitive to environmental stress at our study sites. Discussion Given the complexity of patterns discovered in our study, it is especially important to consider a multitude of factors when comparing biocrust carbon exchange rates across studies. Understanding the dynamics of biocrust carbon fixation in distinct crust types will enable greater precision of carbon cycling models and improved forecasting of impacts of global climate change on dryland carbon cycling and ecosystem functioning. 

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3. A Reconsideration of the Failure of Uncovered Interest Parity for the U.S. Dollar

   Engel, Charles Kazakova (May 2022, Journal of international economics)

   We reexamine the time-series evidence on uncovered interest rate parity for the U.S. dollar versus major currencies at short-, medium- and long-horizons. The evidence that interest rate differentials predict foreign exchange returns is not stable over time and disappears altogether when interest rates are near the zero-lower bound. However, we find that year-on-year inflation rate differentials predict excess returns – when the U.S. y.o.y. inflation rate is relatively high, subsequent returns on U.S. deposits tend to be high. We interpret this as consistent with the hypothesis that markets underreact initially to predictable changes in future monetary policy. The predictive power of y.o.y. inflation begins in the mid-1980s when central banks began to target inflation consistently and continues in the post-ZLB period when interest rates lose their primacy as a policy instrument. We attempt to address some econometric problems that might bias the conventional Fama (1984) test. 

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4. Greenland Surface Melt Dominated by Solar and Sensible Heating

   https://doi.org/10.1029/2020GL090653  

   Wang, Wenshan; Zender, Charles S.; van As, Dirk; Fausto, Robert S.; Laffin, Matthew K. (April 2021, Geophysical Research Letters)

   Abstract The Greenland Ice Sheet is the primary source of global Barystatic sea‐level rise, and at least half of its recent mass‐loss acceleration is caused by surface meltwater runoff. Previous studies on surface melt have examined various thermodynamic and dynamic drivers, yet their contributions are not compared using unified observations. We use decade‐long in‐situ measurements from automatic weather stations throughout the ablation zone to assess energy components and identify the leading physical processes in this area. Large melt events exceeding 3σcontribute only ∼2% to total surface melt since 2007. The day‐to‐day variability of all melt is dominated by sensible heat exchange (31 ± 7%) and shortwave radiation (28 ± 5%). Sensible and solar heating correlate with the occurrence of dry and fast gravity‐driven winds. These katabatic winds increase sensible heating of the surface mainly by enhancing vertical mixing that reduces the temperature inversion. The concomitant low humidity and clear skies yield increased solar heating. 

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5. A generic risk assessment framework to evaluate historical and future climate-induced risk for rainfed corn and soybean yield in the U.S. Midwest

   Zhou, W. (August 2021, Weather and climate extremes)

   null (Ed.)

   Fluctuations in temperature and precipitation are expected to increase with global climate change, with more frequent, more intense and longer-lasting extreme events, posing greater challenges for the security of global food production. Here we proposed a generic framework to assess the impact of climate-induced crop yield risk under both current and future scenarios by combining a stochastic model for synthetic climate generation with a well-validated statistical crop yield model. The synthetic climate patterns were generated using the extended Empirical Orthogonal Function method based on historically observed and projected climate conditions. We applied our framework to assess the corn and soybean yield risk in the U.S. Midwest for historical and future climate conditions. We found that: (1) in the U.S. Midwest, about 45% and 40% of the interannual variability in corn and soybean yield, respectively, can be explained by the climate; (2) the risk level is higher in the southwest and northwest regions of the U.S. Midwest corresponding to 25% yield reduction for both corn and soybean compared to other regions; (3) the severity for the 1988 and 2012 major droughts quantified by our method represent 21-year and 30-year events for corn, and 7-year and 12-year events for soybean, respectively; (4) the crop yield risk will increase under a future climate scenario (i.e., Representative Concentration Pathway 8.5 or RCP 8.5 at 2050) compared with the current climate condition, with averaged yield decreases and yield variability increases for both corn and soybean. The framework and the results of this study enable applications for risk management policies and practices for the agriculture sectors. 

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