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Hydrofluorocarbons (HFCs) are powerful anthropogenic greenhouse gases (GHGs) with high global-warming potentials (GWPs). They have been widely used as refrigerants, insulation foam-blowing agents, aerosol propellants, and fire suppression agents. Since the mid-1990s, emissions of HFCs have been increasing rapidly as they are used in many applications to replace ozone-depleting chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) whose consumption and production have been phased out under the Montreal Protocol (MP). Due to the high GWP of HFCs, the Kigali Amendment to the MP requires the phasedown of production and consumption of HFCs to gradually achieve an 80 %–85 % reduction by 2047, starting in 2019 for non-Article 5 (developed) countries with a 10 % reduction against each defined baseline and later schedules for Article 5 (developing) countries. In this study, we have examined long-term high-precision measurements of atmospheric abundances of five major HFCs (HFC-134a, HFC-143a, HFC-32, HFC-125, and HFC-152a) at Gosan station, Jeju Island, South Korea, from 2008 to 2020. Background abundances of HFCs gradually increased, and the inflow of polluted air masses with elevated abundances from surrounding source regions were detected over the entire period. From these pollution events, we inferred regional and country-specific HFC emission estimates using two independent Lagrangian particle dispersion models and Bayesian inversion frameworks (FLEXPART-FLEXINVERT + and NAME-InTEM). The spatial distribution of the derived "top-down" (measurement based) emissions for all HFCs shows large fluxes from megacities and industrial areas in the region. Our most important finding is that HFC emissions in eastern China and Japan have sharply increased from 2016 to 2018. The contribution of East Asian HFC emissions to the global total increased from 9 % (2008–2014) to 13 % (2016–2020). In particular, HFC emissions in Japan (Annex I country) rose rapidly from 2016 onward, with accumulated total inferred HFC emissions being ∼ 114 Gg yr -1 , which is ∼ 76 Gg yr -1 higher for 2016–2020 than the "bottom-up" (i.e., based on activity data and emission factors) emissions of ∼ 38 Gg yr -1 reported to the United Nations Framework Convention on Climate Change (UNFCCC). This is likely related to the increase in domestic demand in Japan for refrigerants and air-conditioning-system-related products and incomplete accounting. A downward trend of HFC emissions that started in 2019 reflects the effectiveness of the F-gas policy in Japan. Eastern China and South Korea, though not obligated to report to the UNFCCC, voluntarily reported emissions, which also show differences between top-down and bottom-up emission estimates, demonstrating the need for atmospheric measurements, comprehensive data analysis, and accurate reporting for precise emission management. Further, the proportional contribution of each country's CO 2 -equivalent HFC emissions has changed over time, with HFC-134a decreasing and HFC-125 increasing. This demonstrates the transition in the predominant HFC substances contributing to global warming in each country. [ABSTRACT FROM AUTHOR]

Coastal warming, acidification, and deoxygenation are progressing primarily due to the increase in anthropogenic CO 2. Coastal acidification has been reported to have effects that are anticipated to become more severe as acidification progresses, including inhibiting the formation of shells of calcifying organisms such as shellfish, which include Pacific oysters (Crassostrea gigas), one of the most important aquaculture resources in Japan. Moreover, there is concern regarding the combined impacts of coastal warming, acidification, and deoxygenation on Pacific oysters. However, spatiotemporal variations in acidification and deoxygenation indicators such as pH, the aragonite saturation state (Ωarag), and dissolved oxygen have not been observed and projected in oceanic Pacific oyster farms in Japan. To assess the present impacts and project future impacts of coastal warming, acidification, and deoxygenation on Pacific oysters, we performed continuous in situ monitoring, numerical modeling, and microscopic examination of Pacific oyster larvae in the Hinase area of Okayama Prefecture and Shizugawa Bay in Miyagi Prefecture, Japan, both of which are famous for their Pacific oyster farms. Our monitoring results first found Ωarag values lower than the critical level of acidification for Pacific oyster larvae in Hinase, although no impact of acidification on larvae was identified by microscopic examination. Our modeling results suggest that Pacific oyster larvae are anticipated to be affected more seriously by the combined impacts of coastal warming and acidification, with lower pH and Ωarag values and a prolonged spawning period, which may shorten the oyster shipping period and lower the quality of oysters. [ABSTRACT FROM AUTHOR]

Carbon dioxide concentrations in the atmosphere play an integral role in many Earth system dynamics, including its influence on global temperature. The past can provide insights into these dynamics, but unfortunately reconstructing long-term trends of atmospheric carbon dioxide (expressed in partial pressure; pCO2) remains a challenge in paleoclimatology. One promising approach for reconstructing past pCO2 utilizes the isotopic fractionation associated with CO2 fixation during photosynthesis into organic matter (εp). Previous studies have focused primarily on testing estimates of εp derived from the δ13C of species-specific alkenone compounds in laboratory cultures and mesocosm experiments. Here, we analyze εp derived from the δ13C of more general algal biomarkers, i.e., compounds derived from a multitude of species from sites near a CO2 seep off the coast of Shikine Island (Japan), a natural environment with CO2 concentrations ranging from ambient (ca. 310 µ atm) to elevated (ca. 770 µ atm) pCO2. We observed strong, consistent δ13C shifts in several algal biomarkers from a variety of sample matrices over the steep CO2 gradient. Of the three general algal biomarkers explored here, namely loliolide, phytol, and cholesterol, εp positively correlates with pCO2 , in agreement with εp theory and previous culture studies. pCO2 reconstructed from the εp of general algal biomarkers show the same trends throughout, as well as the correct control values, but with lower absolute reconstructed values than the measured values at the elevated pCO2 sites. Our results show that naturally occurring CO2 seeps may provide useful testing grounds for pCO2 proxies and that general algal biomarkers show promise for reconstructing past pCO2. [ABSTRACT FROM AUTHOR]

Lidar observations of vertical profiles of aerosols and thin cirrus clouds were made at Tsukuba (36.05° N, 140.12° E), Japan, to investigate the influence of aerosols and thin cirrus clouds on the column-averaged dry-air mole fraction of carbon dioxide (XCO2) retrieved from observation data of the Thermal And Near-infrared Sensor for carbon Observation Fourier Transform Spectrometer, measured in the Short-Wavelength InfraRed band (TANSO-FTS SWIR), onboard the Greenhouse gases Observing SATellite (GOSAT). The lidar system measured the backscattering ratio, depolarization ratio, and/or the wavelength exponent of atmospheric particles. The lidar observations and ground-based highresolution FTS measurements at the Tsukuba Total Carbon Column Observing Network (Tsukuba TCCON) site were recorded simultaneously during passages of GOSAT over Tsukuba. GOSAT SWIR XCO2 data (Version 01.xx) released in August 2010 were compared with the lidar and Tsukuba TCCON data. High-altitude aerosols and thin cirrus clouds had a large impact on the GOSAT SWIR XCO2 results. By taking into account the observed aerosol/cirrus vertical profiles and using a more adequate solar irradiance database in the GOSAT SWIR retrieval, the difference between the GOSAT SWIR XCO2 data and the Tsukuba TCCON data was reduced. The 3-band retrieval approach where the aerosol and cirrus profiles were retrieved gave us the best results and the retrieved XCO2 data followed the seasonal cycle of ~8 ppm observed at Tsukuba TCCON site. [ABSTRACT FROM AUTHOR]

Column-averaged volume mixing ratios of carbon dioxide (XCO2 ) during the period from January 2007 to May 2008 over Tsukuba, Japan, were derived using CO2 concentrations measured by Continuous CO2 Measuring Equipment (CME). The CMEs were installed on Japan Airlines Corporation (JAL) commercial airliners, which frequently fly to and from Narita Airport. It was assumed that CO2 profiles over Tsukuba and Narita are the same. CO2 profile data for 493 flights on clear-sky days were analyzed in order to calculate XCO2 with one of two ancillary datasets: "Tsukuba observational" data (rawinsonde and meteorological tower), or "global" forecast/reanalysis and climatological data (NCEP and CIRA-86). The amplitude of the seasonal variation of XCO2 using the ancillary data measured in Tsukuba (XCO2(Tsukuba observational)) was determined by a least squares fit using a harmonic function to roughly evaluate the seasonal variation over Tsukuba. The highest and lowest values of the obtained fitted curve in 2007 for XCO2 (Tsukuba observational) were 386.4±1.0 and 381.7±1.0 ppm in May and September, respectively, where the errors represent 1 standard deviation of the fit residuals. The dependence of XCO2 on the type of ancillary dataset was evaluated. The average difference between XCO2 from global climatological data, XCO2 (global), and XCO2 (Tsukuba observational), i.e., the bias of XCO2 (global) based on XCO2 (Tsukuba observational), was found to be -0.621 ppm with a standard deviation of 0.682 ppm. The uncertainty of XCO2 (global) based on XCO2 (Tsukuba observational) was estimated to be 0.922 ppm. This small uncertainty relative to the GOSAT precision suggests that calculating XCO2 using data from airliners and global climatological data can be applied to the validation of GOSAT products for XCO2 over airports worldwide. [ABSTRACT FROM AUTHOR]