The switch from the use of coal to natural gas or oil for energy generation potentially reduces greenhouse gas emissions and thus the impact on global warming and climate change because of the higher ...energy creation per CO.sub.2 molecule emitted. However, the climate benefit over coal is offset by methane (CH.sub.4) leakage from natural gas and petroleum systems, which reverses the climate impact mitigation if the rate of fugitive emissions exceeds the compensation point at which the global warming resulting from the leakage and the benefit from the reduction of coal combustion coincide. Consequently, an accurate quantification of CH.sub.4 emissions from the oil and gas industry is essential to evaluate the suitability of natural gas and petroleum as bridging fuels on the way to a carbon-neutral future.
Satellite observations of the high-resolution TROPOspheric Monitoring Instrument (TROPOMI) on Sentinel-5 Precursor can be used to observe nitrogen dioxide (NO2) at city scales to quantify short time ...variability of nitrogen oxide (NOx) emissions and lifetimes on a daily and seasonal basis. In this study, 2 years of TROPOMI tropospheric NO2 columns, having a spatial resolution of up to 3.5 km × 5.5 km, have been analyzed together with wind and ozone data. NOx lifetimes and emission fluxes are estimated for 50 different NOx sources comprising cities, isolated power plants, industrial regions, oil fields, and regions with a mix of sources distributed around the world. The retrieved NOx emissions are in agreement with other TROPOMI-based estimates and reproduce the variability seen in power plant stack measurements but are in general lower than the analyzed stack measurements and emission inventory results. Separation into seasons shows a clear seasonal dependence of NOx emissions with in general the highest emissions during winter, except for isolated power plants and especially sources in hot desert climates, where the opposite is found. The NOx lifetime shows a systematic latitudinal dependence with an increase in lifetime from 2 to 8 h with latitude but only a weak seasonal dependence. For most of the 50 sources including the city of Wuhan in China, a clear weekly pattern of NOx emissions is found, with weekend-to-weekday ratios of up to 0.5 but with a high variability for the different locations. During the Covid-19 lockdown period in 2020, strong reductions in the NOx emissions were observed for New Delhi, Buenos Aires, and Madrid.
We construct global budgets of atmospheric glyoxal and methylglyoxal with the goal of quantifying their potential for global secondary organic aerosol (SOA) formation via irreversible uptake by ...aqueous aerosols and clouds. We conduct a detailed simulation of glyoxal and methylglyoxal in the GEOS‐Chem global 3‐D chemical transport model including our best knowledge of source and sink processes. Our resulting best estimates of the global sources of glyoxal and methylglyoxal are 45 Tg a−1 and 140 Tg a−1, respectively. Oxidation of biogenic isoprene contributes globally 47% of glyoxal and 79% of methylglyoxal. The second most important precursors are acetylene (mostly anthropogenic) for glyoxal and acetone (mostly biogenic) for methylglyoxal. Both acetylene and acetone have long lifetimes and provide a source of dicarbonyls in the free troposphere. Atmospheric lifetimes of glyoxal and methylglyoxal in the model are 2.9 h and 1.6 h, respectively, mostly determined by photolysis. Simulated dicarbonyl concentrations in continental surface air at northern midlatitudes are in the range 10–100 ppt, consistent with in situ measurements. On a global scale, the highest concentrations are over biomass burning regions, in agreement with glyoxal column observations from the SCIAMACHY satellite instrument. SCIAMACHY and a few ship cruises also suggest a large marine source of dicarbonyls missing from our model. The global source of SOA from the irreversible uptake of dicarbonyls in GEOS‐Chem is 11 Tg C a−1, including 2.6 Tg C a−1 from glyoxal and 8 Tg C a−1 from methylglyoxal; 90% of this source takes place in clouds. The magnitude of the global SOA source from dicarbonyls is comparable to that computed in GEOS‐Chem from the standard mechanism involving reversible partitioning of semivolatile products from the oxidation of monoterpenes, sesquiterpenes, isoprene, and aromatics.
Global child mortality reduced substantially during the Millennium Development Goal period (2000–15). We aimed to estimate morbidity, mortality, and prevalence of risk factors for child pneumonia at ...the global, regional, and national level for developing countries for the Millennium Development Goal period.
We estimated the incidence, number of hospital admissions, and in-hospital mortality due to all-cause clinical pneumonia in children younger than 5 years in developing countries at 5-year intervals during the Millennium Development Goal period (2000–15) using data from a systematic review and Poisson regression. We estimated the incidence and number of cases of clinical pneumonia, and the pneumonia burden attributable to HIV for 132 developing countries using a risk-factor-based model that used Demographic and Health Survey data on prevalence of the various risk factors for child pneumonia. We also estimated pneumonia mortality in young children using data from multicause models based on vital registration and verbal autopsy.
Globally, the number of episodes of clinical pneumonia in young children decreased by 22% from 178 million (95% uncertainty interval UI 110–289) in 2000 to 138 million (86–226) in 2015. In 2015, India, Nigeria, Indonesia, Pakistan, and China contributed to more than 54% of all global pneumonia cases, with 32% of the global burden from India alone. Between 2000 and 2015, the burden of clinical pneumonia attributable to HIV decreased by 45%. Between 2000 and 2015, global hospital admissions for child pneumonia increased by 2·9 times with a more rapid increase observed in the WHO South-East Asia Region than the African Region. Pneumonia deaths in this age group decreased from 1·7 million (95% UI 1·7–2·0) in 2000 to 0·9 million (0·8–1·1) in 2015. In 2015, 49% of global pneumonia deaths occurred in India, Nigeria, Pakistan, Democratic Republic of the Congo, and Ethiopia collectively. All key risk factors for child pneumonia (non-exclusive breastfeeding, crowding, malnutrition, indoor air pollution, incomplete immunisation, and paediatric HIV), with the exception of low birthweight, decreased across all regions between 2000 and 2015.
Globally, the incidence of child pneumonia decreased by 30% and mortality decreased by 51% during the Millennium Development Goal period. These reductions are consistent with the decrease in the prevalence of some of the key risk factors for pneumonia, increasing socioeconomic development and preventive interventions, improved access to care, and quality of care in hospitals. However, intersectoral action is required to improve socioeconomic conditions and increase coverage of interventions targeting risk factors for child pneumonia to accelerate decline in pneumonia mortality and achieve the Sustainable Development Goals for health by 2030.
Bill & Melinda Gates Foundation.
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We use height‐resolved and total column satellite observations and 3‐D chemical transport model simulations to study stratospheric ozone variations during 1998–2017 as ozone‐depleting substances ...decline. In 2017 extrapolar lower stratospheric ozone displayed a strong positive anomaly following much lower values in 2016. This points to large interannual variability rather than an ongoing downward trend, as reported recently by Ball et al. (2018, https://doi.org/10.5194/acp‐18‐1379‐2018). The observed ozone variations are well captured by the chemical transport model throughout the stratosphere and are largely driven by meteorology. Model sensitivity experiments show that the contribution of past trends in short‐lived chlorine species to the ozone changes is small. Similarly, the potential impact of modest trends in natural brominated short‐lived species is small. These results confirm the important role that atmospheric dynamics plays in controlling ozone in the extrapolar lower stratosphere on multiannual time scales and the continued importance of monitoring ozone profiles as the stratosphere changes.
Plain Language Summary
Emission of long‐lived chlorine and bromine‐containing ozone‐depleting substances has led to the depletion of the ozone layer, most notably the Antarctic ozone hole. Policy action through the Montreal Protocol has phased out the production of the major long‐lived ozone‐depleting substances. Consequently, stratospheric chlorine and bromine amounts are declining, and we expect the ozone layer to slowly recover. However, although the tropical lower stratosphere is not a region where large ozone loss has so‐far been observed, a recent study by Ball et al. (2018) suggested that ozone there is decreasing, in disagreement with models and expectations of ozone recovery. We use updated observations and an atmospheric model to investigate these issues. First, we use an additional year of observations which show that ozone values in the lower stratosphere increased in 2017, which is a consequence of variations in atmospheric dynamics. Second, our 3‐D model performs well in reproducing the observed ozone variations. Although the model is not perfect, the comparisons suggest that we do have a good understanding of the lower stratospheric ozone. Third, we quantify the role of short‐lived chlorine and bromine compounds, which are not controlled by the Montreal Protocol, on the recent ozone changes. The effect is small.
Key Points
Observations show that lower stratospheric ozone at extrapolar latitudes increased strongly in 2017 relative to a negative anomaly in 2016
Model simulations reproduce the observed ozone variations well, and the main driver in the lower stratosphere is atmospheric dynamics
The contribution of an observation‐based trend in short‐lived chlorine species to recent lower stratospheric ozone variations is small
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Despite its key role in climate change, large uncertainties persist in our knowledge of the anthropogenic emissions of carbon dioxide (CO2) and no global observing system exists that allows us to ...monitor emissions from localized CO2 sources with sufficient accuracy. The Orbiting Carbon Observatory-2 (OCO-2) satellite allows retrievals of the column-average dry-air mole fractions of CO2 (XCO2). However, regional column-average enhancements of individual point sources are usually small, compared to the background concentration and its natural variability, and often not much larger than the satellite's measurement noise. This makes the unambiguous identification and quantification of anthropogenic emission plume signals challenging. NO2 is co-emitted with CO2 when fossil fuels are combusted at high temperatures. It has a short lifetime on the order of hours so that NO2 columns often greatly exceed background and noise levels of modern satellite sensors near sources, which makes it a suitable tracer of recently emitted CO2. Based on six case studies (Moscow, Russia; Lipetsk, Russia; Baghdad, Iraq; Medupi and Matimba power plants, South Africa; Australian wildfires; and Nanjing, China), we demonstrate the usefulness of simultaneous satellite observations of NO2 and XCO2. For this purpose, we analyze co-located regional enhancements of XCO2 observed by OCO-2 and NO2 from the Sentinel-5 Precursor (S5P) satellite and estimate the CO2 plume's cross-sectional fluxes. We take advantage of the nearly simultaneous NO2 measurements with S5P's wide swath and small measurement noise by identifying the source of the observed XCO2 enhancements, excluding interference with remote upwind sources, allowing us to adjust the wind direction, and by constraining the shape of the CO2 plumes. We compare the inferred cross-sectional fluxes with the Emissions Database for Global Atmospheric Research (EDGAR), the Open-Data Inventory for Anthropogenic Carbon dioxide (ODIAC), and, in the case of the Australian wildfires, with the Global Fire Emissions Database (GFED). The inferred cross-sectional fluxes range from 31 MtCO2 a−1 to 153 MtCO2 a−1 with uncertainties (1σ) between 23 % and 72 %. For the majority of analyzed emission sources, the estimated cross-sectional fluxes agree, within their uncertainty, with either EDGAR or ODIAC or lie somewhere between them. We assess the contribution of multiple sources of uncertainty and find that the dominating contributions are related to the computation of the effective wind speed normal to the plume's cross section. The flux uncertainties are expected to be reduced by the planned European Copernicus anthropogenic CO2 monitoring mission (CO2M), which will provide not only precise measurements with high spatial resolution but also imaging capabilities with a wider swath of simultaneous XCO2 and NO2 observations. Such a mission, particularly if performed by a constellation of satellites, will deliver CO2 emission estimates from localized sources at an unprecedented frequency and level of accuracy.
Due to proceeding climate change, some regions such as California face rising weather extremes with
dry periods becoming warmer and drier, entailing the risk that wildfires and associated air
...pollution episodes will continue to increase. November 2018 turned into one of the most severe
wildfire episodes on record in California, with two particularly destructive wildfires spreading
concurrently through the north and the south of the state. Both fires ignited at the wildland–urban
interface, causing many civilian fatalities and forcing the total evacuation of several cities and
communities. Here we demonstrate that the inherent carbon monoxide (CO) emissions of the wildfires and
subsequent transport can be observed from space by analysing radiance measurements of the
TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor
satellite in the shortwave infrared spectral range. From the determined CO distribution we
assess the corresponding air quality burden in major Californian cities caused by the fires and
discuss the associated uncertainties. As a result of the prevailing wind conditions, the largest
CO load during the first days of the fires is found in Sacramento and San Francisco, with
city area averages reaching boundary layer concentration anomalies of about
2.5 mg CO m−3. Even the most polluted city scenes likely comply with the
national ambient air quality standards (10 mg CO m−3 with 8 h averaging
time). This finding based on dense daily recurrent satellite monitoring is consistent with isolated
ground-based air quality measurements.
Glyoxal (CHOCHO) and formaldehyde (HCHO) are
intermediate products in the tropospheric oxidation of the majority of
volatile organic compounds (VOCs). CHOCHO is also a precursor of secondary
organic ...aerosol (SOA) in the atmosphere. CHOCHO and HCHO are released from
biogenic, anthropogenic, and pyrogenic sources. CHOCHO and HCHO
tropospheric lifetimes are typically considered to be short during the
daytime at mid-latitudes (e.g. several hours), as they are rapidly removed
from the atmosphere by their photolysis, oxidation by OH, and uptake on
particles or deposition. At night and at high latitudes, tropospheric
lifetimes increase to many hours or even days. Previous studies demonstrated
that CHOCHO and HCHO vertical column densities (VCDs) are well retrieved
from space-borne observations using differential optical absorption
spectroscopy (DOAS). In this study, we present CHOCHO and HCHO VCDs
retrieved from measurements by TROPOMI (TROPOspheric Monitoring Instrument), launched on the
Sentinel-5 Precursor (S5P) platform in October 2017. We observe strongly
elevated amounts of CHOCHO and HCHO during the 2018 fire season in British
Columbia, Canada, where a large number of fires occurred in August. CHOCHO
and HCHO plumes from individual fire hot spots are observed in air masses
travelling over distances of up to 1500 km, i.e. much longer than expected
for the relatively short tropospheric lifetime expected for CHOCHO and
HCHO. Comparison with simulations by the particle dispersion model FLEXPART
(FLEXible PARTicle dispersion model)
indicates that effective lifetimes of 20 h and more are needed to
explain the observations of CHOCHO and HCHO if they decay in an effective
first-order process. FLEXPART used in the study calculates accurately the
transport. In addition an exponential decay, in our case assumed to be
photochemical, of a species along the trajectory is added. We have used this
simple approach to test our assumption that CHOCHO and HCHO are created
in the fires and then decay at a constant rate in the plume as it is
transported. This is clearly not the case and we infer that CHOCHO and HCHO
are either efficiently recycled during transport or continuously formed
from the oxidation of longer-lived precursors present in the plume, or
possibly a mixture of both. We consider the best explanation of the observed
CHOCHO and HCHO VCD in the plumes of the fire is that they are produced by
oxidation of longer-lived precursors, which were also released by the fire and present
in the plume.
The origin of fire‐adapted lineages is a long‐standing question in ecology. Although phylogeny can provide a significant contribution to the ongoing debate, its use has been precluded by the lack of ...comprehensive DNA data. Here, we focus on the ‘underground trees’ (=geoxyles) of southern Africa, one of the most distinctive growth forms characteristic of fire‐prone savannas. We placed geoxyles within the most comprehensive dated phylogeny for the regional flora comprising over 1400 woody species. Using this phylogeny, we tested whether African geoxyles evolved concomitantly with those of the South American cerrado and used their phylogenetic position to date the appearance of humid savannas. We found multiple independent origins of the geoxyle life‐form mostly from the Pliocene, a period consistent with the origin of cerrado, with the majority of divergences occurring within the last 2 million yr. When contrasted with their tree relatives, geoxyles occur in regions characterized by higher rainfall and greater fire frequency. Our results indicate that the geoxylic growth form may have evolved in response to the interactive effects of frequent fires and high precipitation. As such, geoxyles may be regarded as markers of fire‐maintained savannas occurring in climates suitable for forests.
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•A fast radiative transfer model, FASMAR, for aerosol remote sensing was developed.•The accuracy of FASMAR is better than 3% for GEO and LEO satellite observations.•FASMAR is valid for all surface ...and atmospheric conditions.•FASMAR is used to create ‘NRT FIRSTLOOK’ global aerosol products.
After several decades’ development of retrieval techniques in aerosol remote sensing, no fast and accurate analytical Radiative Transfer Model (RTM) has been developed and applied to create global aerosol products for non-polarimetric instruments such as Ocean and Land Colour Instrument/Sentinel-3 (OLCI/Sentinel-3) and Meteosat Second Generation/Spinning Enhanced Visible and Infrared Imager (MSG/SEVIRI). Global aerosol retrieval algorithms are typically based on a Look-Up–Table (LUT) technique, requiring high-performance computers. The current eXtensible Bremen Aerosol/cloud and surfacE parameters Retrieval (XBAER) algorithm also utilizes the LUT method. In order to have a near-real time retrieval and achieve a quick and accurate “FIRST-LOOK” aerosol product without high-demand of computing resource, we have developed a Fast and Accurate Semi-analytical Model of Atmosphere-surface Reflectance (FASMAR) for aerosol remote sensing. The FASMAR is developed based on a successive order of scattering technique. In FASMAR, the first three orders of scattering are calculated exactly. The contribution of higher orders of scattering is estimated using an extrapolation technique and an additional correction function. The evaluation of FASMAR has been performed by comparing with radiative transfer model SCIATRAN for all typical observation/illumination geometries, surface/aerosol conditions, and wavelengths 412, 550, 670, 870, 1600, 2100 nm used for aerosol remote sensing. The selected observation/illumination conditions are based on the observations from both geostationary satellite (e.g. MSG/SEVIRI) and polar-orbit satellite (e.g. OLCI/Sentinel-3). The percentage error of the top of atmosphere reflectance calculated by FASMAR is within ± 3% for typical polar-orbit/geostationary satellites’ observation/illumination geometries. The accuracy decreases for solar and viewing zenith angles larger than 70∘. However, even in such cases, the error is within the range ± 5%. The evaluation of model performance also shows that FASMAR can be used for all typical surfaces with albedo in the interval 0−1and aerosol with optical thickness in the range 0.01−1.
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