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Adoption of cleaner technologies and reduction in fire events in the hotspots lead to global decline in carbon monoxide
Abstract
Carbon Monoxide (CO) is not a greenhouse gas (GHG), but has the capacity to change atmospheric chemistry of other GHGs such as methane and ozone, and therefore indirectly affects Earth's radiative forcing of the GHGs and surface temperature. Here, we use the CO mixing ratio at 850 hPa from the Tropospheric Emission Spectrometer (TES) reanalysis and the Measurement of Pollution in the Troposphere (MOPITT) satellite measurements for the period 2005-2019 to examine the spatio-temporal changes in CO across the latitudes. We find a substantial decrease in global CO, about 0.21 ± 0.09 ppb/yr (0.23 ± 0.12%/yr) with the TES data and about 0.36 ± 0.07 ppb/yr (0.45 ± 0.08%/yr) with the MOPITT satellite measurements during the study period. The highest CO decreasing trend is observed in Eastern China (2.7 ± 0.37 ppb/yr) followed by Myanmar (2.142 ± 0.59 ppb/yr) and South America (1.08 ± 0.82 ppb/yr). This negative trend in CO is primarily due to the decrease in biomass burning and stringent environmental regulations in the respective regions and countries. The sources including road transport that account for about 33.6% of CO emissions, followed by industries (18.3%) and agricultural waste burning (8.8%), might also be responsible for the reduction in CO due to adaptation of improved emission control technology and regulations in the past decade from 2005 to 2019. Therefore, the study provides new insights on the current trends of global CO distribution and reasons for recent reduction in global CO emissions, which would be useful for future decision-making process to control air pollution.
... These studies report the highest CO mixing ratio in the northern hemisphere (NH) winter ranging from 200 to 220 ppb and the lowest mixing ratios in the southern hemisphere (SH) summer with values of about 35-45 ppb. Joshi et al. (2023) also observed a significant seasonal variability of CO in the troposphere, e.g. with its peak in February-March and the minimum in July-August in Indo-Gangetic Plain (IGP). They find a significant decline in the global CO due to the implementation of environmental laws, technological advance to cut the emissions and reduction in the fire events and biomass burning in the CO hotspot regions. ...
... Most studies on atmospheric CO are restricted to the troposphere and extra-tropical atmosphere (Brunke et al., 1990;Seiler et al., 1984;Sheel et al., 2014Sheel et al., , 2016Kuttippurath et al., 2023;Joshi et al., 2023). Also, most research on the long-term CO trends are limited to the troposphere or up to the Upper Troposphere Lower Stratosphere (UTLS). ...
... Although the trend in tropospheric CO column and vertical profiles have been vastly studied (Brunke et al., 1990;Rinsland et al., 2000;Isaksen and Hov, 1987;Dlugokencky et al., 1996;Strode and Pawson, 2013;Wai et al., 2014;Joshi et al., 2023), the spatio-temporal analysis of the middle atmospheric CO remained untouched due to the lack of data for this region. However, there are few studies that examine the global CO budget as well as the global CO column trends (Khalil and Rasmussen, 1988;Duncan and Logan, 2008;Worden et al., 2013;Gratz et al., 2015). ...
Middle atmospheric carbon monoxide (CO) has been considered as a dynamical tracer to study the transport in the stratosphere and mesosphere because of its long lifetime. However, most trend studies of CO are limited to troposphere and the Upper Troposphere Lower Stratosphere (UTLS). Here, we investigate the seasonal, annual and long-term changes of CO in the tropical (30° N–30° S) middle atmosphere (20–80 km) for the period of 2005–2021. CO shows a semi-annual oscillation in the higher altitudes of both stratosphere and mesosphere. The response of solar cycle to CO increases with altitude and is largest in the mesosphere. On the other hand, Quasi Biennial Oscillation (QBO) response to CO change is highest in the lower stratosphere. The CO trends are statistically insignificant at all altitudes, although they are positive in the height range 20–25 km and 32–40 km, at about 0.01–0.035/yr, depending on altitude. The observed changes in the middle atmospheric CO in the tropics are well reproduced by the Whole Atmospheric Chemical Climate Model (WACCM). Therefore, this study provides new insights on the long-term changes in the tropical middle atmospheric CO and its connection to dynamics of the region.
... As per the IHME evalutions, it was linked to 365,000 premature deaths worldwide due to chronic obstructive pulmonary disease (COPD) in 2016 alone and has been increasing from 2014 onwards (Izadi, 2018). The formation of ozone near the surface is driven by a number of complex reactions of precursors with transport on all scales (Travis et al., 2016;Joshi et al., 2023;Kuttippurath et al., 2022). As each city has its unique pollution sources and challenges, tailored interventions are devised globally to address local air pollution issues effectively (Han et al., 2022;Chen et al., 2021;Liu et al., 2022). ...
There is a significant increase in ozone at the surface and troposphere due to growing population, industrialization and urbanization. The initiation of National Clean Air Programme (NCAP) in 2019 marked a turning point in addressing air pollution in Indian cities. The Central Pollution Control Board (CPCB) ground-based measurements show a reduction in number of days with continuous exposure to 8 h surface ozone (MDA-8) exceeding 100 ppb since the implementation of NCAP. For instance, cities such as Visakhapatnam and Tirupati reported zero days of MDA-8 ozone surpassing 100 ppb in 2022. Also, a substantial reduction is observed in the frequency of MDA-8 ozone exceeding the 100 ppb threshold at other stations. The NO2 and PM2.5 measurements from CPCB show a decreasing trend at most stations, whereas satellite-based HCHO and NO2 measurements show negative (0–0.004 mol m−2 month−1) and positive (0–0.02 m−2 month−1) trends, respectively, during the period of 2019–2022. Therefore, although the implementation of NCAP is oriented towards reducing PM10 concentrations, it is also proven to be effective in curbing ozone pollution in most cities of India. This study, therefore, suggests to continue the efforts of NCAP and to implement tailored regulations for reducing ozone pollution in cities with high pollution.
... Here, we have taken the total anthropogenic emissions of BC and OC along with those from road transport separately for the period of 1980-2018. This inventory is widely used to understand the emission of pollutants from different anthropogenic sectors across the globe (Joshi et al., 2023). EDGAR offers comprehensive data on greenhouse gas (GHG) and air pollutant emissions for various anthropogenic activities and are classified in accordance with the Intergovernmental Panel on Climate Change (IPCC) guidelines. ...
We analyse the long-term (1980-2020) changes in aerosols over the Third Pole (TP) and assess the changes in radiative forcing (RF) using satellite, ground-based and reanalysis data. The annual mean aerosol optical depth (AOD) varies from 0.06 to 0.24, with the highest values of around 0.2 in the north and southwest TP, which are dominated by dust from Taklimakan and Thar deserts, respectively. However, Organic Carbon (OC), Black Carbon (BC) and sulphate aerosols have significant contribution to the total AOD in the south and east TP. High amounts of dust are observed in spring and summer, but BC in winter. Trajectory analysis reveals that the air mass originated from East and South Asia carries BC and OC, whereas the air from South Asia, Central Asia and Middle East brings dust to TP. Significant positive trends in AOD is found in TP, with high values of about 0.002/yr in the eastern and southern TP. There is a gradual increase in BC and OC concentrations during 1980-2020, but the change from 2000 is phenomenal. The RF at the top of the atmosphere varies from -10 to 2 W/m2 in TP, and high positive RF of about 2 W/m2 is estimated in Pamir, Karakoram and Nyainquentanglha mountains, where the massive glacier mass exists. The RF has increased in much of TP during recent decades (2001-2020) with respect to previous decades (1981-2000), which can be due to the rise in BC and dust during the latter period. Therefore, the positive trend in BC and its associated change in RF can amplify the regional warming, and thus, the melting of glaciers or ice in TP. This is a great concern as it is directly connected to the water security of many South Asian countries.
... During the study period, India's economic and industrial activities have increased considerably, including fuel and coal consumption, which resulted in high emissions of pollutants, particularly NO x and CO, and hence, the formation of ozone through secondary reactions (e.g. Joshi et al., 2023;Levine et al., 1996). Fig. 5 shows the annual (left panel) and seasonal (four small panels on the right side) trends of TPO in India. ...
At higher concentrations, tropospheric ozone can cause respiratory difficulties, premature human mortality and can harm vegetation by reducing photosynthesis and its growth. It is an oxidant and also an important green- house gas with positive feedback to temperature. It is produced as a byproduct of chemical reactions involving nitrogen oxides (NO ) and volatile organic compounds (VOCs) in the presence of sunlight, rather than being emitted directly to the atmosphere. Here, we analyse the seasonal and inter-annual variability, long-term trends and radiative forcing of the tropospheric column ozone (TPO) in India for the period of 2005–2020 using satellite and ground-based data. The analysis shows very high annual averaged TPO in the Indo-Gangetic Plain (IGP) and North West India, about 45–50 DU. Our findings reveal a significant increase of TPO in India, with the highest trend in the peninsular region (0.295 ± 0.0617 DU/year) and the lowest in North West (0.179 ± 0.048 DU/ year). The increase in tropospheric ozone reveals a warming of about 0.5 °C in the troposphere as there is an as- sociated radiative forcing of about 0.2–0.5 W/m 2 at the tropopause (125 hPa); indicating that the increasing tropospheric ozone is a great concern for regional warming, public health and ecosystem dynamics.
The Third Pole (TP) is a high mountain region in the world, and is well-known for its pristine environment, but recent development activities in the region have degraded its air quality. Here, we investigate the spatial and temporal changes of the air pollutants ammonia (NH₃), sulphur dioxide (SO₂) and carbon monoxide (CO) in TP, and reveal their sources using satellite measurements and emission inventory. We observe a clear seasonal cycle of NH3 in TP, with high values in summer and low values in winter. The intense agriculture activities in the southern TP are the cause of high NH₃ (6–8 × 1016 molec./cm2) there. Similarly, CO shows a distinct seasonal cycle with high values in spring in the southeast TP due to biomass burning. In addition, the eastern boundary of TP in the Sichuan and Qinghai provinces also show high values of CO (about 1.5 × 1018 mol/cm2), primarily owing to the industrial activities. There is no seasonal cycle found for SO₂ distribution in TP, but relatively high values (8–10 mg/m2)) are observed in its eastern boundary. The high-altitude pristine regions of inner TP are also getting polluted because of recent human activities in and around TP, as we estimate positive trends in CO (0.5–1.5 × 1016 mol/cm2/yr) there. In addition, positive trends are also found in NH₃ (0.025 × 1016 molec./cm2/yr) during 2008–2020 in most regions of TP and SO₂ (about 0.25–0.75 mg/m2/yr) in the Sichuan and Qinghai region during 2000–2020. As revealed by the emission inventory, there are high anthropogenic emissions of NH3, SO2 and CO within TP. There are emissions of pollutants from energy sectors, oil and refinery, agriculture waste burning and manure management within TP. These anthropogenic activities accelerate the ongoing development in TP, but severely erode its environment.
The COVID-19 lockdown (LD) provided a unique opportunity to examine the changes in regional and global air quality. Changes in the atmospheric carbon monoxide (CO) concentrations during LD warrant a thorough analysis as CO is a major air pollutant that affects human health, ecosystem and climate. Our analysis reveals a decrease of 5-10% in the CO concentrations during LD (April-May 2020) compared to the pre-lockdown (PreLD, March 2020) periods in regions with high anthropogenic activity, such as East China (EC), Indo-Gangetic Plain (IGP), North America, parts of Europe and Russia. However, this reduction did not occur in the regions of frequent and intense wildfires and agricultural waste burning (AWB). We find high heterogeneity in the CO column distributions, from regional to city scales during the LD period. To determine the sources of CO emissions during LD, we examined the ratios of nitrogen dioxide (NO2), sulfur dioxide (SO2) to CO for about 3000 major cities in the world. This facilitated the identification of contributions from different sources; including vehicles, industries, AWB and forest fires during LD. The comparison between CO levels during the LD and PreLD periods indicates a notable reduction in the global tropospheric CO, but no significant change in the stratosphere. It is found that CO emissions decreased during LD in the hotspot regions, but rebounded after the LD restrictions were lifted. This study, therefore, highlights the importance of policy decisions and their implementations in the global and regional scales to improve the air quality, and thus to protect public health and environment.
Fires in South America have profound effects on climate change and air quality. Although anthropogenic forcing has exacerbated drought and fire risks, the fire emissions and aerosol pollution in the southern Amazon and the Pantanal region showed a consistent long-term decrease during the dry season (August–October) between 2003 and 2019. Here, we find that the decreasing trend in fire emissions, mainly located in the non-deforested region, was associated with climatic conditions unfavorable for intensifying and spreading fires, including increased humidity and slower surface wind speed. These climatic trends can be attributed to weakening of the positive phase of the Atlantic Multidecadal Oscillation, which has strengthened the northeast trade winds within the region (3° S–13° N) and the northwest winds east of the Andes that transport more moisture into the southern Amazon and the Pantanal region. Our findings show the mitigating effects of weakening of the positive Atlantic Multidecadal Oscillation phase on human-induced intensification of fire risks in the South America and warn of potentially increased risks of fires and aerosol pollution under intensified anthropogenic forcing in the future.
The study aimed at using Moderate Resolution Imaging Spectroradiometer (MODIS-Terra) to investigate long-term spatial and temporal aerosol variations over Zambia during 2000–2020. Based on data availability, ground truthing for MODIS-Terra was done over Mongu in western Zambia using Aerosol Robotic Network (AERONET) data for 2001–2009. The correlation coefficient between MODIS-Terra and AERONET is 0.42 and statistically significant at 95% confidence level. The aerosol optical depth at 550nm (AOD550) and Angstrom exponent (AE470-870) annual mean spatial distribution indicates high and moderate to low patterns explaining distinct features of aerosol loadings from different areas over Zambia. Generally, the AOD550 and AE470-870 spatial gradient values increase from southern to northern Zambia explaining fine mode particles mainly produced by local intensive anthropogenic and urban/small and large-scale industrial emission activities in the cities. Seasonal climatology reveals that highest AOD550 is observed during SON, followed by JJA, DJF, with the lowest recorded during MAM. It is also observed from AE470-870 that fine particles are prominent during JJA and SON. The insignificant decreasing (increasing) trend of AOD550 is revealed over Mwinilunga, Misamfu, Mfuwe, Choma, and Kabwe (Mongu). Further results showed that fire hotspot density intensifies over central parts of Africa, including Zambia from June to November. Moreover, the 5-day air mass back trajectory analysis suggests that aerosol sources over Zambia are associated with short- and long-distance ranges from East Africa, Congo Basin, Madagascar, and Atlantic and Indian oceans with diverse transport pathways in different seasons. These findings may help enhance a better understanding of climatic effects and atmospheric aerosol sources in Zambia.
Following past studies to quantify decadal trends in global carbon monoxide (CO) using satellite observations, we update estimates and find a CO trend in column amounts of about −0.50 % per year between 2002 to 2018, which is a deceleration compared to analyses performed on shorter records that found −1 % per year. Aerosols are co-emitted with CO from both fires and anthropogenic sources but with a shorter lifetime than CO. A combined trend analysis of CO and aerosol optical depth (AOD) measurements from space helps to diagnose the drivers of regional differences in the CO trend. We use the long-term records of CO from the Measurements of Pollution in the Troposphere (MOPITT) and AOD from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. Other satellite instruments measuring CO in the thermal infrared, AIRS, TES, IASI, and CrIS, show consistent hemispheric CO variability and corroborate results from the trend analysis performed with MOPITT CO. Trends are examined by hemisphere and in regions for 2002 to 2018, with uncertainties quantified. The CO and AOD records are split into two sub-periods (2002 to 2010 and 2010 to 2018) in order to assess trend changes over the 16 years. We focus on four major population centers: Northeast China, North India, Europe, and Eastern USA, as well as fire-prone regions in both hemispheres. In general, CO declines faster in the first half of the record compared to the second half, while AOD trends show more variability across regions. We find evidence of the atmospheric impact of air quality management policies. The large decline in CO found over Northeast China is initially associated with an improvement in combustion efficiency, with subsequent additional air quality improvements from 2010 onwards. Industrial regions with minimal emission control measures such as North India become more globally relevant as the global CO trend weakens. We also examine the CO trends in monthly percentile values to understand seasonal implications and find that local changes in biomass burning are sufficiently strong to counteract the global downward trend in atmospheric CO, particularly in late summer.
Decadal trends and interannual variations in the hydroxyl radical (OH), while poorly constrained at present, are critical for understanding the observed evolution of atmospheric methane (CH4). Through analyzing the OH fields simulated by the model ensemble of the Chemistry–Climate Model Initiative (CCMI), we find (1) the negative OH anomalies during the El Niño years mainly corresponding to the enhanced carbon monoxide (CO) emissions from biomass burning and (2) a positive OH trend during 1980–2010 dominated by the elevated primary production and the reduced loss of OH due to decreasing CO after 2000. Both two-box model inversions and variational 4D inversions suggest that ignoring the negative anomaly of OH during the El Niño years leads to a large overestimation of the increase in global CH4 emissions by up to 10 ± 3 Tg yr-1 to match the observed CH4 increase over these years. Not accounting for the increasing OH trends given by the CCMI models leads to an underestimation of the CH4 emission increase by 23 ± 9 Tg yr-1 from 1986 to 2010. The variational-inversion-estimated CH4 emissions show that the tropical regions contribute most to the uncertainties related to OH. This study highlights the significant impact of climate and chemical feedbacks related to OH on the top-down estimates of the global CH4 budget.
Fire is an integral part of Earth system that links regional and global biogeochemical cycles, human activities, and ecosystems. Global estimates for biomass burning indicate that Africa is responsible for ~70% of global burned area and ~50% of fire-related carbon emissions. Previous studies have documented an overall decline in burned area in the African continent, but changes in fire patterns, such as the frequency and size of different fire categories, have not been assessed. In this study, long-term fire trends were investigated using the latest burned area data from the MODerate resolution Imaging Spectroradiometer (MODIS) and the Global Fire Emission Database (GFED4s) over Central Africa (10°E-40°E, 15°N-15°S). A 3-D (latitude, longitude, time) connected-component labeling algorithm was applied to identify individual fires and their size. Results show a decline in burned area by 2.7-3.2 Mha yr-1 (~1.3% yr-1) for the period 2003-2017, particularly in northern Central Africa. This decline was attributed to significant decreases in both fire frequency and size, particularly for large fires (> 100 ha) which contribute to ~90% of the total burned area. Burned area declined in tropical savannas and grasslands but increased at the edges of the Congolese rainforest. A random forest regression model was applied to quantify influences of climatic conditions, fuel availability, and agricultural activity on burned area changes. Overall, suppressed fuel, increased dry season length, and decreased rainfall contributed to significant declines in burned area in savannas and grasslands. In the edges of the southern Congolese rainforest, suppressed rainfall and warmer temperature were responsible for the increased burned area.
Given its relatively long lifetime in the troposphere, carbon monoxide (CO) is commonly employed as a tracer for characterizing airborne pollutant distributions. The present study aims to estimate the spatiotemporal distributions of ground-level CO concentrations across China during 2013–2016. We refined the random-forest–spatiotemporal kriging (RF–STK) model to simulate the daily CO concentrations on a 0.1∘ grid based on the extensive CO monitoring data and the Measurements of Pollution in the Troposphere CO retrievals (MOPITT CO). The RF–STK model alleviated the negative effects of sampling bias and variance heterogeneity on the model training, with cross-validation R2 of 0.51 and 0.71 for predicting the daily and multiyear average CO concentrations, respectively. The national population-weighted average CO concentrations were predicted to be 0.99±0.30 mg m-3 (μ±σ) and showed decreasing trends over all regions of China at a rate of -0.021±0.004 mg m-3 yr-1. The CO pollution was more severe in North China (1.19±0.30 mg m-3), and the predicted patterns were generally consistent with MOPITT CO. The hotspots in the central Tibetan Plateau where the CO concentrations were underestimated by MOPITT CO were apparent in the RF–STK predictions. This comprehensive dataset of ground-level CO concentrations is valuable for air quality management in China.
Atmospheric carbon monoxide (CO) concentrations have been decreasing since 2000, as observed by both satellite- and ground-based instruments, but global bottom-up emission inventories estimate increasing anthropogenic CO emissions concurrently. In this study, we use a multi-species atmospheric Bayesian inversion approach to attribute satellite-observed atmospheric CO variations to its sources and sinks in order to achieve a full closure of the global CO budget during 2000–2017. Our observation constraints include satellite retrievals of the total column mole fraction of CO, formaldehyde (HCHO), and methane (CH4) that are all major components of the atmospheric CO cycle. Three inversions (i.e., 2000–2017, 2005–2017, and 2010–2017) are performed to use the observation data to the maximum extent possible as they become available and assess the consistency of inversion results to the assimilation of more trace gas species. We identify a declining trend in the global CO budget since 2000 (three inversions are broadly consistent during overlapping periods), driven by reduced anthropogenic emissions in the US and Europe (both likely from the transport sector), and in China (likely from industry and residential sectors), as well as by reduced biomass burning emissions globally, especially in equatorial Africa (associated with reduced burned areas). We show that the trends and drivers of the inversion-based CO budget are not affected by the inter-annual variation assumed for prior CO fluxes. All three inversions contradict the global bottom-up inventories in the world's top two emitters: for the sign of anthropogenic emission trends in China (e.g., here -0.8±0.5 % yr-1 since 2000, while the prior gives 1.3±0.4 % yr-1) and for the rate of anthropogenic emission increase in South Asia (e.g., here 1.0±0.6 % yr-1 since 2000, smaller than 3.5±0.4 % yr-1 in the prior inventory). The posterior model CO concentrations and trends agree well with independent ground-based observations and correct the prior model bias. The comparison of the three inversions with different observation constraints further suggests that the most complete constrained inversion that assimilates CO, HCHO, and CH4 has a good representation of the global CO budget, and therefore matches best with independent observations, while the inversion only assimilating CO tends to underestimate both the decrease in anthropogenic CO emissions and the increase in the CO chemical production. The global CO budget data from all three inversions in this study can be accessed from 10.6084/m9.figshare.c.4454453.v1 (Zheng et al., 2019).
Catalytic conversion of carbon monoxide (CO) is one of the most important process for human health protection. CO is also called the unnoticed poisons and silent killer of 21st century. The effect of inhaling CO can cause of hypoxic injury, neurological break and even death. Due to CO poisoning decay vegetation life and increases in global warming and ozone layer depletion. CO is produced into the environment by partial oxidation of carbon containing compounds. The main source of CO emission is the transportation sector. Thus, the oxidation of poisonous CO to nonpoisonous CO2 at ambient conditions is crucial for life conservation in many applications. Further, low-temperature CO oxidation is vital in minimizing emissions at the cold start of an internal combustion engine. A variety of CO oxidation catalysts are investigated in this era, but a maximum of them have problems associated with the deactivation in presence of moisture, cost-effective, lower stability, poison resistance, availability in the world. These accelerate the investigation of CO oxidation over various catalysts. Although there are numerous research articles present on this topic until now no one review are present for this demanding issue. So there is a space in this area, it has been made an attempt to seal this hole by this review. Keywords: Carbon monoxide, Poisonous, Source, Catalyst, Parameters and applications
China has been the largest vehicle market in the world since 2009. The stalemate between the rapid development of the vehicle industry and delayed vehicle emission control has become increasingly prominent. Vehicle emission has become a significant source of air pollution in China's cities. Understanding the current barriers in the vehicle industry is necessary for the development of effective and sustainable measures and policy to manage vehicle-induced air pollution. This review provides insight into the circumstances and causes of vehicle-induced air pollution and outlines recent progress in policy-makers' long-term strategies and regulations. The development of an integrated mechanism of social participation, technical revolution, and regulatory innovation in vehicles, fuel, and roads is suggested to break the stalemate between air pollution and the automobile boom in China; the implications of this review extend to other countries facing the similar atmospheric pollution problems. Subjects Environmental
Extensive fossil fuel combustion in rapidly developing cities severely affects air quality and public health. We report observational evidence of decadal changes in the efficiency and cleanness of bulk combustion over large cities in mainland China. In order to estimate the trends in enhancement ratios of CO and SO2 to NO2 (ΔCO/ΔNO2 and ΔSO2/ΔNO2) and infer emergent bulk combustion properties over these cities, we combine air quality retrievals from widely used satellite instruments across 2005–2014. We present results for four Chinese cities (Shenyang, Beijing, Shanghai, and Shenzhen) representing four levels of urban development. Our results show a robust coherent progression of declining to growing ΔCO/ΔNO2 relative to 2005 (-5.4±0.7 to +8.3±3.1% yr-1) and slowly declining ΔSO2/ΔNO2 (-6.0±1.0 to -3.4±1.0 % yr-1) across the four cities. The coherent progression we find is not evident in the trends of emission ratios reported in Representative Concentration Pathway (RCP8.5) inventory. This progression is likely due to a shift towards cleaner combustion from industrial and residential sectors in Shanghai and Shenzhen that is not yet seen in Shenyang and Beijing. This overall trend is presently obfuscated by China's still relatively higher dependence on coal. Such progression is well-correlated with economic development and traces a common emission pathway that resembles evolution of air pollution in more developed cities. Our results highlight the utility of augmenting observing and modeling capabilities by exploiting enhancement ratios in constraining the time variation in emission ratios in current inventories. As cities and/or countries continue to socioeconomically develop, the ability to monitor combustion efficiency and effectiveness of pollution control becomes increasingly important in assessing sustainable control strategies.
The new version of the Emissions Database for Global Atmospheric Research (EDGAR v4.3.2) compiles gaseous and particulate air pollutant emissions, making use of the same anthropogenic sectors, time period (1970–2012), and international activity data that is used for estimating GHG emissions, as described in a companion paper (Janssens-Maenhout et al., 2017). All human activities, except large scale biomass burning and land use, land-use change, and forestry are included in the emissions calculation. The bottom-up compilation methodology of sector-specific emissions was applied consistently for all world countries, providing methodological transparency and comparability between countries. In addition to the activity data used to estimate GHG emissions, air pollutant emissions are determined by the process technology and end-of-pipe emission reduction abatements. Region-specific emission factors and abatement measures were selected from recent available scientific literature and reports. Compared to previous versions of EDGAR, the EDGAR v4.3.2 dataset covers all gaseous and particulate air pollutants, has extended time series (1970–2012), and has been evaluated with quality control and quality assurance (QC and QA) procedures both for the emission time series (e.g. particulate matter – PM – mass balance, gap-filling for missing data, the split-up of countries over time, few updates in the emission factors, etc.) and grid maps (full coverage of the world, complete mapping of EDGAR emissions with sector-specific proxies, etc.). This publication focuses on the gaseous air pollutants of CO, NOx, SO2, total non-methane volatile organic compounds (NMVOCs), NH3, and the aerosols PM10, PM2.5, black carbon (BC), and organic carbon (OC). Considering the 1970–2012 time period, global emissions of SO2 increased from 99 to 103 Mt, CO from 441 to 562 Mt, NOx from 68 to 122 Mt, NMVOC from 119 to 170 Mt, NH3 from 25 to 59 Mt, PM10 from 37 to 65 Mt, PM2.5 from 24 to 41 Mt, BC from 2.7 to 4.5 Mt, and OC from 9 to 11 Mt. We present the country-specific emission totals and analyze the larger emitting countries (including the European Union) to provide insights on major sector contributions. In addition, per capita and per GDP emissions and implied emission factors – the apparent emissions per unit of production or energy consumption – are presented. We find that the implied emission factors (EFs) are higher for low-income countries compared to high-income countries, but in both cases decrease from 1970 to 2012. The comparison with other global inventories, such as the Hemispheric Transport of Air Pollution Inventory (HTAP v2.2) and the Community Emission Data System (CEDS), reveals insights on the uncertainties as well as the impact of data revisions (e.g. activity data, emission factors, etc.). As an additional metric, we analyze the emission ratios of some pollutants to CO2 (e.g. CO/CO2, NOx/CO2, NOx/CO, and SO2/CO2) by sector, region, and time to identify any decoupling of air pollutant emissions from energy production activities and to demonstrate the potential of such ratios to compare to satellite-derived emission data. Gridded emissions are also made available for the 1970–2012 historic time series, disaggregated for 26 anthropogenic sectors using updated spatial proxies. The analysis of the evolution of hot spots over time allowed us to identify areas with growing emissions and where emissions should be constrained to improve global air quality (e.g. China, India, the Middle East, and some South American countries are often characterized by high emitting areas that are changing rapidly compared to Europe or the USA, where stable or decreasing emissions are evaluated). Sector- and component-specific contributions to grid-cell emissions may help the modelling and satellite communities to disaggregate atmospheric column amounts and concentrations into main emitting sectors. This work addresses not only the emission inventory and modelling communities, but also aims to broaden the usefulness of information available in a global emission inventory such as EDGAR to also include the measurement community. Data are publicly available online through the EDGAR website http://edgar.jrc.ec.europa.eu/overview.php?v=432_AP and registered under 10.2904/JRC_DATASET_EDGAR.
Measurements of Pollution in the Troposphere (MOPITT) satellite and ground-based carbon monoxide (CO) measurements both suggest a widespread downward trend in CO concentrations over East Asia during the period 2005–2016. This negative trend is inconsistent with global bottom-up inventories of CO emissions, which show a small increase or stable emissions in this region. We try to reconcile the observed CO trend with emission inventories using an atmospheric inversion of the MOPITT CO data that estimates emissions from primary sources, secondary production, and chemical sinks of CO. The atmospheric inversion indicates a ~ −2% yr⁻¹ decrease in emissions from primary sources in East Asia from 2005–2016. The decreasing emissions are mainly caused by source reductions in China. The regional MEIC inventory for China is the only bottom up estimate consistent with the inversion-diagnosed decrease of CO emissions. According to the MEIC data, decreasing CO emissions from four main sectors (iron and steel industries, residential sources, gasoline-powered vehicles, and construction materials industries) in China explain 76% of the inversion-based trend of East Asian CO emissions. This result suggests that global inventories underestimate the recent decrease of CO emission factors in China which occurred despite increasing consumption of carbon-based fuels, and is driven by rapid technological changes with improved combustion efficiency and emission control measures.
We present a new data set of annual historical (1750–2014) anthropogenic chemically reactive gases (CO, CH4, NH3, NOx, SO2, NMVOCs), carbonaceous aerosols (black carbon – BC, and organic carbon – OC), and CO2 developed with the Community Emissions Data System (CEDS). We improve upon existing inventories with a more consistent and reproducible methodology applied to all emission species, updated emission factors, and recent estimates through 2014. The data system relies on existing energy consumption data sets and regional and country-specific inventories to produce trends over recent decades. All emission species are consistently estimated using the same activity data over all time periods. Emissions are provided on an annual basis at the level of country and sector and gridded with monthly seasonality. These estimates are comparable to, but generally slightly higher than, existing global inventories. Emissions over the most recent years are more uncertain, particularly in low- and middle-income regions where country-specific emission inventories are less available. Future work will involve refining and updating these emission estimates, estimating emissions' uncertainty, and publication of the system as open-source software.
Burn less, baby, burn less
Humans have, and always have had, a major impact on wildfire activity, which is expected to increase in our warming world. Andela et al. use satellite data to show that, unexpectedly, global burned area declined by ∼25% over the past 18 years, despite the influence of climate. The decrease has been largest in savannas and grasslands because of agricultural expansion and intensification. The decline of burned area has consequences for predictions of future changes to the atmosphere, vegetation, and the terrestrial carbon sink.
Science , this issue p. 1356
Long-term measurements from satellites and surface stations have demonstrated a decreasing trend of tropospheric carbon monoxide (CO) in the Northern Hemisphere over the past decade. Likely explanations for this decrease include changes in anthropogenic, fires, and/or biogenic emissions or changes in the primary chemical sink hydroxyl radical (OH). Using remotely sensed CO measurements from the Measurement of Pollution in the Troposphere (MOPITT) satellite instrument, in situ methyl chloroform (MCF) measurements from the World Data Centre for Greenhouse Gases (WDCGG) and the adjoint of the GEOS-Chem model, we estimate the change in global CO emissions from 2001 to 2015. We show that the loss rate of MCF varied by 0.2 % in the past 15 years, indicating that changes in global OH distributions do not explain the recent decrease in CO. Our two-step inversion approach for estimating CO emissions is intended to mitigate the effect of bias errors in the MOPITT data as well as model errors in transport and chemistry, which are the primary factors contributing to the uncertainties when quantifying CO emissions using these remotely sensed data. Our results confirm that the decreasing trend of tropospheric CO in the Northern Hemisphere is due to decreasing CO emissions from anthropogenic and biomass burning sources. In particular, we find decreasing CO emissions from the United States and China in the past 15 years, and unchanged anthropogenic CO emissions from Europe since 2008. We find decreasing trends of biomass burning CO emissions from boreal North America, boreal Asia and South America, but little change over Africa. In contrast to prior results, we find that a positive trend in CO emissions is likely for India and southeast Asia.
The quantification of carbon monoxide (CO) emissions is necessary for atmospheric research and has been studied extensively. Aiming to build an inventory with both high spatial resolution and detailed source information, this study estimated the monthly nation-level CO emissions from 79 major sources from 1960 to 2013, based on which a 0.1° × 0.1° gridded emission map was developed for 2011 using a recent energy product. The high sectorial resolution of this inventory can help scientists to study the influence of socioeconomic development on emissions, help decision makers to formulate abatement strategies, and potentially benefit emission-reduction scenario modeling and cost-benefit analysis. Our estimate for 2011 was 888.17 Tg (745.67 Tg–1112.80 Tg), with a much higher contribution from anthropogenic activities (68 %) than wildfire and deforestation (32 %). The anthropogenic emissions in recent years were dominated by developing countries due to the continuously increasing industrial production intensity and/or population explosion. Further discussion of the spatial and temporal variation of emissions was conducted, and a decreased emission intensity was observed, which was attributed to related policies and technological progress.
We have updated the Regional Emission inventory in ASia (REAS) as version
2.1. REAS 2.1 includes most major air pollutants and greenhouse gases from
each year during 2000 and 2008 and following areas of Asia: East, Southeast,
South, and Central Asia and the Asian part of Russia. Emissions are estimated
for each country and region using updated activity data and parameters.
Monthly gridded data with a 0.25° × 0.25°
resolution are also provided. Asian emissions for each species in 2008 are as
follows (with their growth rate from 2000 to 2008): 56.9 Tg (+34%) for
SO2, 53.9 Tg (+54%) for NOx, 359.5 Tg (+34%) for CO,
68.5 Tg (+46%) for non-methane volatile organic compounds, 32.8 Tg
(+17%) for NH3, 36.4 Tg (+45%) for PM10, 24.7 Tg (+42%)
for PM2.5, 3.03 Tg (+35%) for black carbon, 7.72 Tg (+21%) for
organic carbon, 182.2 Tg (+32%) for CH4, 5.80 Tg (+18%) for
N2O, and 16.0 Pg (+57%) for CO2. By country, China and India were
respectively the largest and second largest contributors to Asian emissions.
Both countries also had higher growth rates in emissions than others because
of their continuous increases in energy consumption, industrial activities,
and infrastructure development. In China, emission mitigation measures have
been implemented gradually. Emissions of SO2 in China increased from
2000 to 2006 and then began to decrease as flue-gas desulphurization was
installed to large power plants. On the other hand, emissions of air
pollutants in total East Asia except for China decreased from 2000 to 2008
owing to lower economic growth rates and more effective emission regulations
in Japan, South Korea, and Taiwan. Emissions from other regions generally
increased from 2000 to 2008, although their relative shares of total Asian
emissions are smaller than those of China and India. Tables of annual
emissions by country and region broken down by sub-sector and fuel type, and
monthly gridded emission data with a resolution of 0.25° × 0.25° for the major sectors are available
from the following URL: http://www.nies.go.jp/REAS/.
Negative trends of carbon monoxide (CO) concentrations are observed in the
recent decade by both surface measurements and satellite retrievals over many
regions of the globe, but they are not well explained by current emission
inventories. Here, we analyse the observed CO concentration decline with an
atmospheric inversion that simultaneously optimizes the two main CO sources
(surface emissions and atmospheric hydrocarbon oxidations) and the main CO
sink (atmospheric hydroxyl radical OH oxidation). Satellite CO column
retrievals from Measurements of Pollution in the Troposphere (MOPITT),
version 6, and surface observations of methane and methyl chloroform mole
fractions are assimilated jointly for the period covering 2002–2011.
Compared to the model simulation prescribed with prior emission inventories,
trends in the optimized CO concentrations show better agreement with that of
independent surface in situ measurements. At the global scale, the
atmospheric inversion primarily interprets the CO concentration decline as a
decrease in the CO emissions (−2.3 % yr−1), more than twice the
negative trend estimated by the prior emission inventories
(−1.0 % yr−1). The spatial distribution of the inferred decrease
in CO emissions indicates contributions from western Europe
(−4.0 % yr−1), the United States (−4.6 % yr−1) and
East Asia (−1.2 % yr−1), where anthropogenic fuel combustion
generally dominates the overall CO emissions, and also from Australia
(−5.3 % yr−1), the Indo-China Peninsula
(−5.6 % yr−1), Indonesia (−6.7 % y−1), and South
America (−3 % yr−1), where CO emissions are mostly due to biomass
burning. In contradiction with the bottom-up inventories that report an
increase of 2 % yr−1 over China during the study period, a
significant emission decrease of 1.1 % yr−1 is inferred by the
inversion. A large decrease in CO emission factors due to technology
improvements would outweigh the increase in carbon fuel combustions and may
explain this decrease. Independent satellite formaldehyde (CH2O) column
retrievals confirm the absence of large-scale trends in the atmospheric
source of CO. However, it should be noted that the CH2O retrievals are
not assimilated and OH concentrations are optimized at a very large scale in
this study.
A B S T R A C T We analysed ozone and carbon monoxide profiles measured by commercial aircrafts from the MOZAIC/ IAGOS fleet, during ascending and descending flights over Caracas, in Venezuela, from. For ozone, results showed a clean atmosphere over Caracas presenting the highest seasonal mean in March, April and May. Backward trajectory analyses with FLEXPART, of case studies for which the measured concentrations were high, showed that contributions from local, Central and North America, the Caribbean and Africa either from anthropogenic emissions, biomass burning or lightning were possible. Satellite products as fire counts from MODIS, lightning flash rates from LIS, and CO and O 3 from Infrared Atmospheric Sounding Interferometer and wind maps at different levels helped corroborate previous findings. Sensitivity studies performed with the chemical transport model GEOS-Chem captured the effect of anthropogenic emissions but underestimated the influence of biomass burning, which could be due to an underestimation of GFEDv2 emission inventory. The model detected the contribution of lightning from Africa in JJA and SON and from South America in DJF, possibly from the northeast of Brazil. Over Saõ Paulo and Rio de Janeiro, GEOS-Chem captured the seasonal variability of lightning produced in South America and attributed this source as the most important in this region, except in JJA, when anthropogenic emissions were addressed as the more impacting source of ozone precursors. However, comparison with the measurements indicated that the model overestimated ozone formation, which could be due to the convective parameterisation or the stratospheric influence. The highest ozone concentration was observed during September to November, but the model attributed only a small influence of biomass burning from South America, with no contribution of long-range transport from Africa. This paper is part of a Special Issue on MOZAIC-IAGOS in Tellus B celebrating 20 years of an ongoing air chemistry climate research measurements from airbus commerical aircraft operated by an international consortium of countries. More papers from this issue can be found at http://www.tellusb.net
Roughly 15% of the Brazilian Amazon was deforested between 1976 and 2010. Fire is the dominant method through which forests and vegetation are cleared. Fires emit large quantities of particulate matter into the atmosphere, which degrades air quality and affects human health. Since 2004, Brazil has achieved substantial reductions in deforestation rates and associated deforestation fires. Here we assess the impact of this reduction on air quality and human health during non-drought years between 2001 and 2012. We analyse aerosol optical depth measurements obtained with satellite and ground-based sensors over southwest Brazil and Bolivia for the dry season, from August to October. We find that observed dry season aerosol optical depths are more than a factor of two lower in years with low deforestation rates in Brazil. We used a global aerosol model to show that reductions in fires associated with deforestation have caused mean surface particulate matter concentrations to decline by ∼30% during the dry season in the region. Using particulate matter concentration response functions from the epidemiological literature, we estimate that this reduction in particulate matter may be preventing roughly 400 to 1,700 premature adult deaths annually across South America.
[1] Urban areas are large sources of several air pollutants, with carbon monoxide (CO) among the largest. Yet measurement from space of their CO emissions remains elusive due to its long lifetime. Here we introduce a new method of estimating relative changes in CO emissions over megacities. A new multichannel Measurements of Pollution in the Troposphere (MOPITT) CO data product, offering improved sensitivity to the boundary layer, is used to estimate this relative change over eight megacities: Moscow, Paris, Mexico, Tehran, Baghdad, Los Angeles, Sao Paulo, and Delhi. By combining MOPITT observations with wind information from a meteorological reanalysis, changes in the CO upwind-downwind difference are used as a proxy for changes in emissions. Most locations show a clear reduction in CO emission between 2000–2003 and 2004–2008, reaching −43% over Tehran and −47% over Baghdad. There is a contrasted agreement between these results and the MACCity and Emission Database for Global Atmospheric Research v4.2 inventories.
Background: Landscape fires in South America have considerable impacts on ecosystems, air quality and the climate system. We examined long-term trends and interannual variability of forest, savanna and agricultural fires for the continent during 2001–2012 using multiple satellite-derived fire products. Results: The annual number of active fires in tropical forests increased significantly during 2001–2005. Several satellite-derived metrics, including fire persistence, indicated that this trend was mostly driven by deforestation. Fires between 2005 and 2012 had a small decreasing trend and large year-to-year changes that were associated with climate extremes. Fires in savannas and evergreen forests increased in parallel during drought events in 2005, 2007 and 2010, suggesting similar regional climate controls on fire behavior. Deforestation fire intensity (the number of fires per unit of deforested area) increased significantly within the Brazilian Amazon in areas with small-scale deforestation. Conclusion: Fires associated with forest degradation are becoming an increasingly important component of the fire regime and associated carbon emissions.
This paper presents results of the inverse modeling of carbon monoxide surface sources on a monthly and regional basis using the MOPITT (Measurement Of the Pollution In The Troposphere) CO retrievals. The targeted time period is from April 2000 to March 2001. A sequential and time-dependent inversion scheme is implemented to correct an a priori set of monthly mean CO sources. The a posteriori estimates for the total anthropogenic (fossil fuel + biofuel + biomass burning) surface sources of CO in TgCO/yr are 509 in Asia, 267 in Africa, 140 in North America, 90 in Europe and 84 in Central and South America. Inverting on a monthly scale allows one to assess a corrected seasonality specific to each source type and each region. Forward CTM simulations with the a posteriori emissions show a substantial improvement of the agreement between modeled CO and independent in situ observations.
CO is a well-suited indicator for the transport of pollutants in the troposphere on a regional and global scale. For the study presented here, simulations of CO concentrations from a global chemistry transport model (MOZART-2), with the CO being tagged according to the emission type and the source region, have been used to diagnose the contributions of different processes and regions to the CO burden over Europe. Model simulations have been performed with both a priori emissions and an optimized set of CO surface emissions derived from the inversion of CO retrievals of the Measurements of Pollution in the Troposphere (MOPITT) remote sensing instrument. The annual mean difference between the modeled and the observed CO at 850 hPa over Europe is -38 +/- 13 ppb with the a priori set of emissions and -7 +/- 7 ppb when the optimized emissions are employed in the model. The general difficulties arising from an intercomparison of remote sensing data with model simulations are discussed. Besides data from MOPITT, ground-based CO measurements have been employed in the evaluation of the model and its emissions. The comparisons show that the model represents the background conditions as well as large-scale transport relatively well. The budget analysis reveals the predominant impact of the European emissions on CO concentrations near the surface, and a strong impact of sources from Asia and North America on the CO burden in the free troposphere over Europe. On average, the largest contribution (67%) to the anthropogenic (fossil and biofuel sources, biomass burning) CO at the surface originates from regional anthropogenic sources, but further significant impact is evident from North America (14%) and Asia (15%). With increasing altitude, anthropogenic CO from Asia and North America gains in importance, reaching maximum contributions of 32% for North American CO at 500 hPa and 50% for Asian CO at 200 hPa. The impact of European emissions weakens with increasing altitude (8% at 500 hPa).
Despite the importance of carbon monoxide (CO) for the overall oxidative capacity of the atmosphere, there is still considerable uncertainty in ambient measurements of CO. To address this issue, an inter-comparison between four different measurement techniques was made over a period of two months at the high-alpine site Jungfraujoch (JFJ), Switzerland. The measurement techniques were Non-dispersive Infrared Absorption (NDIR), Vacuum UV Resonance Fluorescence (VURF), gas chromatographic separation with a mercuric oxide reduction detector (GC/HgO), and gas chromatographic separation followed by reduction on a nickel catalyst and analysis by a flame ionization detector (GC/FID). The agreement among all techniques was better than 2% for one-hourly averages, which confirmed the suitability of the NDIR method for CO measurements even at remote sites. The inter-comparison added to the validation of the 12-year record (1996-2007) of continuous CO measurements at JFJ. To date this is one of the longest time series of continuous CO measurements in the free troposphere over Central Europe. This data record was further investigated with a focus on trend analysis. A significant negative trend was observed at JFJ showing a decrease of 21.4±0.3% over the investigated period, or an average annual decrease of 1.78%/yr (2.65±0.04 ppb/yr). These results were compared with emission inventory data reported to the Long-range Transboundary Air Pollution (LRTAP) Convention. It could be shown that long range transport significantly influences the CO levels observed at JFJ, with air masses of non-European origin contributing at least one third of the observed mole fractions.
Chinese radiosonde data from 1970 to 1990 are relatively homogeneous in time and are used to examine the climatology, trends, and variability of China's atmospheric water vapor content. The climatological distribution of precipitable water (PW) is primarily dependent on surface temperature. Influenced by the east Asia monsoon, China's precipitable water exhibits very large seasonal variations. Station elevation is also a dominant factor affecting water vapor distribution in China.An increase (decrease) in precipitable water over China is associated with an increase (decrease) of precipitation in most regions. Increases in the percentage of PW relative to climatology are greater in winter and spring than in summer and autumn.Interannual variation and trends in precipitable water and surface temperature are closely correlated in China, confirming a positive `greenhouse' feedback. Interannual variations between precipitable water and precipitation are also significantly correlated.
Atmospheric carbon monoxide (CO) distributions are controlled by
anthropogenic emissions, biomass burning, transport and oxidation by
reaction with the hydroxyl radical (OH). Quantifying trends in CO is
therefore important for understanding changes related to all of these
contributions. Here we present a comprehensive record of satellite
observations from 2000 through 2011 of total column CO using the
available measurements from nadir-viewing thermal infrared instruments:
MOPITT, AIRS, TES and IASI. We examine trends for CO in the Northern and
Southern Hemispheres along with regional trends for Eastern China,
Eastern USA, Europe and India. We find that all the satellite
observations are consistent with a modest decreasing trend ∼-1%
yr-1 in total column CO over the Northern Hemisphere for this
time period and a less significant, but still decreasing trend in the
Southern Hemisphere. Although decreasing trends in the United States and
Europe have been observed from surface CO measurements, we also find a
decrease in CO over E. China that, to our knowledge, has not been
reported previously. Some of the interannual variability in the
observations can be explained by global fire emissions, but the overall
decrease needs further study to understand the implications for changes
in anthropogenic emissions.
Trends in the CO andC2H6 partial columns ~0-15 km)
have been estimated from four European ground-based solar FTIR (Fourier
Transform InfraRed) stations for the 1996-2006 time period. The CO
trends from the four stations Jungfraujoch, Zugspitze, Harestua and
Kiruna have been estimated to -0.45 ± 0.16% yr-1,
-1.00 ± 0.24% yr-1, -0.62 ± 0.19 %
yr-1 and -0.61 ± 0.16% yr-1, respectively.
The corresponding trends for C2H6 are -1.51
± 0.23% yr-1, -2.11 ± 0.30% yr-1,
-1.09 ± 0.25% yr-1 and -1.14 ± 0.18%
yr-1. All trends are presented with their 2-σ
confidence intervals. To find possible reasons for the CO trends, the
global-scale EMEP MSC-W chemical transport model has been used in a
series of sensitivity scenarios. It is shown that the trends are
consistent with the combination of a 20% decrease in the anthropogenic
CO emissions seen in Europe and North America during the 1996-2006
period and a 20% increase in the anthropogenic CO emissions in East
Asia, during the same time period. The possible impacts of
CH4 and biogenic volatile organic compounds (BVOCs) are also
considered. The European and global-scale EMEP models have been
evaluated against the measured CO and C2H6 partial
columns from Jungfraujoch, Zugspitze, Bremen, Harestua, Kiruna and
Ny-Ålesund. The European model reproduces, on average the
measurements at the different sites fairly well and within 10-22%
deviation for CO and 14-31% deviation for C2H6.
Their seasonal amplitude is captured within 6-35% and 9-124% for CO and
C2H6, respectively. However, 61-98% of the CO and
C2H6 partial columns in the European model are
shown to arise from the boundary conditions, making the global-scale
model a more suitable alternative when modeling these two species. In
the evaluation of the global model the average partial columns for 2006
are shown to be within 1-9% and 37-50% of the measurements for CO and
C2H6, respectively. The global model sensitivity
for assumptions made in this paper is also analyzed.
Since 1988, the distribution of carbon monoxide (CO) in the lower troposphere has been determined using a globally distributed air sampling network. Site locations range from 82 oN to 90 ø S, with wide longitudinal coverage, and represent the marine boundary layer, regionally polluted atmospheres, and the free troposphere. These measurements present a unique, intercalibrated, and internally consistent data set that are used to better define the global temporal and spatial distribution of CO. In this paper, times series from 49 sites are discussed. With an average lifetime of-2 months, CO showed significant concentration gradients. In the marine boundary layer, mixing ratios were greatest in the northern winter (200-220 ppb) and lowest in the southern summer (35-45 ppb). The interhemispheric gradient showed strong seasonality with a maximum difference between the high latitudes of the northern and southern hemispheres (160-180 ppb) in February and March and a minimum in July and August (10-20 ppb). Higher CO was found in regions near human development relative to those over more remote areas. The distributions provide additional evidence of the widespread pollution of the lower atmosphere. Remote areas in the high northern hemisphere are polluted by anthropogenic activities in the middle latitudes, and those in the southern hemisphere are heavily influenced by the burning of biomass in the tropics. While tropospheric concentrations of CO exhibit periods of increase and decrease, the globally averaged CO mixing ratio over the period from 1990 through 1995 decreased at a rate of approximately 2 ppb yr-1.
We used day-side Measurement of Pollution in the Troposphere (MOPITT) carbon monoxide (CO) retrievals (2000–2007) to examine the regional CO emission and its transport pathways during the summer/winter monsoon, with a specific focus on the Indian-subcontinent. It is observed that MOPITT CO retrievals at 850 hPa level in general show large scale features of CO emission in India, as reflected in the bottom-up inventory. In particular, high CO mixing ratios over the eastern north-eastern part of India, along the Indo-Gangetic (IG) region, and low CO mixing ratios over central India are generally captured from the MOPITT data. A strong plume with enhanced CO mixing ratios at 350 hPa is observed during the summer monsoon, demonstrating large scale vertical transport of the boundary layer CO from the Indian region into the upper troposphere. During winter outflow CO from the Indian region is found to be transported over the Arabian Sea and Bay of Bengal and reaches up to Saudi Arabia and north-eastern Africa. It is observed that emissions from Southeast Asia and the eastern north-eastern Indian region have the greatest impact over the Bay of Bengal and the eastern Indian Ocean, while emissions from the rest of India dominate over the Arabian Sea and the western Indian Ocean.
Several different inventories of global and regional anthropogenic and biomass burning emissions are assessed for the 1980–2010
period. The species considered in this study are carbon monoxide, nitrogen oxides, sulfur dioxide and black carbon. The inventories
considered include the ACCMIP historical emissions developed in support of the simulations for the IPCC AR5 assessment. Emissions
for 2005 and 2010 from the Representative Concentration Pathways (RCPs) are also included. Large discrepancies between the
global and regional emissions are identified, which shows that there is still no consensus on the best estimates for surface
emissions of atmospheric compounds. At the global scale, anthropogenic emissions of CO, NOx and SO2 show the best agreement for most years, although agreement does not necessarily mean that uncertainty is low. The agreement
is low for BC emissions, particularly in the period prior to 2000. The best consensus is for NOx emissions for all periods and all regions, except for China, where emissions in 1980 and 1990 need to be better defined.
Emissions of CO need better quantification in the USA and India for all periods; in Central Europe, the evolution of emissions
during the past two decades needs to be better determined. The agreement between the different SO2 emissions datasets is rather good for the USA, but better quantification is needed elsewhere, particularly for Central Europe,
India and China. The comparisons performed in this study show that the use of RCP8.5 for the extension of the ACCMIP inventory
beyond 2000 is reasonable, until more global or regional estimates become available. Concerning biomass burning emissions,
most inventories agree within 50–80%, depending on the year and season. The large differences between biomass burning inventories
are due to differences in the estimates of burned areas from the different available products, as well as in the amount of
biomass burned.
The first global tropospheric forecasts of O3 and its precursors have been used in the daily flight planning of field measurement campaigns. The 3-D chemistry-transport model MATCH-MPIC is driven by meteorological data from a weather center (NCEP) to produce daily 3-day forecasts of the global distributions of O3 and related gases, as well as regional CO tracers. This paper describes the forecast system and its use in three field campaigns, MINOS, CONTRACE and INDOEX. An overview is given of the forecasts by MATCH-MPIC and by three other chemical weather forecast models (EURAD, ECHAM, and FLEXPART), focusing on O3 and CO. Total CO and regional CO tracers were found to be the most valuable gases for flight planning, due to their relatively well-defined anthropogenic source regions and lifetimes of one to a few months. CO was in good agreement with the observations on nearly all the flights (generally r > 0.7, and the relative RMS differences for the deviations from the means was less than 20%). In every case in which the chemical weather forecasts were primarily responsible for the flight plans, the targeted features were observed. Three forecasted phenomena are discussed in detail: outflow from Asia observed in the Mediterranean upper troposphere during MINOS, outflow from North America observed in the middle troposphere over northern Europe during CONTRACE, and the location of the "chemical ITCZ'' over the Indian Ocean during INDOEX. In particular it is shown that although intercontinental pollution plumes such as those observed during MINOS and CONTRACE occur repeatedly during the months around the campaigns, their frequency is sufficiently low (~10--30% of the time) that global chemical weather forecasts are important for enabling them to be observed during limited-duration field campaigns. The MATCH-MPIC chemical weather forecasts, including an interface for making customized figures from the output, are available for community use via http://www.mpch-mainz.mpg.de/~lawrence/forecasts.html .
The MOPITT (Measurements of Pollution in the Troposphere) instrument has provided more than nine years of global carbon monoxide (CO) measurements on a continuous basis since its launch aboard the Terra Spacecraft on December 18th, 1999. This paper gives an overview of the core sub-system performance and major issues of the in-flight instrument over the mission period. Some of the instrument anomalies are also discussed. The major successes are: (1) the concept of using a combination of correlation systems such as Length Modulated Cells (LMCs) and Pressure Modulated Cells (PMCs) to retrieve CO profiles in the troposphere; (2) the redundant design in the instrumentation which was crucial for coping with unexpected in-flight anomalies and for continuing the mission in the case of component failure; (3) the thermal environment on orbit that is so stable that some calibration procedures are not necessary; and (4) the recent production of CO total column retrieved from the MOPITT 2.3 μm channel.
Millennial-scale climatic variations have punctuated the Holocene characterised by abrupt changes from warm to cool or wetter to drier conditions. Amongst these climatic events, there is increased evidence for an abrupt multicentennial shift of climatic conditions around 3.8/3.7 kyr BP (4.1 cal. kyr BP) in mid- to low-latitude regions which had a profound impact on landscape and population migration. In the Mediterranean region, subtropical, tropical and equatorial Africa, a number of continental proxies (lake-levels, pollen sequences, stable isotopes) record this abrupt change towards drier conditions. However, regionalism in climatic conditions is reflected in the vegetation records, possibly in relation to orographic conditions and the influence of sea-surface conditions. Hitherto there have been very few marine sequences that record this particular climatic shift at high-resolution. We present here new data from the Congo deep-sea fan containing integrated marine and terrestrial proxies. Around 5–4 cal. kyr BP, shifts in surface conditions off the Congo River mouth are observed, with possible establishment of seasonal coastal upwelling, and lower sea-surface temperatures. In parallel, pollen data indicate fluctuations of herbaceous, afromontane taxa and charred grass cuticles, suggesting more open vegetation in the lowland regions and an increase in cloud forest and/or afromontane vegetation at higher altitudes within the Congolese region.
We analyze present-day and future carbon monoxide (CO) simulations in 26 state-of-the-art atmospheric chemistry models run to study future air quality and climate change. In comparison with near-global satellite observations from the MOPITT instrument and local surface measurements, the models show large underestimates of Northern Hemisphere (NH) extratropical CO, while typically performing reasonably well elsewhere. The results suggest that year-round emissions, probably from fossil fuel burning in east Asia and seasonal biomass burning emissions in south-central Africa, are greatly underestimated in current inventories such as IIASA and EDGAR3.2. Variability among models is large, likely resulting primarily from intermodel differences in representations and emissions of nonmethane volatile organic compounds (NMVOCs) and in hydrologic cycles, which affect OH and soluble hydrocarbon intermediates. Global mean projections of the 2030 CO response to emissions changes are quite robust. Global mean midtropospheric (500 hPa) CO increases by 12.6 +/- 3.5 ppbv (16%) for the high-emissions (A2) scenario, by 1.7 +/- 1.8 ppbv (2%) for the midrange (CLE) scenario, and decreases by 8.1 +/- 2.3 ppbv (11%) for the low-emissions (MFR) scenario. Projected 2030 climate changes decrease global 500 hPa CO by 1.4 +/- 1.4 ppbv. Local changes can be much larger. In response to climate change, substantial effects are seen in the tropics, but intermodel variability is quite large. The regional CO responses to emissions changes are robust across models, however. These range from decreases of 10-20 ppbv over much of the industrialized NH for the CLE scenario to CO increases worldwide and year-round under A2, with the largest changes over central Africa (20-30 ppbv), southern Brazil (20-35 ppbv) and south and east Asia (30-70 ppbv). The trajectory of future emissions thus has the potential to profoundly affect air quality over most of the world's populated areas.
As the hydroxyl radical (OH) is the cleansing agent of the atmosphere, reduction in its concentration is a great concern for air quality and transport of trace gases across the latitudes and altitudes. In addition, OH determines the lifetime of most trace gases and non-CO2 greenhouse gases in the atmosphere. Since many pollutants have adverse health effects and are greenhouse gases, the changes in OH concentrations directly or indirectly affect public health and climate. Our analysis with OH data (from Tropospheric Emission Spectrometer and Copernicus Atmosphere Monitoring Service reanalyses) for the past 14 (2005–2018) years finds an OH minimum region over Indian Ocean, in the eastern Bay of Bengal at 6°–14° N and 92°–95° E. The Indian Ocean OH minimum reaches to 15 × 104 molec.cm−3 in April, and a secondary minimum of 18 × 104 molec.cm−3 in September–November. This seasonal minimum found around the Andaman and Nicobar Islands also hosts an active volcano, which releases noticeable amount of SO2 (OH sink) throughout the year. In addition, the biomass burning in spring and thus, the distribution of CO has a profound influence on the OH distribution in this region as Southeast Asia is one of the global hotspots of biomass burning, and the Indian Ocean OH minimum is located near that region. The El Niño and La Niño events also control the tropospheric ozone and CO distribution, and thus the interannual variability of OH minimum there. The WACCM model simulations reproduce the general latitudinal distribution and average seasonal cycle of OH, but not the extreme minimum OH values, although the simulations show the annual minimum in winter (December–January) in both ocean regions, which demands dedicated studies using chemical transport models. Therefore, this study reveals a seasonal OH minimum over Indian Ocean, which is very likely to influence the regional air quality and trace gas transport in the tropics.
In the present study the diurnal, seasonal variability along with the comparison of ground-based and satellite retrieved carbon monoxide (CO) observations are reported at Agra in the central Indo-Gangetic Plain (IGP). In addition, the impact of long-range transport of emissions from crop residue burning region (Punjab and Haryana) on CO concentrations at a downwind site was determined. Previous studies reported so far in India have mainly focused on the impact of crop residue burning activities on CO concentrations in the nearby regions while the present study is an attempt to identify the impact of these activities on a downwind site situated several kilometers away. The average concentration of in-situ measured CO at Agra was 518.7 ± 487.9 ppb during 2015-2019. A good correlation between ground-based and satellite CO observations was found (y = 0.1 x + 129.4, R = 0.8). The highest seasonal average CO concentrations were observed during Oct-Nov, which corresponds with paddy residue burning in the north-west IGP (NW-IGP). These activities result in the emission of CO which can be transported to distant places due to its long lifetime (2 months) and can influence the air quality. It was observed that during the crop residue burning period the average concentrations of CO were higher by 19.8, 78.7 and 65.1%, respectively in 2015, 2017 and 2019. Backward air mass trajectories and potential source contribution function (PSCF) suggested crop residue burning activities can be the potential source of CO at the study site during the crop residue burning period.
To reduce the emissions from the iron and steel industry, China has imposed a series of strengthened emission standards since 2012. An accurate impact of emission reduction on the air quality is critical for evaluating policy efficiency. This study was the first attempt to explore the contribution of emissions from China's iron and steel industry to ambient air quality at national scale, after the implementation of current standards in 2012. First, all emission sources in production processes were estimated at unit level in China's iron and steel industry, covering sulfur dioxide (SO2), nitrogen oxides (NOx) and particulate matter (M2.5), etc. Second, the corresponding air quality impacts were modeled with the Comprehensive Air Quality Model with extensions (CAMx) model. We find that emission hotspots from China's iron and steel industry, with following aspects. (1)From a spatial perspective, the largest emissions and ambient concentration contributors were mainly concentrated in eastern areas of China, with high crude steel production. (2) Among three main pollutants (i.e., SO2, NOx and PM2.5), SO2 made the largest contribution to ambient concentration in China's iron and steel industry. (3) As for temporal distribution, emission sources presented the greatest contribution to air quality concentration in summer. (4) For policy evaluation, under the current standards in 2012, the contribution of iron and steel industry emissions to air quality decreased by 92.07% and 72.91% for SO2 and PM2.5, respectively. Therefore, these results will be essential to reflecting current emission characteristics and underscoring further opportunities for emission reductions.
Atmospheric ammonia (NH3) is an alkaline gas and a prominent constituent of the nitrogen cycle that adversely affects ecosystems at higher concentrations. It is a pollutant, which influences all three spheres such as haze formation in the atmosphere, soil acidification in the lithosphere, and eutrophication in water bodies. Atmospheric NH3 reacts with sulfur (SOx) and nitrogen (NOx) oxides to form aerosols, which eventually affect human health and climate. Here, we present the seasonal and inter-annual variability of atmospheric NH3 over India in 2008–2016 using the IASI (Infrared Atmospheric Sounding Interferometer) satellite observations. We find that Indo-Gangetic Plains (IGP) is one of the largest and rapidly growing NH3 hotspots of the world, with a growth rate of +1.2% yr⁻¹ in summer (June–August: Kharif season), due to intense agricultural activities and presence of many fertilizer industries there. However, our analyses show insignificant decreasing trends in annual NH3 of about −0.8% yr⁻¹ in all India, about −0.4% yr⁻¹ in IGP, and −1.0% yr⁻¹ in the rest of India. Ammonia is positively correlated with total fertilizer consumption (r = 0.75) and temperature (r = 0.5) since high temperature favors volatilization, and is anti-correlated with total precipitation (r = from −0.2, but −0.8 in the Rabi season: October–February) as wet deposition helps removal of atmospheric NH3. This study, henceforth, suggest the need for better fertilization practices and viable strategies to curb emissions, to alleviate the adverse health effects and negative impacts on the ecosystem in the region. On the other hand, the overall decreasing trend in atmospheric NH3 over India shows the positive actions and commitment to the national missions and action plans to reduce atmospheric pollution and changes in climate.
The Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), is the latest atmospheric reanalysis of the modern satellite era produced by NASA's Global Modeling and Assimilation Office (GMAO). MERRA-2 assimilates observation types not available to its predecessor, MERRA, and includes updates to the Goddard Earth Observing System (GEOS) model and analysis scheme so as to provide a viable ongoing climate analysis beyond MERRA's terminus. While addressing known limitations of MERRA, MERRA-2 is also intended to be a development milestone for a future integrated Earth system analysis (IESA) currently under development at GMAO. This paper provides an overview of the MERRA-2 system and various performance metrics. Among the advances in MERRA-2 relevant to IESA are the assimilation of aerosol observations, several improvements to the representation of the stratosphere including ozone, and improved representations of cryospheric processes. Other improvements in the quality of MERRA-2 compared with MERRA include the reduction of some spurious trends and jumps related to changes in the observing system and reduced biases and imbalances in aspects of the water cycle. Remaining deficiencies are also identified. Production of MERRA-2 began in June 2014 in four processing streams and converged to a single near-real-time stream in mid-2015. MERRA-2 products are accessible online through the NASA Goddard Earth Sciences Data Information Services Center (GES DISC).
HYSPLIT, developed by NOAA’s Air Resources Laboratory, is one of the most widely used models for atmospheric trajectory and dispersion calculations. We present the model’s historical evolution over the last 30 years from simple hand drawn back trajectories to very sophisticated computations of transport, mixing, chemical transformation, and deposition of pollutants and hazardous materials. We highlight recent applications of the HYSPLIT modeling system, including the simulation of atmospheric tracer release experiments, radionuclides, smoke originated from wild fires, volcanic ash, mercury, and wind-blown dust.
In the earth's atmosphere, which contains 21% oxygen, natural and man-made trace gases are broken down by oxidation. This oxidation is a complex process and generally mediated by chains of free radical reactions. By far the most important oxidizing agent in the troposphere is the hydroxyl radical, OH. It is generated primarily through the photolysis of ozone, and reacts with most atmospheric trace gases, in many cases as the first and rate determining step in the reaction chains leading to their oxidation. Usually, these chains regenerate OH, thus maintaining OH at daytime concentrations of up to 107 cm-3. At these concentrations OH determines the destruction rate and tropospheric lifetime of most trace gases. In turn, all these gases influence the concentration of OH in the troposphere. There is thus the possibility of a regional, even global, impact on OH by man-made pollutants. The basic photochemical reaction system controlling OH is developed from simple examples of the various types of reactions that produce or destroy OH. The salient properties of the system are analyzed. The system is tested by comparing the OH concentrations predicted from the numerical simulation of the OH chemistry in clean surface air with those measured in these conditions.
Systematic observations of atmospheric carbon monoxide (CO) have been carried out in the western part of the Pacific Ocean since February 1990. The average CO concentration showed a latitudinal gradient, with higher values in the northern hemisphere than in the southern hemisphere. A clear seasonal CO cycle was found nearly at all sampling locations, showing maximum and minimum concentrations in spring and summer, respectively. In the 30°-35°N latitude zone, the average CO concentration was higher and the seasonal amplitude was larger compared with other latitudes. The CO concentration also showed a large interannual variability mainly in association with forest fires. In particular, the forest fires in Siberia in 1998 and Indonesia in 1997-1998 contributed to a remarkable increase in the regional CO concentration, followed by a recovery that took several months to a year. A three-dimensional atmospheric global chemical transport model (CHASER) was used to simulate the observed characteristics of the latitudinal distribution, seasonal cycle, and interannual variability relatively well. Tagged CO experiments with the model revealed that the contribution of CO emissions from various regions in the northern hemisphere to the CO concentrations at our sampling locations varied seasonally in association with Asian outflows and long-range transport from Europe and North America. In the southern hemisphere, biomass burnings significantly affected the regional seasonal CO cycle, in addition to the effect of CO oxidation with OH. It was also found that CHASER underestimates the average CO concentration in the northern hemisphere and its interannual variability.
This study explores the evolution and distribution of carbon monoxide (CO) using the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory three-dimensional global chemical transport model (GFDL GCTM). The work aims to gain an improved understanding of the global carbon monoxide budget, specifically focusing on the contribution of each of the four source terms to the seasonal variability of CO. The sum of all CO sources in the model is 2.5 Pg CO/yr (1Pg=103Tg), including fossil fuel use (300 Tg CO/yr), biomass burning (748 Tg CO/yr), oxidation of biogenic hydrocarbons (683 Tg CO/yr), and methane oxidation (760 Tg CO/yr). The main sink for CO is destruction by the hydroxyl radical, and we assume a hydroxyl distribution based on three-dimensional monthly varying fields given by Spivakovsky et al. [1990], but we increase this field by 15% uniformly to agree with a methyl chloroform lifetime of 4.8 years [Prinn et al., 1995]. Our simulation produces a carbon monoxide field that agrees well with available measurements from the NOAA/Climate Monitoring and Diagnostics Laboratory global cooperative flask sampling network and from the Jungfraujoch observing station of the Swiss Federal Laboratories for Materials Testing and Research (EMPA) (93% of seasonal-average data points agree within +/-25%) and flight data from measurement campaigns of the NASA Global Tropospheric Experiment (79% of regional-average data points agree within +/-25%). For all 34 ground-based measurement sites we have calculated the percentage contribution of each CO source term to the total model-simulated distribution and examined how these contributions vary seasonally due to transport, changes in OH concentration, and seasonality of emission sources. CO from all four sources contributes to the total magnitude of CO in all regions. Seasonality, however, is usually governed by the transport and destruction by OH of CO emitted by fossil fuel and/or biomass burning. The sensitivity to the hydroxyl field varies spatially, with a 30% increase in OH yielding decreases in CO ranging from 4-23%, with lower sensitivities near emission regions where advection acts as a strong local sink. The lifetime of CO varies from 10 days over summer continental regions to well over a year at the winter poles, where we define lifetime as the turnover time in the troposphere due to reaction with OH.
Carbon monoxide and methane are the two largest direct sinks of atmospheric OH. Globally the reaction between OH and CO provides the largest direct sink of OH, which is about twice as large as the reaction between OH and CH4. However, neither CO nor CH4 affects OH only by direct reactions. In fact, the direct reaction of OH with either CO or CH4 initiates a series of reactions and products, which also affect the atmospheric OH and can thus be considered as feedbacks. We developed a method to calculate the total contribution of either CO or CH4 to OH by tracing a series of reactions and products, which are initiated by the direct reaction of OH with either CO or CH4. With this tracing technique, we show that atmospheric methane, along with its feedbacks, may remove as much as more atmospheric OH than carbon monoxide, although CO is widely accepted as the largest sink of the atmospheric OH.
The photolysis of water vapor at 1849 Å has been investigated as a possible source of hydroxyl radicals for kinetic studies. At temperatures from 23 to 350 °C and pressures from 1.3 to 28 mm, H2 and H2O2 were the only detectable products. Experiments with added oxygen indicated that O2 may have been present as an intermediate at a very low steady-state concentration, although this is not certain. Possible mechanisms are discussed.At temperatures from 200 to 350 °C, carbon monoxide appeared to react quantitatively with the hydroxyl radicals produced in the photolysis of water by the reaction, Rates of this reaction relative to those of the reactions, and were estimated from the decrement in the yield of CO2 when H2 or D2 was added to the H2O–CO system, and the following Arrhenius parameters were obtained:At temperatures below 200 °C, hydroxyl radicals were not completely converted to CO2, as the yield of CO2 increased to a maximum, then decreased again, with increasing pressure of CO. The mechanism of this system is complex, but probably involves secondary reactions of HCO or COOH radicals.
ABSTRACTCO mixing ratios in air have been measured continuously at Cape Point (34°21prime;S; 18°29'E) between 1978 and 1981. The results show a seasonal variation of the CO mixing ratios with minimum values of 53 p.p.b.v. during January/February and maximum values of 87 p.p.b.v. during September/October. Short-term variations of CO mixing ratios in clean, undisturbed air were lacking, indicating that CO is well mixed in the Southern Hemisphere at latitudes of 20–40° S and that the observed seasonal variation is not due to temporal changes of local and regional source strengths. The seasonality of CO is explained by the seasonal variation of OH and by the north–south shift of the intertropical convergence zone. The agreement of CO mixing ratios measured at Cape Point and over the Southern Atlantic in 1971/1972 indicates that the southern hemispheric CO mixing ratios cannot have changed by more than 5–10% during the last decade.
The annual global emissions of CO are estimated to be about 2,600 ± 600 Tg, of which about 60% are from human activities including combustion of fossil fuels and oxidation of hydrocarbons including methane. The remaining 40% of the emissions are from natural processes, mostly from the oxidation of hydrocarbons but also from plants and the oceans. Almost all the CO emitted into the atmosphere each year is removed by reactions with OH radicals (85%), by soils (10%), and by diffusion into the stratosphere. There is a small imbalance between annual emissions and removal, causing an increase of about 1% per year. It is very likely that the imbalance is due to increasing emissions from anthropogenic activities. The average concentration of CO is about 90 ppbv, which amounts to about 400 Tg in the atmosphere, and the average lifetime is about 2 months. This view of the global cycle of CO is consistent with the present estimates of average OH concentrations and the budgets of other trace gases including methane and methylchloroform. There are large remaining uncertainties that may in the future upset the apparently cohesive present budget of CO. If the present view of the global cycle of CO is correct, then it is likely that, in time, increasing levels of CO will contribute to widespread changes in atmospheric chemistry.