Changes In Regional Emissions Research Articles

Trends in sulfur dioxide over the Indian subcontinent during 2003–2019

Sulfur dioxide (SO 2 ) and its oxidation products profoundly impact the air quality and climate. In recent decades, contrasting SO 2 trends have been observed over different regions of the globe due to urbanization, energy generation and control measures. In this study, we have investigated the SO 2 trends over the rapidly developing Indian subcontinent using model reanalysis, satellite data, and emission inventories during 2003–2019 period. Copernicus Atmosphere Monitoring Service (CAMS) reanalysis shows rapid SO 2 growth up to 0.4 ppbv yr −1 during 2003–2009, particularly significant over the Indo-Gangetic Plain (IGP) and eastern India. However, the growth becomes slower after 2010 and is followed by a stabilization or slight reduction. The CAMS results agree with the satellite-based observations, however, the model underestimates enhancements over eastern India. The analysis of inventory datasets also suggests slower growths in SO 2 emissions and coal-fired electricity generation in recent years. Besides the changes in regional emissions, the enhancements in water vapor and OH radical coinciding with SO 2 stabilization indicate strengthening of the sink processes. Model simulation (Modern-Era Retrospective analysis for Research and Applications version 2―MERRA-2) with constant emissions shows reduction in SO 2 which confirms the stronger chemical losses. Overall, the SO 2 trends over the Indian subcontinent are found to be a manifestation of the combined effects of the regional emission change and chemistry. Our findings highlight the need for studies to assess the impacts of changing SO 2 trends in India on the regional and global climate. • Investigation of SO 2 trends and the driving processes over a global hotspot. • Comprehensive analysis of model results, satellite data, and emission inventories. • Rapid SO 2 growth over India until around 2010, followed by slower trends. • Role of stronger chemical sink besides effect of changing emissions. • Need of studies to assess the climatic implications of presented SO 2 trends.

Continental-scale contributions to the global CFC-11 emission increase between 2012 and 2017

Abstract. The detection of increasing global CFC-11 emissions after 2012 alerted society to a possible violation of the Montreal Protocol on Substances that Deplete the Ozone Layer (MP). This alert resulted in parties to the MP taking urgent actions. As a result, atmospheric measurements made in 2019 suggest a sharp decline in global CFC-11 emissions. Despite the success in the detection and mitigation of part of this problem, regions fully responsible for the recent global emission changes in CFC-11 have not yet been identified. Roughly two thirds (60 ± 40 %) of the emission increase between 2008–2012 and 2014–2017 and two thirds (60 ± 30 %) of the decline between 2014–2017 and 2019 were explained by regional emission changes in eastern mainland China. Here, we used atmospheric CFC-11 measurements made from two global aircraft surveys – the HIAPER (High-performance Instrumented Airborne Platform for Environmental Research) Pole-to-Pole Observations (HIPPO) in November 2009–September 2011 and the Atmospheric Tomography Mission (ATom) in August 2016–May 2018, in combination with the global CFC-11 measurements made by the US National Oceanic and Atmospheric Administration during these two periods – to derive global and regional emission changes in CFC-11. Our results suggest Asia accounted for the largest fractions of global CFC-11 emissions in both periods: 43 (37–52) % during November 2009–September 2011 and 57 (49–62) % during August 2016–May 2018. Asia was also primarily responsible for the emission increase between these two periods, accounting for 86 (59–115) % of the global CFC-11 emission rise between the two periods. Besides eastern mainland China, temperate western Asia and tropical Asia also contributed significantly to global CFC-11 emissions during both periods and likely to the global CFC-11 emission increase. The atmospheric observations further provide strong constraints on CFC-11 emissions from North America and Europe, suggesting that each of them accounted for 10 %–15 % of global CFC-11 emissions during the HIPPO period and smaller fractions in the ATom period. For South America, Africa, and Australia, the derived regional emissions had larger dependence on the prior assumptions of emissions and emission changes due to a lower sensitivity of the observations considered here to emissions from these regions. However, significant increases in CFC-11 emissions from southern hemispheric lands were not likely due to the observed increase of north-to-south interhemispheric gradients in atmospheric CFC-11 mole fractions from 2012–2017.

Assessment of the impact of “dual-carbon” goal on future changes in air pollution and climate in China

<p indent=0mm>Carbon neutrality refers to achieving net-zero carbon dioxide emissions. Reducing CO₂ emissions is one of the major ways to achieve carbon neutrality and control air temperature rise. So far, numerous countries have pledged their goals of achieving carbon neutrality. In September 2020, China proposed a national dual-carbon goal and the associated timeline to achieve peak carbon and carbon neutrality. Therefore, how the proposal will lead to future changes in air quality and climate in China is of great interest. In the context of the dual-carbon goal, a series of emission reduction policies for different types of industries will be implemented to achieve CO₂ reductions. As a result, emissions of other pollutants will be reduced as well. Furthermore, future global climate change is also one of the main concerns. Most previous studies have focused on one single impacting factor without consideration of the dual-carbon goal. While carbon neutrality is an inevitable global trend, studies of its implication on air quality and climate change in China are still rare. Considering both regional emissions and global climate change will help predict future climate. Taking the dual-carbon goal into account will help adjust current emission reduction policies. In this study, we simulate the impacts of both regional emissions and global climate change in the future on China’s air quality and climate in the future under the dual-carbon goal scenario using a regional climate-ecology coupled model RegCM-Chem-YIBs, based on the Representative Concentration Pathway (RCP4.5) climate scenario and China’s 2030 emission data based on dynamics projection model (DPEC). Numerical simulations for present climate and present emissions, present climate and future emissions, and future climate and future emissions were performed. The comparison between the three sets of simulations provides how future regional emission reduction and global climate change will affect air pollution and climate in 2030. The study shows that, compared with 2015, the concentrations of fine particulate matter (PM_2.5), ozone (O₃), and carbon dioxide (CO₂) in China will decrease by approximately 36.8, <sc>19.8 μg m⁻³</sc> and <sc>1.9 ppm</sc> in 2030, respectively, under the combined effect of future regional emissions and global climate change. The temperature in the southern part of China will increase significantly, with an increase between 0.5 and <sc>1.5 K.</sc> Precipitation and clouds decrease by <sc>1−2 mm d⁻¹</sc> and <sc>3%−6%,</sc> respectively. The temperature in the northern part decreases slightly, generally below <sc>1 K.</sc> Precipitation and clouds increase by approximately 2 mm d⁻¹ and 6%, respectively. Overall, regional emission changes have a larger impact on PM_2.5, O₃ and CO₂ concentrations, which are the main influencing factors for future air quality changes, while global climate change has a greater impact on temperature, clouds and precipitation. Emission reduction policies under the dual-carbon target will significantly reduce air pollution, but may exacerbate warming at the surface because these policies will inevitably diminish the cooling effect of particulate matter. The mitigation of climate change will require GHG (greenhouse gas) and air pollution synergistic emission reduction policies and worldwide cooperation.

Climate change penalty and benefit on surface ozone: a global perspective based on CMIP6 earth system models

This work presents an analysis of the effect of climate change on surface ozone discussing the related penalties and benefits around the globe from the global modelling perspective based on simulations with five CMIP6 (Coupled Model Intercomparison Project Phase 6) Earth System Models. As part of AerChemMIP (Aerosol Chemistry Model Intercomparison Project) all models conducted simulation experiments considering future climate (ssp370SST) and present-day climate (ssp370pdSST) under the same future emissions trajectory (SSP3-7.0). A multi-model global average climate change benefit on surface ozone of −0.96 ± 0.07 ppbv °C−1 is calculated which is mainly linked to the dominating role of enhanced ozone destruction with higher water vapour abundances under a warmer climate. Over regions remote from pollution sources, there is a robust decline in mean surface ozone concentration on an annual basis as well as for boreal winter and summer varying spatially from −0.2 to −2 ppbv °C−1, with strongest decline over tropical oceanic regions. The implication is that over regions remote from pollution sources (except over the Arctic) there is a consistent climate change benefit for baseline ozone due to global warming. However, ozone increases over regions close to anthropogenic pollution sources or close to enhanced natural biogenic volatile organic compounds emission sources with a rate ranging regionally from 0.2 to 2 ppbv C−1, implying a regional surface ozone penalty due to global warming. Overall, the future climate change enhances the efficiency of precursor emissions to generate surface ozone in polluted regions and thus the magnitude of this effect depends on the regional emission changes considered in this study within the SSP3_7.0 scenario. The comparison of the climate change impact effect on surface ozone versus the combined effect of climate and emission changes indicates the dominant role of precursor emission changes in projecting surface ozone concentrations under future climate change scenarios.

Black carbon deposited in Hariqin Glacier of the Central Tibetan Plateau record changes in the emission from Eurasia.

Black carbon (BC), by the combustion of fossil fuels and biomass, has profound effects on climate change and glacier retreat in industrial eras. In the present study, we report refractory BC (rBC) in an ice core spanning 1850-2014, retrieved from the Hariqin Glacier of the Tanggula Mountains in the central Tibetan Plateau, measured using a single particle soot photometer (SP2). The rBC concentration shows a three-fold increase since the 1950s. The mean rBC concentration was 0.71±0.52ngmL-1 during 1850s-1940s and 2.11±1.60ngmL-1 during 1950s-2010s. The substantial increase in rBC since the 1950s is consistent with rBC ice core records from the Tibetan Plateau and Eastern Europe. According to the predominant atmospheric circulation patterns over the glacier and timing of changes in regional emissions, the post-1950 amplification of rBC concentration in the central Tibetan Plateau most likely reflects increases in emissions in Eastern Europe, former USSR, the Middle East, and South Asia. Despite the low-level background rBC concentrations in the ice cores from the Tibetan Plateau, the present study highlights a remarkable increase in anthropogenic BC emissions in recent decades and the consequent influence on glaciers in the Tibetan Plateau.

Emission influences on air pollutant concentrations in New York State: I. ozone

Abstract Relationships between regional air pollutant emissions and ambient concentration trends in New York State are studied. Large (∼50–85%) reductions in anthropogenic emissions occurred in the northeastern U.S. and eastern Canada between 1995 and 2015. Spatially and temporally aggregated ambient concentrations of O3 precursors declined steadily along with emission reductions: multi-site mean annual nitrogen dioxide (NO2), carbon monoxide (CO), and toluene concentrations tracked state and regional emissions of oxides of nitrogen (NOx, NO + NO2), CO, and volatile organic compounds (VOC), respectively (r2 = 0.97, 0.88, and 0.73), showing linear responses of average O3 precursor concentrations to both state and regional emission reductions. O3 exhibited complex spatial and temporal variations, indicating that O3 was influenced not only by the steady decline of regional emissions but also by subregional emission changes, chemical and physical processes, and day-specific variations in emissions and weather. The statewide multi-site mean annual 4th-highest daily 8-h O3 peak declined at the rate of 0.86 ± 0.14 ppbv y−1 (1.1% y−1). Influences on peak daily 8-h O3 were studied using a long-term data record from a research site at Pinnacle State Park (PSP), located near Addison, New York. A generalized additive model (GAM) was applied to separate the influences of local and regional emission changes, weather, and other factors. GAM results indicate that the reduction of summer O3 peak values and the overall trends in O3 at PSP were due to changes in ambient pollutant levels, rather than to trends in temperature or other meteorological factors. Whereas PSP summer O3 was NOx-sensitive, O3 was often VOC-sensitive during winter and spring days. The frequency of VOC-sensitive days decreased between 2001 – 2005 and 2012–2016, consistent with an expectation of increasing NOx sensitivity as ambient NOx concentrations decline.

Concentrations and radiative forcing of anthropogenic aerosols from 1750 to 2014 simulated with the Oslo CTM3 and CEDS emission inventory

Abstract. We document the ability of the new-generation Oslo chemistry-transport model, Oslo CTM3, to accurately simulate present-day aerosol distributions. The model is then used with the new Community Emission Data System (CEDS) historical emission inventory to provide updated time series of anthropogenic aerosol concentrations and consequent direct radiative forcing (RFari) from 1750 to 2014. Overall, Oslo CTM3 performs well compared with measurements of surface concentrations and remotely sensed aerosol optical depth. Concentrations are underestimated in Asia, but the higher emissions in CEDS than previous inventories result in improvements compared to observations. The treatment of black carbon (BC) scavenging in Oslo CTM3 gives better agreement with observed vertical BC profiles relative to the predecessor Oslo CTM2. However, Arctic wintertime BC concentrations remain underestimated, and a range of sensitivity tests indicate that better physical understanding of processes associated with atmospheric BC processing is required to simultaneously reproduce both the observed features. Uncertainties in model input data, resolution, and scavenging affect the distribution of all aerosols species, especially at high latitudes and altitudes. However, we find no evidence of consistently better model performance across all observables and regions in the sensitivity tests than in the baseline configuration. Using CEDS, we estimate a net RFari in 2014 relative to 1750 of −0.17 W m−2, significantly weaker than the IPCC AR5 2011–1750 estimate. Differences are attributable to several factors, including stronger absorption by organic aerosol, updated parameterization of BC absorption, and reduced sulfate cooling. The trend towards a weaker RFari over recent years is more pronounced than in the IPCC AR5, illustrating the importance of capturing recent regional emission changes.

Wet deposition of sulfur and nitrogen in Jiuzhaigou National Nature Reserve, Sichuan, China during 2015-2016: Possible effects from regional emission reduction and local tourist activities.

In order to understand the impacts of regional emission changes and local tourism on sulfur and nitrogen wet deposition in Jiuzhaigou National Nature Reserve of southwestern China, wet deposition was monitored at a background site (Rize) and a tourist-affected site (PE: park entrance) in the reserve during 2015-2016. The observation data were compared between Rize and PE and between 2010-2011 and 2015-2016 monitoring campaigns. Also, the observation data were used in the Positive Matrix Factorization (PMF) model to identify the major sources of sulfur and nitrogen wet deposition. The results show that although local tourism emissions had considerable contributions to NH4+, NO2-, NO3-, and SO42- concentrations in wet deposition (p<0.05), most of the annual Volume Weighted Mean (VWM) concentrations of these four ions were likely from emissions outside Jiuzhaigou. Annual wet deposition fluxes of the four ions were also affected more by precipitation and regional emissions than by local emissions. Although annual precipitation was higher at Rize (818mm) during 2015-2016 than at another background site near Long Lake (LL: 752mm) during 2010-2011, the annual concentrations and fluxes of SO42- and NO3- wet deposition decreased by 77% and 74% for SO42- and by 12% and 19% for NO3-, respectively, most likely due to regional emission reductions. Similar large reductions in SO42- and NO3- concentrations have been also found in some other sites in southwestern China. In contrast, the annual concentration and flux of NH4+ wet deposition at Rize during 2015-2016 were 1.4 and 1.2 times of that measured at LL during 2010-2011, respectively. The results of source apportionment analysis and tour bus emission estimates suggest that elevated NH4+ wet deposition was possibly related to NH3 emissions from local tour buses, but additional studies on NH3 emissions from tour buses in the reserve are needed to confirm this.

Incorporating regional growth into forecasts of greenhouse gas emissions from project-level residential and commercial development

Abstract To better understand the greenhouse gas (GHG) implications of land use planning decisions, regional planning organizations have developed tools to forecast the emissions from project-level residential and commercial development. This paper reviews the state of GHG emissions forecasting methods for project-level development. We argue that when forecasting changes in regional emissions it is important to make explicit what is assumed about a project′s effect on the population of residents and businesses in the region. We present five regional growth assumptions capturing the range of ways that project-level development might influence (i) construction and occupancy of similar developments elsewhere in a region and (ii) relocation of the initial activities that occur on-site before the project is built. We show that current forecasting tools inconsistently address the latter when they are interpreted as forecasted changes in regional emissions. Using a case study in Yolo County, California we demonstrate that forecasted changes in regional emissions are greatly affected by the regional growth assumption. In the absence of information about which regional growth assumption is accurate, we provide guidelines for selection of a conservative regional growth assumption.

Climate-driven changes in air quality over Europe by the end of the 21st century, with special reference to Portugal

Abstract Climate change alone may deeply impact air quality levels in the atmosphere because the changes in the meteorological conditions will induce changes on the transport, dispersion and transformation of air pollutants. The aim of this work was to evaluate the impact of climate change on the air quality over Europe and Portugal, using a reference year (year 1990) and a IPCC SRES A2 year (year 2100). The Hadley Centre global atmospheric circulation model (HadAM3P) was used to provide results for these two climatic scenarios, which were then used as synoptic forcing for the MM5-CHIMERE air quality modelling system. In order to assess the contribution of future climate change on O3 and PM concentrations, no changes in regional emissions were assumed and only climate change forcing was considered. The modelling results suggest that the O3 monthly mean levels in the atmosphere may increase almost 50 μg m−3 across Europe in July under the IPCC SRES A2 scenario. In Portugal, this increase may reach 20 μg m−3. The changes of PM10 monthly average values over Europe will depend on the region. The increase in PM10 concentrations during specific months could be explained by the average reduction of the boundary layer height and wind speed.

Increasing synoptic scale variability in atmospheric CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; at Hateruma Island associated with increasing East-Asian emissions

Abstract. In-situ observations of atmospheric CO2 and CH4 at Hateruma Island (24.05° N, 123.80° E, 47 m a.s.l), Japan shows large synoptic scale variations during a 6-month period from November to April, when the sampled air is predominantly of continental origin due to the Asian winter monsoon. Synoptic scale variations are extracted from the daily averaged values for the years between 1996 and 2007, along with the annual standard deviations (σCO2 and σCH4 for CO2 and CH4, respectively) for the relevant 6-month period. During this 6-month period the absolute mixing ratios of CO2 and CH4 at Hateruma are also elevated compared to those at two sites in the central North Pacific Ocean. The temporal change in σCO2 shows a systematic increase over the 12-year period, with elevated excursions in 1998 and 2003; there is no clear increase in σCH4. We also find that the σCO2/σCH4 ratio increases gradually from 1996 to 2002 and rapidly after 2002 without any extreme deviations that characterised σCO2. The σCO2/σCH4 ratio correlates closely with the recent rapid increase in fossil carbon emissions from China, as indicated in the Carbon Dioxide Information Analysis Center (CDIAC) database. This methodology can be applied to multiple chemical tracers of sufficient lifetime, for tracking overall changes in regional emissions.

Monitoring and modelling trace-gas changes following the 2001 outbreak of Foot and Mouth Disease to reduce the uncertainties in agricultural emissions abatement

Abstract The outbreak of Foot and Mouth Disease (FMD) in the UK during 2001 provided a case study to test the link between changing NH3 emissions and NH3 concentrations in air. Previous studies have shown an “ammonia gap” between modelled and observed changes, which might be due to low effectiveness of abatement measures, interactions with changing atmospheric chemistry, ammonia compensation points and inter-annual variability. This study therefore aimed to support policy development by assessing whether possible future reductions in ammonia emissions would achieve the desired outcome of reduced air concentrations. Two networks for monthly measurement of atmospheric NH3 were established, centred on Cumbria and Devon, these being two of the areas worst-affected by FMD. Measurements of CH4 were made in parallel to represent an inert tracer emitted by ruminants, for which near-source atmospheric concentration enhancements would be unaffected by atmospheric reactions. Measurements commenced immediately after the end of the FMD outbreak in February 2002, followed the period of restocking and ceased in January 2004. The spatio-temporal patterns of monthly NH3 and CH4 emissions and concentrations at 5 km resolution were modelled for the UK, providing a reference to interpret the measurements. Overall trends in monthly modelled and measured NH3 concentrations were not significant, these being masked by seasonal and inter-year variability. However, comparison of sampling locations in FMD-affected areas with those in areas not directly affected by FMD showed relative depletions in modelled NH3 in FMD-affected areas of ∼25% for Cumbria and ∼8% for Devon. These reductions were matched by measured depletions in NH3 in FMD-affected areas of ∼35% for Cumbria and ∼20% for Devon, relative to unaffected areas. The modelled recovery in NH3 emissions was slower than for CH4, due to the lag-time associated with NH3 emissions from manure storage and spreading. For CH4 concentrations, modelled reductions in affected areas relative to unaffected areas were 17% for Cumbria and 5% for Devon, but significant relative changes in the measured CH4 concentrations were not detectable. The results show that sites need to be more representative and/or sampling precision needs to be improved to detect such short-term CH4 signals. Conversely, this study has demonstrated that atmospheric NH3 concentrations responded to changes in regional emissions, but that such short-term changes are only detectable by a multi-site assessment of contrasting areas.

Net radiative forcing due to changes in regional emissions of tropospheric ozone precursors

The global distribution of tropospheric ozone (O3) depends on the emission of precursors, chemistry, and transport. For small perturbations to emissions, the global radiative forcing resulting from changes in O3 can be expressed as a sum of forcings from emission changes in different regions. Tropospheric O3 is considered in present climate policies only through the inclusion of indirect effect of CH4 on radiative forcing through its impact on O3 concentrations. The short‐lived O3 precursors (NOx, CO, and NMHCs) are not directly included in the Kyoto Protocol or any similar climate mitigation agreement. In this study, we quantify the global radiative forcing resulting from a marginal reduction (10%) in anthropogenic emissions of NOx alone from nine geographic regions and a combined marginal reduction in NOx, CO, and NMHCs emissions from three regions. We simulate, using the global chemistry transport model MOZART‐2, the change in the distribution of global O3 resulting from these emission reductions. In addition to the short‐term reduction in O3, these emission reductions also increase CH4 concentrations (by decreasing OH); this increase in CH4 in turn counteracts part of the initial reduction in O3 concentrations. We calculate the global radiative forcing resulting from the regional emission reductions, accounting for changes in both O3 and CH4. Our results show that changes in O3 production and resulting distribution depend strongly on the geographical location of the reduction in precursor emissions. We find that the global O3 distribution and radiative forcing are most sensitive to changes in precursor emissions from tropical regions and least sensitive to changes from midlatitude and high‐latitude regions. Changes in CH4 and O3 concentrations resulting from NOx emission reductions alone produce offsetting changes in radiative forcing, leaving a small positive residual forcing (warming) for all regions. In contrast, for combined reductions of anthropogenic emissions of NOx, CO, and NMHCs, changes in O3 and CH4 concentrations result in a net negative radiative forcing (cooling). Thus we conclude that simultaneous reductions of CO, NMHCs, and NOx lead to a net reduction in radiative forcing due to resulting changes in tropospheric O3 and CH4 while reductions in NOx emissions alone do not.

The role of nitrogen oxides in oxidant production as predicted by the Regional Acid Deposition Model (RADM)

Regional oxidant distributions produced under various atmospheric conditions and emission scenarios are investigated using the Regional Acid Deposition Model (RADM). RADM is a complex, evolving three-dimensional Eulerian model that describes the chemistry, transport and deposition of tropospheric trace species including SO2, sulfate, NO x and volatile organic compounds as well as O3, other major oxidants and acids. The model calculates the short-term temporal evolution of atmospheric trace gas concentrations and their deposition on the regional scale. This study is focused on oxidant production in the eastern United States and southeastern Canada. The influence of atmospheric conditions is explored by comparing three characteristic winter, summer and spring/fall cases. Base-case 1985 emissions of SO x , NO x , volatile organic compounds (VOCs), NH3 and CO are specified using the comprehensive pollutant emissions inventory developed as part of the National Acid Precipitation Assessment Program (NAPAP). The perturbed case, which represents projected anthropogenic emission changes for 2010, indicates changes in daily total 80 km grid average NO x emissions ranging from increases of 75% to decreases of 45% and VOC emission changes ranging from increases of 65% to decreases of 20%. The largest NO x emission changes occur in the northeast, and the largest VOC changes occur in the Gulf Coast area. Ground level grid average midday O3 concentrations for the 1985 emission cases are highest (on the order of 70 to 100 ppb) in the New York City and Houston metropolitan areas for the summer and spring cases; the summer case also indicates relatively high grid average O3 concentrations of greater than 80 ppb in the southeast. Winter case values are much lower than summer O3 values throughout the region, with highs of 40 to 50 ppb occurring in the southeast and the Great Lakes area. Changes in NO x and other emissions under the complex 2010 emissions scenario for the summer case result in maximum O3 concentration reductions of 10% in the Houston area and increases in O3 of a few percent in some rural areas of the southeast. This study underscores the need for more comprehensive assessment of the complex relationships among regional emission changes, oxidant production and atmospheric conditions.