Reconstructing urban CO₂ emissions utilising the radiocarbon composition of tree rings from the Wellington Region, New Zealand

<p>This study demonstrates the utility of tree ring radiocarbon analysis to quantify a temporal record of recently-added fossil fuel-derived carbon dioxide (CO₂ff) in the urban atmosphere, to retrospectively measure emissions and potentially validate local emissions inventories. Currently, there is no internationally recognised method to test emissions inventories against direct atmospheric estimations of CO₂ff. With the increasing interest in emissions control legislation, independent and objective research to validate emissions reported by governments and industries is needed. As CO₂ff emissions are completely depleted in radiocarbon (¹⁴C), an observed decrease in the ¹⁴C content of the atmosphere is mostly due to additions of CO₂ff. As trees incorporate CO₂ from the local atmosphere into annual growth rings, it was hypothesised that an urban located tree would reflect emission rates of its local surroundings. Measurements of the ¹⁴C content of cellulose were made from the annual tree rings of a Kauri tree (Agathis australis), located in the downtown area of the Wellington suburb of Lower Hutt (KNG52). This record was compared with tree rings from two Kauri at a nearby coastal site (NIK19 and NIK23) and the long-term clean air ¹⁴CO₂ record from Baring Head. The clean air Kauri trees, NIK19 and NIK23, demonstrated excellent agreement with the Baring Head atmospheric record, indicating that the trees were accurately sampling the atmosphere. The KNG52 tree, demonstrated good agreement with the clean air record in the early part of the record (with some variability), however, exhibited significantly lower Δ¹⁴CO₂ values from the 1980s onward. Calculation of the influence of the terrestrial biosphere on the ¹⁴CO₂ record showed very little impact, determining that the variability seen was due to local additions of CO₂ff. Historic CO₂ff emissions were calculated using the Δ¹⁴CO₂ measurements from the KNG52 ¹⁴CO₂ record for the period 1972 – 2012. Biosphere correction calculations showed that the biosphere was the dominant influence on the record in the early part of the record (1972 – 1980), with fossil fuel emissions dominating the record from 1980s onward. The observations were compared qualitatively with meteorological data and urban development in the area to assess variability in CO₂ff. A minor trend towards lower wind speeds associated with higher levels of CO₂ff was identified, indicating that local meteorology may be responsible for 10% change seen in the record. The influence of local development demonstrated some possible relation but a correlation was not significant. The KNG52 CO₂ff record was compared with national-level reported liquid (road traffic) emissions from the Carbon Dioxide Information Analysis Centre (CDIAC). The observed KNG52 CO₂ff in the tree ring record appeared to increase in tandem with road traffic emissions.</p>

Reconstructing urban CO₂ emissions utilising the radiocarbon composition of tree rings from the Wellington Region, New Zealand

<p>This study demonstrates the utility of tree ring radiocarbon analysis to quantify a temporal record of recently-added fossil fuel-derived carbon dioxide (CO₂ff) in the urban atmosphere, to retrospectively measure emissions and potentially validate local emissions inventories. Currently, there is no internationally recognised method to test emissions inventories against direct atmospheric estimations of CO₂ff. With the increasing interest in emissions control legislation, independent and objective research to validate emissions reported by governments and industries is needed. As CO₂ff emissions are completely depleted in radiocarbon (¹⁴C), an observed decrease in the ¹⁴C content of the atmosphere is mostly due to additions of CO₂ff. As trees incorporate CO₂ from the local atmosphere into annual growth rings, it was hypothesised that an urban located tree would reflect emission rates of its local surroundings. Measurements of the ¹⁴C content of cellulose were made from the annual tree rings of a Kauri tree (Agathis australis), located in the downtown area of the Wellington suburb of Lower Hutt (KNG52). This record was compared with tree rings from two Kauri at a nearby coastal site (NIK19 and NIK23) and the long-term clean air ¹⁴CO₂ record from Baring Head. The clean air Kauri trees, NIK19 and NIK23, demonstrated excellent agreement with the Baring Head atmospheric record, indicating that the trees were accurately sampling the atmosphere. The KNG52 tree, demonstrated good agreement with the clean air record in the early part of the record (with some variability), however, exhibited significantly lower Δ¹⁴CO₂ values from the 1980s onward. Calculation of the influence of the terrestrial biosphere on the ¹⁴CO₂ record showed very little impact, determining that the variability seen was due to local additions of CO₂ff. Historic CO₂ff emissions were calculated using the Δ¹⁴CO₂ measurements from the KNG52 ¹⁴CO₂ record for the period 1972 – 2012. Biosphere correction calculations showed that the biosphere was the dominant influence on the record in the early part of the record (1972 – 1980), with fossil fuel emissions dominating the record from 1980s onward. The observations were compared qualitatively with meteorological data and urban development in the area to assess variability in CO₂ff. A minor trend towards lower wind speeds associated with higher levels of CO₂ff was identified, indicating that local meteorology may be responsible for 10% change seen in the record. The influence of local development demonstrated some possible relation but a correlation was not significant. The KNG52 CO₂ff record was compared with national-level reported liquid (road traffic) emissions from the Carbon Dioxide Information Analysis Centre (CDIAC). The observed KNG52 CO₂ff in the tree ring record appeared to increase in tandem with road traffic emissions.</p>

Estimating CO₂ Emissions for 108,000 European Cities

City-level CO2 emissions inventories are foundational for supporting the EU’s decarbonization goals. Inventories are essential for priority setting and for estimating impacts from the decarbonization transition. Here we present a new CO2 emissions inventory for 116,572 municipal and local government units in Europe. The inventory spatially disaggregates the national reported emissions, using 9 spatialization methods to distribute the 167 line items detailed in the UN's Common Reporting Framework. The novel contribution of this model is that results are provided per administrative jurisdiction at multiple administrative levels using a new spatialization approach. All data from this study is available along with an interactive map of results at https://openghgmap.net

Constraining emission estimates of carbon monoxide using a perturbed emissions ensemble with observations: a focus on Beijing

The reliability of air quality simulations has a strong dependence on the input emissions inventories, which are associated with various sources of uncertainties, particularly in regions undergoing rapid emission changes where inventories can be ‘out of date’ almost as soon as they are compiled. This work provides a new methodology for updating emissions inventories by source sector using air quality ensemble simulations and observations from a dense monitoring network. It is adopted to determine the short-term trends in carbon monoxide (CO) emissions, an important pollutant and precursor to tropospheric ozone, in a study area centred around Beijing following the implementation of clean air policies. We sample the uncertainties associated with using an a priori emissions inventory for the year 2013 in air quality simulations of 2016, using an atmospheric dispersion model combined with a perturbed emissions ensemble (PEE), which is constructed based on expert-elicited uncertainty ranges for individual source sectors in the inventory. By comparing the simulation outputs with observational constraints, we are able to constrain the emissions of key source sectors relative to those in the a priori emissions inventory. From 2013 to 2016, we find a 44–88% reduction in the transport sector emissions (0.92–4.4×105 Mg in 2016) and a minimum 61% decrease in residential sector emissions (<3.5×105 Mg in 2016) within the study area. We also provide evidence that the night-time fraction of traffic sources in 2016 was higher than that in the 2013 emissions inventory. This study shows the applicability of PEEs and high-resolution observations in providing timely updates of emission estimates by source sector.

Emissions inventory for road transport in India in 2020: Framework and post facto policy impact assessment

India's growing population and economic development lead to an increase in transport emissions. Quantification of emissions at frequent intervals is required to assess the emission levels and impact of control policies implemented. Implemented policies affect the fleet configuration over time. Therefore, in the present paper, an age-wise emission analysis framework was developed for the road transport sector with updated fleet characteristics corresponding to the vehicles' age. The results show that fuel consumption is estimated to be 92 (87–95) Mt, and total CO2, CO, PM, and NOx vehicle emissions are estimated to be 274 (265–292) Tg, 4463 (3253–6676) Gg, 164 (119–250) Gg, and 2378 (2191–3045) Gg, respectively for the reference year 2020. The study contributes by developing an inventory for the fleet of 2020 used as a benchmark to compare past emissions inventories, evaluate control policies, estimate state-wise vehicle emissions inventories, and identify significant emitters in the fleet. Sensitivity analysis indicates the considerable variation in total emissions resulting from different age-mix of vehicles. Among the investigated policies, advancement in emission norms followed by fuel efficiency improvement in vehicles led to a substantial reduction in gaseous pollutants. Based on the inventory results, suitable policies are suggested for India's future fleet, and the need for country-level fleet characteristics data is recommended.

Prediction of aircraft engine emissions using ADS-B flight data

ABSTRACT Real-time flight data from the Automatic Dependent Surveillance–Broadcast (ADS-B) has been integrated, through a data interface, with a flight performance computer program to predict aviation emissions at altitude. The ADS-B, along with data from Mode-S, are then used to ‘fly’ selected long-range aircraft models (Airbus A380-841, A330-343 and A350-900) and one turboprop (ATR72). Over 2,500 flight trajectories have been processed to demonstrate the integration between databases and software systems. Emissions are calculated for altitudes greater than 3,000 feet (609m) and exclude landing and take-off cycles. This proof of concept fills a gap in the aviation emissions inventories, since it uses real-time flights and produces estimates at a very granular level. It can be used to analyse emissions of gases such as carbon dioxide ( $\mathrm{CO}_2$ ), carbon monoxide (CO), nitrogen oxides ( $\mathrm{NO}_x$ ) and water vapour on a specific route (city pair), for a specific aircraft, for an entire fleet, or on a seasonal basis. It is shown how $\mathrm{NO}_x$ and water vapour emissions concentrate around tropospheric altitudes only for long-range flights, and that the cruise range is the biggest discriminator in the absolute value of these and other exhaust emissions.

Low-NO atmospheric oxidation pathways in a polluted megacity

The impact of emissions of volatile organic compounds (VOCs) to the atmosphere on the production of secondary pollutants, such as ozone and secondary organic aerosol (SOA), is mediated by the concentration of nitric oxide (NO). Polluted urban atmospheres are typically considered to be “high-NO” environments, while remote regions such as rainforests, with minimal anthropogenic influences, are considered to be “low NO”. However, our observations from central Beijing show that this simplistic separation of regimes is flawed. Despite being in one of the largest megacities in the world, we observe formation of gas- and aerosol-phase oxidation products usually associated with low-NO “rainforest-like” atmospheric oxidation pathways during the afternoon, caused by extreme suppression of NO concentrations at this time. Box model calculations suggest that during the morning high-NO chemistry predominates (95 %) but in the afternoon low-NO chemistry plays a greater role (30 %). Current emissions inventories are applied in the GEOS-Chem model which shows that such models, when run at the regional scale, fail to accurately predict such an extreme diurnal cycle in the NO concentration. With increasing global emphasis on reducing air pollution, it is crucial for the modelling tools used to develop urban air quality policy to be able to accurately represent such extreme diurnal variations in NO to accurately predict the formation of pollutants such as SOA and ozone.