AGW Observer

Observations of anthropogenic global warming

New research – atmospheric composition (September 19, 2016)

Posted by Ari Jokimäki on September 19, 2016

Some of the latest papers on atmospheric composition (mainly on greenhouse gases and aerosols) are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.


A global catalogue of large SO2 sources and emissions derived from the Ozone Monitoring Instrument (Fioletov et al. 2016)

Abstract: Sulfur dioxide (SO2) measurements from the Ozone Monitoring Instrument (OMI) satellite sensor processed with the new principal component analysis (PCA) algorithm were used to detect large point emission sources or clusters of sources. The total of 491 continuously emitting point sources releasing from about 30 kt yr−1 to more than 4000 kt yr−1 of SO2 per year have been identified and grouped by country and by primary source origin: volcanoes (76 sources); power plants (297); smelters (53); and sources related to the oil and gas industry (65). The sources were identified using different methods, including through OMI measurements themselves applied to a new emission detection algorithm, and their evolution during the 2005–2014 period was traced by estimating annual emissions from each source. For volcanic sources, the study focused on continuous degassing, and emissions from explosive eruptions were excluded. Emissions from degassing volcanic sources were measured, many for the first time, and collectively they account for about 30 % of total SO2 emissions estimated from OMI measurements, but that fraction has increased in recent years given that cumulative global emissions from power plants and smelters are declining while emissions from oil and gas industry remained nearly constant. Anthropogenic emissions from the USA declined by 80 % over the 2005–2014 period as did emissions from western and central Europe, whereas emissions from India nearly doubled, and emissions from other large SO2-emitting regions (South Africa, Russia, Mexico, and the Middle East) remained fairly constant. In total, OMI-based estimates account for about a half of total reported anthropogenic SO2 emissions; the remaining half is likely related to sources emitting less than 30 kt yr−1 and not detected by OMI.

Re-evaluating the 1940s CO2 plateau (Bastos et al. 2016)

Abstract: The high-resolution CO2 record from Law Dome ice core reveals that atmospheric CO2 concentration stalled during the 1940s (so-called CO2 plateau). Since the fossil-fuel emissions did not decrease during the period, this stalling implies the persistence of a strong sink, perhaps sustained for as long as a decade or more. Double-deconvolution analyses have attributed this sink to the ocean, conceivably as a response to the very strong El Niño event in 1940–1942. However, this explanation is questionable, as recent ocean CO2 data indicate that the range of variability in the ocean sink has been rather modest in recent decades, and El Niño events have generally led to higher growth rates of atmospheric CO2 due to the offsetting terrestrial response. Here, we use the most up-to-date information on the different terms of the carbon budget: fossil-fuel emissions, four estimates of land-use change (LUC) emissions, ocean uptake from two different reconstructions, and the terrestrial sink modelled by the TRENDY project to identify the most likely causes of the 1940s plateau. We find that they greatly overestimate atmospheric CO2 growth rate during the plateau period, as well as in the 1960s, in spite of giving a plausible explanation for most of the 20th century carbon budget, especially from 1970 onwards. The mismatch between reconstructions and observations during the CO2 plateau epoch of 1940–1950 ranges between 0.9 and 2.0 Pg C yr−1, depending on the LUC dataset considered. This mismatch may be explained by (i) decadal variability in the ocean carbon sink not accounted for in the reconstructions we used, (ii) a further terrestrial sink currently missing in the estimates by land-surface models, or (iii) LUC processes not included in the current datasets. Ocean carbon models from CMIP5 indicate that natural variability in the ocean carbon sink could explain an additional 0.5 Pg C yr−1 uptake, but it is unlikely to be higher. The impact of the 1940–1942 El Niño on the observed stabilization of atmospheric CO2 cannot be confirmed nor discarded, as TRENDY models do not reproduce the expected concurrent strong decrease in terrestrial uptake. Nevertheless, this would further increase the mismatch between observed and modelled CO2 growth rate during the CO2 plateau epoch. Tests performed using the OSCAR (v2.2) model indicate that changes in land use not correctly accounted for during the period (coinciding with drastic socioeconomic changes during the Second World War) could contribute to the additional sink required. Thus, the previously proposed ocean hypothesis for the 1940s plateau cannot be confirmed by independent data. Further efforts are required to reduce uncertainty in the different terms of the carbon budget during the first half of the 20th century and to better understand the long-term variability of the ocean and terrestrial CO2 sinks.

Trace gases in the atmosphere over Russian cities (Elansky et al. 2016)

Abstract: Multiyear observational data (obtained at the mobile railroad laboratory in the course of the 1995–2010 TROICA experiments) on the composition and state of the atmosphere were used to study the features of both spatial and temporal variations in the contents of trace gases in the surface air layer over Russian cities. The obtained characteristics of urban air noticeably differ from those obtained at stationary stations. The emission fluxes of NOx, CO, and CH4 and their integral emissions from large cities have been estimated on the basis of observational data obtained at the mobile laboratory. The values of these emission fluxes reflect the state of urban infrastructure. The integral urban emissions of CO depend on the city size and vary from 50 Gg yr−1 for Yaroslavl to 130 Gg yr−1 for Yekaterinburg. For most cities, they agree with the EDGAR v4.2 data within the limits of experimental error. The agreement is worse for the emissions of NOx. The EDGAR v4.2 data on the emissions of CH4 seem to be overestimated..

Potential sea salt aerosol sources from frost flowers in the pan-Arctic region (Xu et al. 2016)

Abstract: In order to better represent observed wintertime aerosol mass and number concentrations in the pan-Arctic (60°N-90°N) region, we implemented an observationally-based parameterization for estimating sea salt production from frost flowers in the Community Earth System Model (CESM, version 1.2.1). In this work, we evaluate the potential influence of this sea salt source on the pan-Arctic climate. Results show that frost flower salt emissions increase the modeled surface sea salt aerosol mass concentration by roughly 200% at Barrow and 100% at Alert and accumulation-mode number concentration by about a factor of 2 at Barrow and more than a factor of 10 at Alert in the winter months when new sea ice and frost flowers are present. The magnitude of sea salt aerosol mass and number concentrations at the surface in Barrow during winter simulated by the model configuration that includes this parameterization agrees better with observations by 48% and 12%, respectively, than the standard CESM simulation without a frost-flower salt particle source. At Alert, the simulation with this parameterization overestimates observed sea salt aerosol mass concentration by 150% during winter in contrast to the underestimation of 63% in the simulation without this frost flower source, while it produces particle number concentration about 14% closer to observation than the standard CESM simulation. However, because the CESM version used here underestimates transported sulfate in winter, the reference accumulation-mode number concentrations at Alert are also underestimated. Adding these frost flower salt particle emissions increases sea salt aerosol optical depth by 10% in the pan-Arctic region and results in a small cooling at the surface. The increase in salt aerosol mass concentrations of a factor of 8 provides nearly two times the cloud condensation nuclei concentration at supersaturation of 0.1%, as well as 10% increases in cloud droplet number and 40% increases in liquid water content near coastal regions adjacent to continents. These cloud changes reduce longwave cloud forcing at the top of the atmosphere by 3% and cause a small surface warming, increasing the downward longwave flux at the surface by 1.8 W m−2 in the pan-Arctic under the present-day climate. This regional average longwave warming due to the presence of clouds attributed to frost flower sea salts is roughly half of previous observed surface longwave fluxes and cloud-forcing estimates reported in Alaska, implying that the longwave enhancement due to frost flower salts may be comparable to those estimated for anthropogenic aerosol emissions. Since the potential frost flower area is parameterized as the maximum possible region on which frost flowers grow for the modeled atmospheric temperature and sea ice conditions and the model underestimates the number of accumulation-mode particles from mid-latitude anthropogenic sources transported in winter, the calculated aerosol indirect effect of frost flower sea salts in this work can be regarded as an upper bound.

Early detection of volcanic hazard by lidar measurement of carbon dioxide (Fiorani et al. 2016)

Abstract: Volcanic gases give information on magmatic processes. In particular, anomalous releases of carbon dioxide precede volcanic eruptions. Up to now, this gas has been measured in volcanic plumes with conventional measurements that imply the severe risks of local sampling and can last many hours. For these reasons and for the great advantages of laser sensing, the thorough development of volcanic lidars has been undertaken at ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development). In fact, lidar profiling allows one to scan remotely volcanic plumes in a fast and continuous way, and with high spatial and temporal resolution. A differential absorption lidar instrument will be presented in this paper: BILLI (BrIdge voLcanic LIdar). It is based on injection-seeded Nd:YAG laser, double-grating dye laser, difference frequency mixing and optical parametric amplifier. BILLI is funded by the ERC (European Research Council) project BRIDGE (BRIDging the gap between Gas Emissions and geophysical observations at active volcanos). It scanned the gas emitted by Pozzuoli Solfatara (Naples, Italy) and Stromboli Volcano (Sicily, Italy) during field campaigns carried out from October 13 to 17, 2014, and from June 24 to 29, 2015, respectively. Carbon dioxide concentration maps were retrieved remotely in few minutes in the crater areas. To our knowledge, it is the first time that carbon dioxide in a volcanic plume is retrieved by lidar. This result represents the first direct measurement of this kind ever performed on active volcanos and shows the high potential of laser remote sensing in early detection of volcanic hazard.

Other papers

Validation and update of OMI Total Column Water Vapor product (Wang et al. 2016)

Long-term visibility variation in Athens (1931–2013): a proxy for local and regional atmospheric aerosol loads (Founda et al. 2016)

Particulate air pollution from wildfires in the Western US under climate change (Liu et al. 2016)

Climate-driven ground-level ozone extreme in the fall over the Southeast United States (Zhang et al. 2016)

Radon as a tracer of atmospheric influences on traffic-related air pollution in a small inland city (Williams et al. 2016)

Bioaerosols in the Earth system: Climate, health, and ecosystem interactions (Fröhlich-Nowoisky et al. 2016)

The importance of non-fossil sources in carbonaceous aerosols in a megacity of central China during the 2013 winter haze episode: A source apportionment constrained by radiocarbon and organic tracers (Liu et al. 2016)

Estimating Minimum Detection Times for Satellite Remote Sensing of Trends in Mean and Extreme Precipitable Water Vapor (Roman et al. 2016)

A comprehensive estimate for loss of atmospheric carbon tetrachloride (CCl4) to the ocean (Butler et al. 2016)

Significant increase of summertime ozone at Mount Tai in Central Eastern China (Sun et al. 2016)

Snow Covered Soils Produce N2O that is Lost from Forested Catchments (Enanga et al. 2016)

Spatial and temporal variability of urban fluxes of methane, carbon monoxide and carbon dioxide above London, UK (Helfter et al. 2016)

Climatic variability of the column ozone over the Iranian plateau (Mousavi et al. 2016)

Long-term variation of stratospheric aerosols observed with lidars over Tsukuba, Japan from 1982 and Lauder, New Zealand from 1992 to 2015 (Sakai et al. 2016)

The natural oscillations in stratospheric ozone observed by the GROMOS microwave radiometer at the NDACC station Bern (Moreira et al. 2016)

A biogenic CO2 flux adjustment scheme for the mitigation of large-scale biases in global atmospheric CO2 analyses and forecasts (Agustí-Panareda et al. 2016)

Relationship of ground-level ozone with synoptic weather conditions in Chicago (Jing et al. 2016)

Global detection of absorbing aerosols over the ocean in the red and near infrared spectral region (Waquet et al. 2016)

Atmospheric benzene observations from oil and gas production in the Denver Julesburg basin in July and August 2014 (Halliday et al. 2016)

Carbon monoxide climatology derived from the trajectory mapping of global MOZAIC-IAGOS data (Osman et al. 2016)

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