The Adams Event, a geomagnetic-driven environmental crisis 42,000 years ago

Geological archives record multiple reversals of Earth’s magnetic poles, yet the potential impacts of these events remain unknown. The lack of any obvious association between the last major inversion, the Laschamps Excursion ~41 thousand years ago (ka), and polar ice paleoclimate records has underpinned the view that geomagnetic reversals do not have major environmental consequences. We find this is not the case. Importantly, the weakened geomagnetic field causes rapid production of atmospheric radiocarbon, and the lack of accurate calibration records has complicated dating of environmental and archaeological events in other parts of the world. Here we exploit the first detailed record of radiocarbon levels across the Laschamps Excursion using New Zealand swamp kauri (Agathis australis) trees to precisely align Pacific Basin environmental changes with polar paleoclimate records (via 10Be). Comprehensive radiocarbon-dated and glacial sequences are consistent with global chemistry climate modelling, and show synchronous climate changes across the mid to low latitudes that are concentrated during the geomagnetic field minima (42.2-41.5 ka) in the transitional phase that precedes the Laschamps Excursion. Critically, the revised timing reveals associations with a wide range of extinction events and major changes in the global archaeological record, which we hereby term the Adams Event. The climatic, environmental, and evolutionary impacts of past magnetic reversals now form a critical issue for future investigation

Effective density of aircraft engine PM revisited : effects of engine thrust, engine type, fuel, and sample conditioning

Aircraft gas turbine engines emit soot agglomerates with varying size, shape, and composition as a function of their operating condition. A useful parameter, which accounts for particle morphology, is effective density. Effective density is used to relate particle number and mass emissions in aviation PM emission models. However, measurement data of PM effective density from commercial aircraft turbine engines are very limited. Here, we report the size‐dependent effective density of PM sampled from commercial aircraft turbine engines in an engine test cell using a standardized sampling and measurement system. We used tandem DMA‐CPMA classification as in our previous study (Durdina et al. 2014). The novelty of this work is reduced scan time from over 10 minutes down to 1 minute per sample with the same hardware configuration, wider range of particle sizes, measurement of different engines, and a larger database with better data quality. The fast method allowed us to measure various engine types during their post‐overhaul test runs with short test points. We also performed effective density measurements during two dedicated test campaigns of the same engine. These campaigns investigated the effects of an alternative fuel blend on emissions and the evolution of the exhaust plume downstream of the engine exit plane. In the latter campaign, the effective density was measured with and without the treatment with a catalytic stripper approximately 25 m downstream of the engine exit plane. Figure 1 shows the compiled results obtained for all engines and fuels tested with exhaust samples taken at the engine exit plane and 25 m downstream with a catalytic stripper. The results confirm the thrust dependence of the effective density distributions reported previously. The most distinct differences are between the effective density distributions at idle thrust (Figure 1, a) and medium to high thrust (Figure 1, b). This trend was qualitatively the same for all engines tested. In contrast to our previous report, the effective densities at medium and high thrust did not follow the mass‐mobility relationship determined previously. The best fit of the data is an exponential function. The fit functions determined have potential applications in aircraft PM emissions modeling and measurement. The size‐dependent densities can be used to estimate PM mass concentration from particle size distributions measured using mobility particle sizers. The density functions can be used to improve particle loss correction models in sampling systems for aircraft engine emissions

Spatiotemporal heterogeneity of lung-deposited surface area in Zurich Switzerland : lung-deposited surface area as a new routine metric for ambient particle monitoring

Objective: To assess the spatiotemporal heterogeneity of lung-deposited particle surface area concentration (LDSA), while testing the long-term performance of a prototype of low-cost-low-maintenance LDSA sensors. One factor hampering epidemiological studies on fine to ultrafine particles (F-to-UFP) exposure is exposure error due to their high spatiotemporal heterogeneity, not reflected in particle mass. Though LDSA shows consistent associations between F-to-UFP exposure and health effects, LDSA data are limited. Methods: We measured LDSA in a network of ten sensors, including urban, suburban, and rural environments in Zurich, Switzerland. With traffic counts, traffic co-pollutant concentrations, and meteorological parameters, we assessed the drivers of the LDSA observations. Results: LDSA reflected the high spatiotemporal heterogeneity of F-to-UFP. With micrometeorological influences, local sources like road traffic, restaurants, air traffic, and residential combustion drove LDSA. The temporal pattern of LDSA reflected that of the local sources. Conclusion: LDSA may be a viable metric for inexpensively characterizing F-to-UFP exposure. The tested devices generated sound data and may significantly contribute to filling the LDSA exposure data gap, providing grounds for more statistically significant epidemiological studies and regulation of F-to-UFP

Overview of the impact of aviation on climate change and how this should be considered for air travel at ZHAW

Disclaimer: This research was conducted independently by a team of researchers on behalf of ZHAW sustainable, strategic program for Sustainable Development of the Zürich University of Applied Sciences (ZHAW), and financed as part of the implementation of the ZHAW Sustainability Strategy. https://www.zhaw.ch/sustainableThis overview paper describes the impact of aviation on the environment and its effects on climate change. It provides scientific and decision-making elements for considering the environmental impact of air travel, especially at universities. Travelling is an essential part of international cooperation and as air traffic constitutes the only means of travelling long distances within reasonable timeframe, corporate air travel remains indispensable. However, assessing the contribution of air travel to human induced global warming is characterized by large uncertainties, mostly due to non-CO2 emissions of airplanes and direct and indirect impact on the radiative balance. A recommendation for a uniform so-called “emission weighting factor” (EWF) of 3.0 is made for reporting, as it is believed to best represent the actual current impact of corporate air travel’s CO2 and non-CO2 emissions on the environment, with the suggestion that it be regularly reassessed

Coupling of Arctic ozone and stratospheric dynamics and its influence on surface climate : the role of CFC concentrations

Arctic stratospheric ozone has been shown to exert a statistically significant influence on Northern Hemispheric surface climate. This suggests that Arctic ozone is not only passively responding to dynamical variability in the stratosphere, but actively feeds back into the circulation through chemical and radiative processes. However, the extent and causality of the chemistry-dynamics coupling is still unknown. Since many state-of-the-art climate models lack a sufficient representation of ozone-dynamic feedbacks, a quantification of this coupling can be used to improve intra-seasonal weather and long-term climate forecasts. We assess the importance of the ozone-dynamics coupling by performing simulations with and without interactive chemistry in two Chemistry Climate Models. The chemistry-dynamics coupling was examined in two different sets of time-slice simulations: one using pre-industrial, and one using year-2000 boundary conditions. We focus on the impact of sudden stratospheric warmings (SSW) and strong vortex events on stratosphere-troposphere coupling, since these go along with strong ozone anomalies and therefore an intensified ozone feedback. We compare the runs with and without interactive chemistry. For pre-industrial conditions, simulations without interactive ozone show a more intense and longer lasting surface signature of SSWs compared to simulations with interactive chemistry. Conversely, for year-2000 conditions, the opposite effect is found: interactive chemistry amplifies the surface signature of SSWs. Following these results, atmospheric CFC concentrations, which differ greatly in the pre-industrial and year-2000 runs, determine the sign of the ozone-circulation feedback, and thus have a strong impact on chemistry-climate coupling. Implications for modeling of stratosphere-troposphere coupling and future projections are discussed

Intercomparison of two reference sampling and measurement systems for aircraft engine nonvolatile PM using a small-scale RQL combustor rig burning conventional and sustainable aviation fuels

Aircraft gas turbine engines directly emit non-volatile PM (nvPM) with electrical mobility diameters mostly 26.7 kN. However, further work is needed to characterize and reduce nvPM emissions measurement uncertainty and particle loss correction to provide better estimations of engine exit concentrations for airport emission inventories. As a part of the first campaign of the Horizon 2020 funded project RAPTOR, two nvPM reference sampling and measurement systems (Swiss and EU) were operated in parallel and sampled exhaust from a small-scale aero-engine rich-burn quick-quench lean-burn (RQL) combustor rig burning a range of conventional and sustainable aviation fuels at multiple rig operating conditions. Additional particle size measurements were performed using a TSI SMPS with a catalytic stripper in the Swiss system and a Cambustion DMS-500 fast spectrometer in the EU system. The preliminary results of this study show good agreement between the two systems for the nvPM number and mass emission indices (EIs) (Figure). At low nvPM mass, larger discrepancies were observed between the two systems because of the shedding of accumulated in the PM1 cyclones installed in each system. At specific rig conditions, the RQL combustor produced bi-modal particle size distributions with no volatile fraction which were similarly captured by both the SMPS and the DMS-500. It was found that the standardised particle loss correction methodology (only requiring measured nvPM mass and number) was inaccurate when particle size distributions were bi-modal and or low nvPM mass concentration when compared with particle loss correction estimated using measured particle size distributions. . This study will lead to a better understanding of the uncertainties of the regulatory nvPM data and supply data to improve the measurement methodology and more accurate prediction of aircraft engine nvPM emissions released into the environment

Nonvolatile particulate matter emissions of a business jet measured at ground level and estimated for cruising altitudes

This document is the Accepted Manuscript version of a Published Work that appeared in final form in Environmental Science & Technology, copyright © American Chemical Society after peer review and technical editing by the publisher.Business aviation is a relatively small but steadily growing and little investigated emission source. Regarding emissions, aircraft turbine engines rated at and below 26.7 kN thrust are certified only for visible smoke and are excluded from the nonvolatile particulate matter (nvPM) standard. Here, we report nvPM emission characteristics of a widely used small turbofan engine determined in a ground test of a Dassault Falcon 900EX business jet. These are the first reported nvPM emissions of a small in-production turbofan engine determined with a standardized measurement system used for emissions certification of large turbofan engines. The ground-level measurements together with a detailed engine performance model were used to predict emissions at cruising altitudes. The measured nvPM emission characteristics strongly depended on engine thrust. The geometric mean diameter increased from 17 nm at idle to 45 nm at take-off. The nvPM emission indices peaked at low thrust levels (7 and 40% take-off thrust in terms of nvPM number and mass, respectively). A comparison with a commercial airliner shows that a business jet may produce higher nvPM emissions from flight missions as well as from landing and take-off operations. This study will aid the development of emission inventories for small aircraft turbine engines and future emission standards

Surface ozone in the Southern Hemisphere : 20 years of data from a site with a unique setting in El Tololo, Chile

The knowledge of surface ozone mole fractions and their global distribution is of utmost importance due to the impact of ozone on human health and ecosystems and the central role of ozone in controlling the oxidation capacity of the troposphere. The availability of long-term ozone records is far better in the Northern than in the Southern Hemisphere, and recent analyses of the seven accessible records in the Southern Hemisphere have shown inconclusive trends. Since late 1995, surface ozone is measured in situ at "El Tololo", a high-altitude (2200ma.s.l.) and pristine station in Chile (30°S, 71°W). The dataset has been recently fully quality controlled and reprocessed. This study presents the observed ozone trends and annual cycles and identifies key processes driving these patterns. From 1995 to 2010, an overall positive trend of ∼ 0.7ppb decade−1 is found. Strongest trends per season are observed in March and April. Highest mole fractions are observed in late spring (October) and show a strong correlation with ozone transported from the stratosphere down into the troposphere, as simulated with a model. Over the 20 years of observations, the springtime ozone maximum has shifted to earlier times in the year, which, again, is strongly correlated with a temporal shift in the occurrence of the maximum of simulated stratospheric ozone transport at the site. We conclude that background ozone at El Tololo is mainly driven by stratospheric intrusions rather than photochemical production from anthropogenic and biogenic precursors. The major footprint of the sampled air masses is located over the Pacific Ocean. Therefore, due to the negligible influence of local processes, the ozone record also allows studying the influence of El Niño and La Niña episodes on background ozone levels in South America. In agreement with previous studies, we find that, during La Niña conditions, ozone mole fractions reach higher levels than during El Niño conditions

Springtime arctic ozone depletion forces northern hemisphere climate anomalies

Large-scale chemical depletion of ozone due to anthropogenic emissions occurs over Antarctica as well as, to a lesser degree, the Arctic. Surface climate predictability in the Northern Hemisphere might be improved due to a previously proposed, albeit uncertain, link to springtime ozone depletion in the Arctic. Here we use observations and targeted chemistry–climate experiments from two models to isolate the surface impacts of ozone depletion from complex downward dynamical influences. We find that springtime stratospheric ozone depletion is consistently followed by surface temperature and precipitation anomalies with signs consistent with a positive Arctic Oscillation, namely, warm and dry conditions over southern Europe and Eurasia and moistening over northern Europe. Notably, we show that these anomalies, affecting large portions of the Northern Hemisphere, are driven substantially by the loss of stratospheric ozone. This is due to ozone depletion leading to a reduction in short-wave radiation absorption, when in turn causing persistent negative temperature anomalies in the lower stratosphere and a delayed break-up of the polar vortex. These results indicate that the inclusion of interactive ozone chemistry in atmospheric models can considerably improve the predictability of Northern Hemisphere surface climate on seasonal timescales

Multidecadal variations of the effects of the Quasi-Biennial Oscillation on the climate system

Effects of the Quasi-Biennial Oscillation (QBO) on tropospheric climate are not always strong or they appear only intermittently. Studying them requires long time series of both the QBO and climate variables, which has restricted previous studies to the past 30–50 years. Here we use the benefits of an existing QBO reconstruction back to 1908. We first investigate additional, newly digitized historical observations of stratospheric winds to test the reconstruction. Then we use the QBO time series to analyse atmospheric data sets (reconstructions and reanalyses) as well as the results of coupled ocean–atmosphere-chemistry climate model simulations that were forced with the reconstructed QBO. We investigate effects related to (1) tropical-extratropical interaction in the stratosphere, wave-mean flow interaction and subsequent downward propagation, and (2) interaction between deep tropical convection and stratospheric flow. We generally find weak connections, though some are statistically significant over the 100-year period and consistent with model results. Apparent multidecadal variations in the connection between the QBO and the investigated climate responses are consistent with a small effect in the presence of large variability, with one exception: the imprint on the northern polar vortex, which is seen in recent reanalysis data, is not found in the period 1908-1957. Conversely, an imprint in Berlin surface air temperature is only found in 1908-1957 but not in the recent period. Likewise, in the model simulations both links tend to appear alternatingly, suggesting a more systematic modulation due to a shift in the circulation, for example. Over the Pacific warm pool, we find increased convection during easterly QBO, mainly in boreal winter in observation-based data as well as in the model simulations, with large variability. No QBO effects were found in the Indian monsoon strength or Atlantic hurricane frequency