The influence of African air pollution on regional and global tropospheric chemistry

International audienceWe investigate the relative importance of African biomass burning, biogenic volatile organic compounds (VOC), lightning and anthropogenic emissions to the tropospheric ozone budget over Africa and globally using a coupled global chemistry climate model. Our model studies indicate that the photochemical surface ozone concentration may rise by up to 50 ppbv in the burning region during the biomass burning seasons. Biogenic VOCs contribute between 5?20 ppbv to the near surface ozone concentration over the tropical African region. The impact of lightning on surface ozone is negligible, while anthropogenic emissions contribute a maximum of 10 ppbv to the surface ozone over Nigeria, South-Africa and Egypt. The annual average of the surface and column ozone over Africa shows that biomass burning is the single most important emission source affecting the African region, while biogenic emissions have the highest contribution during the rainy seasons. The contributions of African emissions to global tropospheric ozone burden (TOB) are about 9 Tg, 13 Tg, 8 Tg and 4 Tg for African biomass burning, biogenic VOC, lightning and anthropogenic emissions respectively. These correspond to 2.4%, 3.4%, 2.1% and 1% of the global tropospheric ozone budget respectively. Over Africa itself, the contribution of each of these emission types is only 2.4 Tg, 2.2 Tg, 1.4 Tg and 0.8 Tg respectively. Outside the continent, African biogenic VOC emissions yield the highest contribution to the TOB. Our model calculations suggest that about 70% of the tropospheric ozone produced from emissions in Africa is found outside the continent, thus exerting a noticeable influence on a large part of the tropical troposphere. Latin America experiences the highest impact of African emissions, followed by southeast and south-central Asia, Oceania, and the Middle East for all the emission categories; while Canada, the United States, Russia, Mongolia, China and Europe experience the least impact of African emissions

The vertical distribution of ozone instantaneous radiative forcing from satellite and chemistry climate models

We evaluate the instantaneous radiative forcing (IRF) of tropospheric ozone predicted by four state-of-the-art global chemistry climate models (AM2-Chem, CAM-Chem, ECHAM5-MOZ, and GISS-PUCCINI) against ozone distribution observed from the NASA Tropospheric Emission Spectrometer (TES) during August 2006. The IRF is computed through the application of an observationally constrained instantaneous radiative forcing kernels (IRFK) to the difference between TES and model-predicted ozone. The IRFK represent the sensitivity of outgoing longwave radiation to the vertical and spatial distribution of ozone under all-sky condition. Through this technique, we find total tropospheric IRF biases from -0.4 to + 0.7 W/m(2) over large regions within the tropics and midlatitudes, due to ozone differences over the region in the lower and middle troposphere, enhanced by persistent bias in the upper troposphere-lower stratospheric region. The zonal mean biases also range from -30 to + 50 mW/m(2) for the models. However, the ensemble mean total tropospheric IRF bias is less than 0.2 W/m(2) within the entire troposphere

Global Multi-Year O3-CO Correlation Patterns from Models and TES Satellite Observations

The correlation between measured tropospheric ozone (O3) and carbon monoxide (CO) has been used extensively in tropospheric chemistry studies to explore the photochemical characteristics of different regions and to evaluate the ability of models to capture these characteristics. Here, we present the first study that uses multi-year, global, vertically resolved, simultaneous and collocated O3 and CO satellite (Tropospheric Emission Spectrometer) measurements, to determine this correlation in the middle/lower free troposphere for two different seasons, and to evaluate two chemistry-climate models. We find results that are fairly robust across different years, altitudes and timescales considered, which indicates that the correlation maps presented here could be used in future model evaluations. The highest positive correlations (around 0.8) are found in the northern Pacific during summer, which is a common feature in the observations and the G-PUCCINI model. We make quantitative comparisons between the models using a single-figure metric (C), which we define as the correlation coefficient between the modeled and the observed O3-CO correlations for different regions of the globe. On a global scale, the G-PUCCINI model shows a good performance in the summer (C =0.71) and a satisfactory performance in the winter (C = 0.52). It captures midlatitude features very well, especially in the summer, whereas the performance in regions like South America or Central Africa is weaker. The UKCA model (C = 0.46/0.15 for July-August/December-January on a global scale) performs better in certain regions, such as the tropics in winter, and it captures some of the broad characteristics of summer extratropical correlations, but it systematically underestimates the O3-CO correlations over much of the globe. It is noteworthy that the correlations look very different in the two models, even though the ozone distributions are similar. This demonstrates that this technique provides a powerful global constraint for understanding modeled tropospheric chemical processes. We investigated the sources of the correlations by performing a series of sensitivity experiments. In these, the sign of the correlation is, in most cases, insensitive to removing different individual emissions, but its magnitude changes downwind of emission regions when applying such perturbations. Interestingly, we find that the O3-CO correlation does not solely reflect the strength of O3 photochemical production, as often assumed by earlier studies, but is more complicated and may reflect a mixture of different processes such as transport

COMPARING GEOSCIENCES-RELATED ENGAGEMENT GENERATED DURING AND AFTER THE USE OF MULTIPLE PEDAGOGICAL APPROACHES: ANIMATED VIDEOS, YOUTUBE, INTERACTIVE EDUCATIONAL GAMES, GROUP DISCUSSION AND POWERPOINT PRESENTATIONS

The COVID-19 pandemic has increased educators’ reliance on online learning tools such as Blackboard Collaborate Ultra and Zoom meetings to deliver geoscience-related lessons in real-time. Assessments were conducted using introduction to geology, environmental geology, and oceanography - part of the City University of New York\u27s (CUNY) newly implemented pathways curriculum. These general education courses belong to scientific world and life and physical sciences category and are intended for seamless transfer between CUNY campuses. Students, however, have the option to disengage from participation. Students are able to disable microphones and cameras, as well as rely entirely on text-chat if they choose. Students also have the option to simply log-on and not be physically present at all. If a practitioner does not advocate for forced participation via assigning a heavy weight of the course grade to participation, then the burden of bolstering engagement is almost entirely on the practitioner. This study attempts to review different pedagogical approaches and create a rubric to measure engagement during and after the delivery of the course contents. These approaches include short animated videos, long, medium, and short YouTube videos, interactive educational games, group discussions and debates, PowerPoint presentations, etc. The goal is to find approaches that deliver an effective learning, but still encourage organic class participation. Initial findings are as follows: short animated videos had the most total engagement with highly positively correlated with engagement during and after; long YouTube videos generated the most engagement during and after; single-player interactive educational games tied for highest total engagement and encouraged discussion during the game as well as after; short PowerPoint presentations with salient information did much better than longer presentations; and group discussions (when engaged upon) generated a moderate amount of total engagement. Trends included: length correlated positively with discussion during delivery, but negatively with discussion after delivery; intensity played no part in discussion during an activity, but correlated positively with discussion afterwards. In general, high intensity material of any kind, has been deemed the best

Satellite constraint on the tropospheric ozone radiative effect

Tropospheric ozone directly affects the radiative balance of the Earth through interaction with shortwave and longwave radiation. Here we use measurements of tropospheric ozone from the Tropospheric Emission Spectrometer satellite instrument, together with chemical transport and radiative transfer models, to produce a first estimate of the stratospherically adjusted annual radiative effect (RE) of tropospheric ozone. We show that differences between modeled and observed ozone concentrations have little impact on the RE, indicating that our present-day tropospheric ozone RE estimate of 1.17 ± 0.03 W m−2 is robust. The RE normalized by column ozone decreased between the preindustrial and the present-day. Using a simulation with historical biomass burning and no anthropogenic emissions, we calculate a radiative forcing of 0.32 W m−2 for tropospheric ozone, within the current best estimate range. We propose a radiative kernel approach as an efficient and accurate tool for calculating ozone REs in simulations with similar ozone abundances

Displacement and Resettlement: Understanding the Role of Climate Change in Contemporary Migration

How do we understand displacement and resettlement in the context of climate change? This chapter outlines challenges and debates in the literature connecting climate change to the growing global flow of people. We begin with an outline of the literature on environmental migration, specifically the definitions, measurements, and forms of environmental migration. The discussion then moves to challenges in the reception of migrants, treating the current scholarship on migrant resettlement. We detail a selection of cases in which the environment plays a role in the displacement of a population, including sea level rise in Pacific Island States, cyclonic storms in Bangladesh, and desertification in West Africa, as well as the role of deforestation in South America’s Southern Cone as a driver of both climate change and migration. We outline examples of each, highlighting the complex set of losses and damages incurred by populations in each case

Sensitivity of tracer transport to model resolution, forcing data and tracer lifetime in the general circulation model ECHAM5

International audienceThe transport of tracers in the general circulation model ECHAM5 is analysed using 9 independent idealized tracers with constant lifetimes released in different altitude regions of the atmosphere. The source regions were split into the tropics, Northern and Southern Hemisphere. The dependency of tracer transport on model resolution is tested in the resolutions T21L19, T42L19, T42L31, T63L31 and T106L31, by employing tracers with a globally uniform lifetime of 5 months. Each of the experiments uses prescribed sea surface temperatures and sea ice fields of the 1990s. The influence of meteorology and tracer lifetimes were tested by performing additional experiments in the T63L31 resolution, by nudging ECHAM5 towards the European Centre for Medium Range Weather Forecast 40 years re-analysis data (ERA40), and by using tracer lifetimes of 0.5 and 50 months, respectively. The transport of tracers is faster in the finer resolution models and is mostly dependent on the number of vertical levels. We found a decrease in the inter-hemispheric transport of tracers with source region at the surface or the tropopause in the coarse resolution models due to increasing recirculation within the source region and vertical mixing. However, a coarse model resolution leads to enhanced inter-hemispheric transport in the stratosphere. The use of ERA40 data only slightly affects the inter-hemispheric transport of surface and tropopause tracers, whereas it increases the inter-hemispheric and vertical transport in the stratosphere by up to 100% and by a factor of 2.5, respectively. The inter-hemispheric transport time was deduced from simulations with tracers of infinite lifetime and source regions at the surface in the Northern and Southern Hemisphere. Again, the transport was found to be faster for models with higher vertical resolution. We find inter-hemispheric transport times of about 7 to 9 months which are lower than the values reported in the literature, based for example on 85Kr observations

The influence of African air pollution on regional and global tropospheric ozone

We investigate the influence of African biomass burning, biogenic, lightning and anthropogenic emissions on the tropospheric ozone over Africa and globally using a coupled global chemistry climate model. Our model studies indicate that surface ozone concentration may rise by up to 50 ppbv in the burning region during the biomass burning seasons. Biogenic emissions yield between 5–30 ppbv increase in the near surface ozone concentration over tropical Africa. The impact of lightning on surface ozone is negligible, while anthropogenic emissions yield a maximum of 7 ppbv increase in the annual-mean surface ozone concentration over Nigeria, South Africa and Egypt. Our results show that biogenic emissions are the most important African emission source affecting total tropospheric ozone. The influence of each of the African emissions on the global tropospheric ozone burden (TOB) of 384 Tg yields about 9.5 Tg, 19.6 Tg, 9.0 Tg and 4.7 Tg for biomass burning, biogenic, lightning and anthropogenic emissions emitted in Africa respectively. The impact of each of these emission categories on African TOB of 33 Tg is 2.5 Tg, 4.1 Tg, 1.75 Tg and 0.89 Tg respectively, which together represents about 28% of the total TOB calculated over Africa. Our model calculations also suggest that more than 70% of the tropospheric ozone produced by each of the African emissions is found outside the continent, thus exerting a noticeable influence on a large part of the tropical troposphere. Apart from the Atlantic and Indian Ocean, Latin America experiences the largest impact of African emissions, followed by Oceania, the Middle East, Southeast and south-central Asia, northern North America (i.e. the United States and Canada), Europe and north-central Asia, for all the emission categories

The influence of African air pollution on regional and global tropospheric ozone

We investigate the influence of African biomass burning, biogenic, lightning and anthropogenic emissions on the tropospheric ozone over Africa and globally using a coupled global chemistry climate model. Our model studies indicate that surface ozone concentration may rise by up to 50 ppbv in the burning region during the biomass burning seasons. Biogenic emissions yield between 5-30 ppbv increase in the near surface ozone concentration over tropical Africa. The impact of lightning on surface ozone is negligible, while anthropogenic emissions yield a maximum of 7 ppbv increase in the annual-mean surface ozone concentration over Nigeria, South Africa and Egypt. Our results show that biogenic emissions are the most important African emission source affecting total tropospheric ozone. The influence of each of the African emissions on the global tropospheric ozone burden (TOB) of 384 Tg yields about 9.5 Tg, 19.6 Tg, 9.0 Tg and 4.7 Tg for biomass burning, biogenic, lightning and anthropogenic emissions emitted in Africa respectively. The impact of each of these emission categories on African TOB of 33 Tg is 2.5 Tg, 4.1 Tg, 1.75 Tg and 0.89 Tg respectively, which together represents about 28% of the total TOB calculated over Africa. Our model calculations also suggest that more than 70% of the tropospheric ozone produced by each of the African emissions is found outside the continent, thus exerting a noticeable influence on a large part of the tropical troposphere. Apart from the Atlantic and Indian Ocean, Latin America experiences the largest impact of African emissions, followed by Oceania, the Middle East, Southeast and south-central Asia, northern North America (i.e. the United States and Canada), Europe and north-central Asia, for all the emission categories