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The relationship between economic growth and environmental pollution continues to attract significant research interest for researchers, practitioners, and policymakers all over the globe. Theoretically, the environmental benefit of economic growth should be greater than its negative externality with higher level of development. However, from the African perspective, countries with higher economic performances often face several environmental challenges, which raises the doubt whether economic growth helps or constrains environmental quality improvement. Under the environmental Kuznets curve (EKC) hypothesis, this study re-examined the effect of economic growth on CO2 emissions conditional on the dynamics of urbanization, renewable energy, and good governance across 47 African countries using panel data from 1996 to 2019. We employ panel cointegration tests to establish whether there is a long-run equilibrium relationship among our variables. We also apply pooled mean group ARDL (PMG-ARDL) techniques and the Dumitrescu-Hurlin causality test to determine the long- and short-run effects of economic growth, urbanization, renewable energy consumption, and good governance on CO2 emissions. The results from the PMG estimator validate the EKC hypothesis since a 1% surge in GDP per capita increases emissions by 0.61% in the long run, while a 1% increase in its square decreases emissions by 0.03%. In the short-run, economic growth does not exercise any significant effect on emissions. Furthermore, results indicate a significantly negative and positive long-run effect of renewable energy and governance, respectively. Finally, our causality test shows bidirectional relationship between CO2 emissions and all the explanatory variables. Henceforth, we provided policy implications based on the study's results., (© 2023. The Author(s).)

Environmental degradation continues to attract interest from academics, policymakers, and other stakeholders. However, empirical studies have been limited in the choice of human well-being indicators. Therefore, this study extends the literature by broadening the nexus between human well-being and environmental degradation in 29 African countries from 1970 to 2019. Preliminary tests adaptable to effects of cross-sectional dependency and heterogeneity in panel dataset were adopted, alongside the cross-sectional auto-regressive distributed lag model. Findings from the study showed that the adopted human well-being indicators such as globalisation, life expectancy, and human capital development were environmentally enhancing both in the short and long terms. In contrast, income growth was environmentally degrading in the short and long terms. At the same time, urbanisation was only environmentally detrimental in the long term with no significant short-term effect. Natural resource rent which served as a control variable was environmentally degrading both in the short and long terms. Consequently, this study confirms the synergy approach between the environment and human well-being and the trade-off hypothesis in African countries. Thus, African countries' general resource management policy significantly determines the impact their path to human well-being enhancement has on the environment., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Motivated by the growing levelof informal economy in emerging economies, this study examines the role of the informal economy in the ecological footprint for the case of Africa. The relationship between official economy, trade openness, governance indicator, financial development, and urbanization on ecological footprint is also investigated. Applying data from 1991 to 2017, this empiric utilizes panel estimation procedures to account for cross-sectional dependence and slope heterogeneity in panel data. The results establish the presence of cross-sectional dependence and slope heterogeneity across countries in Africa. Furthermore, long-run cointegration is confirmed using Westerlund panel cointegration. Driscoll-Kraay's (DK) estimation technique shows that informal economy, official economy, governance, financial development, and urbanization have significant positive impacts on ecological footprint, implying that they contribute to environmental degradation. However, trade openness has a negative and significant effect on ecological footprint, improving environmental quality. Similarly, the Dumitrescu-Hurlin (DH) Granger causality test reveals a two-way relationship between the informal economy and ecological footprint and formal economy and ecological footprint. However, the study finds a one-way connection from urbanization and financial development to ecological footprint and from ecological footprint to governance indicators and trade openness. The implications of the findings for a sustainable environment are discussed., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

This study examines the spatial impact of FDI on ecological footprint of 31 African countries. In achieving this, the study uses the Driscoll-Kraay (1998) random effect model, fixed-effect instrumental variable regression, and the spatial Durbin model. There are three main important findings from this empirical study. First, FDI has a nonlinear impact on ecological footprint in Africa. At the initial stage, FDI reduces ecological footprint up to a threshold of $404.75-$669.96 million, before the impact increases ecological degradation. This result is robust to the instrumental regression model. Second, the results further reveal a significant spatial spillover of FDI on ecological footprint in Africa. Third, the empirical results provide evidence of both direct and spillover effects of environmental degradation determinant in Africa. This denotes that environmental quality of a particular country influences the environmental quality of other neighbouring countries. While it is important to attract significant amount of foreign investment to Africa, this study recommends that African governments need to improve their environmental regulations and laws to achieve transfer of energy-saving technology from foreign investors., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

To better understand Africa's banks and the environment, this study investigates the impact of financial performance on environmental performance in Africa. We examined financial performance, environmental performance, and some control indicators dated from 2000 to 2016 by applying panel quantile regression and panel vector autoregressive techniques. Our results indicate that (i) in North African countries, carbon emission had a significant negative impact on financial performance on the 25th quantile and (ii) in the South, carbon emission had a statistically positive impact on financial performance on the 25th and 50th quantiles with the marginal effect increases from the lower quantile to the highest quantile. Also, bank deposits statistically negatively impacted financial performance on the 25th and 50th quantiles for both North and South economies. The dynamic panel quantile results show dissimilar effects at different quantiles. Also, the panel vector autoregressive results show that in North Africa carbon emission had a positive impact. Our results validate the stability test of the panel vector autoregressive model. The granger causality results in the North show a bilateral causal link between carbon emission and bank credit, carbon emission, and bank deposit. Since sustainability has become one of our era's most thorny issues, this paper provides extensive policy directives to assist African nations in boosting a greener future., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The economic and environmental structures of countries are greatly impacted by domestic and foreign conflicts. To promote sustainable development, it is crucial to understand the spatial impact of these conflicts on the ecological footprint of a region. With a focus on Middle Eastern and African countries, this paper investigates the impact of such conflicts on their environments, taking into consideration the unique spatial features of their ecological footprints. Using a spatial econometric model, the study assesses the contributions of ecological footprint determinants, particularly internal and external conflict indicators, across 46 Middle Eastern and African countries from 2001 to 2019. The results indicate that internal conflict can lead to increased pressure on natural resources and ecological systems in neighboring countries, while energy use and economic growth impose a significant ecological burden both domestically and abroad. While urbanization and resource rents were found to reduce the ecological footprint, trade openness was found to be nonsignificant. Conflicts such as war, foreign pressure, civil war, and civil disorder were found to have a significant negative impact on the environment, suggesting that reducing these conflicts would improve environmental circumstances. The findings highlight the need for conflict resolution measures to achieve a sustainable environment in the Middle Eastern and African regions and have implications for other countries facing similar issues., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The major aim of this study was to investigate the impact of renewable energy consumption and agricultural economic growth on agricultural carbon emissions in Africa for the period 1990-2019. This paper employed panel fully modified ordinary least square (PFMOLS) and dynamic ordinary least square (PDOLS) estimation techniques. The empirical results showed that agriculture growth promote agricultural carbon emissions. More precisely, the results revealed a strong positive and statistical significant impact on agricultural carbon emissions in Africa. On the other hand, the results on quadratic show a negative causal association between agriculture growth and agricultural carbon emissions in Africa. Interestingly, renewable energy consumption was found to have a negative impact on agricultural carbon emissions. On Granger causality, the result shows that there is a unidirectional causality between agriculture growth and agricultural carbon emissions. Based on these findings, we recommend that countries should promote and encourage the use of renewable energy to curb agricultural carbon emissions. There is a need to adopt agricultural practices that have the potential to limit carbon emissions., (© 2023. The Author(s).)

The ambition of the Belt and Road Initiative (BRI) became an integral part of carbon emission abatement. The BRI impact on African participating countries' battle against carbon emissions intensity is a contentious subject. Urbanization and industrialization are the main sources of CO 2 emissions in Africa and the driving force in the BRI. Using data on variables from 2010 to 2019 in 54 African countries, applying Difference-in-differences model (DID) and Propensity Score Matching-Difference-in-differences regression (PSM-DID), and robustness tests to investigate if the BRI's participation tends to reduce the carbon emissions intensity of African participating countries. This study finds that African countries' participation in the BRI minimizes the intensity of carbon emissions in those countries. Further analysis shows that low carbon development of BRI countries is more significant in countries that joined the BRI than those that did not join it. In addition, our results show that improving economic transformation such as the innovation in technology and industries' structures can boost the CO 2 emission reduction technologies. These findings suggest that developing BRI collaboration with China will benefit the environment and African BRI participating countries' ability to achieve sustainable development. Our results further support the BRI's effect and recommend policy implications and methods for those countries' CO 2 emission prevention and control actions., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Industrialization is considered imperative for growth but energy transitions are paramount for inclusive and green growth especially for a region with low financial sector development to spur investment in renewable energy. This study thus unbundles the interrelation among renewable energy production, financial development, and real per capita growth in 32 selected African countries from the period of 1996 to 2018. These countries are categorized on the basis of oil-rich and non-oil-rich as well as income levels. The study employs Pooled Mean Group, Augmented Mean Group, and Dynamic OLS, and key findings are established. The findings reveal a significantly positive renewable energy-economic growth relationship in all the different groups. Financial development is also found to improve economic performance in all categories except in non-oil-rich African countries. These findings empirically support the need for cleaner energy in the production process to spur inclusive and green growth amidst current global concern for climate change and global warning. This study thus recommends the restructuring of the energy pricing system, provision of long-term finance, adoption of risk mitigation instruments, and improved institutional framework for private participation in renewable energy infrastructural development for growth sustainability in Africa., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Using an aerosol–climate coupled model, this paper has investigated the changes in distributions of anthropogenic and natural particles due to 4 × CO2-induced global warming, under the low emission scenario of Representative Concentration Pathway 4.5 (RCP4.5). Special attention is paid to the seasonal variations of aerosol size modes. With rising CO2 levels, surface warming, and changes in atmospheric circulations and hydrologic cycles are found during both summer (JJA) and winter (DJF). For anthropogenic particles, changes in fine anthropogenic particulate matter (PM2.5, particles with diameters smaller than 2.5 μm) decrease over high-latitude regions and increase over the tropics in both DJF and JJA. Global mean column concentrations of PM2.5 decrease by approximately 0.19 mg m−2, and concentrations of coarse anthropogenic particles (CPM, particles with diameters larger than 2.5 μm) increase by 0.005 mg m−2 in JJA. Changes in anthropogenic particles in DJF are similar to those in JJA, but the magnitudes of maximum regional changes are much smaller than those in JJA. The coarse anthropogenic particles (CPM, particles with diameters larger than 2.5 μm) increase over northern Africa and the Arabian Peninsula during JJA, whereas changes in anthropogenic CPM during DJF are minimal. During both JJA and DJF, changes in anthropogenic CPM are about two orders of magnitude smaller than those of anthropogenic PM2.5. Enhanced wet deposition by large-scale precipitation under rising CO2-induced surface warming is the critical factor affecting changes in anthropogenic particles. For natural particles, the distribution of change in the natural PM2.5 burden is similar to that of natural CPM, but much larger than natural CPM during each season. Both natural PM2.5 and CPM burdens increase over northern Africa and the Arabian Peninsula during JJA, but decrease over most of the continental regions during DJF. Changes in surface wind speed, divergence/convergence of surface wind, and precipitation are primary reasons for the variation of natural particles. [ABSTRACT FROM AUTHOR]

In order to explore whether China-Africa exchange will influence on the African environment. This paper selects four paths of China-Africa exchanges and explores the impact of each path on the African environment under the influence of different factors. We found that construction income and Africa's exports to China will increase Africa's carbon emissions. Foreign direct investment and China's exports to Africa will lead to a reduction in carbon emissions in Africa. The resource moderation will reduce the significance of the environmental impact of each path on Africa. Based on the above conclusions, several suggestions are made on the policies and actual operations in the path of China-Africa exchanges., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Li et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Renewable energy and institutions have emerged among other variables touted to address climate change problems. However, empirical results have been conflicting. With a relatively poorer state of institutional quality and a lower level of renewable energy development amidst rising carbon dioxide (CO 2 ) emissions in Africa, the study assesses: a) the direct effect of renewable energy and institutional quality on CO 2 emissions in Africa; and b) the moderation role of institutional quality on the effect of renewable energy on CO 2 emissions in Africa. The study relies on panel data covering 2002-2021 for 32 African countries. The Fully-Modified OLS regression method is employed to analyze the data based on the environmental Kuznets curve (EKC) hypothesis and Stochastic Impacts by Regression on Population, Affluence, & Technology (STIRPAT) model. The results show that urbanization and trade openness increase CO 2 emissions. Although income has a positive effect on carbon emissions, the square term has a negative confirming the EKC hypothesis. Renewable energy also reduces CO 2 emissions. Institutional quality variables of control of corruption, rule of law, regulatory quality, political stability and absence of violence, voice and accountability, government effectiveness and institutional index created from the above indicators reduce CO 2 emissions. In addition, except government effectiveness, the remaining indicators of institutional quality negatively moderate the effect of renewable energy on CO 2 emissions. The results among other things imply that intensifying the development and usage of renewable energy would help address the rising carbon dioxide emissions trend in Africa. Also, strengthening institutions promises to reduce CO 2 emissions., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

A key goal of the Paris Agreement (PA) is to reach net-zero greenhouse gas (GHG) emissions by 2050 globally, which requires mitigation efforts from all countries. Africa's rapidly growing population and gross domestic product (GDP) make this continent important for GHG emission trends. In this paper, we study the emissions of carbon dioxide (CO 2), methane (CH 4) and nitrous oxide (N 2 O) in Africa over 3 decades (1990–2018). We compare bottom-up (BU) approaches, including United Nations Convention Framework on Climate Change (UNFCCC) national inventories, FAO, PRIMAP-hist, process-based ecosystem models for CO 2 fluxes in the land use, land use change and forestry (LULUCF) sector and global atmospheric inversions. For inversions, we applied different methods to separate anthropogenic CH 4 emissions. The BU inventories show that, over the decade 2010–2018, fewer than 10 countries represented more than 75 % of African fossil CO 2 emissions. With a mean of 1373 Mt CO 2 yr -1 , total African fossil CO 2 emissions over 2010–2018 represent only 4 % of global fossil emissions. However, these emissions grew by +34% from 1990–1999 to 2000–2009 and by +31% from 2000–2009 to 2010–2018, which represents more than a doubling in 30 years. This growth rate is more than 2 times faster than the global growth rate of fossil CO 2 emissions. The anthropogenic emissions of CH 4 grew by 5 % from 1990–1999 to 2000–2009 and by 14.8 % from 2000–2009 to 2010–2018. The N 2 O emissions grew by 19.5 % from 1990–1999 to 2000–2009 and by 20.8 % from 2000–2009 to 2010–2018. When using the mean of the estimates from UNFCCC reports (including the land use sector) with corrections from outliers, Africa was a mean source of greenhouse gases of 262221863239 Mt CO 2 eq. yr -1 from all BU estimates (the subscript and superscript indicate min–max range uncertainties) and of +263717615873 Mt CO 2 eq. yr -1 from top-down (TD) methods during their overlap period from 2001 to 2017. Although the mean values are consistent, the range of TD estimates is larger than the one of the BU estimates, indicating that sparse atmospheric observations and transport model errors do not allow us to use inversions to reduce the uncertainty in BU estimates. The main source of uncertainty comes from CO 2 fluxes in the LULUCF sector, for which the spread across inversions is larger than 50 %, especially in central Africa. Moreover, estimates from national UNFCCC communications differ widely depending on whether the large sinks in a few countries are corrected to more plausible values using more recent national sources following the methodology of Grassi et al. (2022). The medians of CH 4 emissions from inversions based on satellite retrievals and surface station networks are consistent with each other within 2 % at the continental scale. The inversion ensemble also provides consistent estimates of anthropogenic CH 4 emissions with BU inventories such as PRIMAP-hist. For N 2 O, inversions systematically show higher emissions than inventories, on average about 4.5 times more than PRIMAP-hist, either because natural N 2 O sources cannot be separated accurately from anthropogenic ones in inversions or because BU estimates ignore indirect emissions and underestimate emission factors. Future improvements can be expected thanks to a denser network of monitoring atmospheric concentrations. This study helps to introduce methods to enhance the scope of use of various published datasets and allows us to compute budgets thanks to recombinations of those data products. Our results allow us to understand uncertainty and trends in emissions and removals in a region of the world where few observations exist and where most inventories are based on default IPCC guideline values. The results can therefore serve as a support tool for the Global Stocktake (GST) of the Paris Agreement. The referenced datasets related to the figures are available at 10.5281/zenodo.7347077 (Mostefaoui et al., 2022). [ABSTRACT FROM AUTHOR]

Convergence of the environmental indicators has been one of the significant research areas for researchers since the study of Strazicich and List (2003) was published. Earlier papers have concentrated on investigating the existence of the convergence of indicators of the environment by using carbon emissions as a pollution indicator. However, some researchers have criticized the use of carbon emission as a one-dimensional indicator and proposed using ecological footprint as a more comprehensive indicator. The primary aim of this paper is to examine whether stochastic convergence of ecological footprint exists in 49 African countries from 1973 to 2018 by employing a battery of traditional stationarity methods and a newly proposed stationary method with smooth shifts and a combination of p-values. The empirical results show that panel findings of the conventional stationarity test with no structural shifts reveal that ecological footprint follows a stationary process. In contrast, panel findings of the traditional stationarity method with sharp and smooth changes and the newly developed stationary method with smooth shifts and a combination of p-values reveal that ecological footprint follows a non-stationary process. Moreover, the majority of individual results show that the ecological footprint follows a convergent pattern in 38 African countries, whereas it follows a divergent pattern in the remainder. Therefore, the main finding indicates the stochastic convergence of ecological footprint in African countries is validated. The policy outcomes of the empirical results are given in the body of the paper., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

This paper provides evidence on carbon dioxide (CO2) emissions for 51 African and 132 other countries in 163 sectors over the period 1995–2015. The resulting landscape is summarised in four patterns. Patterns identified for Africa differ from those identified for other regions but are closely related to a synthetic aggregate comparator based on key country characteristics. (1) All regions have reduced emission intensities over the period 1995–2015. Africa's share of global CO2 emissions has remained constant from 1995 to 2015. (2) The carbon intensity of production has increased in Africa in both decades. Over half of the 20 top African emitting countries shifted towards more carbon‐intensive techniques. (3) Over 1995–2015, intra‐regional shares of emissions fell by seven percentage points to 84% for Africa. Africa's share of emissions originating from Asia rose from 4% to 11%. Europe's share of emissions from Africa rose from 2% to 4%, respectively. (4) The export basket of Africa is skewed towards high CO2 equivalent‐intensity products. CO2 emission intensities correlate positively with output upstreamness (OU) and input downstreamness (ID). The OU/ID indicator of position in a supply chain is negatively correlated with CO2 emission intensities within regions. [ABSTRACT FROM AUTHOR]

Pyrolyzed semi‐coke (SC) is a by‐product of coal‐graded utilization, while the clean and efficient utilization of excess powdery pyrolyzed SC has given a huge challenge. The antibiotic filter residue (AFR) is a kind of biomass solid wastes, which also requires proper disposal or resource utilization. Utilizing the fuel complementary characteristics of pyrolyzed SC and AFR, oxy‐fuel gasification co‐processing can not only effectively realize the resource utilization of solid wastes but also achieve significant CO2 reduction boosting carbon neutrality. Here, the Aspen Plus software was used to simulate the staged oxy‐fuel co‐gasification characteristics of SC and AFR. The simulation results show that with the increase of the SC proportion in blends from 0% to 100%, the lower heating value is raised from 9.48 to 11.26 MJ·m−3, the gas yield is increased from 1.39 to 2.55 m3·kg−1, and the cold gas efficiency grows by 39.28%. The rise of oxygen volume percentage improves the lower heating value in the produced gas and volume fraction of H2, but the contents of CO and CO2, together with the gas yield and cold gas efficiency, show decreasing trends. Raising gasification temperature within a reasonable range is beneficial for enhancing the gasification performance and improving the syngas quality. The raised oxygen equivalent ratio increases the content of CO2 but leads to the decline of CO and H2. For sample AFR, as the oxygen equivalent ratio is varied from 0.6 to 0.8, the volume fraction of CO2 increases by 14.19%, while the contents of CO and H2 reduce by 5.34% and 8.77%, respectively. The present study offers effective support for the co‐disposal and resource utilization of powdery pyrolyzed SC and AFR. [ABSTRACT FROM AUTHOR]

The terrestrial carbon sink slows the accumulation of carbon dioxide (CO2) in the atmosphere by absorbing roughly 30% of anthropogenic CO2 emissions, but varies greatly from year to year. The resulting variations in the atmospheric CO2 growth rate (CGR) have been related to tropical temperature and water availability. The apparent sensitivity of CGR to tropical temperature ( γ CGR T ) has changed markedly over the past six decades, however, the drivers of the observation to date remains unidentified. Here, we use atmospheric observations, multiple global vegetation models and machine learning products to analyze the cause of the sensitivity change. We found that a threefold increase in γ CGR T emerged due to the long-term changes in the magnitude of CGR variability (i.e., indicated by one standard deviation of CGR; STDCGR), which increased 34.7% from 1960-1979 to 1985-2004 and subsequently decreased 14.4% in 1997-2016. We found a close relationship (r2 = 0.75, p < 0.01) between STDCGR and the tropical vegetated area (23°S – 23°N) affected by extreme droughts, which influenced 6-9% of the tropical vegetated surface. A 1% increase in the tropical area affected by extreme droughts led to about 0.14 Pg C yr−1 increase in STDCGR. The historical changes in STDCGR were dominated by extreme drought-affected areas in tropical Africa and Asia, and semi-arid ecosystems. The outsized influence of extreme droughts over a small fraction of vegetated surface amplified the interannual variability in CGR and explained the observed long-term dynamics of γ CGR T . The apparent temperature sensitivity of atmospheric CO2 growth rate has increased markedly over the past six decades, however, the increase remains unexplained. Here we show that tropical extreme droughts amplified the interannual variability in atmospheric CO2 growth rate and drove the sensitivity change. [ABSTRACT FROM AUTHOR]

We report on three years of continuous monitoring of carbon dioxide (CO2) and methane (CH4) emissions in two contrasting wetland areas of the Okavango Delta, Botswana: a perennial swamp and a seasonal floodplain. The hydrographic zones of the Okavango Delta possess distinct attributes (e.g. vegetation zonation, hydrology) which dictate their respective greenhouse gas (GHG) temporal emission patterns and magnitude. The perennial swamp was a net source of carbon (expressed in CO2-eq units), while the seasonal swamp was a sink in 2018. Despite differences in vegetation types and lifecycles, the net CO2 uptake was comparable at the two sites studied in 2018/2020 (-894.2±127.4 gm-2 yr-1 at the perennial swamp, average of the 2018 and 2020 budgets, and -1024.5±134.7 gm-2 yr-1 at the seasonal floodplain). The annual budgets of CH4 were however a factor of three larger at the permanent swamp in 2018 compared to the seasonal floodplain. Both ecosystems were sensitive to drought, which switched these sinks of atmospheric CO2 into sources in 2019. This phenomenon was particularly strong at the seasonal floodplain (net annual loss of CO2 of 1572.4±158.1 gm-2), due to a sharp decrease in gross primary productivity. Similarly, drought caused CH4 emissions at the seasonal floodplain to decrease by a factor of 4 in 2019 compared to the previous year, but emissions from the perennial swamp were unaffected. Our study demonstrates that complex and divergent processes can coexist within the same landscape, and that meteorological anomalies can significantly perturb the balance of the individual terms of the GHG budget. Seasonal floodplains are particularly sensitive to drought, which exacerbate carbon losses to the atmosphere, and it is crucial to improve our understanding of the role played by such wetlands in order to better forecast how their emissions might evolve in a changing climate. Studying such hydro-ecosystems, particularly in the data-poor tropics, and how natural stressors such as drought affect them, can also inform on the potential impacts of man-made perturbations (e.g. construction of hydro-electric dams) and how these might be mitigated. Given the contrasting effects of drought on the CO2 and CH4 flux terms, it is crucial to evaluate an ecosystem's complete carbon budget instead of treating these GHGs in isolation. [ABSTRACT FROM AUTHOR]

The Orbiting Carbon Observatory 2 (OCO-2) satellite has been providing information to estimate carbon dioxide (CO2) fluxes at global and regional scales since 2014 through the combination of CO2 retrievals with top–down atmospheric inversion methods. Column average CO2 dry-air mole fraction retrievals have been constantly improved. A bias correction has been applied in the OCO-2 version 9 retrievals compared to the previous OCO-2 version 7r improving data accuracy and coverage. We study an ensemble of 10 atmospheric inversions all characterized by different transport models, data assimilation algorithms, and prior fluxes using first OCO-2 v7 in 2015–2016 and then OCO-2 version 9 land observations for the longer period 2015–2018. Inversions assimilating in situ (IS) measurements have also been used to provide a baseline against which the satellite-driven results are compared. The time series at different scales (going from global to regional scales) of the models emissions are analyzed and compared to each experiment using either OCO-2 or IS data. We then evaluate the inversion ensemble based on the dataset from the Total Carbon Column Observing Network (TCCON), aircraft, and in situ observations, all independent from assimilated data. While we find a similar constraint of global total carbon emissions between the ensemble spread using IS and both OCO-2 retrievals, differences between the two retrieval versions appear over regional scales and particularly in tropical Africa. A difference in the carbon budget between v7 and v9 is found over this region, which seems to show the impact of corrections applied in retrievals. However, the lack of data in the tropics limits our conclusions, and the estimation of carbon emissions over tropical Africa require further analysis. [ABSTRACT FROM AUTHOR]

The Eastern Boundary Upwelling System off northwest Africa is among the most productive regions of the ocean. In 2019, two merchant ships equipped with an underway CO 2 system sampled the region following exactly the same track from 10°N to 36°N. We determine the sources and sinks of CO 2 and the seasonal cycle along the track. A weak permanent upwelling (WPU), a permanent upwelling (PU) and an open ocean regions are identified. The WPU (26°N to 33°N) is a source of CO 2 in summer and autumn, and a sink of CO 2 in winter and spring. Thermodynamic warming and cooling processes mainly drive the CO 2 variations in this region. The PU (20°N to 26°N) is a sink of CO 2 in spring and a source of CO 2 in other seasons. This region is the most productive and exhibits the largest variability of the CO 2 flux. The supply of CO 2 from subsurface waters dominate over the carbon uptake by biology, which leads to a strong outgassing, especially in winter and autumn. A sink of CO 2 occurs in spring only in the PU. Near Cape Blanc (20°N) in July 2019, a source of CO 2 is observed around 20°N within ± 1° of latitude and becomes a sink of CO 2 a few days later when the ship samples back the same area. South of 18°N, out of the influence of the coastal upwelling, the region is a sink of CO 2 in winter only and the region is mainly controlled by physical processes. Using voyages from 2010 to 2022, seawater f CO 2 significantly increases at a rate ranging from 1.82 μatm yr−1 to 2.10 μatm yr−1 close to the atmospheric increase. This is associated with a pH decrease between 0.0016 and 0.0022 yr−1. Nevertheless, there is no clear trend of the CO 2 flux in any region. • The NW African permanent upwelling (20-26°N) is a source of CO 2 except in spring. • The Weak Permanent Upwelling is a source of CO 2 in summer and autumn. • Surface pH has decreased at a rate of 0.002 unit yr−1 from 2010 to 2022. [ABSTRACT FROM AUTHOR]