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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]

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]

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]

This paper employs a recently constructed consumption-based carbon dioxide emissions data in which emissions computations are made based on fossil fuel usage domestically, in addition to emissions emanating from imports minus exports. We contrast this measure with the commonly measured territory-based carbon dioxide emissions data and examine how trade performance (split into imports, exports, and total trade) impacts these two measures of carbon dioxide. We focus on 22 sub-Saharan African countries over the period 1995–2014. Employing the system generalized method of moments, we find trade to generally have positive effect on emissions. The results are consistent across the different measures of trade and carbon dioxide emissions. The results of the paper allow us to give some policy suggestions regarding carbon dioxide emissions in sub-Saharan Africa. [ABSTRACT FROM AUTHOR]

We assess the role of riverine inputs of N, Si, Fe, organic and inorganic C in the tropical Atlantic Ocean using a global ocean biogeochemistry model. We use two sensitivity tests to investigate the role of the western (South American Rivers) and eastern (African Rivers) riverine nutrient inputs on the tropical Atlantic Ocean biogeochemistry (between 20° S-20° N and 70° W-20°). Increased nutrient availability from river inputs in this area (compared to an extreme scenario with no river nutrients) leads to an increase in 14% (0.7 PgCa-1) in open ocean primary production (PP), and 21% (0.2 PgCa-1) in coastal ocean PP. We estimate very modest increases in open and coastal ocean export production and sea-air CO2 fluxes. Results suggest that in the tropical Atlantic Ocean, the large riverine nutrient inputs on the western side have a larger impact on primary production and sea-air CO2 exchanges. On the other hand, African river inputs, although smaller than South American inputs, have larger impact on the coastal and open tropical Atlantic Ocean export production. This is probably due to a combination of nutrient trapping in upwelling areas off the Congo River outflow, and differences in delivered nutrient ratios leading to alleviation in limitation conditions mainly for diatoms. [ABSTRACT FROM AUTHOR]

This paper complements existing literature by assessing the conditional relationship between renewable energy and environmental quality in a sample of 40 African countries for the period 2002 to 2017. The empirical evidence is based on fixed effects regressions and quantile fixed effects regressions. The findings from both estimation techniques show that renewable energy consistently decreases carbon dioxide (CO2) emissions. Moreover, the negative effect is a decreasing function of CO2 emissions or the negative effect of renewable energy on CO2 emissions decreases with increasing levels of CO2 emissions. In other words, countries with higher levels of CO2 emissions consistently experience a less negative effect compared with their counterparts with lower levels of CO2 emissions. Policy implications are discussed. [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]

This paper investigates whether trade liberalization affects environmental quality (proxied by CO2 emissions) and, if so, whether the trade-induced emissions originate from differences in countries' economic growth, factor endowment or environmental regulations. We used panel data on 30 African countries and the Generalized Method of Moment estimation techniques. Though we found that trade openness is associated with elevated levels of CO2 emissions due to comparative advantage originating from factor endowment (i.e. composition effect), the overall effects of trade are seen to have some beneficial effects on environmental quality. Also, relative economic growth lowers emissions (scale effect) perhaps due to technology transfer. Furthermore, the differences in environmental regulations do not directly affect CO2 emissions while past levels of CO2 emissions significantly increase the current level due to the cumulative effect of CO2 emissions. To achieve a significant reduction in emissions, environmental regulations must be enforced in tandem with growth enhancing and production technology choice policies. [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]

Africa is one of the most data-scarce regions as satellite observation at the Equator is limited by cloud cover and there is a very limited number of ground-based measurements. As a result, the use of simulations from models is mandatory to fill this data gap. A comparison of satellite observation with model and available in situ observations will be useful to estimate the performance of satellites in the region. In this study, GOSAT column-averaged carbon dioxide dry-air mole fraction (XCO2) is compared with the NOAA CT2016 and six flask observations over Africa using 5 years of data covering the period from May 2009 to April 2014. Ditto for OCO-2 XCO2 against NOAA CT16NRT17 and eight flask observations over Africa using 2 years of data covering the period from January 2015 to December 2016. The analysis shows that the XCO2 from GOSAT is higher than XCO2 simulated by CT2016 by 0.28±1.05 ppm, whereas OCO-2 XCO2 is lower than CT16NRT17 by 0.34±0.9 ppm on the African land mass on average. The mean correlations of 0.83±1.12 and 0.60±1.41 and average root mean square deviation (RMSD) of 2.30±1.45 and 2.57±0.89 ppm are found between the model and the respective datasets from GOSAT and OCO-2, implying the existence of a reasonably good agreement between CT and the two satellites over Africa's land region. However, significant variations were observed in some regions. For example, OCO-2 XCO2 are lower than that of CT16NRT17 by up to 3 ppm over some regions in North Africa (e.g. Egypt, Libya, and Mali), whereas it exceeds CT16NRT17 XCO2 by 2 ppm over Equatorial Africa (10 ∘ S–10 ∘ N). This regional difference is also noted in the comparison of model simulations and satellite observations with flask observations over the continent. For example, CT shows a better sensitivity in capturing flask observations over sites located in North Africa. In contrast, satellite observations have better sensitivity in capturing flask observations in lower-altitude island sites. CT2016 shows a high spatial mean of seasonal mean RMSD of 1.91 ppm during DJF with respect to GOSAT, while CT16NRT17 shows 1.75 ppm during MAM with respect to OCO-2. On the other hand, low RMSDs of 1.00 and 1.07 ppm during SON in the model XCO2 with respect to GOSAT and OCO-2 are respectively determined, indicating better agreement during autumn. The model simulation and satellite observations exhibit similar seasonal cycles of XCO2 with a small discrepancy over Southern Africa (35–10 ∘ S) and during wet seasons over all regions. [ABSTRACT FROM AUTHOR]

Dissolved methane in Lake Kivu (East Africa) represents a precious energy deposit for the neighbouring countries, but the high gas loads have also been perceived as a threat by the local population. This is especially the case with respect to potential changes to the lake's stratification during planned industrial exploitation. Both of the above-mentioned issues require accurate and reliable measurements of dissolved gases and temporal changes to take responsible action. Previous data were unable to satisfactorily fulfil these requirements. Prior to our measurements, there was considerable disagreement about prognosticated new formation of methane. We show how measurement accuracy could be significantly improved by implementing equipment that is especially designed and modified for the complex gas conditions in Lake Kivu. Samples were taken from depths of 150 to 430 m to more reliably and more accurately determine the amount of dissolved methane and dissolved carbon dioxide. Beyond the provision of gas concentration profiles at the beginning of exploitation, this investigation can also potentially provide methods to survey the further evolution of gases over time. The use of gas-tight sampling bags produced highly reliable and accurate measurements. Our measurements confirmed the huge amount of stored methane, but clearly did not support the current belief of a significant recharge beyond diffusive loss. Direct measurements with a custom-made gas pressure sensor indicated no imminent danger due to limnic eruptions. However, a further survey of gas pressures is mandatory to detect changing conditions. Using sampling bags and a gas pressure sensor, we introduced reliable and highly accurate measurement approaches for the survey of the further development of gas concentrations. This equipment requires little effort with respect to calibration, which makes it suitable for use in the remote areas of Africa. [ABSTRACT FROM AUTHOR]

Since 1990 carbon dioxide emissions in Africa have increased by about 50%. The total carbon dioxide emissions of the entire African continent are not, however, anywhere near those of countries such as India or China. Yet certain African countries have per capita emissions comparable to some European countries. What is the outlook for Africa? How should African countries respond as it becomes increasingly likely that climate change is occurring? Increased industrial growth and more foreign investment in Africa, especially in countries that are politically and economically stable, have led to huge commercial developments such as the In Salah gas project in Algeria, which releases more than a million tons of carbon dioxide annually; and synthetic fuel plants and power stations in South Africa that generate more than 350 million tons per year. In this perspective should some African countries be required to limit greenhouse gas emissions or should they be immune to 'environmental taxation'? This paper critically reviews the carbon dioxide problem in some parts of Africa and its role in climate change. [ABSTRACT FROM AUTHOR]

Fuelwood plays an important role in the rural economy of the developing countries of Asia and Africa. Optimizing energy fixation in forest trees through high density energy plantations (HDEP), gasification of wood, and conversion of forest tree biomass, are some of the potential areas whereby additional research and development input for efficient management of atmospheric carbon in our energy system can be incorporated. For example, the photosynthetic efficiency of forest trees is rarely above 0.5%, which on the basis of theoretical considerations can be increased by up to 6.6%. Thus there is an ample scope to improve the efficiency up to 1%, which amounts to doubling of the productivity of the forests. Recent policy changes and experiences with wood-based bio-energy programmes in several countries indicate that woodfuels may become increasingly attractive as industrial energy sources. Use of biodiesel and the formulation of a project for undertaking 13.4 million ha of Jatropha plantations in India highlight the seriousness with which the Government of India is promoting carbon neutral energy plantations. The cost of establishment of plantations primarily for fuel production and its conversion to energy are major deterrents in this pursuit. Some of the issues in developing countries, like low productivity on marginal lands, degraded forest lands, and unorganized units for biomass energy conversion, result in cost escalation as compared to other energy sources. This paper revisits the scope for raising energy plantations, a comparison of the direct and indirect mitigation potential uses of plantations as an adaptation strategy through reforestation and afforestation projects for climate change mitigation and socio-economic issues to make this venture feasible in developing countries. [ABSTRACT FROM AUTHOR]

We examine the impact of trade and political institutions on environmental quality in Africa and explore whether political institutions matter to the trade-environment relationship. We use data from a large group of African countries, covering the period 1990-2008 and two indicators of environmental quality: net forest depletion and CO emissions. Results from GMM-SYS estimates suggest that political institutions influence the relationship between trade and environmental quality only in the case of CO emissions. Interestingly, we find that polity has a U relationship with net forest depletion. In addition, the results are in favor of an environmental Kuznets curve in the case of pollution but not in the case of net forest depletion. Finally, the results suggest that urbanization has a positive and linear impact on CO emissions, while it has a U-shaped relationship with deforestation. We discuss the policy implications of these findings. [ABSTRACT FROM AUTHOR]

Few field studies examine greenhouse gas (GHG) emissions from African agricultural systems, resulting in high uncertainty for national inventories. This lack of data is particularly noticeable in smallholder farms in sub-Saharan Africa, where low inputs are often correlated with low yields, often resulting in food insecurity as well. We provide the most comprehensive study in Africa to date, examining annual soil CO2, CH4 and N2O emissions from 59 smallholder plots across different vegetation types, field types and land classes in western Kenya. The study area consists of a lowland area (approximately 1200 ma.s.l.) rising approximately 600 m to a highland plateau. Cumulative annual fluxes ranged from 2.8 to 15.0 Mg CO2-C ha-1, -6.0 to 2.4 kg CH4-C ha-1 and -0.1 to 1.8 kg N2O-N ha-1. Management intensity of the plots did not result in differences in annual GHG fluxes measured (P = 0.46, 0.14 and 0.67 for CO2, CH4 and N2O respectively). The similar emissions were likely related to low fertilizer input rates (≤ 20 kg N ha-1). Grazing plots had the highest CO2 fluxes (P = 0.005), treed plots (plantations) were a larger CH4 sink than grazing plots (P = 0.05), while soil N2O emissions were similar across vegetation types (P = 0.59). This study is likely representative for low fertilizer input, smallholder systems across sub-Saharan Africa, providing critical data for estimating regional or continental GHG inventories. Low crop yields, likely due to low fertilization inputs, resulted in high (up to 67 g N2O-N kg-1 aboveground N uptake) yield-scaled emissions. Improvement of crop production through better water and nutrient management might therefore be an important tool in increasing food security in the region while reducing the climate footprint per unit of food produced. [ABSTRACT FROM AUTHOR]

Tropical forests in Africa store large amounts of carbon and there is an urgent need for accurate methods to estimate this important carbon stock. One method to achieve this is by allometric equations but in many forest ecosystems in Africa these have not been developed. This study combined biomass data of 896 trees from five tropical countries in Africa and eight different sources to develop mixed-species regression equations for estimation of total biomass and height in Dry, Moist and Wet forest types. For estimation of total biomass, allometric equations combining diameter, height and wood density provided the best estimators in the three forest types. Because adding wood density to diameter improved height estimation, we recommend using allometric equations that combine diameter and wood density for height estimations in mixed and diverse tropical forests. Comparing ecosystem-specific (Dry, Moist and Wet) allometric equations to general allometric equations developed with combined data, and also to pan-tropical equations, showed that ecosystem-specific equations provided better estimators. The results highlight the importance of considering wood density in tree allometry for biomass as well as for tree height estimations. Although general allometric equations can be useful, this study recommends when they are available, the use of existing site-specific or ecosystem-specific allometric equations which provide better estimates. [ABSTRACT FROM AUTHOR]

ABSTRACT Rising atmospheric CO2 concentrations affect climate directly through radiative effects and indirectly by changing plant water-use efficiency. Under global warming scenarios these widely reported changes will have a substantial impact on future bush encroachment, crop yields, river flow and climate feedbacks. Tree-ring intrinsic water-use efficiency (iWUE) records for Africa show a 24.6% increase over the 20th century. As high iWUE can partly counterbalance projected decreases in regional precipitation, this research has important implications for those involved in water resource management and highlights the need for climate models to take physiological forcing into account. [ABSTRACT FROM AUTHOR]

An understanding of the regional contributions and trends of anthropogenic carbon dioxide (CO2) emissions is critical to design mitigation strategies aimed at stabilizing atmospheric greenhouse gases. Here we report CO2 emissions from the combustion of fossil fuels and land use change in Africa for various time periods. Africa was responsible for an average of 500 TgC y-1 for the period 2000-2005. These emissions resulted from the combustion of fossil fuels (260 TgC y1-) and land use change (240 TgC y-1). Over this period, the African share of global emissions from land use change was 17%. For 2005, the last year reported in this study, African fossil fuel emissions were 285 TgC accounting for 3.7% of the global emissions. The 2000-2005 growth rate in African fossil fuel emissions was 3.2% y-1, very close to the global average. Fossil fuel emissions per capita in Africa are among the lowest in the world, at 0.32 tC y-1 compared to the global average of 1.2 tC y-1. The average amount of carbon (C) emitted as CO2 to produce 1US$ of Gross Domestic Product (GDP) in Africa in 2005 was 187 gC/$, close to the world average of 199 gC/$. With the fastest population growth in the world and rising per capita GDP, Africa is likely to increase its share of global emissions over the coming decades although emissions from Africa will remain low compared to other continents. [ABSTRACT FROM AUTHOR]

Highly productive papyrus ( Cyperus papyrus L.) wetlands dominate many permanently flooded areas of tropical East Africa; however, the cycling of carbon and water within these ecosystems is poorly understood. The objective of this study was to utilise Eddy Covariance (EC) techniques to measure the fluxes of carbon dioxide and water vapour between papyrus vegetation and the atmosphere in a wetland located near Jinja, Uganda on the Northern shore of Lake Victoria. Peak, midday rates of photosynthetic CO2 net assimilation were approximately 40 μmol CO2 m−2 s−1, while night time losses through respiration ranged between 10 and 20 μmol CO2 m−2 s−1. Numerical integration of the flux data suggests that papyrus wetlands have the potential to sequester approximately 0.48 kg C m−2 y−1. The average daily water vapour flux from the papyrus vegetation through canopy evapotranspiration was approximately 4.75 kg H2O m−2 d−1, which is approximately 25% higher than water loss through evaporation from open water. [ABSTRACT FROM AUTHOR]