| 1. |
- Kulmala, M., et al.
(författare)
-
General overview: European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) - integrating aerosol research from nano to global scales
- 2011
-
Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:24, s. 13061-13143
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe and summarize the main achievements of the European Aerosol Cloud Climate and Air Quality Interactions project (EUCAARI). EUCAARI started on 1 January 2007 and ended on 31 December 2010 leaving a rich legacy including: (a) a comprehensive database with a year of observations of the physical, chemical and optical properties of aerosol particles over Europe, (b) comprehensive aerosol measurements in four developing countries, (c) a database of airborne measurements of aerosols and clouds over Europe during May 2008, (d) comprehensive modeling tools to study aerosol processes fron nano to global scale and their effects on climate and air quality. In addition a new Pan-European aerosol emissions inventory was developed and evaluated, a new cluster spectrometer was built and tested in the field and several new aerosol parameterizations and computations modules for chemical transport and global climate models were developed and evaluated. These achievements and related studies have substantially improved our understanding and reduced the uncertainties of aerosol radiative forcing and air quality-climate interactions. The EUCAARI results can be utilized in European and global environmental policy to assess the aerosol impacts and the corresponding abatement strategies.
|
|
| 2. |
- Pereira, Laura M., et al.
(författare)
-
From fAIrplay to climate wars : making climate change scenarios more dynamic, creative, and integrative
- 2021
-
Ingår i: Ecology & Society. - 1708-3087. ; 26:4
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding possible climate futures that include carbon dioxide removal (CDR) and solar radiation modification (SRM) requires thinking not just about staying within the remaining carbon budget, but also about politics and people. However, despite growing interest in CDR and SRM, scenarios focused on these potential responses to climate change tend to exclude feedbacks between social and climate systems (a criticism applicable to climate change scenarios more generally). We adapted the Manoa Mash Up method to generate scenarios for CDR and SRM that were more integrative, creative, and dynamic. The method was modified to identify important branching points in which different choices in how to respond to climate change (feedbacks between climate and social dynamics) lead to a plurality of climate futures. An interdisciplinary group of participants imagined distant futures in which SRM or CDR develop into a major social-environmental force. Groups received other seeds of change, such as Universal Basic Income or China's Belt and Road Initiative, and surprises, such as permafrost collapse that grew to influence the course of events to 2100. Groups developed narratives describing pathways to the future and identified bifurcation points to generate families of branching scenarios. Four climate-social dynamics were identified: motivation to mitigate, moral hazard, social unrest, and trust in institutions. These dynamics could orient toward better or worse outcomes with SRM and CDR deployment (and mitigation and adaptation responses more generally) but are typically excluded from existing climate change scenarios. The importance of these dynamics could be tested through the inclusion of social-environmental feedbacks into integrated assessment models (IAM) exploring climate futures. We offer a step-by-step guide to the modified Manoa Mash-up method to generate more integrative, creative, and dynamic scenarios; reflect on broader implications of using this method for generating more dynamic scenarios for climate change research and policy; and provide examples of using the scenarios in climate policy communication, including a choose-your-own adventure game called Survive the Century (https://survivethecentury.net/), which was played by over 15,000 people in the first 2 weeks of launching.
|
|
| 3. |
- Jaars, Kerneels, et al.
(författare)
-
Measurements of biogenic volatile organic compounds at a grazed savannah grassland agricultural landscape in South Africa
- 2016
-
Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 16:24, s. 15665-15688
-
Tidskriftsartikel (refereegranskat)abstract
- Biogenic volatile organic compounds (BVOCs) play an important role in the chemistry of the troposphere, especially in the formation of tropospheric ozone (O3) and secondary organic aerosols (SOA). Ecosystems produce and emit a large number of BVOCs. It is estimated on a global scale that approximately 90% of annual BVOC emissions are from terrestrial sources. In this study, measurements of BVOCs were conducted at the Welgegund measurement station (South Africa), which is considered to be a regionally representative background site situated in savannah grasslands. Very few BVOC measurements exist for savannah grasslands and results presented in this study are the most extensive for this type of landscape. Samples were collected twice a week for 2h during the daytime and 2h during the night-time through two long-term sampling campaigns from February 2011 to February 2012 and from December 2013 to February 2015, respectively. Individual BVOCs were identified and quantified using a thermal desorption instrument, which was connected to a gas chromatograph and a mass selective detector. The annual median concentrations of isoprene, 2-methyl-3-butene-2-ol (MBO), monoterpene and sesquiterpene (SQT) during the first campaign were 14, 7, 120 and 8pptv, respectively, and 14, 4, 83 and 4pptv, respectively, during the second campaign. The sum of the concentrations of the monoterpenes were at least an order of magnitude higher than the concentrations of other BVOC species during both sampling campaigns, with α-pinene being the most abundant species. The highest BVOC concentrations were observed during the wet season and elevated soil moisture was associated with increased BVOC concentrations. However, comparisons with measurements conducted at other landscapes in southern Africa and the rest of the world that have more woody vegetation indicated that BVOC concentrations were, in general, significantly lower for savannah grasslands. Furthermore, BVOC concentrations were an order of magnitude lower compared to total aromatic concentrations measured at Welgegund. An analysis of concentrations by wind direction indicated that isoprene concentrations were higher from the western sector that is considered to be a relatively clean regional background region with no large anthropogenic point sources, while wind direction did not indicate any significant differences in the concentrations of the other BVOC species. Statistical analysis indicated that soil moisture had the most significant impact on atmospheric levels of MBO, monoterpene and SQT concentrations, whereas temperature had the greatest influence on isoprene levels. The combined O3 formation potentials of all the BVOCs measured calculated with maximum incremental reactivity (MIR) coefficients during the first and second campaign were 1162 and 1022pptv, respectively. α-Pinene and limonene had the highest reaction rates with O3, whereas isoprene exhibited relatively small contributions to O3 depletion. Limonene, α-pinene and terpinolene had the largest contributions to the OH reactivity of BVOCs measured at Welgegund for all of the months during both sampling campaigns.
|
|
| 4. |
|
|
| 5. |
- Räsänen, Matti, et al.
(författare)
-
Carbon balance of a grazed savanna grassland ecosystem in South Africa
- 2017
-
Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 14:5, s. 1039-1054
-
Tidskriftsartikel (refereegranskat)abstract
- Tropical savannas and grasslands are estimated to contribute significantly to the total primary production of all terrestrial vegetation. Large parts of African savannas and grasslands are used for agriculture and cattle grazing, but the carbon flux data available from these areas are limited. This study explores carbon dioxide fluxes measured with the eddy covariance method for 3 years at a grazed savanna grassland in Welgegund, South Africa. The tree cover around the measurement site, grazed by cattle and sheep, was around 15 %. The night-time respiration was not significantly dependent on either soil moisture or soil temperature on a weekly temporal scale, whereas on an annual timescale higher respiration rates were observed when soil temperatures were higher. The carbon dioxide balances of the years 2010-2011, 2011-2012 and 2012-2013 were-85 ± 16, 67 ± 20 and 139 ± 13 gC m-2yr-1, respectively. The yearly variation was largely determined by the changes in the early wet season fluxes (September to November) and in the mid-growing season fluxes (December to January). Early rainfall enhanced the respiratory capacity of the ecosystem throughout the year, whereas during the mid-growing season high rainfall resulted in high carbon uptake.
|
|
| 6. |
- Räsänen, Matti, et al.
(författare)
-
The effect of rainfall amount and timing on annual transpiration in a grazed savanna grassland
- 2022
-
Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 26:22, s. 5773-5791
-
Tidskriftsartikel (refereegranskat)abstract
- The role of precipitation (P) variability with respect to evapotranspiration (ET) and its two components, transpiration (T) and evaporation (E), from savannas continues to draw significant research interest given its relevance to a number of ecohydrological applications. Our study reports on 6 years of measured ET and estimated T and E from a grazed savanna grassland at Welgegund, South Africa. Annual P varied significantly with respect to amount (508 to 672 mm yr-1), with dry years characterized by infrequent early-season rainfall. T was determined using annual water-use efficiency and gross primary production estimates derived from eddy-covariance measurements of latent heat flux and net ecosystem CO2 exchange rates. The computed annual T for the 4 wet years with frequent early wet-season rainfall was nearly constant, 326±19 mm yr-1 (T/ET=0.51), but was lower and more variable between the 2 dry years (255 and 154 mm yr-1, respectively). Annual T and T/ET were linearly related to the early wet-season storm frequency. The constancy of annual T during wet years is explained by the moderate water stress of C4 grasses as well as trees' ability to use water from deeper layers. During extreme drought, grasses respond to water availability with a dieback-regrowth pattern, reducing leaf area and transpiration and, thus, increasing the proportion of transpiration contributed by trees. The works suggest that the early-season P distribution explains the interannual variability in T, which should be considered when managing grazing and fodder production in these grasslands.
|
|
| 7. |
- Wabo, H., et al.
(författare)
-
Constraining the chronology of the mashishing dykes from the eastern kaapvaal craton in South Africa
- 2019
-
Ingår i: Springer Geology. - Singapore : Springer Singapore. - 2197-9545 .- 2197-9553. ; , s. 215-261
-
Bokkapitel (refereegranskat)abstract
- The present study focuses on NNE-trending dykes (sites LDA to LDJ) that occur near Mashishing in the eastern Kaapvaal craton. The Mashishing dykes were previously considered to be coeval and regarded as the extension of the 1.875–1.835Â Ga Black Hills dyke swarm into the sedimentary rocks of the Pretoria Group. Thin sections exhibit well-preserved igneous textures, with primary minerals (e.g., hornblende, clinopyroxene, plagioclase) extensively altered to secondary minerals in most cases. Our dykes can be petrographically grouped as pyroxenite (LDB and LDC), dolerite (LDH) and diorite (remainder of samples). REE and multi-element profiles of pyroxenites and two of the diorites (LDI and LDJ) suggest a common origin of the four dykes, but show no similarity with known mafic units of the Kaapvaal craton. An age estimate between 2208 and 2276Â Ma for dyke LDB, obtained from two overlapping amphibole 40Ar/39Ar plateau results, indicates that these four dykes predates the ~2.05Â Ga Bushveld event. The six remaining dykes have similar chemistry to either the ~2.06Â Ga Dullstroom Lavas (LDG), the 1.875–1.835Â Ga Black Hills dyke swarm (LDH) or the ~1.11Â Ga Umkondo dolerites (LDA, LDD, LDE and LDF). An U–Pb baddeleyite date of 1867 ± 10Â Ma for dyke LDH confirms it as a member of the Black Hills dyke swarm. Demagnetization of eighty-three specimens reveals five stable magnetizations carried by titanomagnetite. Two of these are regarded as magnetic overprints while three magnetizations are likely representative of primary remanences. The corresponding virtual geomagnetic poles (Lat.−26.84°N, Long. 31.66°E; Lat. 26.07°N, Long. 11.01°E, and Lat. 55.84°N, Long. 65.02°E) resemble those from the ~2.23Â Ga Hekpoort Formation, the ~1.88–1.83Â Ga post-Waterberg intrusions, and the ~1.11Â Ga Umkondo dolerites respectively. The above results suggest that the Mashishing dykes, despite similar trends, constitute swarms of different generations.
|
|
| 8. |
|
|
