National Greenhouse Gas Inventories: Understanding Uncertainties versus Potential for Improving Reliability

We investigated the Austrian national greenhouse gas emission inventory to review the reliability and usability of such inventories. The overall uncertainty of the inventory (95% confidence interval) is just over 10% of total emissions, with nitrous oxide (N₂O) from soils clearly providing the largest impact. Trend uncertainty – the difference between 2 years – is only about five percentage points, as important sources like soil N₂O are not expected to show different behavior between the years and thus exhibit a high covariance. The result is very typical for industrialized countries – subjective decisions by individuals during uncertainty assessment are responsible for most of the discrepancies among countries. Thus, uncertainty assessment cannot help to evaluate whether emission targets have been met. Instead, a more rigid emission accounting system that allows little individual flexibility is proposed to provide harmonized evaluation uninfluenced by the respective targets. Such an accounting system may increase uncertainty in terms of greenhouse gas fluxes to the atmosphere. More importantly, however, it will decrease uncertainty in intercountry comparisons and thus allow for fair burden sharing. Setting of post-Kyoto emission targets will require the independent evaluation of achievements. This can partly be achieved by the validation of emission inventories and thorough uncertainty assessment.     

Carbon benefits from Amazonian forest reserves: leakage accounting and the value of time

Amazonian forest reserves have significant carbon benefits, but the methodology used for accounting for these benefits will be critical in determining whether the powerful economic force represented by mitigation efforts to slow global warming will be applied to creating these reserves. Opportunities for reserve creation are quickly being lost as new areas are opened to deforestation though highway construction and other developments. Leakage, or the effects that a reserve or other mitigation project provokes outside of the project boundaries, is critical to a proper accounting of net carbon benefits. Protected areas in the Amazon have particularly great potential mitigation benefits over an extended time horizon. Over a 100-year time frame, virtually no unprotected forest is likely to remain, meaning that potential leakages (both leakage to the vicinity of the reserves and that displaced by removing protected areas from the land-grabbing market) should not matter much because any short-term leakage would be “recovered” eventually. The effect of the value attributed to time greatly influences the impact of leakage on benefits credited to reserves. Simple assumptions regarding leakage scenarios illustrate the benefits of reserves and the critical areas where agreement is necessary to make this option a practical component of mitigation efforts. The stakes are too high to allow further delays in reaching agreement on these issues.     

Can the envisaged reductions of fossil fuel CO<Subscript>2</Subscript> emissions be detected by atmospheric observations?

The lower troposphere is an excellent receptacle, which integrates anthropogenic greenhouse gases emissions over large areas. Therefore, atmospheric concentration observations over populated regions would provide the ultimate proof if sustained emissions changes have occurred. The most important anthropogenic greenhouse gas, carbon dioxide (CO(2)), also shows large natural concentration variations, which need to be disentangled from anthropogenic signals to assess changes in associated emissions. This is in principle possible for the fossil fuel CO(2) component (FFCO(2)) by high-precision radiocarbon ((14)C) analyses because FFCO(2) is free of radiocarbon. Long-term observations of (14)CO(2) conducted at two sites in south-western Germany do not yet reveal any significant trends in the regional fossil fuel CO(2) component. We rather observe strong inter-annual variations, which are largely imprinted by changes of atmospheric transport as supported by dedicated transport model simulations of fossil fuel CO(2). In this paper, we show that, depending on the remoteness of the site, changes of about 7-26% in fossil fuel emissions in respective catchment areas could be detected with confidence by high-precision atmospheric (14)CO(2) measurements when comparing 5-year averages if these inter-annual variations were taken into account. This perspective constitutes the urgently needed tool for validation of fossil fuel CO(2) emissions changes in the framework of the Kyoto protocol and successive climate initiatives.     

Effects of manufactured nanomaterials on algae: Implications and applications

● Summary of positive and negative effects of MNMs on algae. ● MNMs adversely affect algal gene expression, metabolite, and growth. ● MNMs induce oxidative stress, mechanical damage and light-shielding effects on algae. ● MNMs can promote production of bioactive substances and environmental remediation. The wide application of manufactured nanomaterials (MNMs) has resulted in the inevitable release of MNMs into the aquatic environment along their life cycle. As the primary producer in aquatic ecosystems, algae play a critical role in maintaining the balance of ecosystems’ energy flow, material circulation and information transmission. Thus, thoroughly understanding the biological effects of MNMs on algae as well as the underlying mechanisms is of vital importance. We conducted a comprehensive review on both positive and negative effects of MNMs on algae and thoroughly discussed the underlying mechanisms. In general, exposure to MNMs may adversely affect algae’s gene expression, metabolites, photosynthesis, nitrogen fixation and growth rate. The major mechanisms of MNMs-induced inhibition are attributed to oxidative stress, mechanical damages, released metal ions and light-shielding effects. Meanwhile, the rational application of MNMs-algae interactions would promote valuable bioactive substances production as well as control biological and chemical pollutants. Our review could provide a better understanding of the biological effects of MNMs on algae and narrow the knowledge gaps on the underlying mechanisms. It would shed light on the investigation of environmental implications and applications of MNMs-algae interactions and meet the increasing demand for sustainable nanotechnology development.