Future socioeconomic conditions may have a larger impact than climate change on nutrient loads to the Baltic Sea

The Baltic Sea is suffering from eutrophication caused by nutrient discharges from land to sea, and these loads might change in a changing climate. We show that the impact from climate change by mid-century is probably less than the direct impact of changing socioeconomic factors such as land use, agricultural practices, atmospheric deposition, and wastewater emissions. We compare results from dynamic modelling of nutrient loads to the Baltic Sea under projections of climate change and scenarios for shared socioeconomic pathways. Average nutrient loads are projected to increase by 8% and 14% for nitrogen and phosphorus, respectively, in response to climate change scenarios. In contrast, changes in the socioeconomic drivers can lead to a decrease of 13% and 6% or an increase of 11% and 9% in nitrogen and phosphorus loads, respectively, depending on the pathway. This indicates that policy decisions still play a major role in climate adaptation and in managing eutrophication in the Baltic Sea region.Peer reviewe

Shared socio-economic pathways extended for the Baltic Sea: exploring long-term environmental problems

Long-term scenario analyses can be powerful tools to explore plausible futures of human development under changing environmental, social, and economic conditions and to evaluate implications of different approaches to reduce pollution and resource overuse. Vulnerable ecosystems like the Baltic Sea in North-Eastern Europe tend to be under pressure from multiple, interacting anthropogenic drivers both related to the local scale (e.g. land use change) and the global scale (e.g. climate change). There is currently a lack of scenarios supporting policy-making that systematically explore how global and regional developments could concurrently impact the Baltic Sea region. Here, we present five narratives for future development in the Baltic Sea region, consistent with the global Shared Socioeconomic Pathways (SSPs) developed for climate research. We focus on agriculture, wastewater treatment, fisheries, shipping, and atmospheric deposition, which all represent major pressures on the Baltic Sea. While we find strong links between the global pathways and regional pressures, we also conclude that each pathway may very well be the host of different sectoral developments, which in turn may have different impacts on the ecosystem state. The extended SSP narratives for the Baltic Sea region are intended as a description of sectoral developments at regional scale that enable detailed scenario analysis and discussions across different sectors and disciplines, but within a common context. In addition, the extended SSPs can readily be combined with climate pathways for integrated scenario analysis of regional environmental problems.Peer reviewe

Quantized conductance in atom-sized wires between two metals

We present experimental and theoretical results for the conductance and mechanical properties of atom-sized wires between two metals. The experimental part is based on measurements with a scanning tunneling microscope (STM) where a point contact is created by indenting the tip into a gold surface. When the tip is retracted, a 10-20 Angstrom long nanowire is formed. Our measurements of the conductance of nanowires show clear signs of a quantization in units of 2e(2)/h. The scatter around the integer values increases considerably with the number of quanta, and typically it is not possible to observe more than up to four quanta in these experiments. A detailed discussion is given of the statistical methods used in the analysis of the experimental data. The theoretical part of the paper addresses some questions posed by the experiment: Why can conductance quantization be observed, what is the origin of the scatter in the experimental data, and what is the origin of the scaling of the scattering with the number of conductance quanta? The theoretical discussion is based on a free-electron-like model where scattering from the boundary of the nanowire is included. The configurations of the nanowires are deduced from molecular dynamics simulations, which also give information about the mechanical properties of the system. We show that such a model can account semiquantitatively for several of the observed effects. One of the main conclusions of the theoretical analysis is that,; due to the plastic deformation of the nanowires formed by the STM, the typical length scale of the variations in the shape of the boundary is not an atomic radius but rather bye times that value. This is the reason why scattering is sufficiently small to make conductance quantization observable by STM