GHG Mitigation Potentials in Annex I Countries. Comparison of Model Estimates for 2020

Robust quantification of the future potentials and costs for mitigating greenhouse gases in different countries could provide important information to the current negotiations on a post-2012 climate agreement. However, such information is not readily available from statistical sources, but requires the use of complex models that combine economic, technological and social aspects. In March 2009, the International Institute for Applied Systems Analysis (IIASA) invited leading modelling teams to a comparison of available model estimates of GHG mitigation potentials and costs in the Annex I countries for the year 2020. Eight modelling teams provided input to this comparison exercise. Although at face value estimates of mitigation potentials and costs show wide variation across models differences (i) in assumptions on the baseline economic development, (ii) in the definition of which mitigation measures are considered part of the baseline, and (iii) in the time window assumed for the implementation of mitigation measures explain much of the variation in model results. The paper presents a check-list of factors that need to be considered when interpreting model results. Once corrected for these key factors, two clusters of cost curves emerge for the year 2020: Models that include consumer demand changes and macro-economic feedbacks agree on a mitigation potential of up to 40% reduction below 2005 levels (that is approximately 45% below the 1990 level) for total Annex I emissions in 2020 for a carbon price of 50 to 150 US-$/tCO2. Bottom-up models that restrict their analysis to technical measures show only half of this potential. The model intercomparison demonstrates that future economic development has a strong impact on the eforts necessary to achieve given emission reduction levels. Any delay in the start of implementation of mitigation measures will reduce the mitigation potential that is achievable in the near term and inrease the costs. The introduction of measures that mobilize demand adjustments through structural or behavioural changes may increase the short-term mitigation potential significantly

Electrical detection of spin echoes for phosphorus donors in silicon

The electrical detection of spin echoes via echo tomography is used to observe decoherence processes associated with the electrical readout of the spin state of phosphorus donor electrons in silicon near a SiO$_2$ interface. Using the Carr-Purcell pulse sequence, an echo decay with a time constant of $1.7\pm0.2 \rm{\mu s}$ is observed, in good agreement with theoretical modeling of the interaction between donors and paramagnetic interface states. Electrical spin echo tomography thus can be used to study the spin dynamics in realistic spin qubit devices for quantum information processing.Comment: 14 pages, 3 figure