The Dust Coma of Comet C/1999 S4 (Linear)

Comet C/1999 S4 (LINEAR) showed a very special behaviour between 28 June and1 July 2000. Optical observations of the dust coma in two distinct continuum bandsrevealed that it changed morphologically as well as in colour. The two-dimensionalcoma morphology indicates a splitting of the nucleus which probably occurred shortlybefore the observations of 28 June 2000. The distribution of the dust particles in sunand tail direction reflected by the slopes of the radial profiles indicate the presence ofa considerable amount of disintegrating dust particles in the sunward hemisphere andan overabundance of dust, reflecting at 440 nm, within the first 18,000 km of the dusttail. The spatial profiles of the (BC–RC) colour index in sun direction are distinctly different on 28 June and 1 July, indicating the production of a large amount of particles observable in blue continuum after 28 June.     

Joint Implementation in Ukraine: national benefits and implications for further climate pacts

The contribution that no-lose target schemes for non-Annex I (NAI) countries could make to achieve the 2°C target is explored by accounting for the incentives of 18 NAI countries’ participation in no-lose target schemes. Using various scenarios, it is shown that implementing uniform no-lose targets as part of the burden-sharing will not lead to global emissions levels compatible with the 2°C target, because uniform no-lose targets will only be beneficial to a few NAI countries. Employing more lenient uniform no-lose targets or individual no-lose targets for large emitters could increase participation by NAI countries and decrease global emissions, global compliance costs, rents by NAI countries, and compliance costs for Annex I (AI) countries. However, the resulting global emissions levels will not be compatible with attaining the 2°C target. Achieving this target will require more stringent emissions targets for AI countries and more lenient no-lose targets for NAI countries. As such, no-lose targets should account for 20% to 47% of global emissions reductions, while due to emissions trading around two-thirds of global emissions reductions should be realized in NAI countries. Indeed, an effective solution may only require no-lose targets for five to seven of the largest NAI countries.

Policy relevance

No-lose targets are one of a number of instruments discussed under the United Nations Framework Convention on Climate Change New Market Mechanism to integrate NAI countries in global emissions reduction efforts. In contrast to binding reduction targets, which apply penalties if a target is not met, no-lose targets provide incentives for meeting a target, e.g. in the form of excess emissions certificates that can be sold on the global carbon market. The presented simulations show that no-lose targets can result in contributions from NAI countries to global emissions reduction efforts. However, the simulations also show that the necessary incentives for no-lose targets need to be adjusted. AI countries require more ambitious targets and NAI countries require less ambitious no-lose targets than proposed by the Intergovernmental Panel on Climate Change report. Effective no-lose targets may only be required for five to seven of the largest NAI countries.     

Revisiting mobile bed tests for beach profile dynamics

The levels of uncertainty for morphodynamic analysis in the present state of art require field measurements and, whenever possible, large scale mobile bed tests to reproduce what happens in Nature under controlled conditions. Following this idea, the paper will revise the procedure to design reduced scale mobile bed tests, including the criteria for scaling and those for selecting an experimental facility.