The impact of the unilateral EU commitment on the stability of international climate agreements

In this paper we analyze the negotiation strategy of the European Union regarding the formation of an international climate agreement for the post-2012 era. We use game theoretical stability concepts to explore incentives for key players in the climate policy game to join future climate agreements. We compare a minus 20 percent unilateral commitment strategy by the EU with a unilateral minus 30 percent emission reduction strategy for all Annex-B countries. Using a numerical integrated assessment climate-economy simulation model, we find that carbon leakage effects are negligible. Ther EU strategy to reduce emissions by 30% (compared to 1990 levels) by 2020 if other Annex-B countries follow does not induce participation of the USA with a similar 30% reduction commitement. However, the model shows that an appropriate initial allocation of emission allowances may stabilize a larger and more ambitious climate coalition than the Kyoto Protocol in its first commitment period.Climate change, Coalition theory, Integrated assessment model, Kyoto protocol

Focus EMU, February 22, 2005

Une opinion rédigée et transmise à la Première ministre et aux Ministresprésidents régionaux par un collectif de signataires

Evaluation framework for sub-daily rainfall extremes simulated by regional climate models

peer reviewedSub-daily precipitation extremes are high-impact events that can result in flash floods, sewer system overload, or landslides. Several studies have reported an intensification of projected short-duration extreme rainfall in a warmer future climate. Traditionally, regional climate models (RCMs) are run at a coarse resolution using deep-convection parameterization for these extreme events. As computational resources are continuously ramping up, these models are run at convection-permitting resolution, thereby partly resolving the small-scale precipitation events explicitly. To date, a comprehensive evaluation of convection-permitting models is still missing. We propose an evaluation strategy for simulated sub-daily rainfall extremes that summarizes the overall RCM performance. More specifically, the following metrics are addressed: the seasonal/diurnal cycle, temperature and humidity dependency, temporal scaling and spatio-temporal clustering. The aim of this paper is: (i) to provide a statistical modeling framework for some of the metrics, based on extreme value analysis, (ii) to apply the evaluation metrics to a micro-ensemble of convection-permitting RCM simulations over Belgium, against high-frequency observations, and (iii) to investigate the added value of convection-permitting scales with respect to coarser 12-km resolution. We find that convection-permitting models improved precipitation extremes on shorter time scales (i.e, hourly or two-hourly), but not on 6h-24h time scales. Some metrics such as the diurnal cycle or the Clausius-Clapeyron rate are improved by convection-permitting models, whereas the seasonal cycle appears robust across spatial scales. On the other hand, the spatial dependence is poorly represented at both convection-permitting scales and coarser scales. Our framework provides perspectives for improving high-resolution atmospheric numerical modeling and datasets for hydrological applications

Evaluation of a high-resolution regional climate simulation over Greenland

A simulation of the 1991 summer has been performed over south Greenland with a coupled atmosphere–snow regional climate model (RCM) forced by the ECMWF re-analysis. The simulation is evaluated with in-situ coastal and ice-sheet atmospheric and glaciological observations. Modelled air temperature, specific humidity, wind speed and radiative fluxes are in good agreement with the available observations, although uncertainties in the radiative transfer scheme need further investigation to improve the model’s performance. In the sub-surface snow-ice model, surface albedo is calculated from the simulated snow grain shape and size, snow depth, meltwater accumulation, cloudiness and ice albedo. The use of snow metamorphism processes allows a realistic modelling of the temporal variations in the surface albedo during both melting periods and accumulation events. Concerning the surface albedo, the main finding is that an accurate albedo simulation during the melting season strongly depends on a proper initialization of the surface conditions which mainly result from winter accumulation processes. Furthermore, in a sensitivity experiment with a constant 0.8 albedo over the whole ice sheet, the average amount of melt decreased by more than 60%, which highlights the importance of a correctly simulated surface albedo. The use of this coupled atmosphere–snow RCM offers new perspectives in the study of the Greenland surface mass balance due to the represented feedback between the surface climate and the surface albedo, which is the most sensitive parameter in energy-balance-based ablation calculations.Peer reviewe

The Helminthosporium Foot-rot of Wheat, with Observations on the Morphology of Helminthosporium and on the Occurrence of Saltation in the Genus

is peer reviewedOpe

A numerical study of the response of the southern ocean and its sea ice to a CO2-induced atmospheric warming

Doctorat en sciences physiques - UCL, 198

A few, ou comment affaiblir un texte du GIEC

Genève, 16 heures, vendredi 16 février 2001. C’est en principe le dernier des quatre jours prévus pour la réunion plénière du groupe 2 du GIEC. Les délégués de cent pays sont ici pour « approuver » mot à mot le « résumé pour les décideurs » du groupe 2 (Impacts, vulnérabilité et adaptation aux changements climatiques). Les auteurs ont commencé à rédiger ce texte il y a un an, sur la base du corps du rapport en gestation. Dans le paragraphe qui traite des effets économiques agrégés des changements climatiques, ils ont notamment écrit (avec un niveau de confiance « moyen ») que beaucoup de pays développés connaîtraient des gains économiques nets pour une augmentation de la température globale allant jusqu’à environ 2 °C ; que les effets nets deviendraient panachés (mixed) ou neutres dans la gamme approximative de 2 à 3 °C, puis négatifs pour des augmentations plus importantes. On trouve aussi un peu plus bas (sans qualification) qu’il y aura « plus de personnes affectées par les changements climatiques que de personnes qui en tireront profit, même dans le cas d’une élévation inférieure à 2 °C de la température moyenne à la surface du globe »..