Evaluation des mesures du Grenelle de l'Environnement sur le parc de logements - Rapport pour le Conseil Général du Développement Durable, ministère de l'Ecologie

La France s'est engagée à réduire les consommations d'énergie du parc des bâtiments existants de 38 % en 2020 par rapport à 2008, objectif " Grenelle -38 % ", et à diviser les émissions de CO2 par quatre en 2050 par rapport à 1990, objectif " Facteur 4 ". Pour atteindre ces objectifs, le Grenelle de l'environnement a mis en avant un certain nombre de leviers réglementaires et incitatifs. Cette étude, réalisée par le CIRED pour le compte du CGDD, a pour objectif d'analyser l'impact de ces différents instruments sur la consommation d'énergie pour le chauffage. Mesures existantes (crédit d'impôt développement durable, éco-prêt à taux zéro, réglementation thermique) et mesures supplémentaires (obligation de rénovation, contribution climat énergie) sont évaluées grâce au modèle Res-IRF du CIRED. Ce modèle prend en compte l'efficacité énergétique des logements et leur évolution dans le temps sous l'effet de rénovations ; il modélise également de façon originale les comportements de chauffage des ménages. Les premières simulations suggèrent que les politiques considérées ne suffisent pas à atteindre les objectifs ambitieux fixés par la France. Ces résultats sont sensibles aux hypothèses retenues. En introduisant des hypothèses plus optimistes (ex : prix des rénovations plus faible) et en prenant en compte des facteurs complémentaires au modèle (ex : bois), un travail de ré-estimation sur la base du modèle du CIRED a permis d'obtenir des résultats plus proches des objectifs du Grenelle

On compression of Bruhat-Tits buildings

We obtain an analog of the compression of angles theorem in symmetric spaces for Bruhat--Tits buildings of the type $A$. More precisely, consider a $p$-adic linear space $V$ and the set $Lat(V)$ of all lattices in $V$. The complex distance in $Lat(V)$ is a complete system of invariants of a pair of points of $Lat(V)$ under the action of the complete linear group. An element of a Nazarov semigroup is a lattice in the duplicated linear space $V\oplus V$. We investigate behavior of the complex distance under the action of the Nazarov semigroup on the set $Lat(V)$.Comment: 6 page

Enhancing global climate policy ambition towards a 1.5 °C stabilization: a short-term multi-model assessment

The Paris Agreement is a milestone in international climate policy as it establishes a global mitigation framework towards 2030 and sets the ground for a potential 1.5 °C climate stabilization. To provide useful insights for the 2018 UNFCCC Talanoa facilitative dialogue, we use eight state-of-the-art climate-energy-economy models to assess the effectiveness of the Intended Nationally Determined Contributions (INDCs) in meeting high probability 1.5 and 2 °C stabilization goals. We estimate that the implementation of conditional INDCs in 2030 leaves an emissions gap from least cost 2 °C and 1.5 °C pathways for year 2030 equal to 15.6 (9.0–20.3) and 24.6 (18.5–29.0) GtCO2eq respectively. The immediate transition to a more efficient and low-carbon energy system is key to achieving the Paris goals. The decarbonization of the power supply sector delivers half of total CO2 emission reductions in all scenarios, primarily through high penetration of renewables and energy efficiency improvements. In combination with an increased electrification of final energy demand, low-carbon power supply is the main short-term abatement option. We find that the global macroeconomic cost of mitigation efforts does not reduce the 2020–2030 annual GDP growth rates in any model more than 0.1 percentage points in the INDC or 0.3 and 0.5 in the 2 °C and 1.5 °C scenarios respectively even without accounting for potential co-benefits and avoided climate damages. Accordingly, the median GDP reductions across all models in 2030 are 0.4%, 1.2% and 3.3% of reference GDP for each respective scenario. Costs go up with increasing mitigation efforts but a fragmented action, as implied by the INDCs, results in higher costs per unit of abated emissions. On a regional level, the cost distribution is different across scenarios while fossil fuel exporters see the highest GDP reductions in all INDC, 2 °C and 1.5 °C scenarios

Evaluating process-based integrated assessment models of climate change mitigation

Process-based integrated assessment models (IAMs) project long-term transformation path- ways in energy and land-use systems under what-if assumptions. IAM evaluation is necessary to improve the models’ usefulness as scientific tools applicable in the complex and contested domain of climate change mitigation. We contribute the first comprehensive synthesis of process-based IAM evaluation research, drawing on a wide range of examples across six different evaluation methods including historical simulations, stylised facts, and model diag- nostics. For each evaluation method, we identify progress and milestones to date, and draw out lessons learnt as well as challenges remaining. We find that each evaluation method has distinctive strengths, as well as constraints on its application. We use these insights to propose a systematic evaluation framework combining multiple methods to establish the appropriate- ness, interpretability, credibility, and relevance of process-based IAMs as useful scientific tools for informing climate policy. We also set out a programme of evaluation research to be mainstreamed both within and outside the IAM community

IPCC, 2023: Climate Change 2023: Synthesis Report, Summary for Policymakers. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland.

This Synthesis Report (SYR) of the IPCC Sixth Assessment Report (AR6) summarises the state of knowledge of climate change, its widespread impacts and risks, and climate change mitigation and adaptation. It integrates the main findings of the Sixth Assessment Report (AR6) based on contributions from the three Working Groups1 , and the three Special Reports. The summary for Policymakers (SPM) is structured in three parts: SPM.A Current Status and Trends, SPM.B Future Climate Change, Risks, and Long-Term Responses, and SPM.C Responses in the Near Term.This report recognizes the interdependence of climate, ecosystems and biodiversity, and human societies; the value of diverse forms of knowledge; and the close linkages between climate change adaptation, mitigation, ecosystem health, human well-being and sustainable development, and reflects the increasing diversity of actors involved in climate action. Based on scientific understanding, key findings can be formulated as statements of fact or associated with an assessed level of confidence using the IPCC calibrated language